Long-term shifts in snake populations: a California site revisited

Abstract

The distribution and abundance of snakes along a transect across an ecotone from an oak woodland-chaparral mosaic to a more arid grassland in north-central California was surveyed. Of 11 taxa documented in the 1970s, 10 were observed in the 1990s; only Tantilla planiceps, a rare form in the 1970s, was absent in the 1990s. Nine of the 11 taxa were similar in abundance across sampling periods. Juvenile Pituophis catenifer and Crotalus viridis increased dramatically in the 1990s; adult Pituophis catenifer declined, whereas adult Crotalus viridis increased. Analysis of these two taxa indicated that abundance along the transect was approximately similar in the 1970s and 1990s; snakes were most abundant in the ecotone. Snake abundance was similar for the 1970s and 1990s in spite of increased road traffic, continued off-road vehicle use and sheep and cattle grazing, and collecting for the pet-trade. Additional study will be necessary to assess the apparent stability of this snake community.