Viverrids: Half-Weasel Palm Civets

Banded palm civet

The word "civet", as currently used in English, is a rather broad term, referring to a wide range of vaguely similar-looking animals. Not all of these are even members of the "civet family" as we currently understand it, and even those that are don't form a natural biological group within that family. 

The word was originally Arabic (pronounced something like "zabad") and would have referred to the animals that medieval Arabs were familiar with, which, given how far they traded, would have included both African and South Asian species. These are still regarded as "true civets" today, but the word now also appears in the name of the "palm civets", long thought to be merely a variant of the true sort.

There are at least ten different species commonly called palm civets, one of which of which we now know belongs outside the civet family. The other nine belong to two closely related subfamilies, which were split apart as early as 1864. One of these is that of the hemigalines, a word that literally translates as "half-weasels".

The subfamily is named for the banded palm civet (Hemigalus derbyanus). When it was first described in 1837, it was placed with the other palm civets, but it was given its own genus by French zoologist Claude Jourdan just a few months later. It is he, therefore, who can take credit for the "half-weasel" part of the name.

First identified in Borneo, this lives across that island, and on Sumatra and the Mentawai Islands just to the west. It is also found on the Malay Peninsula, from continental Malaysia to the peninsular parts of southern Thailand. Its presence across the border in southern Myanmar may be sporadic; after over a century without any being definitively spotted, a camera trap snapped a picture of one in 2022. 

The banded palm civet is much smaller than any of the true civets, due in part to the light, slender build that likely inspired Jourdan's name for it. They reach around 50 cm (20 inches) in length, not counting the tail, but typically only weigh 2 kg (4½ lbs), about the same as a chihuahua. The fur is grey to brownish over most of the body, and lacks markings on the animal's underside. The name, however, comes from the presence of five to eight distinct bands of dark brown fur across the back, which appear triangular from the side, with the points facing downwards.

They live in dense jungles, and, while they can be found as high as 1,600 metres in the mountains of Borneo, they prefer lowland forests over highlands. Similarly, while they can be found in disturbed forests, and even oil palm plantations, they are more common in primeval forests relatively untouched by man. They also tend to avoid rivers, although that's possibly because humans don't. 

Analysis of their stomach contents reveals that they eat little but insects and earthworms. The only vegetable matter they have been reported to consume consists of a few dead leaves, such as might be found lying about on the forest floor; they are probably just eaten along with the insects hiding among them. This suggests, and camera trap images tend to support, the idea that they primarily hunt on the ground among fallen leaf litter. However, they have retractable claws and are quite adept at climbing trees, so this may not be their only option.

Hose's palm civet

Like other viverrids, they are nocturnal, usually sleeping through the day in the cavities of fallen logs, although, again, they have also been discovered snoozing up trees, on branches up to 8 m (26 feet) above the ground. They are solitary, marking their territories with rubbings from their perineal scent glands. These are less well-developed than those of true civets, consisting of a pair of deep folds covered by silky hair. Nonetheless, banded palm civets are capable of spraying their contents like a skunk when alarmed, although they remain on all fours when doing so, simply lifting their tail. 

They give birth to one or two young per litter. Initially blind and helpless, they can climb trees by four weeks and hunt for their own food at six.

Hose's palm civet (Diplogale hosei) is named for the collector of the first specimen, colonial administrator and amateur zoologist Charles Hose. It is physically similar to the banded palm civet, but is even more lightly built, with a typical weight of just 1.3 kg (3 lbs). Notably, it lacks any trace of the banded pattern, instead having a uniform dark brown colour over most of the body, with white underparts and white markings on the face.

It lives only in northern Borneo, with the great majority of sightings coming from the states of Sarawak and Sabah in Malaysia. Based on its habitat requirements, it is assumed to also live to the south, across many of the highlands of Indonesian Borneo, but sightings are there are very rare - if not quite non-existent. The only living specimen to be examined by anything other than a camera trap photo was found in a national park in Brunei, although they may also live in other parts of that country, too.

As a result, it's a very mysterious animal, presumably nocturnal and perhaps with a greater fear of man than its banded cousin. Almost all of the sightings that have been made were in dense, primeval jungle far from human habitation. Aside from avoiding humans, this may also be because it prefers highland areas, not venturing below 325 metres (1,000 feet) and typically being found at least half as high again. The highest elevation at which they have been found 1,700 metres (5,600 feet) but that's likely because nobody has looked any higher in such a remote part of the world. 

It's thought that, where both species are found, the banded palm civet occupies the lowlands and Hose's species the hills and mountains, thus ensuring the two do not compete for limited resources. The little we know of the habits of the latter suggest that it has a similar diet and that it, too, tends to forage on the ground; that one living specimen did not try to climb branches while she was held in captivity.

The closest relative of the banded species, however, is Owston's palm civet (Chrotogale owstoni). Named for its collector, a yachtsman with an interest in wildlife, it was first described as recently as 1912, from a specimen found at the mouth of the Songhai River in Vietnam. It is largely restricted to that country, where it is found in the northern and central regions, but individuals have been sighted in Laos east of the Mekong, and the Vietnamese border regions of southern China. It seems reasonable to suppose that it might also exist in parts of eastern Cambodia, but there are no definitive sightings, possibly due to a lack of camera traps in the area.

The fur is greyish to light brown, with a hint of orange in the adults. It is marked by four or five darker bands, similar in shape to those of the banded palm civet, making the two species look very similar. Owston's species, however, has additional black spots on the neck, flanks, and forelimbs, and is typically larger, with an average body length of around 60 cm (24 inches) rather than 50. 

It lives in damp jungles with only limited dry seasons which, in this part of the world, prevents it from going too far west of the Annamite Mountains forming the Vietnam/Laos border, doubtless explaining its restricted range. Within the mountains, it can reach relatively high elevations, having been sighted at 2,600 metres (8,500 feet), but it also lives on the eastern coastal plains. The limited information on its diet suggests that it largely eats earthworms, and so, like the other hemigalines, must spend most or all of its time on the ground. 

Formerly common, the species is thought to have undergone a dramatic population decline since the mid 1990s due to an increase in the demand for bush meat as Vietnam became more affluent. While there is some demand for the animal specifically for use in traditional medicine, most of the hunting is thought to be indiscriminate, a particular problem in the region. While there may be refuges in particularly rugged rocky areas and, at least as of 2004, the species retained a strong level of genetic diversity, the overall decline, combined with its restricted range, means that it has been officially listed as an endangered species since 2016.

Sulawesi palm civet

Moving east, we come to the Sulawesi palm civet (Macrogalidia musschenbroekii), known to occur in at least four different parts of that island. Having said which, it was only discovered on the southeastern peninsula as recently as 2003, so it's entirely possible that it lives elsewhere, given the inaccessibility of some of the options. For a long time, it was considered to belong to the other subfamily of palm civets until genetic studies in the 2010s confirmed it to be a hemigaline. 

In fairness, it does have several differences from its banded relatives. These are not, however, particularly apparent on first sight. It's the largest of the hemigalines, and is sometimes known as the "giant palm civet" despite being no larger than a regular civet at around 90 cm (3 feet) plus tail, and weighing about 5 kg (11 lbs): it's actually the largest native predator on the island The coat is chestnut-brown, fading towards the underparts and marked with vague darker patches along the back. 

A closer look, however, reveals that the more detailed anatomy is different from that of the banded civets. Its ankles can rotate to point its feet backwards, a common adaptation in animals that want to climb down trees headfirst so they can see where they are going. Similarly, the retractable claws have sheaths, as they do in cats, but not in other hemigaline palm civets. Only the female has scent glands,  and these are very simple in form, just a small pit; in males, this is reduced to an apparently non-functional dimple. 

As the form of the ankles might indicate, it's an effective climber, and, unlike its relatives, it spends most of its time in the trees. Here, it eats an almost equal mixture of arboreal rodents and palm fruit, a far cry from the pure insectivory of the other hemigalines. Other than a requirement for trees, they are relatively adaptable in their habitat choices, being as likely to be found in secondary forest as the primeval sort, and even being found in farmland. 

Other than this, we know relatively little. They are nocturnal and solitary and estimates from that newly discovered southeastern population suggested that each animal had a home range of around 150 hectares (370 acres).

Otter civet

Their closest relative turns out to be another unusual hemigaline, one that's sufficiently odd that it isn't normally called a "palm civet" at all. This is the otter civet (Cynogale bennetti), which lives in much the same area as the banded palm civet, but is even more restricted to the lowlands. It is a relatively bland light brownish colour without any significant markings, but it is more its body shape that makes it unusual.

For one, the tail is much shorter than in other hemigaline species, where they are often the same length as the entire body. The ears are shorter and rounder, and the snout is also rounder, unlike that of most other viverrids. The nostrils are located on the top of the nose, rather than facing forward, and they can be closed by muscular action. The whiskers are unusually large and long. The feet are webbed and the scent gland is unusually small and simple, especially in the male.

Aside from the lack of a long, muscular tail, all of these features are reminiscent of those of otters and it's easy to see why it was given the name. So much so, in fact, that when the only known specimen of a supposed second species, Lowe's otter civet (C. lowei) from Vietnam, was genetically analysed, it turned out to be an actual otter. Previously regarded as a high priority for conservation efforts, it was removed from the list of endangered species in 2008 on the not unreasonable grounds that it never actually existed.

We can reasonably assume from the anatomical specialisations that the otter civet is semi-aquatic, but there are so few observations of it that we know little of the details. Certainly, it is often seen in peat swamps and similar wetlands, but it is also known from regular jungles and bamboo forests so it may be more adaptable than we'd assume. One camera trap image caught one climbing a tree, which isn't something you would expect a regular otter to do, although how common this is is difficult to say.

They are thought to eat small aquatic invertebrates but, again, much hard evidence is lacking. They do, however, have unusually sensitive whiskers, with which they are thought to probe along river bottoms in search out prey. Although there are no reliable estimates of their population, the presumption that they rely on swamps, which are being drained and/or polluted in the area, and the knowledge that they avoid areas frequented by loggers, means that it's highly likely to be declining. As a result, they are currently (if somewhat tentatively, given the lack of information) listed as another endangered species.

However there are, as noted, above, two subfamilies of palm civets. They are related, but are thought to have diverged at least 20 million years ago, so they are quite clearly distinct. Next time, I will be looking at some of the species in that other group.

[Photos by JJ Harrison and "Stavenn" from Wikimedia Commons, pictures by Joseph Smit and A.B. Meyer, in the public domain. Cladogram adapted from Veron et al. 2017.]