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Power of Sign Surveys to Monitor Population Trends
Author(s) -
Kendall Katherine C.,
Metzgar Lee H.,
Patterson David A.,
Steele Brian M.
Publication year - 1992
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.2307/1941877
Subject(s) - ursus , sign (mathematics) , national park , sampling (signal processing) , geography , abundance (ecology) , statistical power , population , ecology , grizzly bears , environmental science , computer science , statistics , biology , demography , telecommunications , mathematics , mathematical analysis , sociology , detector
The urgent need for an effective monitoring scheme for grizzly bear (Ursus arctos) populations led us to investigate the effort required to detect changes in populations of low—density dispersed animals, using sign (mainly scats and tracks) they leave on trails. We surveyed trails in Glacier National Park for bear tracks and scats during five consecutive years. Using these data, we modeled the occurrence of bear sign on trails, then estimated the power of various sampling schemes. Specifically, we explored the power of bear sign surveys to detect a 20% decline in sign occurrence. Realistic sampling schemes appear feasible if the density of sign is high enough, and we provide guidelines for designs with adequate replication to monitor long—term trends of dispersed populations using sign occurrences on trails.