Comparison of the Relative Abundance of Potential Prey to the Diet of the Louisiana Pine Snake (Pituophis ruthveni)

Abstract

Pituophis ruthveni (Louisiana Pine Snake) occurs in parts of western Louisiana and eastern Texas and was recently listed as a threatened species under the Endangered Species Act. It is considered a diet specialist because it mostly feeds upon Geomys breviceps (Baird's Pocket Gopher), which make up ∼75% of its estimated total prey biomass. Diet specialization is rare among vertebrates. One factor that can influence dietary diversity is the availability and abundance of prey items. To gain more insight on the Louisiana Pine Snake's diet, we sampled terrestrial and subterranean small mammals across 3 study sites within the range of this snake species in Louisiana to determine their relative abundance and availability. We compared these results to diet studies of the Louisiana Pine Snake to determine if any small mammal species were consumed more often than expected. The total of 59 small mammals captured consisted of Baird's Pocket Gopher, Sigmodon hispidus (Hispid Cotton Rat), Peromyscus spp. (deer mice), and Reithrodontomys spp. (harvest mice). Baird's Pocket Gopher had significantly higher relative abundances and biomass than terrestrial small mammals. When compared to proportions of actual consumed prey species, the Louisiana Pine Snake preyed upon Baird's Pocket Gopher significantly more than expected based on their availability in the environment. Finally, Chesson's prey selection index determined that the Louisiana Pine Snake positively selected Baird's Pocket Gopher, while the other species were either randomly or negatively selected. The results of this research provide some insight into the factors affecting the diet choices of the Louisiana Pine Snake.