Sunday, 7 June 2015

The Dog Family: Foxes of Asia

Blanford's fox
Asia is a large and varied continent, home to no less than seven species of fox, even using the most narrow of definitions for that term. Three of these, the red, Arctic, and Rüppell's foxes, are also widespread on other continents; the red foxes of Japan, for instance, belong to the same species as those found in Britain and North America. Of the four that are (mostly) confined to Asia, I have already covered the corsac fox of the central steppe lands, but three still remain.

Heading east from Europe the first such species we come to is Blanford's fox (Vulpes cana). This is named for William Thomas Blanford, who first described it as a unique species in 1877 while working for the Geological Survey of India. Blanford, who discovered the animal in what is now Pakistan, seems to have been somewhat surprised that he was first European naturalist to notice it. He may have had a point, since it's fairly distinctive.

It's unusually small, even for a fox, with large ears and a very bushy tail. It is, perhaps, most immediately reminiscent of the better known fennec fox of Africa, and it turns out that there are two good reasons for that. Most obviously, it lives in a very similar habitat, hot and arid, and both species use those large ears to help lose heat without having to pant too much. (Obviously, having good hearing is useful too... there's no rule to say that an evolutionary feature must have only one helpful function). But, secondly, Blanford's fox turns out to be the closest living relative of the fennec fox, the two having parted company during the Pliocene, as the deserts in that part of the world expanded.

Blanford's fox is most common today in Iran, Pakistan, and Afghanistan, with some populations immediately to the north, notably in southern Turkmenistan. However it is also present, albeit in smaller numbers, along the southern and western coasts of the Arabian peninsula and up as far north as Israel and Jordan. It is also known from the Sinai, and probably lives along the west coast of the Red Sea in Egypt, although the evidence for its existence there is rather sketchy, and it's possible that it has just been confused with something else. On the other hand, it is worth noting that it was only confirmed as being present in Oman in 1989, and the Emirates in 1995, so a lack of unequivocal sightings elsewhere may not prove much.

Why are these animals so difficult to find? Well, for a start, they are entirely nocturnal, never moving about in the day if they can help it - they're small enough that being eaten by eagles is a genuine concern. But there's also simply where they choose to live. Blanford's foxes prefer rocky slopes in desolate habitats, being most commonly found in the foothills and on the lower slopes of mountains, in ranges such as the Zagros, Elburz, and Hijaz. Despite an active lifestyle clambering about on those steep slopes, they gain enough water from their food not to need to drink, so they aren't necessarily found close to water sources. While they aren't solely found in mountains - at the opposite extreme, they live below sea level in parts of Israel and Jordan - these are still not places particularly hospitable to humans, and they avoid what farmland there is there.

Hiding in desolate mountain slopes, and only coming out at night, the main diet of Blanford's foxes seems to consist of insects, especially beetles, which they hunt for in places such as dry creekbeds. They also eat fruit - caperbushes in Israel and wild figs in the Emirates - but not to the same extent, and likely changing with the seasons as different options become available. They can eat small vertebrates too, such as gerbils, but, at least in most places that have been surveyed, this is seems to be a very minor part of their diet.

They moult each year, putting on a thicker coat of fur for winter. Given their habitat, however, it's interesting to note that, unlike creatures in more temperate climates, the winter coat is darker than the summer one, which can be quite pale. Hiding against the snow is, after all, a bit pointless in places that never see any snow! While they forage alone, the foxes live in monogamous pairs, and seem to be a good deal more faithful than many others of their kind with no evidence of males cheating on their partners. Possibly they just never get the chance, being spread out too much across the desert mountains. It's quite common for a young female to share her territory with a mated pair, but she's always too young to be sexually receptive, and leaves once she's old enough to find a male of her own.

During winter, the pair huddle together in a den - always some pre-existing shelter they have found, since they don't dig burrows - to keep warm, but they sleep apart in the summer and autumn. They mate in January and February, the mother giving birth to a litter of no more than three black-furred pups. By two months, they are able to forage for themselves, albeit with help from their mother, and most leave before the next winter sets in.

Bengal fox
In the Indian subcontinent we come to the Bengal fox (Vulpes bengalensis), sometimes simply called the "Indian fox". This is widespread across the region, from Pakistan, Nepal, and Bangladesh down to the southern tip of India, and inhabits fairly open terrain, avoiding only mountains, deserts, and dense forest. As this implies, they are somewhat generalist in their habits, although they do have a preference for dry grasslands when they can find them. They only venture into farmlands to take advantage of the extra supply of edible rodents there... although possibly just because domestic dogs stop them getting at anything else they might prefer to eat.

Physically, the Bengal fox is also a fairly typical example of its kind. Which is to say, it's smaller and duller in colour than the red fox, but otherwise broadly the same shape. The black tip to the tail is a distinctive feature, although not unique to this species. Like many foxes, they eat a lot of insects, although they also catch larger animals such as gerbils and lizards, and the pups, in particular, seem to like eating freshly caught rodents.

Although Bengal foxes are often active at night, they are mainly crepuscular, preferring the twilight hours. They have even been observed coming out at midday, although only when it's chucking down with rain, which suggests they really do prefer to avoid bright sunlight. They live, as foxes typically do, in mated pairs, albeit with the sort of casual polygyny that's so unusually absent in Blanford's species. Also unlike Blanford's foxes, they are quite happy to dig and construct quite elaborate dens in which to sleep away the day.

Dens can have anything up to seven entrances, presumably to ensure the foxes always have an escape route, and a positive maze of tunnels covering an area up to ten metres (30 feet) across. Moreover, each pair has several of these across their territory, swapping between them as necessary. By all accounts, they seem to be in a state of more or less permanent construction and renovation, so it's probably fair to say that the foxes really like digging.

They are social animals, however, and, where food is plentiful, multiple animals may share the same territory, and, in some cases, even the same den. They communicate with a sort of chattering cry, and, more rarely, with growls, whines, and a noise that at least comes to close to being a bark. Breeding takes place around November and December, with the litter of up to four pups being born two months later. This, it seems, is the primary purpose of the den, and, while the pups will eventually move around between the others on their parent's territory, birthing itself always seems to take place in the same one year after year.

Tibetan fox
Perhaps the most mysterious of the Asian foxes, however, at least to westerners, is the Tibetan fox (Vulpes ferrilata). This is found on the Tibetan Plateau, north of the Himalayas, including some of the most northerly stretches of Nepal, India, and Bhutan, but primarily in territory claimed by China. Here it lives above the treeline, in regions of alpine meadow and open grasslands that are baking hot in summer yet reach well below zero in winter. Never found below about 2,500 metres (8,200 feet) elevation, and typically much higher than that, its preferred habitat is considerably higher than anywhere even the mountain-loving Blanford's foxes would trouble to visit.

It's sometimes called the "sand fox", although this isn't a terribly accurate description of the terrain it inhabits, and there are other foxes that have the same name anyway. They have thick brownish-grey fur to protect against the freezing winter weather, a white tip to the tail, and an unusually narrow snout and flattened forehead. What's more unusual, however, is that they are amongst the most purely carnivorous of foxes.

Where other species feast mainly on invertebrates, with a side order of fruit and rodents, Tibetan foxes seem to eat to eat almost nothing but pikas - short-eared, non-hopping, relatives of rabbits. Examinations of their dung seem to indicate that these animals constitute over 90% of the fox's diet, and most of the remainder consists of meat they have scavenged from dead chiru, goats, and the like. They hunt during the day, largely because that's when the pikas are up and about, and, while they will also eat rodents and even the odd bit of vegetation if they come across it, this is clearly not what they are looking for.

Indeed, they have been reported to follow bears about, waiting for them to dig up pikas from their burrows, and then chasing down any animals that escape the bear's clutches. The bears, oddly enough, don't seem to mind this, so long as the fox doesn't come to close to them. Evidently, there's enough food to share.

We know relatively little about the social lives of Tibetan foxes. They live in mated pairs, but their territories frequently overlap, so there is plenty of opportunity for mixing. They dig dens on mountain slopes with a good view of the surrounding terrain, presumably so that they can see any larger predators coming, and pick slopes that are sunny, but not directly south-facing. The dens are far less elaborate than those of their Bengali relatives, although they can still have up to four entrances. And, finally, we know that they breed in the spring, with the young remaining with their parents until the winter.

Foxes first entered Asia from North America, crossing over the Bering land bridge. Most foxes today evolved elsewhere, including some that crossed back over the land bridge again in the Pleistocene. But the North American continent is home to at least two species of "true" fox that originated there, and it is to those that I will turn next.

[Photos by Eyal Bartov and Ramakrishnan Aiyaswamy, from Wikimedia Commons. Painting by St George Mivart, copyright expired.]

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