Sunday, 15 November 2015

The Dog Family: South American Oddities

Maned wolf
Most of the living species of native dog in South America can broadly be described as "foxes", even if they are not directly related to the "true" foxes of the Old World and North America. There are, however, two exceptions, whose appearance is particularly un-fox-like. Analysis of their genes and blood chemistry shows that they do seem to be related to the South American foxes, but not very closely. Indeed, they appear to represent entirely separate colonisations of their continent, diverging from their fellows even before the crab-eating fox did much the same thing. It just so happens that their descendants in the North died out, perhaps under competition pressure from wolves and coyotes, while those in the South continued on to the present day.

The two species are, however, likely each other's closest relatives. Which is surprising when you consider how different they look.

By far the larger of the two is the maned wolf (Chrysocyon brachyurus), which is found in southern Brazil, and in neighbouring regions of Bolivia, Paraguay, Uruguay, and far northern Argentina. It is undeniably a distinctive animal, most obviously because of its remarkably long legs and slender, graceful body. Add to that its unusually long reddish-gold fur, large and mobile ears, and the black mane that runs from the nape of its neck part-way down its back, and we have something that's quite clearly a dog, but which perhaps resembles some domestic breeds more than it does any other wild species. It is also, at least in my entirely subjective opinion, the most beautiful of all the wild dogs.

As one might expect, given the long legs, this is an animal that likes to live in open habitats where it is free to run. It has also been argued that the long legs help give it a good view of the surrounding area when it is walking in long grass, which covers much of the open plains. They actively avoid dense forest, but their attitude to man-made open habitats is more equivocal. On the one hand, they used to inhabit more of Argentina and Uruguay than they do today, and their retreat is likely due to the expansion of agriculture there. But, on the other, they are commonly seen around roads and on the fringes of farmland in Brazil, perhaps because such places are easier to travel through.

Maned wolves are slightly taller at the shoulder than the typical grey wolf, but, because of their slender build, only weigh about a third as much. Even so, that's quite a bit more than most foxes, and one might expect an animal that is more focussed on meat and hunting as a result. But, in fact, maned wolves are about as pure an omnivore as one could hope to find - a number of studies have found that, in the wild, almost exactly 50% of their diet is meat, and 50% vegetable matter. (At least, by number of items consumed; the meat component is larger by mass, since the animals tend to be bigger than the bits of plant eaten).

By far their favourite plants to eat are the aptly named wolf apples, a South American shrub that is related to the tomato and has similar-looking fruit. As for the animal matter, beetles and small rodents are the most common source, the latter of which which they stalk through the grass and suddenly pounce upon like a fox. However, they also eat a lot of birds, even being able to jump into the air to catch them, and and will sometimes go for larger prey too, from armadillo to small deer. However, apart from the wolf apples, which they will actively go and look for, they are largely opportunistic, eating whatever happens to be around at the time.

While maned wolves have occasionally been seen travelling in pairs, they seem to prefer the solitary life. Active primarily at night (and, apparently, the darker the better) they use sound to communicate. Although they produce much the same sort of whines and growls as any dog does, their most distinctive call is the "roar-bark", a sort of very loud sharp growl that seems to be used mainly to allow them to avoid one another. They can even howl like true wolves, although this is only used in the unlikely event that they actually want to meet up, and so isn't often heard.

Of course, one of the occasions when they do want to meet is during the April to June breeding season, especially during the five days that the female is in heat. During this time she is, as one might expect, unusually friendly towards reproductive males, and both sexes perform a lot of scent marking and mutual bottom-sniffing before getting down to business. Pregnancy lasts for 65 days, but what happens next has been little studied in the wild, leaving the possibility that they behave differently in zoos (where, for instance, the parents will have a harder time avoiding one another) an open question.

We do know that, unlike most foxes, the female does not dig a den, preferring to leave her pups somewhere concealed by rocks or vegetation. They begin to take solid food after a month or so, and are fully weaned by seven weeks. After this, they remain in the same general area as their mother, although keeping their own sleeping spaces as far as possible, before finally leaving home. Quite what the father is doing while this is going on is less clear. Certainly, in zoos, he does seem to help by bringing food to the pups and regurgitating it for them, and presumably he must do something of the sort in the wild too, but we can't really say how often that is.

Bush dog
At the opposite extreme, in more ways than one, is the bush dog (Speothos venaticus). About the size of a border terrier, bush dogs have short legs, a short stubby tail, a rounded head, and small ears, features that, taken together, make it look one of the least dog-like of all living canid species. They are typically dark brown in colour, although this can vary from near-black to a pale, sandy shade.

Bush dogs are mainly forest-dwelling animals, preferring to stay close to water wherever possible, although they have also been spotted in more open, lightly wooded, country, suggesting at least some degree of adaptability. They are found throughout central and northern South America east of the Andes, as well as along the Pacific coast in Colombia and into Panama in Central America. This does mean that, at the southern edge of their range, they overlap with the maned wolves, but the two animals live such different lifestyles that it's hard to imagine they compete much.

While the maned wolf is nocturnal, bush dogs are only active during the day. And where the maned wolf is as solitary as it can manage, bush dogs are highly gregarious - the only small wild dog that is a pack hunter. Bush dog packs can number up to a dozen animals, and like those of wolves, they seem to be based around a dominant breeding pair, with many of the other members of the pack being their grown children.

The reason for this pack living is clear: like wolves, and completely unlike foxes, they cooperate on the hunt, allowing them to bring down much larger prey than you would expect for an animal of their size. Indeed, they are remarkably carnivorous for dogs, and eat little, if any, plant matter in the wild. Favoured prey include armadillos and pacas - large relatives of guinea pigs that weigh around 10 kg (22 lbs). But this is by no means all they can eat, and they also hunt smaller animals, such as rabbits, rats, and lizards, and much larger ones such as rheas and deer. They have even been seen to take down a tapir, going for its legs until they pulled it down.

They will chase pacas or capybara into rivers when hunting them, since they seem to be quite good at swimming. When hunting armadillos, one of the animals digs into the burrow, while other members of the pack wait outside side-entrances, attacking it as it tries to escape from their fellow. This cooperative attitude is clearly part of the reason for their success, and it has been observed that bush dog pups do not fight over food, as the young of most other dog species will. Apparently, they just expect that everything will be distributed equitably among the pack, which has less of a dominance hierarchy than that of, say, wolves. The pup's play is similar, being less rough-and-tumble, non-hierarchical, and based around an innate tendency to share things rather than compete with one another.

They are, on the other hand, rather more aggressive to strangers of their own species. Even here, though, they prefer to avoid conflict in advance by copious urine marking of their territory. Indeed, scent marking seems to be particularly important for them, with the males swinging their genitals about to spray as widely as they can, and females doing hand-stands to spray surprisingly far up on trees. Of course, they do communicate by other means as well, having the usual repertoire of whines and growls, with which they seem to be able to express a fair degree of emotional subtlety to one another. The pack keeps together during the day using quiet squeaks to let others know where individuals are, and huddles together at night to sleep. They even wag their tails as a greeting.

We perhaps know even less about how bush dogs breed in the wild than we do for maned wolves. It is clear that only one pair of animals in the pack breed, and it is likely that all the other members of the pack help raise the resulting litter. Females come into heat about once or twice a year, but, at least in captivity, there doesn't seem to be any pattern as to when this happens. Perhaps, rather than having a "breeding season" they just get ready to mate when they feel like it, influenced by social or dietary factors that we humans have yet to unravel.

This brings me almost to the end of the dog family. There is just one more living species to cover, and it is, perhaps, visually the least dog-like of them all...

[Photos by "sarefo" and Paul Reynolds, from Wikimedia Commons.]


  1. I thought it was obligatory, when discussing the Speothos, to mention the story of the generic name, which means "cave jackal". The short of it is that the genus was originally described from fossil cave deposits, before the living species was formally known to science.

    1. Quite right - that should be obligatory. I had a reference and everything ready to hand, and then didn't use it. Silly me - thanks for adding it.

  2. It is also worth noting, as a side bit of trivia, that (at least in captive collections) Maned Wolves smell strongly of cannabis, with the result that one can always tell from a distance if one is approaching an enclosure for the species, and that zookeepers often get complaints from concerned members of the public about the smell!