Performance of Spread Spectrum Global Positioning System Collars on Grizzly and Black Bears

Abstract

Global Positioning System (GPS) telemetry is a prevalent tool now used in the study of large mammals. Global Positioning Systems either store the data on board the collar or contain a remote‐transfer system that allows for data recovery at more frequent intervals. Spread spectrum (S‐S) technology is a new mode of data transfer designed to overcome interference problems associated with narrow‐band very high frequency and ultra high frequency data‐transfer systems. We evaluated performance of S‐S GPS radiocollars deployed on grizzly (Ursus arctos) and black bears (U. americanus). We also evaluated variables that influenced GPS fix success rates, with particular focus on animal activity, time of year, and temperature. The S‐S GPS collars performed to our expectations and met study objectives; we did not experience any major problems with the data‐transfer system. We observed varying rates of fix success that were directly related to recorded activity counts. Using logistic regression, we verified that activity counts were a reasonable measure of resting or feeding‐traveling in both bear species. Our results showed that 73% and 79% of missed fixes, respectively, occurred when we predicted black and grizzly bears to be resting. Temperatures measured in the canister of the collar were not correlated with air temperature, suggesting posture and activity influenced canister temperature. Both measures of temperature were predictive of fix success. We did not find that fix success was related to body morphology (i.e., neck circumference, mass, and chest girth), fix interval, position of the GPS antenna relative to the sky, or sex of the bear. We conclude that fix success for both species is strongly related to activity patterns and time of year. Activity counters appear to be a reasonable measure of this behavior, and we recommend researchers consider including an activity‐count system when deploying GPS collars. We also recommend researchers explore building separate models of habitat selection based upon categories of activity to account for bias in fix success associated with bear behavior.

Temporal niche switching by grizzly bears but not American black bears in Yellowstone National Park

“…1). In contrast, sympatric black bears remained TABLE 1.-Percentage (6 SD) of available hours used by male black bears (Ursus americanus) and female and male grizzly bears (Ursus arctos) during daylight, twilight, and nighttime in Yellowstone National Park, Wyoming (2007-2009. Male black bears, female grizzly bears, and male grizzly bears all differed significantly from each other in the percentage of both nighttime and daytime hours used.…”

“…We used the telemetry system described and evaluated by Schwartz et al (2009). We fitted all bears, except dependent young, with Telonics Global Positioning System (GPS) Spread Spectrum collars (Telonics, Inc., Mesa, Arizona) programmed to attempt a GPS fix either every 30 min (1 male black bear, 1 female grizzly bear, and 4 male grizzly bears), 60 min (3 male black bears, 10 female grizzly bears, and 8 male grizzly bears), or 120 min (3 male black bears and 1 female grizzly bear).…”

“…We fitted all bears, except dependent young, with Telonics Global Positioning System (GPS) Spread Spectrum collars (Telonics, Inc., Mesa, Arizona) programmed to attempt a GPS fix either every 30 min (1 male black bear, 1 female grizzly bear, and 4 male grizzly bears), 60 min (3 male black bears, 10 female grizzly bears, and 8 male grizzly bears), or 120 min (3 male black bears and 1 female grizzly bear). We excluded collars that malfunctioned due to antenna fatigue (Schwartz et al 2009) when we calculated fix success. We programmed units to shut off during the expected denning season (15 November-14 April for grizzly bears and 31 October-14 April for black bears).…”

“…We used a generalized linear model with consideration for correlation of individual bear activities (PROC GENMOD with GEE-SAS Institute Inc. 2002). Activity was the dependent variable (resting ¼ 0, active ¼ 1) and the predictor variable was the activity count (Schwartz et al 2009). Each bear was classified as front country or back country based on whether the majority (80%) of their home range did or did not overlap with human developments (as defined by Yellowstone National Park's Bear Management Office) and roads (K. Gunther, Yellowstone National Park, pers.…”

“…-Actogram examples for A) male black bears (Ursus americanus), B) female grizzly bears (Ursus arctos), and C) male grizzly bears in Yellowstone NationalPark, Wyoming (2007-2009, with activity for each hour plotted on a single line and each line consisting of 2 consecutive days. Although the black bear is clearly diurnal for the entire active season, both female and male grizzly bears shift from nocturnal in the early spring and summer to crepuscular and diurnal in the late summer and fall.…”