Sperm Whales React to an Attack by Killer Whales

Abstract

Killer whales or orcas, Orcinus orca, are known to prey occasionally upon members of larger whale species, including sperm whales, Physeter macrocephalus (Hoyt, 1981; Martinez and Klinghammer, 1970). Despite several references in the Russian literature, Berzin (1972) considered the reports to be too rare for killer whales to be "branded serious enemies of the sperm whale." Schevchenko (1975) stated that, in the Antarctic, 65.3% of sperm whale carcasses examined showed signs of killer whale tooth marks, although he did not say if or how he differentiated between marks of killer whale teeth and those made by other sperm whales. Yukhov et al. (1975) found remains of sperm whales in killer whale stomachs in the subtropical and temperate waters of the southern hemisphere, and mention a movie-film showing an attack by a group of killer whales on a school of female sperm whales and their calves. However no description was given. We report here observations made during an encounter between a group of sperm whales and a group of killer whales off the Galapagos Islands, and the subsequent flight of the sperm whales from the area of the attack. During the early part of 1985, we used the 10-m sloop Elendil to follow groups of sperm whales west of the island of Isabela (1*00'S, 91*00'W) in the Galapagos Islands, Ecuador. The methodology employed was based on that described by Whitehead and Gordon (in press). The groups of whales were tracked acoustically using a directional hydrophone at night, and acoustically and visually during the daytime. Sperm whales could be heard at about 8 km using our acoustic equipment. Whenever possible, photographs of dorsal fins and flukes were taken to identify individuals from distinctive marks and scars. At 5-min intervals we recorded the compositions, relative positions, speeds (estimated by comparison with nautical speedometer on boat), headings, and behavior of each visible subgroup. A subgroup constituted a set of whales swimming in a coordinated manner, each less than 100 m from its nearest neighbor within the subgroup. Except in exceptional circumstances, once each hour on the hour an acoustic recording was made through an omnidirectional hydrophone lasting 5 min. The steady click (at about 1 click per second) of the sperm whale is an indicator that the sperm whale is feeding at depth (Whitehead and Gordon, in press). In the following, "many clicks" indicates that we were hearing the output of roughly 10 or more sperm whales. Depth sounder traces of diving whales were obtained when possible. Positions were from a satellite navigator. The encounter between the sperm whales and the killer whales occurred between 0945 and 1230 h local time (GMT-6 h) on 18 April 1985. The observations were divided into five periods: 1. The day before the encounter; 2. The night before the encounter; 3. The morning just before the encounter; 4. The encounter; 5. After the encounter. Analysis of photographs showing individually identifying marks indicated the same group of animals to be present throughout the...

An Unusual Reaction and Other Observations of Sperm Whales Near Fixed-Wing Aircraft

“…The characteristic responses to killer whales are individuals coming to the surface, swimming fast toward one another, and clustering actively and tightly (Whitehead 2003), similar to the behavior we observed. The semi-circle "fan" formation we describe is similar to defensive "marguerite"-and "spindle"-like formations reported by other researchers (Nishiwaki 1962, Berzin 1971, Arnbom et al 1987, Weller et al 1996, Pitman et al 2001. Weller et al (1996) observed open-mouth behavior (akin to our observation) by sperm whales, and interpreted this as a discrete distress response to harassment by short-finned pilot whales, based on obvious distress behavior reported by other researchers.…”

“…This interpretation is based upon behavioral events displayed by sperm whales in situations of distress, reacting to perceived or actual threats, such as killer whales (Orcinus orca) (e.g., Arnbom et al 1987, Pitman et al 2001, false killer whales (Pseudorca crassidens) (Palacios and Mate 1996), short-finned pilot whales (Globicephala macrorhynchus) (Weller et al 1996, Pitman et al 2001, sharks (Best et al 1984), whalers (Nishiwaki 1962, Caldwell et al 1966, Berzin 1971, and vessel approaches (Palacios and Mate 1996). The characteristic responses to killer whales are individuals coming to the surface, swimming fast toward one another, and clustering actively and tightly (Whitehead 2003), similar to the behavior we observed.…”

Video-documentation of a killer whale (Orcinus orca) predatory attack on a giant manta (Manta birostris) in the Galápagos Islands

“…The first documented observations of killer whale predatory behavior in the Galápagos Islands involved sperm whales (Physeter macrocephalus) and Bryde's whales (Balaenoptera edeni) (Arnbom et al, 1987;Brennan and Rodríguez, 1994). Since then, a review of killer whale occurrence in Galápagos has revealed not only the nearly ubiquitous (albeit highly unpredictable) presence of this species throughout the islands, but also the broad array of marine vertebrates upon which they prey, which includes teleost and elasmobranch fishes, sea turtles, otariids, and cetaceans (Merlen, 1999).…”

Patterns of kinship in groups of free-living sperm whales (Physeter macrocephalus) revealed by multiple molecular genetic analyses.

“…Within groups there appears to be both communal suckling (5,6) and communal protection of the young from predators (7)(8)(9). As well, females have frequently been observed to display considerable altruism toward injured group members (8).…”

“…where a is the mortality of males over the age of [7] Confidence intervals for d were calculated using binomial theory.…”