Winter ecology of the Porcupine caribou herd, Yukon: Part III, Role of day length in determining activity pattern and estimating percent lying

Abstract

Data on the activity pattern, proportion of time spent lying and the length of active and lying periods in winter are presented from a 3 year study on the Porcupine caribou herd. Animals were most active at sunrise and sunset resulting in from one (late fall, early and mid winter) to two (early fall and late winter) to three (spring) intervening lying periods. Mean active/lying cycle length decreased from late fall (298 mm) to early winter (238 min), increased to a peak in mid winter (340 min) then declined in late winter (305 min) and again in spring (240 min). Mean length of the lying period increased throughout the 3 winter months from 56 min m early winter to 114 min in mid winter and 153 min in late winter. The percent of the day animals spent lying decreased from fall to early winter, increased throughout the winter and declined in spring. This pattern was related, in part, to day length and was used to compare percent lying among herds. The relationship is suggested to be a means of comparing quality of winter ranges.

Twenty-four-hour feeding and lying patterns of wild reindeer Rangifer tarandus tarandus in summer

“…Though lacking nighttime observations, Skogland (1984) throughout the 24-h period, regardless of season or light conditions. In contrast, Erriksson et al (1981), Collins and Smith (1989), Roby (1978Roby ( , 1980, and Russell and Martell (1986) claimed that Rangifer feeding cycles are dominant in the diurnal phase. When we compare activity rhythms for caribou (Maier and White 1998), Svalbard reindeer (Kastnes 1979), semidomestic reindeer introduced into Alaska (Collins and Smith 1989), semidomestic reindeer in Sweden (Erriksson et al 1981) and Finland (Erkinaro et al 1983), wild forest reindeer (Rangifer tarandus fennicus) in Finland (Erkinaro et al 1983), and wild mountain reindeer in Norway (Thomson 1973;Skogland 1984; this study) with those from other northern temperate species such as domestic sheep (Ovis aries) in Norway (Colman et al Submitted), roe deer (Capreolus capreolus) in Sweden (Cederlund 1981), and white-tailed deer (Odocoileus virginianus) in North America (Montgomery 1963), we conclude that, in lacking a crepuscular pattern, Rangifer spp.…”

“…Earlier reports on the influence of external stimuli on activity patterns for ungulates such as reindeer neglected to consider the possibility that feeding and lying rhythms could be influenced differently by disturbances and respond independently of one another. Based on the assumption that the amount of time spent lying is dependent solely on factors associated with rumination, such as forage quality, some studies (Roby 1978(Roby , 1980Russell and Martell 1986) of the activity patterns of Rangifer spp. focused on the percentage of time spent lying and were conducted primarily to assess and compare range quality among populations.…”

“…The need for, but lack of, such information has been stressed repeatedly in the literature (Thomson 1973, 1977, Skogland 1984Downes et al 1986;Mörschel and Klein 1997;Colman 2000). Thus, contrary to their claims (Roby 1978(Roby , 1980Erriksson et al 1981;Russell and Martell 1986;Collins and Smith 1989), few studies have managed to isolate and separately test the effects of environmental stimuli like sunrise, sunset, or insect harassment on the activity patterns of Rangifer spp.…”

“…Segal (1962) observed that year-round lengths of active-resting cycles of penned reindeer in northern Russia were relatively constant over 24-h periods. Since then, it has been concluded from numerous studies that reindeer activity patterns have common features that are independent of season, such as activity bouts synchronized with sunrise and sunset, lying or feeding activities occurring daily at the same time, feeding and lying cycles contingent on each other, and predominance of the diurnal activity phase over the nocturnal phase (Roby 1978(Roby , 1980Erriksson et al 1981;Russell and Martell 1986;Collins and Smith 1989). In contrast to this, Maier and White (1998) found that caribou (Rangifer tarandus granti) were nychthemeral, i.e., they exhibited equal proportions of feeding and lying during daytime and nighttime, and their active cycle was not attuned to sunrise.…”

Twenty-four-hour feeding and lying patterns of wild reindeer <i>Rangifer tarandus tarandus</i> in summer

“…are essentially diurnal animals that attune their feeding rhythm to the set points of sunrise and sunset (crepuscular), and that their total amount of activity over 24-h periods is controlled by photoperiod (Roby 1978(Roby , 1980Erriksson et al 1981;Russell and Martell 1986;Smith and Collins 1989). However, like Maier and White (1998) we found no effect of sunrise on activity patterns.…”