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.

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.

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.

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.

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.

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.

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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