Sunday, 17 March 2019

The Beaches of Bakersfield

Modern walrus skull
Seals have a moderately long fossil history, with some of the oldest examples dating from Europe, around 15 million years ago. Although they are now found worldwide, back in those early times, they seem only to have lived in the North Atlantic, reaching the Pacific only around 11 million years ago (probably by the simple expedient of swimming through the seas that then covered what is now Central America).

However, one of the world's best fossil sites for recovering fossil aquatic mammals is at Sharktooth Hill, just outside of Bakersfield, California. Part of the larger Temblor Formation, the deposits here consist of silts and sands, laid down just over 15 million years ago, when California was sweltering in the Middle Miocene Climatic Optimum, a time of unusually high worldwide temperatures - and correspondingly high sea levels. This was before seals had reached so far west, but that does not mean that a number of similar animals did not already live there at the time.

Sunday, 10 March 2019

Breeding Cats in Captivity

The Sumatran tiger is a critically endangered subspecies
Although the actual number may be higher, depending on the status of certain subspecies, there are 38 widely recognised species of wild cat. Of these, five are formally considered to be "endangered species", and a further thirteen are "threatened", but not sufficiently so to fall into the riskier bracket. Taken together, that's almost half of the total species, and it ignores the significant number of species that are threatened in parts of their natural range, but survive well enough somewhere else.

The primary reasons for this are habitat loss and poaching, and virtually every species of cat - even those, such as the puma/cougar/mountain lion, that aren't threatened overall - has a declining population. Fortunately, the same thing that makes wild cats attractive to poachers - their undeniable charisma and beauty - also inspires conservation efforts of the sort that, say, the Ethiopian amphibious rat (Nilopegamys plumbeus) could only dream of.

Sunday, 3 March 2019

Fluorescent Pink Squirrels

In visible light...
I don't normally cover stories that have been in the news recently, but this was too good to pass up, and, anyway, it wasn't that prominent so some people may have missed it. Fluorescent pink squirrels, oh yeah!

Our story begins in May 2017 with, of all things, a professor of forestry. He was conducting a preliminary survey of the plants and lichens growing in a forest in northern Wisconsin, Many kinds of lichen, and some flowers, fluoresce under UV light, so one way of finding them is to wander around in a forest at night, carrying a UV flashlight. So far, so perfectly normal for the people who study this sort of thing. But, on this occasion, the researcher discovered something entirely unexpected: when he directed his flashlight at a nearby squirrel, it fluoresced a brilliant pink.

This is not something one generally expects squirrels to do. Clearly, more research was called for.

Sunday, 24 February 2019

Small British Mammals: Field Mice

Wood mouse
While the common house mouse is likely one of the most familiar of all animals living wild in Britain, it is only one of four species of mouse native to the islands. (France and Germany, for comparison, have six each, although they aren't the same six). Of the other three, the closest relatives of the house mouse are the two species of field mouse, which are also found widely on continental Europe.

Field mice have benefited less from the presence of humans than house mice, since they tend to avoid human dwellings, and there are rather a lot of those in Europe. Given their common name, however, one might suppose that they have at least benefited from the spread of agricultural land. This, however, only true of one of the British species. This is the wood mouse (Apodemus sylvaticus), sometimes also known as the "long-tailed field mouse". In Britain, when the term "field mouse" is used without qualification, it typically means this one.

Sunday, 17 February 2019

Miocene (Pt 12): American Rhinos and Horse-Headed Lopers

Moropus
The warming climate of Early Miocene North America was host to a variety of animals, both familiar and unfamiliar. Even in the former category, some of the creatures would have looked a little odd too modern eyes, but we can still say that a three-toed horse is, at least in general terms, still a horse. One group of animals that would be a little harder to place were the oreodonts (or, more technically, "merycoidodontids"), which were already fairly diverse when the Miocene dawned.

These creatures were unique to the continent and were medium-sized herbivores. They would have looked vaguely like pigs, although without the flattened nose-disc of those animals, and with four functional toes on each foot. As far as we can tell from their teeth, they were mostly browsing animals and were spread quite widely across the continent.

Sunday, 10 February 2019

Land Mines and Scent Marks

For primates such as humans, vision is our primary sense. For the majority of mammal species, however, the most important sense is probably that of smell. In addition to using this sense to scope out the natural environment around them, many mammals leave scent marks as messages to one another, marking out a territory, advertising their willingness to mate, or whatever else they wish to convey.

Much research on the nature of scent marking focuses on how and where the animal leaves these messages, or how they may differ based on sex, maturity, and so on. This is obviously important if we want to understand why they're doing it, and what it is that they're trying to 'say'. But, naturally, it's also useful to understand how other animals of the same species respond to those marks - there's no point leaving a message if everyone else is just going to ignore it.

Sunday, 3 February 2019

The Hybrids are Coming

Hybrid domestic pig x wild boar
Conservation - whether it be of mammals or any other kind of animal or plant - tends to focus on the species level. These are the discrete kinds of living creature that can be most easily identified and preserved, ensuring that the mix and variety of the natural world remains as close to its original state as possible. Preservation of subspecies is often a lower priority, which makes sense if you really have to make the choice, but it, too, can be important if we want to preserve such things as genetic variation within a species.

The common understanding of a 'species' is that it consists of a group of animals that cannot interbreed with animals outside that species to create fertile offspring. This, however, is an oversimplification; lines blur, and not always in neat and tidy ways. Scientifically, there are multiple different ways of defining what a 'species' is, but the general idea is that it has to be a group of animals that can be readily identified as different from their relatives. Which tends to mean that, even if they can interbreed with other species, they generally don't, at least in the wild, and maintain a separate gene pool.

Saturday, 26 January 2019

Small British Mammals: House Mice

Over the last few years, I have done a roughly annual series covering particular groups of mammals, exploring all the different species, familiar and unfamiliar, that belong to them. (If you haven't read the past ones, the link "Synapsida Series" points to the list of them; note that the individual posts appear in reverse chronological order once you select a series to view). One problem with selecting which groups to cover in a given year is that only some groups will really work, and, even then, some are clearly better than others.

One problem, for example, is that some groups are simply too large, and if you split them down into narrower groups that are more easily handled, there's no longer enough variety for it to be worth it. Such is particularly true of small mammals. There are over 700 species in the mouse family, for instance, with over 500 of those in the "murine" subfamily, which includes all of the familiar ones. Even if it would be practical to describe them all, most of the individual species haven't been studied in any detail, so you'd rapidly get a long list of "looks mouse-like, lives in XX".

Sunday, 20 January 2019

Murderous Whales of the Eocene Oceans

The relationships between what animals eat can be thought of as a pyramid. At the bottom are plants, which are eaten by herbivores, which are eaten by carnivores, which are eaten by larger carnivores. The reality is much more complex, and is more accurately thought of as a web (omnivores exist, large carnivores also eat herbivores, etc.), but the general principle is broadly true. In particular, the further up the ladder you go, the fewer animals there are, since the transfer of energy from one level to the next can never be 100% perfect.

At the top of the pyramid are the "apex predators". These are the carnivores that have no predators of their own, that are able to feed without fear of being eaten themselves. Again, the reality is more complex - an adult of one apex predator might occasionally kill and eat the young of a different kind, for instance. And, of course, everything gets eaten by worms (or whatever) once they're dead. Nonetheless, really big scary predators clearly do exist, even if, by their nature, they aren't very common.

Sunday, 13 January 2019

Requiem for a Dolphin

Dolphins are social animals, living in pods and engaging in what seems to be fairly sophisticated communication. It's likely that such behaviour is part of the reason for their success, with well over 30 species spread across the world's oceans... and that's excluding porpoises, and some other "dolphin-like" animals outside the dolphin family proper.

Sociability involves a number of different traits and behaviours, but one that's known to exist in cetaceans and relatively little else, other than primates, is what's technically known as epimeletic behaviour. This is, in essence, the act of helping other members of your species when they are in trouble, typically due to an injury of some kind. (For what it's worth, this compares with etepimeletic behaviour, which is acting in such a way as to make it easier for others to care for you).

Sunday, 6 January 2019

Gerbil versus Rattlesnake

Sidewinder
Deserts are harsh environments, and living in them poses animals a number of problems, not least of which are daytime heat and an absence of water. In order to survive in such a place, animals need to evolve suitable adaptations - extremely efficient kidneys to reduce water loss are one such example.

But the thing about deserts is that, while there are some geographic differences between them, the challenges of living in one are at least broadly similar regardless of which desert it happens to be. And while, say, the world's seas are all connected, the deserts aren't. So animals, including mammals, have had to evolve means of surviving in them several times over, re-developing the necessary features each time they encounter a new one.