Patrick A. Kelly

Distances Moved by Stephens' Kangaroo Rat (Dipodomys stephensi Merriam) and Implications for Conservation

Movements by Dipodomys stephensi were assessed by live-trapping and radiotelemetry to evaluate consequences of habitat fragmentation for this endangered species. The median of the maximum distances moved between captures was 29.2 m for the 557 individuals with ≥2 captures. The median distance between first and last monthly home-range centers was 17.6 m for individuals captured in ≥2 months. Males moved longer distances than did females; lactating females were especially sedentary. Dispersal distances were similar for juveniles and adults and for two sites with different geometries of habitat patches. The median distance between first and last home-range center of adults radiotracked for 15–127 days was 9.5 m, indicating stable home ranges. However, radiotracked individuals moved greater maximum distances than most live-trapped individuals apparently moved over a lifetime. Much dispersal, therefore, occurs within an area about which animals have knowledge. This should facilitate habitat selection and decrease the cost of dispersal in terms of fitness. The frequency distribution of maximum dispersal distances underestimated the frequency of moves >400 m. Two processes may have contributed to this bias. First, the frequency of long-distance moves was underestimated because we measured dispersal away from a single grid. Second, our trapping grids were located in homogeneous habitat without dirt roads, which appear to facilitate long-distance movement. Unvegetated corridors show promise for increasing the connectedness of local populations of D. stephensi . Connectedness should be considered in management of endangered species such as D. stephensi , because the expected persistence of metapopulations is sensitive to the extent of dispersal and the fitness of dispersers.

Optimizing reserve expansion for disjunct populations of San Joaquin kit fox

Expanding habitat protection is a common strategy for species conservation. We present a model to optimize the expansion of reserves for disjunct populations of an endangered species. The objective is to maximize the expected number of surviving populations subject to budget and habitat constraints. The model accounts for benefits of reserve expansion in terms of likelihood of persistence of each population and monetary cost. Solving the model with incrementally higher budgets helps prioritize sites for expansion and produces a cost curve showing funds required for incremental increases in the objective. We applied the model to the problem of allocating funds among eight reserves for the endangered San Joaquin kit fox (Vulpes macrotis mutica) in California, USA. The priorities for reserve expansion were related to land cost and amount of already-protected habitat at each site. Western Kern and Ciervo-Panoche sites received highest priority because land costs were low and moderate amounts of already-protected habitat resulted in large reductions in extinction risk for small increments of habitat protection. The sensitivity analysis focused on the impacts of kit fox reproductive success and home range in non-native grassland sites. If grassland habitat is lower quality than brushland habitat resulting in higher annual variation in reproductive success or larger home ranges, then protecting habitat at the best grassland site (Ciervo-Panoche) is not cost-efficient relative to shrubland sites (Western Kern, Antelope Plain, Carrizo Plain). Finally, results suggested that lowest priority should be given to three relatively high-cost grassland sites (Camp Roberts, Contra Costa, and Western Madera) because protecting habitat at those sites would be expensive and have little effect on the expected number of surviving kit fox populations.

RELATIVE ABUNDANCE OF ENDANGERED SAN JOAQUIN KIT FOXES (VULPES MACROTIS MUTICA) BASED ON SCAT-DETECTION DOG SURVEYS

Abstract Although the San Joaquin kit fox (Vulpes macrotis mutica) has been a federally protected subspecies since 1967, current information on its status throughout much of its historical range is lacking. Since 1983, only 5 surveys have been conducted, and a recent recovery plan emphasized the need for better information on the status of this subspecies. Between 2001 and 2003, we attempted to obtain new information on this kit fox on specific public and private properties in 8 counties in the San Joaquin Valley, California, where knowledge of its current status was limited or poorly understood. We used a trained detection-dog to survey for kit fox, red fox (V. vulpes), and gray fox (Urocyon cinereoargenteus) scats on selected properties, followed by species identification based on genetic analysis of DNA extracted from all scats collected. Despite extensive survey efforts (539 km), kit fox was only detected in Merced County, in the area of Santa Nella, where a small kit fox population was previously documented. Red fox scats were located in Alameda, San Joaquin, and Merced counties, and gray fox scats were located in Fresno County. Our results suggest that if kit foxes are present on the properties surveyed, they either occur at extremely low densities, rendering detection difficult, or only occur intermittently in these areas. In striking contrast, our previous surveys conducted with the same method in the southern part of the range found large numbers of kit fox scats in various areas, particularly in Kern and San Luis Obispo counties. We recommend that future conservation plans focus on preserving additional habitat in areas where kit foxes are relatively abundant, specifically western Kern County and the Ciervo-Panoche region.

The Challenge of Locating Seed Sources for Restoration in the San Joaquin Valley, California

ABSTRACT: In the San Joaquin Valley of California, land conversion for agricultural and urban uses has resulted in profound habitat loss and diminished biological diversity. However, the large-scale retirement (i.e., removal from irrigated agricultural production) of farmland in the western San Joaquin Valley presents an opportunity to restore native plant communities and wildlife habitat values. A key objective of the proposed restoration efforts was to utilize local seed sources to the extent possible. However, local genotypes of San Joaquin Valley native plants are largely unavailable from commercial seed suppliers, and the amount of seed that could be collected from areas of native habitat would be insufficient for reseeding large tracts of retired farmland. Accordingly, we initiated a regional search for local native plant populations from which seeds could be collected and planted in a field nursery for the purpose of seed production. We identified 41 areas of remnant native habitat (sites) that supported 158 native plant species. The majority of the populations were restricted to isolated habitat remnants. Many of the species were uncommon: 65% were documented at three or fewer sites. The number of species per site was generally low; over half of the sites supported 10 or fewer species. This investigation illustrates the difficulty of identifying local native seed sources for restoration purposes in a highly fragmented landscape.

USE OF AGRICULTURAL LANDS BY SAN JOAQUIN KIT FOXES

Abstract Although the current range of the endangered San Joaquin kit fox (Vulpes macrotis mutica) borders large areas of farmland, the ecology of this species rarely has been studied within an agricultural setting. In central California, we examined habitat use, prey availability, and diet of radio-collared kit foxes inhabiting an aqueduct right-of-way (ROW) bordered by farmland. During both years of study (1998–1999), nocturnal locations of foxes occurred more often than expected (based on habitat availability) in the ROW and less often than expected within annual crops. Orchards were used disproportionately more than their availability during 1998 and were used in proportion to availability during 1999. Kit foxes traveled up to 1.1 km into annual crops and up to 1.5 km into orchards. Among diurnal locations (den sites) of foxes, 98% were within the ROW. Live-trapping revealed higher densities and greater diversity of rodents along the ROW than within farmland. Remains of murid rodents were found in 79% of kit fox scats. Our findings indicated that kit foxes ranged into orchards and annual croplands at night, but almost never occupied these areas during the day. The lack of den sites and low prey availability within farmland probably limited the ability of kit foxes to exploit and occupy these areas. Providing artificial den sites within croplands (especially within orchards) and along canals may increase use of farmland by kit foxes and facilitate their movement between isolated patches of natural lands.

Home range size and habitat selection of reintroduced Sylvilagus bachmani riparius

Abstract Effective restoration of threatened or endangered species requires understanding of basic ecological requirements such as habitat selection and home range needs. The endangered riparian brush rabbit (Sylvilagus bachmani riparius) occupies areas of dense, brushy cover along streamside communities in the San Joaquin Valley of California, but over 93% of this habitat has been lost to urban and agricultural development. We released over 325 captive-born rabbits at the San Joaquin River National Wildlife Refuge (Refuge) between July 2002 and July 2005, and we monitored 312 of these rabbits via radiotelemetry to assess spatial and habitat selection. Home ranges and core areas were similar among males and females, and were larger in the breeding season than during the nonbreeding season. Perhaps reflecting a growing population, home range estimates decreased in size over the duration of the study. Animals moved in response to a wildfire in July 2004, but home range area was similar in 90-day pre- and postfire periods. Of 1,143 possible dyads, 534 (47%) exhibited a mean of 86% overlap in 95% fixed-kernel home ranges. Overlap did not differ by dyad type (e.g., male–male), but was greater in nonbreeding than in breeding seasons; unlike home ranges, we did not detect any temporal changes in overlap as might be expected in a growing population. Riparian brush rabbits exhibit scale-independent habitat selection, disproportionately favoring thick understory cover such as sandbar willow mixed with dense shrubs (blackberry, roses). Refuge managers have promoted escape cover and flood refugia at strategic locations throughout the Refuge; our results concur that these are important habitat elements in the niche of riparian brush rabbits.

Use of Simulation Modeling to Evaluate Management Strategies for Reintroduced Riparian Brush Rabbits in California

Abstract The riparian brush rabbit Sylvilagus bachmani riparius is restricted to areas of dense cover along rivers and tributaries in the Central Valley of California, USA, and is considered endangered under the U.S. Endangered Species Act. An approved recovery plan for this subspecies recommended establishment of three additional self-sustaining populations within its historical range. Concurrent with habitat restoration efforts that included revegetation of levees and provision of flood refugia, we reintroduced 325 captive-bred individuals to the San Joaquin River National Wildlife Refuge between July 2002 and July 2005, and monitored their survival with radiotelemetry. Using available survival estimates and estimated reproductive parameters, we developed a population viability analysis model to determine the risk of extinction of the reintroduced population under a series of alternate scenarios including different release strategies. All model scenarios resulted in high probabilities of extinction over...

Mesocarnivore Surveys on Lawrence Livermore National Laboratory Site 300, Alameda and San Joaquin Counties, California

Lawrence Livermore National Laboratory (LLNL), operated under cooperative agreement between the University of California and the U. S. Department of Energy, administers and operates an approximately 11 mi{sup 2} (28 km{sup 2}) test site in the remote hills at the northern end of the South Coast Ranges of Central California (Figure 1). Known as Site 300, this expanse of rolling hills and canyons supports a diverse array of grassland communities typical of lowland central California. The facility serves a variety of functions related to testing non-nuclear explosives, lasers, and weapons subsystems. The primary purpose of this project was to determine the presence of any mesocarnivores on Site 300 that use the property for foraging, denning, and other related activities. The surveys occurred from mid-September to mid-October, 2002.