Home range use and distribution of resident bottlenose dolphins (Tursiops truncatus) in the Cres-Losinj Archipelago (northeastern Adriatic Sea, Croatia).

摘要

One of the most common odontocetes in the Mediterranean Sea, the common bottlenose dolphin (Tursiops truncatus ), has been studied in the northern Adriatic Sea since 1987. However, distribution and home range patterns of the bottlenose dolphin population of the Cres-Losinj Archipelago, Croatia, are not well understood. Ad libitum photo-identification survey data were collected from January 2005 until December 2012 from a small, inflatable watercraft during favorable sea conditions in the Kvarneric region. Individual dolphins were identified by distinctive dorsal fin characteristics (such as scars, notches, nicks, holes, or general fin shape) and categorized as resident or transient animals based on their overall re-sighting patterns. Animals were identified as resident for this study if they were seen throughout the 8-year study period, year-round (in at least 13 of 16 seasons divided into winter and summer), and sighted at least 20 times. Other dolphins were classified as transients. From 2005 to 2012, 38 resident dolphins and 533 transient dolphins were identified.;The 95% and 50% (core use area) fixed kernel density (FKD) estimators and 100% minimum convex polygon (MCP) estimator were calculated for 20 resident bottlenose dolphins with the greatest number of sightings over an 8-year period (2005-2012). The mean overall home range area using the MCP method was 552.1 +/- 139.6 km2 (range: 303.0 to 832.6 km2). Using the 95% fixed kernel density estimator method, the average home range size was 494.6 +/- 190.5 km2 (range: 206.6 to 848.6 km 2). This large interval showed strong evidence of variations in the home ranges of individual dolphins. Core use areas ranged from 53.9 to 212.9 km2 (mean: 120.2 +/- 48.9 km2). The relative size of the core use areas (ratio of 50% to 95%) ranged from 21% to 30% of an individual's home range (mean: 24.3 +/- 2.4%). There was no significant difference between the home range sizes or average linear distance from shore of known adult male and adult female dolphins. There was no significant difference between the summer and winter home range sizes of the 20 resident bottlenose dolphins. However, the average linear distance from shore was larger during the summer than during the winter.;The home range of the 20 resident bottlenose dolphins extended beyond the boundaries of the former Cres-Losinj Special Marine Reserve (CLSMR) area. The combined home range size of the 20 resident bottlenose dolphins was approximately 200 km2 larger than the former Special Marine Reserve, and extended south to the island of Olib, along the western shore of Losinj, and north to the island of Rab. Therefore, it would be beneficial to develop conservation plans in the region to extend the former CLSMR to the south, west, and north to encompass the total home range of the resident bottlenose dolphins. Knowledge about the home range size and location of the bottlenose dolphins in the Cres-Losinj Archipelago is critical for understanding the dolphin's vital resources, identifying their critical habitats, and determining potential overlap with anthropogenic activities along the coast.