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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, 7/29 - 9/21); we could not follow the fourth wolf after its return. Wolves returning to their natal territories after long periods away have been documented before (Fritts and Mech, 1981; Messier, 1985; Mech, 1987; Mech and Seal, 1987; Fuller 1989).

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 (Fig. 1). 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. This finding extends earlier work showing that wolves moved as far as 63 km from their capture points for as long as 24 d can return (Fritts et al., 1984).

Several remaining questions about distant wolf travels include "What constitutes wolf travel barriers?," "Are there travel corridors (Hobbs, 1992) that wolves favor?," and "To what extent do wolf populations adapt to travel barriers and corridors?" (Mech, 1995). With aerial VHF telemetry, relatively few locations are obtainable during long wolf travels (Table 1), so these questions are difficult to address. Satellite and GPS telemetry, however, 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 (Thiel et al., 1998). 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 illustrate 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.