Digging into the behaviour of an active hunting predator: arctic fox prey caching events revealed by accelerometry

Background Biologging now allows detailed recording of animal movement, thus informing behavioural ecology in ways unthinkable just a few years ago. In particular, combining GPS and accelerometry allows spatially explicit tracking of various behaviours, including predation events in large terrestrial mammalian predators. Specifically, identification of location clusters resulting from prey handling allows efficient location of killing events. For small predators with short prey handling times, however, identifying predation events through technology remains unresolved. We propose that a promising avenue emerges when specific foraging behaviours generate diagnostic acceleration patterns. One such example is the caching behaviour of the arctic fox (Vulpes lagopus), an active hunting predator strongly relying on food storage when living in proximity to bird colonies. Methods We equipped 16 Arctic foxes from Bylot Island (Nunavut, Canada) with GPS and accelerometers, yielding 23 fox-summers of movement data. Accelerometers recorded tri-axial acceleration at 50 Hz while we obtained a sample of simultaneous video recordings of fox behaviour. Multiple supervised machine learning algorithms were tested to classify accelerometry data into 4 behaviours: motionless, running, walking and digging, the latter being associated with food caching. Finally, we assessed the spatio-temporal concordance of fox digging and greater snow goose (Anser caerulescens antlanticus) nesting, to test the ecological relevance of our behavioural classification in a well-known study system dominated by top-down trophic interactions. Results The random forest model yielded the best behavioural classification, with accuracies for each behaviour over 96%. Overall, arctic foxes spent 49% of the time motionless, 34% running, 9% walking, and 8% digging. The probability of digging increased with goose nest density and this result held during both goose egg incubation and brooding periods. Conclusions Accelerometry combined with GPS allowed us to track across space and time a critical foraging behaviour from a small active hunting predator, informing on spatio-temporal distribution of predation risk in an Arctic vertebrate community. Our study opens new possibilities for assessing the foraging behaviour of terrestrial predators, a key step to disentangle the subtle mechanisms structuring many predator–prey interactions and trophic networks.

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.

Fecal glucocorticoid metabolites as an indicator of adrenocortical activity in Arctic foxes (Vulpes lagopus) and recommendations for future studies

Measuring fecal glucocorticoid metabolites (fGCMs) is a widely used, non-invasive method for studies of stress in vertebrates. To study physiological responses in wild Arctic foxes (Vulpes lagopus) to perceived stressors such as fluctuating food availability, occurrence of competitors and predators and disturbance from human activities, a species-specific physiological validation of a method to evaluate adrenocortical activity is needed. Here we used 15 captive Arctic foxes (both males and females and juveniles and adults) to investigate fGCM concentrations following ACTH injection (physiological validation), or handling alone and compared them with their respective baseline concentrations prior to the treatments. A 5α-pregnane-3ß,11ß,21-triol-20-one enzyme immunoassay measured significant fGCM increases following both treatments. The time lags to reach peak fGCM values were 9.3 ± 1.3 h and 12.8 ± 1.7 h for ACTH and handling treatment, respectively. Concentrations of fGCMs varied a lot between individuals, but not attributed to sex nor age of the foxes. However, we found a negative relationship between boldness and fGCM concentrations. Faecal glucocorticoid metabolites concentrations did not change significantly over a period of 48 h in samples kept at temperatures reflecting winter and summer means. This would allow the collection of samples up to two days old in the wild regardless of the season. We conclude that our successfully validated method for measuring fGCMs can be used as a non-invasive tool for studies exploring various stressors both in wild and captive Arctic foxes.

Development of technology of highly accessible compound feeds with vacuum spraying of liquid components

The technology of production of compound feeds for agricultural (pigs) and unproductive (dogs, cats) animals, as well as for fur-bearing animals (minks, arctic foxes, sables) and valuable fish (sturgeon, trout, etc.), in which the replacement of expensive components of animal origin (fish meal, meat and bone meal, blood meal, offal), for extruded vegetable high-protein components (soy, sunflower or rapeseed meal, lupine, peas, soy) is carried out. The use of vacuum spraying of thermolabile liquid components (amino acids, protein-vitamin-mineral additives, vitamins, fats) on the surface of extruded pellets will allow you to obtain highly digestible feed. The kinetic regularities of the studied processes of humidification and steaming, extrusion, drying/cooling and draining are determined, and their rational modes are revealed. The technological scheme of the line for the production of highly digestible compound feeds has been developed, which includes the following equipment: hopper; extruder; dryer-cooler; liquid component injection plant, draining machine; conveyor and finished product hopper. According to the technical characteristics (overall dimensions, weight, occupied area, drive power, uniformity of application of fat on the surface of granules), the manufactured coating machine and the liquid component injection unit exceed the best world analogues. The technology of vacuum mixing with the introduction of liquid components will ensure their uniform distribution over the entire volume, reduce the duration of mixing, which will increase the productivity of the vacuum mixer and reduce energy consumption. The developed technology and promising types of technological equipment (mixer, extruder, vacuum sprayer, dryer-cooler) will make it possible to obtain highly digestible feed of a new generation with a protein content of 60 %, fat content of 40 %, with the introduction of growth stimulants, biologically active additives. An increase in the protein and fat complex will increase the digestibility of compound feeds by 10-12 %, increase weight gain by 10-12 % and reduce feed conversion by 15 %.

RESEARCH INTO THE ROLE OF BIVALVE MOLLUSKS IN THE PREVALENCE OF TRICHINELLA IN MARINE BIOCENOSES

Trichinosis is a dangerous anthropozoonotic disease caused by a nematode of the genus Trichinella. Being polyhostal, Trichinella is recorded in more than 150 species of animals, including marine mammals. While the circulation mechanism in terrestrial animal species is well-studied and has a logical explanation, the ways of infection of marine mammals remain unexplored in many respects up to the present. Among marine mammals, trichinosis is most common in walruses with the prevalence of 1.5% (Bukina L.A., 2015). The main sources of trichinosis infection for benthophagous walruses are probably their most important prey items, amphipods and bivalve mollusks. The purpose of the present paper was to study the role of bivalves in the transmission of infective material to a potential host. In the experimental infection, decapsulated trichinella larvae isolated from the muscle tissue of cage-kept arctic foxes were used. Trichinella larvae were isolated by the method of trichinelloscopy and digestion of muscle tissue in artificial gastric juice. It was found that the filter feeding structure of mussels does not let trichinella pass into the intestine. However, larvae trapped in the mantle cavity are filtered out and removed as pseudofaeces through the excurrent siphon to the environment. At the same time, they remain viable for 113 hours. The most invasive and viable were trichinella isolated from pseudofaeces and wash off from the mantle cavity (mantle complex) within 30 to 70 hours. The bio-assays performed on white outbred mice were positive. Therefore, mussels can be direct or indirect sources of the invasion. Taking into account that walruses can eat more than 3,000 mollusks in one feeding, the probability of infection increases significantly.

Fur loss syndrome and lice infestations observed on arctic foxes in central Nunavut, Canada.

As temperatures in the circumpolar north continue to warm, shifts in species distribution and the breakdown of environmental barriers for arthropods may impact the diversity and distribution of ectoparasites in Arctic ecosystems. In May 2019, fur loss over the neck and shoulders was observed on arctic foxes in a terrestrial arctic ecosystem (Karrak Lake) in central Nunavut, Canada. This was inconsistent with normal patterns of shedding winter fur and had not been observed on arctic foxes in this population over the previous 19 years of live-trapping. Operculated eggs attached to hair shafts were collected from one affected fox. Conventional PCR using universal louse primers targeting conserved regions of mitochondrial 12S and 16S rDNA confirmed that the eggs belonged to the order Phthiraptera. Sequencing results were inconclusive at the species level. Further investigation revealed a single unpublished report of an arctic fox with similar fur loss trapped on mainland Nunavut, in 1997. Adult lice collected from this fox were identified as sucking lice (potentially from the genus Linognathus). Our findings emphasize the need for further monitoring and have significant implications for trappers and wildlife management, as infestations negatively impact the pelt quality of these important furbearers.