Jeff Goessling

Animals face myriad decisions when confronting challenges to the maintenance of thermoregulatory setpoints and a frequent response to seasonal thermal challenges is a reduction in function and dormancy induction. Tradeoffs exist that result in strategies that either favor dormancy or sustained activity through thermal challenges , such as winter. Our study focused on a population of gopher tortoises (Gopherus polyphemus), a species that is distributed along the lower southeastern coastal plain of North America (i.e. a warm-temperate to subtropical climate range). Our study population was located near the edge of the species' southern range. Using affixed autonomous GPS trackers containing temperature sensors, we investigated shifts in field thermal performance curves (TPC) in response to shifts in environmental temperature between seasons and we also tested the relationship between winter activity and temperatures to test which strategy (i.e., dormancy vs activity) this study population utilized during the coldest period of the year. Field TPCs were significantly cold shifted during the coldest 28-day period of winter and 80% thermal performance breadth (B80) was greatest during the coldest winter period. Although most individuals were active throughout the coldest period, overall performance, as measured by spatial velocity, was reduced. Tortoises, however, maintained high activity levels as measured by distances moved during the coldest period. Only seven out of 30 individuals induced dormancy, and in those individuals, the mean overwintering period was only 17 days; both proportion of individuals dormant and dormancy duration of gopher tortoises in this study was lower than has been previously observed in other studies. This study indicates this species facultatively utilizes numerous strategies for mitigating winter constraints.

1. A central topic in spatial ecology is identifying what determines animal movement patterns, including both exogenous and endogenous factors. Given that there are different sex-based selection pressures in mating and reproduction, movement patterns often vary between males and females in predictable manners; males of polygynous species typically move more than females to maximize mating opportunities. In female polygynous animals, selection is generally thought to favor movement patterns with smaller home ranges and high spatial site fidelity. Physiology may also constrain movement patterns in a way that can obscure sex-specific selection.
2. We used GPS loggers and physiological assays to study Gopher Tortoise (Gopherus polyphemus) movement patterns to determine how movement patterns depend on physiology (as measured by plasma lactate concentration and body condition) and movement strategy (total distance traveled over the course of the study, daily distance traveled, maximum daily displacement, home range area, burrow use) by sex.
3. Total distance traveled was positively related to body condition and negatively related to baseline lactate concentration (which is an inverse metric of aerobic fitness). Thus, total distance traveled was physiologically constrained. Home range area and burrow use were not related to any physiological metrics.
4. There was not a significant difference in total distance traveled nor daily distance traveled between male and female Gopher Tortoises, but males had larger maximum daily displacements than females. Males also had a larger home range area. Male and female Gopher Tortoises thus used different movement strategies that likely maximize fitness consistent with different selection pressures by sex in a scramble competition mating system.

As the climate continues to warm at an unprecedented rate, much research attention has been focused on climate responses in organisms. Climate responses in the egg stage are restricted to the mother’s choice of nest site in oviparous species without parental care, but can mothers choose nest sites that compensate for climate change effects on developing embryos? We studied nest site choice in the gopher tortoise, Gopherus polyphemus, near the hot end of the species range. We found 25 nests, of which 16 (64%) were located outside burrows (in or near the aprons, the mound of excavated sand at the burrow entrance), as is usually the case for the species. Surprisingly, however, we found nine nests (36%) inside burrows, a novel finding for the species. There was marked variation in the canopy openness of selected nest sites (mean = 42.0%; range 24–62%); openness values of nest sites generally fell between those of potential nest sites in the sunniest (mean =61%) and shadiest (15%) locations. Canopy openness and incident radiation intensity (IRI) were highly, significantly positively related for nest sites and potential nest sites and changed little over the incubation period. Collectively, our data reveal that mothers can reduce mean nest temperatures by ∼2.5–3 °C by nesting 1.5 m down the burrow, or by nesting in the shadiest locations within 50 m of their burrows. Wide variation in openness and IRI and their effects on nest temperatures suggests that, among generations, tortoise mothers have some scope to buffer their developing embryos against climate warming, provided that nest site choice behaviour is heritable and can evolve fast enough to keep pace with future warming. Our novel finding of nests inside burrows suggests that gopher tortoises may have a greater capacity to offset climate warming than most turtles, which do not excavate and inhabit burrows.
•Climate change exposes eggs of oviparous species to hotter temperatures.•Nest site choice is thus a key climate response in oviparous animals.•We found that gopher tortoises can nest in their burrows, not just near them.•Tortoises can depress nest temperatures by 2–3 °C by nesting in shade or in burrows.•Thus, they may be more resilient to climate change than most other turtles.

Studies concerning the social behaviours of non-avian reptiles have generally lagged behind other taxa, yet many reptiles are among the most globally threatened animal groups, and their behaviours are key to conservation successes. Herein, we utilized a captive-reared cohort of headstart Gopher Tortoises (Gopherus polyphemus) to test if these animals first discern soil type by social familiarity and/or tortoise exposure and then we tested how social familiarity and sibling status affected social behaviours between individuals. We found that headstart Gopher Tortoises preferentially chose familiar soil over soil that had never been in contact with a Gopher Tortoise, but they also preferred soil that had been in contact with non-familiar individuals over familiar soil. Tortoises displayed the social behaviour of sniffing disproportionately to non-familiar individuals, regardless of sibling status, over familiar individuals. Other social behaviours of nipping, chasing, headbobbing, and colliding were performed independently of social familiarity or sibling status. Taken together, this set of experiments demonstrates that Gopher Tortoises have a high degree of social nuance that is built upon familiarity, and these results could have direct effects on how to optimize headstarting protocols for restoring wild populations.

1. A central topic in spatial ecology is identifying what determines animal movement patterns, including both external and internal factors. Given different sex-based selection pressures in mating and reproduction, movement patterns often vary between males and females in predictable manners, with males of polygynous species typically moving more than females to maximize mating opportunities. In female polygynous animals, selection is generally thought to favor movement patterns with smaller home ranges and high spatial site fidelity. Physiology may also constrain movement patterns in a way that can obscure sex-specific selection.
2. We used GPS loggers and physiological assays to study Gopher Tortoise (Gopherus polyphemus) movement patterns at Boyd Hill Nature Preserve, located in Pinellas County, Florida, USA to determine how movement patterns depend on physiology (as measured by plasma lactate concentration and body condition) and movement strategy (total distance traveled, home range area, burrow use) by sex.
3. Total distance traveled was positively related to body condition and negatively related to baseline lactate concentration (which is an inverse metric of aerobic fitness). Thus, total distance traveled was physiologically constrained. Home range area and burrow use were not related to any physiological metrics.
4. There was not a significant difference in total linear distance traveled between male and female Gopher Tortoises, but males had a larger home range area. Male and female Gopher Tortoises thus used different movement strategies to maximize fitness consistent with different selection pressures by sex in a scramble competition mating system.

Studies concerning the social behaviours of non-avian reptiles have generally lagged behind other taxa, yet many reptiles are among the most globally threatened animal groups, and their behaviours are key to conservation successes. Herein, we utilized a captive-reared cohort of headstart Gopher Tortoises (Gopherus polyphemus) to test if these animals first discern soil type by social familiarity and/or tortoise exposure and then we tested how social familiarity and sibling status affected social behaviours between individuals. We found that headstart Gopher Tortoises preferentially chose familiar soil over soil that had never been in contact with a Gopher Tortoise, but they also preferred soil that had been in contact with non-familiar individuals over familiar soil. Tortoises displayed the social behaviour of sniffing disproportionately to non-familiar individuals, regardless of sibling status, over familiar individuals. Other social behaviours of nipping, chasing, headbobbing, and colliding were performed independently of social familiarity or sibling status. Taken together, this set of experiments demonstrates that Gopher Tortoises have a high degree of social nuance that is built upon familiarity, and these results could have direct effects on how to optimize headstarting protocols for restoring wild populations.
•Using a cohort of Gopher Tortoises temporarily raised in captivity for conservation, we found that individual tortoises preferentially chose to be on soil from non-familiar tortoises over their own soil and also tortoises avoided soil that had not come into contact with any Gopher Tortoise.•By separating clutch-mates at hatching, we isolated effects of social familiarity from maternal sibling status and found that Gopher Tortoises disproportionately displayed the social behaviour of sniffing non-familiar individuals, regardless of sibling status.•We found that non-familiar sibling pairs did not display any social behaviours differently than non-familiar non-sibling pairs, suggesting that sibling status is not a key social metric that assorts wild Gopher Tortoises into social groups.•Together, these results suggest that Gopher tortoises are both spatially and socially curious yet cautious in both navigating new environments (e.g., novel soil) and interacting with new individuals (e.g., non-familiar members of the same cohort).

Wildlife biologists choose monitoring techniques for threatened and endangered species that optimize time, resources, data quantity, and data quality. We compared 3 commonly used methods of assessing population size in gopher tortoises (Gopherus polyphemus), including burrow censuses, line-transect distance sampling (LTDS) surveys, and mark-recapture surveys. To test how season and year might affect the inferences from surveys, we conducted surveys across multiple seasons during a 2-year continuous interval. We found that mark-recapture estimates yielded tight and consistent estimates of population size, regardless of the statistical model used to analyze the mark-recapture data. Then, we compared results from the mark-recapture study to burrow censuses and LTDS surveys. Our comparison indicated that LTDS surveys had lower variation when the estimates from 2 consecutive years were pooled within each season. Burrow censuses consistently underestimated population size by approximately 19-35%, depending on the sampling year, and did not produce results with confidence intervals. Line-transect distance sampling surveys resulted in mean population size estimates that were consistently lower than mark-recapture results by approximately 9%, though LTDS 95% confidence intervals consistently included the mark-recapture estimate. Our results underscore how not all studies are optimized by using the same survey method. Our results also demonstrate the risk that single-visit population surveys likely underestimate population size, which has implications for the mitigation and translocation management of Gopherus tortoises as well as efforts to quantify the current status of Gopherus species.

As uplands across the southeastern US confront a burgeoning human population, native ecological communities are increasingly stressed by increased predators via urban subsidies to native and invasive predators. Due to a long-standing successful habitat conservation and management program, a natural population of gopher tortoises (Gopherus polyphemus) remains in an urban nature preserve in St. Petersburg, Florida. An ongoing long-term study of tortoises at the site has identified more than 200 unique individual tortoises in this population. Between summer 2023 and 2024, however, more than 20% of the adult tortoise population was found to have been killed by coyotes, which are an invasive species in Florida. The depredated shells of many previously marked, healthy, and reproductive adult tortoises were found across the site and frequently cached and surrounded by coyote scat. Many of these shells were broken throughout individual bones (consistent with a large-gaping canine predator), not just along bone sutures. Three caches of tortoise shells also included other similar-sized carcasses of two other species (domestic cat, Felis catus, and nine-banded armadillo, Dasypus novemcinctus). An unquantifiable number of juvenile and hatchling gopher tortoises have also recently been killed by coyotes at the site, as evidenced by coyote scat in an adult tortoise shell cache containing hatchling tortoise shell scutes. Given the high number of previously-marked and well-studied but recently-depredated tortoises that have been recovered, this presentation will focus on the demographic features of the depredated population (including, sex, size, social network status, and reproductive output of the dead animals). Lastly, we will put this into a broader context and discuss the viability of >20% annual adult mortality and how this should impact regional management of invasive coyotes and this rapidly-declining ecological community.