Masters Thesis

Mark-recapture for estimation of Roosevelt elk numbers at Big Lagoon, Humboldt County, California

Methods for estimating numbers, relative densities, home range and group dynamics of Roosevelt elk (Cervus elaphus roosevelti) were studied near Big Lagoon, Humboldt County, California from 1 July 1985 to 30 June 1987. An aerial mark-recapture model was used to estimate the number of elk groups; groups with telemetry-equipped members were considered as marked and groups without telemetry-equipped members were unmarked. The average group size per survey was multiplied by the estimated number of groups to yield an estimate of elk numbers. Thirteen aerial surveys were conducted within a 10 km2 area where a mark-recapture census model was applicable. Eight surveys, where four or more marked elk groups were available, provided an estimate of 140.6 (95% CI = 68.7 -212.5) elk for an approximate 10 km2 area. The precision of the abundance estimate may be acceptable where other methods provide less reliable estimates and indicated the necessity for averaging results from repetitive surveys. The relationship between group size and density in elk was examined within a 23 km2 area to determine the feasability of using group size as an indicator of relative density. Average elk group size decreased as distance increased from a point of greatest elk density, which indicated group size as a possible indicator of relative density.

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