Science Spotlight

Mountain lion territory, San Diego County.


Justin Dellinger in the field, for the mountain lion study.


Mountain Lion after capture, before being released.

CDFW wildlife biologist Justin Dellinger has a most unusual job --  since 2015, he’s been capturing and collaring mountain lions in California’s back country. Justin aims to achieve something unique, which is the first-of-its-kind comprehensive population assessment of California’s mountain lions.

It’s a tough job that begins long before daybreak, in some of California’s roughest terrain. Justin works with a houndsman whose dogs track the lions by scent. When they pick up the trail, it’s Justin’s job to tranquilize the lion, take biological samples and fit it with a tracking collar before setting it free. But lions are elusive by nature, and there’s a lot of territory to cover. In between successful captures, Justin spend his time setting traps and cameras, fixing field equipment and hiking the state’s hills and mountains looking for tracks.

California’s mountain lion population is thought to be between 4,000 – 6,000.  Because lion habitat has been reduced by human encroachment in the most populous state in the nation, researchers like Justin are seeking any information they can to better understand where wildlife live, what they eat, how they deal with disease, and how they can thrive in the future.

To date, there’s just one corner of the state Justin hasn’t yet scoured as part of the project – the far northwest. That work is scheduled to start in November 2020, with the goal of incorporating the results of the study into the CDFW’s lion management plan by 2023.

Learn more about Justin’s work in the video below, and read about the early stages of the project in this July 2018 Science Spotlight about the state Mountain Lion Project.

CDFW Photos.

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Media Contact:
Tim Daly, CDFW Communications, (916) 201-2958

CDFW manages about 940,000 acres in over 200 properties statewide that are designated as wildlife areas or ecological reserves. Pictured is Elkhorn Slough Ecological Reserve in Monterey County.


Properties like the Carlsbad Highlands Ecological Reserve are acquired and managed to protect sensitive plant and wildlife species.

At the nearly 17,000-acre Yolo Bypass Wildlife Area near Davis, staff close off some areas to the public during certain times of year. The closed zones offer resident wildlife a reprieve from the many activities offered at the site such as hunting, wildlife viewing, and student education field trips.

CDFW working to improve negative effects of non-consumptive recreation on conservation

Editor’s Note: As we publish this article, California, the nation, and the whole world are gripped by the COVID-19 pandemic. To slow its spread and not overwhelm healthcare resources, distancing and stay-at-home orders have led to the delay of trout openers and other fishing events, and closure of parks, reserves and many other publicly accessible facilities. Stories are beginning to emerge of increased wildlife presence in park and reserve areas that are normally filled with people. We look forward to the end of the pandemic and its horrible devastation will be over very soon but we know it will be some time before we realize a return to “normal.” We hope to gain from this emergency more information on wildlife’s response to fewer visitors – data that may be able to help us improve our management of parks and reserves in a way that protects wildlife and their habitat while also providing reasonable recreation experiences. In the meantime, stay well, and stay home to save lives.

Do Not Feed Wildlife. Do Not Cut Switchbacks. Stay On Trail. 

If you’ve spent time in recreational areas, you’ve seen the signs. You’ve most likely complied with them. But you may not have a full understanding of why the rules are important.

A growing body of research is showing that non-consumptive recreation – i.e., activities like hiking, biking and bird watching, that don’t involve harvesting of resources – can have harmful effects on species, their habitat and efforts to protect them.

For example, one study showed that mule deer may experience increased predation risk when they shifted toward nocturnal activity in response to human recreation. Another study showed that human activity resulted in elk foraging less and showing increased signs of stress. Research has shown (PDF) that higher levels of human activity reduced habitat suitability for bobcats, gray fox, mule deer and raccoons. Human activity has also been linked to declines in reptile species.

Recreation has been cited as a factor in endangerment of plant and animal species on federal lands, and of all U.S. states, California has thegreatest number of listed species that are threatened by recreation. In a literature review led by Courtney Larson, a scientist for The Nature Conservancy, 93 percent of included articles found significant effects of recreation on wildlife.

“CDFW is tasked with managing the state’s diverse plant and wildlife species and the public’s use and enjoyment of them – so how do we also manage the effects of recreation? We have to bring environmental stewardship into the fold and find ways for recreation and conservation groups to work together,” said Ron Unger, a program manager in CDFW’s Habitat Conservation Planning Branch. “It’s important to set aside lands for both needs. Lands set aside for conserving declining and vulnerable species generally need to be restricted in terms of public access. Other, less sensitive sites need to be set aside so people can have a positive place to enjoy and appreciate nature and the outdoors.”

At the Carlsbad Highlands Ecological Reserve – a CDFW-owned reserve in San Diego County – land managers have had a tough time with mountain bikers and others building illegal trails. Over the past half-dozen years, bikers have illegally carved out about 17 miles of trails (the property has 2.1 miles of legal trails) and removed nearly 500 trail signs. CDFW had to step up enforcement to stop the illegal trail use.

“We don’t enjoy telling people they can’t ride here, but at the same time we have to make sure we don’t love these spaces to death – especially when the main reason the lands are acquired and set aside is to protect wildlife,” said CDFW Regional Manager Ed Pert.

At the nearly 17,000-acre Yolo Bypass Wildlife Area near Davis, staff close off some areas to the public during certain times of year. The closed zones offer resident wildlife a reprieve from human activity.

“It’s definitely a balance. We want the public to enjoy wildlife, but we also want to give wildlife a place to rest,” said Joe Hobbs, who manages the wildlife area.

CDFW Senior Environmental Scientist Shannon Lucas helps coordinate the department’s Natural Community Conservation Planning (NCCP) program, which issues regional permits that allow for development while ensuring habitat protection. She also oversaw grant funding for research on the effects of recreation on NCCP lands.

“These are areas that are intended to be preserved for their ecological value. We have a responsibility to analyze the effects of recreation on the species and habitats that contribute to conservation under an NCCP,” said Lucas.

CDFW is involved with research efforts aimed at gaining insight into how to best balance recreation with conservation. The department’s Human Dimensions of Wildlife Unit is currently researching the views of stakeholders, and future research will assess how to best communicate with stakeholders on the issue.

“We want to serve our constituents as well as manage the state’s natural resources for their ecological value. Once we understand how our stakeholders feel about the issue, we can communicate in a way that connects with their concerns,” said lead researcher Alex Heeren.

CDFW just released a special edition scientific journal featuring literature reviews and original research on the effects of non-consumptive recreation on wildlife. Ange Baker, editor-in-chief of California Fish and Wildlife Journal, chose the topic after soliciting ideas from CDFW employees.

“Research has shown that even mild recreation like hiking can have pretty significant impacts on some species. This is an especially important issue in California where CDFW manages about 940,000 acres of property designated as wildlife areas or ecological reserves. We decided to do a special edition to bring light to the issue,” said Baker.

Read the special edition journal (PDF).

CDFW Photo. Top Photo: Signage at Carlsbad Highlands Ecological Reserve in San Diego County is intended to help protect threatened and endangered plant and wildlife species by prohibiting incompatible recreation activities such as motorized vehicle, biking, and drones.

Media Contact:
Ken Paglia, CDFW Communications, (916) 322-8958

Upper Independence Creek provides vital spawning habitat for the Lahontan cutthroat trout in Independence Lake.


State and federal agencies, joined by conservation groups such as Trout Unlimited, have worked for decades to safeguard the wild Lahontan cutthroat trout population at Independence Lake, the only self-sustaining lake population of the native species left in California. Trout Unlimited’s Brandon Reeder shows off a hefty Lahontan cutthroat captured at a temporary weir to count spawning fish.


Lahontan cutthroat trout spawn in upper Independence Creek, where biologists have worked for years to remove non-native brook trout.


Each spring, biologists and volunteers set up a weir at upper Independence Creek to trap spawning Lahontan cutthroat trout and assess the population.

The news out of UC Davis last spring knocked California native fish biologists for a loop.

Genetic testing of native Lahontan cutthroat trout from Independence Lake in the Tahoe National Forest near Truckee found evidence of hybridization with non-native rainbow trout.

To understand the magnitude of that news you have to understand that Independence Lake is the only lake in California – and just one of two lakes in the world – to support a self-sustaining lake population of Lahontan cutthroat trout, a trout native to the eastern Sierra range and the Lahontan basin of Nevada.

And you have to understand that for decades, California Department of Fish and Wildlife (CDFW) biologists – joined by colleagues at the U.S. Geological Survey, U.S. Forest Service, the U.S. Fish and Wildlife Service and conservation groups including The Nature Conservancy and Trout Unlimited – have worked to safeguard these fish, enhance their habitat, and reduce competition from non-native brook trout, brown trout and Kokanee salmon introduced over the years into Independence Lake.

Lahontan cutthroat trout are listed as a threatened species under the federal Endangered Species Act. Their original listing in 1970 predates the modern act itself, which was passed in 1973.

Each fall, as part of species recovery efforts, biologists from CDFW and partner organizations electrofish upper Independence Creek, which feeds into Independence Lake, to remove brook trout from the creek that the Lahontan cutthroat trout depend on to spawn. Also in the fall, biologists set up a weir on the creek to block any of the lake’s resident brown and brook trout from moving up the creek to spawn. Non-native trout staging for a fall spawning run at the mouth of Independence Creek are stunned to the surface through electrofishing and removed from the lake.

“For the past 20 years at Independence Lake, we’ve been trying to give the cutthroat a helping hand by removing the non-native trout. It’s not a done deal but we’ve been pretty successful at reducing brown and brook trout down to very low numbers,” explained Dave Lentz, CDFW’s native trout conservation coordinator. “Lahontan cutthroat trout did not evolve with brook trout or brown trout on the landscape and they have been out-competed and displaced by these and other non-native species throughout much of the cutthroat’s historic range.”

Each spring, when the Lahontan cutthroat trout move up to spawn in upper Independence Creek, biologists and volunteers return with their weir to capture and count the numbers of spawning fish to assess population trends.

This spring, however, the spawning surveys will take on a new sense of urgency. After last year’s disheartening news from genetics experts, CDFW staff and partners captured some 170 Lahontan cutthroat trout from Independence Lake, took genetic samples and outfitted each trout with an identifying Passive Integrated Transponder (PIT) tag before releasing the fish back to the lake.

The tissue samples were sent to two labs for genetic testing. The results indicate that some 20 percent of the cutthroats captured and tagged last year show evidence of hybridization with rainbow trout. Biologists are now discussing plans and options for the spring spawn. Cutthroat trout returning to upper Independence Creek will be trapped and scanned with a PIT reader. Unmarked fish will be given a PIT tag, genetic samples will be taken for later testing, and the fish will be returned to the lake.

“We want to prevent further spawning by hybridized trout. We’re using some emerging science and the latest genetics information to manage this fishery,” said Lentz. “The situation is dire for Independence Lake cutthroat trout but we hope to improve their status by taking these measures.”

There are no known populations of rainbow trout within Independence Lake that could account for the hybridization but they are present in lower portions of Independence Creek below the lake. The outlet of the lake, however, is controlled by a dam that does not allow for fish passage into the lake. CDFW and partners will continue to investigate how rainbow trout gained access to the lake. It is thought that the rainbow invasion and hybridization are recent events, likely in the last 10 years.

The effort to remove hybridized cutthroat trout from Independence Lake takes place as state and federal officials in California, Nevada and Oregon step up collaborative efforts to increase Lahontan cutthroat trout awareness and recovery across their native range. Among those efforts:

• A genetic assessment of Lahontan cutthroat trout across their historic range has been underway for the past several years. That process resulted in the UC Davis findings of hybridization within the Independence Lake cutthroat population.
• In May 2019, the U.S. Fish and Wildlife Service released a document that updates recovery goals and objectives from its 1995 Lahontan cutthroat trout recovery plan using current science and a new conservation framework for species recovery.
• In October 2019, the U.S. Fish and Wildlife Service released 5,000 Pilot Peak strain Lahontan cutthroat trout back into Lake Tahoe, returning the native, fast-growing strain to Lake Tahoe for the first time in nearly 90 years.
• This coming May, state and federal fisheries biologists are scheduled to begin planning Lahontan cutthroat trout recovery and outreach efforts within the Carson River drainage.
• CDFW’s Hot Creek Trout Hatchery in the eastern Sierra is preparing facilities to establish a new rearing program for the Walker River strain of Lahontan cutthroat trout native to the Walker River drainage and Nevada’s Walker Lake.

CDFW Photo. Top Photo: A windy day at Independence Lake in the Tahoe National Forest.

Media Contact:
Peter Tira, CDFW Communications, (916) 215-3858
 

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