Brett A. DeGregorio

Out-foxing the red fox: how best to protect the nests of the Endangered loggerhead marine turtle Caretta caretta from mammalian predation?

Recovery plans for the Endangered loggerhead marine turtle Caretta caretta cite mammalian predation as a major threat, and recommend nest protection efforts, already present at many rookery beaches, to protect eggs and hatchlings. Nest protection techniques vary but wire box cages and plastic mesh screens are two common tools used to deter predation by a host of beach-foraging, opportunistic mammalian predators. We empirically tested the efficacy of wire cages and plastic mesh screens in preventing red fox Vulpes vulpes predation on artificial nests. Both techniques averted fox predation (0%), whereas unprotected control nests suffered 33% predation under conditions of normal predator motivation, or a level of motivation stimulated by loggerhead turtle egg scent. However, in side-by-side comparisons under conditions of presumed high predator motivation, 25% of mesh screens were breached whereas no cage-protected nests were successfully predated. In addition to effectiveness at preventing predation, factors such as cost, ease of use, deployment time, and magnetic disturbance were evaluated. Our study suggests that the efficacy of plastic screens and the potential disadvantages associated with galvanized wire should influence selection of mechanical barriers on beaches where fox predation threatens loggerhead nests.

Overwintering of Gopher Tortoises (Gopherus polyphemus) Translocated to the Northern Limit of Their Geographic Range: Temperatures, Timing, and Survival

Abstract We examined overwintering behavior in gopher tortoises (Gopherus polyphemus) translocated to the northern periphery of their geographic range by using miniature temperature data loggers during 2 winters. All adult and juvenile tortoises monitored with temperature loggers survived overwintering; however, during the course of the study 2 translocated juvenile tortoises without temperature loggers died during winter months. Onset and termination of overwintering were not different between the 2 yrs and were not correlated with mean above-ground air temperature. Mean overwinter duration was 127 ± 9 d SD and 128 ± 13 d SD during 2002–2003 and 2004–2005, respectively. Tortoises experienced temperatures as low as 7°C and as high as 31°C while overwintering; however, most (12 of 15) tortoises experienced very little (< 1°C) mean daily temperature fluctuation despite air temperatures regularly dropping below 0°C and exceeding 20°C. The overall mean temperature of overwintering tortoises was 12.4° ± 0.8°C (2002–2003) and 12.6° ± 1.2°C (2004–2005). Large fluctuations in temperature occurred when tortoises actively basked, and half of the monitored tortoises did, particularly juveniles, which accounted for 42% of winter basking events. Our results suggest that, given timely access to suitable refugia at recipient sites, overwinter mortality of translocated adult individuals may be minimal.

Nest Guarding in the Gopher Tortoise (Gopherus polyphemus)

Abstract Nest guarding is rarely observed among reptiles. Specifically, turtles and tortoises are generally perceived as providing no nest protection once the eggs are laid. Here, we describe observations of nest guarding by female gopher tortoises (Gopherus polyphemus).

Climatic and geographic predictors of life history variation in Eastern Massasauga (Sistrurus catenatus): A range-wide synthesis

Elucidating how life history traits vary geographically is important to understanding variation in population dynamics. Because many aspects of ectotherm life history are climate-dependent, geographic variation in climate is expected to have a large impact on population dynamics through effects on annual survival, body size, growth rate, age at first reproduction, size–fecundity relationship, and reproductive frequency. The Eastern Massasauga (Sistrurus catenatus) is a small, imperiled North American rattlesnake with a distribution centered on the Great Lakes region, where lake effects strongly influence local conditions. To address Eastern Massasauga life history data gaps, we compiled data from 47 study sites representing 38 counties across the range. We used multimodel inference and general linear models with geographic coordinates and annual climate normals as explanatory variables to clarify patterns of variation in life history traits. We found strong evidence for geographic variation in six of nine life history variables. Adult female snout-vent length and neonate mass increased with increasing mean annual precipitation. Litter size decreased with increasing mean temperature, and the size–fecundity relationship and growth prior to first hibernation both increased with increasing latitude. The proportion of gravid females also increased with increasing latitude, but this relationship may be the result of geographically varying detection bias. Our results provide insights into ectotherm life history variation and fill critical data gaps, which will inform Eastern Massasauga conservation efforts by improving biological realism for models of population viability and climate change.

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

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.

Commercial Value of Amphibians Produced From an Isolated Wetland

Abstract Despite the functional importance of isolated wetlands as supporters and sources of diverse assemblages of amphibians and reptiles, they lack federal protection and local protection is often insufficient to halt their destruction. A key step in guiding informed policy towards isolated wetlands is to understand their economic value. This study combines a year of intensive amphibian surveys within a wetland with the assignment of values to each of the captured species based upon their reported commercial values. The 392,605 amphibians comprising 17 species captured at this wetland in 1 y were valued at

To forage, mate, or thermoregulate: Influence of resource manipulation on male rattlesnake behavior

3,605,848 (U.S. dollars). Juvenile amphibians produced in the wetland in a single year accounted for the 95% of the reported value (

Do seasonal patterns of rat snake (Pantherophis obsoletus) and black racer (Coluber constrictor) activity predict avian nest predation

3,413,821). This value far exceeds the value of other natural habitats evaluated with similar methods and exceeds by two orders of magnitude the value of this land had it been converted to agriculture. Although this study does not advocate amphibian harvest as an economic use for wetlands, it does highlight the value, diversity, and abundance of amphibians inhabiting these small, isolated, and often unprotected wetlands and provides a foundation for future research, management, mitigation, and policy.

The Spatial Ecology of the Eastern Massasauga (Sistrurus c. catenatus) in Northern Michigan

Abstract Male animals should preferentially allocate their time to performing activities that promote enhancing reproductive opportunity, but the need to acquire resources for growth and survival may compete with those behaviors in the short term. Thus, behaviors which require differing movement patterns such as ambushing prey and actively searching for mates can be mutually exclusive. Consequently, males that succeed at foraging could invest greater time and energy into mate searching. We radio‐tracked sixteen male massasauga rattlesnakes (Sistrurus catenatus) and supplemented the diets of half the snakes with mice across an active season. We tested the predictions that reduced foraging needs would allow fed snakes to move (i.e., mate search) more, but that they would consequently be stationary to thermoregulate less, than unfed controls. Contrary to our first prediction, we found no evidence that fed snakes altered their mate searching behavior compared to controls. However, we found controls maintained higher body temperatures than fed snakes during the breeding season, perhaps because fed snakes spent less time in exposed ambush sites. Fed snakes had higher body condition scores than controls when the breeding season ended. Our results suggest the potential costs incurred by devoting time to stationary foraging may be outweighed by the drive to increase mating opportunities. Such instances may be especially valuable for massasaugas and other temperate reptiles that can remain inactive for upwards of half their lives or longer in some cases, and for female rattlesnakes that generally exhibit biennial or more protracted reproductive cycles.

Nest Predators of North American Birds: Continental Patterns and Implications

Abstract Avian nest success often varies seasonally and because predation is the primary cause of nest failure, seasonal variation in predator activity has been hypothesized to explain seasonal variation in nest success. Despite the fact that nest predator communities are often diverse, recent evidence from studies of snakes that are nest predators has lent some support to the link between snake activity and nest predation. However, the strength of the relationship has varied among studies. Explaining this variation is difficult, because none of these studies directly identified nest predators, the link between predator activity and nest survival was inferred. To address this knowledge gap, we examined seasonal variation in daily survival rates of 463 bird nests (of 17 bird species) and used cameras to document predator identity at 137 nests. We simultaneously quantified seasonal activity patterns of two local snake species (N = 30 individuals) using manual (2136 snake locations) and automated (89,165 movements detected) radiotelemetry. Rat snakes (Pantherophis obsoletus), the dominant snake predator at the site (~28% of observed nest predations), were most active in late May and early June, a pattern reported elsewhere for this species. When analyzing all monitored nests, we found no link between nest predation and seasonal activity of rat snakes. When analyzing only nests with known predator identities (filmed nests), however, we found that rat snakes were more likely to prey on nests during periods when they were moving the greatest distances. Similarly, analyses of all monitored nests indicated that nest survival was not linked to racer activity patterns, but racer‐specific predation (N = 17 nests) of filmed nests was higher when racers were moving the greatest distances. Our results suggest that the activity of predators may be associated with higher predation rates by those predators, but that those effects can be difficult to detect when nest predator communities are diverse and predator identities are not known. Additionally, our results suggest that hand‐tracking of snakes provides a reliable indicator of predator activity that may be more indicative of foraging behavior than movement frequency provided by automated telemetry systems.