Unusual teeth of rare whale more ‘oddity’ than evolutionary throwback

Scientists are excited after a rare whale was found with an extra set of teeth, but we don’t know enough about the elusive species to call it an evolutionary throwback yet.
By Shannon Verhagen May 17, 2016 Reading Time: 2 Minutes

A RARE WHALE that washed up on a South Australian beach earlier this year is not only providing a unique insight into the species, but also exciting scientists with its unusual dentition.

The deceased whale was found on Waitpinga Beach – about 100km south of Adelaide, near Victor Harbor – in February, before being taken to the South Australian Museum for study.

It has now been identified as a Hector’s beaked whale (Mesoplodon hectori), however its unusual dentition initially made identification difficult.

The 3.6m juvenile female specimen had two teeth protruding above its jawline – a trait generally only seen in male beaked whales.

Hector's beaked whale

Museum staff dissected the whale on Waitpinga Beach.

“In female beaked whales, they have two teeth in the bottom jaw – but they never erupt through the jaw,” explained Catherine Kemper, senior research scientist at the South Australian Museum. “In adult males they do erupt, and are probably used for fighting,” she added.

The finding was initially reported as an ‘evolutionary throwback’ or atavism, where features of an animal or plant that have been lost and become ‘silent’ in the species’ evolutionary history are for some reason – generally a mutation – reactivated.

However, Catherine said ‘oddity’ is a better word, because with as little as about 30 Hector’s beaked whale specimens having been found throughout its Southern Hemisphere distribution, there is a chance the trait is present in more individuals.

Rare insight into elusive species

While the whale may not be exhibiting long-lost prehistoric characteristics, Catherine said it’s still exciting to have a specimen of such a poorly known species.

These elusive cetaceans are known only from about 30 strandings and a single sighting – with this being only the fourth specimen found off South Australia’s coast.

“When dealing with species so rare, amazingly, even one animal can tell us a lot more about the species,” Catherine said.

Hector's beaked whale teeth

Teeth pulled from the deceased female whale’s skull intrigued scientists and made headlines, but could me more common than we think.

Squid beaks in the whale’s stomach provided insight into its diet, while the incomplete fusing of its spinal cord indicated its juvenile age, helping determine when the animals reach adulthood.

With records from Australia, South Africa, South America and New Zealand, Hector’s beaked whales are believed to inhabit the Southern Hemisphere’s cool, temperate waters, and Catherine said the timing of these strandings – mostly in summer –  is also an important source of information.

“Something is probably bringing them closer to the shore at that time of the year – whether that be breeding or feeding,” she said.

With so little known about this species, Catherine added that she hopes the information they uncover will help conservation of these elusive creatures.

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