The bottlenose dolphin Tursiops truncatus foraging around a fish farm:Effects of prey abundance on dolphins' behavior

The extent to which prey abundance influences both bottlenose dolphin foraging behavior and group size in the presence of human activities has not previously been studied.The primary aim of this study was to identify and quantify how wild bottlenose dolphins respond,individually and as groups,to the relative abundance of prey around a fish farm.Detailed views of dolphins' behavior were obtained by focal following individual animals whilst simultaneously collecting surface and underwater behavioral data.A total of 2150 dive intervals were analyzed,corresponding to 342 focal samples,lasting over 34 hours.Bottlenose dolphins remained submerged for a mean duration of 46.4 seconds and a maximum of 249 seconds.This study provides the first quantified data on bottlenose dolphin diving behavior in a marine fin-fish farm area.This study's results indicate that within a fish farm area used intensively by bottlenose dolphins for feeding,dolphins did not modify dive duration.Additionally,underwater observations confirmed that dolphins find it easier to exploit a concentrated food source and it appears that hunting tactic and not group size plays an important role during feeding activities.Thus,bottlenose dolphins appear capable of modifying their hunting tactics according to the abundance of prey.When top predators display behavioral responses to activities not directed at them,the task of studying all possible effects of human activities can become even more challenging.

Effects of study area size on home range estimates of common bottlenose dolphins Tursiops truncatus

Knowledge of an animal＇s home range is a crucial component in making informed management decisions. However, many home range studies are limited by study area size, and therefore may underestimate the size of the home range. In many cases, individuals have been shown to travel outside of the study area and utilize a larger area than estimated by the study design. In this study, data collected by multiple research groups studying bottlenose dolphins on the east coast of Florida were combined to determine how home range estimates increased with increasing study area size. Home range analyses utilized photo-identification data collected from 6 study areas throughout the St Johns River （S JR; Jacksonville, FL, USA） and adjacent waterways, extending a total of 253km to the southern end of Mosquito Lagoon in the Indian River Lagoon Estuarine System. Univariate kernel density estimates （KDEs） were computed for individuals with 10 or more sightings （n= 20）. Kernels were calculated for the primary study area （S JR） first, then additional kernels were calculated by combining the S JR and the next adjacent waterway; this continued in an additive fashion until all study areas were included. The 95% and 50% KDEs calculated for the S JR alone ranged from 21 to 35 km and 4 to 19 kin, respectively. The 95% and 50% KDEs calculated for all combined study areas ranged from 116 to 217 km and 9 to 70 km, respectively. This study illustrates the degree to which home range may be underestimated by the use of limited study areas and demonstrates the benefits of conducting collaborative science.

A method for classifying whistles of bottlenose dolphin(Tursiops truncates) based on syntactic pattern reorganization

A method based on syntactic pattern recognition was presented to automatically classify whistles of bottlenose dolphin. Dolphin whistles have typically been characterized in terms of their instantaneous frequency as a function of time, which is also known as ＂whistle contour＂. The frequency variation features of a whistle were extracted according to its contour. Then, the frequency variation features were used for learning grammatical patterns. A whistle was classified according to grammatical pattern of its frequency variation features. The exper- imental results showed that the classification accuracy of the proposed method was 95%. The method can provide technical support for acoustic study of dolphins＇ biological behavior.

Distribution and Relative Abundance of the Tursiops truncatus in Lebanese Marine Waters （Eastern Mediterranean）

Data related to the presence of cetaceans and especially the bottlenose dolphin （Tursiops truncatus） in Lebanese marine waters （eastern Mediterranean） are almost non-existent. This article aims to delimit, for the first time, the areas of distribution and the relative abundance of T. truncatus along the Lebanese coasts in order to develop a strategy for the conservation of this species. Nine campaigns at sea, each lasting between 1 to 3 days, were conducted aboard the vessel ＂CANA＂ between September 2009 and August 2012 in Lebanese marine waters. A total of 1576 km in prospecting effort was covered along the Lebanese coast （220 km）. Dolphins were mainly sighted in the central region of Lebanon （120 km） and 32 sightings and 91 individuals were recorded. The size of the groups were ranged from a minimum of one individual and a maximum of 7 individuals. Relative abundance of T. truncatus for the whole studied region is 0.06 individuals＇km1 in prospecting effort while it is 0.11 individuals·km^-1 in Beirut area that offers habitats sought by this species. The bathymetric distribution of this species is spread over a wide range from a depth of 35 m to 1300 m. More than half of the individuals have been observed in areas where bathymetry ranges between 300 m and 600 m depths.

Site Fidelity and Residency of Tursiops truncatus off the Aragua Coast,Venezuela-First Records of Long Residency

This study represents the first comprehensive analysis of the residency patterns of a coastal population of bottlenose dolphin off the coast of Aragua,Venezuela,over a multi-year period.Using photo-identification,the most recent study(2019-2020)identified 56 individuals with the time between encounters from one to 344 days between the first and last sighting.Site Fidelity(SF)and Residence(RES)indices were calculated and Agglomerative Hierarchical Clustering(AHC)modeling was performed,with three patterns of residence obtained:resident(25%),semi-resident(17.86%)and transient(57.14%).These results were contrasted with remodeled data from a previous study(2006-2007),showing similar patterns:resident(24.44%),semi-resident(28.89%)and transient(46.67%).Importantly,two individuals were found to have been resident over the extended period.A breeding female sighted for the first time in 2004 and again in 2020(16 years)and the other from 2005 to 2020(15 years).This region is an important area for marine mammals,known to support a resident reproductive population over many years,as well seabirds,sea turtles,whale sharks and fishermen.We recommend that consideration be given to designating the waters as a Marine Protected Area to safeguard the existing population and provide benefit to the surrounding marine environment.