A practical method for measuring horizontal cover
Abstract: We propose a new cover cylinder as a useful tool for a single observer to measure horizontal cover in the field. We compared it with 4 other methods for measuring horizontal cover at brown bear (Ursus arctos) beds, with all measurements taken 10 m from beds in the 4 cardinal directions. We...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1082.4998 http://bearproject.info/old/uploads/publications/2009%20Ordiz_et_al_Cover%20measurement%20Ursus.pdf |
| Summary: | Abstract: We propose a new cover cylinder as a useful tool for a single observer to measure horizontal cover in the field. We compared it with 4 other methods for measuring horizontal cover at brown bear (Ursus arctos) beds, with all measurements taken 10 m from beds in the 4 cardinal directions. We also compared cylinder cover values from a fixed distance with an index of cover, namely a sighting distance, D, the minimum distance at which the cylinder could no longer be seen; we also compared measurements from a random direction and from the 4 cardinal directions. The cylinder provided measurements comparable to other devices, including a cardboard profile of a bedded bear, and was the most practical to use in the field. Measuring D was scarcely more time consuming than measuring cover from the fixed 10-m distance, and D is better for statistical analysis. We recommend the cylinder, and using the index of cover, D, taken from the 4 cardinal directions, when assessing horizontal cover for bears or other medium and large terrestrial vertebrates. Key words: bears, cover cylinder, horizontal cover, sighting distance, Sweden, Ursus arctos Cover, a habitat element that conceals, shelters, or protects, is important for animals; it can protect against weather and lower the risk of predation Methods Study area The study took place in 2007 in Sweden, near the southernmost distribution of the Scandinavian brown bear population (61uN, 15uE). The area was 80% covered with highly managed forest, mainly composed of Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and birch (Betula spp.). The understory vegetation was dominated by heathers (Calluna vulgaris), grasses, and berries (Vaccinium 6 andres.ordiz@umb.no 109 |
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