Some of what defines a mammal is its ability to breathe air. This is true even of the marine mammals. The cetaceans (whales, dolphins, porpoises), of which, lead a wholly marine existence, leaving the land some 50-60 million years ago. They evolved extreme adaptations to survive life in the water but will always be tied to the ocean surface for need of air (Hozel 2002). Of course there are vast differences between conditions deep in the ocean and those at sea level. One family of cetaceans has truly conquered existence between these two worlds: the beaked whales.
In 2014 Cuvier’s beaked whale was publish as being recorded diving at 2992 m for 137.5 minutes (Schorr et al. 2014). This time still holds the record for the deepest recorded foraging dive of any mammal. This blog will explore the adaptations that allowed this dive to take place, the reasons why it took place and the dangers surrounding deep diving. But firstly…
What is a beaked whale?
Little is known of the beaked whale family Ziphiidae. For many centuries all we knew of them was from dead specimens, beached up on the shore. They were confused for some form of cryptozoological creature; the most famous perhaps, being the “Moore’s Beach Monster” of 1925 (Fig 1). An alleged plesiosaur, not unlike the creature believed to inhabit the waters of Loch Ness. We know now this “monster” was in fact the decomposed carcass of a Baird’s beaked whale (Long 2014). But with few accounts of a living animal being seen (Gervais’ beaked whale exists on the British cetacean list based on one sighting alone in 1840) there was little for the public to compare the carcass to, other than that of plesiosaur fossils (Dunn, Still et al. 2012).
Our knowledge of the Ziphiidae family has greatly increase since then. Although still, in comparison to other cetacean families, this family remains cryptic and difficult to study (Tyack, Johnson et al. 2006). Up to now we have recorded 22 species, two of which (Perrin’s beaked whale and the pygmy beaked whale) were only identified in the past 25 years, which categorize into five or six genera. They range widely in size from 3 metres (~300 kg) to more than 10 metres (12 tonnes) (Madsen, Aguilar de Soto et al. 2014). They belong to the suborder Odontoceti, the toothed whales. However, unlike their namesake, the beaked whales exhibit an extreme lack of teeth, a characteristic that further fueled cryptozoological claims. Only the Shepard’s beaked whale (Tasmacetus shepherdi) retains it’s full set of teeth. Some ziphiids, namely the bottlenose whale (Hyperoodon spp.) (Fig 2) and Gray’s beaked whale (Mesoplodon grayi) display vestigial teeth although, from what has been observed, these are used for male-male interactions (Dunn, Still et al. 2012, Madsen, Aguilar de Soto et al. 2014, Hozel 2002).