The need to adapt
Previous chapters mentioned the need for animals to adapt to the changes in their environments. This is because some changes can threaten the chances of an animal's survival. In general terms, the three main threats to survival are temperature, lack of water and lack of food. Outside of environmental threats, many animals also need to be able to defend themselves from predators in order to survive.
Many animals have adapted over time, allowing them to better cope with the threats they face as a regular part of their lives. Some types of adaptation may change the physical characteristics of an animal; other adaptations may be a change in behavior.
There are some environments that are naturally hot or cold, and the animals that live in them have usually adapted over time in order to be able to survive more comfortably. Polar bears in the Arctic have thick fur that helps them to keep warm on land and a layer of fat under their skin to help them keep warm when they swim in the cold water.
Many desert dwelling animals are more active at night-time when it is cooler, rather than during the hot days. Animals that are active at night are called nocturnal.
Lack of water
There are many environments around the world in which water can be scarce. These can include deserts, very cold regions and areas in which water sources are polluted. The camel is a prime example of an animal that has adapted to living in regions with limited water supplies.
Australia actually has many camels living in remote areas. These animals were originally introduced to the country by people who wanted to transport goods through dry and desolater areas. Today some people estimate that there are between 500 000 and 1 000 000 feral or wild camels living in Australia.
Camels are famous for having one or two humps. A one-humped camel is known as a dromedary, and two-humped camels are called Bactrian camels. Even though many people believe that a camel's hump is used to store water, the truth is that the hump stores fat. This fat can be used as energy when the camel needs it and the hump will shrink and sag as the fat supplies are used up.
Camels are actually able to survive for over a week without any water and can survive for months without eating. When they do find water, they can also drink a lot. A thirsty camel can drink over a hundred liters in just a couple of minutes.
Lack of food
Some animals can be threatened by a lack of food in their environment. This can be a result of weather conditions like drought, or perhaps other animals have eaten all the food in an area. Sometimes this is caused by humans removing native vegetation to build houses or farms on the land.
Sometimes the food an animal eats is available, but it is difficult to reach. The echidna is an excellent example of an animal that has adapted to be able to catch and eat its favorite food, ants. The echidna has a long snout and powerful front arms that it uses to dig into hollow logs or anthills. It also has a long and sticky tongue that can extend about 15 centimeters past the end of its snout.
Sometimes the echidna will lie near an anthill, stick its tongue out and wait for ants to walk across it. It can do this for a very long time.
Some animals also adapt in order to be able to defend themselves from predators. Some are able to run quickly to escape; others change color in order to hide. The echidna is protected by a coating of thick spines.
Echidnas are sometimes eaten by dingoes and goannas. It is also believed that they may be hunted by foxes. When they are approached by something threatening, they will often curl into a ball, leaving only sharp spikes pointing out toward an attacker. Sometimes they will scrape a small hole for its soft belly in the ground.
There are many ways in which an animal can adapt to the environment around it. Sometimes different animals living in the same area will have similar adaptations. Sometimes the same animals will have different adaptations in different areas. Some of the more common adaptations of animals include:
- Hibernation – some animals will hibernate or 'sleep' through the coldest part of the year. Bears are one of the best-known examples of this.
- Migration – some animals will move from one area to another as the weather becomes too hot or cold. Sometimes they will travel in order to find new sources of food.
- Molting and shedding – some animals grow thick coats of fur to keep warm through winter. Often they will shed this coat when the weather starts to warm up again.
- Changing color – some animals will change their color or markings to blend into their surroundings.
Can you think of any other ways in which an animal might change or adapt to suit its environment?
Even though the circumstances in an environment can change quickly, it usually takes some time for a change to become permanent. This means that most environments change slowly. This gives the animals that live in them time to slowly change as well.
Sometimes the process of change can take place over many generations of animals. Minor changes can be passed from parents to children, and a series of small changes can build up into adaptation