Occurrence of long-finned pilot whales (Globicephala melas) and killer whales (Orcinus orca) in Icelandic coastal waters and their interspecific interactions

Abstract

Long-finned pilot whales and killer whales are widely distributed across the North Atlantic, but few studies have reported their occurrence in Icelandic coastal waters. Here, we use sightings data from research platforms and whale watching tours in six regions of Iceland from 2007 to 2020 to show that the occurrence of long-finned pilot and killer whales varied with region and season. Killer whales were regularly encountered in the south of Iceland during summer and west of Iceland during winter/spring. Long-finned pilot whales were only seen during the summer and were most often encountered in the south, west, and northwest of Iceland. Long-finned pilot whale occurrence in the south of Iceland appeared to increase during the study period but killer whale occurrence showed no noticeable changes. Long-finned pilot whales were sighted often in the areas that were also frequented by killer whales and interspecific interactions were commonly observed when both species co-occurred. Interactions appeared to be antagonistic, with killer whales often avoiding long-finned pilot whales and sometimes fleeing at high speed, similar to what has been described elsewhere in the North Atlantic. In the majority of interactions observed (68%), killer whales avoided long-finned pilot whales by moving away, but in 28% avoidance was at high speed with both species porpoising. This variability in the type of behavioural responses indicates that interactions may be more complex than previously described. We discuss regional trends in long-finned pilot whale and killer whale sightings and potential drivers of the observed interactions.

First account of apparent alloparental care of a long-finned pilot whale calf (Globicephala melas) by a female killer whale (Orcinus orca)

“…While we do not know how the observed relationship between SN0540 and the pilot whale calf started, it does suggest a possible novel explanation for the regularly observed killer whale chasing behavior from long-finned pilot whales in Icelandic waters. The movements of the 92s in conjunction with other killer whales during the subsequent interaction between them and the pilot whale group on 19 July 2022 do not fit any formerly observed behavioral patterns described for these antagonistic interactions (De Stephanis et al 2014;Selbmann et al 2022). It is possible that the movements of the killer whale group as a whole could have been influenced by an active effort of SN0540 to obtain another pilot whale calf through an approach of the pilot whale group, and the pilot whales may have reacted with a chase as a preventative measure to protect their young.…”

“…Antagonistic behavior of long-finned pilot whales toward killer whales has been documented in the Norwegian Sea, the Strait of Gibraltar, and the waters south and west of Iceland, with pilot whales moving toward and pursuing killer whales but never reaching them. In these encounters, the killer whales involved regularly exhibited nonaggressive avoidance behavior (De Stephanis et al 2014;Selbmann et al 2022). The avoidance behavior of the killer whales to the approach of pilot whales in Iceland could be divided into two categories--regular avoidance where killer whales moved away at low to moderate speeds with minorly evasive behavior and highspeed avoidance where killer whales porpoised out of the water as they were pursued by pilot whales in a chase (Selbmann et al 2022).…”

“…In these encounters, the killer whales involved regularly exhibited nonaggressive avoidance behavior (De Stephanis et al 2014;Selbmann et al 2022). The avoidance behavior of the killer whales to the approach of pilot whales in Iceland could be divided into two categories--regular avoidance where killer whales moved away at low to moderate speeds with minorly evasive behavior and highspeed avoidance where killer whales porpoised out of the water as they were pursued by pilot whales in a chase (Selbmann et al 2022). The proposed drivers of these interactions are resource competition, with both species exploiting similar resources (in Iceland possibly Atlantic herring, Clupea harengus Linnaeus 1758, or Atlantic mackerel, Scomber scombrus Linnaeus 1758) or anti-predatory strategies of the pilot whales toward the perceived threat presented by the presence of killer whales (Curé et al 2012;De Stephanis et al 2014;Selbmann et al 2022).…”

Call type repertoire of killer whales (Orcinus orca) in Iceland and its variation across regions

“…Only a small proportion of whales identified there could be matched to sightings in the recent wintering grounds off western Iceland (Samarra et al, 2017). Occasional sightings of killer whales in north and southwest Iceland, outside herring grounds, are also reported, especially during winter and spring (Selbmann et al, 2022). The sporadic nature of these sightings makes photo‐identification data from these areas scarce.…”

Harassment and killing of porpoises (“phocoenacide”) by fish‐eating Southern Resident killer whales (Orcinus orca)

“…Killer whales ( Orcinus orca ), the largest species of dolphin, are known to have complex interactions with other species, ranging from predation to avoidance (Jefferson et al, 1991; Selbmann et al, 2022), including hunting and killing nonprey. Southern Resident killer whales (SRKWs) are a small, well studied population of killer whale that range along the west coast of North America from southeastern Alaska to California with critical habitat that includes the Salish Sea, an inland sea shared by Washington State and British Columbia (National Marine Fisheries Service, 2021).…”