Michael Hilton

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.

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).

Pinball machines combine art and engineering in a fun project for teaching a broad range of maker skills Eckerd offers a two-semester STEM course designed to increase the number of students majoring in physics, math, and computer science. The first semester teaches digital fabrication, CAD, microcontroller-based electronics and programming. Students put these skills to use in the second semester by designing and building full-sized pinball machines.

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.

Social network analyses are sparse, despite having great potential to illuminate intricate details of wildlife behavioral ecology and to inform basic conservation practices. Using social interactions recorded during 1 year of 5-second interval photography, we conducted social network analyses of Gopher Tortoises (Gopherus polyphemus). G. polyphemus are charismatic and declining mid-sized tortoises that are habitat specialists endemic to the southeastern United States. We also conducted a simultaneous radio-telemetric study of tortoises contained within our study population to ascertain whether home range location is consistent with membership in distinct tortoise social network communities. We found strong statistical support for the presence of nonrandom social networks that were derived from male-female mating relationships. The most parsimonious social network included two distinct “cliques” that were spatially segregated. Each clique contained a similar number of males and females. Understanding this basic aspect of tortoise behavior should be key in basic population biology, not only of turtles but also other reptiles. Our results should influence protocols for successful conservation of this keystone species.

Many institutions have a Makerspace, but integrating them into our classrooms can be a challenge, even for physics teachers. A Makerspace takes a lot of care and feeding. This talk will focus on the examples of Maker-based projects that have worked and those that haven’t and, importantly, the contexts for each. Scaffolding and strong connections to the classroom have been important for our success.

The overlap between spatial and physiological ecology is generally understudied, yet both fields are fundamentally related in assessing how individuals balance limited resources. Herein, we quantified the relationships between spatial ecology using two parameters of home range (annual home range area and number of burrows used in one year) and four measures of physiology that integrate stress and immunity (baseline plasma corticosterone concentration [CORT], plasma lactate concentration, heterophil:lymphocyte ratio [H:L], and bactericidal ability [BA]) in a wild free-ranging population of the gopher tortoise (Gopherus polyphemus) to test the hypothesis that space-usage is correlated with physiological state. We also used structural equation modeling (SEM) to test for causative relationships between the spatial and physiological parameters. We predicted that larger home ranges would be negatively correlated to traditional biomarkers of stress and positively correlated with immunity, consistent with our hypothesis that home ranges are determined based on individual condition. Males had larger home ranges, used more burrows, and higher baseline CORT than females. We found significant negative correlations between lactate and home range (r = -0.456, df = 21, P = 0.029). CORT was negatively correlated with number of burrows used in both sexes (F = 7.322, df = 2,20, P = 0.003, Adjusted R² = 0.383). No correlations were observed between space use and BA or, notably, H:L. SEM models suggested that variation in number of burrows used was a result of variation in baseline corticosterone. The lack of a relationship between H:L and home range suggests that home range differences are not associated with differences in chronic stress, despite the pattern between baseline CORT and number of burrows used. Rather, this study indicates that animals balance tradeoffs in energetics, likely by way of baseline corticosteroid, in such a way as to maintain function across continuously variable home range strategies.