Barking Frogs (Eleutherodactylus augusti) are the northernmost ranging member of the large tropical family Leptodactylidae. We investigated the ecology of this saxicolous species at the northern edge of its range in a canyon in southern Arizona. We captured 54 frogs on discontinuous rock outcrops; eight of nine females and 39 of 45 males were on limestone outcrops. The remaining frogs were closer to limestone outcrops by more than 200 m than would be expected if they were distributed randomly with respect to limestone formations. Seven of 10 frogs radio-tracked had core home ranges (50% fixed kernel) from 94 to 100% on limestone; the other three frogs did not have any part of their home range on limestone outcrops. During five years of mark-recapture efforts, no frogs were found on a different outcrop from the one where they were originally captured; no radio-tracked frogs moved between outcrops during the breeding season. We estimated that four to 20 Barking Frogs occupied each outcrop; these groups probably are connected primarily by juvenile dispersal. As an organism living at the edge of its range, Barking Frogs in Arizona may rely heavily on extensive underground areas such as those found in limestone to protect them from a physiologically challenging environment. To manage for the persistence of Barking Frogs in southern Arizona, we must identify and protect habitat patches and movement pathways among them.