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Daily Departure and Return Patterns of Wolves,
Canis lupus, from a Den at 80° N Latitude

Main Article


The senior author and various assistants observed the Ellesmere Wolves around their den during varying periods between 21 June and 4 August 1988, 1990, 1991, 1994, and 1996 and recorded times of departure from, and returns to, the den for the adult Wolves (including yearlings). We made the observations from distances of 1-100 m away and usually continued to watch the Wolves travel until out of sight at least 1 km away and/or we remained observing the den for at least an hour after departures. Further, we did not count data from excursions known to be food-transport trips from kills < 5 km away because such trips represented exceptions to the usual daily hunting routine. That is, when a large kill was nearby, the wolves concentrated on making a series of food-transport trips rather than a single long hunting trip. Thus all departures that we included represented daily foraging trips rather than local exploratory jaunts or food-transport trips.

From data forms we tabulated and summed group and individual departures and returns for each hour of the day, and we pooled the data from all years for each hour. Thus we gave group and individual departures the same weight. We adjusted departure and return data for hours of observation by summing the number of days each year the den was observed at each hour, and multiplying the number of observed departures and returns per hour by 1/this number. For example, if four departures were recorded between all 2000-2100-h periods in a given year, and we observed during this period 20 times that year, the adjusted value was 4/20 = 0.2.

We then pooled adjusted departures and returns for the five observation years and tested them by ANOVA against the following 6-h periods: 2200-0359, 0400-0959, 1000-1559, and 1600-2159 h to test the hypothesis that Wolves leave their den late in the day and return to their den at random times. We chose these periods because field observations suggested that this manner of pooling hours would be most likely to detect differences in times of Wolf departures and returns. ANOVA models were checked for normality of residuals.

We recorded observations of Wolf departure and return rates for 1759 hours (mean = 293 per summer) over 153 days (mean = 31 per summer) during the five summers of the study. Six different Wolves were involved, two of which were present for all five summers; one female was a non-breeder during one of those years and a breeder during the remaining four, and one was a breeder during 1 year and non-breeder during her remaining 2 years (Mech 1995 and unpublished).

We observed significantly fewer group and individual departures (180) than group and individual returns (230) (t test, P <0.001). As members of groups split up while foraging, individuals then tended to return separately, thus resulting in the greater number of returns.

The Wolves departed from the den area at all times of day, but like Wolves at lower latitudes, they tended to leave dens on foraging trips more often during late evening and early morning, starting about 2200 h (Figure 1). They left least frequently on average from 1600-2200 h. This pattern differs significantly from random (F3,20 = 3.95, P = 0.02). The Wolves tended to return to the den least often during 1600 to 2000 h (Figure 2).
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Figure 1. Ratio of times Wolves left Ellesmere Island den area each hour divided by number of times observations were made for each hour, based on five summers. Figure 2. Ratio of times Wolves returned to Ellesmere Island den area each hour divided by number of times observations were made for each hour, based on five summers.

Kolenosky and Johnston (1967) found that one of two peak den-leaving periods for Wolves at 46° N began around 2100 h. At 64° N, Wolves left dens between 1600 and 2200 h (Murie 1944), and starting around 2200 h (Haber 1977). Ballard et al. (1991) reported Wolf departures at 63° N most frequent from 2100 to 2400 h (27% of 191 observations) and least frequent from 1300 to 2100 h, as we did. In Spain, at about 42° N, general Wolf activity and activity around dens peaked at about 2100 h and 0500 h (Vila and Castroviejo 1995). Presumably it is this basic circadian activity pattern (Folk 1964) that leads to Wolves departing from the den during evening.

In a Minnesota study (48° N) involving two dens, Wolves did not tend to leave the den area more during late evening but rather left most often around dawn (Harrington and Mech 1982). These contrasting results are puzzling, especially in view of the Ontario study at about the same latitude and the same type of forested habitat (Kolenosky and Johnston 1967).

In any case, our study indicates that regardless of latitude and amount of sun each day, Wolves tend to depart from dens at about the same time daily. Contrary to the Wolves in previous studies, our Wolves could not have obtained temporal cues from darkness, for there was no darkness in our area during the study or for many weeks before. The sun does dip toward the north at midnight and reaches its zenith in the south around midday, so we suggest that our Wolves might be gaining their temporal cues from sun position, as Folk (1964) also suggested.


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