Monitoring the population of arctic foxes in East Iceland

The Icelandic arctic fox (Vulpes lagopus) (figure 3), Iceland’s only native terrestrial mammal, is thought to have arrived at the end of the last Ice Age and has since remained genetically isolated from mainland Europe (Mellows, 2012). The arctic fox is well adapted to living in cold weather, with a small surface area to volume ratio and thick, insulating fur. In Iceland the arctic fox has a stable diet of birds throughout the year. It therefore does not experience the short-term population cycles seen in other Nordic populations where their diet consists mainly of lemmings (Unnsteinsdóttir, 2016). Arctic foxes stay in breeding pairs and defend a territory, where they raise a litter of young each summer. Monitoring of the arctic fox population in Iceland is important as in other European countries the population declined and has not recovered since the fur trade in the 1920s, despite full legal protection. This is thought to be due to changing climate impacting both the foxes’ prey and increased competition. In Iceland however, despite heavy exploitation and hunting, along with the attempt to exterminate the population in 1958 to reduce the economic damage to eider and sheep farmers, the arctic fox population has been stable (Hersteinsson, 1989).

Pollutants, such as mercury and other persistent organic pollutants have been found increasingly in the tissues of marine fauna, thought to be due to the increasing anthrophonic events, such as the release of stored heavy metals in snow melt (Bocharova, 2013). The two main sources of food for Icelandic foxes in Iceland are rock ptarmigans, which are heavily preyed on by inland populations, and coastal populations preyed also on marine fauna and sea birds (Carbonell Ellgutter, 2020; Dalerum, 2012). In Bocharova’s study in 2013, she looked at the correlations between the feeding ecology and their mercury level in three locations, Iceland and Bering Island, which include range of inland and coastal feeding strategies, along with the island of Mednyi, which only had coastal feeding ecology. In the study it was found that foxes inland primarily fed on terrestrial vertebrates such as rock ptarmigan and wood mice, had drastically less contamination compared to those who adapted a marine diet, including visibly less skin and hair abnormalities. The population on Mednyi is experiencing a population decrease while Bering and Iceland have a stable population, contamination could be influencing winter survival rate and decrease life expectancy. Foxes in coastal habitats in Iceland were found to have a greater isotope niche breadth compared to that of inland foxes under isotopic analysis, showing them to be greater variation in dietary strategies (Dalerum, 2012).

For this project we will be setting up a monitoring station of arctic fox population and diet on the east coast of Iceland. A higher density of the arctic fox is located on the West coast, near the Hornstrandir Nature Reserve, the only area in Iceland where arctic foxes are protected from hunting and without permanent human settlement. The Westfjords, where Hornstrandir Nature Reserve is located, have healthy and successful seabird colonies, which is a year-round food source for coastal arctic fox populations. Setting up a monitoring project with Skálanes Nature and Heritage Centre would help to gain further knowledge about arctic foxes on the eastern coast to compare to the work done on the western coast and over time a population demographic can be created and compared to that of the western coast.

For this project we will be looking into factors affecting the arctic fox’s activity and to find explanations, whether it be abiotic influence or prey activity. With baseline data on the arctic fox population it can be used to start up more advanced research, such as pollution contamination levels and DNA sequencing comparisons. Understanding the factors that affect the arctic foxes’ activity and therefore success in hunting and rearing young are important for explanations of population change in the foxes. From previous studies, it has been seen that those who adapt to a marine diet have more successful litters, which is achieved by having smaller litter sizes and breeding more regularly (Dalerum, 2012). Both foxes and their prey species can be affected by anthropogenic events; this heightens the importance of establishing baseline data for Skálanes’ arctic fox population. As demonstrated in (Carbonell Ellgutter 2012) and (Pálsson, 2016), the Icelandic arctic fox population decline to the 1970s was thought to be due to a corresponding decline in rock ptarmigan populations in the same period, acting as a limiting factor. The recovery of the population is theorised to be due to the increase in goose and sea bird colonies, despite little recovery of ptarmigan numbers. Analysis of arctic fox population dependency and limitation factors such as prey species on the eastern coast will help to add data to Iceland’s arctic fox census and inform on reasons for population variation between regions.

Aims

• Establish baseline data on the arctic fox population in the Skálanes area, including population estimate, distribution between dens, litter sizes, and individual health.
• Identify the types and variation of prey brought back to the den or observed catching.
• Investigate the activity of the arctic foxes based on time of day, temperature, wind speeds and other abiotic factors that could influence hunting success and prey behaviour.

Hypotheses

• There will be a decrease in activity, such as actively hunting, and time spent above ground during high wind, increased rainfall and poor visibility weather.
• Activity will be influenced by the time of day despite minimal variation in light intensity.
• Fox activity will coincide with the activity of its prey species, sea birds and the tidal range.
• Dens located closer to the sea bird colonies will have greater hunting success, in the form of successful cub rearing and increased prey caught observations (observations, camera traps and faeces samples).
• H0 – There will be no significant difference between the activity of the foxes and the severity of the weather.
• H0 – Activity will not be significantly influenced by the time of day (light intensity)
• H0 – Activity will not be significantly influenced by tidal range or prey species activity
• H0 – No significant difference will be found between hunting success and den location.

• Locating arctic fox dens and recording the location of occupied dens with the help of a map made by Ólafur Pétursson of Skálanes. The use of drones with infrared and IR cameras provided by Emmett M Smith of Earlham College to locate dens farther away from the centre.
• Setting up of camera traps at each den location to observe number of individuals, health, behaviour, and diet. Cameras may need to be secured to a post due to lack of foliage to secure to. These traps will be checked every 48 hours, cameras closer to the centre will be checked more often. Each check, memory card will be switched, and batteries checked.
• Population will be estimated by counting the number of adults in each observed den and the number of pups seen in each den. This will be done after all of the camera trap data has been collected in order to give the most accurate estimate of the number of animals present.

• From the vicinity of each safely accessible den, collection of faeces or hair samples taken using protective clothing and storing of samples in bags to be transported back to centre. This will be done far enough away from the den so as not to disturb the foxes.
• When watching the foxes with binoculars and over camera trap footage, an ethogram will be used. Recording of the number and type of prey brought back, the amount of time spent above and below ground, time spent interacting with conspecifics, time spent away from the den. Time of day will always be recorded, along with tidal times.
• Activity of sea bird’s data will be taken through observations done in other research projects being undertaken at the same time.
• When the dens are abandoned at the end of the summer, closer examination and collection of faecal samples for analysis of prey species.