Kit Fox Research Articles

Why and how to combine evidence in environmental assessments: Weighing evidence and building cases

All types of environmental decisions benefit from assessments that assemble and analyze diverse evidence. The diversity of that evidence creates complexities that can be managed using an explicit, well-designed process. We suggest two adaptations from the legal lexicon, weight of evidence and building a case. When weighing evidence, weights are assigned to each piece of evidence, and then the body of evidence is weighed in favor of each hypothesis by amassing the weights. Finally, the total weights of evidence for the alternative hypotheses are compared to determine which alternative has the preponderance of evidence in its favor. When building a case, pieces of evidence are organized to show relationships among multiple hypotheses or complex interactions among agents, events, or processes. We provide processes for weighing evidence and building a case and illustrate both approaches in a case study involving the decline of a kit fox population. The general approach presented here is flexible, transparent, and defensible. During its development, it has been applied to risk assessments for contaminated sites and to causal assessments in aquatic and terrestrial systems. It is intended to balance the need for rigor and discipline with the need for sufficient flexibility to accept all relevant evidence and generate creative solutions to difficult environmental problems.

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, Calif...

Basking in the moonlight? Effect of illumination on capture success of the endangered giant kangaroo rat

Bright moonlight is thought to increase predation risk for nocturnal rodents and consequently reduce their activity levels and capture rates. We examined the effect of moonlight on the foraging activity and capture success of the federally endangered giant kangaroo rat (Dipodomys ingens) in the Carrizo Plain National Monument, California. D. ingens is adapted to open grasslands, a habitat type where moonlight should strongly influence its visibility to predators. Using a trapping data set of 11,353 captures from 2007 to 2009 and accounting for factors such as cloud cover, temperature, abundance of the San Joaquin kit fox (Vulpes macrotis mutica), plant biomass, trap acclimation, and trap effort, we found a consistently positive effect of moonlight on capture success. In foraging trials we detected no effect of moonlight on giving-up densities or time spent at seed piles. Our results suggest that giant kangaroo rats do not perceive a higher risk of predation in bright moonlight. Nocturnal rodents that rely on early visual detection of predators might benefit from moonlight as much as their predators do, thus resulting in no net change in predation risk.

Changes in Kit Fox Defecation Patterns During the Reproductive Season: Implications for Noninvasive Surveys

Abstract: Noninvasive survey methods based on analyzing DNA extracted from feces can be useful for carnivores that are difficult to study by other methods. Changes in fecal deposition patterns associated with reproduction in kit foxes (Vulpes macrotis) might affect results of such surveys. We used a trained dog to collect fresh scats on 2‐km transects in the home ranges of 11 radiocollared female kit foxes in January, February, and March 2008 and determined sex of the individual that deposited the scats by amplifying the zinc finger protein gene. Female foxes give birth in mid‐February to mid‐March. We found a similar number of scats each month. In January, the sex ratio of the scats was not different from the expected 1:1. However, in February there were almost 2 male scats for every female scat and in March there were >8 male scats for every female scat. Comparing March to January, there were more male scats on all 11 transects and fewer female scats on 10 of 11 transects. Around the time pups are born, both sexes appear to show changes in fecal deposition patterns that make it easier to find male scats and harder to find female scats. Effects of these changes on survey results will vary depending on the purpose and design of the survey. Surveys to determine distribution and relative abundance would probably not be negatively affected by these changes. However, if surveys to estimate abundance are conducted during the reproductive season, they could result in an underestimate of population size unless the increased heterogeneity in scat detectability is taken into account.

Changes in Kit Fox Defecation Patterns During the Reproductive Season: Implications for Noninvasive Surveys

Changes in Kit Fox Defecation Patterns During the Reproductive Season: Implications for Noninvasive Surveys

An efficient noninvasive method for discriminating among faeces of sympatric North American canids

Molecular technology can identify species noninvasively from faeces found in the field. We describe a fast and reliable genetic method that differentiates faeces of five potentially sympatric North American canids without using multiple primer sets or restriction enzyme digestion. Our primer set amplifies a short fragment (237–288 bp) of the mitochondrial d-loop that is a different length in each species: kit fox (Vulpes macrotis), red fox (Vulpes vulpes), gray fox (Urocyon cinereoargenteus), coyote (Canis latrans), and dog (Canis familiaris). We extensively tested our technique using published and novel d-loop sequences and then applied it to two large faecal data sets collected in California and Virginia. It provides an efficient tool for noninvasively distinguishing sympatric canids in diverse regions of North America.

A new Lagrangian particle model for the simulation of dense gas dispersion

A Lagrangian stochastic model (MicroSpray), able to simulate the airborne dispersion in complex terrain and in presence of obstacles, was modified to simulate the dispersion of dense gas clouds. This is accomplished by taking into account the following processes: negative buoyancy, gravity spreading and the particle's reflection at the bottom computational boundary. Elevated and ground level sources, continuous and instantaneous emissions, time varying sources, plumes with initial momentum (horizontal, vertical or oblique in any direction), plumes without initial momentum are considered. MicroSpray is part of the model system MSS, which also includes the diagnostic MicroSwift model for the reconstruction of the 3-D wind field in presence of obstacles and orography. To evaluate the MSS ability to simulate the dispersion of heavy gases, its simulation performances are compared in detail to two field experiments (Thorney Island and Kit Fox) and to a chlorine railway accident (Macdona). Then, a comprehensive analysis considering several experiments of the Modelers Data Archive is presented. The statistical analysis on the overall available data reveals that the performance of the new MicroSpray version for dense gas releases is generally reliable. For instance, the agreement between concentration predictions and observations is within a factor of two in the 72% up to 99% of the occurrences for the case studies considered. The values of other performance measures, such as correlation coefficient, geometric mean bias and geometric variance, mostly set in the ranges indicated as good-model performances in the specialized literature.

Effects of Roads on Endangered San Joaquin Kit Foxes

ABSTRACT 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.

Social Interactions among San Joaquin Kit Foxes Before, During, and After the Mating Season

Direct observations of small foxes are rare because of their secretive nature and nocturnal activity patterns. We observed 10 adult (� 1-year-old) San Joaquin kit foxes (Vulpes macrotis mutica) at night over a 7-month period that included the mating season to quantify the types, rates, and durations of social interactions. Of 191 interactions between members of this seasonally breeding, socially monogamous species, 52 were with adult foxes in the same social group, 43 with adult foxes from other known social groups, 48 with juveniles (,1 year old), and 48 with unknown foxes. Most interactions (n ¼ 173), especially those between pair-mates, between females, and with juveniles, were affiliative. Agonistic encounters were rare (n ¼ 18) and occurred mostly between males of different social groups and with unknown foxes. Interaction rates with social group members, most of which were pair-mates (88%), peaked in the months before the annual mating season, whereas those with non‐social group foxes, most of which represented potential extrapair copulation partners (79%), peaked later and more sharply. The duration of interactions with adult social and non‐social group foxes was highest during the mating season. Increased social interactions at this time may help foxes strengthen bonds with pair-mates and become familiar with potential extrapair partners.

CFD and Gaussian atmospheric dispersion models: A comparison for leak from carbon dioxide transportation and storage facilities

Carbon Capture and Storage (CCS) is of interest to the scientific community as a way of achieving significant global reduction of atmospheric CO 2 emission in the medium term. CO 2 would be transported from large emission points (e.g. coal fired power plants) to storage sites by surface/shallow high pressure pipelines. Modelling of CO 2 atmospheric dispersion after leakages from transportation facilities will be required before starting large scale CCS projects. This paper deals with the evaluation of the atmospheric dispersion CFD tool Fluidyn-PANACHE against Prairie Grass and Kit Fox field experiments. A description of the models for turbulence generation and dissipation used ( k– ɛ and k– l) and a comparison with the Gaussian model ALOHA for both field experiments are also outlined. The main outcome of this work puts PANACHE among the “fit-for-purpose” models, respecting all the prerequisites stated by Hanna et al. [Hanna, S.R., Chang, J.C. and Strimaitis, D.G., 1993. Hazardous gas model evaluation with field observations. Atmospheric Environment, 27, 2265–2285] for the evaluation of atmospheric dispersion model performance. The average under-prediction has been ascribed to the usage of mean wind speed and direction, which is characteristic of all CFD models. The authors suggest a modification of performance ranges for model acceptability measures, within the field of high pressure CO 2 transportation risk assessment, with the aim of accounting for the overall simplification induced by the usage of constant wind speed and direction within CFD atmospheric dispersion models.

Niche Overlap and Resource Partitioning Between Sympatric Kit Foxes and Coyotes in the Great Basin Desert of Western Utah

Successful coexistence of sympatric canid species often relies on the subdominant species' ability to reduce competition through the differential selection of niche space. Information regarding the process of niche selection and its effect on the structure of canid communities in the Great Basin Desert is unavailable. From Dec. 1999 to Aug. 2001, we quantified the spatial, dietary and temporal resource overlap of kit foxes (Vulpes macrotis) and coyotes (Canis latrans) on the U.S. Army Dugway Proving Ground, Utah. Kit foxes and coyotes demonstrated substantial levels of spatial, temporal and dietary overlap. However, where the two species had overlapping home ranges, space use within the home range differed between the two species, with kit foxes using vegetative and landscape ruggedness characteristics not regularly used by coyotes. Although there was little evidence of seasonal change in either canid's use of habitat, in some areas kit foxes made nightly movements to more productive habitats with moderate ruggedness. Regardless of spatial partitioning, incidents of interference competition were high; 56% of known kit fox deaths were attributed to coyotes. In our study, high levels of temporal and dietary overlap, kit fox movement from extreme to moderate topography during foraging and selection for abundant cover demonstrated competitive pressures exerted on the kit fox population by the sympatric coyote population.

Subpopulation Triage: How to Allocate Conservation Effort among Populations

Threatened species often exist in a small number of isolated subpopulations. Given limitations on conservation spending, managers must choose from strategies that range from managing just one subpopulation and risking all other subpopulations to managing all subpopulations equally and poorly, thereby risking the loss of all subpopulations. We took an economic approach to this problem in an effort to discover a simple rule of thumb for optimally allocating conservation effort among subpopulations. This rule was derived by maximizing the expected number of extant subpopulations remaining given n subpopulations are actually managed. We also derived a spatiotemporally optimized strategy through stochastic dynamic programming. The rule of thumb suggested that more subpopulations should be managed if the budget increases or if the cost of reducing local extinction probabilities decreases. The rule performed well against the exact optimal strategy that was the result of the stochastic dynamic program and much better than other simple strategies (e.g., always manage one extant subpopulation or half of the remaining subpopulation). We applied our approach to the allocation of funds in 2 contrasting case studies: reduction of poaching of Sumatran tigers (Panthera tigris sumatrae) and habitat acquisition for San Joaquin kit foxes (Vulpes macrotis mutica). For our estimated annual budget for Sumatran tiger management, the mean time to extinction was about 32 years. For our estimated annual management budget for kit foxes in the San Joaquin Valley, the mean time to extinction was approximately 24 years. Our framework allows managers to deal with the important question of how to allocate scarce conservation resources among subpopulations of any threatened species.

Barking Vocalizations in San Joaquin Kit Foxes (Vulpes macrotis mutica)

Swift foxes (Vulpes velox) and Arctic foxes (Alopex lagopus) often use barking to communicate information to mates, members of social groups, and other conspecifics. Barking by the closely related kit fox (V. macrotis), however, remains largely unobserved and undocumented. We observed barking among a population of radiocollared San Joaquin kit foxes (V. m. mutica) inhabiting Bakersfield, Kern Co., California, during August 2002–March 2003. We observed 150 barks, including 56 from two adult (≥1 year old) males, 83 from an adult female, and 11 from two juveniles (<1 year old). Of these, we recorded nine barks, each of which consisted of a series of short, discrete elements repeated in rapid sequence; similar in structure and sound to barking sequences by swift and Arctic foxes. Barking occurred rarely and concentrated mostly around the mating period in mid-December. Our observations suggest that barking functions to contact or attract mates or potential mates and serves little territorial importance.

Anticoagulant Rodenticide Exposure in an Urban Population of the San Joaquin Kit Fox

Author(s): McMillin, Stella C.; Hosea, Robert C.; Finlayson, Brian F.; Cypher, Brian L.; Mekebri, Abdou | Abstract: Concerned that San Joaquin kit foxes from urban areas may be exposed to commensal anticoagulants, the California Department of Fish and Game, Pesticide Investigations Unit, in conjunction with the Endangered Species Recovery Program’s Urban Kit Fox Project, began monitoring San Joaquin kit foxes from the Bakersfield, CA population. Necropsies were performed and liver tissue samples collected from kit fox carcasses. Livers from archived kit foxes dating back to 1977 were also analyzed. A non-urban population of San Joaquin kit foxes from Lokern was used as a control. Other predators in the area, including coyotes and red foxes, were also analyzed for comparison. Between 1999 and 2007, tissue samples from 45 animals have been analyzed for residues of anticoagulant rodenticides. Anticoagulant compounds identified included brodifacoum, bromadiolone, pival, and chlorophacinone. Twenty-six of the 30 San Joaquin kit foxes from Bakersfield contained at least one anticoagulant, and the most commonly detected anticoagulant was brodifacoum. None of the 12 Lokern San Joaquin kit foxes contained anticoagulants. Other predators followed the same pattern: both red foxes from Bakersfield contained anticoagulant residues, but the coyote taken from Lokern did not.

Social Monogamy in Kit Foxes: Formation, Association, Duration, and Dissolution of Mated Pairs

Social monogamy is characterized by long-term pair-bonds, but there is extensive variation among socially monogamous species in the timing of pair formation, the extent to which pair-mates associate throughout the year, the duration of pair-bonds, and the frequency with which pair-bonds are dissolved while both partners are living. We studied these aspects of social monogamy in kit foxes (Vulpes macrotis) at 1 urban and 2 nonurban sites. Behavior was similar across sites despite differences in ecological conditions. Pair formation occurred throughout the year, often within a month after the loss of a mate. Pair-mates associated throughout the year. Some pairs remained associated for more than 1 breeding season. Death of a pair-mate was the most common reason for the dissolution of a pair (14 of 16 cases). Two pairs dissolved while both partners were still living: 1 due to abandonment by a male of his pair-mate and territory and 1 due to displacement of a male by another male. These characteristics of social monogamy in kit foxes may be related to year-round territoriality, and may optimize individual fitness by enhancing survival and ultimately reproductive success.

Escaping Intraguild Predation: Mexican Kit Foxes Survive While Coyotes and Golden Eagles Kill Canadian Swift Foxes

Although interspecific killing among carnivores can drive populations toward extinction, it is generally unknown how these intraguild interactions vary among populations, and whether the threat for vulnerable species can be mitigated. We studied imperiled populations of swift foxes (Vulpes velox) in Canada and kit foxes (Vulpes macrotis) in Mexico to determine potential differences in survival or predator-avoidance strategies. Survival rates were significantly lower in Canada than in Mexico because of mortality caused by coyotes (Canis latrans) and golden eagles (Aquila chrysaëtos), and the potential for population recovery is likely higher for the Mexican fox population. Differences in body size between coyotes and foxes, diet, group sizes, intraspecific home-range overlap, home-range sizes of coyotes, and movements of coyotes relative to foxes were similar among study areas. However, Canadian foxes had home ranges that were approximately 3 times larger than those in Mexico, and Canadian foxes were most frequently killed on their home-range peripheries. Home ranges of kit foxes decreased in size as the availability of black-tailed prairie dog (Cynomys ludovicianus) colonies increased and associated refuge holes, which foxes could use to escape predation, were significantly more abundant in Mexico than in Canada. Small home ranges of foxes probably reduced encounters with coyotes in Mexico, and a high availability of refuges likely allowed foxes to elude predators when such encounters did occur. Differences in survival of foxes relative to mortality caused by coyotes demonstrate that interactions between carnivores can -vary greatly between populations and that, in some situations, vulnerable species may be able to coexist with dominant carnivores despite a lack of large-scale habitat partitioning.

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 Heermann's 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.

CHANGES IN KIT FOX–COYOTE–PREY RELATIONSHIPS IN THE GREAT BASIN DESERT, UTAH

Variation in kit fox (Vulpes macrotis) population parameters can be influenced by vegetative cover and the distribution and abundance of other predator and prey species. Dramatic changes to Great Basin Desert habitats, which can potentially impact mammalian species, have occurred in some areas in Utah. We examined kit fox demographics and prey populations from 1999 to 2001 on Dugway Proving Ground (DPG), a U.S. Army facility in Utah, and compared some parameters to historical levels (1956–1958–1966–1969). Adult survival rates were fairly consistent between 1999 and 2000 and between 1999 and 2001; however, survival was greater in 2001 than in 2000. Reproductive rates ranged from 1.0 to 3.8 pups per female in 1999–2000 and were similar to historical numbers (1.0–4.2 pups per female). We found a decrease in pre-whelping kit fox density from the 1960s (0.12 foxes · km−2) to 1999–2001 (0.04 foxes · km−2); however, densities were similar between the current study and the 1950s (0.08 foxes · km−2). Using 9 years of data, we found density dependence between reproductive rates of the current year and annual fox density from the previous year. Using 7 years of data, we found a slight correlation between kit fox annual density and a 1-year lag in leporid abundance, even though leporid abundance was lower during the present study than it was historically. Compared to historical levels, current small mammal abundance and species composition has changed in several habitats. Kit fox breeding density and annual density were inversely correlated with coyote (Canis latrans) density. Changes to the landscape at DPG, especially due to invasion of cheatgrass (Bromus tectorum) and addition of artificial water sources, have caused a change in available kit fox habitat and prey species, and have increased the abundance of coyotes, the kit fox's major competitor.

USE OF AGRICULTURAL LANDS BY SAN JOAQUIN KIT FOXES

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.

Documenting noise exposures for wildlife studies: Review of large studies over the past 18 years

A couple of decades ago, researchers recognized the importance of improving understanding of noise exposure to wildlife for bioacoustic studies. Due to the differences in the ecology of species of concern, various approaches took place over these past 20 years to address this issue. The metrics used to determine effects and how the metrics were applied to observed behavioral and physiological responses also varied, based on several factors. This presentation will review methods used on several large projects, including big horn sheep, caribou, kit fox, Mexican spotted owls, peregrine falcons, and red cockaded woodpeckers. This review may help provide the direction for future bioacoustic studies.