Sunday, 26 March 2023

The Raccoon Family: Coatis

White-nosed coati
The common raccoon is the only member of the family whose scientific name dates back to the official dawn of biological taxonomy in 1758. However, just eight years later, in a later edition of the same work, Linnaeus added two further species (people were, by this point, sending him many samples of new species to catalogue) that we would now place in the raccoon family - albeit, he initially described them as civets.

These two animals were coatis (or "coatimundis"), with one first identified from Mexico, and the other from Brazil. They were given their own genus by Gottlieb Storr in 1780 when he first named the raccoon family. It's probably fair to say that, to modern eyes, Storr's classification seems the more reasonable of the two; coatis look a lot more like raccoons than they do like civets.

Sunday, 19 March 2023

Age of Mammals: The Oligocene (Pt 1)

It's been over a decade since I started including bimonthly looks at specific slices of Earth's past in this blog. In that time, I have covered three epochs: the Pleistocene, Pliocene, and Miocene. Together with the current Holocene epoch, these comprise what we currently consider to be two "periods": the Quaternary and Neogene. Both of these are dominated, more or less, by mammals of the sort we'd generally recognise today, even if the details are different. All of the earlier chunks of time since the extinction of the non-avian dinosaurs, however, constitute a different period, the Paleogene, where this was much less true.

When Charles Lyell devised the current system of dividing the "Age of Mammals" into epochs in 1833, he originally defined four. A few years later, he revised this to five, but even then, the entirety of what we'd now call the Paleogene was placed into a single epoch, the Eocene. In 1854, however, German palaeontologist Heinrich Beyrich, split off the later part of the Eocene into a new epoch, which he saw as a distinct period of transition in the development of fossil seashells. He called this the Oligocene, and it proved useful beyond his original mollusc-based definition, and so has remained in use to this day. (Beyrich's wife, incidentally, was a children's author, and made the unusual step of favourably commenting on the work of Charles Darwin in a novel for young girls at a time when it was still controversial).

Sunday, 12 March 2023

Fruit Bats of Madagascar

While most attention tends to focus on large charismatic animals such as rhinos and tigers, it will probably come as no surprise to discover that many species of bat are endangered. Here in Britain, all bats are legally protected by the Wildlife and Countryside Act 1981, making it an offence to disturb their roots. That's perhaps an unusually robust example, but other protections and conservation efforts exist across the world.

On the other hand, it is true that the majority of bat species are not especially threatened, at least on a worldwide scale - although things may be different locally. Bearing in mind that around one in six bat species are so recently identified and so little studied that we simply don't know how common they are, only around another one in six are rare enough to be listed as "threatened" by the International Union for the Conservation of Nature. Still, that's not exactly a small proportion, and since there are somewhere around 1,400 named species of bat, it's not small in absolute terms, either.

Tha bats are a highly diverse group, representing no fewer than 21 taxonomic families, none of which are likely as familiar to the layman as terms such as "cat family" or "deer family". Some of these contain very few species, representing oddities that don't quite fit into any of the main subgroups, but there are still five families with over a hundred species each. Of these, the one that contains the highest proportion of threatened species is the fruit bat or "flying fox" family, the Pteropodidae.

Sunday, 5 March 2023

Friendship and Fission-Fusion

Mammal species have a wide range od different social systems into which they organise themselves. Many are essentially solitary outside the breeding season, others form long-lasting pair bonds, and others live in larger associations which may themselves have varying different structures. Among the latter, one common pattern is that of the fission-fusion society.

Here, rather than having a long-lasting association, perhaps bonded by ties of family, the animals live in groups but the membership of that group is not constant. New animals are constantly wandering in, while others break off and leave for other groups. On a larger scale, it may be that the individual fission-fusion groups - the actual bands of animals you would see travelling together - are themselves gathered into larger social networks that may have a relatively consistent structure. That is, the new animals joining the group aren't random; they're individuals already known to the group, and rival social networks may exist nearby that do not mix their members.

Sunday, 26 February 2023

The Raccoon Family: The True Raccoons

Common raccoon
While the raccoon family contains more species than most people likely realise, by far its best-known example is the animal for which it is named. The common raccoon (Procyon lotor), alternatively known as the "northern raccoon" or simply "the raccoon" was the first species in the family to be scientifically described, no doubt because it's not only common and widespread, but because it's a very distinctive animal. Everyone must surely be familiar with what they look like, and, if you're North American, there's a decent chance that's from first-hand experience.

The common raccoon is found across almost the whole of the contiguous United States, barring only some of the drier parts of the Great Basin, as well as across southern Canada and virtually all of Mexico and Central America. Furthermore, raccoons were introduced to Germany as a hunting animal in 1927 and, with the help of others that escaped from fur farms, since around the 1970s they have been expanding rapidly across Europe. Over the last couple of decades, they have established populations from Spain and France in the west across to Russia and Ukraine in the east. In the 1990s, they were also introduced to Japan and they have also been introduced to Uzbekistan and other parts of Central Asia, probably following escapes from fur farms.

Sunday, 19 February 2023

Tree-Dwelling Almost-Lemurs of the Canadian Arctic

Northern Canada, it has sometimes been noted, can get a bit cold. The northern coasts, and the islands beyond them, are covered in treeless tundra, the permanently frozen subsoil preventing anything that needs deep roots from growing there. The interiors of the more northerly islands don't even have that much, just permanent fields of ice and snow. 

The most northerly island in Canada is Ellesmere Island, whose most northerly point is not far from being the most northerly piece of solid land on the planet, only beaten by parts of Greenland. Midsummer temperatures reach a daily high of about 9°C (49°F) in midsummer, and it often snows in July. Winter temperatures regularly drop below -35°C (-31°F) on January nights. So, yeah, that's uncomfortable.

Sunday, 12 February 2023

Benefits of a Deadly Predator

A basic concept in ecology is that of the trophic level, a concept that lines up life forms by where they sit in the food chain. Plants are at the bottom level, taking energy directly from the sun, then the next level up are the herbivores, which eat the plants. Above that we have primary predators eating the herbivores, and then secondary predators eating the primary ones. Because the transfer of energy is never perfect, each level will be smaller than the one below it, with fewer individual life forms in it, thus forming a pyramidal pattern.

The reality is more complex than this. Secondary predators also eat herbivores, omnivores are common, really large herbivores aren't likely to be eaten by anything, there may be more than two steps in the chain of carnivores, and we can't forget the detritivores and fungi. And so on. So what we actually have is a "trophic web", a complicated set of interactions where some animals don't fit neatly into a single level on the pyramid. Nonetheless, that doesn't make the basic idea useless and one of the concepts it leads to is the apex predator - the large carnivores that have no predators of their own (at least as adults).

Sunday, 5 February 2023

Haring About

One of the reasons that there is such a large number of mammal species in the world is that many of them are restricted to relatively small areas. There are a great many species that can be found only in one place, perhaps because it's a remote island or otherwise physically difficult to leave, or perhaps because they have very specific requirements and can't traverse the terrain between the patches of land that meet them. Others, of course, may have lived across wider areas in the past, but are now endangered, perhaps because their land has been converted to agriculture or urban areas, or because they are seen as either especially tasty or a threat to humans or their crops.

On the other hand, many species are widespread with large populations and seem to be happy in a variety of different habitats. Often, these are animals with a broad diet, able to eat a range of different foods and still remain healthy - the red fox is a good example of this, especially once it started exploiting suburban habitats in the 20th century. Typically, they will not be as good at finding or processing these foods as those that specialise in one particular type but the fact that they can switch food sources easily makes up for this. Indeed, this can be a driver for evolution - an animal becomes really good at exploiting one narrow food source, out-competing the generalists, but the latter remain in the background and, when the world changes and the narrow food source is replaced by something different, become the basic stock from which the next round of specialists will arise.

Saturday, 28 January 2023

The Raccoon Family

It has not always been easy to determine where exactly raccoons fit within the larger mammalian family tree. In part, this is because it's difficult to pin down exactly what defines them and makes them distinctive from their closest relatives. We can get some idea of this by looking at the taxonomic history of the group.

The scientific classification of living organisms we use today has its origins in the 1758 edition of Systema Naturae, by Carl Linnaeus. Raccoons live only in the Americas, but even in 1758, Linnaeus was aware of the existence of raccoons, having heard about them from his friend Peter Kalm, who had observed them in what were then the colonies of Pennsylvania and New Jersey. Based on Kalm's description, Linnaeus named this new species Ursus lotor - the "washing bear". It was one of four species of "bear" that he identified in that work, only one of which we'd still consider to be such today.

Sunday, 22 January 2023

Miocene (Pt 37): The Miocene Oceans

Given their extreme adaptations to a life at sea, it should not be surprising that whales and dolphins have a long evolutionary history. Even at the dawn of the Miocene, when seals were at best, only very recent arrivals, and may still have been semi-aquatic, like otters, the cetaceans were already well-established. A time-travelling whale-watching expedition at almost any point during the Miocene would likely have been just as rewarding as one today and, especially so far as one would have been able to see them above the waves, the animals you would have been spotting would not have looked all that different.

At a more detailed anatomical scale, that would have been less true and many of the creatures would not have been as closely related to the modern forms as one might have supposed. Today, the largest number of cetacean species belong to the "true" or "oceanic" dolphin family, including not only all of the sea-going dolphins but some larger animals such as killer whales. But in the Miocene, true dolphins seem to have been comparatively rare and we know of very few fossils predating the subsequent, Pliocene, epoch.

Sunday, 15 January 2023

Grumpy Old Voles?

Meadow vole (a related species)
It should go without saying that the behaviour of young mammals changes as they approach, and eventually reach, adulthood. Obviously, there's the development of the mating drive, but there are also social changes, as the animal gains independence, first from suckling, and then more generally from its parent(s), often leaving home, whether to live alone or to find a new pack where its potential mating partners aren't also its own siblings. 

Drawing parallels between these changes and the way that humans develop isn't without risk; the complexity of our society, the existence of culture and so on significantly colour how we behave. But that's not to say that such parallels don't exist, and can't tell us anything, even if it's only how we evolved. We are, after all, still affected by our biology and evolutionary history in at least some respects. For instance, it's notable that exactly how animal pups are raised by their mother can affect how they behave as adults, even if the details are going to be less complex than they are with human child-rearing.

Sunday, 8 January 2023

Dunnarts in the Sandhills

It's a recurring theme of this blog, especially notable in last year's series on Old World leaf monkeys, that a great many mammalian species are threatened in some way. Population numbers of many species are declining, to the point that their continued existence is in doubt, often due to human encroachment on their habitat, but also due to the habitat itself changing as climate change continues. In this context, the quest of zoologists to understand how mammals (and other animals) behave is not just one of intellectual curiosity but can be of direct benefit to the creatures themselves.

For example, it is useful to conservation efforts to understand not only where a given species lives, and the habitat requirements it may have, but how it makes use of that environment. (Obviously, there's more to it than this, for example, how different species in the same area interact with one another but we'll stick with this one point for today). What particular features of the habitat are important to it? How much land does it need? How is its population distributed across the area?