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The Usefulness of GPS Telemetry to Study Wolf Circadian and Social Activity

Results


We obtained location data from 9 wolves of both genders and various ages and reproductive status during periods of 2-24 weeks, primarily during later winter, spring, and early summer (Table 1).

Except for one wolf traveling on an extraterritorial foray, all circadian movement patterns were nocturnal (Figure 1). Generally, wolves were more active from about 2000 hours to about 0800 hours, but there was no consistent sharp break in activity during night and day. Rather, activity tended to increase at 2000 hours and taper at 0800 hours (Figure 1). All 4 wolves with GPS collars programmed for intervals ≤1 hour showed standardized hourly movement peaks at dawn, dusk, and in the middle of the night. Mean minimum rates of travel per GPS interval varied from 269 m per hour for wolf 860 to 716 m per hour for wolf 820 after denning (Table 2). For the 2 breeding male wolves, straight line distances per 3 hour were apparent between winter and summer for several 3-hour periods (Figure le and g).

Table 2.  Location attempt intervals and mean and maximum travel rates for wolves studied by Global Positioning System telemetry near Little Falls, Minnesota, from 20 February 1997-14 September 1998.
Wolf Location attempt interval Max. Distance per location interval (m) Travel rate (m/interval) Standardized travel rate (m/h)
850
   Before denning 1 hr 7,344 583 583
   During denning 4 hr 9,370 1,423 356
   After denning 4 hr 9,722 2,580 645
840 30 min 4,532 330 660
860 1 hr 2,983 269 269
820 15 min 3,660 179 716
133 3 hr 12,669 1,844 615
229 3 hr 10,906 1,198 399
627 3 hr 8,335 1,289 430
134 3 hr 6,725 1,229 410

Male wolf 399

Wolf 399 conducted an extraterritorial foray 185 km (Merrill and Mech 2000) from his natal territory on 31 May 1998 and returned on 27 July 1998 (Figure 2; if he had not returned to his natal territory, it would have been a dispersal). Distances spanning 3 hours indicated that he traveled an average of 1,179 m per 3 hours prior to the foray and 1,055 m per 3 hours during the foray. The fastest rate of travel recorded before the foray was 10,439 m per 3 hours, and the fastest rate during the foray was 10,642 m per 3 hours. The wolf shifted his circadian movement pattern from nocturnal to diurnal during the foray (Figure 3a).

In the month before the foray, wolf 399 made at least 13 trips to and from the den site (Figure 4), at a rate of roughly one trip per 2 days. The longest duration of trips from the den during this period was 2.5 days, except for one absence that apparently lasted from 15-23 May 1998. The last recorded trip to the den area was on 24 May, one week prior to the foray.

Breeding female wolf 850 before and after whelping

We outfitted this wolf with a GPS collar twice (Table 1). Data from the first collar described the wolf's movements for 3 weeks before denning (327 locations, once per hour from 20 February 9-March 1997; Figure 5), and data from the second collar (254 locations once per 4 hour from 10 April 9-July 1997; Figure 6) recorded movement after denning (based on time of year and presence of only 2 of 76 GPS locations >1.5 km from the den during 11-30 April 1997). Prior to wolf 850's whelping, GPS data collected once per hour show that she moved at night with increases at dusk, dawn, and midnight (Figures 1a and 3b). Her mean minimum rate of travel was 583±475 m per hour (Table 2). After converting data from one location per hour to one per 4 hours (to compare fairly with data collected after she whelped), her mean minimum distance traveled before whelping was 1,889±1,334 m per 4 hours. The observed nocturnal pattern was not altered by this conversion, although the peaks at dusk and dawn were lost. After whelping, 850's mean minimum distance traveled per 4 hours was 2,026±1,051 m.

From 1 to 25 May 1997, wolf 850's amount of time >1.5 km from the den increased from 3 (2/76 locations) to 39% (25/64 locations). During this period she took 20 trips from the den, at one trip per 1.25 days. Of these trips 17 were represented by single GPS locations, 2 by 2 consecutive GPS locations, and one by 3 consecutive GPS locations. This pattern suggested that wolf 850's trips generally lasted <8 hours (the time spanned by 3 consecutive GPS locations). Most locations >1.5 km from the den were nocturnal (Figure 7), as would be expected based on the wolf's nocturnal pattern for distance traveled. We avoided bias in this estimate of temporal distribution of trips away from the den by including only one location for each trip. About 4 June, 850 moved her pups to rendezvous sites (Figure 6, "Locations from 0-6 weeks after pups").

Social activities of pack members during late winter

We analyzed a subset of GPS data from wolves 820, 840, 850, and 860 during 24 February - 13 March 1997, and 3 patterns were apparent (Figure 8). First, during these 17 days the 10-month-old pups (820 and 860) generally stayed at rendezvous sites, and neither the breeding female (850) nor the collared yearling male (840) visited them. Second, during this period, the pups took 3 trips away from their rendezvous sites, apparently together. They started and finished these trips at nearly the same times (Table 3), remained <100 m apart during the trips, and could have been together. Third, the breeding female made 2 passes of several km circumventing the pups, traveling with the yearling male during only one pass (her inner pass in Figure 8).

Table 3.  Onset and cessation of excursions from 2 rendezvous sites by 10 month old wolf pups 820 and 860 near Little Falls, Minnesota, February and March 1997. Numbers indicate month/day hr:min.
Wolf Trip 1 Trip 2 Trip 3
Onset Cessation Onset Cessation Onset Cessation
820*   2/28 04:01 2/28 12:31 2/28 20:45 3/01 09:46 2/25 20:16 2/26 09:45
860** 2/28 04:01 2/28 13:02 2/28 21:00 3/01 10:01 2/25 21:01 2/26 09:46
  * GPS data collection interval: 1 location per 15 min.
** GPS data collection interval: 1 location per hr


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