Seasonal abundance and adult survival of bottlenose dolphins (Tursiops truncatus) in a community that cooperatively forages with fishermen in southern Brazil.

摘要

A subgroup of a population of Tursiops truncatus in southern Brazil is known for a cooperative behavior with artisanal fishermen whereby the dolphins shoal fish towards net-casting fishermen. Combining photo-identification data collected between September 2007 and 2009 with mark-recapture and Pollock's robust design models, we assessed abundance within seasons and survival and temporary emigration rates of dolphins between seasons. We also reanalyzed a previous data set collected during 1989-1991, and Cormack-Jolly-Seber models were applied to estimate survival rates for each of the study periods. The abundance of marked "cooperative" dolphins varied between seasons from 18 (CI: 17-24) to 21 (CI: 20-24). The total abundance varied from 59 in the winter of 2008 (CI: 49-72) to 50 in the autumn of 2009 (CI: 40-62). The annual adult survival was estimated to be 0.917 (CI: 0.876-0.961), close to that estimated from data collected in the 1990 s (0.941; CI: 0.888-0.998). The emigration probability was low (0.031; CI: 0.011-0.084) and different capture probabilities between the "cooperative" and "noncooperative" dolphins indicated a degree of behavioral segregation. The precision of our estimates is likely to provide sufficient power to detect population change, but we recommend a precautionary management approach to protect this vulnerable dolphin community and its unique cooperative feeding tradition.Digital Object Identifier http://dx.doi.org/10.1111/j.1748-7692.2012.00571.x