Ecology and conservation of rattlesnakes in sagebrush steppe ecosystems: Landscape disturbance, small mammal communities, and Great Basin rattlesnake reproduction

Widespread disturbance in sagebrush steppe is threatening many species including reptiles. Great Basin rattlesnakes (Crotalus oreganus lutosus) are capital breeding snakes that acquire energy over multiple years for reproduction. Disturbances may be influencing rattlesnake reproductive output by limiting the amount of energy they can acquire during the active season. The goal of my dissertation was to determine how disturbance influences reproduction in Great Basin rattlesnakes. Specific objectives include, (1) to document microgeographic variation in rattlesnake reproductive characteristics, (2) to determine if disturbance is related to reproduction indirectly through prey availability and/or the amount of potential foraging time, and (3) if local adaptation in growth has occurred in rattlesnake populations.; I sampled substrate, vegetation, small mammals, and operative temperatures and conducted mark-recapture, radio telemetry, and a common garden experiment on rattlesnakes. These studies occurred at three large overwintering complexes (Crater Butte, Cinder Butte, and Rattlesnake Cave) on the Idaho National Laboratory (INL).; My results suggest that patterns in landscape disturbance are indirectly influencing rattlesnake reproduction by altering prey availability. First, I found that the Crater Butte population had lower reproductive output due to lower body condition, slower growth, and lower fecundity than the other two populations. Second, I found that prey availability was lower at Crater Butte and in disturbed areas. Snakes using areas with lower prey availability made more linear movements and gained less weight. Weight gain in individually tracked snakes was correlated to prey availability. When making an overall comparison of the two sites, I found that Crater Butte had more landscape disturbance, lower prey availability, snakes moved more linearly, gained less weight, and had lower reproductive output relative to Rattlesnake Cave. I found no evidence that potential foraging times or local adaptation were influencing the observed variation in reproductive output between Crater Butte and Rattlesnake Cave.; Results from these studies suggest that disturbance is indirectly influencing predator populations by altering prey availability. This result is consistent with studies of snakes in other ecosystems and studies of other small mammal predators in the sagebrush steppe. These findings have applied implications for the conservation of sagebrush steppe, predators, and rattlesnakes.