Foraging behaviours and population dynamics of arctic foxes

Northern environments are often characterised by large seasonal and annual fluctuations in food abundance. In this thesis, I examined how arctic foxes (Alopex lagopus) used seasonally superabundant foods (geese and their eggs) and how access to these foods influenced population dynamics of arctic foxes. I addressed this against a backdrop of variation in lemming and vole abundance (small mammals hereafter) – the main foods of arctic foxes throughout most of their range. Field work was done at the large goose colony at Karrak Lake and surrounding areas in the Queen Maud Gulf Bird Sanctuary in Nunavut, Canada, in the spring and summers of 2000 to 2004. Behavioural observations of individually-marked arctic foxes showed that they took and cached 2,000-3,000 eggs per fox each year and that the rate at which they took eggs was largely unrelated to individual attributes of foxes (e.g. sex, size, and breeding status) and nesting distribution of geese. Further, the rate at which foxes took eggs varied considerably within individuals in that foxes were efficient at taking eggs at times and inefficient at other times. This may have resulted from foxes switching between foraging actively and taking eggs opportunistically while performing other demands such as territorial behaviours. Comparison of stable isotope ratios (13C and 15N) of fox tissues and those of their foods showed that the contribution of cached eggs to arctic fox diets was inversely related to collared lemming (Dicrostonyx torquatus) abundance. In fact, the contribution of cached eggs to overall fox diets increased fro

Monitoring the manul: guidelines for practitioners

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Habitat Selection and Risk of Predation: Re-colonization by Lynx had Limited Impact on Habitat Selection by Roe Deer

Risk of predation is an evolutionary force that affects behaviors of virtually all animals. In this study, we examined how habitat selection by roe deer was affected by risk of predation by Eurasian lynx - the main predator of roe deer in Scandinavia. Specifically, we compared how habitat selection by roe deer varied (1) before and after lynx re-established in the study area and (2) in relation to habitat-specific risk of predation by lynx. All analyses were conducted at the spatial and temporal scales of home ranges and seasons. We did not find any evidence that roe deer avoided habitats in which the risk of predation by lynx was greatest and information-theoretic model selection showed that re-colonization by lynx had limited impact on habitat selection by roe deer despite lynx predation causing 65% of known mortalities after lynx re-colonized the area. Instead we found that habitat selection decreased when habitat availability increased for 2 of 5 habitat types (a pattern referred to as functional response in habitat selection). Limited impact of re-colonization by lynx on habitat selection by roe deer in this study differs from elk in North America altering both daily and seasonal patterns in habitat selection at the spatial scales of habitat patches and home ranges when wolves were reintroduced to Yellowstone National Park. Our study thus provides further evidence of the complexity by which animals respond to risk of predation and suggest that it may vary between ecosystems and predator-prey constellations

Monitoring the manul: guidelines for practitioners

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Foraging Patterns of Arctic Foxes at a Large Arctic Goose Colony

Arctic foxes (Alopex lagopus) are the main predators of many arctic-nesting birds, and such predation can have a large impact on the nesting performance of geese in some years and in some parts of the Arctic. We examined foraging patterns of arctic foxes at a large lesser snow goose (Chen caerulescens caerulescens) colony on Banks Island, Canada, from 1996 to 1998 and were especially interested in the proportion of food that was cached for later use and the impact that fox predation had on goose productivity. Arctic foxes took mostly eggs when foraging among geese, and most of these eggs (97%) were cached for later use. Adult geese and lemmings were taken in low numbers, and most of these foods (83% of geese and 75% of lemmings) were eaten immediately. In years with high fox abundance, the foxes spent considerable effort moving eggs from old caches. This behaviour may have resulted from high rates of cache pilfering, or foxes may have been moving caches to deter cache pilfering. The impact of fox predation was low in all years, and foxes took only about 4-8% of all eggs available at the colony during incubation each year. However, caching and use of cached eggs may influence the survival of arctic foxes by forming significant parts of their winter diet or by supplementing the diets of growing young: during nesting each year, foxes took on average 900-1570 eggs per fox.Le renard arctique (Alopex lagopus) constitue le prédateur principal de nombreux oiseaux nicheurs de l'Arctique, et cette prédation peut avoir des conséquences majeures sur le succès de la couvaison des oies durant certaines années et dans certaines parties de l'Arctique. Notre étude, réalisée de 1996 à 1998, sur les schémas de recherche de nourriture du renard arctique dans une vaste colonie de petites oies des neiges (Chen caerulescens caerulescens) située dans l'île Banks, au Canada, portait surtout sur la proportion de nourriture qui était dissimulée dans des caches pour consommation ultérieure ainsi que sur l'impact qu'avait la prédation du renard sur la productivité de l'oie. Le renard arctique prélevait surtout des œufs quand il cherchait de la nourriture parmi les oies, et la plupart des œufs (97 p. cent) étaient dissimulés pour consommation ultérieure. Les oies adultes et les lemmings étaient prélevés en faible quantité, et la plupart de ces aliments (83 p. cent des oies et 75 p. cent des lemmings) étaient consommés dans l'immédiat. Durant les années d'abondance du renard, les renards faisaient des efforts considérables pour déplacer les œufs d'anciennes caches. Ce comportement peut avoir été dû à un taux élevé de vols de caches, ou bien les renards peuvent avoir déplacé leurs caches pour en décourager le vol. L'impact de la prédation du renard était faible durant toutes les années, et les renards ne prenaient annuellement qu'environ 4 à 8 p. cent de tous les œufs disponibles à la colonie durant l'incubation. La dissimulation dans des caches et l'utilisation des œufs qui y sont conservés pourraient avoir une influence sur la survie du renard arctique, car les caches représentent une partie importante du régime hivernal du renard ou complètent le régime des petits en croissance: durant la nidification annuelle, les renards prélevaient une moyenne de 900 à 1570 œufs par individu

Simultaneous Den Use by Arctic Foxes and Wolves at a Den Site in Nunavut, Canada

Arctic foxes (Alopex lagopus) and wolves (Canis lupus) often use similar den sites. Interspecific interactions and competition for den sites are therefore possible among these species. At the Kangowan River in Nunavut, Canada, we observed arctic foxes and wolves simultaneously using a den site for pup-rearing during a two-day period in the summer of 2000. We also found evidence that both species had used the den site in May that year. Interspecific interactions in summer included avoidance, tolerance, and aggression. Foxes and wolves used separate entrances and did not appear to share a common space. Our observations of arctic foxes and wolves occupying a den site concurrently suggest that avoidance and interspecific tolerance may have facilitated coexistence at this den site.Les renards arctiques (Alopex lagopus) et les loups (Canis lupus) s’installent souvent dans des tanières du même genre. Par conséquent, il est possible que chez ces espèces, il y ait des interactions inter-espèces et une certaine concurrence pour l’obtention des tanières. À la rivière Kangowan, dans le Nunavut, au Canada, on a observé des renards arctiques et des loups qui se servaient simultanément d’une tanière pour élever leurs petits pendant une période de deux jours à l’été 2000. On a également trouvé des preuves que ces deux espèces s’étaient servies de la tanière au mois de mai de cette même année. L’été, les interactions inter-espèces prenaient la forme de l’évitement, de la tolérance et de l’agression. Les renards et les loups empruntaient des entrées différentes et ne donnaient pas l’impression de partager des lieux communs. Par ailleurs, nos observations des renards arctiques et des loups qui occupent une même tanière en même temps laissent croire que l’évitement et la tolérance inter-espèces pourraient avoir joué un rôle dans la coexistence à cette tanière

Risky business: red foxes killed when scavenging from snow leopard kills

Scavenging of foods is a common but potentially dangerous behavior that exposes animals to risk of injury and even death from other animals. Here we report on two observations of red foxes that were killed when scavenging from snow leopard kills that illustrates the risks associated with scavenging for red foxes and other small and medium-sized predators

Seasonal variation in daily activity patterns of snow leopards and their prey

The daily and seasonal activity patterns of snow leopards (Panthera uncia) are poorly understood, limiting our ecological understanding and hampering our ability to mitigate threats such as climate change and retaliatory killing in response to livestock predation. We fitted GPS-collars with activity loggers to snow leopards, Siberian ibex (Capra sibirica: their main prey), and domestic goats (Capra hircus: common livestock prey) in Mongolia between 2009 and 2020. Snow leopards were facultatively nocturnal with season-specific crepuscular activity peaks: seasonal activity shifted towards night-sunrise during summer, and day-sunset in winter. Snow leopard activity was in contrast to their prey, which were consistently diurnal. We interpret these results in relation to: (1) darkness as concealment for snow leopards when stalking in an open landscape (nocturnal activity), (2) low-intermediate light preferred for predatory ambush in steep rocky terrain (dawn and dusk activity), and (3) seasonal activity adjustments to facilitate thermoregulation in an extreme environment. These patterns suggest that to minimise human-wildlife conflict, livestock should be corralled at night and dawn in summer, and dusk in winter. It is likely that climate change will intensify seasonal effects on the snow leopard's daily temporal niche for thermoregulation in the future

Spatial and temporal variation in the distribution and abundance of red foxes in the tundra and taiga of northern Sweden

Variation in the distribution and abundance of animals in space and time are key concepts of population ecology. We studied these variations in a population of red foxes (Vulpes vulpes) in the tundra and taiga of northern Sweden. We analysed 12 years (1974–1985) of snow tracking data from a large area of 65,375 km2. Specifically, we evaluated to what extent the distribution of red foxes was explained by the presence of prey and how this interacted with snow depth and altitude. We also tested for temporal linear trends in the distribution and abundance of red foxes during the study period. The distribution of red foxes was explained by the presence of rodents, hares, tetraonid species, and ungulates (i.e. carcasses). Snow depth had a negative effect on the impact of small prey on the distribution of the red foxes, whereas it had a positive effect on the impact of ungulates. The influence of hares increased with altitude. Neither distribution nor abundance of red foxes showed a positive or negative linear trend, suggesting a stable population in northern Sweden during our study. This study showed that the distribution of red foxes was not only influenced by the presence of their main prey (rodents), but also by interactions between alternative prey, altitude, and snow depth. This study also emphasizes the importance of ungulate carcasses for red foxes and for wildlife management

Foraging Behaviours of Wolverines at a Large Arctic Goose Colony

At the large Ross's goose and lesser snow goose colony at Karrak Lake, Nunavut, Canada, we saw wolverines kill two geese, take 13 eggs from 12 goose nests, and take three goose carcasses from two fox dens. Wolverines also made unsuccessful attempts to capture geese and frequently ignored eggs from nests where geese had fled the approaching wolverine. Most foods (all geese killed by wolverines and 80% of the eggs) were cached for later use, whereas few foods were eaten immediately (20% of the eggs and part of a goose taken from a fox den, which was later lost) or lost (all geese taken from fox dens). Wolverines spent little time caching foods (e.g., some foods were never covered), which suggests that recovery of these foods was not crucial to wolverines. When taking foods from fox dens, wolverines were mobbed by foxes; as a result, only one wolverine managed to consume part of a goose carcass taken from a fox den. These observations illustrate the opportunistic nature of wolverines and suggest that their scavenging success may be influenced by how well foods are defended.À l'importante colonie d'oies de Ross et de petites oies des neiges située à Karrak Lake au Nunavut (Canada), on a vu des carcajous tuer deux oies, prendre 13 oeufs dans 12 nids d'oies, et prendre trois carcasses d'oies dans deux terriers de renards. Les carcajous ont aussi essayé, sans succès, de capturer des oies et ils ignoraient souvent les oeufs des nids que les oies avaient fuis à leur approche. La plupart des aliments (toutes les oies tuées par les carcajous et 80 p. cent des oeufs) étaient dissimulés pour utilisation ultérieure, tandis que peu d'aliments étaient consommés tout de suite (20 p. cent des oeufs et une partie d'une oie prélevée dans un terrier de renard, qui a été perdue par la suite) ou perdus (toutes les oies prises dans les terriers de renards). Les carcajous passaient peu de temps à dissimuler les aliments (p. ex., certains n'étaient jamais recouverts), ce qui suggère qu'il n'est pas crucial pour eux de les retrouver. Quand les carcajous prenaient des aliments dans les terriers de renards, ils étaient assaillis par les occupants; en conséquence, un seul carcajou est parvenu à consommer une partie d'une carcasse d'oie prise dans un terrier de renard. Ces observations illustrent la nature opportuniste des carcajous et suggèrent que leur succès de récupération pourrait être influencé par la façon dont les aliments sont défendus