The difference between night and day (From Durham Times)

The difference between night and day

8:40am Friday 18th May 2012 in Looking Back By Jim Cokill

Durham Wildlife Trust recently ran a Dawn Chorus event, but despite the best efforts of the birds the star of the show was not ornithological.

A special guest appearance by an otter, with support from a fox and roe deer, was what made the event so memorable.

It is always rewarding to see wild mammals because for most of us, even with abundant species such as roe deer, it is an unusual occurrence. Wild mammals are wary of people, and even more wary of the dogs that often accompany us into the countryside, but the main reason people seldom see the mammals that are quite literally on their doorstep is that we are not looking at the right time of day.

Humans are creatures of the light, being active during the day and sleeping at night.

The scientific term for this is diurnal. Many insects and plants follow this diurnal pattern of behaviour, as do some other mammals, but others favour an alternative lifestyle.

The opposite of diurnal is of course nocturnal, and bats are the best known of our native nocturnal animals.

They have evolved adaptations to low light levels making them nocturnal specialists, but other animals adopt nocturnal habits in response to the environment around them; human disturbance being a significant factor.

The third category of behaviour is crepuscular – active during twilight. Some crepuscular animals are matutinal and out at dawn, some are vespertine and active at dusk and some do both.

Our star otter was matutinal, but otters can be diurnal, nocturnal or crepuscular depending on the circumstances.