Jeff Goessling

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.

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.

Global change is leading to increased prevalence of ectotherm diseases. Cryptosporidium

serpentis is a gastrointestinal, protozoal parasite that can cause varying degrees of morbidity and

mortality in snakes. The purpose of this study is to understand the innate immunity of eastern

indigo snakes (Drymarchon couperi) infected with C. serpentis. Body condition index,

heterophil: lymphocyte ratio, bactericidal ability, sheep red blood cell hemagglutination ability,

and plasma corticosterone levels were compared between C. serpentis positive (C+), negative

(C-), and recovered (Cr) individuals. Cr snakes had significantly higher BCI than C- and C+

snakes (ANOVA; F= 11.2 2,80, p<0.01), males had significantly higher bactericidal ability than

females (F= 1.24 2.94, p=0.0462), females had significantly higher corticosterone levels than males

(F=1.24, d.f=2,94, p=0.0462), bactericidal ability had a significant positive relationship with

heterophil: lymphocyte ratio (F=2.17, d.f.=2,71, p=0.033), and bactericidal ability had a

significant positive relationship with sheep red blood cell hemagglutination ability (F=2.17,

d.f.=2,71, p=0.033). These results suggest snakes that recover from C. serpentis may not have

any long-lasting negative effects in regard to their immune system or robustness. These results

also give insight into reptilian physiological ecology, supporting the hypothesis that meaningful

connections exist between different immunological traits.

It is well known that hormones influence and direct most facets of physiology; however, there is still contention regarding the directions of certain relationships, for example, between gonadal hormones and immunity. Among the many proposed relationships relating to gonadal-immune interactions, support for immunosuppressive effects of androgens remains prominent within physiological literature. Although ample study has been directed toward the immunosuppressive effects of androgens, considerable disagreement remains regarding their influence on immune function. In this study, we test the hypothesis that androgens inhibit immunocompetence in the American alligator (Alligator mississippiensis). Developing alligators were incubated at female-producing temperatures with a subset of individuals being exposed to 17-α-methyltestosterone (MT) before sexual determination. 17-α-methyltestosterone is a potent androgen, not aromatizable by crocodilians, that has been found to exert masculinizing effects in exposed crocodilian populations in vivo and in vitro. Additionally, a subset of animals was exposed to a novel antigen to quantify innate and acquired immune function. We recovered no significant differences in leukocyte ratios or proportions between groups and found no significant differences in innate immune function as measured by hemolysis-hemagglutination. However, we did find significant differences in acquired immune function, where masculinized individuals expressed greater antibody titers. Our findings reject the hypothesis that androgens suppress immune function; rather, androgens may be immunoenhancing to acquired humoral responses and neutral to innate humoral immunity in crocodilians.

Large-scale Gopher Tortoise translocations are a widespread practice to remove tortoises from imminent dangers of habitat loss for human development. However, translocation for explicit conservation goals remains an infrequently-utilized and untested tool to conserve this at-risk species. Given the effects of density on tortoise movement and population viability, we conducted a conservation effort to increase the population density of a low-density tortoise population on a public property in southern Alabama. Efforts included consolidating the resident tortoises from a fire-suppressed landscape into a temporary enclosure located in a high-quality restored sandhill. We also headstarted two cohorts of hatchlings from the site for one and two years. In total, 100 resident tortoises were consolidated into the enclosure and 98 headstarted juvenile tortoises were released into the nearby area into both soft- and hard-release conditions. Using radiotelemtry of a sub-population of consolidated adults tracked for two seasons (before and after the enclosure was removed), we found that site fidelity of the adults was 69% in the area enclosed by the pen and 93% in the wider-managed site. Adult home range area was not significantly different between the years that adult tortoises were enclosed in the pen and the year after the pen was removed. A subpopulation of two-year old headstarts was also radiotracked. Radiotracked headstarts had 100% site fidelity, regardless of release condition, and home ranges significantly decreased over the study period. Mortality was extremely low in all groups. We further discuss how this research may contribute to effective strategies for the demographic management of low-density tortoise populations, particularly in the species’ distributional periphery.