Seasonal food habits of corsac and red foxes in Mongolia and the potential for competition

Competition often occurs between sympatric species that exploit similar ecological niches. Among canids, competition may be reduced by partitioning resources such as food, time, and habitat, but the mechanisms of coexistence remain poorly understood, particularly among fox species. We described the food habits of two foxes that live sympatrically across northern and central Asia, the corsac fox (Vulpes corsac) and red fox (V. vulpes), by analyzing scats collected during a field study in Mongolia. We analyzed 829 corsac and 995 red fox scats collected from April 2005 to August 2007 and tested the extent to which food partitioning occurred. The diets of both species consisted mainly of insects followed by rodents, but also included birds, reptiles, large mammal remains (carrion), plant material (including fruits and seeds), and garbage. Despite high overlap in the proportion of food items consumed, differences existed between species in overall diet with corsacs more frequently consuming beetles, but proportionally fewer crickets and large mammal remains than red foxes. We detected interspecific differences during the pup rearing and dispersal seasons, when prey was abundant, but not during the breeding season, when prey was scarce and diet overlap highest. Each species’ diet also differed seasonally and exhibited moderate overall breadth. Corsacs consumed proportionally more beetles and rodents during pup rearing and crickets during dispersal relative to other seasons, whereas red foxes consumed proportionally more crickets during pup rearing and dispersal and more rodents and large mammals during pup rearing and breeding relative to other seasons. Our results suggest that partitioning of food resources during most of the year facilitates coexistence, and that the potential for competition is highest during winter months.     

Survival and Cause-Specific Mortality of Red Foxes in Agricultural and Urban Areas of Illinois

Abstract: Range expansion and population increase by coyotes (Canis latrans), reduced hunting and trapping, and intensified agricultural practices in the Midwest have altered red fox (Vulpes vulpes) mortality, although relative impacts of these factors are unknown. We examined mortality causes and survival of red foxes in urban and rural agricultural areas of Illinois, using radio telemetry data from 335 foxes (Nov 1996 to May 2002). We used Akaike's Information Criterion to evaluate six survival models for foxes reflecting 1) environmental effects, 2) intrinsic effects, 3) temporal effects, 4) behavioral effects, 5) social effects, and 6) a global model. Environmental and intrinsic models of survival were optimal for adult foxes. Adult foxes with low (0-20%) and high (80-100%) percentages of row crops in their home ranges had higher survival than adults with moderate percentages (40-70%). Heavier adults at capture also survived better. A global model (all covariates) was optimal for juvenile foxes. Higher juvenile survival associated with larger litters, lower body fat, and reduced dispersal time. Yearly survival ranged from 0.18 for rural male juveniles to 0.44 for rural female adults. Adult survival rates (0.35) were 11% higher than juvenile survival rates (0.24). Yearly survival varied for urban foxes due to cyclic outbreaks of sarcoptic mange (Sarcoptes scabei). Thus, summer survival (May-Sep) of urban juveniles ranged from 0.10 (mange present) to 0.83 (no mange recorded). Mange was the most common (45% of all fatalities) source of mortality for urban foxes, followed by road kill (31%). We recorded only 4 mange fatalities (2%) for rural foxes. Rural foxes experienced low hunting mortality (7%) and equivalent road kill and coyote predation fatalities (40% each). Sources of mortality for midwestern foxes have dramatically changed since the 1970s when hunting was the major cause of mortality. Coyote predation has effectively replaced hunting mortality, and cyclic patterns of mange outbreaks in urban fox populations might indicate a dynamic source or sink relationship to surrounding rural fox populations. Absent mange, urban areas might provide refugia for red foxes where coyote populations persist at high densities in rural areas. Managers of sympatric urban and rural wildlife populations must understand survival dynamics influencing the population at the landscape level.     

Red fox trap success is correlated with piping plover chick survival

Predation management is an important component of managing species of conservation concern. The piping plover (Charadrius melodus; plover), a disturbance-dependent and conservation-reliant shorebird that nests on sandy beaches and barrier islands on the Atlantic Coast, was listed under the United States Endangered Species Act in 1986, with habitat loss and predation stated as key causes of its decline. We evaluated the relationship between a suite of predators and plover chick survival from 2015–2018. We used a camera grid to establish indices of the abundance of 3 known chick predators: red fox (Vulpes vulpes), raccoon (Procyon lotor), and domestic cat. We used camera detections in a survival model to assess potential relationships between predator species detection and plover chick survival. Plover chick survival was negatively related with red fox detection, but not with detection of the other 2 predators. In addition to the correlation with red fox detections, chick survival was negatively related to high plover nesting density. Our results suggest that red foxes were predators of piping plover chicks during our study, likely augmented by other density-dependent sources of mortality. Targeted predator management could aid in conservation of piping plovers in this system as a short-term solution, but long-term recovery plans must also address habitat limitation.     

Effect of fox hunting with small hound packs on spatial behaviour of brown hares

Control of red fox Vulpes vulpes populations is a fundamental game management tool used by hunters interested in increasing prey populations. In Italy, a popular method to control fox populations is hunting with small hound packs. The effects of this hunting technique on non-target species such as the brown hare Lepus europaeus, are unknown. In this study, we analysed for the first time the effects of fox hunting with hound packs on brown hares tagged with VHF collars. Our results showed that hunting with four trained hounds did not significantly modify the spatial behaviour of the brown hare.     

Snow tracking reveals different foraging patterns of red foxes and pine martens

Red fox (Vulpes vulpes) shares similar prey preferences and co-occurs with several other carnivores, and is together with pine marten (Martes martes), the most common mesocarnivore in the northern boreal forest. Voles are important prey for both species, but it is unclear to what extent they compete for the same food resources in winter. Here, we use 2139 km and 533 km of meticulous snow tracking of red foxes and pine martens to evaluate their food niches. We measured hunting and digging behaviour, whether successful or not, and the effect of snow depth and temperature. Pine martens were restricted to forested habitats, whereas red foxes used a wide range of habitats. Red foxes were found to dig more often than pine martens, 0.67 vs. 0.39 digging events per kilometre. Hunting was less common and similar in both species, about 0.1 hunting event per kilometre. Pine martens were more efficient in hunting and finding food remains compared to red foxes. Increasing snow depth reduced hunting success and also reduced dig success of red foxes. Food niche overlap was small. Red foxes used mostly voles and carrion remains of ungulates, whereas pine martens used cached eggs and small birds. We suggest that caching eggs is an important strategy for pine martens to survive winter in northern latitudes. Snow depth was important for capturing voles, and thick snow cover appeared to mask the effect of vole peaks. Intensified land use, as clear-cutting and leaving slaughter remains from harvest, will benefit red foxes on the expense of pine martens. The ongoing climate change with warmer winters and less snow will likely further benefit the red fox.     

Predation processes: behavioural interactions between red fox and roe deer during the fawning season

Predation by red fox (Vulpes vulpes) is the most important mortality cause for neonatal roe deer (Capreolus capreolus) in Scandinavia. With the objective of investigating how the fox finds fawns and how antipredatory behaviour of roe deer females influences choice of hunting method, I analysed observations of interactions between red fox and roe deer females. The observations were collected over 14 years in a mixed forest/agricultural landscape in Sweden. Of 49 fox–doe encounters, the doe attacked the fox in 59%. In 90% of these attacks the fox was successfully deterred. In two observations a doe saved a fawn attacked by a fox. Two hunting methods used by the fox were discerned. In 28 cases foxes searched the ground, and in 18 cases they surveyed open areas, often from a forest edge. The latter behaviour seemed more directed at fawns and was seen leading to a capture attempt. Searching seemed less efficient and also difficult to conduct due to the aggressiveness of does. A surveying sit-and-wait type of hunting method thus appeared as the most successful. The possibility to use this method could explain why roe deer fawns are more vulnerable to fox predation in open habitats.     

Inter- and intraspecific competition between the fox species Alopex lagopus and Vulpes vulpes: an evaluation trial under penned conditions

This study compared competition capacity and dominance relations between arctic foxes (Alopex lagopus) and red foxes (Vulpes vulpes). Experiments were carried out in semi-natural earthen floor enclosures using farm-bred colour types of both species (blue fox and silver fox) as subjects. Results of the dominance scoring and open field behaviour after weaning in August-September showed that blue foxes dominated over silver foxes. Thereafter, the situation gradually became reversed and silver foxes were dominant during the breeding and whelping seasons. Housing both species together from weaning produced more curious animals as compared to when these species were placed in common quarters after the autumn equinox. In the case of blue foxes, the male dominated highly over all females. In silver foxes, the difference in dominance between the sexes was, however, less pronounced. The most dominant individuals in the study groups were typically among the heaviest. Breedings and whelpings succeeded better in silver than in blue foxes. However, none of litters born survived more than one week. The present results support the conclusion that when both fox species are housed together, Vulpus vulpus tends to dominate over Alopex lagopus. Received: 22 March 1996/Accepted: 30 June 1996     

Population structure of two rabies hosts relative to the known distribution of rabies virus variants in Alaska

For pathogens that infect multiple species, the distinction between reservoir hosts and spillover hosts is often difficult. In Alaska, three variants of the arctic rabies virus exist with distinct spatial distributions. We tested the hypothesis that rabies virus variant distribution corresponds to the population structure of the primary rabies hosts in Alaska, arctic foxes (Vulpes lagopus) and red foxes (Vulpes vulpes) to possibly distinguish reservoir and spillover hosts. We used mitochondrial DNA (mtDNA) sequence and nine microsatellites to assess population structure in those two species. mtDNA structure did not correspond to rabies virus variant structure in either species. Microsatellite analyses gave varying results. Bayesian clustering found two groups of arctic foxes in the coastal tundra region, but for red foxes it identified tundra and boreal types. Spatial Bayesian clustering and spatial principal components analysis identified 3 and 4 groups of arctic foxes, respectively, closely matching the distribution of rabies virus variants in the state. Red foxes, conversely, showed eight clusters comprising two regions (boreal and tundra) with much admixture. These results run contrary to previous beliefs that arctic fox show no fine‐scale spatial population structure. While we cannot rule out that the red fox is part of the maintenance host community for rabies in Alaska, the distribution of virus variants appears to be driven primarily by the arctic fox. Therefore, we show that host population genetics can be utilized to distinguish between maintenance and spillover hosts when used in conjunction with other approaches.     

Arctic fox versus red fox in the warming Arctic: four decades of den surveys in north Yukon

During the last century, the red fox (Vulpes vulpes) has expanded its distribution into the Arctic, where it competes with the arctic fox (Vulpes lagopus), an ecologically similar tundra predator. The red fox expansion correlates with climate warming, and the ultimate determinant of the outcome of the competition between the two species is hypothesized to be climate. We conducted aerial and ground fox den surveys in the northern Yukon (Herschel Island and the coastal mainland) to investigate the relative abundance of red and arctic foxes over the last four decades. This region has undergone the most intense warming observed in North America, and we hypothesized that this climate change led to increasing dominance of red fox over arctic fox. Results of recent surveys fall within the range of previous ones, indicating little change in the relative abundance of the two species. North Yukon fox dens are mostly occupied by arctic fox, with active red fox dens occurring sympatrically. While vegetation changes have been reported, there is no indication that secondary productivity and food abundance for foxes have increased. Our study shows that in the western Arctic of North America, where climate warming was intense, the competitive balance between red and arctic foxes changed little in 40?years. Our results challenge the hypotheses linking climate to red fox expansion, and we discuss how climate warming’s negative effects on predators may be overriding positive effects of milder temperatures and longer growing seasons.     

The high level of nutritional niche overlap between red fox (<Emphasis Type="Italic">Vulpes vulpes</Emphasis>) and sympatric golden jackal (<Emphasis Type="Italic">Canis aureus</Emphasis>) affects the body weight of juvenile foxes

In the period of August 2013 to September 2015, we collected and measured the body weight of 246 red fox (Vulpes vulpes) carcasses collected during hunts. A portion of these red foxes (n = 153) was originally from habitats they shared with the golden jackal (Canis aureus), while the other portion (n = 93) had almost no contact with this species. We analyzed the body weight of red foxes from both areas according to age (adult-cub) as well as gender. We have found that the younger animals that live sympatrically with the golden jackal weigh less than those from the golden jackal-free territory regardless of gender. In the case of adult red foxes, the habitat-related differences between body weight were found to be insignificant. These results suggest that the high level of nutritional niche overlap between sympatric red fox and golden jackal could affect the body weight of juvenile red foxes.     

Natal den selection by sympatric arctic and red foxes on Herschel Island,Yukon, Canada

In the twentieth century, red fox (Vulpes vulpes) expanded into the Canadian Arctic, where it competes with arctic fox (Vulpes lagopus) for food and shelter. Red fox dominates in physical interactions with the smaller arctic fox, but little is known about competition between them on the tundra. On Hershel Island, north Yukon, where these foxes are sympatric, we focused on natal den choice, a critical aspect of habitat selection. We tested the hypothesis that red fox displaces arctic fox from dens in prey-rich habitats. We applied an approach based on model comparisons to analyse a 10-year data set and identify factors important to den selection. Red fox selected dens in habitats that were more prey-rich in spring. When red foxes reproduced, arctic fox selected dens with good springtime access, notably many burrows unblocked by ice and snow. These provided the best refuge early in the reproductive season. In the absence of red foxes, arctic foxes selected dens offering good shelter (i.e. large isolated dens). Proximity to prey-rich habitats was consistently less important than the physical aspects of dens for arctic fox. Our study shows for the first time that red foxes in the tundra select dens associated primarily with prey-rich areas, while sympatric arctic foxes do not. These results fit a model of red fox competitively interfering with arctic fox, the first detailed study of such competition in a true arctic setting.     

The arctic fox Alopex lagopus in Fennoscandia: a victim of human-induced changes in interspecific competition and predation?

After a marked decline at the beginning of the 1900s, the arctic fox Alopex lagopus population in Fennoscandia has remained at a very low level. We suggest that the main cause for the population crash was winter starvation caused by (1) over-hunting of reindeer Rangifer tarandus populations, and thus reduced carcass availability in the mountains, and (2) increased interspecific competition for these carcasses because of increased invasion of red foxes Vulpes vulpes from lower altitudes. The failure of arctic fox populations to recover, despite increasing reindeer populations in the mid 1900s, can be explained by a concurrent strong increase in red fox numbers. Analyses of countywide hunting statistics from Norway 1891–1920 suggest that there actually was an increase in red fox numbers in the period of arctic fox decline, and that the increase in reindeer populations from the 1920s to the 1950s was accompanied by a new increase in red fox numbers. We conclude that restoring arctic fox populations most likely will require a substantial and lasting reduction of red fox populations.     

Evolutionary and climatic factors affecting tooth size in the red foxVulpes vulpes in the Holarctic

Research into the geographical pattern of tooth size in the red fox,Vulpes vulpes (Linnaeus, 1758) in the Holarctic was conducted on a sample of 3806 skulls belonging to 41 fox populations. The Nearctic was represented by 948 specimens (249 females, 359 males, 340 specimens of unknown sex) belonging to 13 populations, whereas the Palearctic was represented by 2858 red foxes (1034 females, 1256 males, 568 specimens of unknown sex) from 32 populations. In the Nearctic, the largest foxes live on Kodiak Island (V. v. harrimani) and the Kenai Peninsula (V. v. kenaiensis), while the smallest ones live in California (V. v. necator) and Georgia (V. v. fulvus). In the Palearctic, the largest foxes come from the Far East (V. v. jakutensis, V. v. beringiana, V. v. tobolica), while the smallest are from the southern borders of the Eurasian range (V. v. pusilla, V. v. barbara, V. v. arabica). In both the Palearctic and Nearctic, tooth size in the fox varies depending on the geo-climatic factors. The fox’s tooth size confirms the general basis of Bergmann’s rule. In the Palearctic, specimens with larger teeth occur in cooler habitats with greater seasonality. These are first and foremost Northern and Far Eastern populations. In the Nearctic, tooth size in red foxes depends on the temperature and humidity of their habitat. Competition within the species and between species has important impact on the variation and dimorphism of tooth size in the red fox. Both in the Nearctic and Palearctic, red foxes from regions of sympatric co-occurrence with other closely relatedVulpes species, are more sexually dimorphic in terms of tooth size than red foxes from allopatric regions. Analysis of morphological distance on the basis of the size of dental characteristics shows, that in the Palearctic, the foxes from India (V. v. pusilla), while in the Nearctic, the population from Kodiak Island (V. v. harrimani) are most distant from the remaining populations. Geographic barriers such as the Bering Strait, Parry Channel, Mackenzie River, Kolyma and Omolon River systems have had a critical impact on red fox evolution. The most likely place for the evolution and diversification of the phyletic lineVulpes vulpes seems to be the Middle East region.     

Effects of Coyote Population Reduction on Swift Fox Demographics in Southeastern Colorado

ABSTRACT The distribution and abundance of swift foxes (Vulpes velox) has declined from historic levels. Causes for the decline include habitat loss and fragmentation, incidental poisoning, changing land use practices, trapping, and predation by other carnivores. Coyotes (Canis latrans) overlap the geographical distribution of swift foxes, compete for similar resources, and are a significant source of mortality amongst many swift fox populations. Current swift fox conservation and management plans to bolster declining or recovering fox populations may include coyote population reduction to decrease predation. However, the role of coyote predation in swift fox population dynamics is not well-understood. To better understand the interactions of swift foxes and coyotes, we compared swift fox population demographics (survival rates, dispersal rates, reproduction, density) between areas with and without coyote population reduction. On the Piñon Canyon Maneuver Site, Colorado, USA, we monitored 141 swift foxes for 65,226 radio-days from 15 December 1998 to 14 December 2000 with 18,035 total telemetry locations collected. Juvenile swift fox survival rate was increased and survival was temporarily prolonged in the coyote removal area. Adult fox survival patterns were also altered by coyote removal, but only following late-summer coyote removals and, again, only temporarily. Coyote predation remained the main cause of juvenile and adult fox mortality in both areas. The increase in juvenile fox survival in the coyote removal area resulted in a compensatory increase in the juvenile dispersal rate and an earlier pulse in dispersal movements. Adult fox dispersal rate was more consistent throughout the year in the coyote removal area. Coyote removal did not influence the reproductive parameters of the swift foxes. Even though juvenile survival increased, swift fox density remained similar between the areas due to the compensatory dispersal rate among juvenile foxes. We concluded that the swift fox population in the area was saturated. Although coyote predation appeared additive in the juvenile cohort, it was compensatory with dispersal.     

Red fox takeover of arctic fox breeding den: an observation from Yamal Peninsula, Russia

Here, we report from the first direct observation of a red fox (Vulpes vulpes) intrusion on an arctic fox (Vulpes lagopus) breeding den from the southern Arctic tundra of Yamal Peninsula, Russia in 2007. At the same time, as a current range retraction of the original inhabitant of the circumpolar tundra zone the arctic fox is going on, the red fox is expanding their range from the south into arctic habitats. Thus, within large parts of the northern tundra areas the two species are sympatric which gives opportunities for direct interactions including interference competition. However, direct first-hand observations of such interactions are rare, especially in the Russian Arctic. In the present study, we observed one red fox taking over an arctic fox breeding den which resulted in den abandonment by the arctic fox. On July 19, eight arctic fox pups were observed on the den before the red fox was observed on the same den July 22. The pups were never seen at the den or elsewhere after the red fox was observed on the den for as long as we stayed in the area (until August 10). Our observation supports the view that direct interference with red fox on breeding dens may contribute to the range retraction of arctic foxes from the southern limits of the Arctic tundra in Russia.     

Summer food of sympatric red fox and pine marten in the German Alps

Based on fecal analyses, we compared summer diet composition and trophic niche breadth for the sympatric red fox Vulpes vulpes (n=55 scats) and pine marten Martes martes (n=64) in the foothills of the German Alps. Mammals accounted for 41 and 51% of the consumed biomass by pine martens and red foxes, respectively, and no single mammal species exceeded 8% of the diet. The larger red fox consumed a wider range of prey sizes than the smaller pine marten, and both consumed large amounts of plants and also insects. Whereas the Levins index suggested that both predators have specialist feeding niches, the Shannon-Wiener index showed that both predators were relatively generalist. Despite its preliminary nature, our study suggests that a strict distinction between generalist and specialist trophic niches is not justified for medium-sized carnivores in the Alps, particularly as results greatly depend on the indices used.     

Influence of revegetation on predation rates by introduced red foxes (Vulpes vulpes) in south‐eastern Australian farmland

Interactions between wild carnivore abundance and landscape composition in agricultural landscapes are poorly understood despite their importance to both production and conservation. In Australia, introduced red foxes (Vulpes vulpes) prey on both native species and lambs in the temperate agricultural regions. Historically these areas were extensively cleared of native vegetation. Recently revegetation programmes have been implemented, but there is concern that this may benefit foxes and hence increase their impacts. We used an artificial prey placed in eight revegetated (6–12% cover) and 10 cleared (0–1.5% cover) landscapes of ～700 ha to assess how these landscapes influenced fox predation rates. In June and August 2006 (winter) when we expect fox populations to be relatively stable following juvenile dispersal, predation rates were 1.5–2 times higher in revegetated landscapes than in cleared landscapes. We found no evidence of microhabitat effects on predation rates suggesting these landscape‐level differences were probably due to differences in fox population density. In April 2007 (autumn) the results were more variable, possibly indicating more transient populations including dispersing juveniles at this time. Our results suggest that the impact of foxes on highly vulnerable prey could increase with revegetation. However, the benefits of revegetation to prey may offset negative impacts of foxes and future work is required to assess the likely net effects.     

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.     

Overcoming prey naiveté: Free‐living marsupials develop recognition and effective behavioral responses to alien predators in Australia

Naiveté in prey arises from novel ecological mismatches in cue recognition systems and antipredator responses following the arrival of alien predators. The multilevel naiveté framework suggests that animals can progress through levels of naiveté toward predator awareness. Alternatively, native prey may be preadapted to recognize novel predators via common constituents in predator odors or familiar predator archetypes. We tested predictions of these competing hypotheses on the mechanisms driving behavioral responses of native species to alien predators by measuring responses of native free‐living northern brown bandicoots (Isoodon macrourus) to alien red fox (Vulpes vulpes) odor. We compared multiple bandicoot populations either sympatric or allopatric with foxes. Bandicoots sympatric with foxes showed recognition and appropriate antipredator behavior toward fox odor via avoidance. On the few occasions bandicoots did visit, their vigilance significantly increased, and their foraging decreased. In contrast, bandicoots allopatric with foxes showed no recognition of this predator cue. Our results suggest that vulnerable Australian mammals were likely naïve to foxes when they first arrived, which explains why so many native mammals declined soon after fox arrival. Our results also suggest such naiveté can be overcome within a relatively short time frame, driven by experience with predators, thus supporting the multilevel naiveté framework.