New publication on Timber Rattlesnake movement

PACeLab PhD Candidate Andrew Jesper co-authored a new paper with his undergrad research advisor Scott Eckert at Principia College. Jesper and Eckert radio-tracked 29 individual Crotalus horridus (13 female, 16 male) in Jersey County, Illinois.

On average, males move greater daily distances and occupy larger home ranges than females, particularly during the summer when Timber Rattlesnakes find mates. Females dispersed shorter distances from their hibernacula than males. Several snakes were tracked over multiple years, and returned to their same general range each summer. This site fidelity may limit the success of translocating adult individuals.




Understanding the home range of imperiled reptiles is important to the design of conservation and recovery efforts. Despite numerous home range studies for the Threatened timber rattlesnake (Crotalus horridus), many have limited sample sizes or outdated analytical methods and only a single study has been undertaken in the central midwestern United States. We report on the home range size, site fidelity, and movements of C. horridus in west-central Illinois. Using VHF telemetry, we located 29 C. horridus (13 female, 16 male) over a 5-year period for a total of 51 annual records of the species’ locations and movements. We calculated annual home ranges for each snake per year using 99%, 95%, and 50% isopleths derived from Brownian Bridge utilization distributions (BBMM), and we also report 100% minimum convex polygons to be consistent with older studies. We examined the effects of sex, mass, SVL, and year on home range sizes and reported on movement metrics as well as home range fidelity using both Utilization Distribution Overlap Index (UDOI) and Bhattacharyya’s affinity (BA) statistics. The home range sizes for male and non-gravid C. horridus were 88.72 Ha (CI 63.41–110.03) and 28.06 Ha (CI 17.17–38.96) for 99% BBMM; 55.65 Ha (CI 39.36–71.93) and 17.98 (CI 10.69–25.28) for 95% BBMM; 7.36 Ha (CI 5.08–9.64) and 2.06 Ha (CI 1.26–2.87) for 50% BBMM; and 78.54Ha (CI 47.78–109.30) and 27.96 Ha (CI 7.41–48.51) for MCP. The estimated daily distance traveled was significantly greater for males (mean = 57.25 m/day, CI 49.06–65.43) than females (mean = 27.55 m/day, CI 18.99–36.12), particularly during the summer mating season. Similarly, maximum displacement distances (i.e., maximum straight-line distance) from hibernacula were significantly greater for males (mean = 2.03 km, CI 1.57–2.48) than females (mean = 1.29 km, CI 0.85–1.73], and on average, males were located further from their hibernacula throughout the entirety of their active season. We calculated fidelity to high-use areas using 11 snakes that were tracked over multiple years. The mean BBMM overlap using Bhattacharyya’s affinity (BA) for all snakes at the 99%, 95%, and 50% isopleths was 0.48 (CI 0.40–0.57), 0.40 (0.32–0.49), and 0.07 (0.05–0.10), respectively. The mean BBMM overlap for all snakes using the Utilization Distribution Overlap Index (UDOI) at the 99%, 95%, and 50% isopleths was 0.64 (CI 0.49–0.77), 0.32 (CI 0.21–0.47), and 0.02 (CI 0.01–0.05)), respectively. Our results are largely consistent with those of other studies in terms of the influence of sex on home range size and movements. The species also exhibits strong site fidelity with snakes generally using the same areas each summer, though there is far less overlap in specific (e.g., 50% UDOI) high-use areas, suggesting some plasticity in hunting areas. Particularly interesting was the tendency for snakes to disperse from specific hibernacula in the same general direction to the same general areas. We propose some possible reasons for this dispersal pattern.

Read the full article: Eckert, S.A., Jesper, A.C. Home range, site fidelity, and movements of timber rattlesnakes (Crotalus horridus) in west-central Illinois. Anim Biotelemetry 12, 1 (2024).


New paper analyzing long term data on Ornate Box Turtle survival

box turtle
Ornate Box Turtle Photo by D. Edmonds

PaCE Lab doctoral candidate Devin Edmonds has a new paper in the journal Wildlife Biology: “Evaluating Population Persistence of Ornate Box Turtles (Terrapene ornata) at the Northeast Edge of their Distribution.”

This work analyzed 34 years of data from one site and 8 years of data from another to estimate female and juvenile survival and population growth over time. Being able to look at a population over a long period of time provides a better understanding of the population. This study also highlighted the need to protect adult female Ornate Box Turtles if the populations are to persist.

This work was co-authored with members of the Wildlife Epidemiology Lab.


Abstract: Turtles and tortoises are among the most threatened vertebrate groups. Their life history is characterized by delayed sexual maturity and a long lifespan, making populations susceptible to decline following perturbations. Despite the urgent conservation need, we are missing estimates of basic demographic traits for many species and populations. The ornate box turtle (Terrapene ornata) is a species lacking crucial demographic data. Many populations are isolated in fragmented habitats, especially in the eastern portion of their range. We carried out long-term capture-mark-recapture surveys on two isolated populations in northern Illinois to estimate population vital rates and project population persistence with deterministic stage-based matrix models. Using 34 years of data, we estimated adult female survival = 0.974 (95% CI: 0.946–0.988) and juvenile survival = 0.867 (95% CI: 0.688–0.951) at our most intensively surveyed site. At a second site using 8 years of data, we estimated adult female survival = 0.897 (95% CI: 0.783–0.954) and juvenile survival = 0.844 (95% CI: 0.551–0.960). Despite seemingly high annual survival rates, populations declined under population projections using mean vital rates. Population growth was most sensitive to adult survival, with increasing sensitivity under more pessimistic scenarios. Our results highlight the importance of long-term demographic studies for threatened species and demonstrate protecting adult female ornate box turtles is critical for ensuring populations persist at the northern edge of their distribution.

Read the full paper:

New paper on more efficiently detecting Kirtland’s Snake

kirtland's snake
Kirtland’s Snake

Recent PaCE Lab graduate Tyler Stewart published a paper on his M.Sc. work creating a species distribution model for the rare and cryptic Kirtland’s Snake, Clonophis kirtlandii. He found that surveys Mid-May to early July when there was high cloud cover, moderate air temperature, and low relative humidity enhanced the detection probability of this species.



Snakes are difficult to study due to their cryptic coloration, minimal movements, and use of inaccessible habitats. Although well‐timed surveys during a species’ active season can result in higher detection rates and conserve survey resources (i.e., time and money), survey effort may not ensure the detection of rare and cryptic species. Thus, in such instances, a strategic species‐ specific sampling design is needed. The Kirtland’s snake (Clonophis kirtlandii) is a rare, cryptic species assumed to be experiencing range‐wide declines. Naturalists have noted the disappearance of Kirtland’s snakes from various habitats since the early 1970s. The primary objective of our study was to determine detection of Kirtland’s snakes and the environmental and temporal factors influencing detection. We calculated the effort needed to detect individuals at sites by estimating detection probabilities of 3 known Kirtland’s snake populations in Illinois from 2019 to 2021. Based on 77 Kirtland’s snake detections over 226 site visits (34.1%) across 3 study sites, we found that high cloud cover, moderate air temperature, and low relative humidity enhanced the detection probability of this species. The middle of May to the beginning of July was the best time to conduct surveys when detection rates were highest. As our results suggested, it is imperative to establish strategic monitoring programs maximizing conservation resources to document populations for conservation action and range shifts for species of conservation concern, such as Kirtland’s snakes.

Stewart, T. A., A.R. Kuhns, C.A. Phillips, J.A. Crawford, and M.J. Dreslik.  2023. Estimating the effort required to detect Kirtland’s snakes (Clonophis kirtlandii). Wildlife Society Bulletin.

New paper on Baron’s mantella frog, co-authored by Devin Edmonds

frog on moss
Mantella baroni photo by Devin Edmonds

INHS PaCE Lab PhD candidate Devin Edmonds co-authored a recent paper on habitat features of Baron’s Mantella Frog. Tantely Rasoarimanana (Université d’Antananarivo) and Olivier Marquis (Paris Zoo) led the collaboration with the NGO Man and the Environment. The study aimed to identify what microhabitat features explain the presence of Baron’s mantella frog (Mantella baroni) and also estimate their population sizes in Vohimana Reserve, eastern Madagascar. We found that leaf litter depth and the number of small trees in a quadrat were important habitat features; deeper leaf litter and fewer small trees explained if M. baroni was present.

New paper on timing prescribed fires to avoid Ornate Box Turtle mortality

Ornate Box Turtle photo by D. Edmonds

PhD candidate Devin Edmonds is lead author on a paper published this week in Journal of Wildlife Management. Recognizing the importance of fire for prairie management, Edmonds et al. examined the behavior and physiology of Ornate Box Turtles to predict when turtles would be underground, sheltered from fire.



Fire is a vital management tool for maintaining prairie ecosystems. Prescribed burns control invasive species, regulate succession, stimulate plant growth, and are a cheap and effective method for removing excess biomass; however, fire can also inadvertently cause wildlife mortality, placing land managers in a challenging situation. Turtles are especially at risk of mortality from fire because of their low mobility and population sensitivity to reductions in adult survival. We studied ornate box turtles (Terrapene ornata) at 3 sites in Illinois, USA, from 2019–2022 to determine the best predictors of above-ground activity so land managers can conduct prescribed burns when turtles are underground. We used turtle shell temperature, air temperature, soil temperature, and precipitation data to develop a predictive model of above-ground activity. The best model for predicting above-ground activity included an interaction between day of year and current air temperature. Earlier in spring and later in fall, above-ground activity is more likely at higher air temperatures compared to later in spring and earlier in fall when the same likelihood of above-ground activity is predicted at lower air temperatures. In spring, we recommend burning in Illinois ornate box turtle habitat before 1 April when air temperature is <10°C and in fall after 1 November when air temperature is <15°C. Above these temperature thresholds, there is a >5% likelihood that turtles in northern populations are above ground.

Read the full paper:

Edmonds, D. A., Bach, E. M., Colton, A. L., Jaquet, I. S., Kessler, E. J., and Dreslik, M. J.. 2023. Avoiding mortality: timing prescribed burns in ornate box turtle habitat. Journal of Wildlife Management e22510.

Read more from Elizabeth Bach and Devin Edmonds on the Grassland Restoration Network blog: Ornate box turtle emergence


New paper on Alligator Snapping Turtle movement by ARC program leader Ethan Kessler

Translocated Alligator Snapping Turtle with radio transmitter attached

A paper just out this week  in the Journal of Wildlife Management, “Movement behavior and passive dispersal of a reintroduced population of alligator snapping turtles” found that translocated AST behaved similarly to wild populations, and is largely passive. This can have conservation implications as reintroduced animals may be transported downstream by high flows.



Maladaptive movement behavior is a leading cause of failure for reptile reintroductions, thus characterizing movement for translocated populations is important to project success. From 2014–2016 we radio-tracked 183 immature reintroduced alligator snapping turtles (Macrochelys temminckii) using very high frequency telemetry in a stream in southern Illinois, USA. We assessed environmental, temporal, morphometric, and microhabitat factors influencing movement, including post-release dispersal from reintroduction sites, movement probability, and step length. We used directional statistics to investigate the effects of precipitation and age on directional movement in the stream. Numerous factors influenced active movement, including ambient temperatures, time since release, use of log jams, turtle size, and age. Precipitation had an age-biased effect on movement. Directional analyses suggested that movement was largely passive as turtles were swept downstream with increased discharge. Overall, the behavior of reintroduced alligator snapping turtles was similar to that reported in wild populations. Passive downstream transport has implications for reintroduced and natural populations as a force for unintentional emigration in channelized streams under current conditions and future high flow regimes.

Read the full paper here.

Kessler, Ethan J. and Michael J. Dreslik. 2023. Movement behavior and passive dispersal of a reintroduced population of alligator snapping turtles. Journal of Wildlife Management.

New Timber Rattlesnake publication by PhD candidate Andrew Jesper

Trailcam image of Timber Rattlesnake at den opening

Abstract: Many temperate reptiles survive winter by using subterranean refugia until external conditions become suitable for activity. Determining when to emerge from refugia relies on the ability to interpret when above-ground environmental conditions are survivable. If temperate reptiles rely on specific environmental cues such as temperature to initiate emergence, we should expect emergence phenologies to be predictable using local climatic data. However, specific predictors of emergence for many temperate reptiles, including the Timber Rattlesnake (Crotalus horridus), remain unclear, limiting our understanding of their overwintering phenology and restricting effective conservation and management. Our objectives were to identify environmental cues of spring emergence for C. horridus in Illinois to determine the species’ emergence phenology, and to examine the applicability of identified cues in predicting emergence phenology across the species’ range. We used wildlife cameras and weather station-derived environmental data to observe and predict the daily surface presence of C. horridus throughout the late winter and early spring at communal refugia in west-central and northern Illinois. The most parsimonious model for predicting surface presence included the additive effects of maximum daily temperature, accumulated degree days, and latitude. With a notable exception in the southeastern U.S., the model accurately predicted the average emergence day for eight other populations range wide, emphasizing the importance of temperature in influencing the phenological plasticity observed across the species’ range. The apparent broad applicability of the model to other populations suggests it can be a valuable tool in predicting spring emergence phenology. Our results provide a foundation for further ecological enquiries and improved management and conservation strategies.


Read the paper at:

Jesper AC, Eckert SA, Bielema BJ, Ballard SR, Dreslik MJ. 2023. Phenology and predictors of spring emergence for the Timber Rattlesnake (Crotalus horridus) PeerJ 11:e16044

New publication from aquatic ecologist Hugo Ruellen

INHS PaCE Lab’s aquatic ecologist, Hugo Ruellen is lead author on a recent publication stemming from his M.Sc. research on freshwater mussels: “Predicting suitable habitat for surrogate species of critically imperiled freshwater mussels to aid in translocations.”

Mussel translocations have been used to mitigate the impacts of in-stream construction projects, including bridge replacements. This work developed a model to predict suitable habitat for mussels. “Knowing where and how much suitable habitat is present in rivers is essential to the conservation and long-term persistence of endangered freshwater mussel species, and habitat suitability models such as these are important tools for achieving these goals.”


Ruellan, Hugo Y., Kirk W. Stodola, Alison P. Stodola, and Jeremy S. Tiemann. 2023. Predicting suitable habitat for surrogate species of critically imperiled freshwater mussels to aid in translocations. Freshwater Science 42(3): 296-314.

Popular article: Discovering the Ornate Box Turtle: A Rare, Remarkable Illinois Reptile

Graduate student Devin Edmonds wrote an article for the August Issue of Outdoor Illinois, showcasing the subject of his M.Sc. thesis research, the Ornate Box Turtle.

Less common than their Eastern Box Turtle relatives, the Ornate Box Turtle is listed as state threatened. Learn more about this “Rare, Remarkable Illinois Reptile.”

Outdoor Illinois – Discovering the Ornate Box Turtle: A Rare, Remarkable Illinois Reptile

INHS PaCE Lab at Turtle Survival Alliance Symposium

Dr. Dreslik and several lab members are presenting posters and talks in Charleston, South Carolina this week for the Turtle Survival Alliance’s 21st Annual Symposium on the Conservation and Biology of Tortoises and Freshwater Turtles


Population structure of the Western Pond Turtle (Actinemys spp.) across twelve military installations in California
Emily Asche, Matthew I. Parry, Thomas S. B. Akre, Robert Lovich, and Michael J. Dreslik
Western Pond Turtle (Actinemys spp.) populations are currently threatened with habitat loss, predation, and shell disease. The synergies among threats have caused severe population declines whereby they are an endangered species in Washington, a sensitive species in Oregon, and a species of special concern in California. It is imperative to investigate their status in California to determine how prevalent threats are and what level of conservation action needs to be taken to avoid declines. We examined the population structure of the Western Pond Turtle populations at twelve military installations across California through sampling in one-week bouts using 50 aquatic traps at one visit per base. We recorded the body size, life stage, and sex of all individuals. Our study is intended to represent a first pass at determining if there are any immediate conservation concerns, such as biases in stage or sex ratios and population size structure.

Detection and occupancy of the Western Pond Turtle (Actinemys spp.)
Matthew I. Parry, Emily Asche, Robert Lovich, Thomas S. B. Akre and Michael J. Dreslik
Low densities, followed by a secretive nature, create challenges for accurately estimating population estimates and site occupancy rates. The Western Pond Turtle (Actinemys spp.) faces range-wide declines and is currently a species of special concern in California. Our project aims to determine their status across 12 military installations using an occupancy/detection framework while attempting to maximize captures during one 50 aquatic trap/four trap night sampling session per installation. Because we sampled areas of known occupancy, we could focus on estimating detection rates. We aim to create an MS Excel tool to determine the detection probabilities while accounting for various environmental and habitat-related covariates.

Survival matters: Comparing the demographic traits of Clemmys and Glyptemys with long-term capture-recapture data
Devin Edmonds, Michael J. Dreslik, Jeffrey E. Lovich, and Carl H. Ernst

Freshwater turtles are one of the most threatened vertebrate groups, with over half of all species at risk of extinction. Overexploitation and habitat loss are the largest threats, with many turtle populations now small, isolated, and needing conservation action to ensure they persist. To enact informed conservation measures and monitor recovery efforts, managers benefit from information about demographic rates like survival and recruitment for highly threatened turtle species. Survival plays a particularly important role in population persistence, considering the life history of most turtle species is characterized by a long lifespan, delayed sexual maturity, and low fecundity. Thus, even small changes in adult annual survival rates can cause otherwise stable populations to decline. We analyzed three historical long-term capture-recapture datasets to estimate annual survival and recruitment for populations of Spotted Turtles (Clemmys guttata), Wood Turtles (Glyptemys insculpta), and Bog Turtles (Glyptemys muhlengerbii) that live in increasingly threatened wetlands and surrounding habitats. All three have ranges characterized by disjunct distributions and often small and isolated populations. Adult sex ratios in turtles can be affected by differences between the sexes in the timing of maturity, rates of mortality, sex-determining mechanism, or differential immigration/emigration. The two Glyptemys species have genetic sex determination while Clemmys has environmental sex determination. This latter distinction could affect each species responses under warming climate scenarios, since Clemmys might be expected to have female-biased populations as global temperatures increase. However, sex-specific differences in survival of Glyptemys species could also occur. Using multi-decadal data, we analyze sex-specific and species-specific survivorship from a site in eastern Pennsylvania where these turtles were sympatric. Our results help inform conservation efforts for three threatened freshwater turtle species and show the strengths of historic long-term data.

Baseline energetic requirements of Ornate Box Turtles (Terrapene ornata)
Andrea L. Colton and Michael J. Dreslik

Increasing ambient temperatures due to climate change may lead to altered behaviors as turtles attempt to regulate internal body temperatures. Increased efforts to maintain temperatures may result in energetic tradeoffs, leading to reduced individual fitness and, thus, population abundance. Estimation of resting metabolic rates for turtles affords calculation of baseline energetic requirements and the potential to predict costs associated with warming landscapes. Using flow-through respirometry, we will determine the resting metabolic rates (RMRs) of adult Ornate Box Turtles (Terrapene ornata) across a temperature gradient to provide information on energetic costs. The baseline estimates will then be used to determine the annual RMR costs on the landscape.

Ranges on the spectrum of recovery: conservation action for the Spotted Turtle and Eastern River Cooter in Illinois
Michael J. Dreslik

Extinction rates in the Anthropocene are significantly higher than background and previous major events. The extinction process can occur when local populations become extirpated, particularly those on the range periphery where habitats are often sub-optimal. Turtles are one of the most critically endangered taxa, with many anthropogenic factors triggering declines. Although jurisdictional boundaries can often complicate conservation, many North American turtles have peripheral populations of conservation concern. Within Illinois, peripheral populations of the Spotted Turtle (Clemmys guttata) and Eastern River Cooter (Pseudemys concinna) are protected as State Endangered; however, their apparent recovery is quite different. I discuss conservation prioritizations, status assessments, and conservation implementation needs for both species in Illinois. Finally, I compare the pathways to recovery for both species.
Conservation Tools and Actions: Oral Thursday PM