What s the difference between hair and fur

A.� Biologically, they’re actually the same thing. Hair is one of a set of characteristics shared by all mammals. The only real difference is in the pattern of growth: all over if you're a dog or only in certain areas if you're human.

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Hair comes in two types: primary and secondary. Primary hair is typically longer and coarser than secondary hair and acts as a form of defence against insects and twigs. Secondary hair repels water and helps regulate body temperature and forms the fluffy coats that some mammals have.

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Apparently 'furry' animals have both secondary and primary hair. Polar bears, for example, have a dense coating of secondary hair to insulate themselves against the freezing temperatures of the arctic. But there are many animals that have only primary hair, for example humans and horses. A mammal's environment determines whether it has just primary hair, or a combination of primary and secondary.

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Q.� Why do humans have to have their hair cut but other mammals, like cats, don't

A.� Actually, many types of human hair won't grow infinitely. Hair length, like hair type, is specific to individual species, so that many different mammals have different hair lengths.

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Q.� When did hair first appear

A.� Hair is one of the defining features of mammals, but because it does not fossilise well, it's impossible to know when it appeared within the evolutionary lineage leading to mammals.

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Q.� Why did hair evolve

A.� The general theory is that hair evolved in tandem with another mammalian characteristic: warm bloodedness, the ability to produce internal body heat, known as 'endothermy'. Generating your own body heat is costly in terms of energy, it wouldn't make sense for a mammal to then loose it: hair acts as a very good insulator.

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Q.� Are whiskers hairs

A.� Yes they are. Whiskers are hairs that work as sensory receptors; they have special nervous connections that make them highly sensitive to movement. Whiskers are just one of the many types of modified hair. A porcupine's quills are actually enlarged hairs.

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Q.� Do whales and dolphins have hair

A.� Yes, but very little. They are born with a few bristles, normally on the back of their heads, which many loose within a few days. However some whales keep these bristles and it’s possible that they act as sensory receptors, like cats whiskers.

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