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1982

Ecology and population status of the river otter in southwestern Montana

Hugh Zackheim The University of Montana

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Recommended Citation Zackheim, Hugh, "Ecology and population status of the river otter in southwestern Montana" (1982). Graduate Student Theses, Dissertations, & Professional Papers. 6994. https://scholarworks.umt.edu/etd/6994

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ECOLOGY AND POPULATION STATUS OF THE RIVER OTTER IN SOUTHWESTERN MONTANA

By

Hugh Zackheim

B. A ., Harvard University, 1974

Presented in partial fulfillment of the requirements for the degree of

M aster of Science

UNIVERSITY OF MONTANA

1982

Approved by;

S - f ' ( p > Chairman, Board of Examiners

Dean, Graduate S5î^ol

D ate

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Zackheim, Hugh S., M.S., Spring Quarter 1982 Wildlife Biology Ecology and Population Status of the River Otter in Southwestern Montana (100 pp.) D irector: B art W. O 'Gara

Field investigations were conducted on river otters (Lutra canadensis) in southwestern Montana from January 1980 through December 1981. Otter presence was detected by examining riverbanks for tracks and latrines, and relative otter populations were determined by scat density. Scat densities during the winter of 1980-81 were highest on the upper Jefferson and upper Madison rivers and lowest on the Ruby and upper Beaverhead rivers. Use by otters during spring and summer of 1981 was greatest on the Jefferson River near Whitehall and the Gallatin River near Three Forks; least use occurred on the Big Hole River near Melrose and the lower Madison River near Three Forks. Otters showed strong fidelity to established latrines. Latrine sites were generally in grassy openings on we 11-vegetated banks and averaged about 15 m^. Scat deposition at latrines peaked from late April through mid-May. Habitat characteristics that benefit otters include high flow volume, densely vegetated and undercut banks, and the presence of numerous sloughs and side channels that serve as brood-rearing habitat. Low flow volume and turbid water apparently reduced otter use on the Ruby and Beaverhead rivers; recent harvest may have reduced use of the lower Madison. Bank alteration through riprapping eliminates cover and denning areas and reduces otter use. Fish occurred in 99% of the 260 scats examined. Suckers (Catastomus spp. ) were the most important prey item, followed by whitefish (Prosopium williamsoni). Sculpins (Cottus bairdi) were an important sustaining food for otters, as were crayfish (Pacifasticus sp. ), except in winter. Otters took the most available prey, as determined by prey abundance and accessibility. Analysis of harvest distribution and the results of a statewide trapper questionnaire indicated densest otter populations in northwestern and southwestern Montana, ^pulations in these areas were seen as stable or increasing. Populations are sparse in west-central and central Montana and otters are generally absent from eastern Montana.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

I wish to thank the Montana Department of Fish, Wildlife and

Parks and the National Wildlife Federation for providing funding for

this project, I also wish to thank the members of my graduate

committee, Drs. Bart O'Gara, Joe Ball, Les Pengelly, and Mr.

Howard Hash, for advising me on study design and helping in thesis

preparation, along with Dr. John Weigand for reviewing thesis drafts.

Dr. Wayne Melquist assisted with the radio-telem etry work

and shared his expert knowledge and insight on river otter ecology.

The following persons also contributed in significant ways to

this study and I sincerely thank them: Karen Zackheim, Nick and

Anne Novich, Craig Hess, Janet Decker-Hess, Jerry Wells, Glen

Brackett, Tim Mosolf, Scott Waldie, Steve Moyles, Hank Fischer,

Robert Colman, Ken and Judy Siebel, Bruce and Elizabeth Potter,

and the many generous people of the Twin Bridges area.

Ill

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

P ag e

ABSTRACT ...... Ü

ACKNOWLEDGEMENTS ...... iii

LIST OF TABLES ...... v i

LIST OF FIGURES ...... v iii

INTRODUCTION ...... 1 O b j e c t i v e s...... 2 Historical Perspective...... 2

STUDY A R E A ...... 4

M ETHODS ...... 8 Population Cens u s in g ...... 8 Trapper Questionnaire ...... 11 H a b i t a t ...... 12 Food H ab its ...... 13

RESULTS ...... 14 Population Cens u s in g ...... 14 T ra p p e r Q u e s tio n n a ir e ...... 20 H a b i t a t ...... 27 Food H ab its ...... 34

DISCUSSION ...... 41 Population Cens u s in g ...... 41 Trapping P ressu re ...... 46 Harvest Im pacts...... 47 Harvest M onitoring ...... 49 H a b i t a t ...... 50 Factors influencing habitat selectio n ...... 51 Habitat selection in southwestern M o n tan a ...... 53

IV

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Latrine cover ...... 58 Food H ab its ...... 60 Factors influencing prey selection ...... 60 Prey selection in southwestern M ontana ...... 62 Seasonal prey variation ...... 64 Relative importance of prey ite m s ...... 65 Population Status ...... 66

RESEARCH RECOMMENDATIONS ...... 69

MANAGEMENT RECOMMENDATIONS ...... 71

REFERENCES CITED ...... 79

APPENDIX A. TRAPPER QUESTIONNAIRE ...... 84

APPENDIX B. SURVEY ON RELATIVE ABUNDANCE OF PREY SPECIES ...... 86

APPENDIX C. SUMMARY OF RELATIVE OTTER POPULATIONS, POPULATION TRENDS, AND RECENT HARVEST ON MONTANA RIVERS ...... 88

APPENDIX D. RADIO-TELEMETRY . 96

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T a b le P ag e

1. Densities of fall and winter otter scats along 6 major rivers in southwestern Montana, 1981 15

2. Otter census sections and scat indices along portions of 5 major rivers in southwestern Montana, March-July 1981 ...... 17

3. Relative otter population densities of 8 census sections, based on otter scats found from November 1980 to July 1981...... 19

4. Regional otter population trend estimates and questionnaire responses by Montana t r a p p e r s ...... 21

5. Type of sets used by trappers who have taken otters in M ontana ...... 24

6. Beaver and otter harvest and pelt price statistics, 1956-57 through 1980-81 trapping seaso n s ...... 2 9

7. Habitat characteristics of river census sections . . . 30

8. Scat deposition by h a b ita t ...... 33

9. Frequency of occurrence of prey items in 260 otter scats from 5 southwestern Montana riv ers ...... 35

10, Seasonal frequency of occurrence <%) of prey items in otter scats from southwestern M o n t a n a ...... 39

VI

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11. Relative importance of prey items by volume in individual sc a ts ...... 40

12. Relative densities of otter prey species in river sections where otter food habits were a n a l y z e d ...... 42

13. Relative benefits to otters of various habitat param eters, in relation to observed scat densities on 6 southwestern Montana rivers . . . 55

Vll

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Figure Page

1. Study a re a ...... 5

2. Census sections for latrine site su rv e y s ...... 9

3. Montana Department of Fish, Wildlife and Parks administrative regions and distribution of Montana otter harvest, 1977-78 through 1980-81 ...... 26

4. Otter and beaver harvest in Montana, 1956-57 through 1980-81 ...... 28

5. Frequency of occurrence by river of the 5 major prey items of otters in southwestern M o n t a n a ...... 37

V l l l

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION

The North American river otter (Lutra canadensis) has been

the subject of intense activity in both the biological and political arenas

during recent years. Some animal protection groups have called for

the complete protection of otters (Nilsson and Vaughan 1978), while

consumptive user groups and state wildlife management agencies have

generally contended that managed trapping does not harm otter popula­

tio n s .

In 1978, the U.S. Endangered Species Scientific Authority

(ESSA), acting in compliance with the Convention on International

Trade in Endangered Species, imposed state-by-state quotas on the

export of otter pelts (Hill 1978), Although these quotas remained in

effect for only 1 year, states have subsequently been required to

provide increased information to ESSA, including population size and

trend estimates, current management programs, projected harvest

levels, and distribution (Jachowski 1981). The result has been

increased research on river otters and the development of new

techniques for otter study (Melquist and Hornocker 1979a). However,

the details of otter population dynamics and habitat requirements are

still little known.

In Montana, biologists have collected information on otter

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. populations and distribution through trapper harvest records,

systematic observation reports, and food habit studies (Greer 1955a

and c). Because of the uncertainties about populations and harvest

impacts, additional biological information on which to base future

management of the otter is needed.

O b jec tiv e s

The purpose of this study was to:

1) determine the status and relative densities of otter popula­

tions on selected rivers in southwestern Montana;

2) identify characteristics of habitat used by otters in south­

western Montana;

3) compile and review data on otter harvest, sightings, and

historical records to gain an overview of otter populations statewide;

4) document otter food habits in southwestern Montana;

5) develop a survey technique that will allow researchers to

gain an indication of relative otter populations; and

6) assess the impacts of trapping harvest on otter populations.

Historical Perspective

During 1805-06, the Lewis and Clark expedition made the

first recorded observations of wildlife populations in what is now

Montana. Expedition journals contain more than a dozen references

to otters in the state (Coues 1893), beginning with an observation on

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the Missouri River near the present North Dakota border, Lewis

reported that otters were "numerous" and "in great plenty" above the

Great Falls of the Missouri where, he wrote, "the water has become

sufficiently clear for them to take fish. " The expedition reported

many otters through the upper M issouri drainage, including Lewis'

observation of "great quantity of beaver, otter and m usk-rats" in the

rivers near Twin Bridges (DeVoto 1953:181).

Development of the fur trade in the early 1800's put intense

pressure on aquatic furbearers. Chittenden (1935) reported that "the

great draft on the supply led to the rapid extermination of the beaver. "

Because otter pelts had a comparable value to beaver (Beidleman 1958,

Hash 1979), otters were sim ilarly exploited. In 1841, Pierre DeSmet,

a m issionary living along the Clark Fork River in western Montana,

remarked, "Like the beaver, [the otter] is incessantly pursued by the

hunters, and the number of both of these animals is yearly diminishing"

(Thwaites 1907).

While this historical record provides some insight into otter

distribution and early trapping impacts, the limited number of reports

and their circum stantial nature preclude generalizations about baseline

otter populations in Montana. In 1949, otter populations did not appear

sufficient to warrant an open season (Greer 1955b), and state wildlife

officials responded by closing the season. During this 7-year closure,

otter populations appeared to have increased (Newby 1957), so a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1-otter lim it was instituted in western Montana in 1956. According

to Newby, the limited open season on otters was "primarily aimed at

legalizing the sale of otters caught accidentally in beaver traps. " The

1-otter lim it for western Montana has remained in effect since that

tim e ,

STUDY AREA

The study was conducted along the upper M issouri River

drainage in southwestern Montana (Fig, 1). Research focused on the

Ruby, Beaverhead, Big Hole, and Jefferson rivers near Twin Bridges

and the Jefferson, Madison, and Gallatin rivers near Three Forks.

Valleys of these rivers are generally broad, flat plains,

bordered by dry benchland with grass and sagebrush cover. Mountain

ranges separate major drainages. Valley elevations range from 1,200

to 1,800 m, while the surrounding mountain peaks reach about 3,200 m.

Riparian vegetation consists largely of shrub thickets and

bottomland hardwood forests. The primary tree species is black

cottonwood (Populus trichocarpa), although quaking aspen (P.

trem uloides) and Rocky Mountain juniper (Juniperus scopulorum) are

occasionally present. Dominant shrubs in moist sites are various

willows (Salix spp. ), red osier dogwood (Cornus stolonifera), thinleaf

alder (Ainus tenuifolia), and water birch (Betula occidentalis). More

xeric sites are dominated by woods rose (Rosa woodsii). snowberry

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W hitehall hreemForks

Wisdom Twin B ridges

E n n is

D illo n

/ \ /

F ig . 1. Study Area

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (Symphoricarpus albus), buffaloberry (Shepherdia argentea), and

chokecherry (Prunus virginiana). Many grass species grow in the

riparian zone in southwestern Montana; Bugbee (1979) lists annual

beardgrass (Polypogon monspeliensis ), slough grass (Beckmannia

syzigachne). tall mannagrass (Glyceria elata). and fowl bluegrass

(Poa palustris) as some of the more important species.

The climate of the southwestern Montana river valleys is

characterized by warm, dry summers, occasional rainy periods in

spring and fall, and cold, dry winters. The average temperature in

Dillon (elevation 1,590 m) along the Beaverhead River ranges from

-6®C in January to 19®C in July, with daily temperature extremes

sometimes reaching -35®C during winter and 35*C during summer.

Average annual precipitation in Dillon is 29 cm.

Slush ice usually begins to flow in area rivers during

December, by which time ponds and backwater areas have frozen

over for the winter. Ice shelves form along the banks of main river

channels and, depending on the length and severity of the cold spell,

the entire river surface may freeze. With continued subfreezing

temperatures in January and February, the rivers may "gorge" with

large, irregular ice blocks forming in main channels. Periodic warm

southwest winds can cause some thawing throughout winter; by mid-

March most river sections are again ice-free.

Peak river flows usually occur between mid-May and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. mid-June, when warm tem peratures melt mountain snowpack and rains

swell tributaries. By late August, most rivers are at their lowest

flow volume, with agricultural withdrawals compounding the effects of

dry summer months. Annual flow variations can be considerable,

particularly on rivers without controlled flows. On the lower Big Hole

River, for example, late summer flows are often only 10-20% of the

annual average flow while spring runoff flows typically reach more

than 5 times this average.

The influence of land uses on riparian habitat in southwestern

Montana is relatively minor. Developments in the 6 largest towns

(Fig. 1) each affect only 1-2 km of river bank, and these impacts are

generally limited to bridges, riprap, and residences bordering the

river. The majority of riparian habitats are well-vegetated, although

light-to-moderate cattle grazing occurs in most areas.

Water quality on rivers in the study area reflects adjacent

land-use practices and substrate composition. The upper Madison and

Big Hole rivers, with cobble bottoms and few agricultural impacts,

are discolored only during spring runoff. The Jefferson, Gallatin, and

lower Madison rivers are generally clear from fall through early

spring, but spring runoff and agriculture-related erosion make them

cloudy periodically through the irrigation season. The Beaverhead

River carries high sediment loads because of heavy grazing pressure,

bank erosion, and irrigation return flows. Despite a clear and

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controlled flow from its source at Clark Canyon Dam, 82 km upstream,

the Beaverhead is generally turbid at its mouth near Twin Bridges.

METHODS

Population Cens using

Because the otter is a wide-ranging, secretive, and often

nocturnal animal, field efforts emphasized locating and quantifying

the amount of otter sign, especially scats (feces) on selected sections

of major rivers in the study area.

From November 1980 through February 1981, a total of

224 km along the banks of 6 rivers was examined for otter scats and

tracks by walking along the banks and searching 3 m inland from the

river's edge. Searches were conducted only when the ground was

snow-free. Survey sections were selected to include a wide range of

river habitats and geographic locations. The number and location of

scats less than 2 months old were recorded. Scat ages were estimated,

based on comparison with known-age scats exposed to ambient weather

conditions.

Eight sections on 5 rivers were selected for continued moni­

toring to obtain detailed information about relative abundance and

habitat use (Fig. 2). These sections provided wide geographic coverage

and representative samples of the various river habitats in the study

a r e a .

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Jefferson ^’

km

1, Big Hole River, Melrose to Glen 5» Jefferson River, Whitehall t. Big Hole River, Twin Bridges 6. Madison River, Upper 3, Beaverhead River, Twin Bridges 7. Madison River, Lower 4, Jefferson River, Twin Bridges 8o Gallatin River, Logan

Fig. 2. Census sections for latrine site surveys.

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For each census section, all areas of scat concentrations

(latrine sites) discovered during rlverbank surveys were re-examined

and evaluated for amount of sign, duration of use, spacing in relation

to other latrine sites, and susceptibility to flooding during high water.

From this evaluation, 1 latrine site for each kilometer of river was

selected for repeated survey. The combination of latrine sites chosen

for each census section was believed to have the most potential for

revealing otter presence and distribution throughout the census section.

A 100-m segment of bank was paced off and flagged at each

latrine site. These segments generally consisted of uniform habitat

and included 1 or. In a few cases, 2 or 3 regularly used latrine sites.

The number and location of new scats were recorded twice each month,

and scats were marked with a spot of fluorescent paint so they would

not be recounted on future visits.

An Index of otter abundance for each census section was

derived by dividing the total number of new scats by the number of

latrlne-slte days since the last survey. For example. If 28 scats were

deposited at 10 latrine sites over a period of 14 days, the Index would

be 28 divided by 140 (10x14), or 0.2, Indicating otters deposited an

average of 0.2 scats at each latrine site per day. For convenience, all

Index numbers were multiplied by 100; the Index for this example thus

becomes 20.

Scent-post surveys were conducted in July 1980 and November

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11

1981 to derive a census index for otters. Two scent posts per

kilometer were placed along 8- to 28-km sections of the Beaverhead,

Big Hole, and Jefferson rivers. Scent posts, consisting of a 10-cm

wooden dowel tipped with 2-3 drops of Laugemann's "Otter Gland" or

Hawbaker's "Otter Lure, " were placed on mud, snow or a prepared

surface of ash and chalk dust. Post sites were checked for 2 consecu­

tive days after placement.

An extensive program of aerial surveys was also planned to

count otter tracks on snow-covered riverbanks and ice shelves. How­

ever, the 1980-81 winter was unusually mild and dry, and only 1 aerial

survey was feasible. This flight was made in a Piper Super Cub on

3 February 1981.

Trapper Questionnaire

On 1 June 1981, 697 copies of a questionnaire (Appendix A) on

otter trapping and populations were mailed to trappers in Montana. The

questionnaire was designed to gain information on otter status, distri­

bution, and management considerations. Recipients included 217

persons who reported trapping an otter during the 4 years of the man­

datory pelt-tagging program, plus 480 trappers who had 5 or more

beaver pelts tagged during the 1980-81 season. All Montana Depart­

ment of Fish, Wildlife and Parks administrative regions were sampled.

Otter harvest distributions from the 1977-78 through 1980-81 trapping

seasons were also reviewed and mapped.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12

H ab itat

During reconnaissance for scats, height, slope, composition

of the lower bank, and vegetative cover on the upper bank were

recorded. The bank was also classified as undercut or intact. A bank

was considered undercut when the outer edge of the upper bank either

overhung, or was vertical to, the surface of the river and when that

bank configuration or associated vegetation provided cover adequate to

conceal an otter. Information was generally recorded for lOO-m

intervals, but lengths of undercut banks and stretches of dense riparian

vegetation were recorded to the nearest 20 m.

Data on physical and vegetative characteristics were recorded

for the 50 latrine sites that received the most use by otters.jduring the

spring scat census. Latrine dimensions, composition, and slope of

the lower bank, and height and vegetative cover of the upper bank were

recorded. Vertical cover was estimated for bare soil, grass, forbs,

shrubs, and trees, using the cover classes described by Pfister and

Arno (1980). Horizontal cover was classified as either sparse, medium,

or dense, when viewed at a 10-m distance from the center of the latrine

s ite .

Vertical and horizontal cover estimates were also made for

contiguous bank characterized by the same vegetative type as the

latrine site. For example, if a latrine site occupied 5 m of a 50-m

upland shrub bank, 2 sets of cover estimates would be recorded--1 for

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13

the latrine site and 1 representing a composite cover estimate for the

other 45 m of bank. The purpose of these latter estimates was to

determine if otters were selecting specific vegetative cover charac­

teristics for latrine site locations or whether latrine sites simply

m irrored the vegetative cover of the contiguous bank.

Food Habits

Food habits of otters were determined from analysis of 260

scats. The collection provided both seasonal and geographic repre­

sentation of otter food habits in the region. Scats were collected from

riverbanks and established latrine sites. Greer (1955a) described

otter scats and noted that they are easily recognized and distinguished

from scats of other species. The scats were collected in plastic bags

and, if necessary, air-dried for several days before being stored.

Only scats with a known month of origin were analyzed.

Dry scats were broken apart and examined under a binocular

microscope for content analysis. Prey remains were compared to

illustrations of fish scales (Lagler 1950, Casteel 1973) and to a

reference collection of scales and bones prepared from potential prey

species. Fish remains were keyed to family or genus, but could often

be classified to species based on Brown (1971), who described the

species occurring in the region.

Species composition was recorded for each scat. These

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results were tabulated as frequency of occurrence of individual prey

items in individual scats, as utilized in numerous studies of otter food

habits, including Greer (1955a and 1955c), Sheldon and Toll (1964),

Modafferi and Yocum (1980), and Melquist (1981). Each prey species

was classified as either a major or trace element of the scat because

prey volumes in combination with occurrence frequency give maximum

information on food habits (Jenkins and Harper 1980).

Two prim ary sources of information were employed to estimate

relative prey populations on southwestern Montana rivers--fisheries

progress reports (Montana Department of Fish, Wildlife and Parks

1981) and a questionnaire that was distributed to area fisheries biologists

(Appendix B), The fisheries reports provided population estimates and

incidental information derived from electro-shocking, while the ques­

tionnaire asked for estimates of relative populations of all prey species

on the study area rivers.

RESULTS

Population Cens using

Use by otters was recorded in almost all of the major river

sections surveyed. During the fall-winter surveys, heaviest otter use

occurred on sections of the upper Jefferson and upper Madison rivers

with sign densities reaching 11.6 and 12.0 scats per km (Table 1).

Least use occurred on the Ruby and upper Beaverhead rivers, where

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 5

Table 1. Densities of fall and winter otter scats along 6 major rivers in southwestern Montana, 1981.

Length of No. of scats bank examined (less than 2 Scats River and section (km) months old) per km

B eaverhead Mouth 3.5 36 10.2 Near Ruby River Junction 4.0 40 10.0 Giem's Bridge 8.0 1 0.1 Beaverhead Rock 11.0 0 0.0 D illon 4.0 0 0.0 Clark Canyon Area 5.0 0 0.0

B ig Hole Mouth to High Bridge 3.5 5 1.4 High Bridge to Pennington Bridge 9.0 89 9.9 Pennington to Reichle 26.0 28 1.1 Reichle to Glen 13.5 130 9.6 Glen to Brown's Bridge 16.0 65 4.1 Brown's Bridge to Melrose 16.0 167 10.4

G allatin Below Logan 6.0 63 10.5

J efferson Twin Bridges 18.5 215 11.6 Waterloo UPPER 5.5 48 8.7 W hitehall 7.0 90 11.6

Williams Bridge LOWER 9.0 33 3.7 Three Forks 8.0 32 4.0

M adison McAtee Bridge 2.0 17 8.5 Pallisades UPPER 6.0 72 12.0 W olf C reek 8.0 85 10.6

Three Forks LOWER 6,0 23 3.8 G reycliff 8.0 30 3.8

Ruby Sheridan 10.0 2 0.2 Twin Bridges 6.5 0 0.0 Ruby Dam 4.0 0 0.0

T otal 224.0 1271 5.7

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16

scat densities ranged from 0 to 0.2.

Although no method was available to correlate numbers of

scats with numbers of otters, patterns of relative abundance were

apparent. On the upper Jefferson, scat densities at Twin Bridges,

Waterloo and Whitehall were high, ranging from 8.7 to 11.6. On 2

lower Jefferson sections, scat densities varied from 3,7 to 4.0.

Similarly, 3 upper Madison sections varied from 8.5 to 12.0, while

2 lower Madison sections both had scat densities of 3.8. Two separate

sections of the Beaverhead River near Twin Bridges had scat densities

of 10.0 and 10.2. Four stretches of the Beaverhead River, from 16

to 75 km above Twin Bridges, and 3 stretches of the Ruby River,

from its mouth to its source at Ruby Dam 40 km upstream, showed

little use by otters.

Scat densities were not consistent on the Big Hole River,

varying from 1.4 at the lowest section to 9.9, 1.1, 9.6, 4.1, and 10.4

on an upstream progression from Twin Bridges to Melrose.

During the spring 1981 census of 8 river sections, the highest

mean scat index was 18.9 on the Jefferson River near Whitehall, while

the lowest index was 4.4 on the Big Hole near Melrose (Table 2).

Indices for individual survey periods ranged from 31.0 on the Jefferson

near Whitehall from 7 to 19 May to 1,1 on the Big Hole near Melrose

from 16 to 30 March.

Overall, 69 of the 92 selected latrine sites were used by

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■DCD O Q. C g Q. Table 2, Otter census sections and scat indices along portions of 5 major rivers in southwestern Montana, March-July 1981. ■D CD Section WC/) 3o' length No. of No. of New sc ats L a trin e - Scat 0 Section and location (km) la trin e s surveys located site days index 3 CD 8 Beaverhead above Twin Bridges 13.0 13 9 145 1,433 10.1

(O'3" Big Hole above Twin Bridges 9.7 9 7 83 855 9.7 1 3 CD Big Hole, Melrose to Glen 17.0 16 5 48 1,082 4.4 c" n 3. 3" CD Gallatin below Logan 9.8 10 4 68 513 13.3 ■DCD O Jefferson near Whitehall 13.2 14 5 189 1,002 18.9 Q.C a o 3 Jefferson near Twin Bridges 10.7 10 5 58 716 8.1 ■D O Madison above Three Forks 10.1 10 4 19 280 6.8 CD Q. Madison, Squaw Creek to Wolf Creek 11.2 10 7 68 910 7.5

■D CD T otal 94.8 92 46 678 6,791 10.0

C/i C/i 18

otters during the census period. Incidental observations of several of

these sites revealed use by otters throughout 18 months of field study.

The high water period extended from late May into the third

week of June, and 40% of all latrine sites were flooded by the unusually

high flows. After the water receded, some use was recorded at pre­

viously flooded sites, but other sites were permanently altered and no

use occurred. Additionally, by early July the growth of grass, forbs,

and shrubs obscured many latrine sites and scats deposited during the

2-week period between surveys were difficult to locate. As a result

of these factors, latrine site surveys were discontinued in mid-July.

On all 8 sections, maximum use of latrine sites was found on

surveys conducted between 2 and 28 May, reflecting use during the

previous 2-week periods. Minimum use occurred in late March and

early April. Levels of use varied substantially, and scat indices from

the period of maximum use averaged about 4 times greater than the

indices from periods of minimum use.

A composite assessm ent of otter sign from both the fall-

winter bank examinations and the spring latrine censuses forms the

basis for the relative population density rankings (Table 3). The

Jefferson River near Whitehall and the Gallatin River near Logan had

the most otter use and apparently the highest local otter populations.

The lower Beaverhead, lower Big Hole, upper Madison, and Jefferson

near Twin Bridges all ranked in the second category of relative otter

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ::o "OCD O Q. C g Q.

"O CD Table 3, Relative otter population densities of 8 census sections, based on otter scats found from WC/) November 1980 to July 1981. 3o' 0 3 Com posite Fall-Winter Spring CD relative density 8 River (section) ranking Scats per km Ranking Scat index Ranking (O'3" 1 Jefferson (Whitehall) 1st 11.6 1st 18.9 1st 3 CD Gallatin (Logan) 1st 10.5 4th 13.3 2nd c" n 3. 3" CD Beaverhead (Twin Bridges) 2nd 10.1 5th 10.1 3rd ■DCD O Q.C Big Hole (Twin Bridges) 2nd 9.9 6th 9.7 4th a o 3 ■D Jefferson (Twin Bridges) 2nd 11.6 1st 8.1 5 th O

CD Madison (Upper) 2nd 10.9 3rd 7.5 6th Q.

Big Hole (Melrose to Glen) 3rd 7.3 7th 4.4 8th ■D CD Madison (Lower) 3rd 3.8 8th 6.8 7th C/) C/)

CO 20

density. The Big Hole near Melrose and the lower Madison exhibited

the least use by otters during the survey periods.

Only 3 visitations occurred during 248 scent -post nights,

even though otters were present in all river sections during the survey

periods. Tracks revealed no specific movements by otters to these 3

posts; rather, otters had encountered the posts along their routes of

travel. At 7 other scent posts, fresh otter tracks were observed

from 2 to 25 m away but no visitation occurred.

On 3 February 1981, 1 day after a 1-4 cm snowfall, the

researcher flew over the lower 50 km of the Big Hole River, from

Melrose to Twin Bridges, From an altitude of 60 m, otter slides on

level ice were noted in 1 location. Ground examination of this site

revealed that 3 otters had been traveling together.

Trapper Questionnaire

Of the trappers contacted, 322 (46%) returned questionnaires

(Table 4). Trappers reported seeing the most otter sign along rivers

in northwestern and southwestern Montana. The Missouri River in

central Montana was also ranked high. Otter sign was generally

regarded as rare, although geographically widespread, in the west-

central and south-central parts of the state.

Survey respondents reported only 3 sightings of otters or

sign in eastern Montana during the last 5 years, including otters on

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■o I I

% Table 4. Regional otter population trend estimates and questionnaire responses by Montana trappers. (gC/) o ' 3 FWP administrative regions Statew ide to tals 8 c5' No. m ailed 87 86 217 185 56 42 24 697

3 CD No. (%) returned 46 (53) 39 (45) 109 (50) 84 (46) 29 (52) 12 (29) 3 (13) 322 (46) C p. No, (%) estimating a 3" CD population increase 10 (37) 4 (17) 28 (47) 3 (16) 45 (35) O ■o O cÛ. No. (%) estimating a a 59 (46) o stable population 12 (44) 13 (54) 25 (42) 9 (47) 3 ■o o No. (%) estimating a population decrease 5 (19) 7 (29) 6 (10) 7 (37) 25 (19) Û.CD

3O" a ■o CD % o 3

to 22

the Milk River near Dodson, the M issouri River in the C. M. Russell

National Wildlife Refuge, and the Little Powder River near Broad us.

Trappers' estimates from northwestern and southwestern

Montana generally indicated local otter populations were stable or

increasing; most trappers in west-central and central Montana saw

populations as stable or declining (Table 4).

Population and trend estimates were tabulated by drainage and

evaluated, based on the trapper's experience and written comments.

Through this assessm ent, plus information provided by FWP personnel

and my own field experience, a composite estimate was derived for

relative otter numbers and population trends on Montana rivers and

major tributaries (Appendix C).

Most trappers indicated that they either take precautions to

avoid trapping otters (24%) or make no specific sets for them (55%).

Conversely, only 21% of the trappers specifically attempt to trap

otters, including the 5% who reported making a "serious attempt"

to catch an otter annually.

Sixty-one percent of the trappers who have taken otters in

Montana indicated that all of their otters were caught in beaver sets.

Additionally, 19% responded that most of their otters were taken in

beaver sets. Only 20% indicated that most or all of their otters were

trapped in sets specifically intended for otters.

To derive comparative percentages for otters taken in beaver

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23

sets and those taken in otter sets, the number of otters represented by

each of the above response categories was tabulated (Table 5). This

analysis indicated that 75% (±9%) of the 416 otters reported taken in

Montana by survey respondents were trapped in beaver sets.

Twenty-nine percent of the trappers indicated accidental otter

trapping could not be avoided, 42% thought some of the otter take

could be reduced, and 2 9% indicated that most accidental otter take

could be eliminated by a careful trapper. Thirteen trappers volunteered

additional information and wrote that with the body-gripping traps like

the Conib ear 330, accidental catches of otters were difficult to avoid.

Several of these trappers stated that leg-hold traps could be set more

selectively for beavers and, if otters were caught, they could occa­

sionally be released. Some trappers noted that Conib ear traps are

very popular with less experienced trappers because they are easier

to use effectively. Sixty-seven percent of the trappers indicated that

making sets to avoid taking otters would reduce a trapper's beaver

harvest to a moderate or significant degree.

Sixty-four survey respondents commented on the 1-otter

annual limit; 75% believed this limit should be retained, 19% wanted

the season closed, and 6% said the limit should be raised to 2. The

most widely offered comments supporting the 1-otter limit were that

populations are too low to sustain more harvest and that accidental

catches are going to occur, so the trapper should be able to use the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■DCD O Q. C g Q.

■D CD Table 5. Type of sets used by trappers who have taken otters in Montana. C/) 3o" No. of Otters Otters trapped Otters trapped O Response category tra p p e rs trapped in beaver sets in otter sets

8 All otter trapped in beaver sets 78 166 166 0 ci'3" Most otter trapped in beaver sets 173 130 (±26)^ 43 (±26)^ i 25 3 CD Most otter trapped In otter sets 14 58 14 (±8)^ 44 (±8)® 3. 3" CD All otter trapped in otter sets 11 19 0 19 ■DCD O Q. T otal 128 416 310 (i 34) 106 (±34) aC O 3 ■D O Percentage of otters trapped in beaver sets: 310 (±34)/416 = 75% (Range: 66-83%)

CD Q. Percentage of otters trapped in otter sets: 106 (±34)/416 = 25% (Range: 17-34%)

■D CD 3 ^Numbers derived by assuming "most" categories represented 75% of harvest. Range C/) determined by using 60% and 90% estimates for "most. " o" 25

fur. A few trappers wrote that the season should remain open so every

trapper would have the opportunity to catch at least 1 otter in a lifetime,

indicating that otters are viewed as a trophy by some Montana trappers.

Seven trappers wanted réintroduction of otters in drainages where the

animals are now very rare or absent. Despite various opinions on the

proper limit, trappers consistently related their comments to their

assessm ent of otter populations, demonstrating a concern that otters

not be over-harvested.

The Three Forks area in southwestern Montana and the

Kalispell area in northwestern Montana have been the centers of con­

centrated otter harvest since the mandatory pelt-tagging and reporting

requirements were implemented in the 1977-78 trapping season (Fig. 3).

Each of these areas is at the confluence of several major rivers and

thus each is at a focal point of otter activity. Reported otter harvest

throughout Montana generally reflects the pattern of relative otter

densities. A notable exception, however, is the upper Yellowstone

drainage, where otter populations are reportedly high, but no harvest

has been documented. Considerable repeat harvest of otters by

individual trappers was evident in southwestern Montana during the

past 4 seasons; 17 trappers were responsible for 38 of the 112 otters

harvested in the region.

Since 1956, when the otter season was reopened after a 7-year

statewide closure, Montana's otter harvest has closely tracked the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 "OCD O Û. C g Q.

■D CD

C/î(£> d3

8

â'= r 3 CD C p. 3" CD ■OS I Ca o ■O3 O

û.CD

O C ■o CD • - 1 otter harvested (/) C/) ® - 5 otters harvested

Fig, 3» Montana Department of Fish, Wildlife and Parks administrative regions and d istrib u tio n of Montana o tte r harvest, 1977-78 through 1980-81. 27

beaver harvest (Fig. 4). The highest recorded otter harvest in Montana

was 88 animals in the 1979-80 trapping season. This represented a

103% increase over the previous season. The beaver harvest in

1979-80 was 28,627, also the highest in recent decades and a 126%

increase over the preceding year's harvest.

This harvest peak correlated with a sharp increase in beaver

prices (Table 6). Fur buyers paid a statewide average of $28.2 3 for

each beaver pelt and prime "blankets" sold for about $65. During the

1980-81 trapping season, beaver pelt prices dropped by 40% to a

$17.07 average and beaver and otter harvests decreased by 44% and

45%, respectively.

Although prices for otter pelts have fluctuated considerably

during the past 25 years, variations in otter harvest levels have not

correlated with variations in otter pelt prices.

From the 1975-76 trapping season through the 1979-80 season,

Montana experienced a 158% increase in the number of beaver trappers,

from 824 to 2,125. Trapper numbers have declined from this peak in

the subsequent 2 seasons (H. Hash, pers. comm. ).

H ab itat

An assessment of vegetative and river characteristics reveals

that major habitat differences exist among the 8 river census sections

(Table 7). The 2 Jefferson River sections, that have the largest flow

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Otter Harvest o o o o ON a o o O o VQ

oo I 8 ON

-pI » I ct5 I o § I o .3 g 1> î co I* g I I fO

asA-eag;

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 9

Table 6. Beaver and otter harvest and pelt price statistics, 1956-57 through 1980-81 trapping seasons.

Otter Beaver Beavers Average Average No. of trapped Trapping Reported pelt Estimated pelt beaver per otter season harvest price harvest price trappers trapped

1956-57 62 $17.71 10,000 $ 7.01 N/A 161

1957-58 63 19.15 19,700 7.55 N/A 313

1958-59 40 11.94 12,650 7,82 N/A 316

1959-60 44 13.24 18,732 10.84 629 42 6

1960-61 59 15.37 23.800 8.86 794 403

1961-62 45 10.00 16,000 8.21 707 356

1962 -63 51 16.69 22,000 10.26 635 431

1963-64 65 15.85 16,000 10.18 695 246

1964-65 32 22.17 7,800 9.63 501 244

1965-66 54 20.41 11,000 11.54 536 204

1966-67 42 17.66 12,200 10.23 407 291

1967-68 25 18.80 11,890 10,67 679 476

1968-69 25 24.17 12,405 13.52 652 496

1969-70 55 19.75 14,135 11.00 850 257

1970-71 32 18.89 8,345 9.2 9 556 261

1971-72 24 23.77 10,030 12.69 622 418

1972-73 34 32.19 15,612 15.95 861 459

1973-74 48 25.25 13,162 15.95 997 274

1974-75 42 20.67 12,080 11.66 766 288

1975-76 28 29.28 8,627 12.78 824 308

1976-77 48 42.36 18,756 17.18 1,371 391

1977-78 50 39.11 13,630 11.63 1,341 273

1978-79 39 55.19 14,101 15.78 1,212 362

1979-80 88 34.83 28,627 28.23 2,125 341

1980-81 48 34.48 16,111 17.07 N/A 336

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■DCD O Q. C g Q. Table 7. Habitat characteristics of river census sections.

1—H 3" Physical characteristics Vegetative characteristics "D CD 3 Side % % H a b ita t %® C/) F lo w C/) F lo w ”tù % % M e a n d e r ch annel unaQrcui o' River section 3 g ra d ie n t^ v o lu m e ^ p oo l r i f f l e ru n q u o tien t‘s ratio*^ banks v e g . 1 2 3 4 5 6 7 8 9 B e a v e rh e a d 2.0 16 1 1 98 1.6 1.3 22 21 9 30 36 10 1 2 10 1 1 3 CD 8 B ig H o le (Twin Bridges) 3.1 35 16 28 56 1.2 1,4 6 1 2 24 6 1 11 18 4 4 19 (O' 3 " B ig H o le Ï (M e lro s e ) 2 .4 35 16 41 44 1.2 1.0 6 4 3 22 16 1 12 26 8 3 8 CD G a lla tin 1.8 31 11 25 64 1.5 1.8 16 26 2 28 27 2 0 21 8 2 11

C 3 J e ffe rs o n 3 " CD (Twin Bridges) 1.7 51 18 19 63 1.3 1.4 10 18 8 16 33 5 3 11 19 0 16 CD T 3 J e ffe rs o n O Q. (Whitehall) 1.8 59 29 20 51 1.4 1.9 16 25 3 34 36 5 0 3 12 3 5 C a o Madison, Lower 3.2 45 D 90 10 1.2 1.9 5 28 1 16 53 9 4 1 5 1 10 3 T 3 O Madison, Upper 5.2 28 0 100 0 1.1 0.3 1 7 2 1 85 0 0 0 9 1 3 3 "

CD ^Elevational change in meters per kilometer of river. Q. Average annual flow in cubic meters per second.

‘^Ratio of actual length of river to straight line distance of flow, ■DCD ^Ratio of length of associated side channels and sloughs to length of main river channel.

C/) (/) ^Habitat classifications: 1—Marsh or riparian grasses 2—Early successional willow or cottonwood 3—Mixed moist shrub 4—Mixed upland shrub 5—Cottonwood forest with grass understory 6—Cottonwood forest with shrub understory 7—Cultivated pasture or hay meadow 8—Sagebrush grassland 9—Non-vegetated o 31

volumes, are characterized by a moderate flow gradient and a diverse

flow pattern, with many pools and riffles separating even-flowing runs.

About 1/6 of the banks on the Jefferson near Whitehall are undercut

and about 1/4 of the upper banks support dense vegetation, character­

istics that provide excellent cover for otters, both in the water and on

land. The Jefferson near Twin Bridges provides slightly less of this

cover, but both sections have many associated side channels and

spring-fed sloughs. Willows and other m oist-site shrubs dominate

the riparian community, with cottonwood forests also of importance

along the upper Jefferson.

The Gallatin River shares the dense vegetation and many

undercut banks which characterize the Jefferson, although cottonwood-

dominated banks are more frequent here. Its flow volume is about 1/2

that of the Jefferson and the flow gradient is somewhat steeper, result­

ing in more riffles. Sloughs and side channels parallel much of the

main channel.

The upper and lower Big Hole River sections are bordered

predominantly by open stands of cottonwood and willow with little dense

riparian vegetation, and only 6% of their banks are undercut. The

flow is relatively straight and rapid with many riffles. Flow volume

is sim ilar to the Gallatin, and lengths of associated side channels and

sloughs are equal to or greater than the main river channel.

The upper and lower Madison are both characterized by

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continuous riffles and shrub-dominated banks. The lower section has

more undercut banks, more dense vegetation, higher flow rates, and

more associated sloughs and side channels than the upper section.

The Beaverhead River has an even flow (98% classified as

"run") as it meanders through a shrub-dominated valley. Outside

banks are characterized by dense mesic shrub habitat, and the inside

bends are prim arily early successional willow with occasional m arsh

grass sections. Twenty-two percent of the banks are undercut, and

numerous sloughs enter the river.

Four of the 9 riparian habitats differentiated were preferred

by otters for scat deposition (Table 8). The moist shrub community,

dominated by willow, dogwood, alder, and birch, comprised only 24%

of total bank habitat but contained 44% of the scats. Banks dominated

by upland shrub species (primarily rose, snowberry, and buffaloberry),

cottonwood forest with shrub under story, and m arsh grass also held a

higher percentage of scats than the frequency of occurrence of those

habitats. Conversely, sparse sagebrush, hayfields, early successional

cottonwood-willow, and non-vegetated banks (usually sand, gravel, or

cobblestone) comprised 46% of the banks but contained only 15% of all

s c a ts .

Latrine sites were typically well vegetated but noticeably

more open than most of the contiguous bank. Matted grass covered

50-95% of the ground layer of the latrine while shrub coverage varied

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Table 8. Scat deposition by habitat.

% of total bank % of total scats ex am ined H ab itat (no, of scats) (bank length in km)

1-Marsh or riparian grasses 9 (181) 4 (9)

2-Early successional willow or cottonwood 13 (277) 22 (50)

3-Mixed moist shrub 44 (917) 24 (55)

4-Mixed upland shrub 8 (163) 4 (9)

5-Cottonwood forest with grass under story 4 (75) 5 (11)

6-Cottonwood forest with shrub understory 21 (446) 16 (36)

7-Cultivated pasture or haym eadow 1 (11) 8 (17)

8-Sagebrush grassland 0 (0) 3 (7)

9-Non-vegetated 1 (25) 13 (30)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34

widely from 5-95%. Adjacent non-latrine areas generally had grass

coverage below 50% and shrub coverage above 50%. Horizontal cover

was usually rated as sparse or moderate on latrine sites and moderate

or dense at adjacent areas. Grass or bare soil composed the lower

bank; haulouts, where otters climbed from the river onto the bank,

extended from the water surface at a 100%-to-vertical slope to a mean

height of 0,8 m. The scats were usually confined to an area extending

about 5 m along the riverbank and 3 m inland. A few latrines did not

conform to a rectangular shape; rather, these constituted a series of

haulouts and runways that lead to nearby channels and sloughs. Scats

were found on all portions of these runways which extended 25 m or

more in 1 direction.

Food Habits

Fish were the dominant item in otter diets in southwestern

Montana, occurring in 98.8% of the scats examined. Remains of

suckers (Catastomus catastomus and Ç. commersoni) occurred in

61% of the scats, followed by sculpins (Cottus bairdi) in 51%, whitefish

(Prosopium williamsoni) in 43%, and trout (Salmo gairdneri and S.

trutta) in 27% (Table 9). Other fish included longnose dace (Rhinichthys

cataractae) in 9% of the scats, carp (Cyprinus carpio) in 7%, and perch

(Perea flavescens) in 1%.

Of the invertebrates, crayfish (Pacifasticus spp, ) were the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 73 ■DCD O Q. C 8 Q. Table 9, Frequency of occurrence of prey items in 260 otter scats from 5 southwestern Montana ■D rivers. Numbers in parentheses are total occurrences. CD

(/)C/) R iv ers 3o' 0 P re y Item s G allatin M adison T otal 3 B eaverhead Big Hole Jefferso n CD 8 Sucker 81% (39) 60% (32) 76% (31) 83% (50) 12% (7) 61% (159)

(O' 3" Sculpin 56% (27) 40% (21) 61% (25) 43% (26) 59% (34) 51% (133) 1 3 CD W hitefish 27% (13) 45% (24) 41% (17) 38% (23) 62% (36) 43% (113) c" n 3. 3" CD C rayfish 40% (19) 15% (8) 49% (20) 50% (30) 0 (0) 30% (77) "OO O T rout 17% (8) 23% (12) 10% (4) 13% (8) 64% (37) 27% (69) Q.C a o 3 Stonefly nymph 4% (2) 34% (18) 0 (0) 2% (1) 26% (15) 14% (36) ■D O Longnose dace 19% (9) 2% (1) 17% (7) 12% (7) 0 (0) 9% (24) CD Q. C arp 10% (5) 2% (1) 5% (2) 17% (10) 0 (0) 7% (18) ■D CD Aquatic beetles 0 (0) 2% (1) 0 (0) 6% (4) 3% (2) 3% (7)

C/) C/Î Yellow p erch 0 (0) 0 (0) 0 (0) 3% (2) 0 (0) 1% (2)

M uskrat 0 (0) 2% (1) 0 (0) 0 (0) 0 (0) <1% (1)

03 36

most important diet item, occurring in 30% of the scats, Stonefly

nymphs (Plecoptera) occurred with a 14% frequency, and various

aquatic beetles (Coleoptera) were in 3%.

Muskrat (Ondatra zibithecus) composed the only mammal

remains, occurring in 1 scat from the Big Hole River.

Prey frequencies were consistent among the Beaverhead,

Gallatin, and Jefferson rivers (Fig. 5), On these 3 rivers, suckers

ranked first in frequency, sculpin and crayfish were either second or

third, and whitefish ranked fourth. In otter scats from the Big Hole

River, suckers were also the dominant item, followed by whitefish

and sculpins.

Otter food habits on the upper Madison River varied sharply

from the general pattern displayed by the other 4 rivers. Trout and

whitefish were the most important items in the otter diet, crayfish

were absent from scats, and suckers (which had a combined occur­

rence of 75% in scats from the other 4 rivers) occurred in only 12%

of the Madison River scats.

Other notable variations in otter food habits between rivers

were the importance of stonefly nymphs on the Big Hole (34% frequency),

the relatively low frequency of whitefish (2 7%) in Beaverhead scats,

and the importance of carp on the Jefferson (17%, compared with a

combined frequency of 3% for the other 4 rivers).

Both intra- and interspecific seasonal variations were evident

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■DCD O Q. C g Q.

■D CD P7\ Beaverhead (BV)

C/) n Big Hole (BG) 3o" 100% Gallatin (G) O (T^ Jefferson (j) 90 - im Madison (M) 8 a • « ci' 80 - *•*• • s ••• 0) 70 - •V X • #• i 64_ SO X ;• f 3 60 « X 3" X •* fn CD o o X * X CD o 171 ■D 50 X O X Q. •s ••• M •• • C X a %• / W) 40 s • «•. O 5 40 X .* X y • •• • 3 *•* V X ■D X . • • • s O •*. / X ••• s i* 30 - X X CD / X s ••• Q. X •. r 20 - X X J • • s *:* X • • & X 12 X ■;* 11 ■D 10 %• / s t a CD X « # X •• X • # / X « •* C/) X /• 0 C/) /X BV BG G J M BV BG G J M BV BG G J M BV BG G J M BV BG G J M Prey Item- Sucker Sculpin W hitefish Crayfish Trout Overall Frequency- 6l% 43% 27% Fig. 5. Frequency of occurrence, by river, of the 5 major prey items of otters in southwestern Montana. 38

in otter prey (Table 10). Crayfish demonstrated great seasonal fluc­

tuation, occurring in 17% of the scats during winter, 21% in spring,

50% in summer, and 36% in fall. Predation on trout reversed this

pattern, displaying a 47% frequency in winter and only 10-17% during

other seasons, Longnose dace also exhibited a peak in winter, with an

18% frequency, compared with only 4-7% during other seasons.

The 3 most important fish prey species occurred with con­

sistency in scats throughout the year. Suckers varied seasonally

between 55-65% frequency, sculpins between 40-58%, and whitefish

between 38-46%, These seasonal frequency fluctuations were tested

by X^, and none were significant.

Interspecific comparison of prey by seasons reveals that

suckers were eaten most frequently during all seasons except summer,

when sculpins occurred in 58% of scats and suckers in 55%. In winter

scats, stonefly nymphs (19%) and dace (18%) both reached their highest

frequencies.

Prey volumes in scats revealed that the larger fish (suckers,

whitefish, trout, carp) and crayfish usually composed major parts of

the scats in which they occurred (Table 11). Dace and stonefly nymphs

were generally trace components of the scats, while sculpins were

major components of almost half of the scats in which they occurred.

FWP biologists ranked whitefish as the most abundant of the

large fish prey species on 3 rivers, trout most abundant on the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7) "OCD O Q. C g Q. Table 10. Seasonal frequency of occurrence (%) of prey items in otter scats from southwestern Montana, ■D CD

C/) Spring Summer Fall Winter 3o" (Mar.-May) (June-Aug.) (Sept.-Nov.) (Dec.-Feb.) Total O Prey items n= 72 n= 60 n= 56 n = 72 n = 260

8 Sucker 65 55 59 64 61

ë ' 3" Sculpin 40 58 54 51 51 ï 3 CD Whitefish 46 45 46 38 43

3. 3" CD Crayfish 21 50 36 17 30 ■DCD O Trout 17 10 30 47 27 Q. g.C o 3 Stonefly nymph 10 15 11 19 14 ■D O Longnose dace 4 7 7 18 9 CD Q. Carp 10 3 3 10 7

■D CD Aquatic beetles 6 2 5 0 3 3 C/) o' Yellow perch 0 0 3 0 1

Muskrat 0 0 2 0 <1

CO CO 40

Table 11. Relative importance of prey items by volume in individual s c a ts .

% of scats (no. of scats) where prey item was: T o ta l no. P r e y ite m of scats Major T ra c e

S u ck er 159 68 (108) 32 (51)

Sculpin 133 44 (59) 56 (74)

W h itefish 113 73 (83) 27 (30)

C ra y fis h 77 78 (60) 22 (17)

T ro u t 69 75 (52) 25 (17)

Stonefly nymph 36 25 (9) 75 (27)

Longnose dace 24 17 (4) 83 (20)

C a rp 18 83 (15) 17 (3)

Aquatic beetles 7 0 (0) 100 (7)

Yellow perch 2 50 (1) 50 (1)

M u sk ra t 1 100 (1) 0 (0)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41

Madison, and suckers dominant on the Beaverhead (Table 12). Suckers

were uncommon on the Madison. Carp had a moderate abundance on

the Jefferson but were rare or absent on other area rivers. Crayfish

were considered common on the Beaverhead, Gallatin, and Jefferson,

but were uncommon on the Big Hole and absent from the Madison. Both

sculp ins and stonefly nymphs were ranked as abundant on the rapid,

gravel-bottomed Madison and Big Hole rivers.

DISCUSSION

Population Cens using

Cache counts, track counts, pellet-group transects, and other

field techniques have been used to estimate wildlife populations (Giles

1969). Through annual repetitions of these surveys, researchers can

derive indices of population abundance and trends upon which manage­

ment can be based. The following evaluation reviews a number of

techniques from this and other studies for cens using otter populations.

Several studies indicate a positive correlation between scat

densities and otter population levels. Humphrey (pers. comm, )

reported that scat counts may be a reliable otter census technique in

south Florida. Melquist (1981) determined that otters do not have

exclusive territories, and more than 1 family group often shares the

same general home range. These family groups spend most of their

time at any of several "activity centers" within their range, and scat

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(/) Table 12, Relative densities of otter prey species in river sections where otter food habits were analyzed. o' 3 Relative density^ a Comparative abundance CD Stonefly Longnose 8 River section Sucker Sculpin Whitefish Crayfish Trout nymph dace Carp Whitefish Sucker Trout 5 (S' Big Hole a (M elrose- i3 Twin Bridges) 4 5 5 2 4 5 4 1 1st 2nd 3rd CD C Madison (Upper) 2 5 5 0 5 5 2 0 2nd 3rd 1st p. Beaverhead CD 2nd ■o (Twin Bridges) ' 4 4 4 4 4 2 3 1 3rd 1st O Q.C o Gallatin (Logan) 3 4 5 3 4 3 4 1 1st 3rd 2nd

■D Jefferson O (Twin Bridges- 3 5 4 4 2 3 3 1st 2nd 3rd CD Whitehall) 5 Q. ^0 = absent, 1 = rare, 2 = uncommon, 3 = moderate, 4 = common, 5 = abundant. "O CD I (/)W o'

to 43

accumulations are common in these areas. When populations are high,

otters will occupy more activity centers and deposit more scats.

Moreover, because otters depend largely on olfactory communication

(Melquist 1981, Toweill and Tabor in press), the presence of several

groups of otters within a home range might stimulate scent-marking

behavior and result in an increased density of scats at a latrine site.

In a field study of the congeneric European river otter (Lutra lutra),

Jenkins and Burrows (1980) determined that scat densities generally

reflected otter numbers.

Changes in otter behavior, however, may alter the proportion

of scats deposited on riverbanks and thus reduce the value of scat

densities as population indicators (Jenkins and Burrows 1980). Melquist

and Hornocker (1979a) noted that individual otters may defecate often in

a short time period, and Melquist (pers. comm. ) reported that no scats

were found in the immediate vicinity of a natal den. Melquist (1981)

suggested that defecations and perhaps other forms of scent-marking

could serve to alert adult male otters to estrous females. The increase

in scats at southwestern Montana latrine sites during late April and

May might thus be attributable to breeding activity, rather than to an

increase in otter numbers.

The number of otter scats was used as an indicator of relative

otter populations during this study. In accord with the findings

reviewed above, the data were interpreted cautiously, without

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attempting to derive numbers of otters from the number of scats. Scat

density information, however, when combined with otter harvest data

and field reports from trappers, was valuable for assessing relative

otter populations on area rivers. Moreover, the consistency of scat

densities within geographic areas, as observed during the fall-winter

bank surveys, appears to validate the use of scat densities as measures

of relative otter abundance.

Although scent-post cens using showed potential for developing

an index of relative abundance for otters and mink (Mustela vison) in

south Florida (Humphrey and Zinn 1982), the lack of response by otters

during scent-post trials in this study area argues against further use of

this technique in Montana.

Winter aerial surveys to census otters and assess populations

trends have been used with some success in Minnesota and Wisconsin,

and methods are still being refined (Bill Berg, Minn. Dept. Nat. R es.,

pers. comm. ). The limited experience with aerial surveys for otter

tracks and slides in this study confirms that the technique is useful for

determining locations of otters during winter. Establishing a census

index for otter populations may be possible through repeated annual

flights over the study area rivers.

The effectiveness of aerial surveys for otters in southwestern

Montana is limited because of weather-related problems. Snowfall in

the river valleys tends to be light (less than 5 cm) and irregular in

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occurrence. Rapid temperature rises, caused by warm southwest

winds, often melt snow soon after it has fallen. During periods of

extreme cold, gorge ice forms in the rivers. This uneven surface

makes tracks difficult to see from the air and may discourage otters

from traveling on the ice.

Ideal tracking conditions occur when river edges freeze

gradually over a period of weeks and ice shelves extend several meters

from the bank toward the open water at the center of the river. With a

subsequent snowfall of as little as 1 cm, the tracks of otters on the

ice shelves can readily be seen from the air. Where feasible, ground

examination of aerial track sightings should be utilized to confirm

questionable tracks and determine numbers of animals.

An intensive program of live-trapping, instrumenting, and

monitoring otters can give a reliable population estimate (Melquist

1981); however, substantial time, money, and staff commitments are

necessary. Kruuk et al. (1980) injected radio-active Zn®^ into

European badgers (Meles m eles) and, through subsequent collection

and testing of scats for radio -activity, derived an accurate population

estimate. Scat collection in the badger study was facilitated by its

habit of using distinct latrines. Jenkins (1980) proved that injected

can reliably mark otter scats for more than 200 days.

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Trapping Pressure

Few Montana trappers set for otters, and most of the otters

harvested are taken accidentally in beaver sets. The consistent

relationship of total otter harvest to beaver harvest also confirms that

trapping pressure on otters is largely a function of efforts to catch

b e a v e r s .

The incidental harvest of otters in beaver sets is not unique

to Montana, Trappers in Wisconsin reported that 20% of their otter

harvest was taken accidentally in beaver sets, while Michigan biologists

believed that 50-60% of their 1954 otter harvest was accidental

(Knudsen 1956). More recently, Engel (1981) estimated that over 400

otters were trapped accidentally during Minnesota's 1980 spring beaver

season, while Kohn (pers. comm. ) reported that 36% of the 1979-80

otter harvest in Wisconsin was incidental to beaver trapping activity.

Hill (1978) mentions the relationship between beaver trapping

pressure and otter harvest, reporting that, in the southeastern states,

1 otter is harvested for every 6 to 10 beavers trapped. An experienced

trapper who responded to the Montana questionnaire estimated that he

caught 1 otter per 125-150 beaver traps set on the Jefferson River.

Beaver pelt prices are the major factor determining trapping

pressure on beavers and thus on otters. Hill (1978) commented that

during 2 years when southern beavers were bringing low prices, "a

reduced effort on the part of beaver trappers is believed to have

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reduced pressure on the river otter. " Recent Montana data, especially

during the 1978-81 trapping seasons, underscores how otter harvest

levels are responsive to beaver pelt prices.

Trapper attitudes also influence pressure on otters. Some

trappers set for otters only if they see fresh sign or if they believe

otter populations can sustain harvest. Thus, direct trapping pressure

on otters increases when populations are high and decreases when

numbers are low. Such density-dependent harvest pressure may help

dampen population fluctuations. However, because of local variations

in trapping effort, this self-regulation by trappers is a minor factor

compared to the overriding effect of beaver trapping pressure.

The distribution of otter harvest among individual trappers

can also have management implications. In southwestern Montana, 17

trappers took 38 otters during the past 4 seasons, demonstrating that

a few trappers can exert a significant harvest pressure on otters.

This high level of repeat harvest also implies that skilled trappers

setting for otters may be taking a large share of the harvest.

Harvest Impacts

Despite recent high harvest levels, especially during the

1979-80 season, trappers indicated that regional otter populations are

stable or increasing. Excessive localized harvest, however, may be

responsible for the low number of scats found on the lower Madison

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and the M elrose-Glen section of the Big Hole.

During the past 4 trapping seasons, 10 otters were taken

from the lower Madison study section, and another 12 were trapped

within the adjacent 20 kilometers. This section ranked last among 8

sections in scat density during fall surveys and 7th in scat index

during repeated spring surveys (Table 3). The upper Jefferson study

section, which had a sim ilar habitat rating to the lower Madison (Table

13), had a fall scat density 170% higher and a spring scat index 20%

higher than the lower Madison. Only 1 otter was harvested on the

upper Jefferson study section and 8 were taken within the adjacent

20 km of river during the past 4 seasons. Apparently, the high recent

harvest level on the lower Madison reduced otter numbers and led to

the relative scarcity of scats.

A sim ilar phenomenon is indicated for the Big Hole River. In

a 4-year period, no otters were taken from the Twin Bridges study

section, while 6 were taken from adjacent sections. During this

period, 3 otters were trapped in the Melrose-Glen study section and

6 were taken from adjacent sections. The Twin Bridges and Melrose-

Glen sections of the Big Hole have equal habitat ratings (Table 13); the

Twin Bridges section, which had lower harvest, had a 36% higher scat

density and a 122% higher scat index.

These examples suggest that trapping is reducing otter popula­

tions in local areas. More definitive information, however, is needed

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on carrying capacity, otter movements, and how trapping mortality

affects population size,

A number of factors make otter populations vulnerable to

over harvest and thus necessitate careful harvest regulation. Otters

travel extensively and a small number of knowledgeable trappers along

a waterway could reduce local populations (Toweill and Tabor in press).

Otters have a low reproductive rate; mean litter sizes are reported to

be 2,29 to 2.75 (Hamilton and Eadie 1964, Tabor and Wight 1977,

Mowbray et al. 1979) and otters generally do not bear young until age 3

(Toweill and Tabor in press). Melquist (1981) found a density of only

1 breeding female otter per 20 km of waterway in good habitat that

was closed to otter trapping, so removal of adult female otters could

affect populations over a wide area. Additionally, as demonstrated in

this study, otter harvest levels are in large part responsive to beaver

pelt prices. Thus, several years of high beaver pelt prices could

cause several years of heavy trapping pressure on otters, independent

of the otter population size.

Harvest Monitoring

Montana's mandatory pelt-tagging program has given FWP

a successful means of monitoring the level and distribution of the legal

otter harvest. Individual trappers and the statewide Montana Trappers

Association have endorsed the program, and compliance appears to be

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general in areas with an open otter season. Even trappers who appar­

ently exceeded the 1 -otter lim it reported this harvest, as evidenced

by the 11 instances in which a husband and wife each reported trapping

an otter. One case, in which 5 otters were reported trapped by mem­

bers of a single family, could be an intentional circumvention of the

1-otter limit; nevertheless, the harvest was reported.

Monitoring harvest in areas closed to otter trapping has

proven difficult. In Idaho, where the season on otters is closed,

Melquist (pers. comm. ) has indications of unreported harvest and

illegal trade in otter pelts. In Montana's Yellowstone River drainage,

where high otter populations are reported and a substantial amount of

beaver trapping occurs, no otter harvest has been reported. The

implication is that otters trapped on the Yellowstone are reported as

taken from other areas, are transported out of state, or are retained

by the trappers for personal use. Three otters trapped on the Shields

River, which is also closed to otter harvest, have been submitted to

FWP personnel by trappers.

H ab itat

River otters have demonstrated a remarkable adaptability to

a wide range of habitats. They occur in tundra of the north slope of

the Brooks Range (Magoun and Valkenburg 1977), the rivers of the arid

southwest (McClellan 1954), m arine habitats of the Pacific coast

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(Toweill and Tabor in press), swamps, tidewater, and estuaries of the

Atlantic and Gulf coasts (Mowbray et al. 1979, Humphrey and Zinn

1982), and the hardwood forest lake region of the northeast (Hamilton

1961). Almost all main river systems and large tributaries throughout

North America support or have supported otters (Toweill and Tabor in

p r e s s ) .

Factors influencing habitat selection. Only a few studies

have attempted to determine the factors affecting habitat selection by

otters within a limited geographical area. Melquist (1981) employed

radio -telem etry to determine otter habitat preferences in the North

Fork of the Payette River drainage in west-central Idaho. Instru­

mented otters showed a clear preference for valley habitats (97% of

fixes) over mountain lakes and stream s. Use of large valley streams

was predominant, although use of lakes, reservoirs, and ponds did

increase in winter. Melquist also noted that logjams were used pro­

portionately more than their occurrence and that the unobstructed,

open-water portions of stream s were used more often in winter when

other waters were frozen. He concluded that food availability had the

greatest influence on habitat use, but added that escape cover, shelter,

and freedom from disturbance were also important factors.

Melquist (1981) documented 1,283 otter den and resting sites,

reporting that beaver bank dens and lodges (38% of the total sites).

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logjams (18%), and riparian,yeget.ati_on.jtll%).were the most frequently

used. Other bank dens and natural underauLbanks constituted 8% of

the denning and resting sites; snow caves, talus rock, riprap, and

brush or log piles were used to a lesser extent.

Humphrey and Zinn (1982) assessed seasonal habitat use

in south Florida, They determined that otters retreated from marshes

as they dried out and moved to permanent ponds during the dry season.

In a study of the European otter in England and Wales,

MacDonald et al, (1978) compared the habitat characteristics of river

sections with and without "resident otter territories. " They found

that sections with consistent otter use had substantially more woodland

habitat and dense vegetative cover behind the banks and more cavities

beneath tree roots along the banks.

Several authors have distinguished otter brood-rearing habitat

from general otter habitat. Radio-tracking of otters by Melquist (1981)

indicated the importance of mudflats, marshes, and backwater sloughs

to family groups during summer, when the young were about 3-6 months

old. He noted that an abundant population of slow-moving prey species

inhabited these areas, Liers (1951) reported that a female otter moved

8-week-old pups from their natal den to a den near a shallow pond with

many crayfish.

Stephens (1957) commented that young European otters are

generally raised in small side stream s. Jenkins (1980) found a

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succession of 10 otter broods being reared in 2 tributary lakes over a

4-year span. He hypothesized that obtaining food was easier for young

otters at these shallow lakes than in the nearby main river, to which

the families moved after the young were 7-12 months old. Jenkins

also noted the importance of good cover in rearing areas.

Volume of flow also influences the suitability of river habitats

for otters. Melquist (1981) found only limited use of "feeder" streams

while Jenkins (1980) reported that European otters in Scotland used

small tributaries for brood-rearing and then returned to the main river

after the young were 7-12 months old. Stephens (1957) reported, but

did not document, that European otter populations in large rivers kept

nearby sm aller creeks stocked with otters, implying that the larger

rivers constituted the otter’s prim ary habitat.

Water quality is an important aspect of otter habitat that has

yet to receive adequate attention (Toweill and Tabor in press).

Mowbray et al. (1979) stated that otters were absent from waters

polluted by acid mine drainage in Maryland, Hill (1978) attributed the

decline of otter populations in the Great Plains, in part, to the adverse

impact of stream siltation on fish populations. Because otters hunt \

prim arily by sight (Erlinge 1968a), turbid water probably reduces

habitat quality for otters, even if prey populations are not affected.

Habitat selection in southwestern Montana. To assess habitat

selection by otters in southwestern Montana, river sections were

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ranked on the basis of the habitat characteristics (Table 13). Generally,

sections with the highest scat densities had the most beneficial habitat

characteristics for otters while sections with the lowest scat densities

had the fewest beneficial characteristics. The upper and lower Madison

sections were exceptions to this pattern.

Near Twin Bridges, where 4 different river habitats were

available to otters, the Beaverhead River more than 15 km above its

mouth and the Ruby River received little use. Turbidity and low

volume of flow are apparently the factors that discourage otter use of

these river sections. Bank erosion caused by overgrazing in the^^.'i^^

riparian zone, silt-laden return flows from irrigation, and irregular

flow releases from Clark Canyon and Ruby dams all contribute to the

high sediment loads in the Beaverhead and Ruby rivers. As a result,

visibility through the water is rarely as great as 1 m and often is less

than 0.3 m. Flow volume of these river sections is only 1/6 to 1/3 of

the volume of the major rivers in the study area.

Harvest statistics confirm that habitat selection rather than

trapping pressure is responsible for low otter numbers on the

Beaverhead and Ruby. During the past 4 years, only 1 otter has been

reported trapped on the Ruby and only 1 on the Beaverhead more than

15 km above its mouth. Experienced trappers working both rivers

during the past 30 years report that otters have been rare in these

river sections. Significantly, otters are also rarely reported on the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■O D Q. C g Q. Table 13. Relative benefits to otters of various habitat parameters, in relation to observed scat densities on 6 southwestern Montana rivers. "S" indicates the habitat parameter is

■ D CD most beneficial to otters; "O" indicates the habitat parameter is least beneficial to otters.

WC/) o' Brood- Seclusion Food 3 Relative otter River Flow W ater Denning rearing from human avail­ Mean 3 scat density (section) volume quality habitat habitat activity ability score CD 8 Jefferson 1st (Whitehall) 3 2 3 3 3 3 2.83 c3" i' (most scats) Gallatin i 3 (Logan) 2 2 3 3 3 3 2.67 CD Jefferson 3. 3" (Twin Bridges) 3 2 2 3 3 3 2.67 CD Beaverhead CD ■O D (Twin Bridges) 1 0 3 3 3 2 2.00 Q. 2nd C Big Hole a O (Twin Bridges) 2 3 1 2 2 2 2.00 3 ■D Madison O (Upper) 2 3 0 0 2 2 1.50

CD Q. Madison (Lower) 3 2 2 3 3 2 2.50 3rd Big Hole ■D CD (Melrose-Glen) 2 3 1 2 2 2 2.00

C/) C/) Beaverhead (above Giem's Br.) 0 0 3 3 3 1 1.67 4th Big Hole (fewest scats) (mouth-High Br. & Penn. Br.-Reichle) 2 3 0 0 2 2 1.50 Ruby (Lower) 0 0 3 2 3 1 1.50 56

Red Rock River and on the Big Hole River near Wisdom; both are

meandering, willow-lined rivers with low flow volumes and thus con­

stitute very sim ilar habitats to the Beaverhead and Ruby rivers.

Consistent otter use of the lower 15-km section of the Beaver­

head is apparently related to its proximity to the Big Hole and Jefferson

rivers, rather than to any significant habitat differences between this

section and the rest of the Beaverhead River. Perhaps, turbidity

decreases the availability of food periodically, and otters must use the

nearby larger and clearer rivers at those times.

The limited otter use of the Mouth-to-High-Bridge and the

Pennington-to-Reichle sections of the lower Big Hole River reveals

the adverse impacts of human alteration of banks on otter habitat. In

these sections, about 20-30% of the banks have been riprapped to pre- > ^

vent erosion. Because the riprap is designed to prevent the River from

eroding jts j)anks,_.±he outside edges of natural river bends are most

often altered. These outside edges, normally densely vegetated above,

with deep undercut banks below, are transformed by riprapping to rock

walls and no longer provide adequate denning or resting cover. The

unaltered inside river edges, generally bordering shallow water and

dominated by cobblestone with only sparse grass and willow cover,

also have little value for otters. The result is that long stretches of

riverbank are unsuitable and, despite clear water and the presence of

adequate, prey,—otter use is greatly j :*educed.. This finding parallels

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that of MacDonald et al. (1978), who found little use by European

otters In areas subjected to extensive removal of riparian vegetation.

Winter conditions also appear to influence patterns of otter

habitat use in southwestern Montana. Abundant otter sign during

1979-80 and 1980-81 indicated extensive late fall and winter use of the

upper 8 km of the M elrose-to-Glen section of the Big Hole River. The

River there is characterized by straight and fairly rapid flow, pro­

viding an open water channel throughout winter. Many nearby sections

of the Big Hole, particularly those with braided channels or slow pools,

become blocked by gorge ice during extended periods of subfreezing

weather. Melquist (1981) also found increased use of open-water

stream channels during winter. He attributed this finding to the limited

accessibility to water and food that iced-over stream segments provided

for otters.

The limited spring use and the absence of sign during the late

summer of 1980 indicated otter movement out of this section of the Big

Hole,,, Reasons for this movement are not evident, although it may be

related to seasonal conservation of food resources. Melquist (1981) ^

speculated that otter movements among widely spaced activity centers

allowed prey populations to recover between periods of heavy exploita­

tio n .

Consistent, moderate use of the upper Madison River indicates

that otters can adapt to various river habitats. Food accessibility is

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reduced in this section because suckers and crayfish, 2 easily caught

prey species, are either uncommon or absent. Also, the flow pattern

(all riffles and no pools) precludes prey concentrations and probably

makes hunting difficult. Undercut banks and dense riparian vegetation

are more limited here than on any other river in the study area. Over­

all, otter use of the upper Madison suggests that its abundant trout and

whitefish populations and clear water compensate for the limited

amount of denning habitat and the reduced accessibility of prey.

The lower Madison comprises a sim ilar habitat to the upper

River but has considerably more denning and brood -rearing areas. The

sm all amount of sign observed does not correlate with habitat factors

and is addressed in the discussion of harvest.

Latrine cover, Grinnell et al, (1937), Liers (1951), Melquist

and Hornocker (1979a), and Mowbray et al, (1979) described otter field

sign and catalogued the various types of sites used by otters for

depositing scats and other olfactory sign. These researchers generally

concluded that otters will use long-established sites ("haulouts, "

"landings, " and latrines) when coming onto the bank for feeding, loafing,

or defecating. Additionally, sites where otters leave scent and roll on

sand or grass were identified, although these sites may coincide with

latrines, Beaver lodges, prominent points of land, logjams, and

grassy banks were indicated as some of the most common areas used

b y o tte r s .

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Jenkins and Burrows (1980) systematically assessed the

relationship of vegetative cover to scat deposition in a study of the

European river otter along rivers and lakes in northern Scotland. They

found positive associations between scat density and good cover both on

the bank and 5 m behind the bank.

The data from southwestern Montana support the findings of

Jenkins and Burrows (1980) concerning the importance of cover in

selection of latrine sites. The moist shrub community, that received

the most use for latrines, often formed dense thickets, interspersed

with small grassy openings. Cover 5 m behind the bank was generally

thick, shielding the site from long-range observation. Vegetation on

the bank provided good lateral cover from observation points upstream

or downstream on the same bank.

Sim ilarly, cott onw ood - shrub and upland-shrub vegetative types,

which were selected for latrine sites, generally provided good screening

from inland locations. However, these habitats provided less lateral

cover because the vegetative strip immediately adjacent to the bank was

less dense than in the moist shrub habitats.

Otter use of the more open habitats was disproportionately less

than their frequency of occurrence. Marsh grass habitat was an excep­

tion to the scat density-cover relationship. Despite its open nature,

this habitat contained 9% of the scats but constituted only 4% of the

total bank length. Preferential use of m arsh grass habitat by otters

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may be related to their habit of rolling and defecating in grassy areas

(Melquist and Hornocker 1979a),

Food Habits

The dominant role of fish in otter diets has been documented

by numerous studies (Hamilton 1961 in New York, Knuds en and Hale

1968 in the Great Lakes, Toweill 1974 in Oregon). The 99% occurrence

of fish in otter scats from southwestern Montana rivers supports those . c ^

studies and, more specifically, correlates with the 2 existing Montana

studies. On the West Gallatin River, Greer (1955c) found fish remains^

in 99,9% of 1,142 scats; in the Thompson Lakes area of northwestern '

Montana, 93.2% of 1,374 scats contained fish remains (Greer 1955a),

In the only other otter food study in the northern Rocky Mountains,

Melquist (1981) found fish in 97% of scats from west-central Idaho.

Factors influencing prey selection. Many researchers have

speculated on the mechanics of prey selection by otters and have

attempted to relate the abundance of prey to the composition of the

otter’s diet, Greer (1955a) employed a combination of angling, gill-

netting, and electro-shocking to assess fish populations. For some

prey species, these results were in agreement with scat occurrence

frequencies; other species were greatly under-represented in sampling

compared with scats, notably sunfish (Lepomis gibbosus), or greatly

over-represented, notably squawfish (Ptychocheilus oregonensis) and

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whitefish. Greer speculated that the habits of their prey and the

foraging techniques of the otter made fish species differentially

vulnerable to predation. In the northwestern study, as well as in a |

, 's' ' subsequent study on the Gallatin River in southwestern Montana, Greer Ï I.

(1955a and c) concluded that availability of prey, as determined by both

abundance and vulnerability, was the determining factor in the diet of

the o tte r.

Sheldon and Toll (1964) further enumerated factors affecting

the availability of fish to otters, including the abundance, agility,

habitat, and spawning seasons of the fish; the effects of ice and water

tem perature stratification; and the feeding time and techniques of the

otters. Ryder (1955) stated that fish are probably captured by otter in

"inverse proportion to their swimming ability. " Erlinge (1968b), in

his feeding studies of captive European river otters, found that otters

selected larger, less maneuverable fish that were less able to find

cover. Toweill and Tabor (in press) concluded that otters do not select

for a particular prey species when hunting but abundant, slow-swimming

fish (including suckers) and sedentary, bottom-dwelling species

(including sculpins) are likely to be preyed upon at levels disproportion­

ately greater than their abundance. Trout, the authors added, would be

taken In lower proportion than their abundance because of their ability

' to swim rapidly, a hypothesis supported by Sheldon and Toll (1964) in a

study of a Massachusetts reservoir and by Erlinge (1969) for European

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otters in Swedish rivers.

Prey selection in southwestern Montana. A river-by-river

analysis of relative prey abundance (Table 12) and otter food habits

(Table 9) reveals that southwestern Montana otters select prey in a

manner sim ilar to that found in the studies reviewed above. Availability,

based on numbers and prey characteristics, determines the relative

frequencies of prey in the otter diet.

The slow-swimming suckers occurred most frequently in scats

from the Beaverhead, Big Hole, Jefferson, and Gallatin rivers. Their

relative abundance in those rivers ranged from moderately common to

abundant; however, on 3 of these sections biologists considered white-

fish populations to be greater than sucker populations. Otters were

apparently consuming suckers disproportionately to their abundance

because whitefish were more difficult to catch. On the upper Madison,

suckers occurred in only 12% of the scats, reflecting their low relative

ab u n d an ce.

Sculpins, a highly available prey based on both estimated

numbers and sedentary habits, exhibited a consistently high frequency

of occurrence in scats from all area rivers.

Whitefish, although ranked as the most abundant prey species

on 3 rivers, were only the third most frequent dietary item overall.

This is attributable to the good swimming ability of the whitefish. On

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the Madison, where suckers were uncommon, whitefish became an

important food source for otters, occurring in 62% of the scats.

Trout occurred in disproportionately fewer scats than their

relative abundance would suggest, Superior swimming ability and the

preference of trout for holding in areas with good cover probably com­

bined to reduce the availability of trout to otters. However, on the

upper Madison, where trout were the most abundant fish, undercut

banks were few, and suckers were uncommon, trout were the most

frequent prey item.

Studies from other regions of North America have indicated a

sim ilar importance of crayfish to that found in southwestern Montana.

Reported frequencies of occurrence from scat and digestive tract

analyses were 35% in New York (Hamilton 1961), 46% in Massachusetts

(Sheldon and Toll 1964), 2 5% in Oregon (Toweill 1974), 28% in

Wisconsin (Knudsen and Hale 1968), and 39% in North Carolina (Wilson

1954). Grenfell (1974), studying otter food habits in a central California

marsh, found crayfish remains in 98% of otter scats.

Predation on stonefly nymphs was significant only on the Big

Hole and Madison rivers where sizable populations of the salmon fly

(Pteronarcys californica) nymph exist. Greer (1955c) also found high

frequencies of stonefly nymphs (40%) in otter scats from the West

Gallatin, indicating otters will make heavy use of these large inverte­

brates where available.

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The presence of muskrat fur and bones in 1 scat correlates

with findings of Wilson (1954), Greer (1955a), Grenfell (1974), and

Melquist (1981), who indicate that otters will prey on small mammals,

but that such predation is opportunistic rather than part of a concerted

feeding strategy.

Seasonal prey variation. The winter trough and summer peak

in otter utilization of crayfish reflects the varying availability of this

prey species. Crayfish burrow in bottom sediments during winter and

are active on the river substrate in warmer seasons. Thus otters

would have to dig in the river bottom, a foraging technique described

by Liers (1951), to obtain crayfish in winter. In other seasons,

especially summer, active crayfish would be more easily encountered

by otters, either through direct observation or by otters moving under­

water rocks, a foraging technique discussed by Greer (1955c).

Predation on trout was greatest during winter, a finding

attributable to the reduced mobility of trout in water temperatures

near freezing. In contrast, whitefish are less affected by low water

tem peratures and exhibited no significant seasonal changes in otter

d ie ts .

Interspecific comparison of prey by seasons reveals that

suckers were the most frequent prey in all seasons, except summer

when sculpins occurred in 58% of the scats and suckers in only 55%.

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This increase in sculp in occurrence coincided with the increased

predation on crayfish, and may indicate otters forage on benthic

species more during summer.

During winter, longnose dace reached its highest frequency

in scats (18%), perhaps serving as an alternative food during the

reduced winter availability of crayfish.

Relative importance of prey item s. Knuds en and Hale (1968)

recorded both frequency of occurrence and prey volume in digestive

tracts to assess the importance of various foods to otters. Jenkins

and Harper (1980) used frequency of occurrence in scats together with

an estimation of the volume of prey items in the scat. In this study,

food items in each scat were subjectively ranked as either a major or

trace component of the scat. Volume measurements were not utilized

because several researchers (Lagier and Ostenson 1942, Wilson 1954,

Knuds en and Hale 1968) have pointed out that volumes of prey remains

may not accurately reflect actual prey volumes, due to varying digesti­

bility of prey items (especially crayfish shells). According to Knuds en

and Hale (1968:90), "in general, when occurrence and volume are both

high, the food is important; when occurrence is high and volume low,

the food is moderately important; when occurrence is low and volume

high, the food may not be important. " They also defined the high-

occurrence, low-volume foods as staple or sustaining foods.

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Regionwide application of these criteria to otter diet in

southwestern Montana suggests suckers are the most important food,

followed by whitefish. Crayfish are also very important, except in

winter, Sculpins constitute a sustaining food throughout the year.

Trout and carp are not very important because, despite high volumes

per occurrence, their frequency is low (with the exception of trout on

the upper Madison). All other foods could be considered relatively

unimportant based on the assessm ent of frequency and volume.

Population Status

Large amounts of sign, coupled with harvest data and reports

from trappers, indicate a good otter population along the Jefferson

River. Isolation from development, extensive undercut and densely

vegetated banks, large populations of rough fish and crayfish, and an

abundance of backwaters and sloughs for brood-rearing are the main

factors contributing to the excellent otter habitat on the Jefferson.

Dense vegetation and numerous spring sloughs limit human access to

the main river in many locations; however, trappers are making

increased use of boats to set beaver traps. Current harvest levels do

not seem to be adversely affecting the otter population on the Jefferson.

On the Gallatin River (Logan to Three Forks), consistently

large amounts of sign indicate a good population. Habitat is very

sim ilar to the Jefferson River, with ample denning and brood-rearing

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sites and diverse prey populations. Its proximity to the East and West

Gallatin, Madison, Jefferson, and Missouri rivers places the main

Gallatin near the center of perhaps the largest otter concentration in

southwestern Montana.

The upper Madison River shows consistent, moderate otter

use. Tributary mountain streams and lakes apparently connect popu­

lations from the upper Madison to those in the Red Rocks Lake National

Wildlife Refuge, where otters are rare but annually observed (Stroops

pers. comm. ). Trapping pressure is low on the upper Madison from

Quake Lake to Varney Bridge, but the scarcity of backwater sloughs

and slow-moving prey species may limit the value of this section for

brood-rearing. Harvest and reported observations indicate denser

populations in the Ennis area, where the Madison forms many channels

and where vegetative cover, and denning and brood-rearing habitat

increase significantly. Frequent observations of otters are made near

the Madison River delta on Ennis Lake and in Beartrap Canyon below

the Lake. From the Beartrap to the junction with the Jefferson, very

good otter populations have been reported, although recent high otter

harvest incidental to beaver trapping activities may have reduced otter

numbers on the lower Madison.

Evenly distributed otter sign and reported observations

indicate a moderate otter population on the Big Hole River from the

mouth to Wise River. Habitat alteration through riprapping has

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reduced otter use of some portions of the lower Big Hole, but the

majority of habitat is in good condition. Reports of otters are less

frequent above the confluence with the Wise River. Above Wisdom,

where the headwaters of the Big Hole consist of small meandering

meadow stream s, otters are only occasional visitors. Extremely

cold winter conditions and the subsequent shortage of open water may

discourage year-round use of the upper Big Hole. Below Wise River,

areas of open channels appear to attract the most winter use. The

generally open riparian vegetation gives trappers ready access to the

Big Hole and, because beaver (and thus otter) denning areas are both

obvious and somewhat limited in number, accidental trapping of otters

is a problem here. The middle and upper portions of the Big Hole are

isolated from other river systems, so high trapping pressure could

reduce local populations.

Consistent use by otters on the Beaverhead River is confined

to the lowest 15 km, where flow volume is greatest and other larger

river habitats are nearby. Use of the upper 70 km is scattered, but

otters have been observed throughout the length of the Beaverhead.

The generally excellent riparian habitat, freedom from human

encroachment, and very low reported harvest all indicate that direct

human influence is not responsible for the low otter density in the

upper Beaverhead. However, turbid water and low flow volume may

discourage otter use.

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RESEARCH RECOMMENDATIONS

Lack of reliable population Information is the foremost

obstacle to refining otter management in Montana. Tabulation of scats

can provide a measure of otter abundance, but further research is

needed on how such data should be interpreted.

1. The Department of Fish, Wildlife and Parks should

sponsor a study using Zn®^ to determine otter population density in

a limited study area representative of regional otter habitat.

Rationale; A program of live-trapping otters and injecting

them with radio-active tracer holds promise for estimating otter

populations and testing census-index techniques. As shown by

Northcott and Slade (1976) and Melquist and Hornocker (1979a), otters

can be live-trapped without great difficulty. Moreover, otters have

demonstrated strong fidelity to established latrines, and these sites

can readily be found along rivers in southwestern Montana. A large

sample of scats could be located to derive a population estimate.

Extrapolation of the population density determined by such a study

would provide an estimate of regional otter populations.

2. As part of a Zn®^ research project, scats from major

latrine sites should be counted regularly.

Rationale: The relationship between numbers of scats and the

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otter population's density determined through the Zn®^ results would

reveal whether scat counts are reliable indicators of otter abundance.

3. If scat numbers are shown to reflect otter abundance,

annual scat counts should be conducted. To initiate such a program,

researchers would select river sections, locate 1 major latrine per

kilometer of river, and count scats at these sites. Although this effort

would be time-consuming initially, latrines could be checked quickly

during float trips in subsequent years. Censuses would be conducted

at the same time each year.

Rationale: Annual scat counts would give abundance and trend

indices for otter populations. Biologists would thus have information

on which to judge the status of local otter populations. Conducting

censuses at the same time each year would eliminate impacts of

seasonal changes in otter use of latrine sites.

4. If cost or manpower limitations preclude FWP from

conducting any field monitoring program, or if scat numbers do not

prove to reflect otter populations, volunteer help from trappers should

be sought. Experienced trappers active along various western Montana

rivers should be requested to record data on trap-nights, otter sign

observed, and specific areas used by otters.

Rationale: Although the data would be subjective, relative

abundance and population trends would be established after several

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years. By using volunteer active trappers, many different geograph­

ical areas could be monitored at little financial cost to the Department.

5. The trapper questionnaire should be repeated at 5-year

in te rv a ls .

Rationale; Responses to the questionnaire will reveal otter

population trends and trapping pressure on a statewide basis.

MANAGEMENT RECOMMENDATIONS

Information generated during this study has been used to derive

specific management recommendations for the southwestern Montana

study area and to develop a general strategy for otter management

throughout the rest of the state. Careful monitoring of otter popula­

tions and trends is essential for the success of this management

strategy. The field research program, outlined under "Research

Recommendations, " Is the best way to generate reliable information.

If no annual field surveys are implemented, mail surveys to trappers

and interviews with local biologists should serve as the primary

sources of information.

Habitat carrying capacity also influences proper otter manage­

ment direction. In assessing habitat carrying capacity, wildlife man­

agers should consider food availability, water quality and quantity,

vegetative and physical characteristics, and the degree of seclusion

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from human activity. Recent history of otter populations in a drainage

can also provide an indication of carrying capacity. For example, if

a given drainage once supported more otters and habitat conditions

have remained unchanged, then the otter population in that drainage is

indicated as being below carrying capacity.

Because of the inherent uncertainties in the estimation of

otter populations, trends, and carrying capacity, and because of the

susceptibility of otters to over-harvest (see p. 49), the selection of

specific management direction for a given drainage should be conser­

vative. As more information is developed on otter habitat require­

ments and populations, a more precise otter management program

should become feasible in Montana.

For the southwestern Montana study area;

1. The Montana Fish and Game Commission should retain

the 1-otter seasonal limit at the present time.

Rationale; Good otter populations are indicated in most of

these waters, and the populations are reportedly remaining stable or

increasing under current levels of harvest. Low otter numbers in the

Beaverhead and Ruby rivers appear to be habitat-related, not harvest-

related, so more restrictive harvest regulations would probably not

increase populations in these drainages.

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2, If indicators reveal a decline in otter numbers in the

future, the Commission should institute a voluntary harvest-reduction

program, requesting that trappers avoid taking otters. Under this

program. Department of Fish, Wildlife and Parks personnel would

inform trappers that a reduction in otter harvest is necessary to allow

population recovery. The Department would also publish a brochure

on how trappers can recognize otter sign and take precautions to avoid

trapping otters. The 1 -otter seasonal limit would be retained to

accommodate incidental harvest.

Rationale; A decline in otter numbers (in the absence of

habitat change) indicates a population has dropped below the habitat

carrying capacity. Trapping harvest is one controllable aspect of

otter mortality and should be reduced to allow populations to recover.

Trappers responding to the survey expressed great interest in con­

serving otters; additionally, many trappers currently avoid trapping

otters, and most believe incidental trapping can be reduced. Given

these factors, a volunteer harvest-reduction program has a good

chance of success.

A number of factors argue against imposing more restrictive

regulations as a first step in reversing otter population declines in

southwestern Montana. First, most otter harvest is incidental to

beaver trapping, so a mandatory closure of the otter season would

only eliminate a small component of the otter harvest. Secondly, if

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the otter season were closed, incidental otter harvest might be

unreported or reported as being from another drainage, thus resulting

in the loss of harvest information or biasing harvest data from other

drainages. Finally, otter populations in the region appear high enough

to sustain a moderate decline without being jeopardized. While a

mandatory closure of both otter and beaver trapping would be the

fastest way to allow populations to recover, such a regulation would

end beaver trapping opportunities, would undermine trapper support

for otter management, and would be unnecessarily restrictive as a

first step to promoting otter population recovery.

If no population recovery is evident through the voluntary

harvest-reduction program and if continued incidental harvest is

indicated as being responsible for keeping otter numbers low, then

both beaver and otter trapping should be restricted or closed on a

drainage-specific basis. If continued intentional trapping of otters is

responsible for the lack of any population recovery, then the otter

season alone should be closed.

3. If the price of beaver pelts rises enough to stimulate a

significant increase in trapping effort, the Commission should institute

a voluntary harvest-reduction program for otters, as described in

No. 2 above.

Rationale; Currently beaver pelt prices largely determine

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trapping pressure and harvest of otters. The voluntary harvest-

reduction program would be a first step to prevent excessive otter

harvest when beaver pelt prices are high.

4. If otter pelt prices rise dramatically and stimulate an

Increase in direct trapping pressure on otters, the otter season should

b e c lo se d .

Rationale: Although regional otter populations can sustain

current Incidental harvest levels, the added pressure of intentional

harvest could have serious population consequences. Given a strong

economic Incentive for trapping otters, a mandatory closure of otter

trapping would probably be more effective in preventing excessive

harvest than would a voluntary harvest-reduction program.

For a general statewide otter management strategy:

1. In areas where good otter populations are Indicated, the

1-otter seasonal lim it should be retained.

Rationale: These populations have demonstrated the ability

to sustain current harvest levels. The 1-otter limit accommodates

incidental harvest and insures accurate harvest monitoring.

2. In areas where otter populations are declining In the

absence of habitat change, or are below carrying capacity, a voluntary

harvest-reduction program should be instituted.

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Rationale; See Management Recommendation No. 2 for the

southwestern Montana study area.

3, In areas where otter populations have traditionally been

very low, little harvest has occurred, and the otter habitat conditions

are poor, the otter season should be closed.

Rationale: Closure of the otter season would eliminate the

intentional component of trapping pressure and thus remove any

incentive for trappers in these areas to set for otters as a "trophy"

animal. On the other hand, imposing more restrictive regulations on

beaver trapping in addition to the otter trapping closure would not

cause a significant otter population response because this marginal

habitat is apparently not capable of supporting a larger otter population.

4. In areas where otter populations have suffered severe

recent population declines in the absence of habitat change, both the

otter and beaver seasons should be closed.

Rationale: Otter populations under these circumstances are

in immediate danger of becoming locally extinct; moreover, their past

higher relative abundance indicates that the habitat is capable of

supporting more otters. Closures of both the otter and beaver seasons

are necessary to eliminate both intentional and incidental harvest and

allow the population to recover.

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5. Otter management regulations should be modified if

beaver or otter pelt prices rise. These management modifications

and the rationales are presented under Management Recommendations

No, 3 and No. 4 for the southwestern Montana study area.

6. The Department should investigate the feasibility of re ­

introducing otters in drainages where they are now extinct. Local

support, the lack of intensive beaver trapping, and the presence of

adequate food resources and good otter habitat should be prerequisites

for re-introduction. If otters are re-introduced, they should be

monitored with implanted radio-transm itters.

Rationale; Historically, eastern Montana supported otters,

and suitable habitat still exists in many areas. A successful re-

introduction would restore this animal as a natural component of the

aquatic ecosystem. Interest by the public and trappers in otters is

considerable, so re-introduction would likely be well received. Radio­

telem etry would allow the success of the program to be monitored,

7. The Department should work toward establishing drainage-

specific otter management regulations. These regulations would be

based on census index data, trapper questionnaires, harvest statistics,

and population studies.

Rationale: Low population density and limited reproductive

potential make otter populations susceptible to over-harvest.

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especially if a rise in beaver pelt prices stimulates trapping activity.

Management based on reliable population information would insure the

conservation of otter populations in Montana.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. REFERENCES CITED

Beidleman, R. G. 1958. Early fur returns of the northwest, J. Mammal. 39:146-147,

Brown, C. J. D, 1971. Fishes of Montana. Montana State Univ., Bozeman. 207pp.

Bugbee, B. A, 1979. Lower Big Hole Ranch, ecological inventory with recommendations for a conservation easement. Bugbee Land Use Consultants, Missoula, MT. 36pp.

Casteel, R. W. 1973. The scales of the native freshwater fish families of Washington. Northwest Sci. 47:230-238.

Chittenden, H. M. 1935. The American fur trade of the Far West. Barnes and Noble, Inc., New York. 2 Vol.

Coues, E, 1893. History of the expedition under the command of Lewis and Clark. Smithsonian Inst., Washington, D. C. 4 Vol.

DeVoto, B, (ed.), 1953. The journals of Lewis and Clark. Houghton Mifflin Co., Boston, 504pp.

Engel, T. 1981. The status of otter populations and some aspects of the 1979 otter harvest. Unpubl. Rept. Minn. Dept. Nat. R es., St. Paul. 10pp.

Erlinge, S. 1968a. Food studies on captive otters (Lutra lutra). Oikos 19:259-270.

______. 1968b. Territoriality of the otter (Lutra lutra). Oikos 19:8 1 -9 8 .

______. 1969. Food habits of the otter (Lutra lutra) and the mink (Mustela vison) in a trout water in southern Sweden. Oikos 20: 1 -7 .

Giles, R. H. (ed.). 1969. Wildlife management techniques. Wildlife Society, Ann Arbor, MI, 623pp.

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Greer, K. R. 1955a. Yearly food habits of the river otter in the Thompson Lakes region, northwestern Montana, as indicated by scat analyses. Amer. Midi. Nat. 54:2 99-313.

______. 1955b. The otter diet—good or bad? Mont. Wildl. 5: 1 4 -1 7 .

______. 1955c. A study of the otter's food habits along a segment of the Gallatin River. Mont. Dept. Fish and Game Proj. No. W-49-R-6, Job No. 11-K, pp. 35-39.

Grenfell, W. E ., Jr. 1974. Food habits of the river otter in Suis un marsh, central California. Calif. Dept. Fish and Game Proj. No, W-52-R-23, Job No. II-l, Sacramento, CA. 17pp.

Grinnell, J ., J. S. Dixon, and J. M. Lins dale. 1937. F urb earing mammals of California. Vol 1. Univ. Calif. Press, Berkeley. 375pp.

Hamilton, W. J ., Jr. 1961. Late fall, winter and early spring foods of 141 otters from New York, New York Fish and Game J, 8: 106-109.

______, and W, R. Eadie. 1964. Reproduction in the otter, Lutra canadensis. J. Mammal. 45:242-252.

Hash, H. 1979. Montana's fur trade: living history, Montana Outdoors 10(6):7-10.

Hill, E, P. 1978. Current harvest and regulation of trade of river otter in the southwestern United States in 1978. Pp. 164-172 m Proc. of the Rare and Endangered Wildl. Symp. R. O. Odom and L. Landers (eds.). Georgia Dept. Nat. R es., Game and Fish Div. Tech. Bull. WL4.

Humphrey, S. E ., and T. L. Zinn. 1982. Seasonal habitat use by otters and Everglades mink in Florida. J. Wildl. Manage. 46: 375-381.

Jachowski, R. L. 1981. Letter to F. E. Newby, deputy director, Mont. Dept. Fish, Wildlife and Parks, Helena.

Jenkins, D. 1980. Ecology of otters in northern Scotland. I. Otter breeding and dispersion in Mid-Deeside, Aberdeenshire. J. Animal. Ecol. 49:713-735.

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Jenkins, D., and G, O, Burrows. 1980. Ecology of otters in northern Scotland. Ill, The use of faeces as indicators of otter (Lutra lutra) density and distribution. J. Animal Ecol. 49:755-774.

______f and R. J. Harper, 1980. Ecology of otters in northern Scotland. II. Analyses of otter (Lutra lutra) and mink (Mustela vison) faeces from Deeside, N. E. Scotland, J. Animal Ecol. 49: 737-754.

Knuds en, G. J. 1956. Preliminary otter investigations--Wise. Fish and Game Proj. No. W-79-R-1, Job No. I-A, Madison, WI, pp. 1 3 1-147.

, and J. B. Hale. 1968, Food habits of otters in the Great Lakes region. J. Wildl. Manage. 32:89-93.

Kruuk, H., M, Gorman, and T, Parrish. 1980. The use of Zn®^ for estimating populations of carnivores, Oikos 34:206-208.

Lagier, K. F, 1950. Studies in freshwater fishery biology. J. W. Edwards, Ann Arbor, MI. 2 50pp.

______, and B, T, Ostenson. 1942. Early spring food of the otter in Michigan, J, Wildl, Manage. 6:244-254.

Liers, E, E, 1951, Notes on the river otter (Lutra canadensis). J, Mammal, 32:1-9.

Linhart, S. B ,, and F. F. Knowlton. 1975, Determining the relative abundance of coyotes by scent-station lines. Wildl. Soc. Bull. 3:119-124.

MacDonald, S. M ., C. F. Mason, and I. S. Coghill. 1978, The otter and its conservation in the River Teme catchment. J. Appl. Ecol. 15:373-384.

Magoun, A. J,, and P. Valkenburg. 1977. The river otter (Lutra canadensis) on the north slope of the Brooks range, Alaska. Can, Field Nat, 91:303-305.

McClellan, J. 1954. An otter catch on the Gila River in southeastern New Mexico. J. Mammal. 35:443-444,

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Melquist, W. E. 1981. Ecological aspects of a river otter (Lutra canadensis) population in west-central Idaho. Ph.D. Thesis. Univ. Idaho, Moscow. 144pp.

. and M. G. Hornocker. 1979a, Methods and techniques for studying and censusing river otter populations. Univ. Idaho F or., Wildl., and Range Exp. Sta., Tech. Rep. 8. 17pp.

, a n d ______. 1979b. Development and use of a telemetry technique for studying river otter. Pp. 104-114 in F. M. Long (ed.). Proc. Second Int. Conf. Wildl. Biotelemetry, Laramie, WY.

Modafferi, R ., and C. F. Yocum. 1980. Summer food of river otter in north coastal California lakes. Murrelet 61:38-41.

Montana Department of Fish, Wildlife and Parks. 1981. Fisheries Division progress reports. Proj. No. F-9-R-28, Job Nos. I-a, I-b, I-d, and XI-c. 85pp.

Mowbray, E, E ,, D. Pursley, and J. A, Chapman, 1979. The status, population characteristics and harvest of the river otter in Maryland. Publ. Wildl. Ecol. No. 2, Maryland Wildl. Admin. 15pp.

Newby, F. 1957. Montana's 1955-56 fur harvest. Mont, Wildl, 7:1 8 -2 3 .

Nilsson, G ., and A. S. Vaughan. 1978. A turning point for the river otter. Natl. Parks and Cons. Mag. 52:10-15.

Northcott, T. H., and D. Slade. 1976. A livetrapping technique for river otters. J. Wildl. Manage. 40:163-164.

Pfister, R. D,, and S. F, Arno. 1980. Classifying forest habitat types based on potential climax vegetation. For. Sci. 26:52-70.

Rust, H, J. 1946. Mammals of northern Idaho. J. Mammal. 27: 308-327.

Ryder, R. A. 1955. Fish predation by the otter in Michigan. J. Wildl. Manage. 30:215-235.

Sheldon, W. G ., and W. G, Toll. 1964. Feeding habits of the river otter in a reservoir in central Massachusetts. J. Mammal. 45:449- 454.

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Stephens, M, N, 1957, The natural history of the otter. Univ. Fed, for Animals Welfare, Potter's Bar, Herts,, England. 88pp.

Tabor, J, E ,, and H, M. Wight, 1977. Population status of the river otter in western Oregon. J. Wildl. Manage. 41:692-699.

Thwaites, R. G. 1907. Early western travels, 1748-1846. A. H. Clark Co., Cleveland. 32 Vol.

Toweill, D. E. 1974. Winter food habits of river otters in western Oregon. J. Wildl. Manage. 38:107-111.

and J. E. Tabor. In press. The northern river otter Lutra canadensis. In J. A. Chapman and G. A. Feldhamer (eds.). Game, pest and commercial mammals north of Mexico. John Hopkins Univ. Press.

Wilson, K. 1954. The role of the mink and otter as muskrat predators In northwest North Carolina. J. Wildl. Manage. 18: 199-207.

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TRAPPER QUESTIONNAIRE

84

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I%S'Emv%B@'m»' €ii%PEEE

OTTER SURVEY

1. How many years have you been trapping on Montana waters? 2. Approximately how many otter have you trapped in Montana? ______3. On lines 1 through 5 below, please list the river sections, major creeks or lakes where you have been trapping during the last four seasons. River. Creek or Lake County A.B.C or D (See Questions #4 below)

3. 4. 5. 4. For each water you listed above, indicate how much otter sign you have seen there by writing the appropriate letter (A,B,C or D) on the line provided. A. I have never seen otter or otter sign along this waterway. B. Otter sign rare but occasionally observed along this waterway. C. Otter sign uncommon but can usually be found in a few specific sites. p. Otter sign common in most areas of this waterway. 5. Please indicate which one of the following statements applies to your trapping. I take special precautions to avoid trapping otter when some are around. I make no specific sets for otter but may catch them in beaver sets. I will set specifically for otter if I have seen fresh sign. Each year 1 make a serious attempt to catch my one otter limit. There are no otter in my area so the above statements don't apply. 6 . What other water—assoelated species do you trap? Beaver Mink Muskrat 7. From your trapping experience in Montana, check the one statement that applies. Otter populations appear to have increased. Otter populations appear to have stayed about the same. Otter populations appear to have decreased. I don't have an indication of otter population trends. 8. Can a careful beaver trapper avoid taking otter by accident? Ko Yes, in some instances Yea, in most cases 9. Will making sets to avoid taking otter reduce a trapper's beaver harvest? No Yes, to a moderate degree Yes, to a significant degree 1 0 . If you have trapped otter in Montana, please indicate whether; All otter I have trapped have been in sets intended for beaver. Most otter I have trapped have been in beaver sets. Most otter I have trapped have been in sets intended for otter. All otter I have trapped have been in sets intended for otter. 11. Optional. Name ______Address ______12. Please write any additional comments on otter populations, season length, limits, etc., on the back of this survey.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A PPE N D IX B

SURVEY ON RELATIVE ABUNDANCE

OF PREY SPECIES

86

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DATE: September 22, 1981 TO: SW Montana Fishery Biologists FROM: K’Jgh Zackheim RE; Fish Populations

As part of my thesis project on river otters in southwestern Montana, I am studying otter food habits on the Beaverhead, Big Hole, Jefferson, Gallatin and Madison Rivers. To analyze the food habit data. I ’d like to have an indication of the relative populations of various prey species on these rivers.

In the space provided below, please list any sections of the five rivers with whose fish populations you are familiar (through electro-shocking, creel surveys, fishing, etc.). For each section you list, place the appropriate number designating population status under each species.

Also, please compare and rank suckers, trout and whitefish in terms of their populations relative to each other. For example, if on a particular river section whitefish are more abundant than trout, which are in turn more abundant than suckers, you would put a "1" under whitefish, a "2” under trout and a "3" ander sucker in the columns at the right side of the chart.

A stamped, addressed envelope is provided for returning the surveys. Thanks for your help and feel free to call me (684-5217 in Twin Bridges) if you have

LS N AT Y Comparative ROM Ranking GN P Estimates E 3 H

Sucker .Trout Whitefish

RIVER & SECTION

Population Status Key Comparative Ranking Key 5 - Abundant 1 - Most Abundant 4 - Common 2 - 2nd Most Abundant 3 - Moderately Common 3 - Least Abundant 2 - Uncommon 1'- Rare (Applies to sucker, trout 0 - Absent and whitefish only) U - Status Unknown

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SUMMARY OF RELATIVE OTTER POPULATIONS, POPULATION TRENDS, AND RECENT HARVEST ON MONTANA RIVERS

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD ■ D O Q. C g Q. Appendix C. Summary of relative otter populations, population trends, and recent harvest on Montana rivers. Tributaries where otters have been trapped or reported are listed. ■D CD 3 A verage R elativ e C/) annual Population density § trendb o harvest^- ranking^ 3 CD REGION 1 8 Clark Fork Drainage (O'3" i Clark Fork, Paradise to Idaho border 0.50 ? 2 Thompson River and lakes 0.00 "n c B ull R iv er 0.00 3" CD Flathead River, Flathead Lake to Paradise 0.00 ? 1 "O3 Jocko River 0.00 o Q. Little Bitterroot River 0.00 a 0.25 o P o st C reek 3 ■D Flathead River, Forks to Flathead Lake 3.00 I 3 O 3" Ashley Creek, Mount Creek 0.25 <—H CD McWinegar Slough 0.50 Q. $ 1—H 3" Flathead River, North Fork 0.25 I/S 3 O Coal C reek 0.00

3 Flathead River, Middle Fork 1.25 s 3 C/) C/) o ' Flathead River, South Fork 0.75 I/s 3 3 Big Salm on 0.00 Danaher Creek 0.00 Spotted Bear River 0.00 White River 0.00 Stillwater River 2.25 I/s 3

Duns ire Cr„ Griffin Cr., Good Cr., Logan Cr., Tally Lk. 0.50 00 CO ::o ■oCD I I Average Relative annual Population density harvest^ trend^ ranking® % o =3 Swan River 0.50 S 2/1 Whitefish River 0.75 ? 2 8 eg- Kootenai Drainage Fisher River 0.00 ? P =3 CD Wolf Creek 0.00 Kootenai River 0.25 D 2 Lake Creek 0.00

CD Libby Creek 0.00 "O Swamp Creek 0.00 cI g ? P o Tobacco River 0.00 =3 ■o Fortine Creek 0.00 S Graves Creek 0.00 & Yaak River 0.25 ? 2 co REGION 2 % Clark Fork Drainage % o 1.00 S/D 2/1 =3 Bitterroot River West Fork of the Bitterroot 0.25 East Fork 0.00 Lolo Creek 0.00 Lost Horse Creek 0.25

oCO CD ■ D O Q. C g Q. Average Relative ■D CD annual Population density harvest®- trend^ ranking® C/) C/) Blackfoot River 0.25 S/D Alice Creek 0.00 CD 8 Clearwater River and lakes 0.25 5 Gold Creek 0.00 Monture Creek 0.25 Nevada Creek 0.00 N orth P o rk 0.00

3. Clark Fork River, Missoula to Paradise 1.25 3" CD F ish C reek 1.00 ■DCD Trout C r., Dry C r., Cedar Cr. 0.25 O Q. aC Clark Fork River, Deer Lodge to Missoula 0.25 3O Flint Creek 0.00 ■O D Little Blackfoot 0.00 Rock C reek 0.00 CD Q. St. Regis River 0.25 Big C r., Deer C r., Savanach Cr. 0.00 ■D CD REGION 3

C/) C/) Missouri Drainage Beaverhead River, Madison Co. 1.25 S 3/2 Beaverhead River, Beaverhead Co. 0.25 S 1 Blacktail Creek 0.25

CO CD ■ D O Q. C g Q.

■D CD A verage R elative

C/) annual Population density 3o" h arv est^ trend^ ranking^ O Red Rock River 0.25 ? 1 8 Upper Centennial 0.25 ci' Horseprairie Creek 0.00 Ruby River, lower 0.25 S 1 Big Hole River, Twin Bridges to Wise River 2.75 S 3/2 3 W ise R iv er 0.25 3" CD Big Hole River, Wise River to Wisdom 0,00 s 1 ■DCD O N orth F o rk 0.00 Q. C Upper Big Hole tributaries 0.00 a O 3 6.00 s 3 ■D Jefferson River O Boulder River 0.75 South Boulder River 0.25 CD Q. Willow Creek 0.00 Gallatin River 2.25 I 3 ■D R ae C reek 0.00 CD 0.75 I 2 C/) East Gallatin River C/) Bridger Creek 0.00 Rocky Creek, Bridger Creek 0.00 West Gallatin 0.25 ? 2 Madison River, Ennis Lake to Three Forks 3.50 I/s 3/2 Madison Dike 0.25 Cherry Creek 0.00 roCD "OCD O Q. C O.g Average Relative ■D CD annual Population density harvest^ trend^ ranking^ C/) 3o" O Madison River, West Yellowstone to Ennis Lake 1.75 I/S 3/2 South Fork 0.25 8 Duck Creek 0.50 W est F o rk 0.75 ci' O'Dell Creek 1.00 Jack C r., Jourdain C r., Wigwam C r., Bear Cr. 0.25 North Meadow Creek 0.50 Ennis Lake 0.00 3 3" CD Missouri River, headwaters to Canyon Ferry 4.50 "OCD Duck Creek, Confederate Gulch 0.00 O Q. Sixteen Mile Creek 0.25 aC O 3 Yellowstone Drainage ■D O Yellowstone River 0.00 I/S 0.00 CD Hellroaring Creek, Slough Creek Q. Mill Cr., Canyon Cr,, Brackett Cr., Mol Heron Cr., Bear Cr. 0.00 Shields River, Wilsall to Yellowstone River 0.75 ■D CD REGION 4 C/)(/) Missouri Drainage Dearborn River 0.00 S/D 2/1 N orth F o rk 0.00 Smith River 0.00 ? 2 Sun River, Cascade Co. 1.00 S 1 CO Ca9 CD ■ D O Q. C g Q. Average Relative ■D CD annual Population density harvest^ trend^ ranking^ C/) C/)

3 O Sun River, Teton Co. and Lewis and Clark Co. 0.75 S 2 3 N orth F o rk 0.25 CD 8 South Fork, Wood Creek and Straight Creek 0.75 5 Elk Cr., Willow Cr., Smith Cr., Little Willow Cr. 0.00 (O' 3 " Sun River Game Range 0.00 i 3 Teton River 0.25 D 1 CD Deep C reek 0.00 c“n 3 . Marias River 0.00 ? 1 3 " CD Sheep Creek 0.00 CD ■D 0.00 ? 2/1 O Judith River Q. C Ross Fork, Box Elder C r., Olsen Cr. 0.00 S- o" 0.00 3 Spring C r., Beaver C r., East Fork Spring Cr. "O O 0.00 ? 1 3 " Musselshell cr 1—H Missouri River, Lewis and Clark Co. 2.75 S 3 Q. g Beaver Creek 0.00 3 O Wolf C reek 0.25 C_ "O CD Missouri River, Cascade Co. 0.75 S 2 3 B elt C reek 0.00 w 5' 3 Missouri River, Choteau Co. 0.25 S 2 Shonkin Creek 0.00 Arrow Creek 0.00 Missouri River, Fergus Co. 0.00 ? 2/1

(O 4^ "OCD O Q. C g Q. Average Relative -O CD annual Population density C/) harvest^ trend^ ranking® 3o" REGION 5 O Missouri Drainage Musselshell River 0.00 ? 1 Yellowstone River Drainage

CD Boulder River 0.00 ?P East Boulder 0.00 3. West Boulder 0.00 3 " CD Stillwater River 0.00 ? 2/1 "OCD O West Rosebud Creek 0.00 Q. C East Rosebud C r., Slough Lake, Phantom Cr. 0.00 a O 3 "O Big Horn River 0.00 ? ? O Buster Creek 0.00

CD Q. Yellowstone River, Sweetgrass Co. 0.00 2/1 Yellowstone River, Stillwater Co. 0.00 1 Yellowstone River, Yellowstone Co. 0.00 P ■DCD (/) &1977-78 through 1980-81 trapping seasons.

^1 = increasing; I/S = increasing or stable; S = stable; S/D = stable or decreasing; D = decreasing; ? = unknown. ^Relative density categories: 3 = highest; 2 = intermediate; 1 = lowest; P = present, but information is inadequate to judge. Categories intermediate between these are indicated as 3/2 or 2/1. CO tn A PPE N D IX D

RADIO-TELEMETRY

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97

M ethods

To determine movement patterns and habitat use, efforts were

made to live-trap, instrument, and monitor otters on the Jefferson

River north of Twin Bridges. Four trap sites were selected in areas

where fresh otter sign was found. The trap sites were all on wooded

islands and the traps were set at sites where otters regularly "hauled

out" onto banks. Modified Hancock traps (Melquist and Hornocker

1979a) were concealed on the banks and checked daily.

On 1 October 1980, after 49 trap-nights spread over 19 days,

a 9,7-kg, 1.29-m long male otter was captured. Based on an assess­

ment of size, tooth wear, and baculum length, the otter was estimated

to be 3 to 5 years old. On 5 October, Wayne Melquist of McCall,

Idaho, performed an intraperitoneal implant of a Telonics transm itter,

using techniques and m aterials described by Melquist and Hornocker

(1979a and 1979b). The otter was released at the original trap site on

the same day.

Subsequent monitoring of the instrumented otter was accom­

plished by using an omnidirectional whip antenna mounted atop an

automobile and a hand-held, 3-element Yagi antenna, which was used

to pinpoint exact locations. When the otter could not be located from

the ground, aerial surveillance of the rivers was conducted using the

Yagi antenna attached to the wing strut of a Piper Super Cub,

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R e s u lts

Because of the otter's mobility and the absence of roads close

to many portions of the rivers, only sporadic monitoring of otter move­

ment was possible. From 6 October 1980 through 16 January 1981, the

instrumented otter was relocated 7 times as it moved consistently up­

stream from its release site on the Jefferson River to the Big Hole

near Glen, a distance of 30 km. From 22 January through 14 February,

the otter was relocated 8 times within a 400-m section of a side channel

of the Big Hole River. This location was 3 km upstream from the 16

January site. After 14 February, no further radio-locations were

obtained, despite repeated ground searches and 3 flights over approxi­

mately 100 km of both the Big Hole and Jefferson rivers.

In 8 instances, a determination was made of the specific site

where the otter was resting or denning. Seven of these locations were

in beaver lodges, including 5 locations in the same beaver lodge on the

channel where the otter resided from mid-January through mid-

February. The other location was beneath an undercut bank on a small

slough about 50 m from the main river channel. All 7 of the beaver

lodge locations were adjacent to frozen-over river channels or ponds

and, in several instances, the otter was detected swimming, and pre­

sumably foraging, under the ice.

Following a snowfall, the tracks of 3 otters and fresh scat were

located about 600 m from the instrumented otter's den. From the track

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record, these otters had apparently been in this vicinity for several

days. However, only 1 otter track was evident near the instrumented

otter's den and no evidence was noted of any encounters between the

group of 3 otters and the instrumented adult male,

Lioss of radio-contact with the otter is probably attributable

to the prem ature failure of the transm itter batteries or to the otter's

movement out of the monitored area. Possibly, the instrumented otter

was trapped and, contrary to state law, the pelt was not submitted for

tagging nor the carcass for collection. Because no obvious benefit

accrues to a trapper for not complying with these laws, this event is

considered unlikely.

D is c u s s io n

The 108-day, 33-km movement by the instrumented adult male

otter parallels M elquist's (1981) reported seasonal 90-day home ranges

of 8-78 km of waterway and his mean values of 28 and 31 km, respec­

tively, for faU and winter ranges.

The use of beaver lodges for denning is also consistent with

M elquist'8 findings. However, the limited number of denning sites

located during radio-monitoring precludes generalization about specific

otter denning needs in southwestern Montana.

The 8 relocations of the instrumented otter in an ice-covered

side channel of the Big Hole River show that, despite a preference for

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open-water areas during winter (Melquist 1981), otters can inhabit

frozen-over waterways. In this instance, an uneven ice surface

created ample air space, a beaver lodge provided a secure den, and

the river flowing beneath the ice served as a foraging area.

The lack of evidence of contact between the instrumented otter

and conspecifics, even when tracks revealed 3 other otters were in­

habiting a nearby river section, supports Melquist's conclusion that

adult males generally remain solitary, except during the breeding

s e a s o n .

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