A practical method for measuring horizontal cover

Abstract

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.