Kaibab activities in relation to forest characteristics

Item Type text; Thesis-Reproduction (electronic)

Authors Ratcliff, Thomas D., 1943-

Publisher The University of Arizona.

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Link to Item http://hdl.handle.net/10150/554684 KAIBAB SQUIRREL ACTIVITIES IH RELATION

TO FOREST CHARACTERISTICS

by

Thomas Donald Ratcliff

A Thesis Submitted to the Faculty of the

DEPARTMENT OF WATERSHED MANAGEMENT

In Partial Fulfillment of the Requirements For the Degree of

MASTER OF SCIENCE

In the Graduate College

THE UNIVERSITY OF ARIZONA

19 7 4 STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfillment of the requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to bor­ rowers under rules of the Library,

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduc­ tion of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of schol­ arship, In all other instances, however, permission must be obtained from the author.

SIGNED:

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

Associate Professor of Watershed Management ACKNOWLEDGMENTS

I wish to express my appreciation to Dr„ Peter F„ Ffolliott who

served as director of this thesis and who has provided invaluable advice

and assistance throughout my graduate program.

Dr, C, Roger Hungerford and Dr, Phil R„ Ogden served on my grad­ uate committee and provided helpful comments and advice.

Dr, David R, Patton, USDA Forest Service, Rocky Mountain Forest

and Range Experimental Station, Tempe, Arizona, was instrumental in the

development of this project, and has been very helpful in all phases of

the field work and data analysis.

Funding for the project was provided largely by the USDA Forest

Service, Rocky Mountain Forest and Range Experimental Station, Fort

Collins, Colorado, The , Williams, Arizona, pro­ vided housing and assistance during the field study.

This study was also funded as part of the Arizona Contribution

to Regional Research Project, W-119, Evaluation of Alternative Land Uses on Forest, Range, and Other Wildlands,

Many individuals have participated in this research effort in some way. Dr, D, I, Rasmussen, Ken Rogers, Don Mackelprang, and Jim

Dunham helped with various parts of-the field work, Rhey Solomon assisted with the data analysis.

Finally, I wish to thank my wife, Carla, who has been field tech­ nician, typist, and a great source of encouragement during this study, • TABLE OF CONTENTS

Page

LIST OF TABLES a o Q o o o o <> a o a o o a a o o a o o a o c » V

LIST OF ILLUSTRATIONS eoaooooooeooooooooeo VX

ABSTRACT, 0- vii ° 0 ° 00 0 0* 00 000

INTRODUCTION,. » ° *■0* 000 * 00000 1

DESCRIPTION OF STUDY, , , , » • * o«0°o00 00000 3

Objective , , , , , 0 0 0 0 0 0 0 0 0 o0 0 0 0 0 3

Study Area, , , , , o00 000 0 0 0 0. o 0 00 0 3

Field Methods , , , O0c0 0 0 O0 O0 0 O0 0 0 4 8 Analytic Methods, , ° * * ° ° 00 0000 00o0

RESULTS AND DISCUSSION, , , ° 00*o0 000 0000 10

Trapping, , , , , , 000000 000 0000 10

Forest Density Parameters O 0 0 0 0 0 0 0 o 0 o 0 o . 12

All Tree Species' 0 0 0 00 00000o00 12 Ponderosa Pine, O» o 0 o 0 0 0 o 0 0 0 0 0 0 17 Pinyon, , , 0 0 0 0 o0 o 0 0 0 0 0 0 0 20

Juniper , , o 00 0 o 0 0 o o 0 Q0 0 o 0 22

Gambel Oak, o o 0

Site Index, , , , , 0 0 0 0 0 0 0 0 0 0 0 0 0 23

Nests ,,,,,,, o 0 0 0 0 0 0 0 0 0 0 0 o 0 , 23 Habitat Rating, , , -°-° ° ° c00o 00000 0 • 27

CONCLUSIONS 0 0 0 0 .0 0 0 0 0 29

APPENDIX A: MATRIX OF CORRELATION COEFFICIENTS 31

APPENDIX B; METRIC CONVERSION TABLE, , , . <, , , , „ „ , , , 37

LITERATURE CITED, ,,,,,,,,,,,,,,,,,,,,,, 3^

IV LIST OF TABLES

Table Page

lo Summary of Variables Tested for Association with Kaibab Squirrel Numbers Per Trapsite, ***.,, 13

2, Mean and Range of Variables Tested for Association with Squirrel Numbers Per Trapsite* 000 » 0 0 o a o 000 «? 0 o » o » 13

v LIST OF ILLUSTRATIONS

Figure Page

1. Abert's Squirrel in Handling Cone with Ear Tag Attached ® ^ ® ® ^ ® ® ® @ ® » 6

2. Number of Kaibab Trapped or Known to be on Trapsites . 11

3. Relationship between Kaibab Squirrel Numbers and Basal Area of All Ponderosa Pine Size ClaSSOS c o ■ C ' C C C O O 'C C C 0,0 0 O O O 0 o o o .18

4. Relationship between Kaibab Squirrel Numbers , ^ and Basal Area of Ponderosa Pine Greater than 6 Inches dbh® ooooooooooooooo . W

5. ' Relationship between Kaibab Squirrel Numbers and Volume of Ponderosa Pine 6-24 Inches dbh „ . . 21

6c Douglas-fir Twig Utilized as a Food Source by Kaibab Squirrel® oocooooocooooooo %

7. Relationship between Kaibab Squirrel Numbers and Nests on Trapsites . 26

vi ABSTRACT

Kaibab squirrel numbers were estimated on nine trapsites on the

Kaibab National Forest in northern Arizona* The squirrel proved dif­

ficult to trap, requiring 224 trap days for each squirrel capture*

Forest characteristics were measured on the nine trapsites and

were compared to Kaibab squirrel numbers by using simple linear cor­

relation coefficients in an attempt to identify and quantify empirical

associations* Sixteen significant (a ^ 0*10) associations were ob­

tained*

An evaluation of the association analysis showed basal area of

all ponderosa pine size classes and number of Kaibab squirrel nests per

trapsite to be significantly associated with Kaibab squirrel numbers*

Using the former two variables, a conceptual model was developed where-

. by a natural resource manager may rank areas of squirrel habitat in

terms of potential quality*

vii INTRODUCTION

i The Kaibab squirrel (Sciurus kaibabensis) is one of North

America’s most attractive.„ It lives in the ponderosa pine

(Finns ponderosa) forests of the , north of the Grand

Canyon, in Coconino County, Arizona, The. Kaibab squirrel, long of interest to naturalists and biologists, is a member of the tassel­ eared subgenus of tree squirrels, Otosciurus (Nelson 1899)o

The Kaibab squirrel was described as a species in 1904 by

C, Hart Merriam, based on characteristics of a specimen collected near the head of the Kaibab trail in National Park

(Bailey 1931)« Taxonomists still do not fully agree on the classi­ fication of the squirrel as a distinct species, some preferring to list the Kaibab as a subspecies of the Abert’s squirrel (Sciurus aberti) (Cockrum I960)„ However, the Kaibab squirrel has been dif­ ferentiated from the Abert’s squirrel by two major coloration characteristics: an all-white tail as opposed to the Abert’s grey tail with white fringe, and a black ventral side in place of the white belly of the Abert’s, Both squirrels have grey sides and a rufus dorsal stripe. The Abert’s squirrel is found in the ponderosa pine forests of Colorado, Utah, New Mexico, Arizona and in the

Mexican states of Durango and Chihuahua (McKee 1941), The Kaibab squirrel is restricted to 220,000 acres of the Kaibab Plateau; about

1, The authority used for nomenclature is Hall and Kelson (1939), and Kearney and Peebles (1969) for plants.

1 2 one tenth, of its range is in Grand Canyon National Park and the re­ mainder on the Kaibab National Forest (Dodge 1965)«

Various workers have cited the Kaibab squirrel as an example of divergent evolution (McKee 1941, Cahalane 1947, Dodge 1965)» Theoreti­ cally, a common ancestor of the Abort*s and Kaibab lived on both sides of the Grand Canyon,, Those squirrels on the north side of the Canyon were isolated during the Pleistocene (MacClintock 1970)„ Squirrels exhibiting the coloration characteristics of the Abert’s have been found on the Kaibab Plateau, and animals with Kaibab colorings have been collected south of the Grand Canyon (Hall 1967)<■

The Abert *s squirrel is hunted as small game in Arizona (Brown

1972), but the Kaibab squirrel has been protected since Arizona achieved 2 statehood. The Kaibab squirrel was included in the 1973 edition of

Threatened Wildlife of the United States (USDI 1973)« Estimates of total Kaibab squirrel numbers range from 550 (MacClintock 1970) to

"optimum numbers" for the squirrel's habitat (Webb 1969)« A population. of 3,000 to 4,000 squirrels has been estimated by several workers

(Rasmussen 1941, Hall 1967, Webb 1969)0

Tassel-eared squirrels are limited in distribution to ponder— osa pine forests, and the dependence of the on ponderosa pine has been reported (Keith 1 9 6 5 ) 0 Squirrels derive food, cover, and protection from pine. Mixed conifer forest above, and pinyon-juniper below the belt of pure pine is marginal habitat (Hall 1967),

2, Personal communication, David E, Brown, Small Game Super­ visor, Arizona Game and Fish Department, April 2, 1974o DESCRIPTION OF THE STUDY

This study was initiated as a part of a long-term investigation by the USDA Forest Service (Kaibab National Forest and Rocky Mountain

Forest and Range Experimental Station) to describe the effects of tim­ ber harvest, on the Kaibab squirrel* The field portion of the study was conducted between December 1972 and September 1973«?

Objective

The primary objective of this study was to identify and quan­ tify empirical relationships between Kaibab squirrel numbers and forest parameters*

Study Area

The study area was located approximately three miles west of

Jacob Lake/ Arizona* Jacob Lake is approximately 80 miles west of Page,

Arizona and 40 miles south of Kanab, Utah* Specifically, the study was conducted on the North Kaibab Ranger District of the Kaibab National •

Forest*

Nine trapsites were located oh the Buck timber sale, a 6,000- acre sale of virgin ponderosa pine* Elevations range from 7,600 feet to

8,200 feet* Soils are of the Soldier Cobbly loam type (USDA, Soil Con­ servation Service-1972)* The average ponderosa pine site index for the nine sites is 70 feet at 100 years (Meyer 1961)*

Study sites were chosen with considerations for timber diversity between sites, continuity of timber on individual sites, representation 4 of surrounding physiographic conditions, and some evidence of squirrels on individual sites.

Field Methods

Previous work with tassle-eared squirrels indicates that mark recapture live-trapping provides the best estimate of squirrel numbers

(Keith 1965* Farentinos 1972)» Experience gained in another study near

Happy Jack, Arizona, pointed out three important considerations in trap­ ping squirrels: (1) a density of two traps per acre is desirable for good coverage of an area; (2) the attention required in trapping be­ comes limiting at approximately 40 traps per site; and (3) the range of squirrels is restricted enough that a trapsite of 20 to 25 acres should provide meaningful mark-recapture data (Patton 1972), A grid, 1,000 feet on a side with traps placed at 250-foot intervals, was established on each trapsite. Alternating rows of five and four traps were placed so that the maximum distance between any two traps was 177 feet. Thus, each trapsite had 41 traps, providing a trap density of approximately two traps per acre, 3 Tomahawk Ho, 202 livetraps were used in this study. This trap operates.on a trip-plate principle. Unshelled peanuts, either raw or roasted, were used as bait. Bait was placed behind the trip-plate and around the entrance of the trap to attract squirrels to the trap.

Trial trapping on two trapsites in March and April 1973 resulted in a poor catch response. This was attributed to the large accumulation

3* Trade names and company names are used for the benefit of the reader, and do not imply endorsement and preferential treatment. of snow on the study area and a reluctance of squirrels to feed on the ground during periods of heavy snow cover. The trapping data presented in this study were collected from June through August 1973e Trapping periods were 20 days per trapsite, and three sites were trapped simul­ taneously, Traps were checked twice daily, at noon and just before dusk. Observations indicated peak squirrel activity periods to be ear­ ly in the morning and again just before dark. Checking and baiting 1 traps at noon and dusk minimized human interference on the trapsites, and insured that no squirrel would enter a trap in the afternoon and remain overnight, - •

Once a squirrel was caught, it was removed from the trap by use of a handling cone constructed from hardware cloth and canvas (Giles

1971)= The squirrel was ear-tagged with a numbered aluminum tag (No,

4-q.l, National Band and Tag) and a colored plastic washer. This tag and washer arrangement allowed recognition of the individual when sub­ sequently recaught or sighted (Figure 1),

Occasionally a squirrel injured itself while confined in a trap. In sUch cases, the squirrel was briefly exposed to Hetofane, an. inhalent anesthetic, which renders the animal unconscious (Barrie 1972),

The animal was exposed to Hetofane by holding the handling cone in the mouth of a plastic one-half gallon jar which contained a cotton ball soaked with a few drops of Hetofane, A fifteen to twenty second ex­ posure to the anesthetic was sufficient to immobilize the squirrel to allow removal of the animal and application of an antiseptic to the injured area. The animal was then allowed to recover for fifteen to twenty minutes in a trap before it was released. No squirrel failed 6

Figure 1. Abert's Squirrel in Handling Cone with Ear Tag Attached, to recover and resume normal activities in approximately forty such

treatments in this study and associated trapping*

Kaibab squirrels build large, bulky nests of ponderosa pine

twigs, needles, leaves and any other available material* These nests

are usually located in ponderosa pine trees, near the bole of the tree

or in a fork of the bole* Each traps!te was systematically searched

for squirrel nests, and the number and location of nests on each trap™

site were noted* No attempt was made to determine whether a nest was

active or inactive at the time of the search*

Tree measurements were made on forty»one one«tenth~acre circu™

lar plots on each trapsite to describe the forest'characteristics* Each

trap location was used as a plot center* All trees were tallied by

.species and classified by two inch diameter (dbh) classes* Trees which

did not reach breast height (4^2" feet) were placed in the 0 to 2 inch

dbh class* A tree was counted if any portion of the trunk was within

the plot* Tree diameters were estimated with a Biltmore stick,(Avery

1969 )<, A clinometer was used to measure the height of the tree nearest

the center of the plot* Volumes of trees were computed in cubic feet

per acre (Myers 1963), When the tree nearest the.center of the plot

was dominant or co~dorainant with no evidence of physical damage, an

increment core was taken from that tree at dbh to derive an estimate

of site index (Meyer 1961)* Any additional information regarding the

plot, such as nests, red-squirrel (Tamisciurus hudsonicus) middens,

or peculiar site features, was recorded* 8

Analytic Methods

To test for correlation between Kaibab squirrel numbers and forest parameters, some indicator of squirrel numbers was required. By counting squirrels actually caught or known to be on the trapsites dur­ ing the twenty day trapping period, a minimum index to squirrel numbers was obtained for each trapsite. The index procedure is similar to one used by Mosby (1969)»

A simple linear correlation analysis was conducted to empiri­ cally associate squirrel numbers with thirty-seven independent varia­ bles. These variables included?

(1) Humber, basal area, and volume per acre of all trees

on the plot.

(2) Number, basal area, and volume per acre of all ponder-

osa pine size classes.

(3) Number, basal area, and volume per acre of all ponder-

osa pine greater than 6 inches dbh.

(4) Number, basal area, and volume per acre of all ponder-

osa pine 6 to 24 inches dbh.

(5) Number, basal area, and volume per acre of all pinyon

(Pinus edulis).

(6) Number, basal area, and volume per acre of all juniper

(Juniperus spp.),

(7) Number, basal area, and volume per acre of all Gambel

oak (Quercus gambelii). 9

(8) Number, basal area, and volume per acre of all Douglas*

fir (Pseudotsuga menziesii),

(9) Number, basal area, and volume per acre of all quaking

aspen (Populus tremuloides)*

(10) Ponderosa pine site index*

(11) Numbers of Kaibab squirrel nests per trapsite*

A matrix of correlation coefficients showing association among the 37 independent variables is presented in Appendix A* RESULTS AND DISCUSSION

During the winter of 1972-1973, the Jacob Lake weather station recorded, over 200 inches of snow, approximately twice the amount of an average winter according to long time winter residents. The sever­ ity of weather conditions may have had detrimental effects on Kaibab squirrel populations. However, these effects may not be known until similar trapping is conducted on the same, trapsites. With these re.™ straints in mind trapping and forest density parameters will be discussed.

Trapping

In this study, 7,380 trap days produced twenty known individual

Kaibab squirrels and thirty-three total catches. An average of 224 trap days was expended per catch; thus, trapping success was consider­ ably lower than reported by earlier workers in similar circumstances with Abert's squirrels (Keith 1969)o

Known individual squirrels per trapsite are illustrated in

Figure 2, Although differences in squirrel numbers per trapsite were relatively small, it should be pointed out that trapping on all nine sites was conducted in exactly the same manner, and all trapping was done within a seventy day period. Furthermore, no unmarked individuals were trapped in the final five days of the twenty day trapping period on eight of the nine sites, suggesting few unmarked squirrels remained on these sites,

10 Figure 2. Number ofortoTrapped Squirrels Number Kaibab Known onbeTrapsites. 2.Figure SQUIRREL NUMBERS 6 3 4 2 5

TRAPSITE 4

5 8 H H 12

The values of squirrel numbers per site may have greatest mean­

ing when viewed as an index to minimum'squirrel numbers per site, be­

cause a known number of squirrels can be attributed to each site during

a specific time period,, Using this index to minimum squirrel numbers,

the nine study sites were empirically compared to 37 independent varia­

bles, which were quantified in a more rigorous sense. The correlation

of squirrel numbers and independent variables, indicated by simple

linear correlation coefficients, is outlined in Table 1*

It is emphasized that the application and interpretation of the

results of this study should not be extended beyond the limits of the independent variables sampled on the study area (Table 2),

Forest Density Parameters

Although the nine trap sites in this study were located, on the

same virgin ponderosa pine forest, an attempt was made to differentiate

the trapsites with respect to forest density and tree species composition.

All Tree Species

Cover is an essential ingredient in any wildlife habitat. An

attempt was made, to describe cover in this study by evaluating the

associations between squirrel numbers and number, basal area, and vol­

ume of all trees per acre. Total basal area and volume per acre were

significantly associated with squirrel numbers (r = 0,62 and 0,60,

respectively), whereas total trees per acre was not significant. One possible explanation for number of trees per acre not being significant is that numbers with no consideration for tree size may not provide an

adequate measure of cover in uneven-aged forests. 13

Table 1: Summary of Variables Tested for Association with Kaibab Squirrel Numbers Per Trapsite*

Variable Correlation Coefficient

Total'trees-all species

Numbers per acge 0,51. Basal area-(ft ) per acre 0.62* Volume (ft ) per acre 0.60*

Ponderosa Pine

Numbers per acge • 0,51 Basal area (ft ) per acre 0.72* Volume (ft ) per acre 0.59*

Greater than 6 inches dbh Numbers per acge 0.37 Basal area (ft ) per acre 0.69* Volume (ft ) per acre 0.57

6=24 inches dbh. Numbers per acge 0.32 Basal area-(ft ) per acre 0.57 Volume (ft ) per acre 0.63* 2 Basal area (ft ) per acre 8-10 inch dbh classes -0.03 10-12 inch dbh classes 0.35 12-14 inch dbh classes -0.02 14-16 inch dbh classes 0.67* 16-18 inch dbh classes 0.71* 18-20 inch dbh classes 0.37 20-22 inch dbh classes 0.64* 22-24 inch dbh classes 0.12 14

Table 1, Continued

Variable Correlation Coefficient

Pinyon

Numbers per- acge ^0,75* Basal area (ft ) per acre -0,59* Volume (ft ) per acre -0,49

Juniper

Numbers per acre -0,63* Basal area,(ft ) per acre -0,48 Volume (ft ) per acre —0,42

Gambel oak

Numbers per acre -0,30 Basal area^(ft ) per acre -0,57 Volume (ft ) per acre -0,50

Douglas-fir

Numbers per acre 0,21 Basal area,,(ft ) per acre 0,20 Volume (ft ) per acre 0,20

Quaking aspen

Numbers per acre 0,73* Basal area (ft ) per acre 0,68* Volume (ft ) per acre 0,67*

Ponderosa pine site index —0,06

Nests. 0,68*

* Significant at a = Qo10 Table 2s Mean and Range of Variables Tested for Association with Squirrel Numbers Per Trapsite*

Variable ____ Mean ' Range

Squirrel numbers per.trapsite 2.2 0 — 5

Total trees-all species

Numbers per acge 610 - 181 e*e 1044 Basal area (ft ) per acre 156 122 » 175 Volume (ft ) per acre 5074 3807 - 6019

Ponderosa Pine

Numbers per acre 580 313 1009 Basal area (ft ) per acre 149 114 — 171 Volume (ft ) per acre 5039 3786 - 6010

Greater than 6 inches dbh Numbers per acge 83 54 - 105 Basal area(ft ) per acre 138 109 — 161 Volume (ft ) per acre 4837 3536 - 5853

6-24 inches dbh Numbers per acge 71 44 — 94 Basal area (ft.) per acre 79 50 - 108 Volume (ft ) per acre 2225 1462 — 3062 2 Basal area (ft ) per acre 8-10 inch dbh classes 4.3 2 — 8 10-12 inch dbh classes 4.4 1 — 9 12-14 inch dbh classes 9.0 1 — 14 14-16 inch dbh classes 8.6 3 — 16 16-18 inch dbh classes 10.7 5 - 17 18-20 inch dbh classes 12.9 7 — 21 20-22 inch dbh classes - 12.7 8 - 19 22-24 inch dbh classes 13.4 6 - 20 16

Table 2, Continued

Variable Mean Range

Pinyon

Numbers per acre 5 0 - 17 Basal area_,(ft ) per acre 0,2 0 00 1 Volume (ft ) per acre 3 0 - 21

Juniper

Numbers per acge 7 0 •*» 22 Basal area_.(ft ) per acre 1 0 ~ 6 Volume (ft ) per acre 9 0 - 56

Gambol oak

Numbers per acge 8 0 - 29 Basal area_(ft ) per acre 0,5 0 e° 2 Volume (ft ) per acre 4 0 - 11

Douglas-fir

Numbers per acge 2 0 - 18 Basal area_,(ft ) per acre 0,2 0 - 2 Volume (ft ) per acre 4 0 ««» 37

Quaking aspen.

Numbers per ac^e 7 0 => 60 Basal area-,(ft ) per acre 1 0 - 4 Volume (ft ) per acre 14 o - 63

Ponderosa pine site index >70 65 “ 77

Nests per trapsite 4 1 - 8 17

Ponderosa Pine

Previous workers have reported close associatioiis Between tassle^eared squirrels and ponderosa pine (Keith 1965^ Hall I9 6 7 ), For this reason^ squirrel, numbers were compared to numbers^ basal area^ and volume per acre of all ponderosa pine (i» ea * all size classes combined)^

Basal area arid volume per acre.of all ponderosa pine resulted in signify leant correlation coefficients (ri = 6 ,7 2 ^ r-~ d^5 9 » respectively) 5 whereas numbers per acre of all ponderosa pine v/as riot significant^

Since ponderosa pine was the dominant tree species on all trapsitds^ the same explanation of why numbers of ponderosa pine per acre did riot reach a significant level as given in total trees per acre may apply here, A graphical representation of squirrel numbers versus basal area of ponderosa pirie per acre is presented in Figure

Pattori (1974) found no Abert*s squirrel nests in ponderosa pirid trees less than 8 inches dbh^ Field observations have shown littld evidence of squirrels feedirig in trees smaller thari this sizd class^

Correlation coefficients were computed id assess the assdeiatiori tween squirrel numbers and number^ basal area^ arid volume per acre §f ponderosa pirie greater than 6 inches dbha Basal area of poriderdsd pine greater than 6 inches dbh had a sigriificarit association (r = Q$£§)

(Figure k)6 No association was found betweeri squirrel numbers aril number dr volume of ponderosa pirie greater than 6 inches dbha

To further evaluate specific poriderosa pirie size classes with

Kaibab squirrels ^ squirrel numbers were associated by correlation coefficients with number,- basal area^ arid volume peri ad re of ponderosa pine 6=24 inches dbh,- Volume per acre of ponderosa pirie 6-24 iridhes iue3 RelationshipKaibabbetweenSquirreland ofNumbers Basal All Area Ponderosa Figure3. SQUIRREL NUMBERS 2 4 3 6 5 I Pine Size Classes,PineSize ! Squirrels Squirrels aa Area Basal 2 5 4 2 8 TRAPSITE % 1 . i n 180 140 100 160 120 40 40 60 60 20 80

BASAL AREA-SQUARE FEET PER ACRE iue4 RelationshipandbetweenKaibabofSquirrel NumbersBasal Area Ponderosa Pine 4.Figure SQUIRREL NUMBERS 4 2 3 5 6 Greater thanGreater I aa Area Basal Squirrels 6 Inches dbh.Inches 2 4 5 2 8 TRAPSITE % 1 140 H 100 120 40 40 180 160 60 60 80 20

BASAL AREA-SQUARE FEET PER ACRE

VO H 20 dbh was significantly associated (r = 0 ,6 3 ) with squirrel numbers

(Figure 5)» Number and basal area of ponderosa pine 6-24 inches dbh showed no association.

Earlier workers have pointed out the importance of ponderosa pine in the 8 = 2 4 inch dbh class in the biology of tassle-eahed squir­ rels (Keith 1965s Patton and Green 1970, Patton 1974)* Hall (1967) and

Patton (1974) have discussed basal area as a dominant factor in pre­ ferred habitat of these squirrels. In this analysis, basal area of ponderosa pine was significantly correlated with squirrel numbers in two of three tests for association involving these two variables. For this reason, a further analysis was conducted to compare squirrel num­ bers with basal area in each two inch dbh class of ponderosa pine ranging from 8 to 24 inches dbh. Size classes with significant cor­ relation coeffiecients were; 14- 1 6 inch dbh class (r - 0 ,6 4 );16-18 inch dbh class (r = 0 ,7 1 )? 2 0 - 2 2 inch dbh class (r = 0 ,6 4 )? the 1 8 - 2 0 inch dbh class showed no association with squirrel numbers. Thus, the dependence of tassle-eared squirrels on the size classes of ponderosa pine 8 - 2 4 inches dbh and especially 1 4 - 2 2 inches dbh, seems supported within the range of the data examined in this study,

Pinyon

Throughout its range, southwestern ponderosa pine is usually bordered at the lower elevational limit by stands of pinyon-juniper.

Some pinyon and juniper were encountered on seven of nine trapsites.

Significant correlation coefficients were obtained when number and basal area of pinyon were tested for association with squirrel iue5 RelationshipandofKaibab betweenSquirrelNumbersVolume Ponderosa Pine 5.Figure SQUIRREL NUMBERS 5 4 4 3 r- 6 2

i 6-24 Inches dbh.6-24 Inches I Volume I I :/l / f Squirrels 8 3 4 3 6 TRAPSITE I i 2000 2400 3200 2800 1200 400 1600 800

VOLUME-CUBIC FEET PER ACRE 22 numbers (r = -0,75, r = -0,59)» Volume per acre of plnyon showed no association with squirrel numbers. Two possible explanations could account for these results; (1 ) since squirrel numbers and measures of pine density are positively associated, and there is an inverse rela­ tionship between ponderosa pine and pinyon densities, these results could be data artifacts; or (2 ) the negative association may result because, as pinyon density increases, ponderosa pine density decreases and squirrel habitat is lowered in quality.

Several times during the field portion of this study, pinyon were located which had been utilized as feed trees by squirrels. One squirrel was seen clipping terminal twigs and feeding on the inner bark. The seeds of the pinyon are large, but pinyon cone centers were never found as litter beneath pinyon trees as is the case when ponderosa pine cones are utilized as food, Reynolds (1966) has report­ ed the use of pinyon by Abert’s squirrels, juniper

When squirrel numbers were tested for association with juniper number, basal area, and volume per acre, only number per acre resulted in a significant value (r = 0,63)» Juniper and ponderosa pine densi­ ties exhibit a similar inverse relationship to the relationship of ponderosa pine and pinyon, Therefore, the same explanations' of a neg­ ative correlation coefficient may apply here. Gambel Oak

Gambel oak is a mast producing species? which provides a valua­ ble food source where the oak is abundant (Reynolds, Clary and Ffolliott

1970)* Patton (1974) points out the value of oak in mast producing size in describing cover sites for Abart’s squirrels. When analyzed with squirrel numbers, number, basal area, and volume per acre of Gambel oak showed no significant associations, Gambel oak on the study area commonly grow in dense clumps with individual stems of small diameter; these clumps of oak may produce little mast or nesting cover, provide ing little benefit to Kaibab squirrels,

Douglas-fir

Douglas-fir occurred in sample plots on three of nine trapsites,

Number, basal area, and volume per acre of Douglas«fir showed no asso­ ciation when compared to squirrel numbers. However, during the study, several instances were noted where Douglas-fir trees were used as a food source in the early spring. As many as three squirrels have been observed feeding on young buds in a single Douglas-fir tree (Figure 6),

The use of Douglas-fir as a, food source by tassle-eared squir­ rels has not been reported previously. Evidence of similar use of

Douglas-fir by Abert’s squirrels has since been observed near Heber,

Arizona, and near Rose Canyon in the Santa Catalina Mountains, near

Tucson, Arizona,

Quaking Aspen

When tested for association with squirrel numbers, number, basal area, and volume per acre of quaking aspen resulted in significant 24

Figure 6, Douglas-fir Twig Utilized as a Food Source by Kaibab Squirrel. correlation coefficients (r = 0 .7 3 , 0 *6 8 , and 0 *6 7 , respectively)*

Aspen was recorded on three of nine.sites; however, ten of the twenty squirrels trapped during the study, were■taken on these three sites*

Thus, the association between squirrel numbers and aspen obtained in this analysis may be artifacts of the data rather than an indication of a natural association between an independent and dependent variable*

Site Index

Site index and squirrel numbers showed no association* The average site index for the nine trapsites was 70 feet at 100 years with a range of 65 to 77 feet at 100 years (Meyer 1961)* The narrow range of site index values for the nine trapsites could account for a lack of significant association between squirrel numbers and site index*

Hosts

Thirty-six nests were located on the nine trapsites* Nest and squirrel numbers per site are graphically presented.in Figure 7* A test for association between squirrel numbers and nests per site re­

sulted in a significant correlation (r = 0*68)» The association be­

tween squirrel numbers and nests per trapsite suggests that squirrel nests may be an indicator of the relative abundance of squirrels on

a particular area, and an indicator of the value of a site as squirrel habitat. iue? RelationshipandonKaibabbetweenSquirrel Numbers NestsTrapsites. ?•Figure SQUIRREL NUMBERS 5 3 4 4 r- 6 2 Nests Squirrels 1 4 3 4 6 TRAPSITE I 1 4 2 3 6 5 7 8 9 I

NUMBER OF SQUIRREL NESTS % 27

Habitat Rating • ‘ ) A natural resource manager may desire to evaluate one site with another in terms of Kaibab squirrel habitat or relative abundance of squirrels* As pointed out earlier, live-trapping and markerecapture population analysis of tassel-eared squirrels is difficult and time consuming* Thus, some technique whereby site characteristics might be evaluated as squirrel habitat with respect to several similar sites is needed*

An assessment of the correlation coefficients in Table 1 showed

Kaibab squirrel numbers to be associated with basal area of all ponder- osa pine, basal area of ponderosa pine greater than 6 inches dbh, and number of squirrel nests per trapsite* The manager may have access to basal area of ponderosa pine from previous work, such as a timber inventoryo Number of squirrel nests per trapsite may be obtained by searching representative areas on each of several similar sites* The association of some other variables (i„e», aspen numbers, basal area and volume), may not necessarily reflect cause-and-effect on-site associations of independent and dependent variables*

In consideration of these criteria, multiple correlation anal­ yses were conducted to examine, initially, the association between squirrel numbers as a dependent variable and basal area per acre of all ponderosa pine and number of squirrel nests per site as indepen­ dent variables* In this initial analysis, the coefficient of determina­ tion was 0*77, A similar analysis of squirrel numbers versus basal area per acre of ponderosa pine greater than 6 inches dbh and squirrel 28 nests per site resulted in a coefficient of determination of 0 ,7 2 ,

Therefore, based on the range of the source data in this study, an evaluation of squirrel nest numbers and basal area per acre of ponder- osa pine may allow ranking of several squirrel sites in terms of poten­ tial squirrel habitat.

From the above relationship of squirrel numbers, basal area per acre, and nests per site the following general model of habitat evaluation may be drawn;

Basal Area / Acre Nest Ranked Habitat (ponderosa pine) Abundance____(potential quality)

High Many ++

High Few +

Low Many +

Low Few 0

This conceptual model is intended to predict relative potential of squirrel habitat only. Variations from area to area are to be ex­ pected, However, the model may prove useful to the natural resource manager in evaluating several sites in terms of potential habitat quality.

Since readers of this thesis may desire a metric equivalent of all values enumerated herein, a conversion table for all units used in this thesis is presented in Appendix B, CONCLUSIONS

Trap-recapture population analysis of Kaibab squirrel numbers is' difficult and time-consuming, and does not lend itself to statistical analysis by most methods of population estimation. Therefore, in this study, population estimates were the minimum number of known squirrels per trapsite.

When thirty-seven independent variables were compared to Kaibab squirrel numbers by means of simple linear correlation coefficients, sixteen significant relationships were identified and quantified.

The variable most consistently associated with Kaibab squirrel numbers was basal area of ponderosa pine, including total ponderosa pine, ponderosa pine.greater than 6 inches dbh, and ponderosa pine in the

14-16, 16-18 and 20-22 inch dbh classes.

By using two of the variables which were significantly asso­ ciated with squirrel numbers in this study (i,e,, basal area of all ponderosa pine size classes and number of Kaibab squirrel nests per trapsite), a method of rating areas of squirrel habitat in terms of potential quality was devised. This conceptual model may prove useful to natural resource managers in evaluation of Kaibab squirrel habitat potential.

Further study of the Kaibab squirrel and its habitat is needed • to evaluate the empirical relationships identified and quantified in . this study. Further study may also provide information which will allow development of timber management plans which provide for 29 30 maximum production of ponderosa pine in the size and density ranges to insure good potential squirrel habitat, while maintaining accept­ able levels of timber production. APPENDIX A

MATRIX OF CORRELATION COEFFICIENTS

Description of Variables Included in Matrix of Correlation Coefficients

Variable Description

A . Squirrel numbers per site

XI Numbers per acre-all ponderosa pine X2 Basal.area per acre-all ponderosa pine X3 Volume per acre-all ponderosa pine

X4 Numbers per acre-pinyon X3 Basal area per acre-pinyon X6 Volume per acre-pinyon

X? Numbers per acre-juniper X8 Basal area per acre-juniper X9 Volume per acre-juniper

X10 Numbers per acre-Gambel oak XII Basal area per acre-G-ambel oak X12 Volume per acre-Gambel oak

X13 Numbers per acre-Douglas-fir Xlk Basal area per acre-Douglas-fir X15 Volume per acre-Douglas-fir

X16 Numbers per acre-quaking aspen XI? Basal area per acre-quaking aspen X18 Volume per acre-quaking aspen

Xlg Numbers per acre-ponderosa pine greater than 6 inches dbh X20 Basal area per acre-ponderosa pine greater than 6 inches dbh X21 Volume per acre-ponderosa pine greater than 6 inches dbh

31 3a

Variable Description

X22 Numbers per acre-ponderosa pine 6 - 2 4 inches dbh X23 Basal area per acre«ponderosa pine 6 * 2 4 inches dbh X24 Volume per acre-ponderosa pine 6 * 2 4 inches dbh

X25 Ponderosa pine site index

X26 Number of Kaibab squirrel nests per trapsite

X2? Numbers per acre-all tree species X28 Basal area per acre-all tree species X29 Volume per acre-all tree species

BA 8 Basal area per acre-all ponderosa pine 8-10 inches dbh BA 10 Basal area per acre-all ponderosa pine 10-12 inches dbh BA 12 Basal area per acre-all ponderosa pine 1 2 - 1 4 inches dbh BA 1 4 Basal area per acre-all ponderosa pine 14-16 inches dbh BA 16 Basal area per acre-all ponderosa pine 16-18 inches dbh BA 18 Basal area per acre-all ponderosa pine. 18-20 inches dbh BA 20 Basal area per acre-all ponderosa pine 20-22 inches dbh BA 22 Basal area per acre-all ponderosa pine 2 2 - 2 4 inches dbh Matrix Showing Association between Kaibab Squirrels and 37 Independent Variables

Variable A XI X2 X3 Xif X5 X6 X? X8 X9 X10 Xll X12 X13 X14

X1 .51

X2 ,72* .32

X3 ,59* .20 ,89*

X4 -.75* -.34 -.89* -.81*

X5 -.59* -.44 -.89* -.75* .91*

X6 1 CO -.49 -.44 ■s -.67* .81* .98*

X7 -.63* — . 23 -.55 — .28 .35 .36 ,33 x8 -.4 8 -.56 -.59* -.26 .60* .81* .86* .41

X9 -.42 -.46 -.75* -.54 .67* .91* .97* .37 .91*

XlO — .30 .33 -.63* -.47 .53 .51 ,52 .25 .37 .47

Xll -.57 -.11 -.25 .11 .38 .25 .20 .51 .49 .18

X12 -. 5 0 .23 -.7 2 * -.3 8 * .71* .6 0 * .55 .31 .38 .44 .95* .53

^ ,21 -.18 .29 .12 - .28 - .20 -.18 - . 3 8 - . 2 2 - . 2 0 -.31 -.35 -.34 xlZi- .20 -.20 . 28 .13 -.29' - .19 - .18 -.37 - . 2 2 -.19 -.31 -.34 -.34 . 99* Variable A XI X2 X3 X4 X 5 X6 X7 X8 X9 X10 XII . XI2 X13 X14

X15 ,20 -,20 ,28 .13 —,28 -.19 -.17 -.37 — .20 -.19 -.29 -.33 -.33 .99* .99*

X16 ,73* ,43 ,46 .33 -.31 -.21 -.19 -.40 -.23 -.20 -.32 -.36 -.36 .00 -.03

XI? ,68* ,20 .53 .34 -.44 -.31 -.27 -.51 -.32 -.29 -.45 -.49 -.50 .68* .65*

Xl8 ,67* .18 .53 .34 -.44 -.31 — ,28 -.50 -.32 -.29 -.45 -.49 -.50 .71* .68*

X19 ,37 ,07 .50 .07 -.36 -.46 -.5 2 -.62* -.68* -.56 -.69* -.73* -.64* .42 .41

X20 ,69* ,04 .94* .84* -.81* -.73* -.67* -.59* -.41 -.58* -.77* -.33 -.85* .41 .41

X21 ,57 ,06 ,88* .99* -.79* -.70* -.61* -.30 -.19 -«48 -.54 .07 -.65* .18 ,18

X22 ,32 ,04 ,40 -.04 -.27 -.35 — .41 -.62* -.62* -.47 -.65* -.76* -.59* .41 .39

X23 ,57 -, 13 ,60 ,30 -.47 -.37 -.34 -.68* -.37 -.31 -,79* -.74* -.82* .52 .51

X24 ,63* -.11 .56 .29 -.49 -.31 -.2 5 -.65* -.2 9 -.20 -.73* -.78* -.80* .48 .47

X25 .-.06 ,65* -.01 -.03 -.17 -.35 -.39 .29 -,4 8 -.42 .44 .18 .40 .00 .00

X26 ,68* .39 ,28 .27 —, 18 -.01 ,06 -.52 .02 .03 .16 -.16 ,04 .32 .30

X2? .51 ,99* .29 .17 -.30 -.39 -.39 -.21 -.52 -.41 .35 — .10 .26 -.18 -.20

X28 ,62* ,11 .86* .73* -.76* -.70* -.65* -.58* -,46 -.59* -.60* -.31 -.68* .73* .73*

X29 ,60* .18 .89* .99* -.81* -.74* -.65* -.30 -.24 -.52 -.47 .09 -.58* .16 .16 VI -p- Variable X15 X16 X17 Xl8 X19 X20 X21 X2 X23 X24 X25 X26 X2? X28 X29

X16 -.03

X17 .66* .73*

X18 .69* .70* .99*

X 19 .39 .35 .51 .51

X20 .40 .47 .62* .6 2 * .55

X21 * 00 .18 .33 .37 .37 .10 - 0

X22 .38 .34 .49 .49 .99* .47 .00 CO CO -3" X23 .49 .52 .71* .71* .8 5 * .77*

X24 .45 .56 .71* .70* .77* .73* .36 .77' ,98* .

X25 .00 — .26 -.16 -.15 — .18 —.30 -.16 -.23 -.53 -.56

X26 .32 .67* .71* .70* -.03 .30 .27 -.03 .25 .31 -.13

X27 -.20 .46 .22 .21 ,.05 .01 .04 .02 -.14 -.12 .63* ,42

X28 .72* .36 .75* .76* .52 .89* .75* .44 .69* .64* -.06 .41 .08

X29 .16 . .35 .38 .38 .07 .85* .99* .03 .32 .31 -.05 .31 .16 .75*

VI Vn Variable

SQ ' BA8 BA10 BA12 BA1 4 BA16 BA18 BA20 BA22 AG16

BA8 -.03 BA10 ,35 .77* BA12 -.02 —.14 -.07 BA14 .67* .34 .67* .24 BA16 ,71* ' .36 .73* ,01 .78* BA18 .37 .70* .76* .18 ,81* ,50 BA20 .64* ,35 ,58* .33 .86* .8 9 * .64* BA22 ' .12 -.46 -.29 .55 ,03 ,22 -,30 ,31. AG16 .66* .45 .78* .24 .98* .81* ,86* ,86* -,03 AG20 .54 .65* . .86* .14 .92* ,82* ,90* ,86* -.09 .96*

^Significant at a = 0,10 level

VI

METRIC CONVERSION TABLE

Centimeters (cm) x 0*393 = Inches

Meters (m) x 3,280 = Feet

Kilometers (km) x 0*621 = Miles (Statute)

Hectares x 2*671 = Acres 2 Square Meters (m ) X 10*764 = Square Feet 3 Cubic Meters (m ) X 35,314 = Cubic Feet

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