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

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-ce ntral 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, w as absent in the 1990s. Nine of the 11 taxa were similar in abundance acros s sampling periods. Juvenile Pituophis catenifer and Crotalus viridis incre ased dramatically in the 1990s; adult Pituophis catenifer declined, whereas adult Crotalus viridis increased. Analysis or these two taxa indicated tha t abundance along the transect was approximately similar in the 1970s and 1 990s: 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-t rade. Additional study will be necessary to assess the apparent stability o f this snake community. (C) 2000 Elsevier Science Ltd. All rights reserved.