Dusky dolphins: modeling habitat selection

GRISELDA V. GARAFFO; SILVANA L. DANS; ENRIQUE A. CRESPO; MARIANA DEGRATI; PAULA GIUDICI; GAGLIARDINI ANTONIO

JOURNAL OF MAMMALOGY

ALLIANCE COMMUNICATIONS GROUP DIVISION ALLEN PRESS

Año: 2010 vol. 91 p. 54 - 65

0022-2372

The use of habitat selection models to predict the likely occurrence of wild populations is an important tool in conservation planning and wildlife management. The goal of the work reported here was to build habitat selection models for Golfo Nuevo, Argentina, considering a set of variables (depth, slope, distance from shore, sea surface temperature (sst) and chlorophyll). Random transects were surveyed by a boat (2002-2007). A grid of 1.5x1.5-km squares was constructed for the study area. A GIS was used to integrate the variables with the grid; each cell was characterized by depth, slope, distance from shore, sst, chlorophyll, presence-absence of dolphins and a coefficient of use by dusky dolphins. Models were developed for each season (warm and cold) and then for all the data together. Data collected during 2002-2005 were pooled to develop the model, and data collected during 2006-2007 were used for cross-validation. Logistic regression with a binomial error structure and a logit-link function were used to relate the presence of dolphins to habitat variables. Models with gamma structure and log-link function were used to relate area use  to habitat variables The models were selected with Deviance Analysis and AIC. All predictor variables significantly influenced the dolphins´ distribution. The dolphins showed a clear preference for steep areas between 50 and 60m of depth, distance from shore of 3-5km and higher values of chlorophyll. In the warm season, the dolphins showed preference for colder waters. The dolphins avoided deeper and warmer areas. Dusky dolphins in Golfo Nuevo are exploited as a tourism resource, and. the selected models should be considered when deciding the management scheme of dolphin-watching activities.