The Hourglass Dolphin: What Is Attracting Lagenorhynchus cruciger To The Antarctic?
The hourglass dolphin is a little known cetacean that is found in Antarctic waters. However, its is unclear as to why this dolphin has chosen or in fact evolved to have Antarctica as a habitat. This dolphin is one of only seven species of dolphin that inhabits the Southern Ocean surrounding Antarctica. Only a small number have been examined and they are rarely witnessed in their natural habitats. With such little knowledge of these animals, it is still unclear how they fit into their environment and what caused them to choose an extreme environment to call home. All this uncertainty is why they are becoming increasingly popular within the scientific community. Lagenorhynchus cruciger (L. cruciger), were first described in 1824 by Quoy and Gaimard with their characteristic black and white markings. The common name developed due to their markings being in the shape of an hourglass, with their length averaging around 1.5-2 meters. This animal has similar colour markings to none other than its cousin, Orcinus orca also known as the killer whale. The surprising thing is that there is very little known about this remarkable creature.
Where Are They Exactly?
As previously stated the hourglass dolphin is found in the Southern Ocean and have been seen around Antarctica. The map below shows the expanse that L. cruciger are believed to cover. However, with this vast area it is unclear whether this is either exaggerated or underestimated because there is very little physical evidence of L. cruciger and their migration patterns.
The distribution map (Figure 1) is based on both witness accounts and information collected by surveys.
Why Are They There?
In the paper published by Kasamatsu and Joyce in 1995 it was observed that there was a significant increase in L. cruciger in February, this increase was also seen by stated a possible explanation as to why L. cruciger are seen in higher numbers in February. It was thought it is due to warming sea surface temperatures and the seasonal increase in prey. From previous data sea surface temperatures in Antarctica are believed to increase from 1.04ºC to 1.37ºC between January and February. It is believed by Kasamatsu and Joyce that this temperature is more favourable for their thermoregulations. This is the process by which an animal retains its core internal temperature, in relation to their body shape and size.
This sea surface temperature increase in February is not the only increase seen in the Antarctic. There is an increase in the Antarctic krill, Euphausia superba (E. superba). The reproduction cycle of krill occurs between November and March with spawning and maturation occurring around late January into February. It believed that L. cruciger predates on fish, squid and crustaceans. The prey of L. cruciger feed on the large amounts of E. superba along with many other species. E. superba in turn bring an increase of larger more valuable prey. These are just two factors that are thought to cause an increase.
What Have We Got To Do Now?
With the Antarctic being one of the least researched areas in the world, which is due to the nature of the environment there it is extremely difficult to carry out research and to gain a valuable understanding about this part of our world. However, due to climate change and the effects it is having already, Antarctica is becoming yet more important because it is one of the environments where the change is seen and felt most prominently. Understanding how organisms are adapting to these sudden changes gives a greater insight as to whether or not they will be able to survive. Regarding the hourglass dolphin, it is unclear as to how they will be affected by climate change and whether or not they will be able to adapt. However, knowing more about this species could unlock a different understanding as to how animals are dealing with the changes that are occurring.