Science Spotlight

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.

Since 1959 the California Department of Fish and Wildlife (CDFW) has used a combination of scientific techniques to better understand fish populations and the general health of Northern California waterways. Examples include tagging sturgeon, trawling the Delta for smelt, and counting salmon carcasses. CDFW uses data from these strategies and others to help influence operations of the State Water Project and Central Valley Project, ultimately helping decision makers determine water flows. This short video highlights these operations along the Sacramento River and into the Delta, including a smelt survey conducted by Environmental Scientist Felipe la Luz.

Arborimus albipes, a CA Critically Imperiled Species of Special Concern

The white-footed vole is one of the least-studied (and most difficult to catch!) mammals in North America. CDFW Environmental Scientist Dr. Scott Osborn, his collaborator Dr. Tim Bean of Humboldt State University’s Wildlife Department, and a small team of field biologists know that better than anyone – they spent the summer of 2014 setting traps for them in Humboldt and Del Norte counties. Designated a Species of Special Concern by CDFW, only nine records of the species were known in California prior to their study, which was aimed at determining how environmental conditions, such as climate (and future climate change), might affect their distribution.

Habitat modeling by Bean (based on the previous records) identified areas with high habitat suitability for the white-footed vole. Ten study sites were chosen along the North Coast for the field study, including three where voles had been successfully trapped in the 1990s. Using live traps (both pitfall traps made of two coffee cans taped together and Sherman live traps baited with oats and peanut butter), the team successfully trapped three voles. Notably, one of these was the first recorded capture of a white-footed vole in Del Norte County. All three voles were returned unharmed to their capture site after basic measurements and assessments of food plant preferences were made.

Although three voles might not seem like a large return on the investment of many hours of field work, the team actually had one of the highest capture rates of white-footed voles of any small mammal study in its geographic range, which includes coastal Oregon and the North Coast of California. Vegetation plots suggest that white-footed voles are tightly associated with stands of red alder trees – so now the biologists know that’s a likely place to find them. The habitat modeling work indicates that suitable habitat may currently exist as far south as Mendocino County, which is outside the known geographic range of the vole. On the other hand, it is possible that this species’ range may contract northward in a warmer and drier future. Open the Full Report (PDF)

California’s recreational fishery resource provides a huge benefit to the state’s economy. In the latest issue (102-3) of the scientific journal California Fish and Game, Reid et. al tackles the difficult task of quantifying the economic value of California’s recreational red abalone (Haliotis rufescens) fishery.

Using data for the 2013 season at more than 50 sites in Sonoma and Mendocino counties, the authors used the travel-cost estimation method to determine a value. According to their findings, the 31,000 people who fish for red abalone provide an economic benefit to California of between $24M and $44M annually.

The lower figure was derived solely by determining the costs involved in driving to the fishing locations, while the higher figure considers the time spent on the fishing activity. The data reveal three dominant criteria used to select fishing sites: 1) the presence of a harmful algal bloom — and the resulting stricter fishing regulations — in Sonoma County; 2) protection from ocean swells; and 3) the presence of recreational conveniences such as restrooms and boat launches.

Determining the economic value of the red abalone fishery puts into perspective the importance of managing it for sustainability. Other articles in this issue focus on management implications for California halibut (Paralichthys californicus) and Olympia oysters (Ostrea lurida).

Lesyna and Barnes report that California halibut reach physical maturity at different sizes and ages, depending upon location. Macroscopic examination of specimens revealed that, although all halibut were mature before reaching the commercial and recreational minimum legal size limit, central California halibut are larger and older by the time they reach physical maturity than their southern California counterparts.

Moore et. al studied the sexual development and symbionts of Olympia oysters (Ostrea lurida) that settled naturally on artificial clutches placed in San Francisco Bay. The results of the study suggest that Olympia oysters have the capacity to flourish when suitable habitat is available.

Collectively, these articles demonstrate the importance of studying natural resources for their consumptive and non-consumptive value.

According to California Fish and Game Editor-in-Chief Armand Gonzales, the articles provide critical direction for resource management. “It is therefore incumbent upon us as scientists, to keep working, keep studying and keep reporting what we see and find.