Surviving the cold

If you think that we have it tough in the winter and have an excuse to moan about the cold while we pass from one heated building to the next, bundled tightly in warm clothes and thick coats, then image how hard wild animals find it. There are no insects or berries for them to eat so food is scarce; there is little canopy cover in trees to hide from predators and keep the wind, rain and snow off them; and, to top it all off, they should be eating copious amounts of food just to keep warm!

Due to these rather brutal living conditions, animals have had to be clever in order to survive. Consequently,  they have had to perfect the use a range of physical and/or behavioural adaptations to give them the edge they need to keep one step ahead of the cold.

The most obvious of these adaptations are those that involve specialised behaviours, which typically involve migrating to warmer continents or hibernating through the inclement of winter until spring arrives, bringing  more hospitable weather with it and a much needed abundance of food!

Hibernation then, is essentially just a state of extremely deep sleep that aims to allow an animal to preserve as much energy as possible. In order to do this, a hibernating animal's brain activity drops to a very low level of activity (which is unusual for sleep) and their metabolism virtually stops - allowing them to save enough energy to survive until spring. The process is surprisingly efficient and, as such, scientists have recorded many species of animals that hibernate, although it is most commonly seen in mammals, such bears, bats and hedgehogs, and in certain species of insects, such as bumblebees.

Contrary to popular belief, most animals that hibernate do not sleep continuously and wake sporadically throughout their hibernation in order to defecate and (occasionally) to eat from their food reserves.  This photograph provides a good example of this, showing a doormouse hibernating with emergency hazelnuts close to hand.

For many animals however, hibernation isn't an option since it leaves such individuals very vulnerable to active predators and human disturbances, but they still lack the specialised physical adaptations (like thick coats) that are needed to keep them warm. These animals then, have chosen to simply 'opt out' of the cold winter months and migrate for thousands of miles each year until they reach warmer climates where food is still plentiful. Migration is particularly common in birds, such as house martins, swallows and swifts, and in many species of whale, such as humpback whales that can travel over 25, 000 kilometres a year!

Although many animals survive well using hibernation and migration, they are both extremely risky methods of enduring/avoiding the cold that are fraught with their own disadvantages, such as falling prey to storms while migrating over oceans and not being able to build up enough fat reserves in the spring to sleep through winter! Due to this, many animals not only opt to remain in cold areas, but chose to stay active and alert over the coldest months.

This has meant that many animals, especially species that live in the cold all year round, have evolved a wide range of physical adaptations that help to keep them warm. The most common of these, which has been mentioned above, is to posses a thick coat of fur (just look at the coats of wolves and reindeer), which acts as an excellent insulator against the cold by trapping layer of air above the skin. This layer of air gets warmed by the animal's own body heat and effectively acts as an electric blanket because it can't escape!

In addition to having a thick pelt that covers them, many animals that live in the cold have a thick layer of fat beneath their skin called blubber, which insulates heat and effectively acts as a 'blanket' that traps warmth inside their body. These layers can be extremely thick, with the 4 inch layer found in polar bears being a good example.

Many animals also possess other physical adaptations that are much less obvious since they involve internal changes rather than outside defences. A good example of this can be found in many species of fish that live in the Antarctic, which produce a natural 'antifreeze' in their blood that alters the way water molecules move in a manner that stops them from freezing. The antifreeze is made from glycoproteins, a very common class of biological 'building blocks' and is rather imaginatively called Antifreeze glycoprotein (AFGP), allowing fish to survive in extremely cold waters with a temperature far below 0C.

The wood frog, Rana Sylvatica, has a remarkable survival strategy to survive the winter and actually allows itself to freeze completely solid. As it freezes, the frog packs its cells with glucose and urea (found in urine), which helps to stop their cells from shrinking and splitting as they freeze. As much as 65% of their total body mass can freeze over winter; thawing out in the spring as if nothing has happened!

Many animals that live in algid climates also employ the use of specialised forms of mitochondria and enzymes, called isozymes or allozymes (depending on whether or not its gene is coded on the same chromosome as the original), which work much better at low temperatures than normal forms of enzymes do. Thus, the animal's body simply becomes better at functioning in the cold than it otherwise would have - providing them with a huge survival advantage.

In fact all animals, including humans, have many different isozymes and allozymes in their body that replace normal enzymes after spending a few weeks in a new climate. This is why we appear to 'get used to the temperature' when we move between seasons or go on holiday - unbelievably, we actually are getting used to it!

So there you have it - a few examples of the remarkable methods that animals have developed so they can  survive in (or avoid) the brutal conditions and biting cold of winter! I sincerely hope that you have enjoyed reading this post, along with all the rest in this blog, and hope that you continue to visit my site in the coming year! I already have a whole bunch of (hopefully) interesting ideas for articles and creature features planned for you!

Have a very Merry Christmas!

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!