Effect of resource supplementation on female Western Rattlesnake postpartum movement

Abstract

Resource availability plays an important factor in an animal's life history by affecting growth and reproduction and influencing behaviours such as movement and thermoregulation. Female rattlesnakes in northern climes face shortened active seasons limiting the time available to replenish lost reserves from reproduction. Consequently, this leads to slower growth rates, small litters, and infrequent reproduction in these populations. With these challenges, it has been assumed postpartum rattlesnakes in these regions should return to their hibernacula immediately following parturition. However, our previous study revealed different tactics of postpartum movements by females across several study sites. To examine the relationship between resource availability and these movements, we experimentally supplemented resources (mice or mice injected with water) to free-ranging pregnant Western Rattlesnakes ( Crotalus oreganus Holbrook, 1840) at three sites in British Columbia, Canada, during 2019. We examined body condition and movement of snakes, finding that pregnant rattlesnakes consumed supplemented resources until late parturition and had significantly higher postpartum body condition than controls. Contrary to our expectations, increased access to resources ad libitum did not significantly halt or alter postpartum movements away from hibernacula. These results suggest that resource availability influences certain life-history traits such as body condition but not others like postpartum movement.