CDFW News

‘A Massive Win’: Rehabilitated Black Bears Thriving After Fall Releases

Mon, 08 Jun 2026 13:57:03 GMT

Five orphaned black bear cubs that were rehabilitated and released into northern California in November 2025 successfully hibernated through the winter and returned to the landscape this spring healthy and active, according to recent data reviewed by California Department of Fish and Wildlife (CDFW) scientists.

These bears were part of an experimental effort led by the department’s Wildlife Rehabilitation Program, in coordination with CDFW’s Game Conservation Program and North Central Region, to test the viability of releasing rehabilitated juvenile black bears back in the wild in the fall versus the typical spring release. This practice – which can be helpful in mitigating human-wildlife conflict – has been successful in other states but had yet to be tested in California.

All five bears were ear-tagged, microchipped and fitted with GPS collars for scientific study and individual identification. Based on collar data, all five bears successfully established dens, hibernated during the winter, and reemerged this spring back on the landscape.

“This is a massive win. These bears spent their first winter hibernating naturally in the wild as opposed to staying overwinter in a facility, which can be costly and difficult to do. It means less time in rehabilitation and less opportunity to get comfortable around humans,” said Dr. Heather Perry, CDFW’s Wildlife Rehabilitation Program Coordinator. “We were able to work together to release these healthy young animals back to the wild where they belong. It highlights the important and unique role of wildlife rehabilitators – and wildlife rehabilitation by its very definition – in the conservation of California’s native wildlife.”

The releases were made possible by CDFW’s wildlife rehabilitation partners with support from the CDFW Wildlife Health Lab and veterinary staff who provided health assessments prior to release. CDFW decided to test the fall bear releases after noting the success of fall releases in other western states, specifically Nevada and Washington.

“Bears are incredibly resilient. They have an innate behavior to find shelter when snow starts to accumulate on the ground,” said Alexia Ronning, CDFW Environmental Scientist and Tahoe bear specialist. “They teach us all the time that we need to trust their ability to survive on the landscape.”

The five bears include:

Two female siblings reported to CDFW as orphaned near Nevada City, Nevada County in May 2025. Both cubs were captured and taken to the Sonoma County Wildlife Rescue for rehabilitation then returned together to suitable habitat in Nevada County.

One male cub reported to CDFW as abandoned in South Lake Tahoe, El Dorado County in July 2025. The cub was captured and taken to Sonoma County Wildlife Rescue for rehabilitation then returned to suitable habitat in El Dorado County.

Three male siblings reported to CDFW as abandoned in Arnold, Calaveras County in July 2025. The cubs were captured and taken to the San Diego Humane Society’s Ramona Wildlife Center for rehabilitation. One sibling arrived sick and was humanely euthanized. The remaining two cubs were transferred to Sonoma County Wildlife Rescue then returned together to suitable habitat in Calaveras County.

CDFW provides year-round education, outreach and community support on living responsibly with black bears and recreating in bear country through its affiliations with the Tahoe Interagency Bear Team (TIBT) and BearWise. Preventing black bears from accessing trash, human food sources and other attractants is key to preventing human-bear conflicts.

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Media Contact:
Peter Tira, CDFW Communications, (916) 215-3858

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CDFW Image: A cluster of GPS points overlayed on satellite imagery over a three-month period in winter shows very little movement and indicates to CDFW biologists that the GPS-collared Calaveras County bear wearing the collar found a den and hibernated.

California Red-Legged Frog Recovery Reaches 10-Year Milestone in Yosemite

Thu, 07 May 2026 15:06:12 GMT

10,000 frogs released through multiagency conservation effort

The California red-legged frog, a federally threatened species absent from Yosemite National Park for decades, has made a significant comeback after 10 years of coordinated conservation work.

Partners marked the milestone today with the symbolic release of the program’s 10,000th frog in Yosemite Valley.

The recovery effort is led by the National Park Service in collaboration with U.S. Fish and Wildlife Service, the California Department of Fish and Wildlife, Yosemite Conservancy and San Francisco Zoo & Gardens.

“This milestone reflects years of focused work to restore a species that plays an important role in the park’s ecosystem,” said Rob Grasso, aquatic ecologist at Yosemite National Park. “After invasive bullfrogs eliminated red-legged frogs from the area decades ago, we removed those threats and created conditions for recovery. Today, multiple generations of frogs are established in Yosemite Valley.”

Invasive American bullfrogs, introduced to the park, drove the species’ decline. Elevated raccoon populations, fueled by open refuse sites that remained in use until the 1970s, also contributed to the loss. Park staff spent decades removing bullfrogs, while habitat improvements tied to the Merced River Plan restored wetlands, streambanks and river systems critical to the frog’s survival.

“Our partners have been essential to the recovery of the California red-legged frog,” said Kim Turner, acting field supervisor for the Sacramento Fish and Wildlife Office. “We appreciate the progress made over the past decade and remain committed to this collaborative effort.”

During the May 7 event, speakers will deliver remarks near Yosemite Falls before releasing several zoo-reared frogs, including the program’s symbolic 10,000th frog, nicknamed “Twain.”

“The California Department of Fish and Wildlife is proud to have assisted the recovery of California’s official state amphibian in Yosemite,” said Laura Patterson, amphibian and reptile conservation coordinator for the Department. “Grants administered by the Department, using funds approved by the voters of California, facilitated the habitat restoration necessary for the success of this recovery effort.”

A key component of the effort is a dedicated rearing facility established in San Francisco in 2016 through a partnership between the National Park Service and the San Francisco Zoological Society. At the facility, staff raise frogs from wild-collected eggs to one- and two-year-old juveniles in a controlled environment before releasing them into the park.

The program is supported by the Zoo-Park Partnership Program, facilitated by the Wildlife Restoration Foundation, and is considered a model for species recovery in California.

“When the program began in 2016, no California red-legged frogs remained in Yosemite Valley,” said Dr. Rochelle Stiles, director of field conservation at the San Francisco Zoo and Gardens. “Today, every frog in the valley traces back to this effort. Despite drought, severe winters and flooding, the population has proven resilient.”

This year, the zoo plans to release about 830 juvenile frogs into Yosemite while raising approximately 600 eggs for future release.

“Protecting vulnerable species helps preserve the park’s natural balance,” said Cassius Cash, president of Yosemite Conservancy. “This milestone shows what sustained collaboration can achieve.”

The effort also relied on private landowner Diane Buchholz of Garden Valley, Calif., who allowed researchers to collect frog eggs from her property.

The California red-legged frog gained national recognition in The Celebrated Jumping Frog of Calaveras County by Mark Twain. The species, the largest native frog in the western United States, grows 2 to 5 inches long and is known for its reddish underside and soft, short calls. It inhabits ponds, streams and wet meadows.

About the National Park Service Established in 1916, the National Park Service preserves America’s most treasured natural and cultural places for the enjoyment, education and inspiration of current and future generations. ;Learn more at nps.gov.

About the U.S. Fish and Wildlife Service The U.S. Fish and Wildlife Service works with others to conserve, protect and enhance fish, wildlife, plants and their habitats for the continuing benefit of the American people. For more information, visit www.fws.gov, or connect with us through any of these social media channels: Facebook, Instagram, X, LinkedIn, YouTube and Flickr.

About the California Department of Fish and Wildlife The California Department of Fish and Wildlife’s mission is to protect California's diverse fish, wildlife and plant resources, and the habitats upon which they depend, for their ecological values and enjoyment by the public today and for generations to come. For more information visit wildlife.ca.gov or follow CDFW on Facebook, Instagram, X and YouTube.

About San Francisco Zoo & Gardens Established in 1929, San Francisco Zoo & Gardens connects people to wildlife, inspires caring for nature and advances conservation action. An urban oasis, SF Zoo is home to nearly 1,500 exotic, endangered and rescued animals representing about 150 species. Located at the edge of the Pacific Ocean at Sloat Boulevard, the Zoo is open 365 days a year from 10 a.m. to 5 p.m. (4 p.m. in the winter). Visit www.sfzoo.org for more information.

About Yosemite Conservancy For more than 100 years, Yosemite Conservancy has supported the conservation of Yosemite’s natural and cultural resources and helped people develop a deeper relationship to the park. Thanks to generous donors, in recent years, the Conservancy has provided more than $180 million in grants to Yosemite for more than 950 projects. In 2026, we are providing $19 million in total support and funding around 60 new grants to the National Park Service for projects in the park. The Conservancy’s guided adventures and art classes, donor events, volunteer opportunities, wilderness services and bookstores help people from across the country and world connect with Yosemite. Learn more at yosemite.org.

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Media Contacts:
Yosemite National Park
U.S. Fish and Wildlife Service
Krysten Kellum, CDFW Communications, (916) 825-7120
Nancy Chan, San Francisco Zoo & Gardens, (415) 840-6065
Peter Bartelme, Yosemite Conservancy

CDFW Research Links California’s Nutria Invasion to Pacific Northwest Population

Tue, 07 Apr 2026 10:28:13 GMT

Study Also Informs Eradication Efforts, Offers Toolkit for Future Research Worldwide

Scientists with the Wildlife Genetics Research Unit at the California Department of Fish and Wildlife (CDFW) have completed a genomic study of nutria, an invasive South American rodent, linking their 2017 discovery in Merced County to a population in central Oregon. This was the first genomic study of the semi-aquatic pest species that is harmful to wetland habitats and agriculture and has challenged control efforts of land and wildlife managers worldwide for decades.

To identify the origins of nutria in California, CDFW research scientists compared DNA of invasive nutria populations around the world. This led to building a dataset showing the genetic similarity among nutria on a global scale that will serve as a toolkit for future research. The genetic data also give insight into how nutria populations spread across a landscape — information that will inform eradication efforts and development of management strategies.

“CDFW conducts sophisticated genetics research to improve management outcomes for California’s wildlife populations,” said CDFW Wildlife Genetics Research Lead Mike Buchalski. “The results of this study additionally will benefit future national and global genetic research on nutria.”

“Genetics allowed us to narrow down the most likely source of California’s nutria population and provide land and wildlife managers with information about how these animals are spreading across the landscape,” said CDFW Research Scientist Kristen Ahrens. “We have also created a global reference dataset that others can use to compare populations and trace invasion pathways.”

Nutria were introduced to countries all over the world to be raised for their pelts at the height of the fur trade in the late 19th and early 20th centuries, including in California. When that trade collapsed nutria were set free from fur farms, leading to a limited number of feral populations on the landscape, which seemingly failed to thrive. Localized nutria eradication efforts followed, and they were ultimately declared eradicated from California by the late 1970s.

There was no sign of nutria presence in the state until 2017 when a pregnant female was found in Merced County. Unlikely that nutria could have gone undetected since eradication in the 1970s, particularly given the rapid rate of reproduction and geographic spread observed following their discovery, CDFW went to work to assess genetic variation in past and present nutria populations in California to find the origin of this recent discovery.

To compare today’s nutria with those present before eradication, historical genetic data were essential. CDFW’s Ahrens located and sampled nutria skins and skulls housed in museums and universities across California, and one unexpected source in a taxidermy nutria found at the Butte County Weights and Measures Department office. Recovering DNA from decades-old specimens allowed direct comparison of past and present maternal lineages, providing critical insight into the origins of the current invasion.

CDFW’s Nutria Eradication Program team provided tissue samples for DNA sequencing of California’s current nutria population.

For broader comparison, Ahrens obtained tissue samples from federal and state wildlife management agencies for other nutria populations in the U.S. — Louisiana, Texas, Maryland, Virginia, Oregon and Washington. Ahrens was also able to tap into publicly archived sequenced DNA from invasive nutria in South Korea, Japan and Brazil.

Comparisons showed that nutria in California today are most genetically similar to populations in central Oregon. Historical California nutria represented multiple maternal lineages, based on analysis of the museum bone and taxidermy specimens. In contrast, today’s population traces back to a single lineage, also detected in historical samples, a pattern most consistent with a recent reintroduction rather than survival of the earlier, more diverse population.

Ultimately, the genetic research suggests California’s current nutria invasion was the result of intentional reintroduction, with the original source animals likely being transported from the central Oregon population, which is prohibited by Fish and Game Code section 2118 and Title 14, California Code of Regulations section 671. Eradication efforts are now costing the state about $5 million per year.

“This study supports our long-held belief that the current invasion is the result of reintroduction rather than explosive growth of a remnant, undetected population,” said Nutria Eradication Program Manager Valerie Cook. “While we can only speculate on the ‘reasoning’ behind the reintroduction of this incredibly destructive invasive species, these findings highlight the critical importance of biosecurity inspections aimed at preventing the importation and transportation of invasive plants and animals into and within California.”

CDFW’s Nutria Eradication Program has taken 7,841 nutria in California since 2017. Eradication efforts are underway across hundreds of thousands of acres of wetland and riparian habitat in California’s Sacramento-San Joaquin Delta and Central Valley, spanning from San Pablo Bay to Kings County. Visual observation surveys, motion-detection cameras and scat-detection dogs help CDFW’s eradication team detect nutria presence for subsequent trapping efforts.

Findings of the nutria genomic study will be another valuable tool for the CDFW Nutria Eradication Program. This study demonstrates how genetics can shed light on population structure and patterns of gene flow to better understand how nutria disperse across a landscape.

The nutria genomic research took place over the past five years and was funded by the California Department of Water Resources. Research was done in partnership with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

The recently published paper on the study, Population Genomic Insights Into Recent Nutria Invasion Dynamics, is available online.

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Media Contacts
Michael Buchalski, CDFW Wildlife Health Laboratory, (916) 508-1385
Krysten Kellum, CDFW Communications, (916) 825-7120

CDFW to Conduct Helicopter Capture and Collaring Efforts for Deer, Elk and Gray Wolves in Northern California

Mon, 29 Dec 2025 15:50:07 GMT

The California Department of Fish and Wildlife (CDFW) is initiating efforts in northern California to capture deer, elk and wolves by helicopter and outfit the animals with GPS collars.

Helicopter captures for deer and elk will be conducted in portions of Alameda, Colusa, Humboldt, Lake, Lassen, Modoc, Plumas, Santa Clara, Sierra, Siskiyou, Tehama and Trinity counties throughout the month of January 2026.

Capturing and collaring mule deer, tule, Roosevelt and Rocky Mountain elk improves CDFW’s understanding of ;species distribution, habitat use, abundance, migration patterns, recruitment rates and survival.

Capture teams will be targeting wolves in Siskiyou, Lassen and Tehama counties and potentially other uncollared packs or wolf groups in Modoc, Shasta and Plumas counties. Any captured wolves will be returned to the nearest suitable public land habitat after processing.

Deployed collars will transmit data to CDFW scientists daily for up to three years and provide detailed information about animal movements, habitat preferences and locations. For collared wolves specifically, CDFW will share animal location information with cattle and sheep producers with the goal of reducing negative interactions with the understanding GPS tracking collars do not transmit data in real-time. Wolf movement and location data will automatically feed into CDFW’s online Wolf Tracker mapping tool.

Wildlife capture operations will take place on lands managed by CDFW, the USDA Forest Service, the Bureau of Land Management as well as on private properties with permission from landowners. CDFW is grateful to the USDA Forest Service, BLM, timberland owners and other private parties for providing access to their lands for these wildlife capture efforts.

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Media Contact:
Peter Tira, CDFW Communications, (916) 215-3858

Scientific Surveys Show Continued Decline in White Sturgeon Population

Wed, 09 Jul 2025 16:11:28 GMT

Recent results from white sturgeon monitoring surveys by the California Department of Fish and Wildlife (CDFW) suggest the white sturgeon (Acipenser transmontanus) population has continued to decline. CDFW fisheries biologists now estimate there are approximately 6,500 white sturgeon between 40-60 inches long in California — down sharply from the previous estimate of approximately 30,000 fish in that size range, based on the 2016-2021 survey average.

There may be many reasons for the downward trend, including mortality from harmful algal blooms, poaching, past sport fishing harvest and poor river and Delta conditions.

In 2024, CDFW implemented a new method for surveying the white sturgeon population in collaboration with the Pacific States Marine Fisheries Commission and local sturgeon fishing guides. Surveys take place in the spring and fall from San Pablo Bay to Rio Vista and surrounding areas. The methods are based off white sturgeon surveys conducted in Oregon and Washington and modified for use in California. The study design has been peer-reviewed and is the most robust and comprehensive white sturgeon population monitoring survey ever conducted in California.

While CDFW’s efforts in 2024 established a new baseline of data, multiple years of this new survey approach are needed to confirm the findings and accurately track population trends.

The surveys utilize a “mark-recapture” technique combined with statistical analyses to estimate population size. Each spring, baited setlines (lines with multiple baited hooks) are used to capture sturgeon. The fish are then measured, scanned for existing tags, tagged if necessary, and then released. In the fall, the number of tagged sturgeon that are recaptured is compared to the number of untagged sturgeon caught, allowing scientists to estimate the overall population size.

In addition to providing an estimate of fish between 40-60 inches, the new survey method caught a greater size range of fish, allowing CDFW to estimate the abundance of a broader segment of the population than in the past. Based on the new methods, 19,000 white sturgeon between 10-87 inches fork length (the length from the tip of the snout to the fork in the tail) are estimated to be in California.

Based on historical surveys conducted by CDFW between 1954–2022, the number of white sturgeon in California has been in decline for many years. The species is currently a candidate for listing as threatened under the California Endangered Species Act (CESA) and receives full CESA protection while its status is reviewed. Sturgeon fishing is now limited to catch-and-release only with protective seasons, fishing areas and handling restrictions.

At its Aug. 13 meeting, the California Fish and Game Commission is expected to consider whether to continue recreational catch-and-release regulations for white sturgeon. These regulations have been discussed in public meetings with opportunity for public comment.

To read the full sturgeon survey report download the document. To learn more about conservation efforts for this prehistoric species, visit wildlife.ca.gov/Conserve-the-Sturg.

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Media Contacts:
Jay Rowan, CDFW Fisheries Branch, (916) 212-3164
Steve Gonzalez, CDFW Communications, (916) 804-1714