Sunday, 26 March 2023

The Raccoon Family: Coatis

White-nosed coati
The common raccoon is the only member of the family whose scientific name dates back to the official dawn of biological taxonomy in 1758. However, people continued sending him new specimens to catalogue and, just eight years later, in a later edition of the same work, Linnaeus added two further species that we would now also place in the raccoon family - albeit, he initially described them as civets.

These two animals were coatis (or "coatimundis"), with one first identified from Mexico, and the other from Brazil. They were given their own genus by Gottlieb Storr in 1780 when he first named the raccoon family. It's probably fair to say that, to modern eyes, Storr's classification seems the more reasonable of the two; coatis look a lot more like raccoons than they do like civets.

The northern species is the white-nosed coati (Nasua narica) and it lives, not just in Mexico, but throughout Central America and along the Pacific coast of Colombia. The precise extent of the occurrence of the species in South America is unclear, with recent reports from Colombia's Caribbean coast and from coastal regions of Ecuador. In the north, they are found throughout much of Arizona and western New Mexico, with occasional reports from southern Texas. Like the local raccoons, the coatis of Cozumel Island have sometimes been identified as a separate species, but, in their case, this seems to be very much a minority view today.

One reason we can be reasonably confident that at least some of these reports are accurate is that coatis are distinctive animals. They are about the same size as raccoons, and their coat colour is highly variable, ranging from pale reddish to near black, and their tail has the same striped markings, although, again how visible these are can vary between individuals. But what makes them distinctive is their unusually long snout, with a white muzzle and markings around the eyes and on the cheeks.

They use their long noses to poke about in leaf litter, sniffing out tasty invertebrates which form about half their total diet. In true omnivore fashion, the other half consists largely of fruit, although they will also eat the occasional small vertebrate or feed on carrion if it should present itself. They are adept at climbing trees, and will forage in them for food, but seem to prefer staying on the ground, even on the dry season when invertebrate prey is less common. They are mainly active during the day, perhaps because many of their predators are nocturnal.

In most areas, their preferred habitat is forest, often tropical jungle but this is not something that's widely available in, say, Arizona where they tend to stay close to rivers, but do occasionally venture out into more barren terrain. In the tropics, where trees can still be found some distance upslope, they reach at least 2,900 metres (9,500 feet) elevation in the mountains.

By the standards of carnivorans (rather than, say, antelopes or deer) female coatis are unusually gregarious. They travel in "bands" of up to 25 individuals or more, the great majority of which will be related through the female line. The exact size of any given band fluctuates over time as members move away or die and particularly large bands eventually split into two, even if they then don't immediately head away for pastures new. 

Since they aren't pack hunters and forage individually even when travelling with others, it is thought that the primary reason for this behaviour is much the same as it is for many herd animals; the more eyes available to the group the easier it will be for them to spot predators such as pumas or jaguars. This can be particularly advantageous at waterholes (presumably because the predators know where they are) and smaller bands spend less time at such places before darting back into cover. Indeed, availability of water, rather than food, seems to be the primary determiner of how much land a given band will occupy, which can vary tenfold even in the more comfortable parts of their range - it's naturally larger still in places like Arizona. 

Another advantage of band-living is the opportunity for cooperation, and while adults don't tend to go so far as sharing food with one another, they do share in child-rearing duties and groom one another to remove parasites. It's perhaps notable here that the few band-members that are not closely related to the majority, having presumably joined from elsewhere, receive fewer of these forms of cooperation, and sometimes even face aggression, while still benefiting overall from the safety of numbers.

The behaviour of males is rather different. They typically remain in their mother's band until the age of two, at which point they are basically driven out to live solitary lives from then on, returning only to breed. Although this does expose them to predators, it seems that their larger size makes it easier for them to defend patches of food, which they will do aggressively. However, a few adult males do sometimes travel with female bands that include their mother or other close female relatives, being tolerated in part because they do not try to mate with them. 

The breeding season is short, lasting no more than four weeks, and ranging from January to March depending on the latitude. Unusually, the mating behaviour has been reported to involve males climbing trees and calling to females passing beneath; a female who likes what she hears rapidly climbs the tree to join her preferred partner. This sort of behaviour is fairly common in birds, but is much less so in mammals and notably doesn't involve the sort of mate-guarding that one might see in deer or similar animals where the male also displays but subsequently maintains a harem.

South American coati

About ten to eleven weeks later, the pregnant female leaves her band and climbs into a tree to give birth away from ground-travelling predators. She produces a litter of up to six young, although it is not unusual for some of them to die before weaning, and rejoins her band once the young are able to travel independently at around 40 days old.

The word "coati" comes from the native Tupi language of Brazil, where it refers to the more southerly of the two originally described species, the South American coati (Nasua nasua), also called the ring-tailed or brown-nosed coati. (English, incidentally, is a little unusual here; most other Germanic languages use a variant of "nose-bear"). They closely resemble the white-nosed species but were identified as distinct even back in the 18th century because their snout is dark brown or grey, and they have fewer white facial markings.

South American coatis are found throughout almost the whole of tropical and subtropical South America east of the Andes, being absent only from the Caribbean coast and far eastern Brazil. They inhabit a wide range of forest types and apparently spend more time in the trees than their northern kin do, especially where edible bromeliads are common. They are even found to some extent in areas with relatively dense human populations - one study found that they do better on land controlled by the Brazilian Air Force than in urban state parks, perhaps because there are fewer predators there.

They also eat much the same sort of food, feeding mainly on leafy vegetation, insects and millipedes, switching to a higher proportion of fruit when the latter are in short supply. In the case of millipedes, which are rather noxious, they roll them in their paws before eating to get the defensive secretions off, and behave similarly when removing the spiky rind from certain fruits. They act as important dispersers of fruit seeds in the forests, with some fruit benefiting from their removal of the tasty pulp.

South American coatis may live in even larger bands than do members of the northern species, with up to 30 individuals reportedly being common, with a few twice that size. These are apparently led by a dominant male, in a variation from the white-nosed species, although otherwise the group consists entirely of adult females and young. Another unusual feature within the group is that juveniles of both sexes apparently "outrank" the adult females, obtaining superior access to food and other resources. This, it would seem, is not dominance in the traditional sense, but more a feature of the females letting the aggressive little brats get away with whatever they want.

Mountain coati

If that sounds like a certain species of primate, the complexity of social interactions within South American coati bands has been likened to that of some monkeys. This is marked by high levels of reciprocal behaviour that must require the animals to remember exactly who has helped them in the past.

The two remaining species of coati were not identified as distinct until much later, and were considered to be a single species until 2009. The western mountain coati (Nasuella olivacea) inhabits the northern part of the Andes in Colombia and Ecuador, and has also recently been seen in Peru. The endangered eastern mountain coati (Nasuella meridensis) is found in the Merida Mountains, a northeastern extension of the Andes into Venezuela. Both species are roughly half the size of the lowland coatis, with a uniform brownish-grey colour, except for the stripes on the tail, and a nose that is even longer and narrower. Although traditionally placed in their own genus, having apparently split away before the Ice Ages, this has been recently questioned on chromosomal and genetic grounds.

Mountain coatis, as their name suggests, live in higher elevations than the other species, at least 1,300 metres (4,300 feet) above sea level, and, rarely, even above 3,200 metres (10,500 feet). These areas are mostly dominated by cloud forests, although they may also live above the tree line in the "paramo" habitat of the higher Andean slopes. 

Their diet contains significantly more invertebrate matter, especially beetles and millipedes, than the lowland species, with vegetation providing less than 10% of their total food. Otherwise, we know relatively little about them, although it's likely that their habits are similar to those of their lowland kin. For instance, they are sometimes seen in groups, but sometimes alone, which would suggest a similar split between all-female bands and solitary males... but there are, as yet, no detailed studies to confirm this.

The western species is relatively tolerant of humans, being found close to high-altitude cities such as Bogota, while the eastern one lives in areas so remote that human encroachment isn't yet an issue. Even so, the latter is known from such a comparatively small area, and so few sites within that area, that it is provisionally listed as an endangered species, pending any clear evidence to the contrary.

While there are several other members of the raccoon family living in Latin America, only one other, besides the common raccoon and the white-nosed coati, lives in the US. It is to that, and its closest relative, that I will turn next.

[Photos by Terry Stone and "Rufus 46", from Wikimedia Commons. Painting by Ulisse Aldrovandi, in the public domain.]

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