Fission–fusion dynamics of a pelagic delphinid in the arctic: the white‐beaked dolphin (Lagenorhynchus albirostris)

Abstract

Delphinids exhibit great variability in their social structures. It is therefore important to document lesser known species, in extreme changing habitats, to compare and contrast mechanisms driving sociality. Here, we describe the first long-term assessment of social structure of white-beaked dolphins (Lagenorhynchus albirostris) using a compiled version of SOCPROG 2.8 and an 11-year photo-identification dataset (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) collected from whalewatching vessels at 2 sites (Faxaflói and Skjálfandi bays) off Iceland. We identified a total of 487 dolphins which are suggested to be part of an open population as shown by the discovery curve obtained analyzing photo-id data. The social analyses were restricted to 35 adults which were sighted on ≥5 different days. The mean residency time of white-beaked dolphins in our 2 study areas was of 95 days (SE = 35.63; 95% CI: 23-171), with the "migration-full interchange" model best describing movements of dolphins in and out of our 2 study sites. Social differentiation in this population was high (Likelihood: S = 0.87, SE = 0.04; r = 0.31, SE = 0.03) indicating diverse, non-random social relationships. Temporal associations best fit the model of "casual acquaintances" against the standardized lagged association rates with the majority of white-beaked dolphin associations being short-term, but with a few long-term across years. Testing for preferred companionship, long-term associations are favored over short-term. In this study, associations among white-beaked dolphins are short-term but with desirably long-term associations fitting into a society with fission-fusion dynamics. This information expands the latitudinal range for which social structure has been described for oceanic dolphin species.

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).…”

“…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).…”

Research on whales, dolphins, and porpoises

“…Understanding the intra-and inter-population variability in social features is essential to socioecological studies on a specific cetacean species (Gygax 2002;Gowans et al 2007). In this volume, Bertulli et al (2021) built an 11-year photo-identification dataset for the white-beaked dolphins (Lagenorhynchus albirostris) in 2 regions off Iceland. Results indicated that associations among white-beaked dolphins were short-term but with preferred long-term associations fitting into a society with fission-fusion dynamics.…”

“…In this volume, Bertulli et al . (2021) built an 11‐year photo‐identification dataset for the white‐beaked dolphins ( Lagenorhynchus albirostris ) in 2 regions off Iceland. Results indicated that associations among white‐beaked dolphins were short‐term but with preferred long‐term associations fitting into a society with fission–fusion dynamics.…”

The partial merger of two dolphin societies

“…A fission–fusion grouping pattern is often described in other species of in- or near-shore delphinids (e.g. Australian humpback dolphins, Sousa sahulensis [ 18 ]; white-beaked dolphins, Lagenorhynchus albirostris [ 19 ]), including Atlantic spotted dolphins ( Stenella frontalis ) in The Bahamas, that have been the subject of two long-term studies [ 20 , 21 ]. Our group, the Dolphin Communication Project (DCP), has been studying a resident group of approximately 120 spotted dolphins in an area of roughly 250 km 2 on the northwestern portion of the Great Bahama Bank in the coastal waters around Bimini, The Bahamas, since 2003 [ 20 ].…”