What is a mammal?
Mammals, which includes us (and your furry pets), are vertebrate animals (with backbones) characterised by:
- Young nourished with milk from their mothers.
- Having hair (in whales, this only occurs in the foetal stage).
- A lower jaw hinged directly to the skull.
- The inclusion of 3 bones in their ears for transmitting sound.
- Having a diaphragm separating the heart and lungs from the abdominal cavity.
- Only having a left aortic arch (artery originating from the heart).
- A lack of nucleus in mature red blood cells.
- Giving birth to young (except for monotremes, egg-layers, such as the duck-billed platypus).
Mammal species
Mammals are diverse; they can be super small, such as bats weighing less than one gram, or impressively large, like the blue whale weighing in at over 180 metric tonnes. There are 5,500 species worldwide, living across all large landmasses and oceans. Rodents are the most numerous, both in species number and total numbers. The pangolin gets a top spot for uniqueness, being covered in scales.
In Britain, there are about 90 native species (this compares to about 420 found in the Amazon rainforest), including:
- Eulipotyphla (small, feed mainly on insects and often hibernate) – hedgehogs, moles and shrews.
- Lagomorpha (gnawing herbivores) – rabbits and hares.
- Rodentia (small gnawing mammals) – squirrels, voles, dormouse, beavers, mice and rats.
- Carnivora (placental mammals eating flesh) – red fox, badger, otter, wildcat, pine marten, stoat, weasel, polecat, American mink.
- Artiodactyla (hoofed animals with an even number of functional toes) – wild boar and deer.
- Pinnipedia (aquatic) – seals.
- Chiroptera (adapted to fly) – bats.
- Cetaceans (aquatic) – whales and dolphins.
Declining mammal numbers
Alarmingly, one in four native mammals in Britain is at risk of extinction. An increasing number of species appearing on the IUCN Red List of Threatened Species, reflects a worldwide decline of plants and animal diversity. 28% of the world’s mammals are threatened with extinction (falling in the vulnerable, endangered and critically endangered categories). There are many reasons for the dramatic loss in biodiversity, of which human activities play a dominant part, as shown here:
- Residential and commercial development.
- Agriculture and aquaculture.
- Energy production and mining.
- Transportation and service corridors.
- Biological resource use (e.g. logging/fishing).
- Human intrusions and disturbance (e.g. recreation activities).
- Natural system modifications (e.g. fire/dams).
- Invasive and other problematic species, genes and diseases.
- Pollution.
- Geological events (e.g. earthquakes).
- Climate change and severe weather.
A species might be affected by one or more of these threats. The upside of these threats being man-made is that we have the agency to counter them.
Why mammal species loss matters
Charlie Le Marquand from the Mammal Society outlined nicely the importance of retaining and protecting species in her podcast episode.
- Mammal species are part of an ecosystem, so if you lose one species, it upsets the dynamics of the entire ecosystem. A loss of one species can lead to further species loss, as they may provide resources for other species to survive.
- Ecosystem services – certain mammals can directly provide positive help to us humans. For example, bats are necessary for pollinating many tropical and sub-tropical plant species.
- Intrinsic value – I liked this one a lot, as it highlights our respect for the living things we share our planet with, not because they give us anything, just for their very presence.
What can we do?
Simply becoming aware of the problem can inform how we view and value nature. Our family gained a Hungarian Vizsla dog seven years ago. Before we had our Vizsla, I wasn’t aware of their existence, but afterwards, I saw them everywhere. These sightings were not because there was a spike in numbers of this particular breed but simply because they were now on my radar. When we are out in nature, a green space of any kind, we can become more in tune with the presence and evidence of mammals. If you think it adds a new dimension to your enjoyment of the natural world, then you could consider helping with their recording. The Mammal Society have an app for anyone wishing to record mammal (and evidence of mammals) sightings in Britain. There are organisations across the globe set up to specifically conserve species and are always looking for volunteers to help locate mammals.