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Little Bunny Blues

Even with the recent discovery of a new population in the upper Delta, the tiny riparian brush rabbit (sylvilagus bachmani riparius) remains the most endangered mammal in the state, say experts on the species. Once numbering in the tens of thousands (possibly hundreds of thousands at highs in its population cycles), the rabbit inhabited riparian thickets along the main northern valley rivers - the Merced, San Joaquin, Stanislaus, and Tuolumne - as well as along major channels in the San Joaquin River delta. Now, most of the remaining rabbits (less than a few dozen), are restricted to the Stanislaus River in Caswell Memorial Park, says BurRec's Rosalie Faubian. Flooding of the park in 1997 probably reduced the number of rabbits living there as well, she says. To protect the newly found upper Delta population, officials refused to disclose its location.

The riparian subspecies, smaller and with lighter coloration than ordinary brush rabbits, weighs only 1.5 pounds, and has evolved in wet areas supporting riparian vegetation like blackberry brambles, willows, and wild roses, says Faubian. Because the rivers have been channelized, flood levels are higher than they would normally be, says Daniel Williams of California State University Stanislaus, and cultivated farmland extends to and often within the levees. "This means the animals have no refuge from floodwater and are forced onto the levees or adjacent farmland where there is no cover from predators or adverse weather," says Williams. Ordinarily, the rabbits will not leave the riparian thickets, another characteristic that differentiates them from other brush rabbits.

The rabbits were proposed for federal listing almost two years ago, but the decision to list has been stalled over an internal dispute about whether or not to designate critical habitat. The rabbit has been listed as endangered by the state since 1994.

Contact: Rosalie Faubian (559)487.5138 or Daniel Williams (209)667.3477

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