Science Spotlight

rss
  • July 31, 2018

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:

  • link opens in new windowReproductive 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.
  • link opens in new windowComparison 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.
  • link opens in new windowField 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.

Categories: California Fish and Game Journal
  • July 24, 2018

Frog resting on rock
Yellow-Legged Frog

Small river pool of water featuring a small waterfall trees, rocks and steep, rocky terrain
Mountain Yellow-Legged Frog habitat

Many years of painstaking monitoring and assessment efforts undertaken by CDFW have helped guide an ongoing effort to bolster the dwindling populations of mountain yellow-legged frogs in Southern California.

Tim Hovey, a senior environmental scientist in CDFW’s South Coast Region, has been hiking through the forest to monitor and evaluate yellow-legged frogs in Little Rock Creek and Big Rock Creek in the Angeles National Forest since 2002, when they were listed under the Endangered Species Act (they were listed as state endangered in 2013). At that time, it was estimated that fewer than 100 adult frogs remained in the wild. 

The drastic decline of this population over the last 50 years has been a cause for concern to biologists. “The mountain yellow-legged frog is a critical part of the fragile stream ecosystem here in Southern California,” Hovey explains. “We hope that our efforts to increase the wild population through captive tadpole release will eventually lead to self-sustaining populations that will no longer require captive care to recover.”  

Hovey estimates that fewer than 400 adult mountain yellow-legged frogs currently exist in the wild in small populations throughout its range in Southern California. Threats to the species include habitat loss, pollution, non-native predators and the deadly amphibian disease chytridiomycosis, which is caused by the chytrid fungus. Some measures have already been taken to help the species. From 2002 to 2012, for example, CDFW was the lead agency involved in removing non-native predatory fish in a section of Little Rock Creek, located below the current mountain yellow-legged frog population, which essentially doubled the amount of high-quality habitat available for frogs in the stream.

But more human intervention is necessary, in the form of captive rearing. The multi-pronged effort to bolster mountain yellow-legged frogs includes contributions from the U.S. Fish and Wildlife Service, the Los Angeles Zoo, San Diego Zoo Global, the U.S. Forest Service, the U.S. Geological Survey (USGS), and others.

According to Hovey, the captive rearing project began in 2014, when wild-caught tadpoles were removed from Little Rock Creek and Big Rock Creek by USGS staff during a breeding cycle. The tadpoles were raised to adulthood in captivity at the Los Angeles Zoo in temperature-controlled aquaria in a quiet frog-rearing room, carefully equipped to mimic the frogs’ natural life cycle conditions.

While the tadpoles were growing, CDFW staff conducted field surveys to evaluate suitable habitat, using the data to identify specific streams where mountain yellow-legged frogs could potentially be released. The criteria for evaluation considered current recreational uses, access for monitoring, safety and property ownership. The resulting list of approved locations was reviewed by the other agencies and is being used to guide the releases.

On June 26, 500 tadpoles, descendants of the captive Big Rock Creek frogs, were released back into their historic range in the lower section of Big Rock Creek in the Angeles National Forest. Another 500 tadpoles, offspring of the Little Rock Creek captive group, were released on June 27 into Devils Canyon Creek in the Angeles National Forest. The offspring of the captive frogs, which were bred and kept separate, were released into their creeks of origin.  

“These releases represent a promising first step in the recovery of mountain yellow-legged frogs, as well as hopefully establishing new populations in areas where the frog has been absent for over fifty years,” Hovey said.  “We hope that with continued agency coordination and continued tadpole releases, the dwindling numbers of these endangered frogs will slowly begin to rebound and recover.”

This was the first release of tadpoles into Angeles National Forest with several more scheduled this summer throughout portions of the species’ range. 

###

CDFW Photos courtesy of Tim Hovey. Top Photo: Mountain Yellow-Legged Frog.

For more information:

US Fish and Wildlife Service, “Trailblazing Tadpoles
US Fish and Wildlife Service, Draft Recovery Plan for the Mountain Yellow-Legged Frog
CDFW, Mountain Yellow-Legged Frog, description and taxonomy
 

Categories: General
  • July 13, 2018

A man on a horse with a mule in tow, climbing rugged, mountainous, dry scrub-covered terrain
a man's hand laid flaat on sandy soil, next to a mountain lion track
A golden-coated mountain lion sits high on a large limb of an oak tree
Man wearing a hard hat and climbing gear, working his way up a tall pine tree, under a royal blue sky
A mountain lion crouches, well camouflaged by boulders and sandy soil under dead branches

It’s just before dawn in the eastern Sierra Nevada Mountains in Mono County. It’s a cold clear morning, a good day to be out experiencing a still very much wild area of California. California Department of Fish and Wildlife (CDFW) biologist Justin Dellinger and a Wildlife Services houndsman are preparing gear to go out looking for fresh mountain lion tracks in this vast landscape. With the help of a team of highly trained dogs, Dellinger and the tracker are focused on the ultimate goal: Capturing a mountain lion and outfitting it with a GPS collar for research purposes.

This tracking effort in Mono County is part of a larger project to estimate mountain lion population size statewide. It began in the southern Cascades and northern Sierra-Nevada Mountains in 2015, and since then CDFW has solely undertaken or collaborated on similar efforts in the north coast, Modoc plateau and here in the eastern Sierra Nevada Mountains. It’s tough work with long hours; trackers can spend days or even weeks in pursuit of lions. Yet tracking remains the gold standard method of gathering data in the mountain lion research world.

Notably, it takes both biologist and houndsman, each with a unique skill set, to make this team effort work. On this particular day, for example, Dellinger starts the ball rolling when he spots a fresh set of mountain lion tracks made the night before. The mark of the hind heelpad, measuring 52mm across, indicates that it’s a tom (male cat) heading southwest. The long stride suggests he’s traveling in a focused and determined manner – perhaps to secure a meal, locate a mate or confront another male trying to move in on his turf.

Dellinger radios the houndsman, who is astride a mule. The houndsman makes his way to the tracks with dogs in tow, where he assesses a wide variety of information – the time of day, wind speed and direction, topography, etc.

“The mental calculations (of the tracker) are rooted in decades of experience and know-how, but they’re still somewhat of an enigma to me,” Dellinger says. “But then again, houndsman feel likewise about the statistical calculations employed by biologists. It takes both of us, working together, to compile all the information and derive a solid population estimate.”

Over the next several days, the houndsman and the biologist follow the tom over miles of country, with the cat none the wiser about his pursuers. The team eventually catches up to the tom. The dogs masterfully trail him over boulders and around escarpments and tree him in a pinyon pine. The houndsman signals to Dellinger that the tom is treed. Dellinger then works his way into position to dart the animal. Success! Within an hour, the cat is asleep and Dellinger is able to affix a collar.

Yet despite the enormity of the overall effort, the day’s accomplishment is only one small step in the overall plan. Simply put, they’ll get a little rest and then wake up and try to do it all over again tomorrow.

As CDFW’s lead mountain lion biologist, Dellinger understands the need to study and understand Puma concolor only too well. “Lions are the apex predators across much of California, and apex predators can tell scientists a lot about the ecological wellbeing of a given landscape or ecosystem,” he explains. “If mountain lions are decreasing in an area, it’s likely that prey species are decreasing too. If mountain lions are exhibiting health issues, it’s likely that other animals in the ecosystem are experiencing similar issues.”

Because of those grants, this first comprehensive effort to collar lions around the state is now underway. It’s a huge and somewhat daunting task. California’s size and ecological diversity requires a divide-and-conquer approach, meaning that studies can only be conducted in one area at a time. Together, those “slices” of data will add up to a statewide picture. 

Getting the collar on the cat might be the most important part, but all of the data Dellinger collects on this trip will be useful. He’ll be able to compare tracks and remote game camera photos with GPS collar data to derive a minimum count of mountain lions in the area. For now, this is the best way of counting mountain lions in the western United States. In the future, CDFW may grow to rely on data gathering techniques that are more cost- and time-effective than tracking, and use more common skill sets. One possible alternative is developing thanks to the rapid advance of using genetics to monitor wildlife species without having to handle the animals. Scat samples can be collected and analyzed to provide a genetic fingerprint of the animal that deposited them. In theory, if enough lion scat is collected over a large enough area, CDFW can estimate the number of lions in the area.

But scat analysis is still a fairly new way of doing things, and until techniques can be tested, compared and perfected, CDFW will continue to employ the tracking “gold-standard.” The newer methods can be compared to the old, and it’s possible that the newer methods will outperform (i.e., be cheaper and just as reliable) the older methods in some areas but not other areas.

CDFW sees this statewide effort as a first step in monitoring and conserving the elusive, ecologically important mountain lion long-term in California. The project is still in its early stages and will likely continue for another six years or so. Dellinger is enthusiastically looking forward to the work. “It’s really cool because no other state has attempted such a comprehensive population assessment of lions … and  no other western state is as ecologically diverse as California,” he says. “Doing something this comprehensive requires working in a lot of very unique areas. It’s never going to be boring.”

Photos courtesy of Justin Dellinger

Categories: General
  • July 5, 2018

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

###

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

Categories: Wildlife Research
  • July 3, 2018

Woman holding dead nutria
CDFW dog trainer Lynette Shimek uses a dead nutria (caught in the Central Valley) to train Star and Trigger to search and locate the body as well as residual odor from the carcass

Woman in waders and orange shirt stands in water with dog
Successful nutria detection dogs have to spend a lot of time in the water searching for nutria scent and scat. One of the unknowns when dog training began in May was whether Trigger, a German shepherd, would take to water work. He quickly allayed any concerns.

Black dog with red collar sitting with person standing behind holding leash
K9 Star

German Shepherd dog sitting with tongue out wearing orange collar
K9 Trigger

Meet the newest members of CDFW’s “Team Nutria;” a 1-year-old female black Labrador retriever named Star and a 2-year-old male German shepherd named Trigger.

The two scent-detection dogs, their handlers and CDFW’s top canine trainer officially joined CDFW’s nutria eradication effort in late May. The two dogs have been undergoing training to detect nutria scent, scat and residual odor. Recently certified as being proficient at their work, the dogs will soon be deployed to the marshes, wetlands and riparian habit in California’s Central Valley where CDFW teams already have captured some 200 invasive nutria since eradication efforts began this spring.

Star and Trigger are learning quickly and drawing praise.

“Both of these dogs are exceptional to begin with and they are exceeding expectations with how quickly they are adapting to the environment they will be working in,” said Lynette Shimek, CDFW’s canine trainer.

Nutria are semi-aquatic rodents native to South America that have turned up in the Central Valley’s marshes and wetlands and on the edge of the Sacramento-San Joaquin Delta. Their destructive feeding and burrowing threaten the critical wetland habitat needed by native species and jeopardizes the state’s water infrastructure. A top-rated agricultural pest, nutria also pose a serious risk to the state’s multi-billion dollar agricultural economy. CDFW is leading the state’s effort to eliminate nutria from the California landscape.

Nutria, furtive and primarily nocturnal, can be difficult to detect in the heavily vegetative wetland environments they prefer, particularly as trapping knocks down their numbers. Dogs can move more quickly through the wetland habitat and cover more territory than their human partners. The dogs’ responses to nutria scent – sometimes sitting, other times lying down or standing still – can alert CDFW biologists to nutria presence or let them know they need to look elsewhere.

It’s a page right out of the playbook of the federal government’s Chesapeake Bay Nutria Eradication Project, the only successful nutria eradication effort in the United States and a model and source of inspiration for California wildlife officials. That effort removed some 14,000 nutria from more than a quarter-million acres of the Delmarva Peninsula from 2002 to 2015. Nutria detection dogs joined the campaign in 2014 and proved invaluable in finding the last remaining animals. Three years after the last nutria was removed, the project still maintains a team of six nutria detection dogs and their handlers. Their primary role now is not to find nutria necessarily – but rather give biologists confidence that nutria are no longer present.

Many of the Chesapeake Bay nutria detection dogs have been Labrador mixes adopted out of animal shelters. The Labrador blood helps with the water work. The dogs’ high energy and prey drive that made them difficult household pets and forced their owners to surrender them made them ideal working dogs when given a job to do and a focus for their energy.

Star and Trigger, by contrast, have pedigreed bloodlines from proven scent-detection lineage. Still, questions surfaced at the outset of training whether the dogs would take to nutria detection work. Would Trigger, a heavy coated German shepherd, take to water work? Would Star, a bundle of Labrador puppy enthusiasm, have the attention span to stay focused on the job? Their training not only involves accurately identifying nutria scent, but also distinguishing it from that of beaver, muskrat, mink, raccoon and other birds and animals that inhabit the same wetland habitat.

It’s all positive reinforcement. Successful detection is rewarded with praise, affection and play. Star gets to make a few water retrieves of a favorite rubber ball toy. Trigger gets some toy time and a quick game of tug of war.

“They’re both doing extremely well,” said Shimek during a training break recently at the Upper Butte Basin Wildlife Area in Northern California. ”I am extremely confident these two dogs will be a big help in our eradication efforts.”

Star and Trigger are pioneers of sorts as biological detection canines. While CDFW has used canines in law enforcement work since 1989, Star and Trigger are part of two separate pilot programs to determine whether biological detection canines can support CDFW’s scientific work.

Star and Trigger’s handlers are not wildlife officers, but rather environmental scientists Harvest Vieira and Helayna Pera, respectively. Before their nutria assignment, Star was being trained to detect the nests of Western pond turtles, a Species of Special Concern in California due to declining populations. Trigger is trained to find downed deer that have been darted with tranquilizers. He can even locate errant darts from missed shots.

Both Vieira, based in Redding, and Pera, based in Sacramento, believe the nutria eradication effort is exactly the kind of high-profile project where their scent-detection dogs can shine, perhaps leading to a formalized program and additional biological detection dogs that can support CDFW’s various conservation and scientific efforts across the state.

 

 

 

 

CDFW Photos by Peter Tira. CDFW Video Courtesy of Sandra Jacks. Top Photo: From left to right: Trigger, his handler Helayna Pera, CDFW dog trainer Lynette Shimek, Star’s handler Harvest Vieira, and Star pause for a photo during a training break at the Upper Butte Basin Wildlife Area.

Categories: General