Hematology and serum chemistry of the island fox on Santa Cruz Island

Serum and hematologic biochemistry values for island foxes (Urocyon littoralis) on Santa Cruz Island (California, USA) in April (wet season) and September (dry season) 1998 were evaluated. Serum chemistry of island foxes generally varied seasonally; 10 (40%) of the 25 serum characteristics were higher in the wet season, and three (12%) of the 25 serum characteristics were higher in the dry season. No hematologic parameters varied between seasons, although some measures varied between sexes. Blood analytes also varied with age; fox pups had higher values than adults for one hematologic and four serum parameters, whereas adult foxes had higher values for five hematologic characteristics. The information on blood chemistry provides baseline data useful in the monitoring of this threatened insular endemic carnivore.     

Mitochondrial Genomes Suggest Rapid Evolution of Dwarf California Channel Islands Foxes (Urocyon littoralis)

Island endemics are typically differentiated from their mainland progenitors in behavior, morphology, and genetics, often resulting from long-term evolutionary change. To examine mechanisms for the origins of island endemism, we present a phylogeographic analysis of whole mitochondrial genomes from the endangered island fox (Urocyon littoralis), endemic to California’s Channel Islands, and mainland gray foxes (U. cinereoargenteus). Previous genetic studies suggested that foxes first appeared on the islands >16,000 years ago, before human arrival (~13,000 cal BP), while archaeological and paleontological data supported a colonization >7000 cal BP. Our results are consistent with initial fox colonization of the northern islands probably by rafting or human introduction ~9200–7100 years ago, followed quickly by human translocation of foxes from the northern to southern Channel Islands. Mitogenomes indicate that island foxes are monophyletic and most closely related to gray foxes from northern California that likely experienced a Holocene climate-induced range shift. Our data document rapid morphological evolution of island foxes (in ~2000 years or less). Despite evidence for bottlenecks, island foxes have generated and maintained multiple mitochondrial haplotypes. This study highlights the intertwined evolutionary history of island foxes and humans, and illustrates a new approach for investigating the evolutionary histories of other island endemics.     

Spatial and temporal variation in the seroprevalence of canine heartworm antigen in the island fox

Island foxes (Urocyon littoralis) are endemic to six of the eight California Channel Islands (USA). The island fox is classified as a threatened species by the State of California, and recently three of the six subspecies have experienced abrupt population declines. As part of a continuing effort to determine the cause of the declines, we tested island fox serum samples collected in 1988 (n = 176) and 1997-98 (n = 156) over the entire geographic range of the species for seroprevalence of canine heartworm (Dirofilaria immitis) antigen. Using a commercially available enzyme-linked immunosorbent assay (PetChek, Idexx Laboratories, Westbrook, Maine, USA) we detected heartworm antigen in four of the six populations of island foxes. On San Miguel and Santa Rosa Islands, seroprevalence in adult foxes was >85% (n = 62) in 1988 and increased to 100% (n = 24) in 1997-98. On Santa Cruz Island, seroprevalence in adult foxes decreased from 83% (n = 30) to 58% (n = 26), whereas on San Nicolas Island, seroprevalence increased from 25% (n = 32) to 77% (n = 30) during the same period. All of the pups assayed (n = 33) were seronegative. The seroprevalences of heartworm reported herein for the four populations of island foxes are the highest yet reported for a fox species. However, additional demographic data reported elsewhere suggests that heartworm has not been a major factor in the recent declines of island fox populations.     

Biochemical and hematologic reference intervals for the endangered island fox (Urocyon littoralis)

Hematologic and serum biochemical data collected must be interpreted by comparison with normal reference intervals generated from healthy animals, within a similar population, because many blood parameters are influenced by diet, environment, and stress. Species-specific reference intervals for the endangered island fox (Urocyon littoralis) are not available. We reviewed hematology and serum biochemistry panels from 280 island foxes sampled from 1999-2008 and established normal reference intervals from clinically healthy foxes using a nonparametric approach. Blood parameters were analyzed for differences in age, sex, island of origin, and captivity status. Alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and creatine kinase activities, as well as calcium and phosphorus concentrations, were significantly higher in juveniles than in adults, but total protein and globulin concentration was lower for juveniles than for adults. Lymphocyte and eosinophil counts, and blood urea nitrogen (BUN) concentration, in foxes from the northern Channel islands of California, USA (Santa Cruz, Santa Rosa, and San Miguel) were higher when compared with foxes from Santa Catalina Island to the south. Higher lymphocyte and eosinophil numbers in the northern island foxes may be associated with increased levels of parasitism on the northern islands. Differences in BUN concentration in both free-ranging and captive foxes may reflect dietary differences among islands. Although aggressive conservation programs have been enacted, island foxes are still susceptible to infectious and neoplastic diseases and, potentially, to toxins. Island fox species-specific reference intervals will enable managers and veterinarians to better care for sick and injured foxes and will contribute to future population health monitoring.     

Factors Affecting Glucocorticoid and Thyroid Hormone Production of Island Foxes

The island fox (Urocyon littoralis) is native to 6 of the 8 Channel Islands of California, USA. The species experienced a population decline in the 1990s but recovered after predatory golden eagles (Aquila chrysaetos) were relocated and feral pigs (Sus scrofa), a main food source for the eagles, were removed. As part of an ongoing conservation program, the National Park Service conducts yearly health surveys on foxes residing on Santa Rosa and San Miguel islands. In this study, we document non-invasive measures of stress and nutritional status from fecal samples collected during surveys from 2009 to 2015. We collected samples defecated in traps overnight or during handling and measured concentrations of glucocorticoid (GC) and triiodothyronine (T3) metabolites using validated assays. We used generalized linear mixed models to assess the relationships between hormones, season, island, age class, sex, body condition, reproductive status, and ectoparasite presence. Overall, males had marginally lower fecal T3 concentrations than females. Concentrations of both hormones positively correlated with body condition. Fecal GC production varied seasonally; concentrations were highest from December to February and declined through the summer and fall. During summer, younger females and those with signs of recent reproduction had higher fecal GC concentrations than older females or those without evidence of reproduction. Fecal T3 concentrations did not vary in relation to season, age, or reproductive status, but on San Miguel Island were positively correlated with ectoparasite presence. There were no other significant differences between islands. Our results provide hormone data for island foxes and demonstrate that production varies in relation to seasonal and biological factors. These reference data will serve as a comparison for future health surveys and allow managers to identify factors associated with increased stress or reduced nutritional state. © 2019 The Wildlife Society.     

Effects of roads on survival of San Clemente Island foxes

Roads generate a variety of influences on wildlife populations; however, little is known about the effects of roads on endemic wildlife on islands. Specifically, road-kills of island foxes (Urocyon littoralis) on San Clemente Island (SCI), Channel Islands, California, USA are a concern for resource managers. To determine the effects of roads on island foxes, we radiocollared foxes using a 3-tiered sampling design to represent the entire population in the study area, a sub-population near roads, and a sub-population away from roads on SCI. We examined annual survival rates using nest-survival models, causes of mortalities, and movements for each sample. We found the population had high annual survival (0.90), although survival declined with use of road habitat, particularly for intermediate-aged foxes. Foxes living near roads suffered lower annual survival (0.76), resulting from high frequencies of road-kills (7 of 11 mortalities). Foxes living away from roads had the highest annual survival (0.97). Road-kill was the most prominent cause of mortality detected on SCI, which we estimated as killing 3–8% of the population in the study area annually. Based on movements, we were unable to detect any responses by foxes that minimized their risks from roads. The probabilities of road-kills increased with use of the road habitat, volume of traffic, and decreasing road sinuosity. We recommend that managers should attempt to reduce road-kills by deterring or excluding foxes from entering roads, and attempting to modify behaviors of motorists to be vigilant for foxes. © 2011 The Wildlife Society.     

Studies on sylvatic echinococcosis. V. Factors influencing prevalence of Echinococcus multilocularis Leuckart 1863, in red foxes from North Dakota, 1965--1972

A total of 1,153 red foxes, Vulpes vulpes, was examined for strobilae of Echinococcus multilocularis from 2 geographic regions in North Dakota during 1965 through 1972. Echinococcus multilocularis was found in 184 (16%) of these foxes. The data including date and location of collection, age and sex of the host, and presence or absence of the cestode were used to assess the relative influence of collection interval (sampling period), climatic season, geographic location, and age and sex of the host on the prevalence of the adult cestode. The rate of infection varied significantly with collection interval, which was probably attributable to annual changes in the overall environment. Seasonally, the highest prevalences were observed during summer (32.4%) followed by spring (25.3%), autumn (13.7%) and winter (6.4%). Differences in prevalence between adult and juvenile foxes and that between male and female foxes were not significant. A 3-factor analysis of variance showed the order of importance of the significant variables to be collection interval, season, and the interaction of collection interval and season. A 4-factor ANOVA, which in addition to the above variables included geographic location, showed that the collection interval-location interaction had significant effects on prevalence. Also, evidence is presented that suggests that density of the definitive host may in part be responsible for annual fluctuation in prevalence.     

When the Ghost of Predation has Passed: Do Rodents from Islands with and without Fox Predators Exhibit Aversion to Fox Cues?

Anti‐predator behavior can alter the dynamics of prey populations, but little is known about the rate at which anti‐predator behavior is lost from prey populations following predator removal. The Channel Islands differ in whether they have historically contained a top predator, the Island Fox (Urocyon littoralis), in evolutionary time (approximately 6200–10 000 yr). On a historically fox‐containing island and two historically fox‐free islands in 2007, I deployed live traps that contained olfactory cues of fox predators (fox feces), olfactory cues of an herbivore (horse feces) or a no‐feces control. Due to a captive breeding program, foxes on the historically fox‐containing island were effectively removed from 1998 to 2004. Rodents from one of the historically fox‐free islands did not respond to fox cues, whereas rodents on the historically fox‐containing island were more likely to be captured in a control trap and less likely to be captured in a fox‐cue trap. Results from the other historically fox‐free island that experienced a recent population bottleneck and period of captive rearing exhibited a preference for horse‐scented traps. These results suggest that, on islands where foxes are the primary predators, anti‐predator behavior in response to olfactory cues is not likely to be rapidly lost by short‐term removals of foxes, although the nature of anti‐predator behavior may depend upon founder events and recent population dynamics (e.g. population bottlenecks or several generations in captivity).     

Geographical distribution pattern and interisland movements of Orii’s flying fox in Okinawa Islands, the Ryukyu Archipelago, Japan

The study of mobile animals such as flying foxes in insular habitats involves clarifying the population status on each island and determining the factors affecting movement patterns among the islands in their distributional range. We visited 25 of the Okinawa Islands and documented the number of Orii’s flying foxes Pteropus dasymallus inopinatus from August 2005 to May 2006. We also conducted a monthly road census on the main island (Okinawa-jima Island) and six adjacent islands from June 2006 to January 2007 and counted the number of fruit-bearing trees of the bats’ four main food plants. The results of classification and regression tree analysis suggested that distance from the main island was a primary factor in determining the distribution pattern and population size of this flying fox, whereas island area, number of plant species, and food availability did not directly affect population size. The number of flying foxes on each island tended to decrease with an increase in distance from the main island; no flying foxes existed on islands >30 km away from the main island. On the other hand, the results of the monthly census showed that the population size on each island fluctuated seasonally. Individuals may move between islands in response to seasonal changes in food availability. In conclusion, the distribution and abundance of Orii’s flying foxes in the Okinawa Islands may be determined by the rate of immigration/emigration, depending on each island’s distance from the main island. Seasonal changes in food availability may act as a trigger for interisland movement, but that movement may be restricted by island connectivity.     

Resource utilization by two insular endemic mammalian carnivores,the island fox and island spotted skunk

We compared resource utilization of two insular endemic mammalian carnivores, the island spotted skunk and island fox, along niche dimensions of space, food, and time on Santa Cruz Island. We predicted that resource use by foxes and skunks would differ along one or more niche dimensions, and that both species would have broader niches or higher densities compared with mainland relatives. Island foxes and island spotted skunks differed to some extent in habitat use, diets, and circadian activity, which may account for their long-term coexistence. Nonetheless, substantial overlap between skunks and foxes in spatial, dietary, and temporal dimensions suggests that competition between the two species does occur. Moreover, competition may be asymmetric, affecting skunks more than foxes. Compared with mainland foxes, island foxes have smaller body size, smaller home range, increased population density, increased diurnal activity, and behavior that is more highly inquisitive and less flightprone all common features of insular faunas. Island skunks, however, apparently have not developed these changes, perhaps due to asymmetric competition with foxes in conjunction with severe ecosystem disturbances caused by feral sheep.     

Nesting Habitat Creation Enhances Recruitment in a Predator‐Free Environment: Malaclemys Nesting at the Paul S. Sarbanes Ecosystem Restoration Project

Aquatic turtles worldwide are plagued with habitat loss due to development and shoreline alteration that destroys the terrestrial–aquatic linkage which they must cross to reproduce successfully. Furthermore, nesting habitat loss can concentrate nesting, increasing nest predator efficiency. We describe how the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island created nesting habitat for Malaclemys terrapin (Diamondback Terrapin), and document nesting success in response to construction progress and the absence of raccoons and foxes, the primary nest predators. We monitored terrapin nests throughout the nesting seasons from 2002 to 2011 to determine overall and within‐nest survivorship. Female terrapins began nesting on the restoration project within 1 year but planned construction during the study eliminated some nesting areas and opened previously inaccessible areas. Overall, nest survivorship was considerably higher than mainland nesting areas due to the absence of raccoons and foxes on the island and within‐nest survivorship was similar. Egg size, hatchling size, and the frequency of shell scute anomalies were similar to other terrapin populations, suggesting normal developmental conditions on the island. We documented annual variation in hatchling size that correlated negatively with mean air temperature during the incubation season. Our results indicate that restored or created isolated island habitat can be located rapidly by terrapins and can become an important source of recruitment in regions where nesting habitat is limited and predation is high. Poplar Island illustrates how habitat loss and restoration can affect turtle populations by revealing the changes in nesting patterns and success in newly created, predator‐free habitat.     

Pathology and Epidemiology of Ceruminous Gland Tumors among Endangered Santa Catalina Island Foxes (Urocyon littoralis catalinae) in the Channel Islands,USA

In this study, we examined the prevalence, pathology, and epidemiology of tumors in free-ranging island foxes occurring on three islands in the California Channel Islands, USA. We found a remarkably high prevalence of ceruminous gland tumors in endangered foxes (Urocyon littoralis catalinae) occurring on Santa Catalina Island (SCA)—48.9% of the dead foxes examined from 2001–2008 had tumors in their ears, and tumors were found in 52.2% of randomly-selected mature (≥ 4 years) foxes captured in 2007–2008, representing one of the highest prevalences of tumors ever documented in a wildlife population. In contrast, no tumors were detected in foxes from San Nicolas Island or San Clemente Island, although ear mites (Otodectes cynotis), a predisposing factor for ceruminous gland tumors in dogs and cats, were highly prevalent on all three islands. On SCA, otitis externa secondary to ear mite infection was highly correlated with ceruminous gland hyperplasia (CGH), and tumors were significantly associated with the severity of CGH, ceruminous gland dysplasia, and age group (older foxes). We propose a conceptual model for the formation of ceruminous gland tumors in foxes on SCA that is based on persistent, ubiquitous infection with ear mites, and an innate, over exuberant inflammatory and hyperplastic response of SCA foxes to these mites. Foxes on SCA are now opportunistically treated with acaricides in an attempt to reduce mite infections and the morbidity and mortality associated with this highly prevalent tumor.     

Home range and movements of arctic foxes Alopex lagopus in Svalbard

Summary Movements and home ranges of arctic foxes Alopex lagopus were studied in two regions of Svalbard by means of radio tracking (n= 17), ear tagging (n= 192) and visual observations. The movements of radio collared foxes were highly variable, and most foxes roamed over wide areas at least during periods of the year. Home range size was estimated for 11 foxes when more stationary and for three other less stationary foxes, and were in the range 5–120km². During non-stationary periods several foxes roamed over areas 500–1000 km² or more. These movements may more correctly be classified as nomadic, and should not be termed home ranges. Only 3 of 12 radio collarec. foxes that disappeared from an area, returned later. Seven of the 17 foxes were relocated to the same area in more than one season. Overlap of home ranges was extensive, even more so when a number of non-tagged foxes in the regions were included. The heavier juveniles and adults were more sedentary than those of weight lower than median.     

Mitochondrial Analysis of the Most Basal Canid Reveals Deep Divergence between Eastern and Western North American Gray Foxes (Urocyon spp.) and Ancient Roots in Pleistocene California

Pleistocene aridification in central North America caused many temperate forest-associated vertebrates to split into eastern and western lineages. Such divisions can be cryptic when Holocene expansions have closed the gaps between once-disjunct ranges or when local morphological variation obscures deeper regional divergences. We investigated such cryptic divergence in the gray fox (Urocyon cinereoargenteus), the most basal extant canid in the world. We also investigated the phylogeography of this species and its diminutive relative, the island fox (U. littoralis), in California. The California Floristic Province was a significant source of Pleistocene diversification for a wide range of taxa and, we hypothesized, for the gray fox as well. Alternatively, gray foxes in California potentially reflected a recent Holocene expansion from further south. We sequenced mitochondrial DNA from 169 gray foxes from the southeastern and southwestern United States and 11 island foxes from three of the Channel Islands. We estimated a 1.3% sequence divergence in the cytochrome b gene between eastern and western foxes and used coalescent simulations to date the divergence to approximately 500,000 years before present (YBP), which is comparable to that between recognized sister species within the Canidae. Gray fox samples collected from throughout California exhibited high haplotype diversity, phylogeographic structure, and genetic signatures of a late-Holocene population decline. Bayesian skyline analysis also indicated an earlier population increase dating to the early Wisconsin glaciation (~70,000 YBP) and a root height extending back to the previous interglacial (~100,000 YBP). Together these findings support California’s role as a long-term Pleistocene refugium for western Urocyon. Lastly, based both on our results and re-interpretation of those of another study, we conclude that island foxes of the Channel Islands trace their origins to at least 3 distinct female founders from the mainland rather than to a single matriline, as previously suggested.     

Field cost of activity in the kit fox, Vulpes macrotis

Field metabolic rates and daily movement distances were measured in 26 individual kit foxes (Vulpes macrotis) over a 29-mo period in the southern Mojave Desert of California. Kit foxes traveled long distances (up to 32 km d(-1)), with males usually traveling farther than females. Daily movement distances were affected by season, since males traveled the greatest distances in spring and females traveled farthest in summer. Individual foxes tracked multiple times demonstrated repeatability of daily movement distance between nights, between summer and winter, and between consecutive winters. The field cost of activity per unit distance was estimated as 15.6 kJ km(-1) from the partial regression coefficient of a multiple linear regression model, a value not significantly different from the incremental cost of locomotion derived from laboratory measurements. The field cost of activity was not affected by season, despite the expectation of higher costs of activity in the winter with increased thermoregulatory expenditure. The large daily movement distances resulted in significant activity energy expenditure (11%-33% of field metabolic rate), with a mean of 21% of field metabolic rate expended in activity during nonreproductive seasons.     

Proteomic Analysis of Highly Prevalent Amyloid A Amyloidosis Endemic to Endangered Island Foxes

Amyloid A (AA) amyloidosis is a debilitating, often fatal, systemic amyloid disease associated with chronic inflammation and persistently elevated serum amyloid A (SAA). Elevated SAA is necessary but not sufficient to cause disease and the risk factors for AA amyloidosis remain poorly understood. Here we identify an extraordinarily high prevalence of AA amyloidosis (34%) in a genetically isolated population of island foxes (Urocyon littoralis) with concurrent chronic inflammatory diseases. Amyloid deposits were most common in kidney (76%), spleen (58%), oral cavity (45%), and vasculature (44%) and were composed of unbranching, 10 nm in diameter fibrils. Peptide sequencing by mass spectrometry revealed that SAA peptides were dominant in amyloid-laden kidney, together with high levels of apolipoprotein E, apolipoprotein A-IV, fibrinogen-α chain, and complement C3 and C4 (false discovery rate ≤0.05). Reassembled peptide sequences showed island fox SAA as an 111 amino acid protein, most similar to dog and artic fox, with 5 unique amino acid variants among carnivores. SAA peptides extended to the last two C-terminal amino acids in 5 of 9 samples, indicating that near full length SAA was often present in amyloid aggregates. These studies define a remarkably prevalent AA amyloidosis in island foxes with widespread systemic amyloid deposition, a unique SAA sequence, and the co-occurrence of AA with apolipoproteins.     

Impact of historical founder effects and a recent bottleneck on MHC variability in Commander Arctic foxes (Vulpes lagopus)

Populations of Arctic foxes (Vulpes lagopus) have been isolated on two of the Commander Islands (Bering and Mednyi) from the circumpolar distributed mainland population since the Pleistocene. In 1970-1980, an epizootic outbreak of mange caused a severe population decline on Mednyi Island. Genes of the major histocompatibility complex (MHC) play a primary role in infectious disease resistance. The main objectives of our study were to compare contemporary variation of MHC class II in mainland and island Arctic foxes, and to document the effects of the isolation and the recent bottleneck on MHC polymorphism by analyzing samples from historical and contemporary Arctic foxes. In 184 individuals, we found 25 unique MHC class II DRB and DQB alleles, and identified evidence of balancing selection maintaining allelic lineages over time at both loci. Twenty different MHC alleles were observed in mainland foxes and eight in Bering Island foxes. The historical Mednyi population contained five alleles and all contemporary individuals were monomorphic at both DRB and DQB. Our data indicate that despite positive and diversifying selection leading to elevated rates of amino acid replacement in functionally important antigen-binding sites, below a certain population size, balancing selection may not be strong enough to maintain genetic diversity in functionally important genes. This may have important fitness consequences and might explain the high pathogen susceptibility in some island populations. This is the first study that compares MHC diversity before and after a bottleneck in a wild canid population using DNA from museum samples.     

Hematology and serum chemistry of the island spotted skunk on Santa Cruz Island

We determined serum biochemistry and hematologic values for island spotted skunks (Spilogale gracilis amphiala) on Santa Cruz Island (California, USA). Samples were collected from island spotted skunks chemically restrained with ketamine hydrochloride and acepromazine in August 1999 (dry season) and from skunks manually restrained in August 2000 (dry season) and January 2001 (wet season). One parameter, glucose, significantly differed with season, with higher levels during the wet season. Serum chemistry and hematologic profiles suggest that method of restraint (manual or chemical), as well as other methodologic details, may influence blood characteristics in the island spotted skunk.     

长江源区同域分布兔狲、藏狐和赤狐的时空重叠度

兔狲(Otocolobus manul)、藏狐(Vulpes ferrilata)和赤狐(V. vulpes)是青藏高原三江源区域分布的重要小型食肉兽。本研究于2014年6月至2019年9月在青海省长江源区沱沱河和通天河沿岸选取208个位点布设红外相机, 通过所获取的时空分布数据比较了上述3种同域分布小型食肉兽的时空利用情况。通过空间重叠度系数的比较分析, 兔狲和藏狐、兔狲和赤狐以及藏狐和赤狐之间的空间重叠度系数分别为0.25、0.48和0.17, 这表明兔狲、藏狐和赤狐三者在空间利用上存在一定的差异。通过核密度估计方法分析, 兔狲和藏狐属典型的昼行性动物, 而赤狐以夜行性活动为主。兔狲、藏狐和赤狐每个物种在冷暖两季的日活动节律重叠指数分别为0.83、0.78和0.88。两两比较分析表明, 兔狲和藏狐二者的日活动节律重叠指数最高(0.84), 兔狲和赤狐在夜间活动时段存在一定重叠(0.63), 而藏狐和赤狐的时间生态位分化最明显, 重叠指数最低(0.48)。此外, 在暖季, 两两物种之间的日活动节律重叠指数均小于其冷季的重叠指数。综上所述, 长江源区兔狲、藏狐和赤狐3种小型食肉兽可通过空间和时间资源的利用差异来降低物种间的干扰和竞争, 从而达到同域物种共存的目的。     

Predation of released pheasants <Emphasis Type="Italic">Phasianus colchicus</Emphasis> on lowland farmland in the UK and the effect of predator control

We present data accumulated over the last 25 years on predation of radio-tracked released pheasants. In studies of birds during the autumn/winter at six pheasant shoots with high-density releases managed by full-time gamekeepers, predation of released pheasants by foxes before the shooting season began (July–September) averaged 19.2?±?4.0% per site, and during the shooting season (October 1st–February 1st), a further 15.9?±?1.9% were predated. The range in 3-year average predation rates between sites before shooting began was 8.6 to 42.4%. At seven different sites during the spring and summer, between 20 and 71% of released or wild hens that survived the shooting season were predated, mainly by foxes, between mid-March and mid-July. Predation was significantly higher at sites with low-level predator control (59?±?4.7%) compared to those with high-level control (30?±?5.3%). At three of the four sites with low predator control between 5 and 22% of nest failures were caused by incubating hens being predated by foxes. Our data quantify for the first time highly variable predation rates of released pheasants before and during the winter shooting season which we suggest was influenced by a range of site and management factors. During the spring and summer, our data provide evidence that predation of adult hen pheasants as well as nest predation can suppress breeding success and that predator control can reduce these losses.