Sunday, 18 April 2021

All the World's Deer: Deer With Spots

Fallow deer
The fawns of most (but not all) deer species are born with spotted coats, which likely help to camouflage them among the dappled light of a forest. In some species, the spots disappear shortly after birth, while others retain them for a while longer. In five species, however, they keep them all the way into adulthood. I've covered two of these species already: the sika deer of Japan and the um... spotted deer of the Philippines. 

To Europeans, however, the best-known is surely the fallow deer (Dama dama). This is Europe's medium-sized deer, and one of the six original species of deer identified as such in the first list of scientific names in 1758. It lives in woodland areas across most of western and central Europe, preferring broadleaf forests but happy enough with conifers or Mediterranean scrubland. They don't like deep snow, and so aren't found in the Alps or all but the most southerly parts of Scandinavia, but otherwise, they seem pretty adaptable and widespread. Yet, despite being such a familiar animal, they're arguably not really native to the continent.

This depends, however, on just how long an animal has to be present somewhere to be considered "native". Fallow deer have been living wild in Europe for thousands of years, although they were probably only introduced to Britain by the Romans. (Which, admittedly, is still two thousand years ago...) But, if we go back to the end of the last Ice Age, fallow deer may only have been found in what is now Turkey, before being transported to Europe by Neolithic farmers, presumably so they could hunt them for venison when they weren't tilling the ground. 

To be fair, if we want to go back even further, they did live in Europe during gaps between the Ice Ages, and only retreated to Turkey (and possibly southern Italy and Greece, but that's less clear) when the continent became too cold for them. But, either way, their history for the last ten thousand years or so has been heavily introduced by human management and translocation. In more modern times, they have been brought to both North and South America, Australia, New Zealand, and South Africa. Aside from being attractive animals for keeping in parks and the like, they have also long been farmed for their venison.

The spots of fallow deer fade in the winter, as their coat turns a drab grey; since they prefer deciduous forests, it's likely that a lack of leaves in winter makes the sunlight less dappled and the spots less effective as camouflage. But even without this, they are distinctive animals. They are medium-sized as deer go, with adult bucks standing about 90 cm (3 feet) tall at the shoulder, compared with around 120 cm (4 feet) in red deer, and weighing only around a third to a half as much as the latter animal.

In the case of the bucks, two other features also distinguish them from red deer. For one, they have unusually long hairs on the sheath around their penis, but, perhaps more obviously, the antlers are a different shape. Most deer have antlers consisting of a single beam from which a succession of tines branch off - typically just two, but at least five in large species such as red deer. In fallow deer, however, the antlers are palmate.

This means that above the brow tine, and what would be the trez tine in a red deer, the antler flares out into a flattened palm-like sheet with a number of smaller bumps, or "spellers" around the edge. This is unusual in deer and is one reason why it has long been thought that the giant extinct "Irish elk" (Megaloceros giganteus) was more closely related to fallow than red deer - something now supported by multiple lines of genetic evidence from preserved remains.

Persian fallow deer
The fallow deer is sometimes described as having two subspecies, but it is more common these days to consider it as two distinct species, the common one, and the much rarer Persian fallow deer (Dama mesopotamica). This is the eastern form of the animal, once found across the more wooded parts of the Middle East and introduced to Bronze Age Cyprus before being wiped out there at the end of the Middle Ages. Now, they are restricted to a few reserves in Iran, with a recent reintroduction to Israel starting in 1976. Reduced to a total population of just 25 animals in the 1950s, they have now recovered to around ten times that number of adults (and an uncertain number of fawns), but remain very much an endangered species.

Persian fallow deer can be distinguished from the European and Turkish sort by being slightly larger and having antlers that are rather less palmate. The brow tines are unusually short, and there are typically two further tines above but the beam... well, flattens a bit, but doesn't flare out nearly as much as in the other species. They are also reported to be nocturnal, where common fallow deer are active during the day, but this may well be due to their greater desire to avoid humans rather than anything natural in the species.

For most of the year, fallow deer does live in small family groups that occasionally join up into larger aggregations, but stay apart from the solitary adult bucks. The exception, of course, is during the rut, which typically takes place around October. Bucks old enough to mate stop eating and focus all their energy on competing for dominance some time before the rut even begins. Typically, they then establish and defend a particular patch of ground close to where the does live, but there seems to be considerable variation, with some following the does about to create mobile harems, and others using more mixed tactics. The exact method chosen seems to be connected with factors such as the local population density, which circumstances dictating which one works best in a particular situation.

Whichever method is chosen, the bucks spend most of the rut standing about and repeatedly groaning, often until they are completely exhausted (again, they're not doing anything as potentially wasteful of their time as, say, eating). Since they start this weeks in advance of the rut itself, and the tone of the sounds is more connected with dominance rank than the physical characteristics that the females find attractive, it's thought that this probably intended more to warn off potential rivals than it is to woo the does. Nonetheless, each buck does have a distinctive quality to the sound that it makes, so does probably can determine which one is which by the sound of their voice alone.

After the two species of fallow deer, and the sika and Philippine spotted deer, the fifth species of deer to retain the spots into adulthood is the chital or axis deer (Axis axis). These have also been introduced as ornamental animals to places as far apart as the US and Australia, as well as to parts of eastern Europe, and they are about the same size as fallow deer and so could be potentially confused in places where both are now found.

However, the chital has two key physical differences from fallow deer. Firstly, the spots don't disappear in winter, and secondly, the antlers have a typical three-tined pattern, with brow and trez tines branching off the beam and no trace of a palmate sheet. Chital are found wild across most of the Indian subcontinent, where they range in woodlands and teak plantations close to open country, and presumably keep their spots in winter because the climate is too warm for many trees to lose their leaves at this time.

While the males are solitary, females form small herds of up to a dozen or so individuals composed of two or three older does and their respective daughters. At times, multiple herds may gather together into larger groups, especially close to water sources during the dry season. They are most active at dawn and dusk, avoiding both the dark of the night and the heat of the day. In at least one instance, they have been observed following langur monkeys around, apparently to eat any food that the monkeys drop, although the two species may also be able to respond to and take advantage of, each others' alarm calls.

Although does seem to able to breed throughout the year, most fawns are born shortly before the monsoon, when the mother will find it easier to find plentiful food. This may be down to the time of year that males are able and willing to breed, since the growth of their antlers does seem to be seasonal, perhaps determined by when food is most available for them, which may vary depending on where exactly they live.

Despite the similarity of their coat patterns, fallow deer and chital are not especially closely related. Fallow deer form their own distinct branch within the wider deer family tree, while chital form part of an Asian branch that split off earlier still, perhaps as far back as the Late Miocene. Over the last few thousand years, both have been affected by their interaction with humans, to the extent that many fallow deer can be regarded as semi-domesticated. However, there is another species of deer that has owes its very existence to this particular lifestyle, and it is to that that I will turn next...

[Photos by "NotFromUtrecht", Tamar Assaf, and Shankar Raman, from Wikimedia Commons.]

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