But, leaving those possibilities aside, three basic options for surviving the winter present themselves. They could do something behavioural, such as storing food during the summer and coming back to their hidden caches later in the year when food is short. Or they could change physically, such as by building up fat over the summer or having an extra-thick winter coat that falls out in the spring. (And these are not, of course, mutually exclusive).
Sunday, 25 July 2021
Sunday, 18 July 2021
Sometimes this is due to a simple imbalance in numbers. In species where males monopolise multiple females, a typical herd, while predominantly composed of females, will also have a single dominant male, forcing any subordinate males to live elsewhere. But this is not the case in deer, because, while stags do indeed mate with as many does as they can get away with, they don't live with them outside the rut. Nor are they alone, since other herd animals, such as goats and antelope, often do the same.
Sunday, 11 July 2021
The white-tailed deer (Odocoileus virginianus) is the most widespread and common species of deer in the Americas, and well-known to anyone familiar with the American wilds. They live throughout the whole of the contiguous US, except for the arid south-west, across southern Canada and almost the whole of Mexico. They are also found right across Central America, and into Colombia and Venezuela beyond, reaching the Guyanas and far northern Brazil in the east and as far as Peru in the south.
Sunday, 4 July 2021
An example of this early confusion comes from Dendropithecus, from the Early Miocene of Kenya. Comparatively small, at only around 60 cm (2 feet) in length, and with arms that seem to be adapted to swinging from trees, when it was first named as a distinct genus in 1977, it was thought to be an ancestor of modern gibbons. Despite having a somewhat similar lifestyle and diet, this no longer thought to be likely, and one recent analysis places it as belonging to a very early branch in the ape family tree - just early enough that one could legitimately argue as to whether it really counts as an 'ape' or just a very close relative.
Sunday, 27 June 2021
The largest land animal ever to have lived was surely a dinosaur, most likely a member of the aptly named titanosaur group. But what about the largest land mammal? It's hard to know for sure, partly because "largest" is a vague term that could be interpreted in different ways - do we mean weight or linear dimensions? But it's also just difficult to know when all you have to go on is the skeleton, and that's probably incomplete.
Sunday, 20 June 2021
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
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.