Science Spotlight

The latest issue of California Fish and Game, CDFW’s scientific journal, is now available online. This century-old quarterly journal contains peer-reviewed scientific literature that explores and advances the conservation and understanding of California’s flora and fauna.

A photo of the world’s first radio tagged tricolored blackbird (Agelaius tricolor) graces the cover of this issue of California Fish and Game. The bird was tagged as part of a study, the results of which are published as “Breeding chronology, movements, and life history observations of tricolored blackbirds in the California Central Coast” by Wilson et al. The tricolored blackbird is currently under review for listing under both the California and Federal endangered species acts.

Also in this issue, Overton et al. offers a fascinating observation of predation by Peregrine falcons on an endangered California Ridgway’s rail (Rallus obsoletus obsoletus), the result of environmental extremes and a series of species interactions.

Other papers published in this issue look at a predictive model for commercial catch of white seabass (Atractoscion nobilis); fecundity and reproductive potential of wild female Delta Smelt (Hypomesus transpacificus); and updated information on the length-weight relationships (LWR) and length-length relationships (LLR) and condition factors for pelican barracuda (Sphyraena idiastes) in the Gulf of California.

New in this issue is a section called “From the Archives,” which reprints articles from past issues to provide historical perspective on topics still relevant today. The first article in this series comes from Volume I, Issue I, dated 1914. It asserts that natural resources must be conserved for the use and enjoyment of the public.

Download the entire Fall Issue 102 in high resolution, or browse individual articles in low resolution.

The California Department of Fish and Wildlife (CDFW) recently launched the first phase of a multi-year study of tule elk in Colusa and Lake counties. In partnership with the University of California, Davis and the Rocky Mountain Elk Foundation, and with the assistance of capture specialists from Leading Edge Aviation, researchers used helicopter net guns to capture and place satellite collars on 45 tule elk.

The technique of using DNA extracted from fecal pellets to study wildlife populations is a relatively new, non-invasive approach that minimally disturbs animals and enables surveys in low-visibility habitats where sight-based surveys would be relatively ineffective. It is also less costly than other survey methods, and therefore can be used more frequently.

While fecal DNA analysis has been used to estimate abundance and other population parameters in deer herds in California since 2011, this study will be the first application of the technique to free-ranging tule elk. The study results will guide future elk conservation planning efforts.

Tule elk are a native subspecies of elk unique to California. Prior to the arrival of European settlers, they numbered more than half a million statewide, but the population rapidly declined in the mid-1800s due to unregulated market hunting and habitat loss. In 1875, a ranch owner in Kern County took efforts to protect the last remaining tule elk and allowed them to multiply on his property, likely saving them from extirpation.

Since 1975, CDFW has captured and relocated more than 1,500 elk. As a result, there are an estimated 5,100-plus tule elk distributed in 22 herds throughout California today. See more information about the distribution, range and history of this unique animal in California.

About 10 environmental scientists from CDFW’s Office of Spill Prevention and Response (OSPR) participated in a large-scale oil spill drill along the Feather River on March 21. The drill was intended to help wildlife response teams prepare for a potential train derailment. OSPR has a long history of oil spill response in marine environments but recently expanded its scope statewide to include inland waters. This Feather River exercise was the first time a substantial wildlife response drill has been held inland, testing responders’ abilities to resolve many operational and technical issues presented by a river spill.

Whereas marine spills typically require rescue of seabirds and occasionally marine mammals, the kinds of animals potentially affected by inland spills are quite different and varied, potentially including raptors, songbirds, reptiles, amphibians, rodents, foxes, and other mammals. The need to capture and care for these species during an oil spill presents unique challenges for scientist responders. The goal is to have the necessary protocols in place and practiced.

The drill was put on by the California Oiled Wildlife Care Network (OWCN), an organization funded by OSPR and managed by the UC Davis School of Veterinary Medicine to provide best achievable care of oiled wildlife. The OWCN currently maintains a network of 40 wildlife rehabilitation organizations, trained and ready to respond to oil spills anywhere in the state. Sixteen of these organizations participated in Tuesday’s drill, including two local organizations, Shasta Wildlife Rescue and Rehabilitation and North Valley Animal Disaster Group.

In addition to practicing wildlife response activities, the drill provided the opportunity to test a new Geographic Response Plan (GRP) for the Feather River. GRPs identify the location and nature of resources at risk in the event of a spill, and outline appropriate tactical response strategies to minimize oiling and other injury. During a real spill, OSPR environmental scientists serve as subject-matter experts who help ensure that the GRP is implemented appropriately. A simulated situation like this one gives them a valuable opportunity to conduct a realistic ‘dry run,’ as well as to analyze elements of the GRP and make adjustments as necessary.

To learn more about OSPR, visit www.wildlife.ca.gov/OSPR.

Pronghorn antelope (Antilocapra americana) were once one of the most numerous large mammals in California, with populations estimated to have been as high as 500,000 prior to the Gold Rush era. In the mid-1800s, pronghorn were nearly extirpated by market-shooting to feed California’s rapidly expanding human population.

The remaining population of pronghorn has long been understudied. Prior data collected on the species have been limited to herd counts and habitat selection. In recent years, there has been growing concern over pronghorn populations, particularly in northeastern California. During the harsh winter of 1992, the number of pronghorn dropped almost 50 percent to an estimated 5,000 individuals. The northeastern portion of the state currently supports a population of approximately 4,500 animals that occur primarily in Modoc, Lassen, Siskiyou and Shasta counties and has been fairly stable, with slow declines, since about 2000. The herd’s inability to rebound has prompted scientists to try to understand the specific conditions leading to the declines.

In 2016 the Institute for Wildlife Studies (IWS) completed a two-year study, with funding from CDFW’s Big Game Management Account, which explored aspects of the pronghorn population on the Modoc Plateau. The study involved 48 does (adult females) and 42 fawns that were radio-collared and followed until their deaths or the study’s end. The researcher’s objectives were to learn more about the pronghorn use of habitat, aspects of their reproduction and factors affecting survival of does and fawns.

The researchers found that for most of the year, pronghorn used open areas with less shrubby and more herbaceous vegetation within their sagebrush-steppe habitats. But during fawning, when does need to hide their young, they shifted to spending more time in areas with greater densities of shrubs and juniper trees. The annual survival rate for does in the study was 69 percent, which is low compared to other pronghorn populations. Mountain lions accounted for 80 percent of predator-related mortalities, most of which occurred during and just after the peak birthing period when does are most vulnerable. Fawn survival averaged 44 percent, a higher-than-typical figure, with unknown causes (37.5 percent) or suspected coyote predation (21 percent) accounting for most fawn mortalities.

The adults’ increased use of shrubby areas and conifer woodlands during fawning suggests an important factor in the population’s continued decline. Juniper woodlands have been encroaching on the sagebrush-steppe habitat in the Modoc Plateau for decades, and these juniper trees provide areas of concealment for ambush predators such as mountain lions. Most ungulate studies demonstrate that adult survival plays a more critical role in population stability than juvenile survival. CDFW may be able to reduce adult pronghorn mortality through habitat restoration – the removal of encroaching junipers could help to reduce predations by lions, and potentially increase the Modoc pronghorn population.

Read complete report.

For some public properties, livestock grazing can be an important land management tool to help maintain specific habitat conditions, control invasive weeds and reduce fire hazards. In areas invaded by non-native vegetative species, it is necessary to control vegetation height and density in order to keep habitats functioning for certain sensitive species. For instance, the burrowing owl requires low vegetation cover in order to forage for prey effectively and prevent predators from approaching unseen. Other species that have been known to benefit from managed livestock grazing include California tiger salamander, Yosemite toad and certain sensitive butterfly species.

Controlling the height and density of non-native annual grasslands through grazing has also been shown to help increase forage efficiency for many species of raptors, and it’s used as a tool in some areas of California to maintain sensitive vernal pool habitats.

For years, local, state and federal agencies, as well as non-government organizations, have utilized livestock grazing on public lands. It is important to have many tools available for habitat management because it can sometimes be complicated. Factors such as the presence of listed or protected species, compatible public land uses and erosion -- as well as other land management practices such as herbicide application, mowing and prescribed fires -- must all be considered.

CDFW’s Rancho Jamul Ecological Reserve in San Diego County recently hosted a livestock grazing workshop presented by Rancher to Rancher (R2R) program spokesperson Kent Reeves, and UC Davis researcher Dr. Christina Wolf. The goal of the R2R program is to provide information and educational resources to private ranchers about evolving livestock management practices intended to promote native ecosystem health, and therefore, more sustainable grazing programs. More than 40 participants, including local private ranchers and representatives from about a dozen government and non-government organizations attended the workshop. Participants learned about developing progressive management practices, such as the use of increased stocking densities for shorter, more frequent durations, in order to increase carbon sequestration in the soils. This method is currently being studied as a way of encouraging native grass species as well as combating changing climate conditions.