20 August 2012

Ocean Giants

Throughout its history Earth has been home to animals of epic proportions. These monsters have included dragonflies the size of small planes, dinosaurs that were so big that the very ground trembled when they walked and huge land mammals such as the woolly mammoth, which were actually seen by early man! Most of these colossal animals are now extinct however, with only the occasional over-sized fossil being found as the the only indication that they ever even existed. Despite the loss of these species, Earth is still filled with giants and none are bigger and heavier than the whales. 

10: Gray whale - 45 feet/40 tonnes

The gray whale, Eschrichtius robustus, is the only surviving member of its family,  Eschrichtiidae, which first appeared  over 30 million years ago. Gray whales were nicknamed devil fish during the whaling era because of their violent behaviour when hunted.

Gray whales are famous for their 14, 000 mile (22, 000 kilometre) migration route that takes them from the Bering and Chukchi Seas in the summer to Mexico over the winter. This route was once believed to have been the longest migratory journey undertaken by any animal, but recent evidence now suggests that some humpback whales can travel even further!

9: Sei whale - 48 feet/45 tonnes

The sei whale, Balaenoptera borealis, is one of the fastest species of cetaceans (the family of whales, dolphins and porpoises) and has been recorded swimming at speeds of 30 mph (50 kph).

Sei whales need to consume nearly 1, 000 kilograms of copepods (small crustaceans), krill and zooplankton every day in order to meet their energy requirements. Sei whales are a type of baleen whale, which means that they eat by filtering the organisms out of the water as they swim. Sei whales can be found in most of the world's oceans, although they are not found in polar waters.

8: Humpback whale - 45 feet/48 tonnes

The humpback whale, Megaptera novaeangliae, is easily identifiable by its  knobbly head and unusually long pectoral fins. Male humpbacks produce one of the most complex songs out of any whale species, which can last for as long as 20 minutes and are often repeated for hours at a time. Although the function of their songs is not conclusively known, it is believed that they have a role in attracting a mate.

Humpback whales are one of the most wide-spread species of whale and can be found throughout the world's oceans. They have an intensive migration route and travel over 16, 000 miles (25, 000 kilometres) a year from the cold polar waters where they spend their summer to the tropical or subtropical waters where they breed and give birth in the winter.

7: Sperm whale - 50 feet/60 tonnes

The sperm whale, Physeter macrocephalus, is the largest living species of toothed animal and has the  largest brain of any animal in the world.

Sperm whales feed predominantly on giant squid, which they dive for to depths of up to 3 kilometres. This feat makes them the deepest diving animal and they navigate in the complete darkness using echolocation. The clicks that they produce  for their echolocation have a range of 60 kilometres and are the loudest sound produced by any animal.

6: Bowhead whale - 55 feet/75 tonnes

The bowhead whale, Balaena mysticetus, lives in the frigid waters within the Arctic Circle. In order to keep warm here the whale has a huge layer of blubber that accounts for up to 50% of its total body mass.

Bowhead whales are unique among mammals because their bones never fuse. This means that they keep growing throughout their entire lives and individuals as long as 70 feet have been found (although this post uses the average length of each species, else it would be higher up the list). Remarkably bowhead whales are believed to live for over 200 years due to their low body temperature and females have been found over the age of 100 that are still fertile!

5: North Atlantic right whale - 52 feet/100 tonnes

With only 400 individuals of the species left in existence, the North Atlantic right whale (Eubalaena glacialis) is one of the most endangered whales in the world. This is despite its protection under the Marine Mammal Protection Act of 1972 and the U.S. Endangered Species Act of 1973.

Like all right whales, North Atlantic right whales can be distinguished by their broad back that lacks a dorsal fin and the callosities (thickened skin) above its eyes.  They continuously feed on copepods and other small invertebrates such as krill, pteropods and larval barnacles by skimming them out of the water and migrate from the Gulf of Maine to their calving areas off Georgia and Florida in the winter.

4: Finback whale - 90 feet/74 tonnes

The finback whale, Balaenoptera physalus, is also called the fin whale, razorback whale or  the common rorqual.  It is  the second longest animal in the world, but its thin body means it is lighter than some species of much shorter whale.

Finback whales feed off schooling fish, squid, crustaceans and krill and are unbelievably fast. So fast in fact, that they are faster than the quickest ocean steamship! This attribute has earned them the esteemed title of being the 'greyhounds of the sea'.

3: Southern right whale - 58 feet/110 tonnes

The Southern right whale, Eubalaenna australis, is recovering well since it became protected in 1937 and is now classified as being of 'Least Concern' by the IUCN, with its population growing by an estimated 7% each year.

Southern right whales spend much the summer close to Antarctica where their calves are safer from being predated by killer whales and great white sharks. During the winter, when the conditions of Antarctica become too harsh for them to remain there, they migrate north to the warmer waters of Argentina and seem to spend many hours in a unique behaviour called 'sailing'. This behaviour is believed to be recreational and consists of the whales catching the wind in their flukes and letting it propel them through the water like  boats!

2: North Pacific right whale - 60 feet/120 tonnes 

The North pacific right whale, Eubalaena japonica, feeds mainly on copepods that it constantly filters out of the water while swimming. Its prey is so small that it needs to consume millions of them each day in order to provide the energy that it needs to survive.

Unlike many other species of whale, the North Pacific right whale does not seem to have a clear migratory pattern and the only notable annual difference in their distribution is when they are breeding, where they tend to move closer inland.

1: Blue whale - 100 feet/190 tonnes

The blue whale, Balaenoptera musculus, is a peaceful whale that eats krill - one of the smallest organisms on the planet. Although there were once believed to have been 200, 000 blue whales in the oceans, it is estimated that there are now only 10, 000 left due to their historical over hunting. Sadly, and despite now being protected, their numbers are not expected to recover due to their slow life cycles.

As far as we know the blue whale is the largest animal that has ever lived on this planet and is twice the weight of the biggest known dinosaur. In fact, blue whales are so big that their tongues alone can weigh as much as an elephant and their hearts as much as a small car!

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