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The Coastal California Gnatcatcher (Polioptila californica californica), a federally threatened species, is a flagship species for regional conservation planning in southern California (USA). An inhabitant of coastal sage scrub vegetation, the gnatcatcher has declined in response to habitat loss and fragmentation, exacerbated by catastrophic wildfires. We documented the status of gnatcatchers throughout their California range and examined post-fire recovery of gnatcatchers and their habitat. We used GIS to develop a habitat suitability model for Coastal California Gnatcatchers using climate and topography covariates and selected over 700 sampling points in a spatially balanced manner. Bird and vegetation data were collected at each point between March and May in 2015 and 2016. Presence/absence of gnatcatchers was determined during three visits to points, using area searches within 150 x 150 m plots. We used an occupancy framework to generate Percent Area Occupied (PAO) by gnatcatchers, and analyzed PAO as a function of time since fire. At the regional scale in 2016, 23% of the points surveyed were occupied by gnatcatchers, reflecting the effect of massive wildfires in the last 15 years. Similarly, PAO in the post-fire subset of points was 24%, with the highest occupancy in unburned (last fire <2002) habitat. Positive predictors of occupancy included percent cover of California sagebrush (Artemisia californica), California buckwheat (Eriogonom fasciculatum), and sunflowers (Encelia spp., Bahiopsis laciniata), while negative predictors included laurel sumac (Malosma laurina) and total herbaceous cover; in particular, non-native grasses. Our findings indicate that recovery from wildfire may take decades, and provide information to speed up recovery through habitat restoration. [ABSTRACT FROM AUTHOR]

Under the Endangered Species Act, the U.S. Fish and Wildlife Service is required to designate critical habitat (CH) for listed species. Designation could result in modification to or delay of residential development projects within habitat boundaries, generating concern over potential housing market impacts. This paper draws upon a large data set of municipal-level (FIPS) building permit issuances and critical habitat designations (CHDs) in California over a 13-year period to identify changes in the spatial and temporal pattern of development activity associated with CHD. We find that the proposal of the median-sized CH results in a 23.5 percent decrease in the supply of housing permits in the short run and a 37.0 percent decrease in the long run. The results indicate the proposal of CH acts as a signal that all development in that FIPS will be more costly. We also find that the impact varies across the two periods in which CH is designated and by the number of years relative to when CH was first proposed. [ABSTRACT FROM AUTHOR]

Copyright of Western North American Naturalist is the property of Monte L. Bean Life Science Museum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Positive associations between animals and foundational shrub species are frequent in desert ecosystems for shelter, resources, refuge, and other key ecological processes. Herein, we tested the impact of the density of the shrub species Ephedra californica on the presence and habitat use of the federally endangered lizard species, Gambelia sila. To do this, we used a 3‐year radio telemetry dataset and satellite‐based counts of shrub density across sites at the Carrizo Plain National Monument in San Luis Obispo County, CA. The effect of shrub density on lizard presence was contrasted with previous shrub cover analyses to determine whether measures of shrub density were superior to shrub cover in predicting lizard presence. Increasing shrub density increased lizard presence. As shrub density increased, lizards were located more frequently "above ground" versus "below ground" in burrows. Male lizards had significantly larger home ranges than females, but both sexes were similarly associated with increasing shrub densities. Shrub density and shrub cover models did not significantly differ in their prediction of lizard presence. These findings suggest that both habitat measures are effective analogs and that ecologically, both cover and the density of foundation shrub species are key factors for some desert lizards. [ABSTRACT FROM AUTHOR]

The Sweetwater Authority's urban runoff diversion system (URDS) comprises constructed wetlands on a hillside between the town of Spring Valley and the Sweetwater Reservoir, California, USA. The URDS were designed to divert dry-weather and first-flush urban runoff flows from the Sweetwater reservoir. However, these constructed wetlands have developed into ecologically valuable habitat. This paper evaluates the following ecological questions related to the URDS: (1) the natural development of the species present and their growth pattern; (2) the biodiversity and pollutant stress on the plants and invertebrates; and (3) the question of habitat provided for endangered species. The URDS wetlands are comprised primarily of rush (Scirpus spp.) and cattails (Typha spp.). This vegetative cover ranged from 39-78% of the area of the individual wetland ponds. Current analyses of plant tissues and wetland sediment indicates the importance of sediment sorption for metals and plant uptake of nutrients. Analyses of URDS water following runoff events show the URDS wetlands do reduce the amount of nutrients and metals in the water column. Invertebrate surveys of the wetland ponds revealed lower habitat quality and environmental stress compared to unpolluted natural habitat. The value of the wetlands as wildlife habitat is constrained by low plant biodiversity and pollution stress from the runoff. Since the primary Sweetwater Authority goal is to maintain good water quality for drinking, any secondary utilization of URDS habitat by species (endangered or otherwise) is deemed an added benefit. [ABSTRACT FROM AUTHOR]

A recent global trend toward retirement of farmland presents opportunities to reclaim habitat for threatened and endangered species. We examine habitat restoration opportunities in one of the world’s most converted landscapes, California’s San Joaquin Desert (SJD). Despite the presence of 35 threatened and endangered species, agricultural expansion continues to drive habitat loss in the SJD, even as marginal farmland is retired. Over the next decades a combination of factors, including salinization, climate change, and historical groundwater overdraft, are projected to lead to the retirement of more than 2,000 km2 of farmland in the SJD. To promote strategic habitat protection and restoration, we conducted a quantitative assessment of habitat loss and fragmentation, habitat suitability, climatic niche stability, climate change impacts, habitat protection, and reintroduction opportunities for an umbrella species of the SJD, the endangered blunt-nosed leopard lizard (Gambelia sila). We use our suitability models, in conjunction with modern and historical land use maps, to estimate the historical and modern rate of habitat loss to development. The estimated amount of habitat lost since the species became protected under endangered species law in 1967 is greater than the total amount of habitat currently protected through public ownership and conservation easement. We document climatic niche contraction and associated range contraction away from the more mesic margins of the species’ historical distribution, driven by the anthropogenic introduction of exotic grasses and forbs. The impact of exotic species on G. sila range dynamics appears to be still unfolding. Finally, we use NASA fallowed area maps to identify 610 km2 of fallowed or retired agricultural land with high potential to again serve as habitat. We discuss conservation strategies in light of the potential for habitat restoration and multiple drivers of ongoing and historical habitat loss. [ABSTRACT FROM AUTHOR]

Copyright of Western North American Naturalist is the property of Monte L. Bean Life Science Museum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

White sharks are highly migratory and segregate by sex, age and size. Unlike marine mammals, they neither surface to breathe nor frequent haul-out sites, hindering generation of abundance data required to estimate population size. A recent tag-recapture study used photographic identifications of white sharks at two aggregation sites to estimate abundance in “central California” at 219 mature and sub-adult individuals. They concluded this represented approximately one-half of the total abundance of mature and sub-adult sharks in the entire eastern North Pacific Ocean (ENP). This low estimate generated great concern within the conservation community, prompting petitions for governmental endangered species designations. We critically examine that study and find violations of model assumptions that, when considered in total, lead to population underestimates. We also use a Bayesian mixture model to demonstrate that the inclusion of transient sharks, characteristic of white shark aggregation sites, would substantially increase abundance estimates for the adults and sub-adults in the surveyed sub-population. Using a dataset obtained from the same sampling locations and widely accepted demographic methodology, our analysis indicates a minimum all-life stages population size of >2000 individuals in the California subpopulation is required to account for the number and size range of individual sharks observed at the two sampled sites. Even accounting for methodological and conceptual biases, an extrapolation of these data to estimate the white shark population size throughout the ENP is inappropriate. The true ENP white shark population size is likely several-fold greater as both our study and the original published estimate exclude non-aggregating sharks and those that independently aggregate at other important ENP sites. Accurately estimating the central California and ENP white shark population size requires methodologies that account for biases introduced by sampling a limited number of sites and that account for all life history stages across the species' range of habitats. [ABSTRACT FROM AUTHOR]

The endangered Ohlone tiger beetle ( Cicindela ohlone) depends on bare ground areas in California coastal grasslands to encounter mates, oviposit, and find prey. We tested habitat creation as a potential management strategy to increase the availability of oviposition sites for C. ohlone. We compared three different bare ground treatments by scraping off surface vegetation, ripping, and tamping the plots. We also tested whether bare ground creation expands C. ohlone range within a habitat patch by scraping plots at increasing distances from the core habitat and monitoring C. ohlone colonization. C. ohlone oviposited significantly more in artificial bare ground plots compared to controls both one and 2 years after the scrapes were created. Distance from the core habitat did not affect colonization nor did decompaction of scraped plots. Percent bare ground significantly predicted incidence of colonization. For the conservation of the endangered Ohlone tiger beetle, we recommend continued creation of scraped plots every 2 years in order to maintain bare ground and to ensure maximum usage by female C. ohlone as oviposition sites. [ABSTRACT FROM AUTHOR]

The marbled murrelet (Brachyramphus marmoratus) is an endangered seabird that nests in coastal forests from Alaska to California. The value of these forests for human use, coupled with the difficulty of determining whether a forest stand is occupied by nesting marbled murrelets, poses a dilemma for land managers. Should they implement a costly survey to gather information on whether a potential nest site is occupied, or should they allow human use, effectively assuming the site is unoccupied? This article demonstrates the application of the partially observable Markov decision process (POMDP) as a framework for addressing this question. The analysis yields a policy in which the optimal action is a function of the decision-maker's subjective probability that a potential nest site is occupied by marbled murrelets. By incorporating stochastic state dynamics and the choice of whether to invest in learning, the POMDP provides a formal representation of adaptive management when active learning is possible. [ABSTRACT FROM AUTHOR]

San Joaquin kit foxes (Vulpes macrotis mutica) occur in central California, USA, and are endangered due to habitat loss and degradation. As the human population of California grows, more roads are being constructed in remaining kit fox habitat. We examined effects of 2-lane roads on demographic and ecological patterns of kit foxes on the Lokern Natural Area (LNA) from August 2001 to June 2004. Of 60 radiocollared kit foxes, only one was struck by a vehicle. Foxes were assigned to 1 of 3 risk categories (high, medium, or low) based on proportion of time spent in road-effect zones, which were defined by the probability of a fox encountering a road during nocturnal movements. Fox survival probabilities, reproductive success, litter size, nocturnal movements, and den placement all were similar among risk categories. Nocturnal locations of foxes were closer to roads than were den locations, and den fidelity was lowest for medium-risk foxes and highest for low-risk foxes but intermediate for high-risk foxes. Food availability and use were not affected by proximity to roads. We were unable to detect any significant detrimental effects from 2-lane roads on kit fox demography and ecology. Our results suggest that standard mitigation strategies, such as crossing structures and exclusionary fencing, would not benefit kit foxes on the LNA. [ABSTRACT FROM AUTHOR]

The San Francisco Bay Area hosts a diverse insect fauna and a dense cluster of urban areas. The high diversity of insects in the Bay Area arises for three primary reasons: its location in the California biotic province, the diverse local environment and the entomologist-area effect. The juxtaposition of high insect diversity and an area intensively used by humans led to the first recorded extinction as well as the first efforts to conserve insects in the United States. Habitat loss due to urbanization, agriculture, and invasive species is largely responsible for local extinctions and reduction in abundance of the remaining species. Invasive species such as the Argentine ant and pathogens causing mortality of oaks and pines are poised to have substantial impacts on the insect fauna of the Bay Area in the near future. Understanding which taxa can or cannot persist in remnant habitat patches within an urban or agricultural matrix, and what management practices would encourage persistence should be a focus of future research. Assessments of population status should be focused on insects at risk of extinction because of their restricted geographic ranges, low vagility, interactions with invasive species, or known reduction in their habitat. Assessments that combine examinations of museum collections, literature, and field surveys might enable determination of the status of many species within the Bay Area. Such an approach might better define the scope and magnitude of the problem of conserving insects in an increasingly urbanized region. [ABSTRACT FROM AUTHOR]

Degradation of sagebrush habitat and a lack of information on current status motivated a petition to list the pygmy rabbit (Brachylagus idahoensis) as threatened or endangered under the Endangered Species Act. The petition brought on renewed interest in obtaining data on pygmy rabbits; however, pygmy rabbits are notoriously difficult to capture, especially in summer. We tested box-trap, net, noose-pole, and fabric-fence methods to capture pygmy rabbits in 4 areas of northern Nevada and eastern California, USA. We captured 25 different pygmy rabbits in 30 captures from April 2005 to July 2006. The combination of camouflaged box traps baited with canned green beans was 35% more successful and required less effort per captured rabbit than any other method. Noose-pole methods also were successful. These techniques provide an efficient method of capturing pygmy rabbits in summer when many remote field sites are most accessible. [ABSTRACT FROM AUTHOR]