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High female mortality resulting in herd collapse in free-ranging domesticated reindeer (Rangifer tarandus tarandus) in Sweden.

Åhman B, Svensson K, Rönnegård L - PLoS ONE (2014)

Bottom Line: Lower calving success in herd B compared to A indicated differences in winter foraging conditions.We found no evidence that a lower autumn body mass generally increased the risk for a female of dying from one autumn to the next.We conclude that the prime driver of the on-going collapse of herd B is not high animal density or poor body condition.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden.

ABSTRACT
Reindeer herding in Sweden is a form of pastoralism practised by the indigenous Sámi population. The economy is mainly based on meat production. Herd size is generally regulated by harvest in order not to overuse grazing ranges and keep a productive herd. Nonetheless, herd growth and room for harvest is currently small in many areas. Negative herd growth and low harvest rate were observed in one of two herds in a reindeer herding community in Central Sweden. The herds (A and B) used the same ranges from April until the autumn gathering in October-December, but were separated on different ranges over winter. Analyses of capture-recapture for 723 adult female reindeer over five years (2007-2012) revealed high annual losses (7.1% and 18.4%, for herd A and B respectively). A continuing decline in the total reindeer number in herd B demonstrated an inability to maintain the herd size in spite of a very small harvest. An estimated breakpoint for when herd size cannot be kept stable confirmed that the observed female mortality rate in herd B represented a state of herd collapse. Lower calving success in herd B compared to A indicated differences in winter foraging conditions. However, we found only minor differences in animal body condition between the herds in autumn. We found no evidence that a lower autumn body mass generally increased the risk for a female of dying from one autumn to the next. We conclude that the prime driver of the on-going collapse of herd B is not high animal density or poor body condition. Accidents or disease seem unlikely as major causes of mortality. Predation, primarily by lynx and wolverine, appears to be the most plausible reason for the high female mortality and state of collapse in the studied reindeer herding community.

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Related in: MedlinePlus

Map of study area with spring-summer-autumn ranges for the whole herding community and winter ranges for the two herds, and showing the main locations for reindeer gathering.
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pone-0111509-g002: Map of study area with spring-summer-autumn ranges for the whole herding community and winter ranges for the two herds, and showing the main locations for reindeer gathering.

Mentions: The investigated reindeer were all privately owned. Access to the animals and the area was provided by Njaarke reindeer herding community (indicated in Fig. 2). All fieldwork was made at facilities belonging to the herding community and in connection to routine handling of the animals. The only extra handling procedures, due to the research, was marking (using numbered collars on females and ear-tags on calves) and weighing of females and calves. This was approved and made in cooperation with the owners of the animals. No animals were sacrificed due to the project. The experimental design and handling of animals were approved by Umeå Ethical Committee for Animal Research (application A 35-07, A 76-10 and A 24-12). Official data on reindeer numbers and reindeer slaughter records was provided by the Sámi Parliament in Sweden (according to permission 2007-505). The use of herd-specific data was approved by the reindeer herding community (contact information is available at http://sametinget.se/8812).


High female mortality resulting in herd collapse in free-ranging domesticated reindeer (Rangifer tarandus tarandus) in Sweden.

Åhman B, Svensson K, Rönnegård L - PLoS ONE (2014)

Map of study area with spring-summer-autumn ranges for the whole herding community and winter ranges for the two herds, and showing the main locations for reindeer gathering.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214728&req=5

pone-0111509-g002: Map of study area with spring-summer-autumn ranges for the whole herding community and winter ranges for the two herds, and showing the main locations for reindeer gathering.
Mentions: The investigated reindeer were all privately owned. Access to the animals and the area was provided by Njaarke reindeer herding community (indicated in Fig. 2). All fieldwork was made at facilities belonging to the herding community and in connection to routine handling of the animals. The only extra handling procedures, due to the research, was marking (using numbered collars on females and ear-tags on calves) and weighing of females and calves. This was approved and made in cooperation with the owners of the animals. No animals were sacrificed due to the project. The experimental design and handling of animals were approved by Umeå Ethical Committee for Animal Research (application A 35-07, A 76-10 and A 24-12). Official data on reindeer numbers and reindeer slaughter records was provided by the Sámi Parliament in Sweden (according to permission 2007-505). The use of herd-specific data was approved by the reindeer herding community (contact information is available at http://sametinget.se/8812).

Bottom Line: Lower calving success in herd B compared to A indicated differences in winter foraging conditions.We found no evidence that a lower autumn body mass generally increased the risk for a female of dying from one autumn to the next.We conclude that the prime driver of the on-going collapse of herd B is not high animal density or poor body condition.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden.

ABSTRACT
Reindeer herding in Sweden is a form of pastoralism practised by the indigenous Sámi population. The economy is mainly based on meat production. Herd size is generally regulated by harvest in order not to overuse grazing ranges and keep a productive herd. Nonetheless, herd growth and room for harvest is currently small in many areas. Negative herd growth and low harvest rate were observed in one of two herds in a reindeer herding community in Central Sweden. The herds (A and B) used the same ranges from April until the autumn gathering in October-December, but were separated on different ranges over winter. Analyses of capture-recapture for 723 adult female reindeer over five years (2007-2012) revealed high annual losses (7.1% and 18.4%, for herd A and B respectively). A continuing decline in the total reindeer number in herd B demonstrated an inability to maintain the herd size in spite of a very small harvest. An estimated breakpoint for when herd size cannot be kept stable confirmed that the observed female mortality rate in herd B represented a state of herd collapse. Lower calving success in herd B compared to A indicated differences in winter foraging conditions. However, we found only minor differences in animal body condition between the herds in autumn. We found no evidence that a lower autumn body mass generally increased the risk for a female of dying from one autumn to the next. We conclude that the prime driver of the on-going collapse of herd B is not high animal density or poor body condition. Accidents or disease seem unlikely as major causes of mortality. Predation, primarily by lynx and wolverine, appears to be the most plausible reason for the high female mortality and state of collapse in the studied reindeer herding community.

Show MeSH
Related in: MedlinePlus