The Borneo bay cat (Catopuma badia) was first described in 1874, when it was recognised as a new species after examination of the skull of a poorly preserved specimen collected in 1855. It is closely related to the Asiatic golden cat (Catopuma temminckii) and the marbled cat (Pardofelis marmorata). This clade of three species represents one of the earliest felid radiations. Previously, it was thought that the Borneo bay cat was a small island form of the Asiatic golden cat but now it is known that both species diverged around four million years ago, well before the island of Borneo became isolated from Sumatra. The Borneo bay cat is considered to be a monotypic species.

Just a few Borneo bay cat specimens have been described. In late 1992, a female bay cat was captured on the Sarawak-Indonesian border and brought, at the point of death, to the Sarawak museum. The cat weighed only 1.95 kg but was estimated to have weighed between 3-4 kg when healthy. This remains to be the only data regarding the weight of this felid. The Borneo bay cat was thought to be dimorphic in colour like the jaguarundi (Herpailurus yagouaroundi) and the Asiatic golden cat. Its fur is commonly chestnut-red but grey coloured individuals are also known. However, 2015, a black morph with a reddish tail was captured by a camera trap in Gunong Pueh Forest Reserve, Sarawak. The coat of the female captured in 1992 was speckled with black markings. The Borneo bay cat has a long tail of about 73% of head-body length, a rounded head and small rounded ears. The Borneo bay cat’s pelage coloration, body proportions and the extremely long tail bear a striking resemblance to the jaguarundi.

The belly and the underside of the tail are lightly coloured with a whitish stripe running down the ventral surface of the terminal half of the tail. The underside of the chin is white and there are two faint brown stripes on the cheeks. On all specimens, the backs of the rounded ears appear darker-coloured. The forehead is marked with faint dark stripes and there are light markings at the inner corners of the eyes. The back of the head has a dark M-shaped marking. One juvenile specimen showed a completely black coat with a few reddish hairs on its feet and flanks, and a grey face with two black eye stripes. 

The Borneo bay cat is classified as Endangered in the IUCN Red List. Although no data regarding the actual abundance of this felid exist, it has long been considered rare, and is only very infrequently seen or detected during wildlife surveys. Very few historical and recent records of the Borneo bay cat exist and no population density estimates exist. Consequently, it is thought to occur at low densities compared to other sympatric small felids. The number of mature individuals is thought to be around 2,200 animals assuming a density of 1 individual per 100 km². No known Borneo bay cat lives in captivity.

Endemic to Borneo, the Borneo bay cat is known from all regions of the island with the exception of Brunei and South Kalimantan, Indonesia. Its distribution is still poorly understood although the number of confirmed records is increasing. The Borneo bay cat’s secretive behaviour and apparent low population density result in few sightings. Indeed, the first photograph of the Borneo bay cat in the wild was taken as recently as 1998, and it was not until 2002 that this species was recorded by a camera trap. Most museum specimens originated from northern and eastern Borneo, but there are now confirmed records of bay cats from Central and East Kalimantan. From Brunei Darussalam, the only information on the Borneo bay cat is a personal communication mentioned in the 2015 Red List assessment. Historically, the Borneo bay cat may have occurred throughout the island of Borneo and it is hypothesized that its range included most of forested Borneo. Especially the region of Brunei Darussalams contains highly suitable habitat according to a habitat model.

A study from 2003–2006 documented records of the Borneo bay cat in Kalimantan, Sabah and Sarawak but again not in Brunei Darussalam. From Sarawak, evidence in the form of pictures exists for Mulu National Park, Lanjak Entimau Wildlife Sancturay and Gunong Pueh Forest Reserve. In Sabah, the Borneo bay cat was camera trapped in the INIKEA Forest Rehabilitation Project. In Kalimantan, camera trap pictures were taken for example from the Rungan forest between the Kahayan and Rungan Rivers, but it was never captured during a ten-year camera trap survey of Sebangau peat-swamp forest. Many local people who were interviewed in this study were able to identify four out of five species of Bornean felids, except the Borneo bay cat, indicating that this felid is rarer or more elusive than the other Bornean felids.

With increasing camera trapping studies also the number of Borneo bay cat pictures increased. Nevertheless, it is very rarely pictured and its capture rates are much lower than those of the sympatric Sunda clouded leopard which occurs at densities of 1–4 individuals per 100 km². It is not clear if the low detection rate of the Borneo bay cat is due to its rarity or if it is the result of other factors.

The Borneo bay cat appears to be forest dependent and to be restricted to natural and semi-natural forest cover, yet exhibits within these habitats some habitat plasticity. A recent niche distribution study collated a total of 71 historical and recent records. Observations stemmed from a range of forest types, including hill and lowland dipterocarp forest - both primary and highly degraded due to logging activities. Several of the historical records were obtained in close proximity to rivers and wetlands, leading to earlier suggestions that the bay cat may be closely associated with such habitats. It remains unclear, however, whether this is a result of a true habitat association or merely collector/observer bias. In 2017, the bay cat was for the first time recorded from a mosaic heath/peat-swamp forest in Kalimantan. It was also recorded in a rehabilitated forest. Bay cats were not recorded during camera trap surveys of two oil palm plantations in Sabah, lending tentative support to the forest dependent hypothesis. Records have been obtained from 55 m up to 1,460 m, and there is an unconfirmed sighting at 1,800 m from Mt. Kinabalu in Sabah.

There is almost no information available about the Borneo bay cat’s behaviour, ecology, or social or spatial structure. It is rarely observed. It was thought to be nocturnal but recent camera trap images strongly suggest a diurnal activity pattern, with occasional nocturnal activity. All photographs are of single animals, suggesting that the bay cat is a solitary species.

The Borneo bay cat is included in Appendix II of CITES and is fully protected over most of its range. Hunting and trade is prohibited in Indonesia (Kalimantan) and Malaysia (Sabah and Sarawak). The occurrence of the Borneo bay cat in Brunei could not be confirmed so far, where it would have no legal protection outside of protected areas. The Borneo bay cat has been confirmed to occur in the following protected areas: Sabah, Danum Valley Conservation Area, Tawau Hills National Park, Tabin Wildlife Reserve; Sarawak, Gunung Mulu National Park, Lanjak-Entimau Wildlife Sanctuary, Pulong Tau National Park; West Kalimantan, Gunung Palung National Park; Bentuang Karimun National Park; and in East Kalimantan, Sungai Wain Protection Forest, Kutai National Park, Kayan Mentarang National Park.

In 2011, the 1st Borneo Carnivore Symposium was held in Kota Kinabalu, Sabah, Malaysia. It brought together about 2000 people to discucc and determine the most urgent needs for teh conservation of Bornean carnivores. The Symposium:

• Enhanced communication between scientists, conservationists and governmental authorities;
• Collated occurrence records of all Bornean carnivores and modelled their potential current distribution per species;
• Identified conservation priorities and key areas for protection or sustainable management per species;
• Combined the findings per species to identify the most urgent conservation and research needs for the Bornean carnivore community.

The Borneo bay cat is one of the least known felids and for effective conservation measures it is very important to gain more information through research. Thus, there is an urgent need for further studies of the Borneo bay cat in regard of its ecology, status and distribution. Its possible occurrence in Brunei Darussalam and South Kalimantan must also be examined. It is also important to protect as much as possible the habitat of the Borneo Bay cat, and management priorities should include establishment of more and better protected areas in regions where the Borneo bay cat is found. The inclusion of the Borneo bay cat in CITES Appendix I to strictly prohibit its trade should be considered.