J. A.. Kitchens Maier and  R.G. White

Supporting Agencies: U.S. Air Force; U.S. Fish and Wildlife Service, The Center for Field Research and Earthwatch

Seasonal changes in caribou activity cycles were determined using captive caribou at the University of Alaska Fairbanks, Large Animal Research Station (LARS). Monthly 26 h behavioral watches were conducted on three male and three female caribou and their calves using all-occurrence sampling. Adult caribou were outfitted with Wildlink radio collars. Close concordance was noted between collar activity data and behavioral data (Fig. 10). The relation between collar activity data and behavioral data was determined using simple linear regression. Analysis of covariance was used to test for differences between individuals and months. When possible, animals were grouped and seasonal calibration curves developed. These data then were compared to Wildlink activity count data collected concurrently on wild caribou of the Delta caribou herd (DCH).

Two groups of five female DCH caribou (treatment and control) were outfitted with Wildlink radio collars in each of three seasons in 1991: late winter (March/April), post-calving (June) and insect harassment season (July/August). The groups were separated by ³ 10 km at the time of capture. Animal Noise Monitors (ANM’s) were attached to the collars of the treatment group each season and this group was subjected to low-altitude jet aircraft overflights by U.S. Air Force A-10, F-14, and F-16 jets. Activity count data were translated into number of resting and active bouts, the length of resting and active bouts and the total length of time spent resting and active each day.

Treatment and control data were compared within and between animals using one-way analysis of variance to test for effects of overflights.

The effect of photoperiod on activity cycles was investigated by comparing activity data from captive and DCH caribou (located at the same latitude) to activity data collected on arctic caribou of the Porcupine caribou herd (PCH). Specifically, in winter, onset of activity of PCH caribou was expected to occur later in the day than either DCH or LARS caribou because of the later sunrise. We predicted that LARS and DCH caribou would begin daily activity at the same time each day during winter. Circular statistics were used to describe the peak active time each day in all seasons, for LARS, DCH, and PCH caribou. We predicted highly synchronous activity within each group in winter. Caribou grazing the same pasture at LARS were highly synchronous (Fig. 11). Synchronicity should diminish as summer approaches and the cue for the onset of activity (sunrise) is lost, as seen in reindeer.