Lots of movement, little progress: a review of reptile home range literature

Shelter Distribution and Type Affect Space Use of a Desert Reptile

Animal home ranges derive from the distribution of resources across the landscape. For example, home ranges of most tortoise species in the United States revolve around networks of burrows. However, human disturbances that damage shelters can decrease habitat suitability, individual survival, and population persistence. We investigated effects of burrow distribution and availability on space use of the Sonoran Desert Tortoise Gopherus morafkai at two populations with different habitat structures to determine the extent to which habitat capacity is defined by factors subject to management, such as vegetation, relative to more permanent features such as rock shelters. We also demonstrated the superiority of autocorrelated kernel density estimation, illustrating flawed conclusions that could arise from the use of traditional home-range estimators. Home-range size increased with the number of available burrows at both sites. At the Florence Military Reservation (FMR), with numerous caliche caves and few rock burrows, larger home ranges effectively compensated for one third the burrow density as that of Sugarloaf Mountain, which predominantly featured rock burrows. Female tortoises had smaller home ranges than males despite having similar burrow densities. Females revisited individual burrows more often than males at Sugarloaf, which may relate to female use of preferred nesting sites; however, lower availability led males to revisit burrows at similar rates as females at FMR. Pairs of tortoises at FMR shared 72% more burrows than pairs at Sugarloaf, and pairs of females shared 33% fewer burrows than female-male pairs across both sites. Space and burrow use at FMR and Sugarloaf are consistent with predictions of how animals choose patches for their home ranges in ways that are optimal with respect to spatially distributed resources. Populations largely reliant on pallets or soil burrows may be more subject to declines due to anthropogenic impacts from grazing or off-highway vehicle use or due to increasing temperatures.

Episodic Gregariousness Leads to Level-Dependent Core Habitats: A Case Study in Eastern Copperheads (Agkistrodon contortrix)

Characterizing the complex relationships between animals and their habitats is essential for effective wildlife conservation and management. Wildlife-habitat selection is influenced by multiple life-history requirements, which act over varying spatial and temporal scales, and result in dispersion patterns that can differ across ecological levels. For example, sites that attract intense communal use (e.g., hibernacula and communal basking sites) are often a subset of the habitats required by individuals for survival. Despite the conservation importance of both individually and communally significant habitats, snake habitat models rarely incorporate information about both individual and population-level activity. We used 4 years of radiotelemetry data from eastern copperheads (Agkistrodon contortrix) to evaluate the presence of multilevel spatial habitat responses and whether they revealed conservation-relevant information. We related individual and population space use intensity to underlying habitat covariates to determine whether predictors of copperhead spatial activity were level-dependent, and whether individual core habitats differed by sex and reproductive state. Copperheads' episodic gregariousness resulted in spatial and environmental separation between individual and communal core habitats. Population-level use was greatest in rocky, forested habitats associated with winter brumation and spring basking, whereas individual-level use was greatest in open habitats with woody debris associated with foraging and reproductive behaviors. Male core habitats were open and thickly vegetated while those of females were moderately forested, with gravid female core habitats containing ample woody debris. Our findings demonstrate that multilevel spatial patterns carry conservation-relevant information about snake habitat relationships. We suspect that behaviors leading to multilevel spatial patterns exist in many wildlife species whose individual spatial activities overlap around shared resources.

Tracking the little ones: use of fluorescent powder to follow a leaf litter lizard (Coleodactylus meridionalis, Squamata: Sphaerodactylidae) in the Atlantic Forest of southern Bahia, Brazil

The ecology of movement is an expanding area, marked by the diversity of analytical methods and protocols, which enables this integrative reading. We investigated movement ecology aspects of Coleodactylus meridionalis in southern Bahia, northeastern Brazil, using fluorescent powder with mineral oil to track individuals. We monitored 69 individuals of C. meridionalis that walked an average distance of 148 cm in 2h. We identified this movement as foraging due to the orientation of the step sequence and microenvironments used. We find no significant differences between walking distance and weight. However, we found a decrease in activity over the follow-up period. Most of the lizard's movements were directed north, while south, east, and west were followed equally. The individuals stayed predominantly on the ground (leaf litter), but it was possible to observe the use of other surfaces, such as trunks and burrows on the ground. Therefore, we studied the movement in three dimensions (ground height, distance traveled, and orientation of steps). We observed the lizard's foraging, one of the most common and least investigated movements in small lizards like C. meridionalis. This involves not only the species' activity schedule but other intrinsic and extrinsic factors that shape the movement decisions of individuals.

Climate change-induced shifts in survival and size of the worlds' northernmost oviparous snake: A 68-year study

Because of their dependence on ambient temperature ectothermic animals can serve as sentinels of conservation problems related to global warming. Reptiles in temperate areas are especially well suited to study such effects, as their annual and daily activity patterns directly depend on ambient temperature. This study is based on annual data spanning 68 years from a fringe population of Grass Snakes (Natrix natrix), which is the world's northernmost oviparous (egg-laying) reptile, and known to be constrained by temperature for reproduction, morphology, and behavior. Mark-recapture analyses showed that survival probability was generally higher in males than in females, and that it increased with body length. Body condition (scaled mass index) and body length increased over time, indicative of a longer annual activity period. Monthly survival was generally higher during winter (i.e., hibernation) than over the summer season. Summer survival increased over time, whilst winter survival decreased, especially during recent decades. Winter survival was lower when annual maximum snow depth was less than 15 cm, implying a negative effect of milder winters with less insulating snow cover. Our study demonstrates long-term shifts in body length, body condition and seasonal survival associated with a warming climate. Although the seasonal changes in survival ran in opposite directions and though changes were small in absolute terms, the trends did not cancel out, but total annual survival decreased. We conclude that effects of a warming climate can be diverse and pose a threat for thermophilic species in temperate regions, and that future studies should consider survival change by season, preferably in a long-term approach.

Home range ecology of Indian rock pythons (Python molurus) in Sathyamangalam and Mudumalai Tiger Reserves, Tamil Nadu, Southern India

The Indian rock pythons (Python molurus) are classified as a near-threatened snake species by the International Union for the Conservation of Nature and Natural Resources (IUCN); they are native to the Indian subcontinent and have experienced population declines caused primarily by poaching and habitat loss. We hand-captured the 14 rock pythons from villages, agricultural lands, and core forests to examine the species' home ranges. We later released/translocated them in different kilometer ranges at the Tiger Reserves. From December 2018 to December 2020, we obtained 401 radio-telemetry locations, with an average tracking duration of (444 ± 212 days), and a mean of 29 ± SD 16 data points per individual. We quantified home ranges and measured morphometric and ecological factors (sex, body size, and location) associated with intraspecific differences in home range size. We analyzed the home ranges of rock pythons using Auto correlated Kernel Density Estimates (AKDE). AKDEs can account for the auto-correlated nature of animal movement data and mitigate against biases stemming from inconsistent tracking time lags. Home range size varied from 1.4 ha to 8.1 km2 and averaged 4.2 km2. Differences in home range sizes could not be connected to body mass. Initial indications suggest that rock python home ranges are larger than other pythons.

Sex-specific movement ecology of the shortest-lived tetrapod during the mating season

Sex-specific reproductive strategies are shaped by the distribution of potential mates in space and time. Labord’s chameleon (Furcifer labordi) from southwestern Madagascar is the shortest-lived tetrapod whose life-time mating opportunities are restricted to a few weeks. Given that these chameleons grow to sexual maturity within about three months and that all individuals die soon after breeding, their mating strategies should be adapted to these temporal constraints. The reproductive tactics of this or any other Malagasy chameleon species have not been studied, however. Radio-tracking and observations of 21 females and 18 males revealed that females exhibit high site fidelity, move small cumulative and linear distances, have low corresponding dispersal ratios and small occurrence distributions. In contrast, males moved larger distances in less predictable fashion, resulting in dispersal ratios and occurrence distributions 7–14 times larger than those of females, and males also had greater ranges of their vertical distribution. Despite synchronous hatching, males exhibited substantial inter-individual variation in body mass and snout-vent length that was significantly greater than in females, but apparently unrelated to their spatial tactics. Females mated with up to 6 individually-known mates, but frequent encounters with unmarked individuals indicate that much higher number of matings may be common, as are damaging fights among males. Thus, unlike perennial chameleons, F. labordi males do not seem to maintain and defend territories. Instead, they invest vastly more time and energy into locomotion for their body size than other species. Pronounced variation in key somatic traits may hint at the existence of alternative reproductive tactics, but its causes and consequences require further study. This first preliminary study of the mating system of a Malagasy chameleon indicates that, as in other semelparous tetrapods, accelerated life histories are tied to a mating system with intense contest and scramble competition among males.

Malayan kraits (Bungarus candidus) show affinity to anthropogenic structures in a human dominated landscape

Animal movement can impact human-wildlife conflict by influencing encounter and detection rates. We assess the movement and space use of the highly venomous and medically important Malayan krait (Bungarus candidus) on a suburban university campus. We radio-tracked 14 kraits for an average of 114 days (min: 19, max: 218), during which we located individuals an average of 106 times (min: 21, max: 229) each. Most individuals displayed some level of attraction to buildings (n = 10) and natural areas (n = 12); we identified a similar unambiguous pattern of attraction to buildings and natural areas at the population level (of our sample). Snakes remained in shelter sites for long durations (max: 94 days) and revisited sites on average every 15.45 days. Over 50% of locations were within human settlements and 37.1% were associated with buildings. We found generally seasonal patterns of activity, with higher activity in wet seasons, and lower activity in the hot season. These results show frequent proximity between Malayan kraits and humans at the university; thereby, suggesting a near constant potential for human-wildlife conflict. Despite the fact that no snakebites from this species occurred at the university during our study period, substantial education and awareness training should be considered to ensure continued coexistence on campus.

Artificial shelters provide suitable thermal habitat for a cold-blooded animal

Human activities such as urbanization often has negative affects wildlife. However, urbanization can also be beneficial to some animals by providing suitable microhabitats. To test the impact of urbanization on cold-blooded animals, we first conducted a snake survey at a national nature reserve (Xianghai natural reserve) and an adjacent tourist bird park (Red-crowned Crane Park). We show high presence of Elaphe dione in the tourist park even with high human activities and predator population (the endangered, red-crowned crane, Grus japonensis). We then radio-tracked 20 individuals of E. dione, set seven camera traps, and recorded the temperature of the snakes and artificial structures in Crane Park to document their space use, activity, and thermal preference, respectively. Our results show E. dione preferred to use artificial facilities to shelter from their predators and for thermoregulation. The high number of rats from the camera traps indicate abundant prey items. Overall, E. dione appears to be adapted to modified habitats and may expand population size at the current study site.

Promoting co-existence between humans and venomous snakes through increasing the herpetological knowledge base

Snakebite incidence at least partly depends on the biology of the snakes involved. However, studies of snake biology have been largely neglected in favour of anthropic factors, with the exception of taxonomy, which has been recognised for some decades to affect the design of antivenoms. Despite this, within-species venom variation and the unpredictability of the correlation with antivenom cross-reactivity has continued to be problematic. Meanwhile, other aspects of snake biology, including behaviour, spatial ecology and activity patterns, distribution, and population demography, which can contribute to snakebite mitigation and prevention, remain underfunded and understudied. Here, we review the literature relevant to these aspects of snakebite and illustrate how demographic, spatial, and behavioural studies can improve our understanding of why snakebites occur and provide evidence for prevention strategies. We identify the large gaps that remain to be filled and urge that, in the future, data and relevant metadata be shared openly via public data repositories so that studies can be properly replicated and data used in future meta-analyses.