Howard K. Reinert

Foraging behavior of the timber rattlesnake, Crotalus horridus

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Impacts of Translocation on Behavior and Survival of Timber Rattlesnakes, Crotalus horridus

The impact of translocation on timber rattlesnakes (Crotalus horridus) was assessed experi- mentally by moving 11 specimens distances of between 8 km and 172 km away from their native popula- tions and releasing them into a study area having a resident rattlesnake population. All translocated snakes were equipped with radio transmitters, and their behavior, survival, and interaction with resident snakes were observed. Eighteen resident snakes were also telemetrically monitored during the fouryear study. Six of the 11 (54.5%) translocated snakes are known to have died while only 2 of the 18 (11.1%) resident snakes experienced mortality during the period they were radiotracked. Of the six translocated specimens that died, three experienced overwinter mortality despite their location of resident hibernacula, two were killed by predators, and one died from disease. The mean daily survival rate of translocated snakes (0.9973) was significantly lower than that of resident snakes (0.9993). Translocated snakes selected habitats similar to that of residents, foraged successfully, and maintained body mass. However, translocated snakes exhibited atyp- ical movement patterns consisting of extensive and long-distance traveling. The six translocated male rat- tlesnakes averaged 15,017 m (SE = 2184.3) in total distance traveled from release until hibernation with daily movements of 123.8 m (SE = 19.40) and convex polygon activity range areas of 600.6 ha (SE = 253.0). Comparatively, the total active season distance traveled by the seven resident male rattlesnakes averaged only 5575 m (SE = 936.5) with mean daily movements of 36.9 m (SE = 5.36) and convex polygon activity ranges of 59.9 ha (SE = 13.04). Mean activity parameters 3 to 5 times larger than those of resident snakes were also typical for translocated female rattlesnakes. Translocated snakes located active hibernacula ap- parently by following resident snakes; however, their overwintering mortality was higher than that of res- idents. Translocated snakes that successfully survived the first overwinter period continued to exhibit more extensive movements in their second active season than did residents. However, there was evidence of the establishment of a more resident-like pattern of movement among these specimens during the second year. Translocation of adult snakes is not recommended as a standard conservation practice because of its im- mediate and long-term negative impacts.

Timber rattlesnakes (Crotalus horridus) of the pine barrens: their movement patterns and habitat preference

Radiotelemetry was used to monitor the movements and habitat use of timber rattlesnakes (Crotalus horridus) in the Pine Barrens of southern New Jersey. Reproductive condition strongly influenced both aspects of behavior. Males generally exhibited the largest activity ranges, and the sizes of their ranges were positively correlated with the number of days the snakes were monitored. This was not true for gravid or non-gravid females. Time series analyses indicated that movement patterns of males and non-gravid females consisted of constantly shifting, non-overlapping activity areas. In most cases these snakes moved in a looping pattern during the active season that returned them to the same hibernation site from which they departed. Gravid females exhibited more static, overlapping activity areas and shorter dispersal distances from hibernacula. Males and non-gravid females utilized forested habitat with greater than 50% canopy closure, thick surface vegetation (approx. 75%), and few fallen logs. This habitat occurred with high frequency throughout the study area. Gravid snakes utilized less densely forested sites with approx. 25% canopy closure, an equal mixture of vegetation and leaf litter covering the surface, frequent fallen logs, and warmer climatic conditions. This habitat occurred in low frequency on the study area and was largely restricted to the edge of sand roads.

Recent Occurrence and Dietary Habits of Boa constrictor on Aruba, Dutch West Indies

Abstract Boa constrictor was first documented on the island of Aruba in April of 1999. By the end of December, 2003, 273 B. constrictor had been captured. These snakes ranged in size from neonates (0.30 m total length) to large adults (2.8 m total length) and included at least two gravid females. Boa constrictor is currently distributed islandwide with the highest frequency of occurrence in the southern and southeastern portions of the island. The increasing frequency of occurrence, extensive distribution, and size diversity of B. constrictor indicate that a large, reproductively successful population is established on Aruba. The diet of the B. constrictor on Aruba was determined from the examination of stomach content and scat samples (N = 47). Birds comprised 40.4%, lizards 34.6% and mammals 25.0% of 52 separate prey items identified. A correlation was found between snake total length and prey mass (r(28) = 0.49, P < 0.01) suggesting an ontogenetic shift in the diet at a total length of approximately 1.0 m. In view of the diverse diet and increasing population of B. constrictor, there is concern about the potential impact of this invasive predator on the Aruban fauna. A government instituted euthanization program for all captured B. constrictor has proven ineffective at controlling the population.

Foraging Ecology of Timber Rattlesnakes, Crotalus horridus

Abstract The geographic range of the Timber Rattlesnake (Crotalus horridus) encompasses most of the eastern half of the United States. Although the overall diet composition of C. horridus has been well documented and has been reported to be very broad, local population variation has not been studied. We examined the diet and foraging behavior of C. horridus from four separate populations in Pennsylvania and New Jersey. A total of 253 prey items from scat samples, stomach samples, and field observation were identified to species or family level. Although voles (Myodes gapperi) and mice (Peromyscus spp.) comprised the bulk of the diet in all populations, relative prey species frequency differed significantly among the four populations. These data indicate that the food habits of C. horridus varied widely even within relatively small geographic distances. Comparisons with small mammal trapping data further suggest that the diet composition of this ambush predator may not simply reflect the availability of prey species. Radiotelemetric observations of C. horridus further indicate differing frequencies of log-oriented foraging behavior among the study sites. Analysis of body posture revealed an alternative ambush foraging posture (non-log-oriented posture) which also exhibited variation in frequency among study sites. However, selected foraging habitats at all study sites were typified by a locally high density of fallen logs and other woody debris (6% of forest-floor cover/m2). These findings indicate geographic variation in the foraging ecology of C. horridus and suggest behavioral plasticity in foraging response to available prey.

Response of Timber Rattlesnakes to Commercial Logging Operations

ABSTRACT Forest management practices in the eastern United States directly impact large parcels of land that serve as habitat for timber rattlesnakes (Crotalus horridus). We assessed the behavioral response of timber rattlesnakes to commercial logging activities and the impact of such activities on a timber rattlesnake population in northcentral Pennsylvania. We radiotelemetrically monitored 67 individual snakes over periods of up to 4 years, marked and recaptured 306 snakes, and conducted search and survey efforts before, during, and after commercial logging operations on 3 timber sale parcels (totaling 154.2 ha). Location and timing of timber sales created the maximum opportunity for interaction of snakes with logging operations and with altered habitat. Observed logging-related mortality of snakes was low (<2% of the population/yr), but potential mortality could have reached 7%. Logging activity and resulting habitat changes did not alter behavior or movement patterns of telemetrically monitored snakes. Snakes with established activity ranges in timber sale areas continued to use these areas both during and after logging operations. Similarly, snakes with activity patterns that did not include timber sale areas did not alter their movement patterns to include such sites in the short-term. Timbering increased structural diversity of the habitat and, concurrently, diversity of habitat used by timber rattlesnakes increased. Our results suggest that the opportunity exists to develop forest management practices that provide timber products while limiting impacts on behavior and habitat use of timber rattlesnakes. To further reduce impacts to timber rattlesnake populations we recommend that management agencies require commercial logging contractors, sub-contractors, and field employees to adhere strictly to a policy that prohibits the intentional killing of rattlesnakes encountered during logging activities.

Genetic Structure of Timber Rattlesnake (Crotalus horridus) Populations: Physiographic Influences and Conservation Implications

The distribution and genetic structure of wildlife populations may be impacted by landscape features and anthropogenic factors. The role of these factors in the genetic relationships among Timber Rattlesnakes (Crotalus horridus) from 21 locations in Pennsylvania, New Jersey, and Virginia was investigated using microsatellite genetic markers. Evidence for null alleles was found in 8 of the 21 populations studied, with frequencies ranging from 0.018 to 0.185. However, the presence of null alleles appeared to have no effect on the interpretation of the patterns of genetic relationships among the populations studied. The analyses showed that the overall extent of genetic differentiation was consistent with isolation by distance; however, a substantial amount of among-groups variation could not be accounted for by geographic distance alone. Bayesian analysis (STRUCTURE), genetic distance analysis, and factorial correspondence analysis (FCA) all indicated that the sampled populations represented three genetic groups, which corresponded closely with physiographic regions. These three groups consisted of an Atlantic Coastal Plain group, an Appalachian Plateau group, and an Appalachian Ridge and Valley group. We recommend that these be considered as separate conservation management units (MUs) for C. horridus in Pennsylvania and New Jersey. Several potential barriers to gene flow were identified, including the Appalachian Mountains, several large rivers, and major roadways. The lowest levels of genetic variation were found in the highly isolated populations from the Atlantic Coastal Plain.

Behavioral Responses of a Dietary Specialist, the Queen Snake (Regina septemvittata), to Potential Chemoattractants Released by Its Prey

Abstract Queen Snakes (Regina septemvittata) are extreme dietary specialists, feeding nearly exclusively on freshly molted crayfish. To elucidate specific cues that mediate prey detection and foraging behavior in R. septemvittata, we examined the response of R. septemvittata and the dietary generalist Nerodia sipedon sipedon, to chemical compounds produced by crayfish during the molting cycle. Ingestively naive neonate snakes were presented with 20-hydroxyecdysone, ecdysone, methyl farnesoate, ponasterone A, xanthurenic acid, and distilled water. Their response was measured using a modification to the tongue-flick attack score. Regina septemvittata exhibited an elevated tongue-flicking response to ecdysone, whereas N. s. sipedon exhibited no differential responses to these same arthropod molting chemicals. In a second experiment, R. septemvittata showed a two-fold higher tongue-flicking response to intermolt crayfish extract that contained ecdysone than to intermolt crayfish extract alone, whereas N. s. sipedon demonstrated no differential response between these extracts. In a third experiment consisting of feeding trials, R. septemvittata was offered live intermolt crayfish with and without ecdysone. The presence of ecdysone increased the feeding scores of R. septemvittata. When ecdysone was present, crayfish were ingested in five of the seven trials, but when ecdysone was absent crayfish were not ingested in any trial. These results suggest that ecdysone may play a critical role in the interaction between R. septemvittata and their prey. With numerous stream contaminants known to imitate ecdysone and disrupt the arthropod molting cycle, this finding may have important implications for the conservation of R. septemvittata.

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.

Population Isolation and Genetic Subdivision of Timber Rattlesnakes (Crotalus horridus) in the New Jersey Pine Barrens

Abstract:  Timber Rattlesnakes, Crotalus horridus, are an endangered species in New Jersey, where high human population density places extraordinary pressures on natural populations. Disjunct populations are found in both the northern part of the state and a few scattered locations in the southern Pine Barrens. The Pine Barrens populations were previously shown to have reduced levels of genetic diversity compared to other populations in the Mid-Atlantic region. In this study, we used microsatellite DNA to examine the remaining six known C. horridus populations in the Pine Barrens and two in the northern part of the state. Bayesian analysis, genetic distance analysis, and factorial component analysis were performed, and the results indicated that the sampled populations represented four genetic subgroups, the two northern populations comprised one subgroup and the remaining six Pine Barrens populations comprised the other subgroups. Although there was evidence for isolation by distance among the Pine Barrens populations, geographic distance alone did not account for a substantial amount of among-group variation. The combined analyses implicated paved roads as primary isolating barriers between populations. Given their geographic isolation and reduced levels of genetic diversity, intensive efforts may be required to ensure the persistence of the behaviorally and genetically unique C. horridus populations of the New Jersey Pine Barrens.