We used VHF, GPS and satellite radiocollars to study details of long distance movements by four Minnesota wolves (Canis lupus). Number of locations during our tracking ranged from 14 to 274. Farthest distances reached ranged from 183-494 km. and minimum distances traveled (sums of line segments) ranged from 490-4251 km. Numbers of times wolves crossed state, provincial or interstate highways ranged from 1 to 215. All four of the wolves returned to or near their natal territories after up to 179 d and at least two left again.
Some gray wolves (Canis lupus) travel to areas over 800 km away from their packs. Until recently it has been technologically or financially difficult to determine the detailed routes of these wolves because of the distances involved. Often, the only information available is the starting point based on where a wolf was originally captured and marked and the ending point based on a capture, road-kill or other type of recovery reported later. Recently, however, newer technology such as satellite tracking and Global Positioning System (GPS) collars suitable for wolves have yielded detailed descriptions of wolf routes. These more detailed descriptions allow a better understanding of wolf travels and extraterritorial movements and suggest new questions about such movements. Using GPS, satellite and aerial VHF telemetry, we provide descriptions of four wolf travel routes.
One wolf in our study left from the east-central Superior National Forest in northeastern Minnesota .... The area has long been saturated with wolf pack territories. Three other wolves made long extraterritorial movements from a wolf population at Camp Ridley, a 21,400 ha National Guard Training Site in Little Falls, Minnesota at the southern edge of wolf range. Camp Ridley ... is surrounded on the east and south by agricultural lands and on the north and west by forest interspersed with agricultural development.
Male wolf 2480 ([18-mo. old or older]; ages estimated by tooth wear) was live-trapped in a modified steel foot-trap on 1 November 1972, anesthetized, collared with a 540 g standard VHF radio-collar and aerially radio-tracked weekly. He was a member of a pack of 12 wolves that lived 20 km west of Ely, Minnesota.
On 3 February 1998 male wolf 5399 ([18-mo. old or older]) born at Camp Ridley was captured by helicopter net-gunning. A 920 g GPS collar was placed on the wolf and the wolf was released. The collar had been programmed to acquire a GPS location every 3 h .... We dropped the collar off the wolf via remote signal, homed in on its VHF signal, collected the collar and downloaded the data.
A 500 g satellite collar ... was placed on male wolf 7803 (10-mo.old) which had been captured by helicopter net-gunning at Camp Ridley on 1 February 1998. After retrieval and refurbishing the collar was placed on female wolf 7804 (2-yr old; aged by following her with a VHF radio since she was a pup) on 3 February 1999 .... ArcView geographic information system was used to create maps and calculate distances traveled and the number of times wolves crossed state, provincial and interstate highways.
We located wolf 2480 at 28 locations in his pack territory from 13 November 1972 through 21 March 1973; then on 26 March 1973 the wolf was located 12 km north of his territory, his first extraterritorial location. After that the wolf was located 17 times through 30 June 1973 away from his pack's territory and traveled almost exclusively through wilderness (we recorded only one highway crossing). He returned to within 8 km of his pack territory after 1 mo. Because of the infrequent radio-tracking, wolf 2480 could well have visited the pack without our having detected it. We do not know if the first trip was a predispersal foray or an actual dispersal.
After 19 April 1973 wolf 2480 moved north again and then west through Ontario to a more open area (17 May 1973) with more roads and humans and eventually to the east shore of Lake-of-the-Woods. He traveled northeastward parallel with the shore for about 40 km and then the signal emanated from the same location for 2 wk, so a ground check was made. The collar was found by itself, with no indication of what happened to the wolf.
Satellite-collared wolf 7803 left his territory on 12 September 1998 headed directly away from the known wolf breeding range. His collar collected 55 locations during movements through agricultural areas before he was shot by a coyote hunter near Howard Lake, MN on 14 November 1998. He made at least 33 highway crossings. Wolf 7804, also satellite-collared, left on 26 March 1999; during her travels the wolf stopped directional movement for 37 d between Wisconsin Dells and Stevens Point. This area includes several rugged wetlands with low human presence. The collar collected 274 locations by 21 September, when the wolf returned to camp Ripley. On 25 September the wolf left again, settled about 40 km east of Camp Ridley and was killed illegally on about 11 November 1999. She made at least 215 highway crossings.
The GPS collar on male wolf 5399 collected 1121 locations on 57 days of the animal's extraterritorial trips. The wolf left the territory on 31 May 1998 and traveled an average of at least 3.55 km/h ... during his trip. He made at least 17 highway crossings. He returned to near his natal territory and, therefore, we considered the long movement an extraterritorial foray. The wolf may have rejoined the pack shortly after the collar was dropped.
No data are available that would allow an estimate of the proportion of wolves in the populations studied that make long distance moves because (1) with one wolf (2480), a special effort was made to follow it wherever it went, whereas no such effort was made for other wolves in that study, (2) wolf 5399 was part of a very small sample on which GPS collars were tested and (3) with the last two wolves (7803 and 7804), a special effort was made to select predispersal individuals (nonalpha, at least 1-y old wolves) on which to place the satellite collars.
The four wolves studied all traveled far from their pack territories....
All four wolves also returned to their territories or nearby after travels as far away as 494 km and periods up to 179 d. Two of the four then left again; one remained about 40 km from its territory for 9 wk (wolf 7804 ...); we could not follow the fourth wolf after its return. Wolves returning to their natal territories after long periods away have been documented before.
In two cases, the wolves we followed made large loops to return, whereas one wolf (wolf 5399) returned on almost the same route by which it had left. The loop returns suggest that even at distances of 494 km from their territory and for absences as long as 179 d, wolves remember their territory location....
Several remaining questions about distant wolf travels include "What constitutes wolf travel barriers?," "Are there travel corridors that wolves favor?," and "To what extent do wolf populations adapt to travel barriers and corridors?" .... Satellite and GPS telemetry...provide the first opportunity to examine these questions in greater detail.
Studies reviewed by Fuller (1989) report high, human-caused, wolf mortality rates. Much of this mortality was from motor vehicles, suggesting that roads can hinder wolf travel. In our study, however, collared wolves safely crossed major highways. Three of the four wolves studied (7803, 7804 and 5399) crossed numerous interstate highways and many more smaller roads during their travels. This behavior supports findings that wolves in the Midwest are rapidly adapting to human presence. The fourth wolf (2480) traveled mostly through wilderness, likely encountering few human structures. Nevertheless, the long distances the other wolves traveled through mostly human-dominated landscapes illustrates that few structures or landscape features could be considered travel barriers for these wolves. Roads will continue to pose risks to any wolves crossing them, but their function as travel barriers is perhaps more a question of probability than of permeability.
Figure 1: Long-distance travel routes of four wolves collared in Minnesota.
Table 1: Summary of information about Minnesota wolves that traveled long distances from their pack territories.