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| Pirece, B.M.; Bleich, V.C. | |
| Enumerating mountain lions: a comparison of two indices | |
| 2014 California Fish and Game (100): 527-537 | |
Assessing mountain lion (_Puma concolor_) populations is difficult due to their inherently low densities, secretive nature, and a near absence of demographically closed populations. We developed and compared two methods of indexing the number of mountain lions within a subset (referred to in this paper as the core area) of a total study area. The study area was defined as the outer boundary of combined home range polygons for all collared mountain lions. Therefore, the study area was regularly occupied by uncollared individuals whose home ranges overlapped the study area boundary. We determined through intensive capture efforts and monitoring that the much smaller core area was used only by adult mountain lions that we had identified and collared and was not used in any significant manner by uncollared adults. We derived two indices to the number of lions using the core area. One index is based on location data from VHF aerial telemetry ("fixed wing index"); the second index is based on a combination of fixed wing locations and GPS collar data combined ("location data index"). The fixed wing index yields the mean number (and variance) of adult individuals located in the core region of the study area each of 15 winters during weekly telemetry flights. The location data index is based on the sum of the proportions of locations for each individual that are within the core area each winter. The two indices were highly correlated, and the trends generally were in the same direction and changes in each were of a similar magnitude. These methods are preferable to attempting total counts because the periphery of any study area will occasionally be occupied by unmarked animals. Our methods account for those individuals, but they are not afforded the same weight as mountain lions that use the area frequently or exclusively. Managers with GPS radio collar data are encouraged to delineate a core area, where all lions known to use the area are collared, and use the sum of the proportion of locations from each individual in that area to index density, population size, number of animals present, or use. |
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