Science Spotlight

For residents of Humboldt and Del Norte counties, the majestic Roosevelt elk is a common sight. Although Roosevelt numbers were dwindling in California by the 1920s, conservative management strategies and limited hunting opportunities have helped them to rebound. Today, researchers have identified more than 20 distinct groups of elk in these two counties, many of which consist of well over 50 animals.

This conservation success story doesn’t come without a downside, though. Elk require large amounts of food to survive, and they tend to graze where food is most plentiful – often in agricultural areas and residential neighborhoods, where they cause damage to crops, landscaping, fencing and other private property.

Partly in response to rising concerns about property damage caused by the Humboldt and Del Norte herds, CDFW scientists are working on a wide-ranging, long-term study of Roosevelt elk population size and growth, herd movements, habitat use, disease and causes of mortality. The project, which is a collaborative effort with researchers from Humboldt State University, will collect critical baseline information about the animals that will help CDFW develop more robust and efficient methods for monitoring the herds, set future hunt quotas, inform local agencies about elk management and manage depredation issues. CDFW initiated this project in 2016 and expects to continue data collection efforts through 2018.

Tracking and studying one of the largest mammals in California is a much more complex undertaking than one might think. Roosevelt elk herds are wide-ranging and tend to graze in areas that are not easily accessible. Traditionally, CDFW relied on aerial surveys to monitor population trends of big game species such as elk, but such surveys are only feasible in a small portion of northwestern California because visibility is limited by steep terrain and dense vegetation. Ground surveys have similar constraints and are further limited by the small amount of occupied habitat that can be easily accessed from roads.

Given these constraints, CDFW scientists are employing multiple survey methodologies for the current study. Different techniques will be used in different habitat types. For example, in hard-to-reach areas, trail camera footage will be compared to visual surveys and used to collect herd composition data and estimate population size. Estimates will also be derived from analyzing the DNA contained in elk droppings.

CDFW also monitors the movement of the Roosevelt elk via electronic collars. There are currently 20 collared elk in coastal Del Norte and northern Humboldt counties and researchers hope to extend this project into central Humboldt County this winter, with plans to collar as many as 30 additional elk. Captured animals are also marked with ear tags, which allow for individual identification.

These survey efforts, and similar efforts elsewhere in the North Coast Roosevelt Elk Management Unit (EMU), are outlined in California’s Draft Elk Conservation and Management Plan, which is available for public review and comment through Monday, January 29. The plan provides guidance and direction to help set priorities for elk management efforts statewide.

CDFW photo: Environmental Scientist Carrington Hilson monitors a Roosevelt elk during a survey of the population.

The tilapia skin is visible on the bottom of the bear's paw.


Veterinarians perform an ultrasound to check on the progress of the second bear's pregnancy.


Acupuncture needles assist with pain management.


After placing the second bear, the team moved the first bear to another location where another man-made den awaited.


CDFW staff work together to build a makeshift den for a soft release in Los Padres National Forest. A soft release involves putting the bear in a den to simulate hibernation, and leaving it to wake up on its own.

Two talented veterinarians, an environmental scientist and several dedicated staff members at the CDFW Wildlife Investigations Lab recently put their heads and their resources together to help heal a pair of adult bears that were badly burned in the Thomas Fire. The bears, which were treated at the same time as a young mountain lion with similar, less severe burn injuries, were released back to the wild last Thursday, after several weeks of intensive – and unusual – care.

CDFW Senior Wildlife Veterinarian Dr. Deana Clifford was acting manager of the Wildlife Investigations Lab in Rancho Cordova when the first bear – an adult female weighing about 200 pounds – was captured inside of a backyard aviary in the Ojai area on December 9. With CDFW Environmental Scientist Christine Thompson coordinating, CDFW Wildlife Officer Jacob Coombs darted the bear and local veterinarian Dr. Duane Tom evaluated its injured paws and overall condition. Thompson then conferred with Clifford, who determined the bear might have a chance at recovery if treated quickly. The bear was put into a trailer for the seven-hour transport to Rancho Cordova, where Clifford was waiting.

By the time the bear arrived, Clifford had already reached out to Dr. Jamie Peyton, Chief of Integrative Medicine at the UC Davis Veterinary Teaching Hospital, for help. Weeks earlier, Peyton, who works mostly on domestic animals, had mentioned to Clifford in passing that she had a particular interest in animal burns, and would be interested in helping wildlife if the chance ever arose.

Peyton created a homemade burn salve for the bears’ paws, and a process for sterilizing tilapia skin. Fish skin, which contains collagen, is often used by doctors in Brazil to bandage human burns. The technique is not yet approved by the Food and Drug Administration for use in the United States, and had not been tried on veterinary patients.

To help keep the tilapia skin in place, Peyton cut pieces to exactly match the size of the bear’s paws and then sutured them over the wounds while the bear was under anesthesia. Additional temporary wrappings, including rice paper and corn husks, were added, with the intention of stretching out the amount of time it would take for the animal to chew down to the fish skin bandage. “We expected the outer wrapping to eventually come off, but we hoped the tilapia would keep steady pressure on the wounds and serve as an artificial skin long enough to speed healing of the wounds underneath,” Peyton said. She also used acupuncture to aid the bear with pain management.

The original plan was for Peyton to come to the lab weekly to check on the bear’s progress. But within just a few weeks, two more burn patients arrived from the Thomas Fire. A second adult female bear, found relatively close to where the first one was found, was brought to the lab by Thompson on December 22. And on December 23, the young mountain lion arrived from Santa Paula. The experimental tilapia treatment was extended to the two newcomers as well.

Of the three animals, the mountain lion’s injuries were the least severe. Because of his young age, he was earmarked for placement in a wildlife rescue facility. The two bears were in much worse condition, with oozing wounds and, in some cases, paw pads that were completely burned off. But because the bears were older and stronger, the veterinarians hoped to return them to the wild if their injuries could be healed.

To complicate matters further, on December 28, during a routine burn treatment, Clifford’s team performed an ultrasound on each bear, and found that the second bear was pregnant. The quest to heal the mother-to-be was now a race against time.

“That was a game changer for us, because we knew it wouldn’t be ideal for her to give birth in confinement,” Clifford said. “We aren’t really set up to have a birth at the lab holding facilities, and we knew there was a high probability that she could reject the cub, due to all the stress she was under. We needed to get her back into the wild as quickly as possible.”

While Clifford and Peyton continued to focus on healing the animals’ injuries, Thompson started scouting out potential release locations. Since both bears needed to be transported back to Southern California, it was decided to try to return them at the same time – albeit not exactly in the same location – in order to make the best use of staff time and resources.

Both bears’ original habitat had been destroyed by fire, so Thompson scouted for two new locations that fit several parameters. The bears needed to be close to their home range, but not within the burn area, and near ample food and water sources. She also wanted to keep them as far away from each other as possible. “A lot of wildlife habitat was destroyed by the fire, and there are already a lot of displaced animals roaming around,” Thompson said. “So there’s a good chance that whatever location we choose is already occupied by other bears, but only they know exactly where that designated territory is. The best we can do is make an educated guess, and place them as deep into wild lands as possible.”

Taking the rapidly changing winter weather reports into careful consideration, the team chose Wednesday, January 17, as the target date to get on the road. That morning, Peyton came to the Wildlife Investigations Lab one last time and both bears were immobilized for a final treatment for their feet. Then the bears were placed into separate transport trailers for the long journey home. Simultaneously, in the Los Padres National Forest, Thompson and Tom spent the day digging dirt and moving logs to create a winter den for each bear.

“At this time of the year, most bears have established dens for the winter, but since these bears won’t have time to create a den, we hope to improve their chances of survival by creating a den for them so they have a home base and shelter right away,” Clifford explained.

The team arrived late Wednesday night, and both staff and bears were hosted overnight by the Ventura County Sheriff’s Department. Early on the morning of January 18, Clifford, Thompson, Coombs, Tom and their team drove the bears deep into the forest for the final leg of their journey. One at a time, each bear was sedated and carefully placed into her den, while the team finished constructing a shelter around the slumbering animal. The bears are about five miles apart, as the crow flies, and each is wearing a satellite collar so CDFW can monitor her movements and survival post-release. Staff also placed trail cameras near each den.

“We’re really hopeful that these novel treatments accelerated the healing for these bears and provided them the best odds of survival,” Clifford said. “It’s especially good to know that we’ve maximized the odds of survival for the cub on the way. We don’t know exactly when it will be born, but hopefully we’ll be able to monitor the movements of the mother via satellite, and that will give us an indication of how things are going.”

For Clifford, the entire experience wasn’t simply about saving the lives of two bears. The bigger picture involves the body of knowledge the experimental treatment provided – both to the Wildlife Investigations Lab team and to the UC Davis Veterinary Teaching Hospital.

“This treatment has the potential to be used successfully on all kind of burn patients, both domestic and wild,” Clifford said. “For us, at the Wildlife Investigations Lab, it’s been an invaluable experience because California’s changing climate means that we’re likely to see more wild animals impacted by catastrophic wildfires. By better understanding what resources are needed to care for injured wildlife and what treatment techniques increase healing speed, we can make the most informed treatment decisions, reduce animals’ time in captivity and provide guidance to other facilities caring for burned animals.”

CDFW photos. For more, please see CDFW’s Flickr photo album: Thomas Fire Bears.

Top photo: The first bear rests in her holding enclosure after her treatment is finished. The outer wrapping on her feet (made of corn husks) will delay her efforts to chew off the tilapia skin bandages underneath.

Staff of several wildlife agencies carry light-footed Ridgway’s rails (previously known as light-footed clapper rails) to Batiquitos Lagoon Ecological Reserve.


A light-footed Ridgway’s rail is banded before release into Batiquitos Lagoon Ecological Reserve.

The Ridgway’s rail is a grayish-brown, chicken-sized bird with a long, downward curving bill and a conspicuous whitish rump. Previously known as the clapper rail, the species name was changed in 2014 to honor ornithologist Robert Ridgway. Three subspecies of Ridgway’s rail are resident in California, all of which depend on mudflats or very shallow water (wetland habitat) where there is both forage and taller plant material to provide cover at high tide. They rely on marsh plants such as cordgrass and pickleweed for breeding and feeding.

One subspecies, the light-footed Ridgway’s rail, was once abundant in the Southern California wetlands, but fell to near extinction in the 1980s as their historical habitats were displaced by housing developments. Today, they have a chance to repopulate, buoyed by recent wetland restoration projects by the California Department of Fish and Wildlife (CDFW) and “Team Rail,” a group that has been dedicated to the recovery of this federal- and state-listed marsh bird for more than a decade.

Team Rail is comprised of scientific staff from CDFW, the U.S. Fish and Wildlife Service (USFWS), the U.S. Navy, three zoological breeding centers (SeaWorld San Diego, the San Diego Zoo Safari Park, and the Living Coast Discovery Center) and the Huntington Beach Wetlands Conservancy. Thanks to their efforts, the 2017 rail population reached 514 pairs in the wild. Each rail release is a step closer to achieving the 1985 Light-Footed Clapper Rail Recovery Plan objective of having 800 breeding pairs in California.

Most recently, five light-footed Ridgway’s rails were released into the Batiquitos Lagoon Ecological Reserve in San Diego County. This release consisted of two mated pairs and three offspring produced by one of the pairs. Three of the adults are retired breeders from the zoological breeding program and are part of a rotation plan to reintroduce retired breeders back into the wild. The release of these individuals will contribute genetic diversity to this highly endangered marsh bird population. Rails bred in zoological facilities were released into Batiquitos Lagoon in 2004 and 2005 (eight rails each year), in 2013 (six rails), 2014 (12 rails), and 2015 (seven rails).

“Given that State Ecological Reserves are set aside for the conservation of threatened, rare and endangered species, and rail releases are targeted for wetlands with small subpopulations (fewer than 50 breeding pairs), Batiquitos Lagoon is an ideal location for the release of Ridgway’s rails,” explained CDFW Senior Environmental Scientist (Specialist) Nancy Frost. “For over a decade, CDFW has supported numerous research and monitoring projects for this species, and we are proud to be a partner in their recovery.”

The state-owned Batiquitos Lagoon is managed by CDFW and is one of the few remaining tidal wetlands on the Southern California coast. Located in the city of Carlsbad, it consists of 543 acres with a drainage basin of about 55,000 acres. It is home to several threatened and endangered birds, insects, plants, fish and mammals and is also designated as a State Marine Conservation Area under the Marine Life Protection Act.

Top photo: A light-footed Ridgway’s rail flies away after being released at Batiquitos Lagoon Ecological Reserve in San Diego County.

Kerstin Wasson is leading the Olympia oyster restoration at Elkhorn Slough. Kerstin Wasson photo.


Scientists are working hard so that a new generation of Olympia oysters may one day line the mudflats at the Elkhorn Slough Reserve.


Volunteers Ken Pollak and Celeste Stanik join Dr. Chela Zabin to improve the native oyster habitat at Elkhorn Slough. Kerstin Wasson photo.


Suspended gaper clam shells hang in aerated laboratory tanks, home to what scientists hope will be a new generation of Olympia oysters at the Elkhorn Slough Reserve.


Graduate student Dan Gossard, at CSU’s Moss Landing Marine Laboratories, shows off one of the clam shell “mobiles” on which the Olympia oyster larvae will attach when suspended in aerated tanks.


Kerstin Wasson points out Olympia oysters along the banks of the Elkhorn Slough Ecological Reserve in Monterey County.

For the first time in California history, scientists are turning to shellfish farming techniques to restore native oyster populations.

The groundbreaking research is taking place with Olympia oysters at CDFW’s Elkhorn Slough National Estuarine Research Reserve in Monterey County, in partnership with the California State University’s nearby Moss Landing Marine Laboratories and its new Center for Aquaculture.

Olympia oysters and other shellfish were once so abundant at Elkhorn Slough that Native Americans living there had multiple processing centers along the estuary’s banks to handle their harvest. Olympia oysters have disappeared altogether from many places along the California coast and their numbers at Elkhorn Slough have dwindled so low – estimated today at just a few thousand oysters – that scientists fear they may no longer be able to reproduce in the wild. Not since 2012, they say, have Elkhorn Slough’s wild oysters produced any offspring.

A combination of factors is believed to have caused the population drop over time, including poor water quality because of agricultural runoff from nearby farms and alterations to the landscape and tidal flow from generations of farming and other human activity prior to the area becoming protected in a series of conservation purchases beginning in 1971. An infusion of freshwater from last year’s rainy winter caused a severe oyster die-off and spurred biologists into action.

“This is an iconic species in our estuary in danger of disappearing,” said Kerstin Wasson, Research Coordinator at Elkhorn Slough, where she has worked for 17 years with funding from the National Oceanic and Atmospheric Administration (NOAA), the federal partner in the Elkhorn Slough Reserve. “These oysters fed native people here for 7,000 years.”

In late August, dozens of Olympia oysters were gathered and brought to the Moss Landing Marine Laboratories, where 20 spawned successfully. A few hundred thousand of their microscopic offspring are now swimming in large, circular laboratory tanks and attaching themselves to gaper clam shells suspended on fishing line from the top of the tanks. The clam shells bearing young oysters will be bound together into makeshift reefs and returned to Elkhorn Slough early in 2018 to bolster the native population.

The research is being led by a small group of scientists, including Wasson and graduate student Dan Gossard with funding provided by the Palo Alto-based Anthropocene Institute. These are uncharted waters for California scientists, however, and a major assist is coming from the aquaculture industry itself. Peter Hain of the Monterey Abalone Company has worked closely with the two researchers to set up the laboratory facility for the Olympia oysters and help with their care and feeding.

Due partly to their small size – an individual Olympia oyster is about the size of a 50-cent coin – and slow growth, Olympia oysters hold little appeal and little potential profit for most commercial oyster farmers who focus on larger Pacific varieties, many native to Japan. Taylor Shellfish Farms in Washington State is the only known commercial producer of Olympia oysters.

Wasson welcomes interest and support from aquaculture and hopes growers might one day add the native oyster to their operations. She believes even a niche commercial market for Olympia oysters could have positive implications for wild populations, enhancing recruitment, broadening scientific knowledge and a general appreciation for the native mollusk by the public.

Other efforts to save wild oyster populations in California and elsewhere have focused on building jetty-like artificial reefs constructed from oyster shell contained in plastic mesh.

Wasson prefers that more natural materials be used as part of the oyster restoration efforts underway at Elkhorn Slough, creating small clusters of oysters rising above the mudflats.

“I want this place to look like it did 200 or even 2,000 years ago,” she said.

Top photo: A huge influx of fresh water during winter 2017 resulted in an Olympia oyster die-off and spurred biologists into action.

A California red-legged frog sits motionless at the edge of McClure pond at the Sparling Ranch Conservation Bank. Photo by Ashley Spratt/USFWS


McClure pond is one of the most productive California red-legged frog ponds at the Sparling Ranch Conservation Bank. Like many of those on Sparling Ranch, it was named after the family who homesteaded in site in the late 1800s. Photo by Ashley Spratt/USFWS

Since the mid-1980s, California has been using a system of conservation and mitigation banking to protect valuable natural resources and critical habitat for fish, wildlife and plants. These banks are generally large, connected, ecologically meaningful areas of preserved, restored, enhanced or constructed habitat (for example, wetlands) that are set aside for the express purpose of providing mitigation for project impacts. Conservation banks provide mitigation for impacts to listed species and habitats, while wetland mitigation banks primarily provide mitigation for wetland impacts. Together, they serve to prevent inadequate, fragmented reserves that can result when mitigation projects are carried out individually.

Banks work by establishing credits for sensitive species or habitats found on a given site. These credits can then be sold to developers or other project proponents who need to meet permitting requirements or are otherwise required to compensate for environmental impacts. For those parties needing to mitigate for project impacts, banks serve to streamline the regulatory process by providing a pre-established mitigation site that the regulating state and federal agencies have already confirmed will provide adequate and appropriate mitigation for certain habitats or species. By mitigating at a bank, project proponents can avoid the time and cost of searching for a suitable mitigation site and protecting it in perpetuity themselves.

In order for the banking system to be effective, state and federal agencies must work closely together to align processes and practices. Since 1993, CDFW has been participating in the planning, review, approval, establishment, monitoring and oversight of 81 banks statewide. Other agencies that typically participate in the regulation and approval of conservation banks include the U.S. Army Corps of Engineers (USACE), U.S. Environmental Protection Agency (USEPA), Natural Resources Conservation Service (NRCS), U.S. Fish and Wildlife Service (USFWS) and the National Oceanic and Atmospheric Administration National Marine Fisheries Service (NOAA NMFS).

To read more about one of these successful partnerships, please visit USFWS’ newsroom.

Learn more about CDFW’s Conservation and Mitigation Banking program, on our website.

All photos courtesy of U.S. Fish and Wildlife Service.

Top photo: A herd of cattle graze atop a hillside at Sparling Ranch near Hollister, Calif. Photo by Ashley Spratt/USFWS.