Sunday, 22 April 2018

The Pig Family: Threatened Pigs of the Philippines

Visayan warty pig (female)
When the animal we now know as the Sulawesi warty pig was first described, back in the 19th century, it was thought that it lived, not only on the island of Sulawesi, but also on a whole chain of islands to the north - the Philippines. But the pigs there didn't look exactly the same as those to the south, so in 1886, German zoologist Alfred Nehring proposed that they be regarded as a distinct subspecies.

And so things remained for a hundred years, until scientists began to look more closely at the animal's genetics. When they did so, they discovered something fairly surprising. Pigs typically have 38 chromosomes (compared with 48 in humans), but it turned out that the warty pigs from the Philippines had only 36 - an entire pair had disappeared, its genetic material shuffled around elsewhere in the genome.

Sunday, 15 April 2018

The Curious Necks of Giant Rodents

Josephoartigasia
We tend to think of rodents as small mammals, and the great majority of them are: mice, voles, hamsters, tree squirrels, and so on. Even rats and gophers aren't really all that big. Indeed, when most people think of rodents they probably aren't mentally including the largest ones, such as porcupines and beavers. In fact, the very largest rodent alive today is the capybara, a sort of giant guinea pig that is around 120 cm (4 feet) long and weighs something like 50 kg (110 lbs).

This, you probably won't be surprised to learn, is as nothing compared to some of the fossil species.

Sunday, 8 April 2018

No Boys Allowed

Even in mammals that are otherwise social, it is quite common for males and females to live apart for most of the year. The most common pattern involves females living in groups with their children, until the latter approach adulthood, while males either live alone, or in much smaller bands, outside of the mating season. In many hoofed herd animals, however, the males live in herds that aren't much smaller than those of the females - in other words, both sexes live in herds, but the two don't mix until it's time to do the necessary.

Clearly, these are creatures that benefit from the group protection that living in herds provides, and, while there's obviously a limit on how large a herd can be before there isn't enough food to support them all, it's not always so clear why the herds should be single-sex. Why, in short, do so many hoofed herd animals practice sexual segregation?

There are a number of theories, and, as is often the case, they aren't mutually exclusive. Nor is it likely that the reason - or the balance of reasons, if there's more than one - will be the same for every species. It's something we have to examine on a case-by-case basis.

Sunday, 1 April 2018

First of the Flightless Penguins

Waimanu
Penguins are unusual birds. They walk fully upright, have short legs that force them to waddle, and have wings adapted into flippers to propel them through the water. Compared with many other bird groups, there aren't all that many of them - there are no more than twenty living species, and possibly less, depending on who you talk to.

Surprisingly, perhaps, we have, however, named many more fossil species than living ones, and our understanding of penguin evolution is rather better than that of most families of flying bird - which tend to have light and fragile bones that don't fossilise well. Unfortunately, as is often the way, it's the earliest and most interesting part of that fossil history that's most obscure, since, being older, these are the fossils least likely to be preserved.

But that doesn't mean we have nothing from that time.

Saturday, 24 March 2018

The Pig Family: Wild Pigs of Indonesia

Bearded pig
Thanks to their adaptability, wild boar are a remarkably widespread species, being found from Portugal to Japan. All of their close living relatives, however, are much more restricted, each being isolated on different islands or island chains off the south-east coast of Asia.

The largest such island, and, indeed, the third largest island in the world, is Borneo. This is home to the bearded pig (Sus barbatus), which is also found, not only on the neighbouring island of Sumatra, but also on the Malaysian mainland. The Bornean and Sumatran forms of the animal are widely regarded as different subspecies - the latter going by the rather brilliant name of S. b. oi - although quite which of these two the Malaysian pigs belong to has been a matter of mild controversy.

Saturday, 17 March 2018

Miocene (Pt 6): The Coming of the Mice

Palaeotragus
The Early and Mid parts of the Miocene epoch were, for the most part, times when the world was much warmer than it is today. It wasn't a steady pattern, however, and I've already described how the fluctuations in climate, over the course of many millions of years, affected the rodents of Europe. It was a time when the most common small mammals in Europe were not mice and voles, but dormice, accompanied by early hamsters, squirrels, and the gliding eomyids.

By 10 million years ago, however, the colder, drier climate had become locked in for the long term. We know that the forests of Europe changed dramatically at this time, the old subtropical trees, such as figs and palms, being replaced by oak, alder, and elm. Likely as a result of this change in the available food supply, most of the dormice died out, leaving only a few close relatives of the relatively small number of species we have today.

Sunday, 11 March 2018

The Crusty Forearms of Male Bats

Bats, of course, are not blind. There eyesight is, in fact, pretty good in the majority of species. Which makes sense for an animal that has to fly around at night when the light is dim but not entirely absent. It's only for animals like moles, which live underground, where the light can't penetrate at all, that vision becomes an expensive and unnecessary luxury.

Having said that, many species of bat do spend a lot of time in caves, and, in there it really is too dark to see anything, no matter how good your night vision might be. As a result, the other senses of bats are often highly tuned. Hearing is the obvious one, since bats rely on that for their sonar abilities, but many species also have well-developed senses of smell. In particular, since bats also tend to be highly social, scent often forms a crucial part of their ability to communicate with one another - as it does for many other mammal species.