Variation in behavior drives multiscale responses to habitat conditions in timber rattlesnakes (Crotalus horridus)

Abstract

Variations in both the behavior of wildlife and the scale at which the environment most influences the space use of wild animals (i.e., scale of effect) are critical, but often overlooked in habitat selection modeling. Ecologists have proposed that biological responses happening over longer time frames are influenced by environmental variables at larger spatial scales, but this has rarely been empirically tested. Here, we hypothesized that long-term patterns of behavior (i.e. lasting multiple weeks to months) would be associated with larger scales of effect than more sporadic behaviors. We predicted site use by 43 radio-telemetered timber rattlesnakes (Crotalus horridus) exhibiting four distinct, time-varying behaviors (foraging, digestion, ecdysis, and gestation) using remotely-sensed environmental variables related to forest structure and landscape topography. Among sites used by snakes, warmer temperatures and higher levels of forest disturbance were predictive of behaviors dependent on thermoregulation including gestation and ecdysis while more moderate temperatures and drier, more oak-dominated sites were predictive of foraging. Long-term behaviors were associated with larger spatial scales, supporting our hypothesis that the scale at which habitat selection occurs is linked to the temporal scale of relevant behaviors. Management recommendations based on single-scale models of habitat use that do not account for fine-scale variations in behavior may obscure the importance of potentially limiting habitat features needed for infrequent behaviors that are critically important for growth and reproduction of this and related species.

Prey‐driven behavioral habitat use in a low‐energy ambush predator

“…Hoffman et al ( 2020 ) found that site selection associated with foraging, ecdysis, digestion, and gestation in this TRS population could be described by many of the landscape variables used in this study (Table 1 ) at behavior‐specific spatial scales (5–105 m). Foraging was negatively associated with temperature and a landscape moisture gradient (indicating drier soils and oak‐dominated areas), and these conditions did not describe site use for other behaviors (Hoffman et al, 2020 ). Importantly, TRS foraging was associated with cooler temperatures than sites associated with other behavioral states, suggesting that foraging behavior may be decoupled from snake thermoregulatory needs (Hoffman et al, 2020 ).…”

“…Foraging was negatively associated with temperature and a landscape moisture gradient (indicating drier soils and oak‐dominated areas), and these conditions did not describe site use for other behaviors (Hoffman et al, 2020 ). Importantly, TRS foraging was associated with cooler temperatures than sites associated with other behavioral states, suggesting that foraging behavior may be decoupled from snake thermoregulatory needs (Hoffman et al, 2020 ). Our collective findings that TRS foraging is associated with greater prey availability but also suboptimal conditions for thermoregulation demonstrate that snakes preferentially seek out prey‐rich areas to forage.…”

“…As part of an ongoing study, we radio‐tracked 37 adult TRS (21 males and 16 non‐gravid females) between 2016 and 2019 to obtain behavior‐specific spatial data (further described in Hoffman et al, 2020 ). We relocated snakes 1–3 times per week and classified behavioral state (e.g., ecdysis, resting, foraging) upon relocation, resulting in 522 observed foraging locations.…”