Riparian Brush Rabbit Recovery
On November 28, 2001, one of our recovery partners, the Endangered Species Recovery Program, started captively breeding riparian brush rabbits to help their young survive to adulthood. The species is listed as endangered because it has declined to only a few individuals in the wild.
Riparian Brush Rabbit FAQs
What is the riparian brush rabbit?
The riparian brush rabbit (Sylvilagus bachmani riparius) is a small cottontail, one of eight subspecies of brush rabbits native to California.
How can I distinguish it from other rabbits?
The riparian subspecies of brush rabbit can be distinguished by its relatively pale color, gray sides and darker back. When viewed from above, its cheeks protrude outward rather than being straight or concave, as in the other subspecies.
Brush rabbits can be distinguished from desert cottontails by their smaller, inconspicuous tail and uniformly colored ears (i.e., no black tips).
Where do these rabbits live?
They live in riparian oak forests with a dense understory of wild roses, grapes and blackberries. They have small home ranges and seldom move more than a few feet from cover. We believe they used to live along the San Joaquin River and its tributaries on the valley floor.
Until recently, only one population was known to remain. This population is at Caswell Memorial State Park on the Stanislaus River. In 2005, we established a population on the Faith Ranch, which is owned by the wine-making Gallo family.
What do they eat?
They eat green clover, bark and leaves, grasses and vines.
How many rabbits are there?
We are not sure. In 1993 an estimated 200-300 riparian brush rabbits inhabited Caswell State Park. After severe flooding in the winter of 1997 only one rabbit was trapped during field surveys. While we know population numbers have their ups and downs in their population numbers, we found these poor trapping results alarming.
Since 1997 rabbits have been found in the Sacramento-San Joaquin Delta. We believe they survived the flooding by climbing up a railroad embankment. Although this is fantastic news, the threats to the rabbit remain.
Why is the riparian brush rabbit in trouble?
More than 90 percent of the Central Valley's riparian forests no longer exist, eliminating this special habitat for various species, including the riparian brush rabbit.
A variety of human-caused actions eliminated and modified the rivers and riparian forests. Damming rivers, constructing levees, and urban, commercial and agricultural development all took their toll.
Wildfire, disease, predation from native and nonnative species, flooding and rodenticides also continue to threaten this small California native.
What has the Service done to save the riparian brush rabbit?
When we realized that the flooding had wiped out most of the rabbits, we went into action to prevent this species from going extinct.
- We listed it as endangered under the endangered species act. This provides the species with protection from harm, harassment or killing.
- Because the ultimate goal of the Endangered Species Act is the recovery of listed species, we included the riparian brush rabbit in the Recovery plan for the upland species of the San Joaquin Valley, California, September 30. 1998 (PDF 36MB). Recovery plans are road maps for the recovery of a species. They include land protection, research and management of the species.
What is being done right now?
The following projects are underway:
- Caswell Memorial State Park is enhancing conditions for the rabbits by reducing wildfires, controlling predators such as domestic cats, minimizing recreational impacts, restoring habitat, and planning expansion of the park.
- On November 28, 2001, one of our recovery partners, the Endangered Species Recovery Program, started bringing wild riparian brush rabbits into a controlled propagation (captive breeding) setting to enhance the chances of their young surviving to adulthood. They are now releasing rabbits back into the wild.
- We are working with private land owners to restore habitat within the historic range of the species to prepare for reintroduction using captively bred rabbits.
- We are exploring ways to reduce the effects of flooding on the riparian brush rabbit through the construction of safe areas (refugia) above flood level or vegetating existing flood control levees.
- We are also researching ways to reduce threats, improve reintroduction techniques and monitoring success, and create ideal habitats.
But why do we need to help rabbits breed?!
Unlike other cottontails that may breed year round, riparian brush rabbits only breed between January and May. Females give birth to 3-4 babies in each litter and 3-4 litters a year are possible.
Only 1 out of 6 young typically survive long enough to breed. Most of the young rabbits are killed by predators, especially feral cats. Captive breeding provides protection of those young during their most vulnerable age. These young will start new populations in restored habitat and possibly beef up existing populations.