The aquatic garter snake at Sibley Volcanic Regional Preserve, Oakland, CA.
Photo credit: Sarah Stierch.
Edgehouse et al. show that the common garter snake (Thamnophis sirtalis) and the aquatic garter snake (Thamnophis atratus) show a strong preference for amphibians and forces these snakes to exploit aquatic habitats. They investigate the aggressive behavior of T. sirtalis and the potential that this aggression displaces T. atratus from its preferred habitat. When individuals from either species were alone, they showed a complete preference for aquatic or near aquatic habitats. In contrast, when these species are together, T. sirtalis occupy the aquatic habitat and T. atratus occupy an area far removed from the water. They found Thamnophis sirtalis often physically force T. atratus from the aquatic habitat through repeated biting and other displays of aggression.
The spatial partitioning documented by the authors is likely a direct result of food availability and aggressive defense of the prey resource. The most abundant amphibian prey found in the snakes at the study site were California newt and the pacific treefrog.
Edgehouse M, Latta LC IV, Brodie ED III, Brodie ED Jr (2014) Interspecific Aggression and Habitat Partitioning in Garter Snakes. PLoS ONE 9(1): e86208. doi:10.1371/journal.pone.0086208