Integration of a social cluster of Atlantic spotted dolphins (Stenella frontalis) after a large immigration event in 2013

Abstract

Demographic changes can result in alterations of social structure and behavior which in turn may affect survival, reproduction, or movement and may influence how populations respond to changes in the environment. In 2013, 52 Atlantic spotted dolphins (Stenella frontalis) left Little Bahama Bank (LBB) and immigrated into a resident group of spotted dolphins on Great Bahama Bank (GBB). Initially there was little interaction and two distinct social clusters delineated by residency status. Here we describe the social structure of the dolphins on GBB between 2015-2020.Analyses were conducted with SOCPROG 2.9 and coefficients of association were nonrandom. The number of associations between LBB and GBB individuals increased, and standardized lagged association rates indicated continued associations over time. Modularity analysis showed one community without clear social clusters, although there were preferential associations within the original communities. Multiple Regression Quadratic Assignment Procedure indicated that sex, age, and residency status were good predictor variables that explained the patterns of the association indices. Male alliances were present between LBB, GBB, and LBB/GBB males. New and old relationships are influencing the social restructuring of this community. This

Social and community structure of striped dolphins in a semienclosed Mediterranean embayment

“…The temporal patterns of association of striped dolphins in the Gulf of Corinth indicate that individuals associated on two different time scales; a short, casual level of association and a long‐term one (“two levels of casual acquaintances”; Whitehead, 2008b). This pattern was also found in Atlantic spotted dolphins in the Bahamas (Elliser & Herzing, 2016; Elliser et al, 2023), bottlenose dolphins in eastern Scotland (Lusseau et al, 2006), western Ireland (Baker et al, 2018), in the Sado Estuary, Portugal (Augusto et al, 2012) and Madeira Archipelago (Dinis et al, 2018), white‐beaked dolphins, Lagenorhynchus albirostris , off Iceland (Bertulli et al, 2021), Australian humpback dolphins Sousa sahulensis in Australia (Parra et al, 2011) and Hong Kong waters (Dungan et al, 2012), and dusky dolphins in Argentina (Degrati et al, 2019).…”

“…The temporal patterns of association of striped dolphins in the Gulf of Corinth indicate that individuals associated on two different time scales; a short, casual level of association and a long-term one ("two levels of casual acquaintances"; Whitehead, 2008b). This pattern was also found in Atlantic spotted dolphins in the Bahamas (Elliser & Herzing, 2016;Elliser et al, 2023), bottlenose dolphins in eastern Scotland (Lusseau et al, 2006), western…”

“…The mean HWI was 0.03, and it was lower than that found in other studies on the genus Stenella . For instance, Atlantic spotted dolphins around Bimini Island and Great Bahama, in the Bahamas Archipelago, had mean HWIs of 0.13 (Danaher‐Garcia et al, 2020) and 0.17–0.21 (depending on the year; Elliser et al, 2023), respectively. Higher values were recorded for spinner dolphins at Midway Atoll in the Pacific Ocean, where one portion of the population (reported as “resident”) showed a mean HWI of 0.37, and the other portion (reported as “immigrant”) a mean HWI of 0.63 (Karczmarski et al, 2005).…”

“…This long‐term and stable clustering was disrupted when all members of the central cluster and few from the other two clusters moved to Great Bahama Bank, Bahamas, where another community of Atlantic spotted dolphins was already present (Herzing et al, 2017; Danaher‐Garcia et al, 2020). The clustering patterns changed after the immigration event (Herzing et al, 2017), but after a few years the association patterns changed again, until all individuals were considered as belonging to a single community without distinct clusters (Elliser et al, 2023). While these examples do not help explain the clustering of striped dolphins in the Gulf of Corinth, they suggest that clusters may be specific to a given area or local population, and they may be impermanent.…”

The evolution of peace

“…Humans are unusual for the range of our intergroup relationships which can include affiliation and altruism toward strangers as well as destructive large-scale wars. While other social species such as dolphins and bonobos may have affiliative relationships between groups (Danaher-Garcia, Connor, Fay, Melillo-Sweeting, & Dudzinski, 2022; Elliser, Volker, & Herzing, 2022), sustained positive-sum relationships that cross pronounced group boundaries are exceedingly rare among nonhuman animals likely appearing only in a few eusocial insect species. Our cousins the bonobos often have affiliative interactions with other bonobo groups that include grooming, sex, and sometimes food sharing (Lucchesi et al, 2020; Samuni, Langergraber, & Surbeck, 2022).…”