Mysteries of Antarctica: The Commerson’s Dolphin
For hundreds of years explorers and scientists have discovered, described, and classified a myriad of species inhabiting the waters and continent of Antarctica. Considering its inaccessibility and unforgiving nature, this is a highly impressive feat, no matter the era. However, despite the many grueling hours spent sorting through nets of strange, undescribed species of sea creatures and walking through fields of angry, smelly penguins in order to describe breeding behaviors, there have been a few species that have managed to slip through the scientific cracks. The Commerson’s dolphin, a rare species of Antarctic marine mammal, is one of many species that has managed to elude the inquisitive eyes of scientists for nearly 300 years.
An Accidental Discovery
You may know them by a few different names. Piebald dolphin, skunk dolphin, or even panda dolphin are names given to this distinctly black and white cetacean since its discovery in 1767 by French naturalist Philibert Commerson. Commerson observed these playful dolphins breaching water alongside the ship whilst cruising through the Strait of Magellan in an attempt to circumnavigate Antarctica, and immediately recognized them as a new, undescribed species. Like most discoveries of new species, this occurred completely by accident! Since their discovery, there has been very little described about them in the ways of biology and ecology. Currently, little is known about the actual population size of the dolphins. Their geographic location and general elusive nature make them an especially difficult species to study for long periods of time. Despite some of the best efforts, they still manage to remain an enigmatic animal.
Commerson_Dolphin © Mirko Thiessen_CC-BY-SA-2.5
What Do We Know About the Commerson’s Dolphin?
Commerson’s dolphins are one of the smallest species of cetaceans, and grow only to a length of 1.5 meters (5 feet) at full maturity. Their appearance is unmistakable, with a bold black and white coloration that distinguishes them from all other species of marine mammal. Unlike other species of dolphins the Commerson’s dolphin lacks a rostrum, or characteristic “beak”.
Varieties of Commerson’s Dolphins
There are two recognized subspecies of Commerson’s dolphin in the world. The main subspecies, Cephalorynchus (Greek for ‘head snout’) commersonii commersonii is found around inlets of Argentina, Tierra del Fuego, and amongst the Falkland Islands. The second subspecies, Cephalorynchus commersonii kerguelenensis has managed to establish an extremely small population in the shallow waters off the coast of South Africa near the Kerguelen Islands. How did these two genetically identical species become separated over a distance of 8,500 kilometers (5,300 miles)? Reasons for this unique distribution are unknown to scientists, but may have occurred when a small group of dolphins swam a little too far northeast in the Antarctic Circumpolar Current. The only noticeable difference between the two subspecies is their coloration. Kerguelen dolphins are much lighter shades of grey and black than their Argentinean counterparts.
It’s a bit difficult to tell male and female dolphins apart just by looking at them from above, but luckily for the Commerson’s dolphins, evolution has provided a quick an easy way to tell the two apart. Males have a teardrop-shaped black blotch on their bellies, while the females’ blotch is much more round. Both sexes will reach full maturity between six and nine years of age. Courtship, mating, and birth all occur between the months of September and February. Gestation lasts for approximately 12 months, after which a single calf is born.
Like many other species of cetaceans, these dolphins’ diets consist primarily of shrimp, octopus, various species of fish, and even marine worms! Together, groups of dolphins will gather and herd schools of prey so that they are all able to eat together. This is referred to as cooperative hunting, and can include groups of up to 15 dolphins at a time.
There are only estimated population numbers based on very little data for the Commerson’s dolphin. The last comprehensive census occurred in 1984 in the Strait of Magellan, where only 3,400 individuals were estimated to inhabit. No other comprehensive census has occurred in this area since then. Due to their estimated low population size, these dolphins are red listed as a threatened species throughout their range. There are many different conservation measures in place to ensure these dolphin’s, and other marine species, population size doesn’t decrease over time. Efforts including ocean pollution reduction and the enforcement of strict commercial fishing regulations are incredibly important to the preservation of this species. Additionally, anti-poaching framework is in place to prevent unregulated hunting of these dolphins for their meat at oil. Unfortunately, these regulations can be difficult to enforce, especially since the Southern Ocean is a vast and wildly uninhabited environment.
Where to See Commerson’s Dolphins
Considering their supreme secrecy in the waters of the Southern Ocean, the Commerson’s dolphins can be extremely difficult to spot during an Antarctica trip. Cruises around the Falkland Islands will be your best bet on seeing one of these amazingly rare and curious creatures. Make sure to keep a careful eye out!