Abstract: Photo-identification was used to examine range, rate of movement, and site fidelity of the river dolphins (Inia geoffrensis and Sotalia fluviatilis) in Peru’s Pacaya-Samiria Reserve from 1991 to 2000 (field work conducted all years and all seasons). Dolphins were identified by scars, cuts, nicks, pigmentation patterns, and abnormal beaks. Seventy-two Inia and 7 Sotalia were identified, and 25 Inia and one Sotalia were resighted. Sighting histories ranged from 1 d to 7.6 y. Maximum range of movement for Inia was 220 km, with a mean range of 60.8 km. Maximum range for Sotalia was 130 km. The greatest rates of movement observed were 120 km/2 d for Inia, and 56 km/9 h for Sotalia. The mean rate of movement was 14.5 km/d for Inia and 56 km/d for Sotalia. Identified dolphins were not observed to move between surveyed tributaries of the Marañón River but, instead, were always observed within the same tributary system. Ninety percent of all Inia resighted in one river system were seen in the same lake at least once, and 33% of dolphins resighted in the lake were never seen outside of the lake. Although photo-identification yielded new information about river dolphin movements and site fidelity, its utility was limited due to behavioral, morphological, and ecological characteristics of these cetacean species.

Key Words: RIVER DOLPHINS; INIA GEOFFRENSIS; SOTALIA FLUVIATILIS; SITE FIDELITY; MOVEMENT PATTERNS; RANGE; PHOTO-IDENTIFICATION; PERU; AMAZON RIVER

Document Type: Research article

DOI: 10.1578/AM.33.3.2007.359

Page Numbers: 359-367