Mammals are the most developmentally advanced group of animals. What distinguishes them from other vertebrates (such as reptiles, amphibians, birds and so on) are that they are wholly or at least partly covered in hair or fur, and that the mothers feed their young with milk from their mammary glands. All mammals are warm blooded (but so are birds) and must maintain their bodies at a constant temperature, different for each species but within the range 35 to 40 degrees C. The smallest mammals are just a few cm long and weigh little more than a gram, while at the other extreme the largest whales grow to 30 metres in length and can weigh up to 150 tonnes.
With a few notable exceptions, such as squirrels and rabbits, wild mammals are not easy to observe at close quarters and so field glasses are very helpful if not essential. Herbivores are usually the easiest to find and watch because they tend to live in colonies, while the carnivores are usually more difficult to spot and many of them are nocturnal.
Some marine mammals spend at least part of their time on land - seals, for example - while others such as whales and dolphins spend their entire lives in water and cannot survive very long if accidentally 'beached'. We are as short as can be without being entirely devoid of marine mammal pages - sorry! It's something we plan to rectify as soon as the opportunity arises.
Bats belong to the order Chiroptera, which means 'hand-winged'. (The tiny bones that support the wing membranes are similar in structure to the bones in our own hands.) There are known to be around 900 species of bats in the world; however, only about fifteen of these occur in Britain. The majority of Britain's bat species are either endangered or actually threatened by extinction. This threat is very real: the Mouse-eared Bat was declared extinct from Britain in 1991. Habitat loss and in some instances persecution born of human ignorance about the true nature of bats are major causes of the bat decline in Britain; farm and garden insecticides are almost certainly another key factor.
Apart from birds, bats are the only vertebrates capable of sustained flight. They are extremely manoeuvrable, even at low speed, which makes them very effective insect predators. In Britain we do not have to contend with vampire bats, and neither are there any giant fruit bats with 1.5 metre wingspan. What we do have are several species of insect-eating bats and they play important roles in the ecology of towns and countryside, not least in terms of pest control. A tiny pipistrelle bat can consume up to 3000 insects per night - and most of these are mosquitoes or tiny midges. In so doing there is no doubt they make the world a more hospitable place for the rest of us!
Most of the bats that occur in Britain belong to the family Vespertilionidae, the 'evening bats'; however, we also have two species from the family Rhinolophidae, the Horseshoe Bats, so-called because of a horsehoe-shaped plate of skin around the nostrils. They become torpid in winter, hibernating in roof spaces, hollow trees and dark caves. Hibernation is a useful characteristic since insect numbers are much reduced during the winter months. Although they are not blind, as some people may believe, insectivorous bats use echolocation to avoid obstructions when flying in the dark and to find their way to and from their roosts, and to home in on their prey.
Bats usually have just a single offspring each year, and depending on species they can live for up to 20 and exceptionally 30 years.
Grey Long-eared Bat - Plecotus austriacus
Soprano Pipistrelle - Pipistrellus pygmaeus
Nathusius's Pipistrelle - Pipistrellus nathusii
The numbers of some mammal species - several of the bats as well as the dormouse for instance - are so depleted that attempts to observe them could result in even more damage. British and European legislation provides protection for several mammal species, and anyone seeking to observe or study such animals should first become fully acquainted with the law.
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