Cornwall Mammal Group
Recognition:
During 1998 when there were unusually large aggregations of basking sharks off the south coast, a pod of three orcas was sighted on several occasions in the vicinity, and there is a past report of two orcas attacking and killing a basking shark off Porthcurno. In 2011 there was a minor media panic when a mother and calf were reported close to the shore near Padstow. Despite fears to the contrary, no surfers were eaten.
Maybe our most iconic and recognisable cetacean, the killer whale, or orca, is actually the largest member of the dolphin
family. It has a robust body with a blunt head, wide, paddle-like pectoral fins, and distinctive black and white markings. The
majority of the body is black. The chin, chest, and belly are white and there is an elliptical white patch just behind the eye and a grey ‘saddle’ just behind the dorsal fin. The underside of
the tail flukes are also white. The dorsal fin in males is upright and triangular and may be 2 m height, in females and juveniles it is shorter and more curved. They are highly intelligent and adaptable animals with complex behaviours, especially hunting, which may vary in different parts of the world. Otherwise, commonly observed behaviours include fin slapping, breaching, lobtailing, spyhopping and logging. Two different types of orca are recognised in some areas of the world: ‘resident’ and ‘transient’. Resident orcas have a smaller home range, live in larger family groups and specialise in feeding on the prey found in their home range to the extent that other potential prey is ignored. Transients tend to roam over a larger area either alone or in small pods and have a more varied diet, often including marine mammals. Globally, there are significant
genetic, morphological and behavioural differences between some populations so that several subspecies of orca have been proposed and up to three different species suggested.
The orca occurs in many different habitats, from open ocean to fjords, estuaries, inland seas and coastal zones. Despite its wide distribution, most sightings are within 500 miles of a coastline. Animals move seasonally and locally, probably linked to prey, but longer migrations have not been recorded.
The orca’s success is due to its adaptable nature: a wide variety of prey are taken including fish and squid, birds, sea turtles, sharks, and marine mammals. Some orcas cooperate to separate the calves of species as large as the blue whale from their mothers, before repeatedly forcing them underwater to drown. Smaller cetaceans are killed by being knocked high out of the water using their head or tail. Pods assemble at breeding colonies of seals and sea lions to target the pups as they enter the water, and they may even rush up on to the beach to grab an unsuspecting victim. Older members of the pod teach their calves this technique, before returning their prey to the beach (relatively) unharmed! Around the UK, orcas are thought to feed mainly on fish and the occasional marine mammal.
Males mature at around 15 years, and females at about 9 years. They give birth to a single calf measuring between 2 and 2.5 m following 15 to 18 months gestation: the calf will be dependant for up to 2 years. Calves are born at 3 to 9 year intervals. The mother will teach her offspring any specialised behaviours that she has developed, or been taught by her own mother. Life expectancy is at least 90 years and adults can reach 5.5 m for females, or up to 9.8 m for males.
Threats to orcas may result from disturbance and pollution, especially PCBs. Decreased food supply may cause some pods to move to other areas or extend their home range. Orcas are hunted for food in some parts of the world, but also captured and trained to perform for audiences. The ethical debate over keeping these animals in captivity has been ongoing for decades. The opportunity to get close to these
creatures, to observe their intelligence through the performance of a trained routine, and for them to act as ambassadors for their species so that we can learn more about them and therefore better conserve them in the wild, is weighed against examples of poor care, shorter life spans, poor breeding success, and attacks on human trainers.
Survey Methods:
Different pod types require different survey systems. Land and boat-based surveys can be productive. For resident pods regularly using certain areas, underwater cameras and microphones have been successfully employed over extended periods. This has been useful in recording interactions between and within pods.
© F Ugarte - Sea Watch Foundation
© F Ugarte - Sea Watch Foundation
Conservation:
There is no global population figure for orcas but regionally most subpopulations are
suspected to be in the hundreds or low thousands, in Antarctica there are estimated to be 70,000, with a further 14,000 around the Pacific rim. In the UK the species is protected against intentional harm and disturbance under the Wildlife and Countryside Act 1981.
Did you know?:
The film Free Willy was based on the experience of Keiko (meaning ‘Lucky One’).
Born in 1976 off Iceland and captured in 1979 he was sold into the marine park industry. After almost 20 years Keiko was released near Iceland, but he did not reintegrate with wild pods and he moved over 1000 miles to Norway. He became a local tourist attraction in Taknes Fjord and died in 2003 from pneumonia.
Distribution:
In most years a few are
seen around Cornwall
coinciding with the
summer influx of
basking sharks. Around
the UK they are commonest around the north of Scotland and the islands. Southern sightings are more sporadic. Found in every ocean, the orca is one of the most wideranging mammals, preferring the cooler polar waters rather than tropical or subtropical areas.
Records:
2007-2012: 7
2002-2007: 46
Pre-2001: 256
Total: 309
