Riparian brushrabbit

Classification:
Phylum Chordata,
Class Mammalia,
Order LAGOMORPHA,
Family LEPORIDAE,
GenusSylvilagus,
Species bachmani,
Subspecies riparia

Historical Distribution:
Historically, the riparian brush rabbit is believed to have been found in riparian forests along portions of the San Joaquin River and its tributaries on the Valley floor, from at least Stanislaus County to the Delta. One population estimate was about 110,000 individuals residing in this historic range.

Current Distribution:
Definitive information on former distribution is lacking, but it is believed that today the only known populations are confined to Caswell Memorial State Park on the Stanislaus River and along an over flow channel of the San Joaquin River. By the mid-1980s, the former range of the riparian brush rabbit had been reduced to a few small and widely scattered fragments, totaling about 2,100 hectares(5,189 acres). No other sightings of riparian brush rabbits outside the Park have been reported in over 40 years. The last population estimate was 213 to 312 individuals at Caswell MSP in January 1993. Other information suggests that the population size since 1997 is even lower.

The dramatic decline of the riparian brush rabbit began in the 1940s with the building of dams, constructed for irrigation and flood control, on the major rivers of the Central Valley. Protection from flooding resulted in conversion of floodplains to croplands and the consequent reduction and fragmentation of remaining riparian communities. The most serious problem, however has been the lack of suitable habitat above the level of regular floods where the animals could find food and cover for protection from weather and predators. Aside from the periodic threats from flooding, wildfire poses a major threat due to long-term fire suppression in the Park and the consequent increase in fuel from dead leaves, woody debris, and decadent, flammable shrubs. Other factors that could affect this population are diseases common to rabbits in California. Competition with the more fecund and agile desert cottontail potentially is another threat.