Science Spotlight

Some of the 160 people who assisted Fish and Wildlife with it's March 1 desert bighorn sheep survey. CDFW photo.


Charles and Nicole Lozano of Chino Hills using binoculars and a spotting scope to locate sheep. CDFW photo.


The San Gabriel Mountains, north of Ontario, where the sheep survey took place. CDFW photo.

The San Gabriel Mountains, north of Ontario, are a spectacular location for those who enjoy steep hikes and beautiful scenery. But one Sunday each year, those mountains are visited by people with a more specific agenda. They’re there to assist environmental scientists from the California Department of Fish and Wildlife in determining the number of desert bighorn sheep living there.

On March 1, 2020, about 160 volunteers gathered near the rugged terrain for the annual sheep count. Their goal was to use spotting scopes and binoculars to locate sheep, and determine and record their gender and approximate age. The volunteers attended a mandatory training session the night before in which CDFW staff briefed them on the purpose, counting techniques and best gear and supplies to bring for what can be a long day in tough elements. And as it turned out, March 1 was the one day in a stretch of about 20 that included a forecast of rain, and the forecasters nailed it. Between the fluctuating poor conditions – including a steady rain, low clouds, strong winds and even hail – nearly every volunteer struck out on being able to locate any sheep.

Fortunately, the annual count also includes an aerial survey the day before the boots-on-the-ground effort, and the weather was cooperative on Feb. 29. Eight CDFW employees took turns that Saturday flying in a Bell 407 helicopter over the locations where they’d likely find the sheep groups. Flights were limited to 2.5 hours before refueling was necessary. The crew of three on each flight was responsible for taking notes and guiding the pilot, using a handheld GPS to drop a waypoint at each observed sheep location, and capturing the animals with camera gear. The doors of the aircraft were removed to improve visibility for the spotters.

CDFW Senior Wildlife Biologist and survey coordinator Jeff Villepique said a key element of the effort is determining the health of the younger animals.

“One of the things we look at is how many lambs from last year have survived to this year,” said Villepique. “We did get some decent numbers that will help us determine the recruitment ratio and give an indication that the population is growing and doing well.”

When CDFW first started conducting these counts in 1979, the desert bighorn sheep in the San Gabriels numbered about 740. That dropped to fewer than 200 in the late ‘90s, and currently the population is back up to about 400.  Villepique said the numbers rise and fall based on food availability, habitat loss, weather patterns and the history of wildfires.

One group that enthusiastically supports the survey is the Society for the Conservation of Bighorn Sheep. Volunteer Debbie Miller Marschke has joined the effort multiple times, and despite the lousy weather conditions, was happy to be out in the mountains once again.

“When you get out in the environment and you’re with positive people, it’s not a wasted day, it’s a memorable day,” Miller Marschke said, smiling as she braved the downpour. “If I stayed home, I wouldn’t remember what I did a month later. I’m going to remember this day all year long.”

Environmental Scientist Laura Cockrell records the weight of a wild turkey at Little Dry Creek prior to banding.


Wild turkeys banded in 2019 and 2020 are given one traditional, butt-end band on one leg and one rivet band on the other.


Environmental Scientist Laura Cockrell shows off the supply of butt-end bands prior to banding.

Turkey hunters in parts of Butte and Glenn counties who are skilled and lucky enough to bag a tom this spring may be in for a pleasant surprise: Their bird may be sporting some jewelry – a band on each leg.

Since early February, CDFW biologists at the Upper Butte Basin Wildlife Area – supported by the National Wild Turkey Federation (NWTF) – have been busy trapping and double-banding wild turkeys at the wildlife area’s Howard Slough and Little Dry Creek units. So far this year, some 45 turkeys have been banded, which include toms, hens and young males known as “jakes.”

The staff and volunteers have just about a month and a half to trap and band all the wild turkeys they can between the close of the waterfowl hunting season and the start of the spring wild turkey season in mid-March. It’s part of an innovative research effort aimed at better understanding the characteristics, growth rates, habitat use, range and abundance of the growing population of wild turkeys using the wildlife area.

Bird bands long have been an important research tool for biologists and considered a prize among many hunters who are allowed to keep them after reporting the band information. The Upper Butte Basin turkey banding project is the only one of its kind in the state, making those turkey bands a rare commodity and a valuable potential data source.

In addition to the banding, the turkeys are weighed, sexed and measured at various points before being released.

The wild turkey study began at the wildlife area in 2015 along with the launch of limited spring wild turkey hunts there. NWTF helped secure grant funding to start the hunt program and initiate the research effort. The funds came from the sale of upland game bird hunting validations and stamps required of upland game bird hunters.

“We thought it would be great to start getting an abundance estimate for the turkeys that we do have out here to make sure that we weren’t harming the population through the hunt program and also to see how much hunter opportunity we could potentially utilize,” said Kevin Vella, NWTF’s district biologist for California, Nevada, Oregon and Washington.

The spring wild turkey hunt program has been so successful and popular over its short history funding for the program and its research component will continue under CDFW’s general budget moving forward.

“I think Howard Slough especially offers some of the best turkey hunting I’ve seen anywhere,” said Upper Butte Basin Wildlife Area Manager Tim Hermansen. “Certainly, youth hunters have an excellent opportunity out here.”

Spring turkey hunts at both the Howard Slough and Little Dry Creek units are limited to lottery drawings through CDFW’s website in order to ensure an uncrowded, high-quality hunting experience. The hunter quota and the turkey harvest both have grown over the years along with the local turkey population. Hunter success ranged from 30 to 60 percent during the 2019 spring season but reached 100 percent for the youth hunt at Howard Slough in 2018.

Back to those double-banded birds.

Although 101 turkeys were banded at the wildlife area between 2015 and 2019, only three banded turkeys have been reported by hunters. That leads biologists to believe most of the turkeys have been prying off the traditional, “butt-end” bird bands, which have two edges that butt evenly together when clamped on.

The NWTF has since supplied Upper Butte Basin with rivet bands that are made of a harder metal and riveted closed when attached. The turkeys banded in 2019 and 2020 now receive a butt-end bird band on one leg and a rivet band on the other. Any of those harvested birds wearing a single rivet band will confirm suspicions that the birds have been prying off the butt-end bands.

“That’s the downside of doing any kind of novel research,” explained Laura Cockrell, a CDFW environmental scientist based at the Upper Butte Basin. “You only have your own mistakes to learn from.”

CDFW Photos. Top Photo: Upper Butte Basin Wildlife Area Manager Tim Hermansen releases a wild turkey after banding as Fish and Wildlife Technician Derek Schiewek and Seasonal Aid John Davis look on.

Media Contact:
Peter Tira, CDFW Communications, (916) 322-8908

Logan Weyand, left, a veterinary student form Washington State University, and Drew Trausch, a scientific aid with CDFW’s Big Game Program, help capture and collar a cow Roosevelt elk in Humboldt County this past fall. CDFW photo by Shwn Fresz.


CDFW crews work quickly to tag and collar a tranquilized cow elk in Humboldt County. CDFW photo by George Harse.


Sporting ear tags and a GPS tracking collar, a cow Roosevelt elk returns to heavy timber after being sedated. CDFW photo by Andrew Trausch.


Ear tags provide biologists with visual identification of Roosevelt elk study animals while GPS tracking collars can provide years worth of detailed date on movement and habitat preferences. CDFW photo by George Harse.

State biologists are now learning a great deal about California’s largest land mammal.

Roosevelt elk are one of three subspecies of elk native to California, joining the tule elk (the smallest of the three) and the Rocky Mountain elk. While a bull Rocky Mountain elk will have larger and more impressive antlers, the Roosevelt elk bests it in body mass. A bull Rocky Mountain elk can reach 700 pounds while a bull Roosevelt can exceed 1,000 pounds.

Despite their massive size and majestic appearance, Roosevelt elk have proved an elusive research subject because of the dense forests they inhabit. Aerial surveying and trapping – standard tools for counting and collaring deer, elk and bighorn sheep in more open parts of the state – can be challenging for Roosevelt elk moving in and out of heavy coastal timber.

While deer often can be darted and tranquilized using a biologist’s truck as cover, Roosevelt elk are more wary and vehicle-shy, often requiring a lengthy stalk and serious hunting skills to get within the 50-yard effective range of a dart gun. In some cases, it can take more than 100 hours to capture and collar an individual Roosevelt elk.

In an attempt to close the knowledge gap, CDFW recently initiated one of the largest Roosevelt elk capture and collaring efforts in state history, targeting a population of Roosevelt elk living along the U.S. 101 corridor in Humboldt and Del Norte counties. The effort is part of an ongoing study that began in 2016, explained Carrington Hilson, CDFW’s lead elk research biologist on the north coast. The study will continue through 2025.

Since November, Hilson and her colleagues have affixed GPS tracking collars on 24 cow Roosevelt elk in Humboldt and Del Norte counties to monitor their movements and migrations. CDFW biologists plan to collar another 14 cows this winter.

Several ancillary projects – estimating populations using fecal DNA, looking at calf survival and understanding habitat use – are also underway at Humboldt State University in Arcata in coordination with CDFW that will add to the state’s body of knowledge.

A few factors are driving the research interest, explained Kristin Denryter, the Sacramento-based senior environmental scientist who oversees CDFW’s Elk and Pronghorn Antelope Program. The first is an increasing number of human-elk conflicts along the U.S. 101 corridor that include vehicle collisions, property damage and agricultural losses suffered by north coast farmers and ranchers.

The second driver is technology. Advances in GPS tracking collars make them an increasingly valuable research tool. The new elk collars will record data every six hours over the life of the study and deliver that information daily to CDFW biologists.

Lastly, there is the California Essential Habitat Connectivity Project and U.S. Department of the Interior Secretarial Order 3362 (SO 3362).

Signed in 2018, SO 3362 directs federal agencies to work with California and other western state wildlife agencies to improve the quality of big-game winter range habitat and migration corridors on federal land. The order provided funding for CDFW to acquire the 38 GPS tracking collars and accelerate its research efforts. The collar data will improve understanding of movement and habitat use to inform habitat enhancement on public lands as well as help guide development of potential crossing structures to not only improve habitat connectivity but to also improve public safety by reducing vehicle collisions. CDFW has partnered with CalTrans on improving connectivity as part of the California Essential Habitat Connectivity Project.

A Roosevelt elk stakeholder group made up of CDFW representatives, tribal interests, farmers, ranchers and local officials is also being developed.

Official estimates put the Roosevelt elk population along the U.S. 101 corridor in Humboldt and Del Norte counties at 1,600 animals. Biologists, however, suspect those estimates to be low. In an attempt to reduce growing human-elk conflicts, CDFW issued 20 additional Roosevelt elk tags during the 2019 hunting season through its SHARE program, which provides public hunting opportunities on private land through cooperating landowners. CDFW is currently petitioning the California Fish and Game Commission to increase the allotment of Roosevelt elk tags available along the north coast in the 2020 fall hunting season.

Translocations, limited hunting, high calf survival, and conservation management have all helped boost Roosevelt elk populations from lows in the early 1900s to a robust statewide estimate today of 5,700 animals. Roosevelt elk also occupy parts of Mendocino, Trinity, Shasta, Tehama and Siskiyou counites.

The U.S. 101 corridor population in Humboldt and Del Norte counties has proved particularly adaptable – as comfortable roaming the beaches of state parks as they are grazing in open alfalfa fields or wandering underneath the forest canopy. That’s made them especially popular with tourists and some locals but not so much with farmers and ranchers suffering property damage and crop losses from the expanding herds.

David Wright uses a mirror to reflect light into dark rock crevices in search of pika sign such as scat or urine stains. CDFW image by Joseph Stewart.


Joseph Stewart hikes through one of the mountainous locations in the northern Sierra Nevada that researchers searched for habitat that appeared suitable for pikas. CDFW image by Johanne Boulat.

CDFW staff recently conducted a study to determine whether American pika in California are able to find sufficient refuge from elevated temperatures in their natural habitat. Previous CDFW collaborative research and related work has suggested that pikas in California and Nevada have been declining in warmer areas, but some scientists contend that underground temperature refuges will protect pikas from warming temperature trends.

“The question of whether pikas are protected or exposed to warming temperatures seemed key to us,” said David Wright, a retired CDFW senior environmental scientist who co-authored the research with Joseph Stewart, a former CDFW scientific aid and now a University of California, Davis post-doctoral researcher. “It is central to whether or not climate change is going to push pikas to higher, cooler elevations and significantly reduce and fragment their range, in our state, on our watch.”

Pikas are small herbivores related to rabbits that live in fields of broken rock (talus) in the mountains of western North America. Researchers examined 46 mountainous locations in the northern Sierra Nevada with habitat that appeared suitable for pikas.  

Pikas prefer talus with rocks eight inches to three feet in size, and larger or less isolated talus fields are generally more likely to support pikas.

“We did our research at elevations both within and below the expected elevation range of pikas,” Wright said. “Lower elevations on average have warmer temperatures, which pikas don't tolerate well, but it's been suggested that talus provides a refuge from warmer temperatures. We wanted to look at this hypothesis.”

Two species of pika occur in North America, with only the American pika found within the continental U.S. With their high metabolic rates and thick fur (including inside their ears and on the bottoms of their feet), American pikas are well adapted to cold temperatures at high elevations. They do not hibernate during the winter, and spend the summer gathering grasses and wildflowers to store in “haypiles” for subsistence during the winter. Hikers may know them from their distinctive alarm call, a high-pitched cross between a chirp and a bark.

In 2010 to 2013, using small, year-round temperature recorders lowered approximately 1.6 feet to 3.3 feet into talus, along with visual surveys for pikas or signs of pikas, Wright and Stewart found that temperatures below the talus surface were buffered from warm and cold extremes of ambient air temperature. This was consistent with previous findings.

However, pikas were not found wherever talus temperatures were suitable. Temperatures within talus were mostly suitable for pikas across all the study sites regardless of elevation, yet pikas were absent from many of the sites. Instead, summer air temperatures proved to be the best predictor of pika presence or absence. The warmest sites had no evidence of pikas, followed by warm sites that had only remnant fecal pellets (pika pellets can persist among the rocks for decades), then slightly cooler sites that supported pikas in some years but not in others, to the coolest sites which supported persistent populations of pikas throughout the study.

“It’s not enough to have suitable temperatures in their underground burrows,” said Stewart. “Pikas also need suitable temperatures above ground where they forage for food.”

The authors concluded, based on their own and other research, that daily warm air temperatures may inhibit pika foraging and survival because they cannot tolerate the heat, and juvenile survival and dispersal may be similarly impaired by elevated summer high temperatures. Talus provides a cool refuge for pikas up to a point, but beyond that point pikas still need to forage and complete the portions of their life cycle that occur aboveground. This balance point, from this research, appears to be near an average warm season (June to September) air temperature of 71 to 73 degrees.

Funding for this research and similar CDFW efforts in the Sierra Nevada are supported by State Wildlife Grants administered through the U.S. Fish and Wildlife Service.

The study, Within-talus temperatures are not limiting for pikas in the northern Sierra Nevada, California, USA, can be viewed here (PDF).

CDFW Photos. Top Photo: Pikas are small herbivores that live in fields of broken rock (talus) in the mountains of western North America. CDFW image by Jan Dawson.

Media Contact:
Kyle Orr, CDFW Communications, (916) 322-8958

A newly collected female wild white abalone releases eggs during the captive breeding program’s annual spawning event. This was the first new genetic input in the captive population for 14 years. Photo taken for CDFW by M. Ready

At nearly 130 feet underwater, CDFW abalone researcher Dr. Laura Rogers-Bennett didn’t have much time. Her dive computer told her it was time to ascend, which meant that she would have to stop searching for the endangered white abalone hiding in the waving fields of red and gold gorgonians.

Reluctantly, she watched the beautiful scene drop away below her as she kicked slowly upwards. She moved through the towering elk kelp towards her safety stop, a precious white abalone kept solidly in her grasp. On that trip, back in 2004, Rogers-Bennett and Ian Taniguchi, another CDFW abalone expert, and a team of other scientist divers collected 21 critically endangered white abalone off the deep reefs in the Channel Islands. This collection trip was conducted in an effort to save the species before they disappeared from the wild, and to create a captive breeding program that could bring this important and iconic species back from the brink of extinction.

Fourteen years later, the white abalone Captive Breeding Program is a thriving reality, thanks to the vision and hard work of a committed team of scientists from the White Abalone Consortium (WARC). Those 21 animals that Rogers-Bennett helped to collect in the Channel Islands have now produced thousands of descendants in captivity. The program is so successful, in fact, that it is now producing more animals than it has space to raise. Now, the next step is for WARC and CDFW scientists to perfect methods to release these captive bred animals back into the wild.

A huge challenge for CDFW and the WARC is to ensure that the captive-bred animals stand the best chance for survival in the wild – and one of the greatest obstacles could lie within the abalones’ own DNA. Because the entire captive-bred population stems from only 21 animals, the genetic diversity of the captive program is limited. One of the main factors that influence how a population of animals will react to stress is how genetically diverse the individuals are from one another. 

In the past, wild, healthy white abalone populations had large numbers of individuals to reproduce with. This created a vast number of family lineages and resulted in an expansive genetic pool. A population with diverse genetic parentage strengthens the overall population by ensuring that there will be a diversity of responses among the individuals. For example, some stresses, like disease or environmental change, may affect certain individuals while others maybe be more genetically suited to defend against those threats. If the population faces a major disease outbreak, some individuals will likely survive, enabling the populations to restore itself over time. But if a population lacks this genetic diversity due to limited parentage, the entire population could succumb to the disease.

The solution is to introduce new animals into the captive breeding population in order to diversify the gene pool and create animals vigorous enough to thrive in the wild. Yet that’s a trickier proposition than one might think, because of their endangered status. Even when evidence strongly suggests that there has been zero reproduction, researchers follow very strict guidelines so as not to disrupt potentially viable populations. For this reason, WARC and CDFW spent years monitoring reproduction of wild white abalone populations, until they were absolutely certain that the animals were not reproducing in the wild.

In 2017, the WARC was given a permit by NOAA to collect wild animals for the captive breeding program. The following May, when conditions were right, Rogers-Bennett and the WARC team of scientists returned to the Channel Islands on the first white abalone collecting trip in more than a decade. WARC divers gathered in the spring sun on the deck of the research vessel Garibaldi to discuss the day’s dives, which would be to nearly 120 feet. Everyone was focused, but a cautious optimism hung in the air. Encountering the incredibly rare white abalone was a long shot, but two individuals had been spotted in the area within the last year.

Alongside her team, Rogers-Bennett descended through the water column, watching as the ocean floor came into focus below her. As she got closer, she could just make out the familiar shape of an abalone. She assumed it was another, more common species of abalone, but as she got lower she recognized the unmistakable markings of a white abalone. She had landed directly on top of one!

Since the beginning of 2017, 10 animals have been collected by WARC scientists and transported to their facility in Bodega Bay. This is the first time in 14 years that scientists will be able to add new genetics to the captive breeding program. Dr. Kristin Aquilino, Director of the UC Davis Captive Breeding Program for the WARC, was able to include a newly collected female white abalone into the 2017 annual captive breeding spawn. It takes time before wild animals are able to integrate into the program, but researchers hope that the newly collected animals will participate in the next white abalone broodstock spawn.

With the new genetics from the wild abalone being introduced to the captive breeding program, and restorative stocking studies underway, the future for this species is looking brighter all the time. Through the dedication of a brilliant team of scientists, policymakers and an engaged public, the WARC is hopeful that one day the white abalone will resume its ecological role in the deep reef ecosystems of the beautiful Southern California kelp forests.

Please stay tuned for more updates about the white abalone and our other abalone restoration work in California!

CDFW Photos. Top Photo: CDFW diver Ian Tanigucci takes notes before collecting a wild white abalone (in the foreground) in 2017. This is one of 10 white abalone collected from the wild to be integrated into the captive breeding program at Bodega Marine Lab. These newly collected animals will provide a new and much needed source of genetics for the captive bred white abalone populations.