No folks- it’s not an orca

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Commerson’s dolphins (Cephalorhynchus commersonii) are one of the lesser known species of cetacean. Bearing a striking resemblance to orcas at some angles, these dolphins are also known as skunk dolphins, piebald dolphins and panda dolphins.  They are usually between 4 and 5 ½ feet long and weigh up to 190 pounds, with females usually being slightly bigger than the males.  Similarly to Orcas, their colouring serves to camouflage them in the water and help them distinguish each other.

Distribution

There are two populations of commerson’s dolphin which comprise two subspecies. One population resides around the inlets of Argentina and into the Strait of Magellan close to Falkland Islands. The other population can be found around the Kerguelen Islands in the southern Indian Ocean. Dolphins spend a high proportion of their time in shallow waters but can also be found around harbours, rivers and bays.

Feeding Ecology

As in other dolphin species, commerson’s dolphins tend to hunt in packs, herding schools of fish into tight aggregations. Alongside fish, these dolphins are thought to consume shrimp, octopus, squid, marine worms and algae, taking a more opportunistic approach than other dolphin species. In addition, they are thought to consume significantly more food than other dolphins. Whilst dolphins are normally found in small groups of around 10 individuals, when hunting group numbers can reach around 100.

Behaviour

Commerson’s dolphins are very active and are thought to be migratory, following fish migrating in winter to reach warmer waters. One behaviour which has been noted in this species is upside down swimming.  Marine biologists believe this behaviour may help these dolphins to locate their prey by maximising their echolocation abilities, or to show each other their age and sex, which may be hard to distinguish otherwise. Highly social animals, commerson’s dolphins are often seen associating with the Burmeister’s porpoise, and the Peale’s and Chilean dolphins.

-Echolocation

Echolocation or biological sonar (Biosonar) is a sonar system employed by many types of animals including bats. The system helps animals both to navigate and to locate objects including prey.  To do this, animals will emit a call and listen to the echoes of the call that bounce off objects including prey items. The further away an object is, the longer it takes for the echo to reach the sender. In the case of dolphins, a clicking noise is used.

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Conservation

The commerson’s dolphin appears to be the most abundant dolphin in the genus Cephalorhynchus, however their conservation status is currently marked as ‘data deficient’ by the IUCN Red list. Threats to the dolphin have historically included hunting and capture for aquaria. Current threats and causes of mortality include accidental capture in nets and pelagic trawls.

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Jess Webster

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