The elusive riparian brush rabbit — once thought extinct — is continuing its battle for survival.
Thanks to a wide array of projects from efforts to boost their population at Caswell Memorial State Park where the largest concentration of the rabbit subspecies was known to exist for years south of Manteca and west of Ripon to the creation of the 2,100-acre Dos Rios Preserve by the River Partners at the confluence of the Tuolumne and San Joaquin rivers the brush rabbits are estimated to now number in the low thousands.
The January 1997 floods were literally and figuratively a watershed event for the survival of the rabbit that resembles the desert cottontail but is smaller with a darker, grassy brown coat minus a black tip on the ear as well as having a smaller and a less conspicuous tail.
Prior to the flood 30 years ago that inundated Caswell State Park as well as 70 square miles between Manteca and Tracy the state park unit along the Stanislaus River was home to an estimated 200 to 300 brush rabbits. It was the largest known concentration in the wild of the endangered species.
The reason was simple. Caswell is the largest stand of remaining riparian as roughly 97 percent had been destroyed by the creation of levees and farms. Riparian woodlands create the ideal cover for thick ground foliage the brush rabbits thrive in.
A year after the flood only one of the rabbits that as an adult reach 11 to 14 in length and weigh between 1 and 1.8 pounds was spotted at Caswell State Park.
Combined efforts from the Endangered Species Recovery Program at California State University Stanislaus in Turlock, the US Fish and Wildfire Service, California Fish and Wildlife, the non-profit River Partners as well as the US Geological Survey have helped somewhat reverse the brush rabbit’s fortunes.
The riparian brush rabbit was detected in Paradise Cut some 20 plus years ago during a biological survey that was part of the environmental vetting process for the 15,001-home River Islands at Lathrop planned community.
Several dozen were captured, tagged and intermingled with the population at Caswell State Park. Brush rabbits were then returned to Paradise Cut where a 1,000-acre preserve has been set aside.
And while there haven’t been recent sightings in Paradise Cut it is likely because of their elusive nature.
The rabbits rarely stray more than several feet from where they burrow as well as find shelter and food among wild rose bushes, wild grapevines, as well as blackberry and similar vegetation. While green clover is their favorite food they also feast on grass, bark, vines, leaves, and other plants. When flood work starts in Paradise Cut the developers of River Islands — Cambay Group — has already agreed to create numerous mounds within the preserve to provide high ground for the rabbits that are more conducive to their survival during flood waters than seeking higher ground on levees.
The brush rabbits were also reintroduced in 2005 at the Gallo wine family owned Faith Ranch abutting the riverside in Stanislaus County.
River Partners, which joined efforts to restore habitat to preserve a brush rabbit population at the San Joaquin Wildlife Refuge in the early 2000s, started their own brush rabbit restoration preserve at Dos Rios Ranch in 2014.
Having preserves on either side of the river to reconnect remnants of the ecology system are seen as key for the brush rabbit to expand its range as the years go by.
It is the same reason why River Islands did work along the San Joaquin River in a bid to create a better connection between Paradise Cut and other brush rabbit habitat.
The reintroduction of rabbits from captive breeding programs have helped push estimated numbers in the wild from 200 to 300 three decades ago to more than 2,000 today.
That is based partially on the fact 252 brush rabbits were tagged between August and November in 2020 at Dos Rios leading to the projection there are more than 2,000 brush rabbits in the wild.
Thirty years ago the brush rabbit’s range that once was believed to have been farther south along the San Joaquin River and boasted a population in excess of 110,000 was limited to South San Joaquin County. Their range now includes part of Stanislaus County.
While the brush rabbits are prolific between January and May with females being able to have up to four litters a year and giving birth to three or four young rabbits in each litter, the survival rate for those born in the wild are 1 in 6.
Although they have plenty of natural predators in the wild feral cats are believed to be the deadliest foes when it comes to their survival.
And while brush rabbits that are one of eight rabbit sub-species unique to California seldom venture more than a few feet from their favorite brush covering, they have been known during floods to climb trees.
To contact Dennis Wyatt, email dwyatt@mantecabulletin.com
