Brian L. Cypher

Effects of nest location on depredation of artificial arboreal nests

Depredation on artificial arboreal nests was studied in 1-ha aspen (Populus spp.) plots on a ruffed grouse (Bonasa umbellus) management area in central Pennsylvania from May to August 1985. Predation was evaluated with respect to 2 factors associated with nest placement: height of nest aboveground and plot age. American crows (Corvus brachyrhynchos) were the major nest predator. Fewer low nests (0.5 m aboveground) were disturbed than high nests (1.5 m), and more nests were disturbed in both 8-year-old and mature plots than in 4-year-old plots. Low nests in 4-year-old plots were least susceptible to depredation. Dense shrub growth in 4-year-old plots presumably reduced the foraging efficiency of predators, thereby lowering the probability of disturbing low nests. Young clearcuts provide well-concealed nest sites for avifauna that construct nests near ground level in shrubby vegetation. J. WILDL. MANAGE. 51(1):178-181 Predation is a major factor reducing nesting success in birds (Ricklefs 1969). Avian predators may have a greater impact than large mammalian predators on nests located high in small trees and shrubs than nests positioned close to ground level (Joern and Jackson 1983, Shalaway 1985). The relationship between nest height and susceptibility to disturbance by predators may vary with habitat type. For instance, Caccamise (1977) found that in tidal marshes, the percentage of successful nests decreased as nest height increased, whereas Best and Stauffer (1980) noted that fledging success was greater in higher nests (1-2 m aboveground) compared to that of lower nests (<1 m) in riparian habitats. In general, avian nests, particularly those located near ground level, may be less conspicuous to predators when located in areas with complex vegetative structure (Bowman and Harris 1980, Redmond et al. 1982, Yahner and Wright 1985). An even-aged system of forest clearcutting provides suitable habitat for a variety of songbird species that construct nests near (<2 m) ground level (Yahner 1986b). The objective of this study was to compare depredation on artificial arboreal nests placed at 2 heights above ground level in small aspen plots of 3 age classes (time since clearcutting) and, hence, different vegetative structure. We thank E. A. Cypher and R. L. Schooley for field assistance and L. B. Best, D. P. Scott, and R. D. Shipman for comments on the manuscript. This study was supported by the Pa. Agric. Exp. Stn. and the Max McGraw Wildl. Found. This is J. Ser. Pap. 7417 of the Pa. Agric. Exp. Stn., The Pennsylvania State Univ., University Park.

Competitive Interactions between Coyotes and San Joaquin Kit Foxes

Competitive interactions between coyotes ( Canis latrans ) and federally endangered San Joaquin kit foxes ( Vulpes macrotis mutica ) were investigated at the Naval Petroleum Reserves in California (NPRC) during 1984–1995. Coyotes and kit foxes used similar food items, indicating the potential for exploitative competition. Leporids were the primary prey for coyotes in all years, but small rodents were the primary prey for kit foxes in most years, although leporids were primary prey in other years. Coyotes were the main cause of mortality to kit foxes at NPRC, indicating that interference competition may be occurring. Population trends of kit foxes appeared to be strongly influenced by food availability, but competition from coyotes also may have affected population dynamics of kit foxes. Mechanisms employed by kit foxes, such as resource partitioning, greater dietary breadth, and year-round den use, may facilitate coexistence with coyotes. However, use of anthropogenic food sources by coyotes may intensify competitive interactions during periods of low prey availability.

Effects of Habitat on Competition Between Kit Foxes and Coyotes

Abstract San Joaquin kit foxes (Vulpes macrotis mutica) are an endangered species with a narrow geographic range whose natural populations are limited by predation by coyotes (Canis latrans). In the warm, arid grassland and shrubland habitats where kit foxes occur, coyotes are more cover dependent than kit foxes, creating the possibility of habitat segregation. Effects of habitat variation on coyote and kit fox competition are unknown. We assessed exploitation and interference competition between coyotes and kit foxes in grassland and shrubland habitats to determine if such competition varies among habitats. With respect to exploitation competition, we evaluated habitat and spatial partitioning, diet, prey abundance, and survival for kit foxes and coyotes at the Lokern Natural Area in central California, USA, from January 2003 through June 2004. Kit foxes partitioned habitat, space, and diet with coyotes. Coyotes primarily used shrubland habitats whereas kit foxes selectively used burned grasslands. Kit foxes and coyotes had high dietary overlap with regards to items used, but proportional use of items differed between the 2 species. Kit foxes selected for Heermanns kangaroo rats (Dipodomys heermanni), which were closely tied to shrub habitats. With respect to interference competition, predation was the primary source of mortality for kit foxes, and survival of individual kit foxes was inversely related to proportion of shrub habitat within their home ranges. Our results suggest that a heterogeneous landscape may benefit kit foxes by providing habitat patches where predation risk may be lower.

Dispersal Patterns of San Joaquin Kit Foxes (Vulpes Macrotis Mutica)

Abstract We investigated dispersal patterns of San Joaquin kit foxes (Vulpes macrotis mutica) on the Naval Petroleum Reserves, California. Of 209 juvenile kit foxes monitored during 1980–1996, 33% dispersed from their natal territory. Significantly more males (49.4%) than females (23.8%) dispersed, and dispersal peaked in July. Dispersing males tended to be heavier than philopatric males; philopatric females were significantly heavier than dispersing females. Expressed as a percentage of all juveniles monitored, annual dispersal ranged from 0% to 79% for males, 0% to 50% for females, and 0% to 52% for all foxes. Percentage of male dispersal was related weakly to mean annual litter size (r2 = 0.27), and percentage of female dispersal was weakly and inversely related to annual indices of small-mammal abundance (r2 = 0.46). Most (65.2%) dispersing juveniles died within ≤10 days of leaving their natal range. Survival tended to be higher for dispersing males than for philopatric males but was similar between dispersing and philopatric females. Sixty percent of all foxes that survived to breeding age reproduced except among dispersing females, none of which reproduced. Alloparental care did not account for sex-biased dispersal in kit foxes. Auxiliary adults were observed occasionally with mated pairs, but helping behavior was not observed. Dispersal patterns of kit foxes may be a function of innate sex-biased dispersal altered by physical and biological pressures.

Assessment of scat‐detection dog surveys to determine kit fox distribution

Abstract Developing sound conservation strategies for carnivores in fragmented landscapes relies on accurate distribution information. Fecal (scat) surveys can provide an effective survey technique, especially when collection of scats is followed by genetic analysis of DNA extracted from scats. Furthermore, use of specially trained detection dogs to locate scats on survey routes may greatly enhance scat recovery. We evaluated utility of scat-detection dog surveys as a method to determine current distribution of kit foxes (Vulpes macrotis mutica). We used a trained dog to locate scats in core and satellite population areas with various densities and different habitat conditions. We compared number of scats found per kilometer on transects along different road and vegetation types. Scat-detection dog surveys detected the presence of kit foxes in each population area searched, regardless of relative fox density and vegetation type. We found a greater number of scats on unpaved than paved roads, suggesting unpaved roads are more appropriate for monitoring of foxes. Additionally, we found a greater number of scats in saltbush (Atriplex polycarpa) scrub than in non-native grassland. This result was strongly influenced by latitude, and was probably related to a north–south precipitation gradient. Our results demonstrate that scat-detection dog surveys can provide an effective conservation tool to map current kit fox distribution. This survey method has a wide application to other carnivore species, and can be used to survey multiple species simultaneously.

Stable isotopes evaluate exploitation of anthropogenic foods by the endangered San Joaquin kit fox (Vulpes macrotis mutica)

Abstract The unprecedented rate of urbanization over the past several decades is a major concern for conservation globally and has given rise to the multidisciplinary field of urban ecology. This field explores the direct and indirect effects of human activities on food-web dynamics, community structure, and animal behavior in highly modified urban ecosystems. Urban ecosystems are typically characterized by reduced species diversity but increased abundance of a few species able to exploit anthropogenic food sources. For many urban mammalian and avian species direct resource subsidization is difficult to assess using traditional means such as scat analysis. Here we show how stable isotope analysis can be used to assess the exploitation of anthropogenic foods in an endangered carnivore, the San Joaquin kit fox (Vulpes macrotis mutica) inhabiting the southern San Joaquin Valley in California. Examination of carbon (δ13C) and nitrogen (δ15N) isotope data shows that kit foxes living in urban Bakersfield, California, extensively exploit anthropogenic foods, which sharply contrasts with dietary data derived from scat analysis. Urban kit foxes had significantly higher δ13C and lower δ15N values than foxes from adjacent nonurban areas and had similar isotope values as Bakersfield human residents, which suggests a shared food source. In contrast, examination of isotopic data for nonurban kit foxes shows that they largely consume the most abundant natural prey species found in their scats. Stable isotope analysis offers a rapid and cost-effective means of evaluating the degree to which urban wildlife populations exploit anthropogenic foods in areas where native C4 vegetation is relatively uncommon or absent, important in assessing the direct impacts of human activities on food-web dynamics in urban ecosystems. We anticipate that the isotopic gradients used here will be useful in assessing the exploitation of anthropogenic foods in other urban wildlife populations.

Condition of San Joaquin kit foxes in urban and exurban habitats

We compared condition of endangered San Joaquin kit foxes (Vulpes macrotis mutica) between an urban population in Bakersfield, California (BAK), and a nearby exurban population at the Naval Petroleum Reserves in California (NPRC). Our objective was to determine whether differences between urban and exurban environments, particularly food availability and disease vectors, were reflected in kit fox condition. Body mass, blood chemistry, and prevalence of viral antibodies were assessed at both sites in 1988 and 1989. Body mass was higher for BAK kit foxes, particularly juveniles, and varied between years for NPRC kit foxes. Higher red blood cell count (RBC), hemoglobin (Hb), hematocrit (Hct), mean corpuscular hemoglobin (MCH), and mean corpuscular volume (MCV) among NPRC kit foxes were indicative of hemoconcentration, probably resulting from dehydration associated with low food or water intake. Kit foxes from NPRC exhibited higher blood urea nitrogen (BUN) and lower cholesterol (CHOL) levels compared to BAK kit foxes. These results may have reflected dietary differences, but they possibly indicated tissue catabolism by NPRC kit foxes due to nutritional deprivation. Other serological data also suggested nutritional stress among NPRC kit foxes. Prevalence of antibodies to canine parvovirus (CPV), canine distemper (CD), and infectious canine hepatitus (ICH) was similar between populations. Food availability for kit foxes at NPRC was relatively low during 1988-89 due to drought conditions, but food probably was not a limiting factor at BAK due to abundant water and the presence of anthropogenic foods. Urban environments may provide certain advantages for San Joaquin kit foxes and could contribute to conservation and recovery efforts.

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.

Effects of radiocollars on San Joaquin kit foxes

Effects of radiocollars on San Joaquin kit foxes (Vulpes macrotis mutica; Mecure et al. 1993) at the Naval Petroleum Reserves, California were assessed by comparing survival, body mass changes, and reproductive indices between uncollared and collared foxes, and between foxes wearing 100-110 and 50-60-g collars. Among adults, higher survival for foxes surviving the first 30 days post-collaring (P = 0.07) and higher mass loss among newly collared foxes (P = 0.02) may have been attributable to a post-collaring acclimation period. The increased survival after 30 days only was evident among foxes with 100-110-g collars. Lower survival and higher mass loss among newly collared juvenile foxes also provided evidence of an acclimation period. Effects among juveniles were particularly evident after parental care presumably had ceased and when many juveniles may have been dispersing. Tests of collar:body mass ratios indicated that juvenile survival was lower at ratios ≥6%. Finally, analyses revealed little evidence of sex-specific collar effects and no evidence of reduced reproductive success among collared adult females. The potential for a post-collaring acclimation period should be considered in investigations of kit fox survival and body mass dynamics, and collaring should be avoided during periods of increased vulnerability or stress.

Germination Rates of Tree Seeds Ingested by Coyotes and Raccoons

Abstract The effect of ingestion by coyotes (Canis latrans) and raccoons (Procyon lotor) on seed germination was investigated for four tree species in Illinois. The germination rate of persimmon (Diospyros virginiana) seeds ingested by raccoons was significantly higher than the rate for uningested seeds. Both were significantly higher than the rate for coyote-ingested seeds. Among coyote-ingested seeds, germination rates of persimmon were significantly higher when seeds were protected by undigested fruit pulp or intact seed sheaths thus reducing the exposure of seeds to gastrointestinal enzymes. American plum (Prunus americana) seeds ingested by coyotes had a significantly lower germination rate compared to uningested seeds, whereas germination of pawpaw (Asimina triloba) seeds was similar between coyote-ingested and uningested seeds. Germination was significantly lower for hackberry (Celtis occidentalis) seeds ingested by raccoons compared to uningested seeds. Ingestion improved germination only for persimmon seeds consumed by raccoons, but tree species may realize other benefits from dispersal by coyotes and raccoons (e.g., decreased parental competition).