First observed wild birth and acoustic record of a possible infanticide attempt on a common bottlenose dolphin (Tursiops truncatus)

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Society for Marine Mammalogy for personal use, not for redistribution. The definitive version was published in Marine Mammal Science 32 (2016): 376–385, doi:10.1111/mms.12248.We observed the birth of a common bottlenose dolphin (Tursiops truncatus) followed immediately by a possible infanticide attempt in the estuary near Savannah, Georgia. Our report is unique in several ways: first, we witnessed the birth of the calf; second, we observed infanticidal behavior almost immediately afterward; and third, we obtained acoustic recordings concurrent with the possible infanticidal behavior. Our observations provide insight into aggressive, possible infanticidal, behavior in bottlenose dolphins.Boat time and support was provided by Department of Education/Title VII Award P382G090003. Additional support was provided by EDGE (Enhancing Diversity in Geosciences Education through Costal Research in Port City) NSF award GEO-0194680.2016-07-1

Social Differentiation in Common Bottlenose Dolphins (Tursiops truncatus) that Engage in Human-Related Foraging Behaviors.

Both natural and human-related foraging strategies by the common bottlenose dolphin (Tursiops truncatus) have resulted in social segregation in several areas of the world. Bottlenose dolphins near Savannah, Georgia beg at an unprecedented rate and also forage behind commercial shrimp trawlers, providing an opportunity to study the social ramifications of two human-related foraging behaviors within the same group of animals. Dolphins were photo-identified via surveys conducted throughout estuarine waterways around Savannah in the summers of 2009-2011. Mean half-weight indices (HWI) were calculated for each foraging class, and community division by modularity was used to cluster animals based on association indices. Pairs of trawler dolphins had a higher mean HWI (0.20 ± 0.07) than pairs of non-trawler dolphins (0.04 ± 0.02) or mixed pairs (0.02 ± 0.02). In contrast, pairs of beggars, non-beggars, and mixed pairs all had similar means, with HWI between 0.05-0.07. Community division by modularity produced a useful division (0.307) with 6 clusters. Clusters were predominately divided according to trawler status; however, beggars and non-beggars were mixed throughout clusters. Both the mean HWI and social clusters revealed that the social structure of common bottlenose dolphins near Savannah, Georgia was differentiated based on trawler status but not beg status. This finding may indicate that foraging in association with trawlers is a socially learned behavior, while the mechanisms for the propagation of begging are less clear. This study highlights the importance of taking into account the social parameters of a foraging behavior, such as how group size or competition for resources may affect how the behavior spreads. The positive or negative ramifications of homophily may influence whether the behaviors are exhibited by individuals within the same social clusters and should be considered in future studies examining social relationships and foraging behaviors

Mean half-weight association indices between pairs of common bottlenose dolphins <i>Tursiops truncatus</i> near Savannah, Georgia that associate with trawlers (T) and do not associate with trawlers (NT), and separately for dolphins that are beggars (B) and non-beggars (NB).

<p>Mean half-weight association indices between pairs of common bottlenose dolphins <i>Tursiops truncatus</i> near Savannah, Georgia that associate with trawlers (T) and do not associate with trawlers (NT), and separately for dolphins that are beggars (B) and non-beggars (NB).</p

Utilization areas for social clusters of common bottlenose dolphins <i>Tursiops truncatus</i> near Savannah, Georgia.

<p>Clusters 1, 2, and 3 were considered non-trawler clusters, and clusters 4, 5, and 6 were considered trawler clusters.</p

The study area, located near Savannah, Georgia.

<p>Transects surveyed are denoted for each year of surveys from 2009–2011.</p

Summary of half-weight association indices for common bottlenose dolphins <i>Tursiops truncatus</i> near Savannah, Georgia.

<p>Summary of half-weight association indices for common bottlenose dolphins <i>Tursiops truncatus</i> near Savannah, Georgia.</p

Six social clusters of common bottlenose dolphins <i>Tursiops truncatus</i> near Savannah, Georgia.

<p>Six social clusters of common bottlenose dolphins <i>Tursiops truncatus</i> near Savannah, Georgia.</p