Limits...
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.

Show MeSH

Related in: MedlinePlus

Number of reindeer in the winter herd according to yearly counts after harvest but before calving in spring from 1995 until 2012 (year referring to spring).Reindeer numbers are specified for herd A and B from 2002 and onwards, when the two herds began to be separated in winter (before this, all reindeer were kept in one large herd all year). The main owner of herd A (a young herder) built up his herd, explaining the gradual increase in the number of animals in herd A.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4214728&req=5

pone-0111509-g001: Number of reindeer in the winter herd according to yearly counts after harvest but before calving in spring from 1995 until 2012 (year referring to spring).Reindeer numbers are specified for herd A and B from 2002 and onwards, when the two herds began to be separated in winter (before this, all reindeer were kept in one large herd all year). The main owner of herd A (a young herder) built up his herd, explaining the gradual increase in the number of animals in herd A.

Mentions: Declining harvest, without any subsequent increase in herd size, was observed in Njaarke reindeer herding community in central Sweden. A closer examination of the situation revealed an inability to keep up reindeer numbers in one of two sub-herds (herd B, Fig. 1), in spite of substantially reducing animal density in winter by moving almost half of the reindeer (herd A) to new winter ranges from 2001 and onwards, and a considerable drop in harvest from 2004 and onwards.


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)

Number of reindeer in the winter herd according to yearly counts after harvest but before calving in spring from 1995 until 2012 (year referring to spring).Reindeer numbers are specified for herd A and B from 2002 and onwards, when the two herds began to be separated in winter (before this, all reindeer were kept in one large herd all year). The main owner of herd A (a young herder) built up his herd, explaining the gradual increase in the number of animals in herd A.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0111509-g001: Number of reindeer in the winter herd according to yearly counts after harvest but before calving in spring from 1995 until 2012 (year referring to spring).Reindeer numbers are specified for herd A and B from 2002 and onwards, when the two herds began to be separated in winter (before this, all reindeer were kept in one large herd all year). The main owner of herd A (a young herder) built up his herd, explaining the gradual increase in the number of animals in herd A.
Mentions: Declining harvest, without any subsequent increase in herd size, was observed in Njaarke reindeer herding community in central Sweden. A closer examination of the situation revealed an inability to keep up reindeer numbers in one of two sub-herds (herd B, Fig. 1), in spite of substantially reducing animal density in winter by moving almost half of the reindeer (herd A) to new winter ranges from 2001 and onwards, and a considerable drop in harvest from 2004 and onwards.

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