The arctic fox is an elusive animal, and the only native mammal in Iceland. They play and important role in many arctic ecosystems around the world by bringing nutrients from the sea inland. Arctic foxes are present near Skálanes, but the exact locations of the dens are unknown. We aim to map the dens to make the foxes easier to find and facilitate further research. We will identify the dens, take their GPS coordinates, and create a map for future researchers to use. Research building on these maps could include mapping the territories associated with different dens.
Arctic foxes live across Iceland, but the populations are distinct due to geographical separation. This means that foxes from different parts of the country do not reproduce with each other often, causing them to be genetically distinct, possibly leading to functional differences. Genetic information from hair could help researchers understand how the eastern population differs from the rest, how long ago and how completely the populations were separated, and if the foxes are inbred. One way to examine these differences is by sampling fox DNA and analysing it. To do this, there are a few things we need to know: and how do we sample their DNA without bothering them?
Previous genetic research on arctic foxes in Iceland has occasionally used data from trap-and-release methods, but most samples are from foxes that have been shot by hunters. Alternatively, non-invasive sampling of faeces, saliva, and hair has been used to sample DNA from different mammals around the world. Hair sampling is the most reliable because the DNA in hair follicles is stable and least likely to be contaminated. Often hair is sampled with sticky tape or glue, but the wet environment of Iceland makes this method impractical. In arctic environments, researchers have sampled wolverines, lynx, and red foxes with blunted barbed wire hair traps. This year, we will be testing two different blunted barbed wire hair traps to see if they work well on arctic foxes.
First, we will be using a short, sturdy pole wrapped in wire with a piece of bait (such as canned tuna) on top (figure 1. When foxes jump up to the top of the pole to eat the bait, the hair will be snagged and pulled out by the junction where the wires of the barb cross. The same principle is used in the second method, where a small region is fenced off with wire and bait placed in the middle (figure 2). Foxes can either crawl under or jump over the wire to reach the bait, snagging hair in the process. The wire will be checked regularly to collect any hairs and the bait will be replaced as necessary. If one or both methods are successful, they can be used in future research on arctic foxes at Skálanes and elsewhere.
As part of our investigation, we will also be examining the fox faeces. Faeces is a great way to learn about an animal or population of animals without disturbing them, or even seeing them. For example, faeces often contain the eggs (also called oocytes) of any intestinal parasites the animal might be carrying, as well as indications of its diet, such as bone fragments, fur, or feathers. These indicators can be identified by dissecting the faeces manually or by dissolving the faeces in liquid and observing it under a microscope. The microscope helps us identify structures or fragments too small for the human eye to see, which can tell us a great deal. For example, fish have tiny bones in their ears called otoliths, which are often unique to different types of fish. Identifying otoliths in faeces would tell us not only that the fox ate fish, but also what sort of fish it was! Determining the diet of the foxes can help us understand how they might be affected by climate change, as the abundance and distribution of the prey species may change. We will also be identifying and counting the parasite eggs, which will give us information on what parasites are present in predators around Skálanes and how intense any infections might be. This can have implications for the health of the foxes as well as other predatory animals in the region. For example, many parasites infecting foxes can also infect domestic dogs.
The arctic fox population of Skálanes has not previously been studied, and as such the information we collect on this expedition will form a baseline for further investigations into the health, behaviour, and genetics of the arctic foxes.
Further reading and relevant academic papers:
Bremner-Harrison S, Harrison SWR, Cypher BL, Murdoch JD, Maldonado J, Darden SK. Development of a Single-Sampling Noninvasive Hair Snare. Wildlife Society Bulletin. 2006;34.
Ehrich D, Carmichael L, Fuglei E. Age-dependent genetic structure of arctic foxes in Svalbard. Polar Biology. 2012;35:53-62.
Gharajehdaghipour T, Roth JD, Fafard PM, Markham JM. Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens. Scientific Reports. 2016;6.
Hasselgren, M, Angerbjörn, A, Eide, NE, et al. Genetic rescue in an inbred Arctic fox (Vulpes lagopus) population. Proceedings of the Royal Society. 2018;285(1875).
Henry P, Henry A, Russello MA. A noninvasive hair sampling technique to obtain high quality DNA from elusive small mammals. Journal of visualized experiments. 2011;49.
Kendall KC, McKelvey KS. Chapter 6: Hair Collection. In: Long RA, MacKay P, Ray JC, Zielinski WJ, editors. Noninvasive survey methods for North American carnivores. Washington, D. C.: Island Press; 2008. p. 135-76.
Love Dalén, Eva Fuglei, Páll Hersteinsson, Christian M. O. Kapel, James D. Roth, Gustaf Samelius, Magnus Tannerfeldt, Anders Angerbjörn, Population history and genetic structure of a circumpolar species: the arctic fox, Biological Journal of the Linnean Society, Volume 84, Issue 1, January 2005, Pages 79–89, https://doi.org/10.1111/j.1095-8312.2005.00415.x
Mulders, Robert & Boulanger, John & Mulders, David. (2007). Estimation of population size for wolverines Gulo gulo at Daring Lake, Northwest Territories, Using DNA based mark-recapture methods. Wildlife Biology – WILDLIFE BIOL. 13. 10.2981/0909-6396(2007)13[38:EOPSFW]2.0.CO;2.
Myšková E, Bro ž M, Fuglei E, Kvi č erová J, Mácová A, Sak B, et al. Gastrointestinal parasites of arctic foxes (Vulpes lagopus) and sibling voles (Microtus levis) in Spitsbergen, Svalbard. Parasitology Research. 2019;118:3409 – 18.
Norén K, Angerbjörn A, Hersteinsson P. Population structure in an isolated Arctic fox, Vulpes lagopus , population: the impact of geographical barriers. Biological Journal of the Linnean Society. 2009;97:18-26.
Ramón-Laca A, Soriano L, Gleeson D, Godoy JA. A simple and effective method for obtaining mammal DNA from faeces. Wildlife Biology. 2015;21(4):195-203, 9.
Sherrard-Smith E, Chadwick EA, Cable J. The impact of introduced hosts on parasite transmission: opisthorchiid infections in American mink (Neovison vison). Biol Invasions. 2015;17:115-22.