Sunday, 8 December 2019

Small British Mammals: Moles

If hedgehogs are generally welcome in suburban gardens, there's one native British animal that generally isn't, and, like the hedgehog (and shrews) it belongs to a group of insect-eating mammals technically called the Euliptophyla. This, of course, is the European mole (Talpa europaea), sometimes called the "common mole" if we even need to distinguish it from other kinds of mole at all.

As the name implies, European moles are essentially unique to Europe. They are found throughout much of the continent, from northern Spain, Italy, and the central Balkans in the south to southern Sweden and Finland in the north. They are not found in southern Russia, but do reach just beyond the boundary with Asia in the northeast. While they are not native to Ireland, they are found on a number of smaller islands off the coasts of England, Scotland, and Denmark.

Sunday, 1 December 2019

Miocene (Pt 17): A Diversity of Dogs

Eucyon
As North America dried out in the Late Miocene, and slowly transitioned towards the deserts and open grasslands that became dominant across the central parts of the continent, it wasn't just the herbivores that were forced to adapt. Carnivores may not have been affected so directly, but, if their food source was changing, they had to do so too.

There were two particularly significant changes among the North American mammalian carnivores that took place around this time. One was the extinction of the bear-dogs, a group with a long history on the continent that was, by this time, typified by relatively large animals that would have looked more like bears than dogs (although they were neither). Over in Europe and Asia, the bear-dogs survived for rather longer, although even there they struggled...  but in North America, the changes were too extreme for them to cope with, and they died out as the Late Miocene dawned.

Sunday, 24 November 2019

Small British Mammals: Hedgehogs

There can be few British mammals more distinctive and well-loved than the hedgehog. Indeed, a 2016 poll found that it is, by a substantial margin, Britain's favourite mammal. (For what it's worth, and by a similar margin, the robin is apparently our favourite bird).

The animal that Brits simply call "the hedgehog" is more accurately the European hedgehog (Erinaceus europaeus), and it's found through pretty much the entirety of western Europe. In fact, across much of the continent, the eastern border of its occurrence is very roughly where the old Iron Curtain used to be. That's a simplification, of course, and aside from some border regions of former 'Eastern Bloc' countries, they are also found quite extensively in the Czech Republic, Estonia and parts of north-west Russia. They are also common on several larger islands, including Ireland, Corsica, Sardinia, and Sicily, and, in more recent times, they have been introduced to the Azores.

Sunday, 17 November 2019

Don't Sleep with Your Sister

Conservation of mammals (or other animals) isn't simply a matter of providing enough suitable habitat for them to live in. One other consideration is that that habitat should not be overly fragmented - and this can be a problem as we build roads or other transport networks that cross otherwise wild terrain. The problem with fragmented habitats is that, even if there is enough space and food to support a small population of the animal in question, that population cannot reach and interact with other populations. And this leads to inbreeding.

We have known that inbreeding is a bad thing in animals since... well, probably at least since we started domesticating livestock. In our own species, there's a natural revulsion against incest, something that's reflected in moral teachings that go back at least as far as the Old Testament, and similar codes in other cultures. Animals too, avoid inbreeding when they can, perhaps finding the scent marks left by genetically similar individuals to be unpleasant.

Sunday, 10 November 2019

Small British Mammals: Water Shrews

Two of the three species of shrew found in Britain are very similar to one another in appearance and habits. This is hardly surprising, given how closely related they are. The odd one out, however, is not quite such a close relative, and is rather more distinctive.

This is the Eurasian water shrew (Neomys fodiens), which unsurprisingly, is simply called the "water shrew" in Britain. Despite its differences, even at first glance, it's pretty obvious that it is a shrew: it's a small, long-tailed animal with short fur, tiny ears, small eyes, and a narrow, pointed, snout filled with sharp teeth. However, by the standards of shrews, it's unusually large. Fully grown adults can reach as much as 10cm (4 inches) in length, and weigh up to 25g (0.9 oz.), closer in size to a typical mouse than to other native shrews.

Sunday, 3 November 2019

Bat Poo and Fig Trees

Seba's short-tailed bat (Carollia perspicillata)
feeding on wild pepper
If the presence of plenty of carnivores is generally bad news for herbivores, it may seem that the presence of plenty of herbivores is bad news for plants. Clearly, such problems as over-grazing do exist, but the reality can often be more complex. Fruit are a particular case in point.

Many fruits are tasty specifically to encourage herbivores to eat them, containing highly resistant seeds that pass through the herbivore's digestive tract, land in a nice pile of manure, and germinate to create more plants in future. It has been estimated that, in most wild forest environments, anything from 45% to 90% of tree species bear edible fruit of this kind. (Of course, a number of the fruits we see in supermarkets are even tastier, because we've bred them that way, with the banana being perhaps the most extreme example. But it's not as if wild apples and oranges, for example, don't exist and aren't attractive to animals).

Not all herbivores eat these kinds of fruit, as opposed to other things that botanists would call "fruit", such as grass seeds. Primates are one of the more obvious examples of mammals that do, and it's theorised that our unusually good colour vision arose in part so that we could easily tell which ones were ripe. But another group of mammals that eat a strongly fruit-based diet are, unsurprisingly, the fruit bats.

Sunday, 27 October 2019

How Sloths Turned Upside Down

One of the things that sloths are noted for is spending a lot of time hanging upside down. This isn't, of course, something they literally spend their entire lives doing; they come down out of the trees to defecate, and they do sometimes travel over the ground - or swim across rivers - to move from one tree to another. They have also been observed, especially in zoos, casually sitting about in what we'd consider a fairly normal posture. But even so, being upside down is how they spend most of their time.

This is obviously pretty odd, from the perspective of a mammal (or, indeed, most other animals). You might think that what must have happened is that, at some point in the distant past, some ancestral tree sloth first headed up into the branches, decided to do so by hanging from them rather than by the more obvious method favoured by (say) primates, and that all of its descendants simply happened to do the same thing. In other words, it's a one-off quirk of evolution.

Except that can't be right.