Winter browsing by moose and hares in subarctic birch forest : Scale dependency and responses to food addition

• Main Author: Öhmark, Sara
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Mittuniversitetet, Avdelningen för naturvetenskap 2015
• Subjects: Herbivory; subarctic; hare; moose; spatial scale; Natural Sciences; Naturvetenskap; Biological Sciences; Biologiska vetenskaper; Alces alces; Lepus timidus; mountain hare; Subarctic
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-25865

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 ...