Orca

Orcinus orca is a toothed whale of the family Delphinidae ^[1]. It is the largest of all dolphins: it can reach up to 32 feet, about 9.8 m, and weigh up to 11 tons, and its diet is the most varied of any cetacean ^[2]. In Peru it is called «orca», and the management plan of the Reserva Nacional Mar Tropical de Grau counts it among the 13 cetaceans seen in the Cabo Blanco – El Ñuro sector ^[3].

For a long time its records in Peruvian waters were scarce and mostly anecdotal ^[4]. A 2019 study gathered 29 reports from 2003 to 2018, involving at least 110 animals, and concluded that the species is more frequent in Peru than had been documented ^[5].

Linnaeus described it in 1758 as Delphinus orca, in the dolphin genus; today it sits in a genus of its own, Orcinus ^[1]. Since then it has received many other scientific names: the World Register of Marine Species lists 38 synonyms, among them Orca gladiator and Orcinus glacialis ^[1].

That long list reflects a question still open. In 2010 it was regarded as a single cosmopolitan species, but a study from that year that sequenced the complete mitochondrial genome of 139 samples proposed giving species rank to 3 of its ecotypes and treating the others as subspecies until more data are gathered ^[6].

Its colour pattern makes it unmistakable: the back is almost entirely black, the belly white, and there is a white patch near each eye; behind the dorsal fin it also carries a grey or white saddle-shaped patch whose design changes from one individual to another and between populations ^[2]. Adult males grow much larger pectoral fins, dorsal fin and tail flukes than females, and a thicker body as well ^[2].

Those markings make it possible to recognise each animal. An adult male photographed off Los Órganos in October 2017 was identified by the shape of the patch behind his right eye, which earned him the nickname Phantom, by his straight, slightly wavy dorsal fin with its tip bent to the left, and by a notch on the left side of his flukes ^[7].

It lives in every ocean. It is most abundant in cold waters such as those of Antarctica, the North Atlantic and the North Pacific, but it also occurs in tropical and subtropical seas; its world population is estimated at about 50,000 animals ^[2].

Between 1995 and 2003, cruises of the Instituto del Mar del Perú recorded it on 13 occasions over 39,060 nautical miles of search effort, and 7 further records brought the total to 20, from 4° 59′ S to 18° 19′ S ^[4]. Of the 13 IMARPE records, only 3 were over the continental shelf, and most were in water warmer than 20 °C, with a mean of 20.81 °C; because such warm water is unusual in the cold Peruvian Current, the author suggested that these killer whales might come from oceanic populations of the Eastern Tropical Pacific ^[4].

The 29 reports gathered between 2003 and 2018, by contrast, were concentrated over the continental shelf or near its edge ^[5]. The management plan of the Reserva Nacional Mar Tropical de Grau notes a recurrent presence of killer whales in the region, above all off Punta Sal ^[3].

It is highly social. Most animals live in groups of relatives along the maternal line, ranging from a few to 20 or more whales, and larger temporary gatherings sometimes form to socialise, mate or exploit concentrations of prey ^[2]. It communicates with clicks, whistles and pulsed calls; the pulsed calls are learned culturally and work as an identity badge for each family ^[2].

Females reach sexual maturity between 10 and 13 years of age, gestation lasts 15 to 18 months and a single calf is usually born, in any month of the year ^[2]. Calves suckle exclusively for at least a year and stay beside their mother for at least the first 2 years; males live about 30 years on average and at least 60 at most, and females about 50 years on average and at least 90 at most ^[2]. Together with humans and a few other cetaceans, such as the false killer whale and the beluga, it is one of the species in which menopause is known ^[2].

Killer whales form ecotypes that share areas but do not interbreed, and that differ in appearance, diet, habitat, genetics and behaviour ^[2]. Analysis of complete mitochondrial genomes showed that each known ecotype forms a lineage of its own, split from the others between about 150,000 and 700,000 years ago ^[6].

It is a top predator that often hunts as a team. Depending on the ecotype it eats fish, such as salmon or sharks, or else marine mammals and squid, including sea lions, porpoises, dolphins and other whales ^[2].

In Peru it has been seen hunting other marine mammals. In March 2001, off the central coast, 6 killer whales encircled and chased a group of 15 pilot whales; in February 2002, off Punta Falsa, a group of 8 pursued some 200 bottlenose dolphins and killed one; and in January 2003 a lone male caught 4 fur seal pups on the beach at Punta San Juan ^[4]. Between 2003 and 2018, 8 more cases of predatory behaviour were documented, on humpback whales, blue whales, South American sea lions and fur seals ^[5].

Humpback whales off northern Peru also show traces of these attacks: of 897 individuals photo-identified from 2009 to 2017, 19.6 %, that is 172, had rake marks left by killer whale teeth on their flukes ^[5]. The male Phantom, seen in Mexico, Costa Rica, Ecuador and Peru, turned up almost always during the humpback breeding season, and in Ecuador he was seen attacking a humpback calf; in Galápagos he also attacked a Bryde's whale and, with other killer whales, green turtles ^[7].

The IUCN Red List classifies it as Data Deficient ^[8]. It is listed in CITES Appendix II, and its threats include entanglement in fishing gear, food shortage, chemical contaminants, oil spills and disturbance from vessel traffic and noise ^[2].

In Peru, Resolución Ministerial N.° 451-2019-PRODUCE lists it in its annex among the smaller cetaceans, for which the minimum approach distance is 50 m, and 150 m when they are feeding or socialising; for cetaceans longer than 5 m it sets 100 m, and 300 m when they are feeding or socialising ^[9]. The same regulation forbids heading for or approaching groups of cetaceans with calves and requires any collision or entangled animal to be reported to IMARPE and the maritime authority ^[9].

Not medical advice. For a sting, a poisoning or an allergy, seek medical care.

As a top predator it accumulates contaminants that can harm its immune, nutritional and reproductive systems ^[2]. In a meta-analysis of more than 1000 European cetaceans, killer whales were among the 3 species whose mean blubber PCB levels far exceeded every known toxicity threshold for marine mammals, and some small or declining populations in the northeast Atlantic had few new calves, which fits reproductive harm from those compounds ^[10].

In the past it was the target of commercial hunting and of culls to protect fisheries, and its live capture for display in aquariums still continues around the world ^[2].

In northern Peru, the company Pacifico Adventures has documented that a third of the cetaceans recorded in the country can be seen in the area, and has highlighted its importance for highly migratory species such as the killer whale ^[3]. It was on a whale-watching trip from Los Órganos that the male Phantom was photographed in 2017, and his pictures were then compared with catalogues from Mexico, Costa Rica, Colombia and Ecuador ^[7]. Artisanal fishers and tour operators also report killer whales at various points along the coast, although those records have not been confirmed ^[4].

On the records from 1995 to 2003, its presence in Peru looked low, typical of dispersed predators arriving from neighbouring waters ^[4]. The 2026 management plan of the Reserva Nacional Mar Tropical de Grau notes its recurrent presence mainly off Punta Sal, and regards the north of the country as an important feeding area for the species, which apparently hunts humpback whale calves ^[3].

On 6 October 2017, off Los Órganos, a lone male followed a humpback mother and her calf during a whale-watching trip ^[7]. If a group with calves is encountered, Peruvian regulations require moving slowly away until at least 300 m off ^[9].