Foxes and food subsidies: anthropogenic food use by red and Arctic foxes, and effects on Arctic fox survival, on the Arctic Coastal Plain of Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2013Food subsidies have the potential to impact wildlife on the Arctic Coastal Plain of Alaska. Red foxes (Vulpes vulpes (L., 1758)) expanded their range into Arctic regions during the 20th century, and the availability of anthropogenic foods may have contributed to their success and persistence in the Arctic. Arctic foxes (Vulpes lagopus (L., 1758)) are also known to forage on anthropogenic foods in Prudhoe Bay and to forage on marine mammals on the sea ice, but it is unknown whether these strategies benefit survival of Arctic foxes. This thesis examined: 1) the importance of anthropogenic foods to the diets of red and Arctic foxes in Prudhoe Bay, and 2) the factors with the greatest effect on Arctic fox survival, including access to food subsidies in Prudhoe Bay and on the sea ice. For the first study, stable isotopes of red and Arctic fox tissues were used to infer late summer, late winter, and lifetime (for red fox only) diets. The contribution of anthropogenic foods to the diets of both species was low in late summer (~10%) but high in late winter (49%, 95% credible interval = 38-57%, of red fox diets and 37%, 95% credible interval = 29-44%, of Arctic fox diets). Estimates of lifetime diet in red foxes revealed high levels of anthropogenic food use, similar to the winter diet. To characterize the extent of competition for food resources, dietary niche overlap was examined between both species by comparing isotopic niche space. Both fox species had little isotopic niche overlap but may have greater overlap between their ecological dietary niches. Availability and consumption of anthropogenic foods by red foxes, particularly in winter, may partially explain their year-round presence in Prudhoe Bay. For the second study, nest survival models and satellite collar data were used to evaluate whether multiple factors affected survival of adult and juvenile foxes. Site and sea ice use had two times more support than the other factors. Three groups of foxes were identified based on capture location and sea ice use, which corresponded to different survival rates: Prudhoe Bay foxes, NPR-A foxes that used sea ice during more than eight 2-week periods during the winter (seven 2-week periods for juveniles), and NPR-A foxes that did not use sea ice. Both adult and juvenile foxes at Prudhoe Bay had modestly higher annual survival rates, 0.50 (90% CI 0.31-0.69) and 0.04 (90% CI 0.0-0.08) respectively, than foxes at NPR-A that did not use sea ice, 0.40 (90% CI 0.18-0.62) and 0.01 (90% CI 0.0-0.04) respectively. NPR-A foxes that used sea ice extensively had the highest survival rates. Food subsidies may have far-reaching effects on red and arctic foxes on the Arctic Coastal Plain of Alaska

Rodenticide Exposure Among Endangered Kit Foxes Relative to Habitat Use in an Urban Landscape

Endangered San Joaquin kit foxes (Vulpes macrotis mutica) inhabiting Bakersfield, California exhibit a high incidence of exposure to anticoagulant rodenticides (ARs). We examined kit fox habitat use in an effort to determine potential sources of AR exposure. Kit fox capture, den, night, and mortality locations were assigned to one of 10 habitat categories. Using all available locations, foxes that tested positive for second generation anticoagulant rodenticides (SGARs) were located more frequently on golf courses while those testing negative were located more frequently in commercial areas. Foxes that tested positive for first generation anticoagulant rodenticides (FGARs) were located more frequently in industrial areas while those testing negative were located more frequently on golf courses. Based on night locations (when foxes are foraging), foxes that tested positive for SGARs were found more frequently in undeveloped and golf course habitats. Foxes that tested positive for FGARs were found more frequently in undeveloped, campus, and industrial habitats. Although available data were not sufficient to identify specific point-sources of AR exposure for foxes, golf courses appeared to be used more frequently by foxes exposed to SGARs. However, sources of exposure likely are abundant and widespread in the urban environment. Based on the results of this study, we recommend (1) investigating patterns of AR use in Bakersfield, (2) conducting an outreach program to emphasize the risk from ARs to kit foxes and other wildlife, and (3) continuing to monitor the incidence and patterns of AR exposure among kit foxes in Bakersfield

Breeding den selection by Arctic foxes (Vulpes lagopus) in southern Yamal Peninsula, Russia

Selecting the right location for a den during the breeding season is a type of habitat selection in the Arctic fox (Vulpes lagopus) that is likely to affect its reproductive success. A den’s suitability likely depends on its ability to provide shelter, as well as its proximity to prey resources. Depending on the different relative risks that Arctic foxes may face across their broad circumpolar range, Arctic foxes may place different emphases on selection for shelter and prey resources in different ecosystems. Understanding the different requirements for reproduction under different ecological conditions is highly relevant to conservation efforts in areas where Arctic foxes are threatened by rapid environmental changes. Here, we investigated the relative selection for shelter and prey resources in southern Yamal Peninsula (Russia) using data from 45 dens collected over a 13-year period. Arctic foxes preferred to breed in dens with more den entrances; an indicator of shelter quality. Arctic foxes also preferred dens surrounded by more prey resources (quantified by the amount of river valley habitat), but this result was less conclusive. These results complement the findings reported from other study areas, illustrating that Arctic foxes in ecosystems with diverse predator communities may put emphasis on selection for shelter quality. In less productive ecosystems, Arctic foxes may rather put emphasis on selection for prey resources. As tundra ecosystems become more productive and generalist predators move north, the reproductive requirements and habitat selection of Arctic foxes may change accordingly, depending on the species’ ability to adapt

Island Fox Spatial Ecology and Implications for Management of Disease

Disease, predation, and genetic isolation resulted in 4 of 6 island fox (Urocyon littoralis) subspecies being listed as endangered in 2004. Potential for disease outbreaks continues to pose a major threat to the persistence of these isolated, endemic populations. We examined how roads influence the spatial ecology of San Clemente Island foxes (U. l. clementae), particularly in regard to spread of disease, to provide management recommendations for preventing or minimizing a disease outbreak on San Clemente Island, California, USA. Home range areas (x=0.75 km2) and core areas (x=0.19 km2) of foxes on San Clemente Island were 0.36–1.23 and 2.17 times larger, respectively, than estimates from Santa Cruz Island foxes (U. l. santacruzae). Home ranges and core areas were 78% larger and 73% larger, respectively, for foxes near roads than for foxes away from roads. Home ranges were also largest when foxes were not caring for offspring (i.e., seasons of pup-independence and breeding). We did not detect any dispersal movements, but foxes living near roads moved 33% farther in 2-hour periods than foxes not living near roads. Foxes near roads move faster, range more widely, and could more rapidly spread a pathogen throughout the island; therefore, roads might serve as transmission corridors.We recommend reducing this risk by increasing widths of vaccination firewalls (areas where vaccination is used to induce a disease-resistant or immune population of foxes), ensuring these areas deliberately intersect roads, and vaccinating a higher proportion of foxes living near roads. Disease risk models incorporating these strategies could inform the lowest risk scenarios

Do Urban Red Foxes Attack People? An Exploratory Study and Review of Incidents in Britain

Human–wildlife interactions are believed to be increasing worldwide, and a number of studies have analyzed the risks posed by larger carnivores. However, people can also perceive smaller species of carnivores as threatening, particularly in urban areas. Red foxes (Vulpes vulpes) started to colonize British cities in the 1930s, and there is growing public concern about foxes biting people, particularly babies. These events are generally described in the press as attacks and generate intense media coverage and speculation that foxes view human infants as potential prey. Because foxes rely primarily on auditory cues for hunting, we conducted acoustic playback experiments in the gardens of 15 residential houses in northwest Bristol, United Kingdom, in December 2015 and 11 gardens from May to June 2016 to determine whether urban foxes were attracted to infant distress calls (cries). Foxes were not more likely to be attracted to infant cries or laughs than silence, although a minority of foxes cautiously approached and contacted the source of both types of infant vocalization. Their behavior appeared to be investigative rather than aggressive or predatory. Our review of the incidents reported in the British media showed that most people were bitten or scratched while sleeping, and adults were more likely to be bitten than children. The nature of the interactions and the wounds inflicted suggest that the foxes were using their mouth or forefeet to investigate an unusual object. Most incidents occurred inside people’s homes, even though it is unusual for foxes to enter houses. The data suggested that incidents where people were bitten were chance events, possibly involving a particularly bold fox. To minimize the risk to the public, more quantitative data are required on the age, social status, and health of the foxes that enter houses and those that bite people

Long-term fluctuations in an arctic fox (Vulpes lagopus) population: a matter of diet?

The long-term dynamics of predator populations may be driven by fluctuations in resource availability and reflect ecosystem changes in response to climate change. The Icelandic arctic fox population has known major fluctuations in size since the 1950s, starting with a decreasing period until late 1970s, followed by a six-fold increase until 2008 when the population dropped to half its size within five years until it recently bounced back again. Using stable isotope analysis of bone collagen over a long-time series (1979-2018), I aimed at identifying the main resources used by Icelandic arctic foxes during periods of growth and decline to assess if the recent variations in their population size are linked to fluctuations in the availability of resources. Building on the results of Carbonell Ellgutter & al. (2020), I hypothesized that the decline in seabirds abundance was responsible for the decrease in the fox population. Additionally, I expected that the preceding growth period led to increased competition among foxes, causing a rise in inter-individual variations in their diet, ultimately leading to variations in their isotopic niches at the population scale. The isotopic signatures of arctic foxes differed drastically between their habitats, as well as trends in δ13C and δ15N ratios over time. Inland foxes showed an overall shift towards more terrestrial preys, whereas coastal foxes displayed a relatively stable use of marine resources over the years. Stable isotopes mixing models suggested that marine resources and rock ptarmigans were the most important food sources, and highlighted a rather stable diet in coastal habitats compared to inland habitats where more fluctuations in dietary composition were observed. Isotopic niche breadths showed broader niches for coastal foxes than inland foxes, and also highlighted more variations in inland habitats where foxes seemed to diversify their diet during periods of growth, when their preferred prey became scarce and when the number of conspecifics increased. On the other hand, coastal foxes had a constant niche breadth throughout the study period and seemed to adopt a more generalist behavior. Fluctuations in the Icelandic arctic foxes population occurred without major changes in their dietary composition despite the variations in the abundance of their main resources

Urban foxes are bolder but not more innovative than their rural conspecifics

Urbanization is the fastest form of landscape transformation on the planet, but researchers' understanding of the relationships between urbanization and animal behaviour is still in its infancy. In terms of foraging, bold and innovative behaviours are proposed to help urban animals access, utilize and exploit novel anthropogenic food sources. Red foxes, Vulpes vulpes, are one of the most widespread carnivores on the planet. However, despite frequent stories, images and videos portraying them as ‘pests’ in urban areas due to their exploitation of food-related objects (e.g. raiding the contents of outdoor bins), it is unknown whether they are bolder and more innovative in terms of their likelihood of exploiting these resources compared to rural populations. In the current study, we gave novel food-related objects to foxes from 104 locations (one object per location) across a large urban-rural gradient. To access the food, foxes had to use behaviours necessary for exploiting many food-related objects in the real world (e.g. biting, pushing, pulling or lifting human-made materials). Despite foxes from 96 locations acknowledging the objects, foxes from 31 locations touched them, while foxes from 12 locations gained access to the food inside. A principal component analysis of urban and other landscape variables (e.g. road, greenspace and human population density) revealed that urbanization was significantly and positively related to the likelihood of foxes touching, but not exploiting, the objects. Thus, while urban foxes may be bolder than rural populations in terms of their willingness to physically touch novel food-related objects, our findings are inconsistent with the notion that they are more innovative and pose a general nuisance to people by regularly exploiting these anthropogenic resources on a large geographical scale

Dirofilaria immitis in the Wild Canids of Illinois

The heartworm, Dirofilaria immitis, is widespread in dogs in North America and has been reported in wild canids in many states. This is a report of this parasite in hearts removed from coyote, red fox and gray fox carcasses collected in Illinois. A total of 415 coyotes had a significantly higher infection rate (23.6%) than 225 red foxes (3.6%) and 99 gray foxes (3.0%). Infection rates in red foxes and coyotes were significantly higher in or near the Wabash Border Natural Division along the eastern side of the state, suggesting a relationship between infection rates and this region. The mean number of worms in coyotes (8.1), red foxes (6.8) and gray foxes (1.3) did not differ significantly. Coyotes supported a maximum of 52 worms; red foxes, 21 worms; and gray foxes, 2 worms. An exponential decrease in the number of infected coyotes was noted as worm loads increased; 56.5% of 85 infections consisted of one to four worms, while only 16.5% of the infections had 15 or more worms. The percentage of the coyote sample with the potential to provide microfilariae to vectors (13.1%), based on the presence of both male and female worms, was significantly greater than the same parameter for both red foxes (1.3%) and gray foxes (1.0%)

Winter activity of bat-eared foxes Otocyon megalotis on the Cape West coast

Diurnal activity budgets of bat-eared foxes Otocyon megalotis in winter (June) at the Postberg Nature Reserve, West Coast National Park, were analysed to determine the influence of environmental factors on their activity. Abiotic factors such as effective temperature, wind speed, cloud cover and rainfall have an effect on prey availability and thermoregulation of the foxes and therefore affect their activity rhythm. Low effective temperature and high wind speed result in more resting and less foraging by foxes. The reverse applies at high effective temperature and low wind speed. No foraging occurred during rain, and only for short periods when the sun shone on overcast days. With the start of pair formation in June–July allogrooming, which was not influenced by abiotic factors, increased. Foxes resumed activity from the same resting sites each day