Anoas are the smallest buffalo species, so they are called midget buffaloes as well. However, they are small only compared to the giant water and African buffaloes (Bubalus arnee and Syncerus caffer), since they can weigh more than 200 kg (441 pounds) and they can be just as dangerous to humans, or even more so. They are endangered in the wild and rare in zoos too, so lowland anoas are kept under supervision of species programmes. Although their needs and behaviour resemble those of their large relatives, there are also some differences which determine their keeping and housing.
The two anoa species, the lowland anoa (Bubalus depressicornis) and the mountain anoa (Bubalus quarlesi) are endemic to the Indonesian islands of Sulawesi and Buton (Butung or Boeton) – which are situated close to each other. Although there is still debate about whether lowland anoa and mountain anoa are distinct species or not, recent evidence using cytochrome B gene haplotypes suggests that the two lines are indeed distinct species. In the past these species were considered to form a distinct genus (Anoa), but now they are specified as members of the Bubalus genus and they are more closely related to the wild water buffalo (Bubalus arnee) than it was thought before.
The physique of anoas resembles that of other buffaloes, but their horns are a little different: they are straight and held close to the back so that they can move through the dense vegetation quickly. The horns are longer on males, reaching 50 cm (20 inches).
Lowland anoas prefer undisturbed lowland forests and swamps, including mangroves. Mountain anoas prefer dense forests close to water sources. They move to shaded areas when the temperature is too high, so they are most active in the morning and in the afternoon. Human disturbance can result in anoas becoming active at night. Just like other buffaloes, they like to wallow in mud and water.
Anoas browse young banana trees, bamboo shoots, rattan sprouts; and eat seeds, fallen fruits and other plants. In addition they drink sea water as well, which is thought to satiate their mineral needs.
The main difference to other wild cattle is that anoas are solitary animals. Mother and daughter pairs are common, and there are a few reports of small herds consisting of up to five individuals. Males are territorial, they have been observed to mark trees with their horns and to scratch the soil after urinating. Lowland anoas are not known to have a specific breeding season. Females generally give birth annually after 275-312 days of gestation. Usually they have one offspring, sometimes twins. Age of weaning is at 6-9 months, they reach sexual maturity at 2 years. Their lifespan is about 30 years in zoos.
Anoas can be kept alone, in pairs, or in small groups of compatible individuals. Males are sometimes inclined to herd females aggressively; in this case they should be temporally separated. Consequently, the necessary conditions for permanent separation should be provided. Males may attack calves too, so they should be separated from the mothers before they give birth. Anoas can be very dangerous to humans both in the wild and in captivity. Females with calves attack particularly aggressively. Their heads are approximately at the height of a human’s abdomen and they can cause very serious injuries with their long and sharp horns.
The outdoor enclosures of anoas must be well structured and large enough. It is recommended to build an enclosure which is divided to – at least – two similarly large parts, which is suitable for separating the animals, but also allows them to communicate through the fence. According to the guidelines, the size of this outdoor enclosure must be at least 100 m2 (about 1000 square feet) for each individual. I think it is an “absolute minimum” size; it should be at least 250 m2 (2690 square feet) for each animal. The indoor box should be at least 14 m2 (about 150 square feet) for each individual – according to the guidelines.
It is recommended that the frequently used areas of the outdoor enclosure (for example the entrance to the stables or feeding sites) be paved. They feel better in naturalistic enclosures with dense vegetation (grass, bushes, and trees), several objects (rocks, tree logs), and a pond for wallowing. Living trees should be protected, for example with wire mesh. A rough concrete floor and straw bedding is recommended for the indoor enclosure. Visual barriers should also be provided, both indoors and outdoors.
In cold and temperate climatic zones anoas need a heated stable where the outside temperature can fall below 7.2 °C (45 °F). They tolerate cool weather, they like going out between 10-15 °C (50-59 °F) too. Freezing temperature leads to physiological stress, of course. Being tropical species, hot weather is not a problem for them, but they tend to avoid direct sunlight, so shady areas should be provided as well.
Anoa diet consists of good quality hay, vegetables, fruits and concentrates. Additionally they like soft wood twigs too. Salt licks should also be provided.
Both anoa species are endangered, and according to the IUCN, the population trend is decreasing. The number of anoas is unknown, but it is estimated that there are less than 2500-2500 mature animals. The fragmentation of population is a serious problem, there are no subpopulations exceeding 250 mature individuals. Two major threats are land conversion to agriculture and hunting. Gold mining and other human activities in forests are also problems. Recent reports indicate that hunting is the most serious threat. Anoas are poached for their meat for local consumption. In protected areas many of them are thought to get caught accidentally by traps set up for wild pigs. Being extremely shy animals, they are very sensitive to human disturbance. The infectious diseases of domestic cattle also threaten them.
According to the ZIMS there are 61 lowland anoas in 24 zoos worldwide, so it is a rare species – but not so much as the mountain anoa: 4 individuals are kept in 3 zoos (Krefeld Zoo, Skaerup Mini Zoo and Batu Secret Zoo).