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To survive and reproduce in a cyclic environment – demography and conservation of the Arctic fox in Scandinavia
Stockholm University, Faculty of Science, Department of Zoology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the conservation and life history of the Arctic fox (Vulpes lagopus) in Scandinavia. The Arctic fox was historically a widely distributed species in the Scandinavian mountain tundra with a population size of approximately 10 000 individuals during years with high resource availability, i.e. rodent peaks. However, due to over-harvest in the end of the 19th century, the population numbers declined to a few hundred individuals. Although legally protected for more than 80 years, the population has remained small. The main causes of the non-recovery have been attributed to irregularities in the lemming cycle and increased competitions with the larger red fox. 

Through conservation actions including red fox culling and supplementary feeding, the population has started to recover in parts of its former distribution range. The Arctic fox is highly adapted to the lemming cycle and determine whether to reproduce or not and adjust the litter size relation to small rodent phase in combination with food abundance. In the small rodent increase phase, females produce litters equal to the peak phase, despite higher food abundance in the later. This overproduction of cubs can be selected for through a higher juvenile survival and reproductive value of cubs born in the increase phase compared to the other phases. The most important component affecting the reproductive value seem to be the survival during the first year after birth. In the small rodent increase phase 32% of the cubs survives their first year compared to 9% in the decrease phase. The Arctic fox in Scandinavia constitute an example of how a species can adapt their reproductive strategy to a fluctuating environment by adjustment of the reproduction.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University , 2013. , 31 p.
Keyword [en]
Conservation, life-history, Alopex lagopus, survival
National Category
Zoology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-87404ISBN: 978-91-7447-647-7 (print)OAI: oai:DiVA.org:su-87404DiVA: diva2:606758
Public defence
2013-04-12, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 4: Accepted manuscript; Paper 5: Manuscript.

Available from: 2013-03-21 Created: 2013-02-05 Last updated: 2013-03-04Bibliographically approved
List of papers
1. Carnivore conservation in practice: replicatedmanagement actions on a large spatial scale
Open this publication in new window or tab >>Carnivore conservation in practice: replicatedmanagement actions on a large spatial scale
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2013 (English)In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 50, no 1, 59-67 p.Article in journal (Refereed) Published
Abstract [en]

More than a quarter of the world’s carnivores are threatened, often due to multiple andcomplex causes. Considerable research efforts are devoted to resolving the mechanisms behindthese threats in order to provide a basis for relevant conservation actions. However, evenwhen the underlying mechanisms are known, specific actions aimed at direct support for carnivoresare difficult to implement and evaluate at efficient spatial and temporal scales.2. We report on a 30-year inventory of the critically endangered Fennoscandian arctic foxVulpes lagopus L., including yearly surveys of 600 fox dens covering 21 000 km2. These surveysshowed that the population was close to extinction in 2000, with 40–60 adult animalsleft. However, the population subsequently showed a fourfold increase in size.3. During this time period, conservation actions through supplementary feeding and predatorremoval were implemented in several regions across Scandinavia, encompassing 79% of thearea. To evaluate these actions, we examined the effect of supplemental winter feeding andred fox control applied at different intensities in 10 regions. A path analysis indicated that47% of the explained variation in population productivity could be attributed to lemmingabundance, whereas winter feeding had a 29% effect and red fox control a 20% effect.4. This confirms that arctic foxes are highly dependent on lemming population fluctuationsbut also shows that red foxes severely impact the viability of arctic foxes. This study also highlightsthe importance of implementing conservation actions on extensive spatial and temporalscales, with geographically dispersed actions to scientifically evaluate the effects. We note thatpopulation recovery was only seen in regions with a high intensity of management actions.5. Synthesis and applications. The present study demonstrates that carnivore populationdeclines may be reversed through extensive actions that target specific threats. Fennoscandianarctic fox is still endangered, due to low population connectivity and expected climate impactson the distribution and dynamics of lemmings and red foxes. Climate warming is expected tocontribute to both more irregular lemming dynamics and red fox appearance in tundra areas;however, the effects of climate change can be mitigated through intensive managementactions such as supplemental feeding and red fox control.

Keyword
Alopex, arctic, climate, extinction, population cycles, restoration, SEFALO, Vulpes
National Category
Biological Sciences
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-87916 (URN)10.1111/1365-2664.12033 (DOI)000314520500008 ()
Available from: 2013-02-25 Created: 2013-02-25 Last updated: 2017-12-06Bibliographically approved
2. Estimating population parameters in a threatened arctic fox population using molecular tracking and traditional field methods
Open this publication in new window or tab >>Estimating population parameters in a threatened arctic fox population using molecular tracking and traditional field methods
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2008 (English)In: Animal Conservation, ISSN 1469-1795, Vol. 11, no 4, 330-338 p.Article in journal (Refereed) Published
Abstract [en]

Comprehensive population parameter data are useful for assessing effective conservation actions. The Fennoscandian arctic fox Alopex lagopus is critically endangered and the population size is estimated at 120 individuals that are fragmented into four isolated populations. Here, we use molecular tracking and visual observations to estimate population size and survival in one of the populations on the Swedish mountain tundra during a year of low food availability. We collected 98 arctic fox faecal samples during the winter of 2006 and recorded visual observations of ear-tagged individuals during the summer of 2005 and 2006. The faecal samples were analysed for variation in nine microsatellite loci and matched to the genetic profiles of previously ear-tagged individuals from 2001 to 2005. During winter 2006, the minimum number alive was 12 individuals using visual observations, 30 using molecular tracking and 36 by combining the datasets. Population size was estimated through mark–recapture for the molecular tracking and visual observation datasets and through rarefaction analyses for molecular tracking data. The mark–recapture estimate for visual observations was uninformative due to the large confidence interval (CI) (i.e. 6–212 individuals). Based on the molecular tracking dataset combined with the minimum number alive for visual observations and molecular tracking, we concluded a consensus population size of 36–55 individuals. We also estimated the age-specific finite survival rate during 1 year (July 2005 to July 2006) by combining molecular tracking with visual observations. Juvenile survival on a yearly basis was 0.08 (95% CI 0.02–0.18) while adults had a survival of 0.59 (95% CI 0.39–0.82). Juveniles displayed a lower survival than the adults during autumn (P<0.01) whereas no age-specific survival difference during spring was found. The risk of negative effects due to the small population size and low juvenile survival is accordingly considerable.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2008
Keyword
Alopex lagopus, management, molecular tracking, mark–recapture, rarefaction, survival, conservation
National Category
Zoology
Identifiers
urn:nbn:se:su:diva-14284 (URN)10.1111/j.1469-1795.2008.00188.x (DOI)000257987100013 ()
Available from: 2008-08-14 Created: 2008-08-14 Last updated: 2017-03-22
3. The impact of maternal experience on post-weaning survival in an endangered arctic fox population
Open this publication in new window or tab >>The impact of maternal experience on post-weaning survival in an endangered arctic fox population
2011 (English)In: European Journal of Wildlife Research, ISSN 1612-4642, E-ISSN 1439-0574, Vol. 57, no 3, 549-553 p.Article in journal (Refereed) Published
Abstract [en]

Behavioural differences in parental care can influence offspring survival through variation in e.g. antipredator behaviour and ability to provide food. In a broad range of species, offspring survival has been found to be higher for experienced females compared to inexperienced first-time breeders. The increase in offspring survival for experienced females has mainly been explained by improved experience in providing food. In this paper, we have studied post-weaning juvenile survival in relation to maternal experience in an endangered population of arctic foxes (Vulpes lagopus) in Fennoscandia. For cubs raised by inexperienced and experienced females, the survival rate was 0.42 (CI 95% +/- 0.31) and 0.87 (CI 95% +/- 0.08), respectively. There was no difference in body condition between the cubs and no observations of starvation. We suggest that the difference in survival was due to lack of experience to one of the most common predators, the golden eagle (Aquila chrysaetos). Golden eagles were mainly observed on dens with litters where the females were inexperienced first-time breeders. From a conservation perspective, it is therefore important to increase adult survival through actions to enlarge the proportion of experienced breeders.

Keyword
Alopex lagopus, Conservation, Aquila chrysaetos, Parental experience, Population dynamics, Body index, Juvenile survival
National Category
Zoology
Identifiers
urn:nbn:se:su:diva-67848 (URN)10.1007/s10344-010-0463-0 (DOI)000290771400017 ()
Note

authorCount :3

Available from: 2012-01-02 Created: 2012-01-02 Last updated: 2017-12-08
4. Life history traits in a cyclic ecosystem– a field experiment on the arctic fox
Open this publication in new window or tab >>Life history traits in a cyclic ecosystem– a field experiment on the arctic fox
(English)Manuscript (preprint) (Other academic)
National Category
Biological Sciences
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-87914 (URN)
Available from: 2013-02-25 Created: 2013-02-25 Last updated: 2014-10-13Bibliographically approved
5. Reproductive strategy in a cyclic environment
Open this publication in new window or tab >>Reproductive strategy in a cyclic environment
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The ability to maximize life-time reproductive output in relation to ecological variation in time and space is central for individual fitness. In cyclic environments the optimal litter size might vary over time depending on fluctuations in food abundance, offspring survival and their future fecundity. The arctic fox in Scandinavia is highly dependent on cyclic small rodents, such as lemmings and voles, for its reproduction. The arctic foxes can adjust their litter size in relation to small rodent phase, but this adjustment cannot be explained by food abundance only. In the rodent increase phase, litters are larger than expected from food abundance, while litters are smaller than expected in the decrease phase. In this paper, we studied how arctic fox litter size is associated with variation in the offspring reproductive value, specifically if the reproductive value is higher in the increase phase of the small rodent cycle. We followed the survival and fecundity, i.e. number of offspring, of 282 ear-tagged arctic foxes for a minimum of 4 years after birth in relation to small rodent phase. We found substantial variation in reproductive values, with a 3.2 times higher reproductive value for cubs born in the increase phase (0.74) compared to the decrease phase (0.23). The most pronounced difference in reproductive value between offspring born in different phases was caused by survival from birth to the end of their first year. Of the offspring born in the increase phase, 32% survived their first year compared to only 9% in the decrease phase. Our data supports that the observed phase dependent adjustment of arctic fox litter size has a demographic (and thereby an evolutionary) advantage by maximizing the number of offspring when the reproductive value is highest.

National Category
Biological Sciences
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-87915 (URN)
Available from: 2013-02-25 Created: 2013-02-25 Last updated: 2014-10-13Bibliographically approved

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