Science Spotlight

California Fish and Game, Volume 104, Issue 2, is now available online! California Fish and Game is CDFW's official, quarterly, scientific journal devoted to the conservation and understanding of the flora and fauna of California and surrounding areas, and the eastern Pacific Ocean.

A mallard in flight appears on the cover of the newest installment of the journal. With its iridescent green head and school bus yellow legs, the male mallard is one of the most recognizable species of duck in California. It is also the most abundant breeding species of waterfowl in the state. However, California’s mallard population estimates have generally declined since the mid-1990s. In California mallards: a review, Feldheim et. al synthesizes volumes of research in an effort to identify long-term research needs and monitoring activities to help improve management of this iconic species.

In another paper, entitled Abundance, habitat and occupancy of Roosevelt Elk in the Bald Hills of Redwood National Park, Tolliver and Weckerly seek to understand the relationship between a species’ occupancy-abundance rate and its habitat use. Using elk sign surveys (i.e, counting tracks and feces at standardized locations) researchers found that, as population density increases, Roosevelt elk will move into other (lower quality) habitats. This was true for two herds of vastly different sizes, although the occupancy rate remained comparable.

Finally, Hiney et. al looks at recruiting experienced anglers and using citizen science to help document and survey the native Coastal Rainbow Trout population of Grass Valley Creek Reservoir. The authors look at methods of overcoming the time and resource limitations of assessing wild trout populations.

Also included in this issue are reviews of two books that make meaningful contributions to the field of wildlife research.

As it has for the past 104 years, California Fish and Game continues to publish high-quality, peer-reviewed science that contributes to the understanding and conservation of California’s wildlife. We look forward to witnessing the contributions of the next installment.

The latest issue of the scientific journal California Fish and Game is now available online (for free!). Volume 104, Number 1 features a gorgeous photo of a black-tailed jackrabbit in sunlit profile taken by renowned photographer David Jesse McChesney. The back cover image, also by McChesney, features two cottontails at play. We are fortunate to be allowed the use of these amazing images to promote the content of the latest issue. Individual papers in this issue include:

• Reproductive aspects of Sphyraena ensis (Perciformes: Sphyraenidae) inhabiting the coast of San Blas Nayarit, southeast Gulf of California (PDF). The Mexican barracuda is the subject of a study that gathers baseline data for this important fishery resource. Although the species constitutes one of the main economic pursuits along the coast of Nayari, Mexico, little is known about its reproductive biology. A one-year study of specimens caught via commercial fishing revealed that females outnumber males (1:1.87 male:female). They also grow larger—a reproductive strategy that allows them to produce more eggs. By comparing the size of the liver and reproductive organs of the specimens, relative to their overall size, researchers were able to determine that both sexes are at their reproductive peak from April to June. The study results suggest that a fishery closure during this peak reproductive time can provide long-term population benefits for the species.
• Comparison of rabbit abundance survey techniques in arid habitats (PDF). An important component of any species management plan is population data, which is why it is important to know which survey methods are most effective and cost-efficient. Cypher et. al assesses four methods for counting rabbits and hares in arid climates: 1) visual encounter surveys (walking slowly and counting every animal observed); 2) spotlight surveys (driving slowly at night while shining spotlights out each side of the vehicle); 3) aerial surveys (using a low-flying helicopter to flush and count animals along transect routes); and 4) track stations (putting bait in clearings that have been raked smooth, then counting tracks). The results provide interesting observations to consider based upon the individual researcher’s budget, the habitat being studied, and staff time and availability.
• Field method for estimating the weight of tule elk from chest circumference (PDF). Studying larger animals provides an entirely different set of challenges. CDFW biologists frequently capture tule elk for the purpose of relocating them, gathering data and/or providing veterinary care. Administering a proper dose of sedatives and reversal agents is critical for the safety of the animal as well as its human handlers. Since the dosage is based upon weight, the challenge is figuring out how to accurately estimate the weight of an animal that is the size of a full-grown cow. Langner and Casady address this issue by determining a field method for estimating the weight of tule elk. The researchers captured and weighed more than 50 elk over a four-year period, measuring the chest circumference of each animal. The data were analyzed and resulted in a conversion chart that aids researchers in more accurately estimating weights of tule elk in the field.

The latest issue also contains a review of Butch Weckerly’s book, Population ecology of Roosevelt elk: conservation and management in Redwood National and State Parks and a reprint of a scientific paper originally published in 1947 entitled, “Ecology of a cottontail rabbit (Sylvilagus audubonii) population in Central California."

California Fish and Game is CDFW’s official scientific journal devoted to the conservation and understanding of the state’s plants and animals. This issue (either in hi-res or low-res) can be found in its entirety online.

CDFW Photos.

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
 

Camouflaged trap used to capture foxes for the study. CDFW photo by Jennifer Carlson.


Sierra Nevada red fox bounds back to its native habitat after capture and study. CDFW photo by Scientific Aide Corrie McFarland.

The Sierra Nevada red fox has been the subject of intensified study by CDFW over the past decade. As they are notoriously tough to track and even tougher to trap, there are many unanswered questions regarding this elusive animal.

In an effort to better understand this state-listed threatened species, an ongoing research project seeks to capture and affix GPS tracking collars to them. The data collected will help biologists better understand the size and characteristics of the fox’s home range, its denning and resting areas, and its foraging habits.

The species has been outfoxing researchers for some time -- to the point where in the 1980s, it was presumed to have vanished forever from its historically occupied habitat in the Cascade and Sierra Nevada ranges. In March 1993, thanks to the then-emerging technology of infrared trail cameras, US Forest Service employees detected a single red fox in the Lassen National Forest.

That discovery prompted a wider study of foxes and other meso-carnivores in and around Lassen Volcanic National Park. In the late 1990s and early 2000s, Dr. John Perrine of the University of California, Berkeley, captured five individuals, primarily in the park, and placed radio collars on them to study their home range (both summer and winter), food habits and resting sites. Unfortunately, two of the collared individuals died within a year and none of the females reproduced during the course of the study.

Years later, CDFW launched a new study to determine the foxes’ current distribution in northern California and to address potential impacts on the species from activities including recreation and timber harvest. Initial efforts in 2008 used scat-detector dogs to survey portions of Lassen Volcanic National Park and the adjacent Caribou Wilderness. Then, from 2009 to 2011, trail cameras and hair-snaring devices were employed to survey high-elevation habitats in the Cascade Range from Mount Shasta to Lassen Peak. Yet foxes were only detected in the Lassen Peak area.

CDFW biologists have continued to survey for foxes with trail cameras, hair-snaring devices and scat surveys. Scats and photos are often obtained along Lassen Volcanic National Park and Forest Service hiking trails, because, like many other animals, red foxes frequent trails as they move through their territories. Analysis of the DNA contained in the collected scats and hair identified 22 individuals from 2007-2016. Some of these foxes are long-lived – samples collected over time from the same individual indicate that five of those individuals lived at least five and a half years.

CDFW efforts to capture and collar Sierra Nevada red foxes since 2013 were unsuccessful – until early February 2018. The nearly two decade-long dry spell came to an end at last when CDFW captured a Sierra Nevada red fox, a male that weighed about 10 pounds. It was captured in a “log cabin” style trap on National Forest land just outside of Lassen Volcanic National Park, near the town of Mineral. The fox was collared and released at the capture location, and CDFW biologists have been impressed by the distances he has regularly been covering since (five to six miles per day) despite the rough terrain and high elevation.

“Persistence played a large role in our success, because there are many days when we do not have any fox detections,” said CDFW Wildlife Biologist Jennifer Carlson. “We also ramped up our efforts this year by hiring two scientific aids rather than just one, which allowed us to literally double our efforts by putting more traps out across the study area.”

CDFW hopes to capture as many as four more red foxes this year. Scientists are using box traps, cage traps and a “log cabin” style trap that researchers have used in other states to capture both red foxes and wolverines. Capturing foxes is not an easy task given the cold temperatures and snowstorms, but as the Lassen population may only consist of around 20 individuals, it is imperative for the department to learn as much as it can about this stealthy animal.

For more information, please visit the Sierra Nevada red fox page.

Top photo: Senior Environmental Scientist Pete Figura and Senior Wildlife Veterinarian Deana Clifford release a red fox study subject. CDFW photo by Corrie McFarland

It does not take a leap of faith to believe that CDFW scientists have gained the upper hand in bolstering the population of yellow-legged frogs in the High Sierra.

Over the past three decades, Sierra Nevada yellow-legged frogs have become imperiled in California due to the two-pronged impact of introduced (non-native) trout and chytridiomycosis, a disease that is affecting amphibians worldwide.

Past introduction of non-native fish, including rainbow trout and golden trout, to benefit sport fishing in the High Sierra took a heavy toll on the species. High-elevation lakes where these frogs once flourished were largely fishless until fish stocking came into vogue. As the years passed, scientists determined that these introduced fish were depopulating the frogs by competing for food sources (primarily insects) and by predation (trout ate both adult frogs and their tadpoles). Chytridiomycosis, which affects many frog species, also impaired the ability of the Sierra Nevada yellow-legged frog’s skin to exchange vital nutrients, which often leads to death.

As a result, Sierra Nevada yellow-legged frogs are believed to have vanished from approximately 92 percent of their historical habitat, and halting and reversing that decline has become an important goal of CDFW, as well as other state and federal entities.

“This is an animal that only lives in the Sierra Nevada,” said Sarah Mussulman, a CDFW senior environmental scientist. “It is one of our unique California species that lives in high-elevation areas, and as an amphibian it serves as an important link between the terrestrial and aquatic ecosystems. This link is especially critical in the low nutrient, granitic basins of the High Sierra, where frogs and tadpoles consume insects and algae and are themselves consumed by a variety of snakes, birds and mammals.”

CDFW recently completed two projects as part of its ongoing efforts to reverse the population decline of Sierra Nevada yellow-legged frogs.

The efforts took place at two sites: Highland Lake and Clyde Lake, located approximately seven miles apart on the Rubicon River in the Desolation Wilderness area of El Dorado County. The projects were completed with federal grant funds earmarked for the recovery of endangered and threatened species (the species is listed as threatened by the State of California and as endangered by the U.S. Fish and Wildlife Service).

Highland Lake, along with its outlet, an unnamed stream, and two small adjacent ponds, supported a small population of rainbow trout when the project began in 2012. Trout abundance had declined in the absence of stocking in recent years but sufficient natural reproduction occurred in the inlet to Highland Lake to sustain the population. CDFW began using gill nets to remove rainbow trout -- the descendants of fish planted in the lake by CDFW from 1935 to 2000 -- in 2012, in partnership with Eldorado National Forest personnel.

During a frog-monitoring survey at Highland Lake in 2016, approximately 800 adult frogs were observed, as compared to a 2003 survey in which only a few tadpoles were observed. Because the frogs have consistently survived in this area despite the presence of chytridiomycosis, scientists believe they have a good chance at persisting in the area for a long time.

“Highland really had a population explosion over the past five years and can be counted as one of the most successful projects of this type ever undertaken,” Mussulman said.

The project at Clyde Lake was smaller and had somewhat different factors.

Golden trout, which frequently have the same negative impacts on Sierra Nevada yellow-legged frogs as rainbow trout, including predation and competition for food sources, were planted by CDFW at Clyde Lake from 1932 through 2000.

Once stocking was halted, the golden trout proved less resilient then the rainbow trout at Highland Lake, due to habitat factors.

“Clyde Lake sits in a north-facing granite bowl bordered by 1,000-foot cliffs, and no flowing streams enter the lake,” explained Mussulman. “There was no spawning habitat, which is likely why golden trout did not persist there after stocking was halted.”

The stream flowing out of Clyde Lake and four nearby ponds did support a small population of golden trout after plants were halted. The fish in the stream and ponds, which are self-sustaining populations, are precluded from moving from the stream into Clyde Lake by a fabricated dam. In 2013, frogs and a few tadpoles were observed in the stream alongside fish, and CDFW began removing the fish from the stream with gill nets to provide additional habitat for the frogs.

Nine years of monitoring data collected by CDFW scientists indicate that the area’s Sierra Nevada yellow-legged frog population, while small, is slowly increasing. Surveyors observed more than 120 frogs in 2016, compared to a low of six observed in 2005. Moreover, in 2016, for the first time, dozens of tadpoles were observed in the newly fish-free lower reaches of the stream.

“It is great to see these populations recovering,” Mussulman said. “It is a great privilege doing this work that helps keep these frogs on the landscape.”

CDFW photos: Highland Lake in the Desolation Wilderness, and a Sierra Nevada yellow-legged frog