Use of Radiotelemetry and GIS to Distinguish Habitat Use Between Graptemys Ouachitensis and G. Geographica in the Scioto River

Use of Radiotelemetry and GIS to Distinguish

Habitat Use Between Graptemys ouachitensis and G. geographica in the Scioto River

A thesis presented to

the faculty of

the College of Arts and Sciences of Ohio University

In partial fulfillment

of the requirements for the degree

Master of Science

Kathleen G. Temple-Miller

August 2008 2

This thesis titled

Use of Radiotelemetry and GIS to Distinguish Habitat Use Between Graptemys

ouachitensis and G. geographica in the Scioto River

KATHLEEN G. TEMPLE-MILLER

has been approved for

the Program of Environmental Studies

and the College of Arts and Sciences by

Willem M. Roosenburg

Assosciate Professor of Biological Sciences

Benjamin M. Ogles

Dean, College of Arts and Sciences

ABSTRACT

TEMPLE-MILLER, KATHLEEN G., M.S., August 2008, Environmental Studies

Use of Radiotelemetry and GIS to Distinguish Habitat Use Between Graptemys

ouachitensis and G. geographica in the Scioto River (57 pp.)

Director of Thesis: Willem M. Roosenburg

A disjunct population of G. ouachitensis co-exists and interacts with G. geographica a more abundant and geographically widespread riverine species. Visual surveys in the spring of 2008 from Commercial Point to Portsmouth, OH (200km), show patchy distribution of G. ouachitensis whereas G. geographica appears more widespread.

G. ouachitensis prefers wider river areas and habitats closer to shallow bars than G. geographica. However, G. geographica prefers habitats closer to tributaries than G. ouachitensis. I monitored both species during 2007 using radiotelemetry in a four-mile river reach by evaluating their habitats and species distribution using quantitative methods in GIS. Results show that G. ouachitensis prefers finer substrate and deeper water than G.geographica and random points. The habitat range examined by the adaptive local convex-hull (LoCoH) method reveals that the two species marginally overlap. Population estimates appear stable but may need monitoring should this environment change in subsequent years.

Approved: ______

Willem M. Roosenburg

Assosciate Professor of Biological Sciences

ACKNOWLEDGMENTS

I sincerely appreciate Dr. Willem Roosenburg’s patience, time, and guidance as my advisor throughout this adventure. I will remember this challenge and its lessons for a lifetime. Thank you to Dr. Matthew White, Dr. Willem Roosenburg, and to ODNR,

Division of Wildlife, for securing funding for this project. My completion would not have been possible without the dedication of my lab partner and friend Ashley Smith. I thank you Ashley for all of your insight in the field and your patience. I have great appreciation for the time and especially the support from my committee members Dr.

Michele Morrone, Dr. Matthew White, and Dr. Jeff Ueland. Additionally I would like to thank Michael Hughes from the Voinovich School of Leadership and Public Affairs for his time and insight into the fluvial components of the project.

I would also like to acknowledge the hard work and enthusiasm from all of the graduate and undergraduate students in this study: Alanna Silva, Leah Graham, Brooks

Kohli, Natalie Boydston, Scott Clark, and Dan Kovar.

I have heartfelt gratitude for my husband Doug Miller, my parents Ken and

Martha Temple, my grandparents Robert and Beulah Temple, and my siblings, Sarah and

Steve Temple for all of their ongoing support, housing, advice, and technical assistance.

Additionally, I would like to honor both sets of grandparents, Winfred and Grace Dumm and Robert and Beulah Temple, for their inspiration and encouragement to pursue a career in science.

TABLE OF CONTENTS

Page

Abstract...... 3

Acknowledgments...... 4

List of Tables ...... 6

List of Figures...... 7

Introduction...... 9

Materials and Methods...... 14

Study site...... 14

Graptemys distribution throughout the lower Scioto River...... 18

Habitat selection among G. geographica and G. ouachitensis...... 18

Results...... 25

Graptemys distribution throughout the lower Scioto River...... 25

Graptemys sp. habitat preference...... 34

Graptemys ouachitensis and G. geographica habitat comparison and partitioning38

Discussion...... 45

Graptemys distribution throughout the lower Scioto River...... 45

Habitat preferences and partitioning...... 46

Future directions ...... 48

Management implications...... 50

References...... 53

LIST OF TABLES

Page

Table 1 Previous Habitat Studies of G. ouachitensis and G. geographica...... 13

Table 2 Summary of Habitat Parameters Included in the Graptemys Survey and the

Graptemys radiotelemetry study on the Scioto River...... 24

Table 3 Spring Survey 2008 Bank Aspect of G. ouachitensis and G. geographica

Locations on the Scioto River...... 44

LIST OF FIGURES

Page

Figure 1 Scioto River watershed including locations of radiotelemetry site and the survey range including Pickaway, Ross, Pike, and Scioto counties...... 16

Figure 2 USGS Land Cover classification of the lower Scioto River Valley...... 17

Figure 3.Spring 2007 visual survey results indicating the Graptemys sp. distribution

throughout the Scioto River from Circleville to Portsmouth, OH...... 26

Figure 4 Fall 2007 visual survey results indicating the Graptemys sp. distribution

throughout the Scioto River from Chillicothe to Portsmouth, OH ...... 27

Figure 5 Spring 2008 visual survey results indicating the distribution of Graptemys

ouachitensis and G. geographica on the Scioto River from Commercial Point to

Circleville, OH...... 28

Figure 6 Spring 2008 visual survey results indicating the distribution of Graptemys

ouachitensis and G. geographica on the Scioto River from Circleville to Chillicothe,

OH...... 29

Figure 7 Spring 2008 visual survey results indicating the distribution of Graptemys

ouachitensis and G. geographica on the Scioto River from Chillicothe to Waverly,

OH...... 30

Figure 8 Spring 2008 visual survey results indicating the distribution of Graptemys

ouachitensis and G. geographica on the Scioto River from Waverly to Lucasville,

OH...... 31

Figure 9 Spring 2008 visual survey results indicating the distribution of Graptemys

ouachitensis and G. geographica on the Scioto River from Lucasville to Portsmouth,

OH...... 32

Figure 10 Spring 2008 Survey Distribution...... 33

Figure 11Radiotelemetry study of Graptemys ouachitensis and G. geographica water

depth on the scioto river, oh...... 35

Figure 12 Radiotelemetry study of Graptemys ouachitensis and G. geographica substrate

preference within the Scioto River, OH...... 36

Figure 13 12 Radiotelemetry habitat study of G. ouachitensis and G. geographica

distance to the nearest alcove/bar on the Scioto River, OH...... 37

Figure 14 Summer and fall 2007 radiotelemetry study of Graptemys range near

Kellenberger Rd., Kingston, OH...... 39

Figure 15 Graptemys core habitat near Kellenberger Rd., Kingston, OH...... 40

Figure 16 Spring 2008 visual survey of G. geographica and G. ouachitensis throughout

the 200km Scioto River study area...... 41

Figure 17 Spring 2008 visual survey of G. geographica and G. ouachitensis throughout

the 200km Scioto River study area ...... 42

Figure 18 Figure 17 Spring 2008 visual survey of G. geographica and G. ouachitensis

throughout the 200km Scioto River study area...... 43

Figure 19 Circular histogram of the spring survey 2008 bank aspect of G. ouachitensis

and G. geographica locations on the Scioto River ...... 44

INTRODUCTION

Characterization of environmental variation, habitat selection, and spatial overlap among species remains a key issue in theoretical and applied ecology and habitat conservation (Caldow and Racey 2000). Sympatric species may exhibit habitat selection by partitioning time or resources (Vogt and Guzman 1988) and high pair-wise resource overlap values in one dimension (e.g. foraging habitat) may be complemented by low overlap values in another dimension (e.g. food) (Schoener 1974). Termed niche complementarity (Schoener 1974), researchers can study these patterns nowwith the high spatial accuracy of GIS (Geographic Information Systems) and GPS (Global Positioning

Systems) (Burrough 1986, Haslett 1990).

Rivers provide human populations with transportation, agriculture, and industry;

consequently, many rivers are modified and their native species affected. Impacts on

riverine habitat include changes in flow regime, water quality, introduction of corridor

barriers, isolation from their flood plain, and the loss of lotic surface area (Gore and Petts

1989). Humans have concentrated in areas that threaten river turtles (Moll and Moll

2004) and degrade their habitat. Seven of the eight endangered or threatened freshwater

turtles and tortoises in the U.S. are riverine (USFWS 2008). These include two species in

the genus Graptemys, G. flavimaculata and G. oculifera. Historically Graptemys are the

fourth most exploited turtle for trade and subsistence in the Mississippi River (Cahn

1937). Exportation, mostly to Asian markets, has risen from 600 Graptemys in 1989 to

200,000 in 2000 (USFWS 2000).

Graptemys habitat is complex requiring many different resources. Adult female

Graptemys migrate to suitable nesting locations (Gibons and Lovich 1990) and seek adult

males for mating (Tuberville et al. 1996). Graptemys move throughout their aquatic

landscapes to pursue seasonally available food sources, migrate to hibernacula, juveniles

migrate from nest sites, and they abandon unsuitable habitats (Ernst et al. 1994). River

turtles use habitat differentially based on size and sex. Since smaller size equates with a

lack in swimming ability in strong currents, smaller turtles usually occupy slower moving

water such as back channels, protected areas, and tributaries (Moll and Moll 2004); while

larger female map turtles move throughout expansive areas within the Mississippi River

(Vogt 1980). Emydid turtle populations correlate with deadwood density demonstrating

the importance of natural riparian areas that provide basking habitat (Lindeman 1999).

Additionally, sand and gravel bars that naturally form by channel movement serve as

vital nesting ground for Graptemys. The nesting period varies regionally but typically

begins in late May and ends by mid-July (Ernst et al. 1994).

One of the greatest factors for Graptemys habitat selection is the river width

(Fuselier and Edds 1994), which correlates with filamentous algae density and basking

site area (Shively and Jackson 1985). Stream width correlated strongest with turtle

density in G. ouachitensis sabinesis in a path analysis study (Shively and Jackson 1985).

Dense algae on logs are a primary food source for G. ouachitensis particularly as turtles

become larger (Shively and Jackson 1985, Moll 1976). Literature explaining the preference of algae species in G. ouachitensis, the Ouachita map turtle, is largely lacking.

Digestive tract examination of Ouachita map turtles revealed primarily vegetation and a few insects, yet the turtles had an attraction to fish, mussels, and crayfish (Moll

1976). This behavior is typical of an opportunistic feeder. The Ouachita map turtle feeds

on the bottom as well as the water surface by protruding the neck and revealing only 1/3

of the shell (Vogt 1981). Smaller turtles contained more insects than larger turtles (Moll

1976), and G. ouachitensis ate by volume: mollusks 2.8%, plant material 31.5%, and insects 51%, and 15% unknown (Vogt 1981). Graptemys geographica, the Northern map turtle, consumed more diverse foods including: freshwater snails, clams, aquatic vegetation, crayfish, water mites, fish, and insects of all stages (Ernst and Barbour 1972).

In the Eastern U.S., Penn (1950) found crayfish made up 24% G. geographica diet.

Since G. ouachitensis has a narrower crushing surface than G. geographica, G.

ouachitensis are restricted from clams or mussels because of the crushing strength required to break mollusk shells (Penn 1950, Ernst and Barbour 1972, Moll 1976, Vogt

1980, Lindeman 2008).

Graptemys geographica are most active between April and late October (Vogt

1980) and their hibernacula structures differ among regions. Graptemys geographica have a diel activity pattern in a northern Indiana lake (Smith and Iverson 2004) but

Ouachita map turtle activity patterns are undocumented and could influence habitat partitioning for one or both species. In Pennsylvania, deep riverine pools are used for hibernacula (Pluto and Bellis 1988), yet in Kentucky impoundments are common hibernacula (Ernst et al 1994). Woodlots have been particularly important for

12 hibernacula to G. geographica in urban landscapes (Ryan et al. 2008). A summary of

Graptemys ouachitensis and G. geographica habitat studies is provided in Table 1.

Table 1 Previous Habitat Studies of G. ouachitensis and G. geographica

Species Habitat Preference Citation

G. ouachitensis Opportunistic feeder (examination of their Moll 1976 digestive tracts) Ouachita map turtle Males, remain in the flowing areas of the river Vogt 1980

Wisconsin by volume: mollusks 2.8%, plant Vogt 1981 material 31.5%, and insects 51%

Total stomach volume contained mostly mayfly Vogt 1981 larvae and caddisfly cases in Arkansas

G. o. sabinesis (subspecies of G.o.) preferred wider areas than common map turtles in Kansas. Shively and -Filamentous algal density and basking site area Jackson 1985 influence density.

G. geographica Crayfish made up 24% of their diet Penn 1950

Northern map Diverse foods including freshwater snails, clams, Ernst and turtle aquatic vegetation, crayfish, water mites, fish, and Barbour 1972 insects of all stages

Mollusks made up 66% of stomach volume and Vogt 1981 were present in 81% of all individuals.

Female G. geographica contained some Ernst et al. 1994 earthworms and large crushed snails

Woodlots preferred for winter hibernacula Ryan et al. 2008

Ouachita map turtles were a subspecies of G. pseudogeographica, the False map turtle, so historical population estimates are lacking (Vogt 1993). Graptemys ouachitensis distribution includes most of the Mississippi River basin (Ernst et al. 1994) whereas G. geographica extends throughout the Great Lakes region (Ernst et al. 1994).

Graptemys ouachitensis and G. geographica occur sympatrically in the lower Scioto

River (Ohio). The populations appear stable despite numerous anthropogenic changes in their environment but detailed population studies are absent.

Map turtle habitat preferences may vary with changing localities because G. ouachitensis is potentially isolated within the Scioto River site, this study may provide new insight to their habitat requirements. I studied G. ouachitensis and G. geographica in the Scioto River using radiotelemetry and remote sensing to understand the distribution, critical habitats, and the sympatry of these two species.

MATERIALS AND METHODS

Study site

I studied spatial habitat partitioning between Graptemys geographica and G. ouachitensis on the Scioto River in Pickaway, Ross, Pike, and Scioto Counties, Ohio

(Figure 1). Almost 85% of the 16900 km2 Scioto River watershed drains agricultural

land (Rabb 2005). Other land cover within the area contains fragments of forested and

urban areas (Figure 2). The Scioto River is an alluvial valley stream containing gravel to

fine sediment glacial substrate. Modification of the southern section below Chillicothe,

Ohio minimizes erosion of agriculture lands, whereas the northerly end, between

Circleville and Columbus, Ohio has coarse gravel and cobble substrate. The Scioto

watershed is a target USDA CREP (Conservation Reserve Enhancement Program) watershed. Initiated in 2005 for a 15-year period, the goal of the project is to increase habitat diversity and reduce sediment load by increasing buffer zones and restoring

wetlands in the riparian zone (Nature Conservancy 2008).

200km Survey Columbus, OH Range

Radiotelemetry Site Kellenberger Rd

Figure 1 Scioto River watershed including locations of radiotelemetry site and the survey range including Pickaway, Ross, Pike, and Scioto counties (Kmusser 2007).

Figure 2 USGS Land Cover classification of the lower Scioto River Valley.

Graptemys distribution throughout the lower Scioto River

I completed three visual surveys: spring 2007, fall 2007, and the spring of 2008.

Surveys on sunny spring and fall days located basking Graptemys and determined distribution throughout the 200km study area. Identification was optimal when traveling downstream at slow speeds (5-7 mph). Optimal basking times for the survey were between 9:00 and 17:00. After identifying turtles to species by facial markings

(Lindeman 1997), I marked the turtle’s position using GPS and recorded basking substrate (log, bank, or rock) and approximate distance from shore. I evaluated large- scale habitat variables and the occurrence of the two Graptemys species using photogrammetry of aerial photography (1m resolution) within ArcView 9.2. I obtained aerial photographs from the Ohio metadata explorer projected in UTM 17N zone. The large-scale habitat layers included surrounding land cover, outer/inner bend of river preference, proximal sand bar distance, river width, sinuosity, distance to nearest tributary, natural vs. channeled areas, and distance to nearest backwater habitat.

Compositional analysis of the land cover layer included a 1km squared area surrounding turtle locations to establish percentage of forested, agricultural, and urban areas using zonal statistics within ArcView Spatial Analyst.

Habitat selection among G. geographica and G. ouachitensis

I measured habitat variables in accordance with the Graptemys distribution observed in the spring 08 surveys and used radiotelemetry to evaluate detailed habitat preferences between the two species. I studied with radiotelemetry a concentration of both Graptemys species on the border between Pickaway and Ross extending 4 km south

and 8 km north of the Kellenberger Bridge (83°0'27 W 39°32'22 N). The study area

included a modified bank section (100m) with concrete blocks, islands, para-fluvial

channels, gravel bars, and varying amounts of riparia.

I captured turtles for radiotelemetry using basking traps, hoop nets, fyke nets, basket traps, and dip nets. I used a variety of bait including cat food, sardines, canned oysters, sweet corn, cream corn, and carrion. I collected all of the telemetry females within a 3.2 km range on the border of Ross and Pickaway counties. Marginal notching

(Cagle 1939) uniquely identified all Graptemys using a 6 mm drill. I also marked turtles with a 125 MHz Passive Integrated Transponder (PIT; Biomark) tag in the right rear leg injected beneath the dermis with a 12-gauge syringe. I recorded turtle mass with a digital scale (4000g x 1g). The plastron length, carapace length, maximum height, and maximum width were measured using Mitutoyo 550 series calipers. Males were

differentiated from females by their anus extending beyond the carapace margin. Age

was determined by counting growth annuli on the hypoplastron.

I studied through radiotelemetry fourteen G. ouachitensis and nine G. geographica (greater than 660g) with SIRTRACK(150 MHZ) waterproof radio transmitters attached to the carapace margin of each turtle. Transmitter attachment was on the carapace above the right hind leg on the 9th and 11th marginals with two bolts and

Gorilla Glue©. Animals were located using triangulation a minimum of three times per week between the hours of 0800 and 1800. I recorded locations with a Garmin GPS unit

(software v. 2.05). ArcView projected the point shapefile from WGS 84 to UTM coordinates on the 1983 North American Datum. Telemetry research can have negative

20 effects in association with the transmitter attachment. However the ‘2% rule’ was used to minimize any adverse impacts on the swimming performance of the turtles as originally determined by fisheries biologists (Cooke and Bunt 2001). Therefore, only female turtles could be included in the radiotelemetry study.

Random points were located throughout the river corridor to quantify the variability near the turtle’s sighting. This is the preferred method to identify the environmental variables influencing selection and habitat preference during fluctuating conditions. ArcMap polygons defined the study for the Hawth’ tools software to create random points for field measurements. Hawth’s tools extension (v. 3.27) within

ArcMap created absence values to measure field variables. I used these absence locations only once for each turtle. The MN DNR Garmin software (v. 5.1.1) uploaded the points to the GPS for field use. After locating each animal, the nearest random waypoints were searched. I traveled to the first point on the GPS within 200-500m to measure a presumed absence location but likely a location within Graptemys home range (Pluto and

Bellis 1988). The collection of all variables occurred at random sites within one hour of locating the turtle to ensure similar field conditions.

Habitat measurement included water depth, presence of filamentous algae, cloud cover, water temperature, and relative substrate size. I measured water depth in the field with a weighted line and used the average of three repetitions. I visually examined the large woody debris and other objects at the surface level for the presence or absence of green filamentous algae. I also recorded cloud cover through a relative estimation of 0-

100%. I recorded water temperature (+ 1°C) with an analog thermometer. Visual

21 estimation of substrate at each site determined relative scores (1(silt)-5(large rock)) between turtle and random locations.

Field collected waypoints are uploaded to a PC via the Minnesota DNR software and were saved as an ARC GIS point shapefile without projection. ArcMap opened the shapefiles and projected the points into the UTM Zone 17N coordinate system. I corrected ground truthed field errors in waypoint locations through the ArcMap editor toolbar.

I measured large-scale habitat preferences through photogrammetry, measurement of aerial photography, through ARC View 9.2 The Ohio Metadata Explorer obtained the NAIP 2004 (1m X 1m) ortho-photography of each county (Pickaway, Ross, Pike, and

Scioto). ArcMap Spatial Analyst tools using the Digital Elevation Models of the inclusive counties (10m DEM, Ohio Metadata Explorer) determined the proximal riverbank aspect of each turtle location. The ortho-imagery and the DEM files were all mosaic together (ArcMap Spatial Analyst Tools) to eliminate gaps in analysis of the files.

The USGS seamless data website provided National Land Cover Data.

Relevant turtle habitat variables were digitized through photogrammetry of ortho- photography files: distance to nearest tributary, distance to nearest oxbow/scour, sinuosity, distance to nearest sand bar, and river width (Table 2). I measured these variables in map units of meters in a 1:3,000 m extent using the editor toolbar. The trace tool on the editor toolbar measured the paths between locations by following the thalweg, or valley line, of the river channel. I created a line-shapefile of the river thalweg, by interpreting the slope of the valley created through ArcMap Spatial Analyst tools and the

ortho-photography files. Hawth’s tools determined sinuosity from the input of the river

thalweg within a 500m buffer surrounding each point. Hawth’s tools divided this line

(arc), by the distance between the start and finish locations. Comparison of turtle vs. random habitat locations determines habitat selection.

I analyzed habitat parameters with nonparametric Kruskal-Wallis One-Way

ANOVA on ranks since all variables violated assumptions of normality and equal variances. I used NCSS (Hintze 2006) statistical software. Comparison of each variable against species and random points grouped all individuals by species because some

turtles were located more often than others. I also examined Kruskal-Wallis Multiple-

Comparison Z-Value Test (Dunn's Test) for comparison of both species and the random

site habitat variable differences. Circular statistics within NCSS examined the aspect

direction of each turtle position through the Von Mises statistical procedure (unimodal

and symmetric distribution, direction, and concentration).

This study refers to the home range as the area used in the normal daily activities

of a turtle and excludes seasonal migrations (Moll and Legler 1971). Time spent within

the study area was compared at the species level using the adaptive localized convex hull

(LoCoh) method through the web interface: http://locoh.cnr.berkeley.edu (Getz et al.

2007). This study followed “the rule of thumb” recommendations given within the

LoCoh software (Getz et al. 2007). The adaptive LoCoh method is described as “an

adaptive sphere of influence,” which seeks to build kernels from all points within a radius

(alpha) such that the distances of all points within the radius to the reference point sum to

a value less than or equal to alpha. This study found the value of alpha by incorporating

as many points as possible but minimizing the area outside the riverbanks. Another variable “k” represents a nearest neighbor score. This score equals the square root of the

number of waypoints in the shapefile. LoCoh software analyzed turtles by species level

and incorporated their positions into ArcView shapefiles containing distribution values. I

overlapped these files to produce one map of both species to show differences of time spent within the river corridor. Identification of the core habitat at the 50% isopleths

minimized error from exploratory movement and identified the most critical habitats for

the two species (Börger 2006).

Table 2 Summary of Habitat Parameters Included in the Graptemys Survey and radiotelemetry study on the Scioto River

Habitat Layers Data Source Survey Radiotelemetry

River Width Ortho x x

Filamentous algae presence Field x

Relative Cloud Cover Field x

Land Cover USGS x

Substrate Field x

Water Temperature Field x

Sinuosity pattern Ortho x x

Distance to Nearest Tributary Ortho x x

Distance to Backwater habitat Ortho x x

Air Temperature NOAA x

Precipitation NOAA x

Nearest Sand Bar Ortho x x

Flow Rate NOAA x

Outer-bend occurrence Ortho x

Aspect DEM x

RESULTS

Graptemys distribution throughout the lower Scioto River

Rapidly fluctuating water levels and basking behavior limited survey times to spring and fall. The spring 2007 survey helped to determine areas of habitat diversity and

Graptemys concentrations for the radiotelemetry study at Kellenberger Road (Figure 3), while the preliminary fall 2007 survey revealed relative distribution of both species

(Figure 4). The spring 2008 survey observed 967 Graptemys basking on the logs and the banks of the Scioto. The survey identified 370 G. geographica, 229 G. ouachitensis and

368 were identified as Graptemys sp (Figures 5, 6, 7, 8, 9). The most northern half of the study from Commercial point to Chillicothe had a species level identification rate of

62%, whereas the southern section from Chillicothe to Portsmouth had a success rate of only 53%.

Graptemys ouachitensis was unconfirmed in the most northern 17 km stretch of the survey. The 50% isopleths levels reveal the clumping of G. ouachitensis (Figure 10).

The three polygons representing the 50% isopleths of G. ouachitensis are near the villages of Kingston (radiotelemetry site), extend from Higby to Waverly, and Lucasville,

OH. The gaps in the G. ouachitensis 50% isopleths represent low densities whereas the red polygons represent areas of highest densities. The fall 2007 survey also shows a clump of Ouachita map turtles between Higby and Waverly.

Graptemys geographica distribution was widespread throughout the surveyed portion of the Scioto in the fall 2007 (Figure 4) and the spring of 2008 (Figure 5, 6, 7, 8,

9). The 50% isopleths also reveal a uniform distribution throughout the survey range with the exception of only a small area just south of Deer Creek.

Figure 3 Spring 2007 visual survey results indicating the Graptemys sp. distribution throughout the Scioto River from Circleville to Portsmouth, OH (Graptemys ouachitensis, G.o.; G. geographica, G.g.).

Figure 4 Fall 2007 visual survey results indicating the Graptemys sp. distribution throughout the Scioto River from Chillicothe to Portsmouth, OH.

Figure 5 Spring 2008 visual survey results indicating the distribution of Graptemys ouachitensis and G. geographica on the Scioto River from Commercial Point to Circleville, OH.

Figure 6 Spring 2008 visual survey results indicating the distribution of Graptemys ouachitensis and G. geographica on the Scioto River from Circleville to Chillicothe, OH.

Figure 7 Spring 2008 visual survey results indicating the distribution of Graptemys ouachitensis and G. geographica on the Scioto River from Chillicothe to Waverly, OH.

Figure 8 Spring 2008 visual survey results indicating the distribution of Graptemys ouachitensis and G. geographica on the Scioto River from Waverly to Lucasville, OH.

Figure 9 Spring 2008 visual survey results indicating the distribution of Graptemys ouachitensis and G. geographica on the Scioto River from Lucasville to Portsmouth, OH.

Figure 10 Spring 2008 survey distribution. Examination of the 50% Localized Convex Hull Isopleths reveal distribution clumps of G. ouachitensis and widespread distribution of G. geographica.

Graptemys sp. habitat preference

I evaluated summer and fall G. ouachitensis habitat use through 147 radiotelemetry derived positions from July through October 2007. No differences among individuals were found for any of the habitat variables evaluated (Kruskal-Wallis

ANOVA, p>.05). Fourteen G. ouachitensis individuals comprised the habitat associations with paired random points. I found Ouachita map turtles in areas with deeper water (Figure 11, Dunn’s test, Z= 3.342,466, p<.05) and more clay silt sediment (Figure

12, Dunn’s test, Z= 5.372,466, p<.05) than random points. Graptemys ouachitensis median

weights captured for this radiotelemetry study are 300g larger than G. geographica

(Kruskal Wallis ANOVA, Z= 8.23831, 22, p<.001). Graptemys ouachitensis did not show

any preference over random sites for many habitat variables: distance to alcoves/bars,

water temperature, sinuosity, filamentous algae, or distance to tributaries.

The radiotelemetry study of nine Northern map turtles identified habitat occupied

85 times from July through October 2007. No differences among individuals were found

for any of the habitat variables evaluated (Kruskal-Wallis ANOVA, p>.05). In this

region, G. geographica preferred habitats closer to alcoves/shallow bars than random sites (Figure 13, Kruskal-Wallis ANOVA, Z= 2.012,466, p<.05). Northern map turtles did

not show preference from random sites for many habitat variables: sediment, river width,

sinuosity, water temperature, filamentous algae or distance to tributaries.

155.0

146.3

137.5

128.8 Depth (cm)

120.0 G.g. G.o. Random

Location

Figure 11 Radiotelemetry habitat study of G. ouachitensis and G. geographica water depth on the Scioto River, OH. Graptemys ouachitensis prefers deeper water than random (Dunn’s test, Z= 3.342,466, p<.05) and G. geographica (Dunn’s test, Z= 3.082,466, p<.05).

120.0

G.g.b G.o.a. b 80.0 Random

Count 40.0

0.0 1.0 2.0 3.0 4.0 5.0

Substrate

Figure 12 Radiotelemetry study of G. ouachitensis and G. geographica substrate preference within the Scioto River, OH. G. ouachitensis is different from random sites (Dunn’s test, Z=5.372,466, p<.05) and G. geographica (Dunn’s test, Z= 2.662,466, p<.05). Substrate descriptions: clay silt, 1; sand, 2; gravel, 3; cobble, 4; cinder block or similar size, 5. Superscript letters differentiate significance; different letters have significant differences.

380.0

345.0

310.0

275.0 Distance (m)

240.0 G.g. G.o. Random

Species

Figure 13 Radiotelemetry habitat study of G. ouachitensis and G. geographica bar distance on the Scioto River, OH. Graptemys geographica are closer to bars than G. ouachitensis (Dunn’s test, Z=3.032,466, p<.05) and random sites (Dunn’s test, Z= 2.012,466, p<.05).

Graptemys ouachitensis and G. geographica habitat comparison and partitioning

In the area of the telemetry study, the Ouachita map turtle preferred deeper water

(Figure 11, Dunn’s test Z=3.082,466, p<.05) and finer substrates (Figure 12, Dunn’s test,

Z=2.662,466, p<.05) than G. geographica. Graptemys geographica preferred habitats

closer to alcoves/bars than G. ouachitensis (Figure 13, Dunn’s test, Z= 3.032,466, p<.05).

The local convex hulls (Figure 14) describe the range and the relative time spent

throughout the region. Both species spatial distribution within the telemetry region

overlap marginally (~25%) (Figure15). The species did not show differences in distance moved between radiotelemetry events. This margin of overlap is comparable to the two species dietary partitioning of 21% through Morisita’s index in the Mississippi River near

Wisconsin (Vogt 1981).

In the spring 2008 survey, the Ouachita map turtle preferred wider areas of the river (Figure 16, Kruskal Wallis ANOVA, Z= 7.891, 598, p <0.001) and habitats closer to shallow bars over the Northern map turtle (Figure 17, Kruskal Wallis ANOVA, Z=

3.191,598, p< 0.003). Additionally, the Northern map turtle preferred spring habitats

closer to tributaries than the Ouachita map turtle (Figure 18, Kruskal Wallis ANOVA,

Z=2.331,598, p< 0.02). However, there were no differences in habitat near urban,

forested, or agriculture land. The mean bank aspect of each turtle and the distributions of G. ouachitensis and G. geographica are different however, the concentrations of which

bank they prefer are not different (Figure 21, Table 2).

Figure 14 Summer and fall 2007 radiotelemetry study of Graptemys range near Kellenberger Rd., Kingston, OH. Fourteen G. ouachitensis and nine G. geographica comprise the 100% isopleths.

Figure 15 Graptemys core habitat near Kellenberger Rd., Kingston, OH. The 50% isopleths of summer and fall 2007 radiotelemetry study of fourteen G. ouachitensis and nine G. geographica reveal the core habitat and partitioning of a small Graptemys population in the Scioto River, OH.

Figure 16 Spring 2008 visual survey of G. geographica and G. ouachitensis throughout the 200km Scioto River study area. Graptemys ouachitensis prefers wider river areas than G. geographica (Kruskal Wallis ANOVA, Z= 7.89551,598, p <0.001). Means G.g. 66.0, G.o. 80.9). Bars represent 1.0 SE.

Figure 17 Spring 2008 visual survey of G. geographica and G. ouachitensis throughout the 200km Scioto River study area. Graptemys ouachitensis prefers habitats closer to shallow bars/alcoves than G. geographica (Kruskal-Wallis ANOVA, Z= 3.19531,598, p< 0.003, Means G.g. 619m, G.o. 425m). Bars represent 1.0 SE.

Figure 18 Spring 2008 visual survey of G. geographica and G. ouachitensis throughout the 200km Scioto River study area. Graptemys geographica prefers habitats closer to tributaries than G. ouachitensis (Kruskal Wallis ANOVA, Z=2.33471,598, p< 0.02, Means: G.g 543m, G.o. 779m). Bars represent 1.0 SE.

Table 3 Spring Survey 2008 Bank Aspect of G. ouachitensis and G. geographica Locations on the Scioto River.

Null Hypothesis Test Test Stats Prob Name Statistic Level Equal Distributions Uniform Scores Test 13.352 0.001 Equal Directions Watson-Williams F Test 20.436 0.000 Equal Concentrations Concentration Homogeneity Test 1.012 0.314

LEGEND G.g.

0 G.o.

33.0

16.5

16.5 33.0 90 270 33.0 16.5

16.5

33.0

180

Figure 19 Circular histogram of the spring survey 2008 bank aspect of G. ouachitensis and G. geographica locations on the Scioto River. Distribution and direction of G. ouachitensis and G. geographica differ (G. ouachitensis 179.5°, G. geographica 138.9°, 598 degrees of freedom, p<.05).

DISCUSSION

Graptemys ouachitensis and G. geographica have different habitat preferences in

Ohio’s Scioto River. Graptemys ouachitensis prefers deeper habitats with finer

substrates while G. geographica prefer areas closer to bars and alcoves. These

differences in habitat use result in a clumped distribution of the Ouachita map turtle while

the Northern map turtle has a uniform distribution.

Graptemys distribution throughout the lower Scioto River

G. ouachitensis extends from Circleville to Portsmouth but most individuals are in clusters near Kingston, Waverly, and Lucasville, OH. Distribution maps have presumed the population to be disjunct for many years (Ernst et al. 1994). Smith (2008) suggested that G. ouachitensis likely had several dispersal events and the possibility that a population extended throughout the Ohio River Valley at one time. G. geographica had a wide distribution from Commercial Point to Portsmouth, OH, throughout the fall 2007 and spring 2008 surveys. Unlike G. ouachitensis, G. geographica extend throughout the

Ohio River valley (Ernst et al 1994). Graptemys ouachitensis prefers sandy beaches for nesting (Moll and Moll, 2004) and may not be in the most northern region during the

2008 spring survey because females have not laid their first clutch. However, G. geographica prefers gravel substrate for nesting (Moll and Moll 2004) but has been known to nest in sandy beaches (Ernst et al. 1994) so their distribution below Lucasville,

OH is unexpected where the coarse substrates diminish.

The spring 2008 survey spanned a moderate flood event after the first two days that subsequently increased the water temperature 4 degrees Celsius for the southern

survey period. This increase in temperature influenced the amount of time turtles would

bask in the presence of an oncoming intruder. In colder temperatures (16-17ºC),

Graptemys sp. would allow an observer to be within 10 m as opposed to warmer

temperatures that caused some to dive at distances of 100-130m. The most southern

portion of the survey from Chillicothe to Portsmouth had the lowest success rate of

differentiating species but two of the three G. ouachitensis patches are within this region.

Therefore, G. ouachitensis may be more widespread in this lower portion than surveys

have demonstrated. Survey success is directly dependent on observers, watercraft

operation, superior binoculars, and consistent weather patterns.

Habitat preferences and partitioning

Extreme megacephly and tomium strength differences (Lindeman 2000) likely

contributes to diet variations in Graptemys species (Vogt 1980, Moll 1976, Ernst and

Barbour 1972). Diet variations lead to differences in water depth and substrate between

G. ouachitensis and G. geographica. Graptemys ouachitensis prefers fine silt substrates,

and often occupy laterally scoured pools and eddy drop zones that carry high numbers of

macroinvertebrates and other organisms for the opportunistic feeder. The silt substrate

preference also explains why G. ouachitensis preferred deeper water due to the energy in

these areas during high flows. When the flows are low and the eddy drop zones are not

carrying high numbers of macroinvertebrates, these areas often contain basking logs that provide large insect communities upon observation for surface feeding (Vogt 1981).

High flows in this study created discontinuity to the growth of filamentous algae.

Radiotelemetry did not reveal habitat preference but filamentous algae may be an

intermittent food source (Shively and Jackson 1985, Moll 1976). However, G. geographica preferred gravel and cobble near bars and alcoves. These bars contain coarse substrates that yield a diversity of mussels (OSU 2008) and provide habitat for macroinvertebrates. I was unable to detect an effect of other geological factors such as proximity to tributaries, inner/outer bend preference, or modified areas of the river perhaps because my radiotelemetry work only occurred in a small section of the river.

The spring survey in April revealed slightly different habitat preferences from the radiotelemetry study concerning distances to nearest tributary and bars between the two species. Perhaps these differences are due to discrepancies in male and female foraging and reproduction. Females do not usually forage until laying their first clutch in May and move toward the nesting beaches while it is unknown when males begin to forage (Vogt

1980). The earliest documented feeding by Wisconsin female G. ouachitensis was May

30 while G. geographica began feeding May 26 (Vogt 1980). There are many hypotheses for delayed female foraging including: limited gut cavity space until the female lays the first clutch, macroinvertebrates are in short supply, or temperatures are not high enough to allow digestion (Vogt 1980). These are potential contribution factors explaining why G. ouachitensis was near bar habitat in April and not during the summer and fall radiotelemetry study. Unfortunately, shallow bars spatially correlate with alcoves and thus preference for bars cannot determine whether G. ouachitensis prefers backwater alcoves, nesting beaches in the spring, or foraging habitat.

Bank aspect provides information about habitat selection for basking but also avoidance of wind. Both species prefer mostly southern facing banks for optimal

basking. However, G. geographica preferred a more southeast facing bank, which could aide in avoiding prevailing western wind patterns.

Telemetry results show that the two species core habitats overlap by about 25%,

but most of their range is discrete upon examining the 50% isopleths. A study including

G. pseudogeographica, G. ouachitensis, and G. geographica in the Mississippi River near Wisconsin found food partitioning in all three species but only 21% niche overlap between G. geographica and G. ouachitensis (Vogt 1981). In the same study, G.

ouachitensis was a very successful opportunistic feeder comprising 66% of the total

Graptemys population (Vogt 1981). I hypothesize this overlap in the radiotelemetry

study is due to changing fluvial differences of the habitat that prompted variation in

resources rather than partitioning due to competition.

Future directions

No reports of G. pseudogeographica have been documented within this study

but head markings of G. ouachitensis and the False map turtle are very similar. The

closest documented population of the False map turtle is within the headwaters of the

Scioto River, in Logan, Union, and Hardin counties of Ohio (Ernst et al. 1994). Future studies on the Scioto River could incorporate extended surveys throughout the entire river with telescopic-lens digital photography. Superior optics and at least 10-mega pixel

resolution would be required to verify if a third species is contributing to the Scioto River habitat partitioning. However, Smith (2008) suggests that head markings may not be

reliable in distinguishing between G. ouachitensis and G. pseudogeographica as several

identified museum specimens of G. ouachitensis were mistakenly identified as G. pseudogeographica. Detailed molecular work is necessary to study these populations.

As river conditions change, enhanced GPS trackers with radio receiver technology could give greater understanding of turtle activity patterns, seasonal habitat requirements, information regarding the number of clutches per year, in addition to the habitat variables discussed within this study. GPS trackers have the capability to gather tremendous data points without time of day biases and recent technology has made this

equipment smaller and has extended battery life.

In the future, incorporating remote sensing into ecological studies will save time,

money, and may replace many labor-intensive measurements in the field. Lidar (light

detection and ranging) remote sensing has the capability to characterize the 3-D habitat structure in fine detail and across broad ranges. The potential for improved watershed- extent mapping is even larger when lidar combines with optical imagery through satellites. River imaging with lidar will lend high spatial resolution of the water surface elevations (Schumann et al. 2007) and could potentially give raw data required to

calculate slope remotely. Lidar could also incorporate sediment composition, roughness

profiles, and variations in flow dynamics to build enhanced habitat models. Continuous

data available to land managers and researchers alike would provide beneficial elements for the important monitoring of our streams and rivers in the face of changing land uses due to agricultural, urban development, and deforestation.

Continuing studies of the Graptemys population near the telemetry region could

examine sex ratios and the age class distribution to suggest the stability of the population.

Additional survey work throughout the Scioto River could explain more about seasonal

preferences and critical habitats for nest laying, foraging, and hibernacula selection.

Surveys throughout the summer would be beneficial for determining foraging habitats but

need replication considering the low basking rates in comparison to spring and fall

surveys.

Management implications

The greatest threats for map turtles today are by-catch and tangling in nets of commercial fisheries, human consumption (NatureServe 2003), collection for the pet trade (Dundee and Rossman 1989), and habitat destruction (Ernst et al. 1994). In the

Scioto River, the greatest threat may become habitat alteration of nesting, foraging, and typical basking behavior (on logs) caused by changes in the river flow regime. The flood-pulse concept illustrates how flooding events are responsible for establishing diversity within rivers by creating backwater habitats such as scours, sloughs, oxbows, sandbars, and the distribution of large woody debris (Junk et al. 1989). These backwater areas potentially create habitat for larval insect, arthropod, mussel, and ultimately aquatic turtle communities. Should flood and drought patterns change the flow and sediment distribution, habitat may suffer alteration. Large woody debris recruitment through scouring of banks may be difficult in low flow while high flows may flood basking habitat outside of the channel or further downstream. Riparian areas are also essential to

G. geographica for winter hibernacula (Ryan et al 2008) and probably likewise for G. ouachitensis. Map turtles could be great ecological indicators of these flow regime changes especially in the rarely studied and dynamic Scioto River ecosystem.

Determining how changes in flow impact the habitat partitioning and distribution of

Graptemys sp. in the Scioto River may be crucial to their long-term conservation and could serve as indicators to the health of macroinvertebrate and mussel communities.

Variances in discharge (volume of water/minute) can change the typical home range for aquatic species. There are no studies of riverine turtles but there are many examples of fish that change habitat use and preference with changes in flow conditions

(e.g. Pert and Erman 1994, Bunt et al. 1999, Scruton et al. 2003). Fish ranges change with associated variables such as depth, velocity, shear stress, and substrate with changes in flow (Bovee 1982). Perhaps aquatic turtles have similar responses to changes in the flow. Additional studies should monitor water velocity to determine local turbulence and its impact on home ranges in diverse conditions.

Although populations seem stable, flow in the Scioto River may become flashy as many rivers across the U.S. experience the first signs of global warming. These changes could spark extreme precipitation events with increasing amounts of atmospheric water vapor and destabilization of the atmosphere resulting in a greater frequency of short-term

“flash” floods (Kunkel 2003). Flashy conditions could alter the flow of organic matter, large woody debris, and change the biogeomorhology of the river that could change rates of erosion, sedimentation, and the flow of organic particulates. The upstream dams create a more interesting dynamic in severe conditions of drought and flood events.

Within the summer of 2007, the Scioto River has seen two of the five lowest water

records kept on web record (NOAA, 2008). In 2008, the river crested to historical levels;

two of the twenty crest events on web record were also within the last year (NOAA,

2008). Programs that attempt to restore agricultural land in close proximity of the river such as the Scioto Conservation Reserve Enhancement Program will become increasingly important to minimize runoff and erosion should flood events continue to rise. Future riverine studies should monitor the changing landscape on a broad scale to develop a better understanding of fluvial and ecological interactions. Understanding how species interact in changing environmental conditions will continue to be an important concern for ecologists worldwide.

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