Sunday, 20 June 2021

Girl Power in the Monkey World

There are many advantages to an animal of living in a group, such as it being easier to watch out for predators or even drive them away. One of the downsides, however, is that you also have to compete with others of your own kind for access to resources. Clearly, constant infighting is not a good thing and would lead to a rapid breakup of the social group in question. One way that this can be reduced is through the practice of social dominance.

The first formal model of this concept in animal behaviour was described by Norwegian zoologist Thorleif Schjelderup-Ebbe in the 1920s. Having grown up on a farm, he had observed the behaviour of chickens, and, in his PhD dissertation in 1921, he described what is popularly known as the "pecking order". What happens is that, rather than fighting constantly, chickens establish a hierarchy where each animal knows where it stands. If two chickens face off against one another, the lower-ranking, or submissive, bird almost always backs down, allowing the higher-ranking, dominant bird to win without a proper fight. 

Sunday, 13 June 2021

All the World's Deer: Deer from the Ganges and Beyond

Barasingha
At least before the rise of intensive agriculture, India, with its lush vegetation, was prime habitat for deer. The constraints of geography - the Himalayas to the north and deserts to the west - keep it separate from Europe and central/northern Asia at least, but it's a very large place, able to support a number of local species. When it comes to deer, there are no less than seven species native to the country, although four of those are only found in the north. Across the great bulk of the country, two medium to large species are common: the sambar and the chital. But there used to be three.

That third one was the barasingha (Rucervus duvaucelii). Fortunately, while I say 'used to be', I don't mean that it's extinct, as its closest relative, Schomburgk's deer is. Just that it's no longer common and widespread. It's primarily a grazing species, feeding in long grasslands and on forest edges and there used to be many of these on the Indian subcontinent. As recently as the 19th century, barasingha were found across almost the whole of central and northern India (aside, of course, from the Rajasthan desert) as well as in neighbouring parts of Pakistan, Bangladesh, and Nepal. They were especially common along the great floodplains of the Ganges and Indus Rivers.

Sunday, 6 June 2021

Out of Lockdown

Many mammal species are, by nature, solitary, spending most of their adult lives apart from others of their kind except when mating or raising young. But others are inherently social, living in herds, packs, or simply in mated pairs that live together for a long time even when they don't have children. For such animals, being separated from others is an abnormal situation that can be stressful.

One thing we often see when animals that have been forcefully separated are reunited is that they interact even more than usual, rebounding after their isolation. For instance, male rats kept apart from their friends for a week greet one another with increased petting, social grooming, and anus-sniffing, compared with how they behave on normal days. It probably doesn't come as much of a surprise that something similar is known to be true of humans that have experienced temporary social isolation.

Saturday, 29 May 2021

A History of the Honey Badger

Traditionally the weasel family was divided into three subfamilies: the otters, the skunks, and everything else. Sometimes the badgers were added as a fourth subfamily, but that was about it. As more modern genetic analysis came along, showing us some of the underlying relationships that weren't apparent from anatomy alone, it became clear that things were a good deal more complicated than that, and we now recognise about eight subfamilies of mustelid. (And that's not counting the skunks, which turned out to belong to a different group).

The badgers, in particular, turned out to be more varied in their origins than we had previously thought. Their superficial similarities were due to them all having evolved to be heavily-built digging animals, rather than because they all shared one single ancestor. In particular, two kinds of badger, the American and honey badgers, are now recognised as representing their own distinct subfamilies, with just one living species each, and diverging from the other "weasels" very early on - probably before the "true" badgers of Eurasia had first appeared.

Sunday, 23 May 2021

Out of Your Hole

Many animals dig burrows. They can be used for shelter when sleeping, or as a safe place to raise young and, while they may take more effort to construct than finding a natural rock crevice or hiding beneath a log, it's often worth it. Especially if you happen to live in an environment - open grassy plains, for example, where such alternatives are hard to come by. Although, admittedly, this does tend to apply only if the animal in question is small; not only would it take more effort for a large animal to dig a burrow, there's less that's likely to eat it, and it would be harder to hide the entrance anyway.

But some small mammals go further than merely digging burrows to sleep in. They spend almost their entire lives underground, being able to feed off earthworms, roots, and the like. It's a peculiar environment to live in, entirely lacking in light, and requiring constant work to maintain, as well as often being low in oxygen. But it is undeniably safe, not just from most predators, but also from inclement weather (so long as you're not somewhere that's prone to flooding). 

Sunday, 16 May 2021

All the World's Deer: Endangered and Beyond

Eld's deer
A significant number of deer species are endangered. As primarily forest-dwelling animals they are particularly vulnerable to habitat loss, especially in those parts of the world with high human population density and intensive agriculture. Indeed, of the species of deer formally listed as endangered by the IUCN, all but one live in southern and eastern Asia.

Among these is Eld's deer (Panolia eldii), first described by Percy Eld, a British officer working for the Commissioner of Assam, and then more formally written up by army doctor John McClelland in 1842. There is some dispute about the correct scientific name of the animal, due to a number of conflicting studies about where exactly it fits in the deer family tree. It was originally placed in the genus Cervus, along with red deer, but that didn't mean much at the time, since it was 17 years before the theory of natural selection, let alone modern phylogeny. 

Sunday, 9 May 2021

Miocene (Pt 26): Planet of the Monkeys

Victoriapithecus
The primates are one of the major mammalian orders alive today, with a great many species spread across three continents: Africa, Eurasia, and South America. They have an ancient history, and, even by the dawn of the Miocene, were already divided into the two main groups we have today: the prosimians and the anthropoid primates (most of which are monkeys, or 'simians').

It's probably fair to say that most scientific attention has been paid to the latter of those groups, but we do have a number of fossil prosimians from the Miocene. Madagascar, where most prosimian species are found today, was already an island, and had been since the time of the dinosaurs, but there are few known fossils of the relevant age there to tell us much about the early history of lemurs and their kin. Nonetheless, during the Miocene, prosimians were more widely spread than they are today.