Science Spotlight

Researchers built 90 hair-snare stations designed to pull a small hair sample from black bears that cross the snares.


The Warner Mountains Black Bear Project study area (blue boundary) and layout of hair-snare grids (yellow squares) in northeastern California. The upper-left inset shows the southernmost hair snare grid and layout of hair-snare locations (red circles). Density estimates and information on habitat from within the 10 grids will help researchers estimate overall black bear abundance across the entire study area.

California’s black bear population is healthy and growing, with an estimated 35,000 animals, up from an estimated 10,000 to 15,000 in 1982. But how do wildlife biologists determine these figures – and why are they important?

Deep in the Warner Mountains in Lassen and Modoc counties CDFW is just completing the first year of a study of black bears. The lead scientist, Steffen Peterson, explained that anecdotal evidence in recent years – including increased bear sightings by both field scientists and everyday citizens, as well as an increased number of requests for depredation permits due to bear-human conflicts – seemed to indicate that the population of black bears in the Warner Mountains was booming and this area would be ideal for scientific research.

According to Peterson, the two primary objectives of the Warner Mountains Black Bear Project are to estimate black bear abundance in the study area and to determine how black bears use the landscape. This kind of information on black bear demography and space use is essential for wildlife managers to make scientifically sound bear management decisions for this region of California.

CDFW is using a genetic capture-recapture method to estimate the population size. Usually, this involves physically capturing an animal, marking it in some way and releasing it. But this particular study achieves the same goal with non-invasive techniques – specifically by using hair snares, which cause relatively little stress or harm to the animals. Hair snares have been used on many furbearing species to determine presence, to calculate a minimum absolute count of individuals present, or to estimate total population size by collecting a DNA sample from individuals without physically capturing the animal. Unique repetitive sequences, known as microsatellites, within the DNA sample serve as individual identifiers, making it possible to know when and where each unique animal was present.

In addition, because the DNA located within roots of mammalian hair can identify species, sex, and individuality, this genetic technique is ideal for researchers to estimate abundance as well as obtain information on demographics and genetic diversity.

Peterson, a CDFW scientific aid and a Humboldt State University graduate student, and other researchers built 90 hair-snare stations distributed across 10 sampling grids that that are designed to pull a small hair sample from bears that cross the snares.

The contraption consists of two parallel strands of barbed wire stretched around a cluster of three or more trees, one about eight inches off the ground and the other about 20 inches off the ground. This forms a barbed-wire “corral” in which researchers place a pile of logs drizzled with fish oil. The oil acts as an attractant to black bears, who have both a finely attuned sense of smell and a profound love of fish. At two thirds of the hair-snare stations, researchers placed a trail-camera to help verify the effectiveness of the snares at capturing hair samples when a bear is present. The trail photos also provide demographic (cub-adult ratio) information on bears within the study area.

“The use of hair-snares to collect genetic data for abundance and density estimates has become the gold standard for American black bear,” said Peterson. “The hope is for the bear to cross between the two strands of barbed wire, although some of our video footage from the trail cameras shows bears crossing – even jumping, in some cases –  over the wire. Because bears are big, robust animals, for the most part they pay little mind to the barbs and typically cross them, leaving us a nice big clump of hair. Bears are the ideal critter for hair-snares in this way.”

Although Peterson stressed that it is much too soon in the study process to draw conclusions about the number of black bears living on the grid, initial results indicate that, at a bare minimum, black bears are certainly roaming throughout the study area.

During a 50-day hair collection period that took place this summer, black bears were detected in all of the grids created in the study area that encompasses roughly 600 square miles of high desert terrain; researchers collected 469 samples of hair in all at 57 of the 90 hair-snare locations.

“Long story short, we are pleased by the amount of detections observed during our data collection,” Peterson said. “Good detections will strengthen our ability to estimate density within each grid which will allow us to more reliably estimate abundance off the grid – i.e., the Warner Mountain study area as a whole.”

Peterson is now set to begin the DNA analysis phase on the samples collected. This will allow him to determine precisely how many individual bears left hair behind (bears often leave more than one sample at a snare location and some individuals are repeat visitors), as well as information on gender and habitat use, including the movement of bears across the study area.

Next summer, project staff will capture and collar 12 adult black bear with research collars, which will record hourly GPS locations of the bears as they move across the landscape, providing information on how they use the landscape, including seasonal habitat preferences and, during the winter hibernation period, where bears den.

“This information will greatly improve our knowledge of how bears use these high desert ecosystems, characteristic of the Great Basin, and guide future land management in this region,” Peterson said.

The project is expected to continue for another two to three years. ###

CDFW Photos. Top Photo: Emily Monfort, a CDFW scientific aid, carefully removes black bear hair from barbed wire at a hair-snare location. The DNA from this clump of hair will be examined in the laboratory to determine the sex and genetic identity of the black bear that crossed this wire.  Photo credit Korrina Domingo (CDFW).

Panorama of Summer Lake


USGS employee holding goose


Summer Lake


Summer Lake


Melanie in the water retrieving geese


Melanie in sideview mirror


Fitting the collar


A finger nibble

Every September, California Department of Fish and Wildlife waterfowl biologist Melanie Weaver sets off on an unusual business trip. She packs up a trailer with huge nets, wire, rockets, crates and a number of VHF collars. She makes the seven-hour drive to Summer Lake, in southern Oregon’s high desert country, and settles in for a waterfowl capture project of indeterminate length. Her quarry is Anser alibifrons elgasi — the Tule white-fronted goose. Her goal is to capture, collar and release these huge, cackling birds until she runs out of collars.

Tule geese are one of two sub-species of white-fronted goose — also known colloquially as specklebelly geese, or “specs,” by hunters. The other sub-species of white-fronted goose, Pacific white-fronted, are plentiful, numbering about 700,000 in the Pacific flyway. But the Tule goose is far less common. Weaver estimates there are only 15,000 to 16,000 Tules.

Monitoring goose populations — particularly Tules — is a high priority for CDFW, as regulations are tied to the less numerous species. Currently, California regulations dictate that the hunting season for white-fronts on the west side of the Sacramento Valley closes on Dec. 21. This is to minimize harvest on Tule geese.

“They are right in the middle of a popular hunting area for Pacifics, so we have to be proactive,” Weaver explained. “If we saw the population decline significantly, we’d have to consider closing the season for all white-fronted geese. We want to avoid that.”

But why would the California Department of Fish and Wildlife be trapping geese north of the state line? One reason is logistics —Tule geese begin their southward trek from Alaska in mid-August or thereabouts. They’re heading for the Sacramento Valley, and Summer Lake Wildlife Area is a major stop over along the migration route. As they move further south into California, Tule geese mix with their more common cousins, the Pacifics. “We’ve tried to capture them in and around the Sacramento National Wildlife Refuge Complex before, and we end up expending a lot of effort just for a handful of Tules caught,” Weaver explained. “So the Oregon Department of Fish and Wildlife suggested moving our capture effort to the Summer Lake Wildlife Area. It’s largely only Tule geese coming through this time of year.”

And that’s the other reason — this partnership between the waterfowl programs from neighboring states illustrates the importance and strength of the Pacific Flyway. Alaska, Canada, Washington, Oregon and California all have a stake in ensuring the conservation of the species that traverse their lands and use their waters. ODFW doesn’t just offer up their land as a banding site. They also provide lodging for Weaver, typically split the cost of the radio collars, and supply labor for the duration of the project, no matter how long it takes.

Weaver’s ODFW counterpart, waterfowl biologist Brandon Reishus, was in it for the long haul right alongside Weaver. On a chilly Monday morning in mid-September, only just a week after they laid out the nets, they hit the jackpot. On that particular day, Reishus was crouched in the blind, using a scope to scan for incoming flocks, while Weaver sat nearby in a pickup truck. They waited and watched for a few hours, keeping in touch by radio, before Reishus spotted his opportunity. After a quick heads up to his Californian counterpart, the Oregon biologist pressed the detonation button, launching the pre-set rockets a quarter mile away. In the blink of an eye, the 60-foot-long net sailed over the unsuspecting birds as they blissfully churned up grit from the water. Both biologists then jumped into the truck and raced to the site, where they untangled the geese and put them into crates for transport to the Summer Lake Wildlife Area shop. The final count on this particular morning was 14 birds; a small number was all that was needed to complete the marking effort for this year as an earlier capture resulted in 44 birds.

The geese were given a little time to settle down before the processing began. Each bird was sexed and the bills measured. Although Weaver and Reishus can typically identify their catch just by the size and color (Tules are larger and darker than Pacifics), scientific measurements are essential for definitive identification.

The birds were also weighed before they were banded and collared. The collars will enable the biologists to obtain a population estimate on the wintering grounds, using a mark resight method. This and other data obtained from the bands will be used to make future management recommendations.

In the early afternoon, Weaver and Reishus drove back to the exact spot where the net was deployed just hours earlier. On the count of three, all the crates were opened at the same time, and the geese noisily rushed out, spreading their wings and re-forming their flock as they raced away.

As Weaver and Reishus affixed the last of the VHF collars on this particular Monday, they marveled at the unusually early conclusion of this years’ trapping effort. Sometimes it takes a full two weeks to use up their supply of collars. Once again, the team effort paid off. And even as they packed up their equipment from the Summer Lake Wildlife Area and prepared to head their separate ways, they were making plans to meet up again in a week, for a Pacific Flyway Study Committee meeting in Arizona.

“It’s such a valuable partnership,” Weaver said. “We look at the big picture, and we all work on solutions together.”
 
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CDFW Photos. Top Photo: weighing a goose.

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.

Marten resting atop a broken tree truck covered in moss and lichens. © Photo by Marx Marquez of Green Diamond, all rights reserved.


Marten in tree viewed through spotting scope. © Photo by Marx Marquez of Green Diamond, all rights reserved.


Marten climbing down tree trunk with rodent in mouth. © Photo courtesy of Green Diamond, all rights reserved.

A small population of a rare member of the weasel family has an improved chance at expanding its range, thanks to a joint effort between a forest products company and a state agency.

Green Diamond Resource Company recently signed a safe harbor agreement with the California Department of Fish and Wildlife (CDFW) to help assist in the recovery of the Humboldt marten. The agreement includes commitments by the company to create a 2,100 acre no-harvest reserve area for the marten, a 127,000 acre special management area for marten dispersal and monitoring, and dedicated funding and in-kind resources to support a possible assisted dispersal program and studies of how the martens use managed forests and adjacent public lands.

“We are looking forward to partnering with Green Diamond and exercising this relatively new safe harbor tool to facilitate and fund research and monitoring – and perhaps even help martens reconnect between the Six Rivers National Forest and the Redwood National and State parks,” explained CDFW Senior Environmental Scientist Jon Hendrix, who oversees the Timberland Conservation Program in CDFW’s northern coastal region.

Humboldt martens have been detected in the agreement’s no-harvest reserve area located on Green Diamond property and on the periphery of the company’s other lands covered by the agreement. The purpose of the agreement is to look ahead and voluntarily, proactively manage the land, in the hopes of increasing the presence of (and use by) a species that is protected by the California Endangered Species Act.

Humboldt martens were thought to be extinct in California until a small population was rediscovered in 1996 in portions of their historic range. Today, their known distribution in California is limited to areas of Humboldt, Del Norte and Siskiyou counties. In addition to the small population on Green Diamond property, Humboldt martens have also been detected on National Forest lands near tributaries of the Middle Fork of the Smith River.

In February 2016, the California Fish and Game Commission accepted a petition requesting the Humboldt marten be added to the list of threatened or endangered species under the California Endangered Species Act (CESA). CDFW has initiated a status review of the Humboldt marten which is nearing completion and presentation to the California Fish and Game Commission. During the candidacy review period, the Humboldt marten has been afforded all the legal protections provided under CESA.

In early 2016, Green Diamond applied for a California State Safe Harbor Agreement (California Fish and Game Code, sections 2089.2 – 2089.26) for Humboldt marten. The application included approximately 364,000 acres of Green Diamond’s timberlands, of which, approximately 137,000 acres fall within nine miles of the currently known Humboldt marten populations.

“Green Diamond has consistently applied a proactive view of forest stewardship and a science-based approach to managing its forests to the benefit of special status species such as northern spotted owls, salmon, steelhead and now, the Humboldt marten,” said Keith Hamm, Manager of Conservation Planning for the Green Diamond California Timberlands. “We embrace the opportunity to expand the marten population under this agreement and learn more about how marten use the company’s managed forests.” 

Although incidental take of Humboldt marten is authorized in the agreement, the goal is to conserve, protect, restore and enhance the martens’ habitat. Also included are specific measures to increase Humboldt marten populations and create new habitats.

The Safe Harbor Agreement itself is good for 40 years. It is structured to provide the opportunity for neighboring landowners to enroll their lands in the agreement and contribute to efforts to recover marten populations.

To learn more, please visit CDFW’s Timberland Conservation Program webpage, www.wildlife.ca.gov/Conservation/Timber.

More information about CDFW’s Safe Harbor Agreement Program Act can be found at, www.wildlife.ca.gov/Conservation/CESA/Safe-Harbor-Agreements.

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Top Photo: Collared marten in tree courtesy of Matt Delheimer. All other photos copyright of Green Diamond.  

The California Department of Fish and Wildlife (CDFW) has completed its 2018 waterfowl breeding population survey -- and it’s good news for hunters and birdwatchers alike, as the total waterfowl population in the state now tops out at over a half million, for the first time in six years.

Melanie Weaver, who oversees CDFW’s Waterfowl Program, said that duck populations responded positively to the wet winter conditions of 2017. “Given the good upland and wetland habitat conditions last year from excessive precipitation, we anticipated good production,” she said. “We are pleased to see that higher recruitment reflected in this year’s breeding population survey.”

The full Breeding Population Survey Report, which can be found on the CDFW website, indicates the 2018 breeding population of mallards increased from 198,392 in 2017 to 272,859 (an increase of 38 percent). Mallards are the most abundant waterfowl species in the state, followed by gadwall (102,637) and cinnamon teal (78,498).

Other ducks that increased in number include northern shovelers, wood ducks, redhead and canvasback. Overall, the total number of ducks increased from 396,529 to 549,180 (an increase of 39 percent).

A few duck species did decline, including American wigeon, northern pintail, lesser scaup, ring-necked duck, ruddy duck and common merganser. But Weaver gave two possible explanations for these dips. First, none of these species are considered “strong nesters” in California. They migrate through the state, but don’t breed here in high numbers. And second, the survey is designed for dabbling ducks, meaning that diving ducks (such as mergansers) are harder for biologists to detect.

The survey also included Canada geese, which dropped slightly in number, from 55,224 in 2017 to 54,851 this year. (Canada geese are detected and recorded throughout the survey; however, the number reported refers to the traditional nesting population in northeastern California.)

CDFW biologists and warden pilots have conducted this survey annually using fixed-wing aircraft since 1948. The population estimates are for those areas where the vast majority of waterfowl nesting occurs in California, including wetland and agricultural areas in northeastern California, throughout the Central Valley, the Suisun Marsh and some coastal valleys.

In 2018, the survey was flown April 24-28 in the Central Valley and May 9-10 in northeastern California. A few planned survey segments were cancelled due to weather conditions (fog in the Napa-Santa Rosa area, and high winds in a few planned transects in the northeastern part of the state). However, the crew was able to cover 97 percent of the planned survey transects.

The majority of California’s wintering duck population originates from breeding areas surveyed by the U.S. Fish and Wildlife Service (USFWS) in Alaska and Canada. Those survey results should be available in early August. CDFW survey information, along with similar data from other Pacific Flyway states, is used by the USFWS and the Pacific Flyway Council when setting hunting regulations for the Pacific Flyway states, including California.

CDFW Photo

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Media Contacts:
Melanie Weaver, CDFW Wildlife Branch, (916) 445-3717
Kirsten Macintyre, CDFW Communications, (916) 322-8988