28.10.2014 - 12:04

Decrease in Icelandic Arctic Fox Population



The Arctic fox poulation in Iceland has declined for the first time in 30 years.

According to the newest population assesment there are around a 3rd less individuals now then from the last assesment in 2010.

The decline is both seen in areas where the Arctic fox is hunted and also the protected areas such as the Hornstrandir Nature Reserve in the Westfjords.  

The cause of the decline is yet unknown but is likely connected to climate contitions, food resourses, animal health and poluntants.

Arctic fox hunters are key partners in the monitoring and research of the Arctic fox population by sending in carcasses of hunted animals for dissection and age assesment.

 

The newest calculations on the Icelandic Arctic fox popultion shows that the numbers have dropped dramaticly over the past years. This is the the firs time since the population cencuses have taken place that a decline has been seen. In the autumn of 2007 the population ad been on the increase for more then 30 years and was much higher then when the populaion estimates were started in 1979(1). At that time the popultion was starting to recover from beng at a historical low. The population change was uneven with a slow increase recorded in the first 15-20 years until 1997 when the poplation started to increase at a much faster rate, and it was during this time that there was also an increase in the winter hunting  of foxes, though the spring time den hunting continued at the same rate. The population increased still faster again from 2004 with a high point reached in 2008. In the next 2 years 2009 and 2010 the Arctic fox population decreased by around 32% across Iceland and scientific studies are showing that this decrease is continuing from 2011-2014 tho probably at not such a high rate as 2008-2010.



The population estimates are calculated back in time to give an historical population minimum per year. The last assesment was done in 2010 and gave yearly population estimates from the first year to 2007. It is only possible to make an estimate with any certainty upto 3-5 years back due to the large un hunted population of young when the assesments are made. The margin of error is higher the more animals which are alive from your year of assesment. We will ot be able to assess the populations of 2011-2014 safely until more foxes from these years have been hunted. (Arctic foxes in Iceland live 10-11 years)

The monitoring and research of the Actic fox populations is built on the good relationship betwen scientists and the fox hunters from across Iceland. The hunters send the fox carcasses of foxes caught from all seasons and areas of the country for dissection and age analysis. With each carcass the hunter send a form with information on the hunt type (den, running etc.) date and loction which is very important for the population monitoring to be as accurate as possible. The help and work of the Arctic fox hunters is greatly appreciated for the fox population assesments.

Reasons Arctic fox population changes can be from multiple sources, including changes in climate, food resources, animal health and pollutants. The carrying capacity of the land is unknown and variable and it may have been achieved, at least in some areas. Key factors in the population increase and decrease found is the number of animals born that live to breed along with the number of those dying before or not breeding (fertility, mortality rate and geld). This is all estimated from hunting data and the hunt within a sample submitted for analysis.

Since foxes breed once a year, living a monogamous life except as a family unit over the spring and summer months den hunting data from each area across Iceland is very important. This data can provide insight into the population density and can be used to better predict the habitat carrying capacity of each area.

According to information from fox hunters in the Southern region of Iceland there have been more geld animals observed during the summer (2014) then they are used to seeing. Den hunters from the south and northern regions have reported difficulties finding occupied den sites during the spring. In the western region of Iceland fox pups have been recorded of varying sizes which may indicate a volatile or low food supply. It is also believed that the heavy snow falls in previous winters, especially late on into the season has made it difficult for foxes to get to food. It would be interesting to get information from hunters on their experiences of den hunting during the last summer and if they have experienced anything unusual.

The sharp increase in fox population as has been mentioned in relation to increased winter time hunting which was motivated by the authorities. With this increase came an increase in the setting out of bates, excessively in some areas. A limiting factor on Arctic fox populations is exactly access to winter time food resources which is very important for fox health and spring time fertility. The increased hunting though has had no negative impact on the Arctic fox population and has not shown that in Iceland there is a direct relationship between hunting and Arctic fox population.

Monitoring of Arctic foxes has taken place on the Hornstrandir nature reserve for the last 16 summers including the monitoring of known denning sites for residency and monitoring the pups. There was a recognisable decrease in population this summer (2014) with many foxes found dead in the spring and fewer pairs pupping. This is the first time something like this has been recorded during the research period with the percentage of used dens (and therefore productive pairs) staying stable over the years. According to the hunting reports from Hornstrandir during the 1970/80´s, when the Icelandic Arctic fox population was at its lowest the situation was similar to that of 2014 where hunters were unable to “work” the dens as the females were late in giving birth if not at all with many foxes found dead in the spring. Hunting has not taking place on Hornstrandir since 1995.

From the above it is clear that the population that started in 2009 is still in process in all areas of the country where the fox is protected or not. The reasons for the rapid rate of change in Arctic fox population over the period 2004-2010 are worthy research topics that are important to look further into what changes have occurred within each region separately during this time.

 

For more information contact Ester Rut Unnsteinsdóttir

Chairman Arctic Fox Centre

Mammal researcher Icelandic Nature Institute

Phone: 5900500

Email: ester@ni.is

 

Translations from this report in Icelandic by Stephen Midgley

1 Ester Rut Unnsteinsdóttir (2014). Merkilegir melrakkar. Erindi flutt á Hrafnaþingi 30.4.2014. (ágrip á vef Náttúrufræðistofnunar Íslands).
2 Veiðiskýrslur Ragnars Jakobssonar, Jóns Oddssonar og Sigurjóns Hallgrímssoar frá 1962-1998.

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