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Winter browsing by moose and hares in subarctic birch forest: Scale dependency and responses to food addition
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. (Skogen som resurs)
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Despite their difference in body size and morphology, the moose (Alces alces) andthe mountain hare (Lepus timidus) sustain themselves during winter on similar plantspecies and plant parts in in subarctic environments, namely apical twigs ofmountain birch (Betula pubescens ssp. czerepanovii). Herbivores must select areas anditems of food that provide sufficient intake rates and food nutritional quality whilebalancing this against their intake of dietary fiber and potentially detrimental plantsecondary metabolites. This selection takes place simultaneously at multiple spatialscales, from individual plants and plant parts to patches of food and parts of the wider landscape. While the herbivores must consider their need for food to sustaindaily activities, for body growth and reproduction it is also necessary to avoid predators and harsh environmental conditions. For managers, an understanding of key factors for animal foraging distributions is pivotal to reach intended goals ofmanagement and conservation plans. Knowledge in this area is also important formodels to make accurate predictions of foraging responses of herbivores to resource distributions. The mountain birch forest displays a naturally heterogeneous distribution of trees and shrubs which presents herbivores with a challenge to findgood feeding areas. In an investigation of the spatial distribution of moose browsing on birch and willows (Salix spp.) in two winter seasons separated in time by 14 years,it was found that moose browsing patterns in 1996 were correlated to those observed in 2010. It was also found that moose browsing was spatially clustered within the same distances (1000-2500 m) as densities of willow and birch, but at other spatial scales, browsing was mostly randomly distributed. It was concluded that foragedensity is a cue for moose but only at certain spatial scales. Similarly, a comparison of foraging distribution by hare and moose showed that high birch density was a key factor for both species. In spite of this, hares and moose used different parts ofthe same environment because they respond to food resource distribution at different spatial scales. Hares fed from smaller plants, and focused their foraging activity on smaller spatial scales than moose. These results emphasize the importance of taking into account the distribution of food resources at spatial scales relevant for each species in plans for conservation and management. In an experimental study it was found that intensified browsing on natural forage by mountain hares can be induced locally through placement of food. The induced browsing varied with the amount and quality of the added food, but also with thedensity of natural food plants and natural foraging distribution by hares. Finally, ina last experiment habitat preference of mountain hares across edges between open and forested areas was studied. The results were not consistent; hares utilized baitto a greater extent within forested areas than bait placed on a nearby lake ice, butbait on mires and heaths was either preferred over bait in nearby forest, or utilizedto a similar extent. A possible explanation is that hares have knowledge of their environment such that both forested areas and subarctic mires and heaths are partof its natural home range, whilst the extreme environment on the lake ice is not. During recent decades arctic areas have had an increase in vegetation density andwill be affected by future climate warming and therefore, factors that determineforaging ecology of key herbivores need to be identified. This thesis sheds some light on these factors in relation to spatial scale and forage distribution for two high profile herbivores in the subarctic.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2015. , 115 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 229
Keyword [en]
Herbivory, subarctic, hare, moose, spatial scale
National Category
Natural Sciences Biological Sciences
Identifiers
URN: urn:nbn:se:miun:diva-25865ISBN: 978-91-88025-38-8 (print)OAI: oai:DiVA.org:miun-25865DiVA: diva2:853128
Public defence
2015-10-02, O102, Mittuniversitetet, Sundsvall, 10:15
Opponent
Supervisors
Available from: 2015-09-11 Created: 2015-09-11 Last updated: 2015-10-20Bibliographically approved
List of papers
1. Distribution Of Winter Browsing By Moose: Evidence Of Long-Term Stability In Northern Sweden
Open this publication in new window or tab >>Distribution Of Winter Browsing By Moose: Evidence Of Long-Term Stability In Northern Sweden
2015 (English)In: Alces, ISSN 0835-5851, Vol. 51, 35-43 p.Article in journal (Refereed) Published
Abstract [en]

Predicting spatial distribution of large herbivore foraging is important for successfulmanagement, but accurate predictions remain elusive against a background of multiple causes modifiedby environmental stochasticity. Moose (Alces alces) might prefer to browse areas with high plant density,but if snow depth co-varies with plant density, this could restrict access to these sites and force useof sites with lower plant density and snow depth. Moose browsing was measured in 72 plots distributedwithin the subarctic birch (Betula spp.) forest landscape at Abisko in northern Sweden in 1996. In 2010,the same plots were revisited and the measurements repeated. A generalized linear model predictedmoose browsing on birch in 2010 from the browsing pattern on birch measured in 1996. The modelsuggested that neither total density of willow and birch stems nor snow depth were influential of foragingdistribution of birch at multiple spatial scales. The spatial scale at which clustering of browsing on birchoccurred, coincided with the scale of clustering of birch and willow (Salix spp.) stems at distances of1000–2500 m; at lesser distance browsing was distributed randomly. We concluded that moose demonstratestability in spatial browsing patterns after 14 years which corresponds to 3–4 generations of moose,and that plant density represents a cue for moose only at certain scales. Predictability of feeding sites isvaluable for long-term moose and forest management, and conservation planning.

Keyword
Alces alces, foraging distribution, moose, mountain birch, predictability, spatial scale, willow.
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-24962 (URN)
Available from: 2015-05-23 Created: 2015-05-23 Last updated: 2017-08-10Bibliographically approved
2. Spatially segregated foraging patterns of moose (Alces alces) and mountain hare (Lepus timidus) in a subarctic landscape: different tables in the same restaurant?
Open this publication in new window or tab >>Spatially segregated foraging patterns of moose (Alces alces) and mountain hare (Lepus timidus) in a subarctic landscape: different tables in the same restaurant?
2015 (English)In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 93, no 5, 391-396 p.Article in journal (Refereed) Published
Abstract [en]

Differences in body sizes of mountain hares (Lepus timidus L., 1758) and moose (Alces alces (L., 1758)) affect their abilityto perceive and respond to environmental heterogeneity and plant density. Therefore, we expect these species to show nicheseparation at different scales in the same environment. Results showed that the numbers of mountain birches (Betula pubescenssubsp. czerepanovii L.) browsed by moose per unit area was inversely related to hare browsing. Moose browsed larger birchescompared with hares, and while hares targeted areas with high birch densities regardless of tree sizes, moose preferentiallybrowsed areas with high densities of large birches. Moose browsing was clustered at spatial intervals of 1000–1500 m, while harebrowsing was clustered at intervals of less than 500 m. Willows (genus Salix L.) in the study area were heavily browsed by moose,while few observations of hare browsing on willow were made. Regarding both hare and moose, numbers of birch stems withnew browsing per sample plot were positively correlated with the numbers of birch stems with old browsing, indicating thathare and moose preferred the same foraging sites from year to year. These findings have implications for management of thespecies because they show the importance of scale and landscape perspectives in planning and actions.

Keyword
moose, Alces alces, mountain hare, Lepus timidus, resource use, niche separation, spatial scale.
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-24961 (URN)10.1139/cjz-2014-0332 (DOI)000354125500008 ()2-s2.0-84929087318 (Scopus ID)
Available from: 2015-05-23 Created: 2015-05-23 Last updated: 2015-09-11Bibliographically approved

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