Sampling Considerations for American Black and Brown Bear Home Range and Habitat Use

• Published in: Ursus (International Association for Bear Research and Management) 2002-01, Vol.13, p.299-315
• Main Authors: Belant, Jerrold L., Follmann, Erich H.
• Format: Article
• Language: English
• Subjects: Bears; Black bears; Brown bears; Global positioning systems; Grizzly bears; Habitat selection; Habitats; Methodology; Summer; Wildlife habitats; Wildlife management
• ISSN: 1537-6176; 1938-5439

We deployed 72 collars with global positioning system (GPS) receivers on female brown bears (Ursus arctos) and American black bears (U. americanus) in southcentral Alaska during 1998-2000 to evaluate collar performance and to estimate home range and habitat use. Overall, 67% of relocation attempts were successful (range = 10-93%). Most frequent causes for unsuccessful relocation attempts were inadequate number of satellites available and GPS antenna failure. There were differences (P < 0.05) in proportion of successful relocations by time of day, with lower success during 0800-1359 and 1800-0159 h. The proportion of successful relocations also decreased (P < 0.05) across half-month intervals. Using minimum convex polygon (MCP) and fixed kernel simulations for 6 individuals of each species, we estimated that >40 locations were typically required to estimate May-September home ranges and that >40 and >50 locations were typically necessary to estimate spring (late May-Jun) and summer (Jul-late Sep) home ranges. Precision of both models increased with sample size. More locations were generally required to describe the total area used by a bear (MCP method) than the utilization distribution using the fixed kernel method. For each bear, within-year habitat use differed (P < 0.05) seasonally. Within-season habitat use differed (P < 0.05) among individuals for each species. Furthermore, diurnal (0700-1859 h) and nocturnal (1900-0659 h) seasonal habitat use differed (P < 0.05) in 13% and 42% of all cases for black and brown bears, respectively. Acquiring adequate relocations to estimate home range and habitat use with conventional VHF (very high frequency) telemetry may be prohibitive, particularly in remote areas. Potential biases from obtaining locations during only a portion of the 24-h period should also be considered. Analyses and interpretation of habitat data derived from studies with too few locations should be made with caution. Future investigators of black and brown bear home range and habitat use need to consider sampling designs seriously to ensure that data collected meets study objectives.