Eocene (Pt 2): In the Jungles of Europe

Heterohyus

During the Eocene epoch, Europe was very different from the way it is today. For one thing, it was still separated from Asia, with the Turgai Strait running between the two, roughly from what would now be the Black Sea to the Arctic Ocean. But, were you to look at a map without any modern day context, you probably wouldn't call it a continent, because it wasn't a single landmass, but a chain of large islands.

The biggest of these lay to the north, encompassing Scandinavia and the lands to the east. Just south of that, the second-largest was the one that would later become Britain, France, Germany, and some of their smaller neighbours. A smaller, but still sizable, Iberian island lay to the southwest, and a collection of low-lying ones occupied the south and east, with the more mountainous parts of that region having yet to form.

But, even if you didn't know the changes in the geography, if you could simply travel back in time to the Early Eocene and look around you, it wouldn't feel much like Europe. The continent was closer to the equator than it was now - northern Germany was about where Milan is today - but, even ignoring that, the world as a whole was much hotter. This is part of the reason for the islands, since there were no ice caps back then, but it means that our hypothetical time traveller would be, in almost any part of the landmass, standing in a jungle.

Oligocene (Pt 2): Europe's Big Break

Eomys

The dawn of the Oligocene is marked by a sudden cooling of the Earth's climate, of which the most obvious consequence was the creation of the Antarctic ice sheets. These locked up so much water that sea levels dropped worldwide, reshaping coastlines. Nowhere were the consequences of this more apparent than Europe, despite its great distance from Antarctica.

Prior to the Oligocene, it would have been possible for a hypothetical traveller to sail from what is now the eastern Mediterranean, through the Paratethys Sea (now the Black and Caspian Seas) due north and into the Arctic Ocean. The body of water that made this possible, the Turgai Strait, was already becoming shallower and narrower as the Oligocene approached, and the sudden dip in sea level finished it off altogether, closing off the sea route that had once run along the eastern flank of the Ural Mountains. 

The Smallest Mammal Ever?

When it comes to fossil mammals, or indeed, any other kind of fossil animal, our attention is inevitably drawn to the giants. We are often fascinated by the mammoths or glyptodonts or the largest of Irish elk or the most muscular of sabretooths. Outside of mammals, it seems there's a never-ending battle to find the "largest dinosaur ever".

Indeed, one might almost get the impression that everything prehistoric was larger than today. In a number of cases, that's because larger animals really did exist in the past, perhaps being wiped out by a combination of the harsh realities of the Ice Ages and the arrival of human hunters. It's also an artefact of larger bones being easier to find in rock layers and being less fragile and likely to fragment when they fossilise. And that's before we add in the fact that most popular books on the subject tend to have a focus on the biggest and most dramatic animals of their kind.

The Smallest British Mammals: Shrews

Common shrew

For some reason that I no longer recall, a picture of a shrew cropped up while I was talking with a friend on the internet. "That's a mouse," she insisted. "No," I said, "it's a shrew." "Mouse!"

It was only later that I remembered that the German word for "shrew" is spitzmaus (literally "sharp/pointed mouse") and, since my friend was Austrian, she wasn't necessarily entirely wrong. From a certain perspective, perhaps to German-speakers, all these small, furry, long-tailed things are mäusen.

And it's certainly true that shrews do look, superficially, quite like mice. They tend to be smaller, with narrower snouts, and very small ears and eyes, but there is something quite mouse-like about them. Nonetheless, shrews (unlike, say, voles) are not rodents. In fact, as placental mammals go, they aren't even particularly related to rodents - humans are more closely related to mice than shrews are.

Modified Munchies of Many Mouse-eared Myotises

In the modern system of taxonomy for the classification of living things, a genus is  group of closely related species. It is the lowest mandatory level of classification, apart from 'species' itself, and forms the first half of a creature's scientific name. Thus, Panthera, for example, is the genus containing lions, tigers, leopards, snow leopards, and jaguars.

As such, we'd typically expect a genus to contain only a small number of species - it is, after all, the smallest standard grouping of species that there is. And, at least for mammals, this is typically the case. Many genera, in fact, have only one known species, or at least only one that isn't extinct (as is the case for our own genus, Homo, for example). But there are some exceptions, cases where there are so many incredibly similar species that we just have to lump them all together.

The single largest mammal genus, as commonly defined today, is Crocidura, which represents nearly half of every species of shrew we know about. But even the second largest, Myotis, is a whopper.

The Barcoded Droppings of French Water Moles

How do you know what a given species of animal eats in the wild? The question is of more than merely academic interest. In addition to its obvious relevance to zookeepers, it can also help us to understand how a particular ecology works and what sort of harm we might do it by changing something. In the case of endangered species, it can also be important for conservation, since it's no good protecting the animal if you don't also protect its food supply.

The simplest way to answer the question is probably just to follow the animal around at a suitable distance and watch what it does. In the case of large, visible animals such as lions or moose, this is likely an effective, if somewhat time consuming, method. But it works rather less well with something small or difficult to observe, especially since small mammals spend most of their time eating. (They have to, to maintain their body temperature, since small objects lose heat more rapidly, and they need, proportionally speaking, a lot of calories).