Mesocarnivores affect hispid cotton rat (Sigmodon hispidus) body mass

Abstract

Predator communities are changing worldwide: large carnivores are declining while mesocarnivores (medium-sized mammalian predators) are increasing in number and ecological influence. Predator choice of prey is not random and different predators select prey with different characteristics. Changes in predator communities can change predation patterns experienced by prey. Little is known about how mesocarnivore communities influence prey morphology. We used 14 years of mark-recapture data to investigate how mesocarnivore exclusion affected body mass of hispid cotton rats (Sigmodon hispidus). Finding adult male cotton rats were 9% heavier with mesocarnivore exclusion, we developed hypotheses to explain this observation. Greater adult male body mass in exclosures resulted from: (1) a non-significant trend of increased survival of large males, (2) faster juvenile male growth during the fall and a similar non-significant trend among adult males, and (3) spatial partitioning by size among males. Taxa-specific predation rates (i.e., rates of predation by snakes, raptors, or mesocarnivores) did not differ among male body mass classes. Mesocarnivores disproportionately preyed on large females while raptors targeted small females, but female body mass was not influenced by mesocarnivore exclusion. Changes in predator communities can result in multiple small effects that collectively result in large differences in prey morphology.

Unique histological features of the tail skin of cotton rat (Sigmodon hispidus) related to caudal autotomy

“…On the other hand, the laboratory cotton rat survives up to 23 months ( Faith et al, 1977 ; Curlee and Cooper, 2012 ). Although the cause of the shorter lifespan in wild cotton rats is still not fully elucidated, predation by carnivorous birds and mammals ( Morris and Conner, 2019 ) and high susceptibility to pathogenic viruses ( Ehlen et al, 2016 ) might cause a shorter lifespan in the wild than in the laboratory. It is likely that the cotton rat acquired caudal autotomy during its evolution to minimize the loss of individuals, as reported in other rodents performing autotomy ( Shargal et al, 1999 ).…”