Why Mysterious Mammals?
(Photo: Soprano Pipistrelle, Pipistrellus pygmaeus). This survey allows users to submit sightings of most of Ireland's terrestrial mammals. Some are native (here since the last Ice Age, 13,000 years ago) and some have been introduced by Man. A few species escaped from captivity and are now breeding successfully in the wild (feral). The term 'mysterious' seemed apt for the project as the mammals of Ireland have presented us with many intriguing problems.
For example, when and how did they arrive on the island of Ireland? In a modern context, their distribution is frequently a mystery, mainly because
of pressure from our changing use of the land and the destruction of their habitats. The removal of a hedgerow or a short part of it, for example, can destroy the homes and/or hunting grounds of shrews, mice and hedgehogs.
For many of us, their 'shyness' has created quite a mysterious air about their lives. Many of us are sharing our habitat with mammals such as bats, mice, shrews, hedgehogs, badgers and we remain unaware of them. A recent survey on Biology.ie has shown how the Pine marten has extended its range, moving into parts of the country where they were formally unknown.
A bit of Mammalian History
They first appeared on Earth about 200 million years ago. Then, it is speculated, they were tiny shrew-like, insect eating nocturnal creatures, hiding from the habitat-dominating dinosaurs. No doubt they were planning the eventual demise of those reptiles. Their day did indeed come, probably not because of their own innate success initially, but because of the demise of the dinosaurs.
With the dinosaurs gone, Mammalian success was probably due to the one critical factor that distinguished them from reptiles: there were warm blooded, and very warm-blooded at that. Further, that high body temperature could be regulated. The more evolution equipped mammals to maintain a high body temperature, the more successful they became. Body temperature was kept constant by fur, hair and the versatile sweat gland. The brain developed to control these new artifacts.
The versatile sweat gland, (the target of a huge cosmetic industry today) evolved as an excretory organ, an organ of nutrition (the mammary gland or breast), and an organ of scent.
When/How mammals arrived in Ireland?
Many a scientific paper has been written, and even Ph. D earned through discussing how and when mammals arrived in Ireland. The problem centers around two issues: (i) we are an island (ii) we were covered in ice about 13,000 years ago.
Hypothesis to explain how they arrived here include by land-bridges, swimming and traveling by boat (which humans built and navigated). These latter mammals paid their way by producing milk or later offering their hides and meat (after they reproduced, of course) to the humans.
Some were probably here before Man arrived, even though the island was covered in ice. There are mammals in the Arctic today, and I'm sure they would have been happy enough here 13,000 years ago!
Some 31 wild terrestrial mammals and 10 species of bat have lived in Ireland since that last Ice Age.
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