ABSTRACT

With the goal of gathering ecological data in order to develop future cetacean management and conservation plans, the distribution, home range (HR) and residency of bottlenose dolphins (Tursiops truncatus) were studied in the central-north Mexican Gulf of Mexico (21°35’ N, 97°19’ W and 20°08’ N, 96°40’ W). Between July 2005 and June 2008, 59 boat surveys were carried out for a total of 313 h of effort at sea. During these surveys, 471 individuals were observed in 88 different groups. Photographs of naturally marked animals resulted in 275 different individuals photo-identified. Their distribution was homogeneous throughout the study site at a mean distance from coast of 2.5 km (SD = 2.9,  n = 471) and depths below 20 m. Of the total of dolphins identified, 202 (73%) had a low sighting rate and were considered transients, whereas 34 individuals (12%) with medium and high sighting rates were considered resident animals. Home range estimates using the minimum convex polygon method showed a mean of 2771 ±1116 km². Using the adaptive kernel method, the average size of home range was 1199 ± 143 km², with five core areas identified. These areas decreased in size during rainy season because dolphins remained close to the rivers’ plumes. At individual level, the mean home range was 129.2 km² (n = 66), according to other reports from Texas and Florida in spite of the habitat differences. The main component determining the size of the home range in this area was the presence of rivers, rather than the geomorphology of the coast.