Delphinids: Right Whale Dolphins

Northern right whale dolphin

Dolphins are familiar animals. We see them at aquaria and boat trips to see them in the wild are relatively common. In recent decades, there has been a rise in 'swimming with dolphins' tourist experiences, which studies have shown to be good in the short term for humans, but less so in the long term for the dolphins. Either way, we know a fair amount about them, both culturally and scientifically and, depending on the part of the world you live in, there may be many different species that you can see.

Some dolphin species, however, are less well-known than others. I've covered some already, but perhaps the most obscure are the right whale dolphins. 

Fishing for Salmon (When You're a Bear)

Bears like eating fish. Among the most iconic images of brown bears (Ursus arctos) are those that show them wading out into a wide river or by a waterfall, and catching salmon for their food. Yet this isn't necessarily an image of everyday ursine behaviour.

This is because wide rivers, whitewater rapids, and so on, aren't all that common. Or at least, they don't form the majority of bear habitat. We watch and photograph bears feeding in such places because it looks dramatic and, more importantly, it's relatively easy to do. It's the same with other predators. We know a fair amount about the hunting habits of wolves and lions because we can watch them in Yellowstone Park or the Serengeti, where the terrain is wide open. That allows us to safely observe their behaviour from a distance, so, understandably, we'd prefer it where possible.

Delphinids: Newest and Largest Dolphins

Fraser's dolphin

One of the largest features at the British Natural History Museum is a full-scale model of a blue whale, occupying a large chunk of one of the mammal halls. This was installed in 1938 by Francis Fraser, a Scottish zoologist with a lifelong interest in cetaceans. Eighteen years later, still working at the museum, he was put in charge of reorganising their collection of cetacean skeletons and came across one that hadn't been closely examined since it had arrived in 1895.

It had been donated by Charles Hose, a colonial administrator and amateur naturalist who had found the skeleton on a beach near a river mouth in Sarawak (then a British Protectorate). Hose hadn't been quite sure what it was, and simply labelled it "white porpoise ? Lagenorhynchus sp." before sending it on. When Fraser examined it, however, he soon realised that it couldn't possibly be what Hose had guessed and that it was, instead, an animal previously unknown to science.

American Moles in a Spanish Crater

Eastern mole

Moles are unusual animals. Most species are highly adapted for digging, spending almost all their lives underground, making them vulnerable to predators when they have to venture onto the surface. One might think, therefore, that they would not have dispersed widely across the globe and that it should be easy to trace their evolutionary history.

However, this is not the case. For one thing, moles are found across the Northern Hemisphere, in Europe, Asia, and North America. A million years is, after all, a very long time and moles have been around far longer than that - including some times when the Bering Straits were dry land. 

How the Lemming Got its Coat

The Ice Ages were, without doubt, the most dramatic natural climatic changes on Earth in the last few million years. The last one was particularly severe, with vast ice sheets covering much of northern Europe and northern North America. This, naturally enough, forced many species of animals in the Northern Hemisphere to move south. Even those well-suited to the cold, such as reindeer, musk oxen, and woolly mammoths, would have had to avoid the barren ice sheets, even if they were happy in the broad tundra belt to the south.

In Europe, in particular, there is only so far south you can go before hitting the coastline. This meant that many animals were forced into small areas, some of which may still have been marginal habitat for them, to avoid extinction. These areas are called "refugia", and their small size and isolation were a driver for evolutionary change. Sometimes populations were split apart for so long that they became separate species and, for example, we can date many species of northern birds to this time, even though, for them, the Mediterranean would not have been an issue. 

Delphinids: Dolphins in the Irrawaddy

Irrawaddy dolphin

While we normally think of dolphins as being sea-dwelling animals, there are no fewer than eight species referred to as such that are commonly found in rivers. Six of these, however, are not true members of the "dolphin family", or Delphinidae, their ancestors having split off from that group even before those of some of our modern whales did. Of the two exceptions, one is entirely freshwater, and lives in South America. The other is more varied in its habitat and lives in Asia.

The Irrawaddy dolphin (Orcaella brevirostris) was first described in 1866, from a specimen caught, not in a river, but off the northeast coast of India. We now know that this is at the far western edge of its range, and that it is also found all along the coast from northeast India, around the Malaysian Peninsula, to as far east as southern Vietnam. It is also found further south, around Borneo and along the north coasts of Sumatra and Java. In 1999, a very small population was discovered in the Philippines, living in a couple of isolated bays very far from the remainder of the animal's range, presumably the result of some having been swept away in a storm decades or even centuries before.

Oligocene (Pt 16): The First Monkeys in South America

A modern South American monkey

Much like the rodents, the presence of monkeys in South America has long been a puzzle. We know that monkeys evolved in Africa and that the monkeys still living in the Old World share a common ancestor distinct from, but related to, the common ancestor of the American sort. Genetic evidence shows that the split between the two lineages, which must have happened in Africa, happened a very long time ago. At some point then, early monkeys from what we now call the 'New World' group must have crossed the Atlantic, likely rafting on a floating patch of vegetation.

The Atlantic was narrower then than it was now, and ocean currents were different, but it's still a remarkable feat. It may also have been a lucky escape, since the African relatives of this first American migrant died out not long after, perhaps outcompeted by the ancestors of today's langurs, baboons, macaques, and apes. In South America, however, its descendants got almost free rein, diversifying into the five families we have today.