Changes in fine-scale movement and foraging patterns of common wombats along a snow-depth gradient
Alison MatthewsSchool of Environmental Sciences, Institute for Land, Water and Society, Charles Sturt University, PO Box 789, Albury, NSW 2640, Australia. Email: almatthews@csu.edu.au
Wildlife Research 37(3) 175-182 https://doi.org/10.1071/WR09121
Submitted: 14 July 2009 Accepted: 8 February 2010 Published: 18 May 2010
Abstract
Context. Feeding strategies of large herbivores in snow-covered environments can be influenced by snow depth and snow quality. Common wombats, Vombatus ursinus, are large marsupial herbivores that occur in subalpine areas of Australia where they must dig through the snow to reach low vegetation. Deeper snow at higher elevations is considered to limit foraging and constrain their range, although there have been no quantitative studies investigating the influence of snow on their foraging behaviour.
Aims. The present study examined how snow influenced the foraging behaviour of common wombats along a snow-depth gradient.
Methods. During the 2008 winter season, snow tracks of 17 wombats were located within the subalpine zone, in a study area ranging from 1520 to 1850 m asl, and followed to record attributes of the snow cover and environment in relation to wombat activity.
Key results. Wombats selected sites to feed where the snow was shallower, and deeper snow at feeding sites caused changes in foraging behaviour. Foraging occurred along fairly direct routes between burrows; however, as snow depth increased, wombats deviated more from their path to seek out suitable foraging sites. Most foraging occurred in shallow snow in open areas or where the snow had melted around the bases of trees, shrubs or boulders. About half (52%) of the feeding sites necessitated the wombats digging through the snow to reach low vegetation, predominantly the grasses of Poa spp. Digging craters for feeding occurred in snow depths up to 100 cm, although depths less than 35 cm were preferred. Some shrub species, such as dusty daisy bush, Olearia phlogopappa, that protruded from the snow, were also eaten where the snow was deeper. Dietary analysis confirmed that monocots made up the majority of the diet (93.3%), although some individuals consumed up to 26% dicots.
Conclusions. The present study demonstrated that wombats can adjust to a snow-covered environment by altering both their foraging patterns and diet as snow depth increases. However, they will be limited where snow depths are consistently greater than 100 cm.
Implications. Under future climate-change scenarios of declining snow cover, wombats may be able to forage and inhabit higher altitudes than where they currently occur, and this has implications for the grazing-sensitive alpine ecosystem. Predicting shifts in the range of other herbivores to higher altitudes will require knowledge of their species-specific foraging thresholds in snow, such as presented in this study.
Acknowledgements
I thank Wayne Robinson for assistance with statistics, Deanna Duffy for assistance with ArcPad and spatial analyses, and Naomi Davis for conducting the dietary analyses at Melbourne University. Nick Klomp and Peter Spooner provided advice on the study design, and Peter Spooner and Ken Green provided helpful comments on the manuscript.
Bridle, K. L. , and Kirkpatrick, J. B. (2001). Impacts of grazing by vertebrate herbivores on the flower stem production of tall alpine herbs, Eastern Central Plateau, Tasmania. Australian Journal of Botany 49, 459–470.
| Crossref | GoogleScholarGoogle Scholar |
Davis, N. E. , Coulson, G. , and Forsyth, D. M. (2008). Diets of native and introduced mammalian herbivores in shrub-encroached grassy woodland, south-eastern Australia. Wildlife Research 35, 684–694.
| Crossref | GoogleScholarGoogle Scholar |
Fortin, D. (2003). Searching behavior and use of sampling information by free-ranging bison (Bos bison). Behavioral Ecology and Sociobiology 54, 194–203.
Ihl, C. , and Klein, D. R. (2001). Habitat and diet selection by muskoxen and reindeer in western Alaska. Journal of Wildlife Management 65, 964–972.
| Crossref | GoogleScholarGoogle Scholar |
Johnson, C. J. , Parker, K. L. , and Heard, D. C. (2001). Foraging across a variable landscape: behavioral decisions made by woodland caribou at multiple spatial scales. Oecologia 127, 590–602.
| Crossref | GoogleScholarGoogle Scholar |
Larter, N. C. , and Nagy, J. A. (2001). Variation between snow conditions at Peary caribou and muskox feeding sites and elsewhere in foraging habitats on Banks Island in the Canadian High Arctic. Arctic, Antarctic, and Alpine Research 33, 123–130.
| Crossref | GoogleScholarGoogle Scholar |
Norbury, G. L. (1988). Microscopic analysis of herbivore diets – a problem and a solution. Wildlife Research 15, 51–57.
| Crossref | GoogleScholarGoogle Scholar |
Rishworth, C. , McIlroy, J. C. , and Tanton, M. T. (1995). Diet of the common wombat, Vombatus ursinus, in plantations of Pinus radiata. Wildlife Research 22, 333–339.
| Crossref | GoogleScholarGoogle Scholar |
Schaefer, J. A. , and Messier, F. (1995a). Habitat selection as a hierarchy: the spatial scales of winter foraging by muskoxen. Ecography 18, 333–344.
| Crossref | GoogleScholarGoogle Scholar |
Turchin, P. (1991). Translating foraging movements in heterogeneous environments into the spatial distribution of foragers. Ecology 72, 1253–1266.
| Crossref | GoogleScholarGoogle Scholar |
