Conspecific scarring on wild belugas (Delphinapterus leucas) in Cunningham Inlet

Abstract

Intra-specific aggression is not frequently observed in wild cetaceans, including belugas. One proxy, identified in past research, that indicates past aggressive behaviour is the presence of rake marks (scars left on skin by the teeth of conspecifics). Behavioural observations of belugas, compared to bottlenose dolphins, suggest that belugas engage in less physically aggressive behaviour; yet, a detailed study of beluga aggressive behaviour remains to be conducted. Beluga intra-specific aggression was assessed by scoring photographs taken from July to August in 2015 at Cunningham Inlet, Canada for the presence/absence and body location of rake marks. Of the 252 belugas analysed, 44% had rake marks. The results suggest that physical aggression occurs comparatively less with only half of the observed beluga population having rake marks compared to almost all bottlenose dolphins previously surveyed. We suggest social structure, skin pigmentation, and/or species-specific behaviours as explanations for the differences in rake marks among species.

The effect of age, sex, and resource abundance on patterns of rake markings in resident killer whales (Orcinus orca)

“…Although rake marks only provide an indirect measure of aggression, biting has been found to be closely associated with aggressive behavior in several species of toothed whales (Connor et al, 2000; Samuels & Gifford, 1997) and in some instances, play behavior (which may also lead to rake marks) can develop into aggression (Scott et al, 2005). As such, rake marks on toothed whales likely reflect the level and context of aggression received (Ham et al, 2021; Scott et al, 2005), which varies widely across species according to their evolutionary history. For example, in some species, including narwhals, ( Monodon monoceros , Gerson & Hickie, 1984), Risso's dolphins, ( Grampus grisues , MacLeod, 1998), and sperm whales, ( Physeter microcephalus , Kato, 1984), diet specialization is believed to have driven a reduction in the repigmentation of tooth scars during wound‐healing (MacLeod, 1998).…”

Season, age, sex, and location impact the density of tooth rake mark and dorsal fin notch of Indo‐Pacific humpback dolphins (Sousa chinensis) in the northern South China Sea

“…Most sightings exhibited tooth rake marks (62.08%) and dorsal fin notches (95.03%), suggesting that, like in other odontocete species (e.g., bottlenose dolphins, 83.1% of individuals, Scott et al, 2005; belugas, Delphinapterus leucas , 44% of individuals, Ham et al, 2021a), aggressive behaviors are common among IPHDs. The rates we found for IPHDs fall in between bottlenose dolphins (between 80% and 100% of individuals; Luksenburg, 2014; Marley et al, 2013; Scott et al, 2005) and belugas (44% of individuals, Ham et al, 2021a).…”

“…Most sightings exhibited tooth rake marks (62.08%) and dorsal fin notches (95.03%), suggesting that, like in other odontocete species (e.g., bottlenose dolphins, 83.1% of individuals, Scott et al, 2005; belugas, Delphinapterus leucas , 44% of individuals, Ham et al, 2021a), aggressive behaviors are common among IPHDs. The rates we found for IPHDs fall in between bottlenose dolphins (between 80% and 100% of individuals; Luksenburg, 2014; Marley et al, 2013; Scott et al, 2005) and belugas (44% of individuals, Ham et al, 2021a). While most bottlenose dolphins are known to exhibit a fission‐fusion social structure with males forming long‐lasting bonds with other males (Connor et al, 2000; Mann, 2006), belugas' social structure is less clear but has also been described as fission‐fusion during summer congregations (Colbeck et al, 2012).…”

“…In addition, even though more data is needed to validate the presented model, this work confirms the usefulness of tooth rake mark and notch density to determine the sex of IPHDs. Scott et al, 2005) and belugas (44% of individuals, Ham et al, 2021a). While most bottlenose dolphins are known to exhibit a fission-fusion social structure with males forming long-lasting bonds with other males (Connor et al, 2000;Mann, 2006), belugas' social structure is less clear but has also been described as fission-fusion during summer congregations (Colbeck et al, 2012).…”

Seasonality of social behaviour among immature belugas (Delphinapterus leucas) in managed care

“…Most agonistic interactions consisted of open-mouth displays, head jerks and brief interactions and rarely included any form of physical contact between individuals. Further study of wild belugas is necessary to know if agonistic behaviour is similarly infrequent and mostly display-based (e.g., Ham et al 2021).…”