Weather Whiplash Impacts All of California, Wildlife Included

Rescuing Endangered Riparian Brush Rabbits During Winter Flooding

Extreme weather causes low-lying areas near rivers to flood, inundating the habitat of endangered riparian brush rabbits and San Joaquin River desert cottontails (pictured). U.S. Fish and Wildlife Service staff at the San Joaquin River National Wildlife Refuge near Modesto are leading a rescue effort with assistance from River Partners, the California Department of Fish and Wildlife, and Oakland Zoo to relocate the rabbits to safety. Photo: Alejandro Alegria, USFWS

In California, the wettest winter in recent history shattered snow records and caused levees to overtop. A series of 31 atmospheric rivers between October and March caused dangerous flooding across the state. In the San Joaquin Valley, Tulare Lake has reemerged from the ancient lakebed, flooding towns and farmland. After a record-setting period of drought, the climate pendulum swung in the opposite direction.

All of that water has forced some people living near rivers to evacuate their homes. However, wildlife, such as the endangered riparian brush rabbit, don’t always have the luxury of evacuating to higher ground.

At the San Joaquin River National Wildlife Refuge near Modesto, River Partners’ allies at the U.S. Fish and Wildlife Service are leading a rescue operation to save endangered riparian brush rabbits from this year’s extreme floods.

Over the last 20 years, River Partners has restored thousands of acres of habitat within the rabbit’s range, including at the Refuge and our neighboring Dos Rios Ranch Preserve, where some of the stranded rabbits are being relocated to safety.

Riparian brush rabbit estimated historical and current range. One of California’s most endangered mammals, this map shows the estimated historical range shown is a coarse representation of potential historical distribution based on pre-1900 land cover (California State University Chico 2003, spacial dataset). The current range is based on occurrence point data. Source: Map and Species Status Assessment for the Riparian Brush Rabbit, June 2020 by US Fish and Wildlife Service, Sacramento Fish and Wildlife Office.

“We’re running out of places the rabbits can live that aren’t flooded,” says River Partners Restoration Ecologist Haley Mirts.

This small, adorable rabbit is native to the dense riparian forests along California’s Central Valley. Since the mid-1800s, 95% of their habitat has been lost—that’s like losing 95% of their housing market. So, when the waters rise, the rabbits have very limited options on where they can move to. Their habitat has been fragmented and redeveloped for cities, agriculture, and other human activities. They currently only reside in one area in the entire world, in the San Joaquin Valley.

A Wet Winter Puts the Riparian Brush Rabbit at Risk

At the San Joaquin River National Wildlife Refuge near Modesto, where an estimated 1,000 to 2,000 rabbits live, nearly 300 rabbits have been rescued and relocated to higher ground since January, as floodwaters engorged by the nearby San Joaquin and Tuolumne rivers and water poured into rabbit habitat.

Partners assisting the effort include River Partners, the California Department of Fish and Wildlife, and Oakland Zoo.

“We kayak and boat around, looking for rabbits in trees, placing traps in areas that will soon be underwater and moving any trapped rabbits to higher ground and restored areas,” says San Luis National Wildlife Refuge Complex Wildlife Biologist Fumika Takahashi.

U.S. Fish and Wildlife Service Wildlife Biologist Fumika Takahashi and Biological Science Technician Dylan Hilts prepare to rescue stranded riparian brush rabbits at the San Joaquin River National Wildlife Refuge during winter flooding. Photo: USFWS

Takahashi continues, “It’s an emotional experience seeing their habitats be completely underwater. Seeing rabbits floating on logs waiting to die. You know they have survived floods before, and they certainly bounced back. But it’s incredible to think that they were able to make it.”

Legacy of Restoring Habitat Lifelines

River Partners has worked with refuge staff for more than a decade to restore rabbit habitat and give rabbits somewhere to go when floodwaters rise, both at the refuge and River Partners’ Dos Rios Ranch Preserve located across the Tuolumne River from the refuge. These “bunny berms,” as Takahashi refers to them, are elevated areas including levees planted with dense foliage to provide plenty of forage and shelter from predators for the rabbits. Rabbits are being relocated to these berms, both at the Refuge and at Dos Rios.

A bunny berm (elevated area, right) at River Partners’ Dos Rios Ranch Preserve, located across the Tuolumne River from the San Joaquin River National Wildlife Refuge. This restored habitat provides a crucial haven for riparian brush rabbits during flood events.

“River Partners has done a lot of tree planting,” says Takahashi. “To see those efforts benefit the rabbits directly in this flood is really cool. The habitat was there and ready for them.”

With climate change, flooding along the San Joaquin Valley rivers is expected to occur more frequently and be more damaging, and Takahashi emphasized the importance of learning from each flood to continue improving restoration efforts. During 2017 flooding, for example, rabbits were stranded on small islands of habitat for so long that they ate through the available food source. Since then, River Partners and the refuge partnered to plant more plant species on bunny berms to increase rabbit forage.

Riparian brush rabbits seek shelter on levees and other elevated areas during floods. As floodwaters rise, their habitat and food sources become limited, leaving them vulnerable to predators. Restoration efforts like the “bunny berms” River Partners restores create elevated corridors of habitat to help them survive natural disasters such as flooding.

These Rabbits Can’t Catch a Break

To make matters worse, riparian brush rabbits face another major threat to their survival: a deadly, highly contagious disease known as rabbit hemorrhagic disease.

“The rabbit hemorrhagic disease has thrown another hardball at the rabbit, one more issue they’ve had to overcome,” says San Joaquin River National Wildlife Refuge Manager Eric Hopson.

Partners have been working since the disease first found its way to North America in 2020 to vaccinate riparian brush rabbits in the San Joaquin Valley to give them a fighting chance for survival as the disease spread west and north from New Mexico. The virus spreads between domestic and wild rabbit populations and is fatal in about 90% of cases.

Fumika Takahashi administering a vaccine to a riparian brush rabbit to protect against often-deadly rabbit hemorrhagic disease. In addition to restoring degraded habitat, vaccination is a key strategy to ensure these endangered rabbits continue not only hang on, but thrive. Photo: USFWS

Luckily, partners were able to vaccinate a portion of the riparian brush rabbit population before the disease spread to the San Joaquin River National Wildlife Refuge and neighboring Dos Rios Ranch Preserve in May 2022.This preemptive action helped them from being wiped out entirely.

This year’s flood rescues provide an opportunity for staff to give the life-saving vaccine to the rescued rabbits and test rabbits for the disease.

“We’ve captured and relocated 286 rabbits so far during the floods. Each of those were also vaccinated,” says Takahashi. “It’s been crazy, a crazy busy time.”

San Joaquin River national Wildlife Refuge staff in boats and kayaks trying to grab rabbits that escaped floodwaters by climbing into trees. The rescued rabbits will all be tested and vaccinated before release to prevent the spread of the deadly rabbit hemorrhagic disease. Photo: USFWS

Though the challenges facing these rabbits are great, there is an incredible team of people working tirelessly on multiple strategies to provide recovery lifelines. Restoring and expanding their habitat and vaccinations are two major strategies to give them a fighting chance.

“The riparian brush rabbit is a resilient species,” says Hopson. “Their reproductive rate is high for rabbits. We have seen the populations bounce back in prior years after these fires and floods. We’re hopeful.”