Jinelle H. Sperry

Evaluation of Automated Radio Telemetry for Quantifying Movements and Home Ranges of Snakes

Abstract We evaluated an automated telemetry system that can dramatically increase the amount of activity and spatial data collected for snakes. We developed methods for analyzing data from single automated receiving units (ARUs) and ARU arrays, compared results from ARUs with conventional hand tracking, and assessed previously untested assumptions used in conventional telemetry, using data from ratsnakes (Pantherophis spp.) in Texas and Illinois. ARU data indicated that ratsnakes spent most of their time in small home ranges (mean = 25 ha) but engaged in forays of up to 1.5 km from their core-use areas, suggesting this species may engage in central place foraging. Forays inflated home-range sizes greatly if areas were estimated using minimum convex polygons rather than 95% kernels. Large numbers of locations generated by ARUs produce more reliable home-range estimates than those from hand tracking. ARU data indicated that snakes moved in response to observers during hand tracking. Daily hand tracking produced reliable estimates of distances moved but underestimated distances by a factor of 4 when snakes were tracked every 5 days. Drawbacks of ARUs are that the error associated with individual locations exceeds that for hand-tracked locations and that the costs exceed those for hand tracking. Automated receivers can increase data greatly from radio-tracked snakes, providing novel insights unavailable from conventional hand tracking. There are drawbacks to this technology, some of which will vary among study species; therefore, researchers should evaluate the appropriateness of the technology for both the study species and the questions being asked.

Effects of temperature, moon phase, and prey on nocturnal activity in Ratsnakes: An automated telemetry study

Abstract Nocturnal activity is important for many animals, but difficulty in documenting that activity has hampered efforts to understand factors that influence when animals are active at night. We used automated radiotelemetry to provide the first detailed tests of the hypothesis that the nocturnal activity of free-ranging snakes should be influenced by temperature, moon phase, and prey abundance by using data for Ratsnakes (Pantherophis spp.) from Texas and Illinois. Ratsnakes exhibited some nocturnal behavior throughout their active season in both Texas and Illinois, although snakes were much more active at night in Texas than in Illinois. Texas snakes transitioned from primarily diurnal activity to primarily nocturnal activity over this snakes active season, whereas Illinois snakes were always most active in the middle of the day. For both populations, nocturnal activity was positively related to temperature but unrelated to moon phase. Ratsnakes in Texas exhibited a stepwise increase in nocturnal activity in mid-summer, independent of temperature and coincident with the shift in their diet to almost exclusively mammals active at night. Given the ability of snakes in both populations to be active at night when temperatures allow, warming climates could lead to an increase in nocturnal activity, with consequences for both the snakes and the species on which they prey.

Power lines, roads, and avian nest survival: effects on predator identity and predation intensity

1 Anthropogenic alteration of landscapes can affect avian nest success by influencing the abundance, distribution, and behavior of predators. Understanding avian nest predation risk necessitates understanding how landscapes affect predator distribution and behavior. 2 From a sample of 463 nests of 17 songbird species, we evaluated how landscape features (distance to forest edge, unpaved roads, and power lines) influenced daily nest survival. We also used video cameras to identify nest predators at 137 nest predation events and evaluated how landscape features influenced predator identity. Finally, we determined the abundance and distribution of several of the principal predators using surveys and radiotelemetry. 3 Distance to power lines was the best predictor of predator identity: predation by brown-headed cowbirds (Molothrus ater), corvids (Corvus sp. and Cyanocitta cristata), racers (Coluber constrictor), and coachwhips (Masticophis flagellum) increased with proximity to power lines, whereas predation by rat snakes (Elaphe obsoleta) and raptors decreased. In some cases, predator density may reliably indicate nest predation risk because racers, corvids, and cowbirds frequently used power line right-of-ways. 4 Of five bird species with enough nests to analyze individually, daily nest survival of only indigo buntings (Passerina cyanea) decreased with proximity to power lines, despite predation by most predators at our site being positively associated with power lines. For all nesting species combined, distance to unpaved road was the model that most influenced daily nest survival. This pattern is likely a consequence of rat snakes, the locally dominant nest predator (28% of predation events), rarely using power lines and associated areas. Instead, rat snakes were frequently associated with road edges, indicating that not all edges are functionally similar. 5 Our results suggest that interactions between predators and landscape features are likely to be specific to both the local predators and landscape. Thus, predicting how anthropogenic changes to landscapes affect nesting birds requires that we know more about how landscape changes affect the behavior of nest predators and which nest predators are locally important.

Habitat Use and Seasonal Activity Patterns of the Great Plains Ratsnake (Elaphe guttata emoryi) in Central Texas

Abstract The Great Plains ratsnake (Elaphe guttata emoryi) is a poorly known species of the central and southern United States. We captured 24 Great Plains ratsnakes over 3 years at Fort Hood, Texas, and used radiotelemetry to determine habitat use and seasonal activity patterns of five adult male snakes. Great Plains ratsnakes showed an affinity for human-made structures with the majority of locations in rock structures used to control erosion. When compared to random sites, snake-selected sites were in areas of increased structure with more trees and ground cover and closer to habitat edges. Despite Great Plains ratsnakes having been documented preying on nests of arboreal birds, tracked snakes were found almost exclusively at or below ground level. Snakes were active year round and did not exhibit distinct hibernation times or sites. Snakes exhibited a bimodal pattern of activity with peaks in late spring and autumn, most likely due to temperature constraints.

Reproductive Decisions in Anurans: A Review of How Predation and Competition Affects the Deposition of Eggs And Tadpoles

The selection of breeding habitat has broadscale implications for species distributions and community structure and smaller-scale ramifications for offspring survival and parental fitness. In anurans, offspring deposition is a decisionmaking process that involves the assessment of multiple factors at a breeding site, including the presence of predators and competitors. Evolutionary theory predicts that adult anurans should seek to minimize the risk of predation to offspring, reduce the pressure of competition, and maximize offspring survival. Many experimental studies have demonstrated the ability of anurans to assess deposition sites for predation and competition and to choose accordingly, but our understanding of the various ecological factors involved in site choice and the broader consequences of choice is still limited. Here, we review and synthesize the literature on the influence of predators and competitors on anuran deposition behavior. We highlight current gaps in our understanding of this topic and outline future avenues of research.

An efficient and inexpensive method for measuring long-term thermoregulatory behavior.

Thermoregulatory ability and behavior influence organismal responses to their environment. By measuring thermal preferences, researchers can better understand the effects that temperature tolerances have on ecological and physiological responses to both biotic and abiotic stressors. However, because of funding limitations and confounders, measuring thermoregulation can often be difficult. Here, we provide an effective, affordable (~

Use of the NatureServe Climate Change Vulnerability Index as an Assessment Tool for Reptiles and Amphibians: Lessons Learned

50 USD per unit), easy to construct, and validated apparatus for measuring the long-term thermal preferences of animals. In tests, the apparatus spanned temperatures from 9.29 to 33.94°C, and we provide methods to further increase this range. Additionally, we provide simple methods to non-invasively measure animal and substrate temperatures and to prevent temperature preferences of the focal organisms from being confounded with temperature preferences of its prey and its humidity preferences. To validate the apparatus, we show that it was capable of detecting individual-level consistency and among individual-level variation in the preferred body temperatures of Southern toads (Anaxyrus terrestris) and Cuban tree frogs (Osteopilus septentrionalis) over three-weeks. Nearly every aspect of our design is adaptable to meet the needs of a multitude of study systems, including various terrestrial amphibious, and aquatic organisms. The apparatus and methods described here can be used to quantify behavioral thermal preferences, which can be critical for determining temperature tolerances across species and thus the resiliency of species to current and impending climate change.

ECOLOGICAL FACTORS AFFECTING RESPONSE OF DARK-EYED JUNCOS TO PRESCRIBED BURNING

Climate change threatens biodiversity globally, yet it can be challenging to predict which species may be most vulnerable. Given the scope of the problem, it is imperative to rapidly assess vulnerability and identify actions to decrease risk. Although a variety of tools have been developed to assess climate change vulnerability, few have been evaluated with regard to their suitability for certain taxonomic groups. Due to their ectothermic physiology, low vagility, and strong association with temporary wetlands, reptiles and amphibians may be particularly vulnerable relative to other groups. Here, we evaluate use of the NatureServe Climate Change Vulnerability Index (CCVI) to assess a large suite of herpetofauna from the Sand Hills Ecoregion of the southeastern United States. Although data were frequently lacking for certain variables (e.g., phenological response to climate change, genetic variation), sufficient data were available to evaluate all 117 species. Sensitivity analyses indicated that results were highly dependent on size of assessment area and climate scenario selection. In addition, several ecological traits common in, but relatively unique to, herpetofauna are likely to contribute to their vulnerability and need special consideration during the scoring process. Despite some limitations, the NatureServe CCVI was a useful tool for screening large numbers of reptile and amphibian species. We provide general recommendations as to how the CCVI tool’s application to herpetofauna can be improved through more specific guidance to the user regarding how to incorporate unique physiological and behavioral traits into scoring existing sensitivity factors and through modification to the assessment tool itself.

Translocating ratsnakes: does enrichment offset negative effects of time in captivity?

Abstract We compared abundance, daily survival rate, nest site characteristics, food availability, nest activity, and nestling size of Dark-eyed Juncos (Junco hymenalis) between burned and unburned mechanically-thinned ponderosa pine (Pinus ponderosa) forest units. Dark-eyed Junco territory density, number of detections in point counts, and daily nest survival were similar between treatments. Average bare ground was 4.8 times higher and litter cover was 2.6 times lower at nest sites in burned units compared to unburned nest sites. However, there was 28% less burned area around nests compared to random points in burned units, indicating that juncos placed nests in unburned portions of burned units. They also selected non-traditional nesting sites in burned units such as root holes and in trees. Arthropod abundance was higher in burned units 1-year post burn although numbers were similar in the second-year post burn. Nest attentiveness and feeding rates were three times higher in burned units, possibly in response to increased food availability. The potentially negative effect of prescribed burning through reduction of litter and increase in bare ground was offset by novel nesting strategies and increased food availability.

Mortality Patterns and the Cost of Reproduction in a Northern Population of Ratsnakes, Elaphe obsoleta

Abstract Context. Wildlife translocation is a conservation tool with mixed success. Evidence suggests that longer time in captivity may negatively affect an animal’s post-release behaviour and survival. However, environmental enrichment may reduce the deleterious effects of captivity for animals that are going to be released into the wild. Aims. The aim of the present study was to compare first-year post-release survival and behaviour of translocated ratsnakes (Pantherophis obsoletus) held captive for varying durations (1–7 years) either with or without enrichment, with that of resident and wild-to-wild (W–W)-translocated ratsnakes. Key results. Being in captivity before release negatively affected survival; 11 of 19 (57.9%) captive snakes died or were removed from the study within 12 months, compared with 3 of 11 (27.3%) resident snakes and none of five (0%) W–W snakes. Furthermore, survival probability declined the longer a snake had been in captivity. Six of the seven snakes (86%) that we released that had been in captivity for four or more years before release died during this study, regardless of whether they were enriched or not. Although W–W-translocated ratsnakes moved more often and further than did snakes in other groups, this difference was apparent only in the first month post-release. We found no evidence that abnormal movement patterns or winter behaviour was the cause of reduced survival for captive snakes. Instead, our data suggested that spending time in captivity reduced concealment behaviour of snakes, which likely increased the vulnerability of snakes to predators. Captivity also compromised the foraging ability of some of the snakes. Although there were no overall differences in percentage weight change among the four groups, two snakes (one enriched, one unenriched) were removed from the study because of extreme weight loss (>30%). Conclusions. Our results suggested that environmental enrichment did not offset the negative effects of captivity on ratsnakes and that the likely mechanism responsible for low survival was vulnerability to predators. Implications. Whether extended periods in captivity render other species unsuitable for translocation, how long it takes for captivity to have deleterious effects, and whether environmental enrichment is also ineffective at offsetting captivity effects in other species remain to be determined.