Striped dolphin (Stenella coeruleoalba), one of the most widespread cetacean species in the Mediterranean Sea, is an extremely vocal mammalian species but its visual and acoustic behaviour, are still unknown. This study describes for the first time how Stenella coeruleoalba echolocation clicks rate, changes in relation to focal group size and behavioral context. During the summers 2009-2010, in an area of over 700 Km2 located in the Ionian Sea (Gulf of Corinth,Greece), continuous passive acoustic and behavioral simultaneous data were collected broken down into 3-minute-intervals. The sound recordings were made in the proximity of the animals with a single hydrophone and a digital audio M-Audio microtrack recorder. 63 surveys were made, 44 sightings were recorded, and 3,5 hours of behavioral observations and simultaneous recordings were sampled. For each 3-minute-interval of recording data, only the clicks detected in the first 10 seconds were considered. 5015 echolocation clicks were then detected. Group dimension was divided in four categories: 1) 1-5; 2) 6-9; 3) 10-15; 4) 20-30 animals. Statistical analysis (Spearman’s test) showed a significant correlation of the click rate in relation to behavioral state linked to forage and travel activities. The relationship between group size (number of animals) and the echolocation clicks density in the first 10 seconds divided for the number of animals (number of clicks/minute/animals) was also examined. Statistical analysis (Kruscall-Wallis Test) showed that the echolocation clicks density was significantly affected by group size (P< 0.05), as the echolocation production per dolphin decreased as the group size increased. These results support the idea that echolocation information can be shared by the animals in a larger group.
Mediterranean striped dolphins share echolocation information during travelling and foraging
GIACOMA, Cristina;PAPALE, ELENA;
2011-01-01
Abstract
Striped dolphin (Stenella coeruleoalba), one of the most widespread cetacean species in the Mediterranean Sea, is an extremely vocal mammalian species but its visual and acoustic behaviour, are still unknown. This study describes for the first time how Stenella coeruleoalba echolocation clicks rate, changes in relation to focal group size and behavioral context. During the summers 2009-2010, in an area of over 700 Km2 located in the Ionian Sea (Gulf of Corinth,Greece), continuous passive acoustic and behavioral simultaneous data were collected broken down into 3-minute-intervals. The sound recordings were made in the proximity of the animals with a single hydrophone and a digital audio M-Audio microtrack recorder. 63 surveys were made, 44 sightings were recorded, and 3,5 hours of behavioral observations and simultaneous recordings were sampled. For each 3-minute-interval of recording data, only the clicks detected in the first 10 seconds were considered. 5015 echolocation clicks were then detected. Group dimension was divided in four categories: 1) 1-5; 2) 6-9; 3) 10-15; 4) 20-30 animals. Statistical analysis (Spearman’s test) showed a significant correlation of the click rate in relation to behavioral state linked to forage and travel activities. The relationship between group size (number of animals) and the echolocation clicks density in the first 10 seconds divided for the number of animals (number of clicks/minute/animals) was also examined. Statistical analysis (Kruscall-Wallis Test) showed that the echolocation clicks density was significantly affected by group size (P< 0.05), as the echolocation production per dolphin decreased as the group size increased. These results support the idea that echolocation information can be shared by the animals in a larger group.
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