The Biology of Four-Horned Antelopes

The four-horned antelope is unique amongst all living wild bovids, primarily because, as its name suggests, it has four horns. I had never heard of this species before seeing a comment, so that immediately sparked my interest in learning all about it. As usual, a document with the sources for the image is used, along with research papers I found useful will be included in the description of this video. I've explored different groups of artiodactyls many times, although it has been a while since my last deep dive. I've covered camels and llamas, porpoises, whales, giraffes, and the pronghorn in previous videos, however, I have yet to explore animals from the largest family in Artiodactyla, the family Bovidae, which comprises around 50 genera and a combined 143 known species. Bovidae belongs in the suborder Ruminantia, commonly known as the Ruminants. This group is renowned for their remarkable ability to digest plant material using a complex stomach with multiple compartments and a fermentation process. This enables them to extract more nutrients out of their food than most other herbivores. The challenge with digesting plants lies in breaking down their strong cell walls known as cellulose. Ruminants have evolved a digestive system capable of breaking down cellulose, thereby maximising nutrient absorption from plant material. When Ruminants consume food, it enters the first two compartments of their stomach. In here, a variety of microbes start the fermentation process on the plant material. Once partially digested, this material, known as cud, is regurgitated back into the mouth. The animal chews the cud to further break down the plant material manually. This process of chewing the cud has even become an idiom, meaning to think slowly, deeply, or carefully about something. A reflection of how bovids, like cows, appear to be deep in thought while chewing. After this additional chewing, the cud is swallowed again and moves to the third stomach chamber where fatty acids and ammonia are absorbed. The remaining material then enters the fourth chamber, which functions as the true stomach when nutrients are absorbed and waste is sent to the intestine for excretion. While the process is more complex than the summary, it should give you an idea of how it functions. There are six families of ruminants which can be distinguished by their horn types, despite their similar digestive systems. First is the chevrotains, or mousetair, in Trigulidae. There are ten species of chevrotains, mostly in South and Southeast Asia, but with one in Central and Western Africa. They lack horns but have large canine teeth, an intriguing adaptation for a herbivore. Next are the two families that I have actually looked at before. The pronghorns in Antelocapridae only have one species alive today, but there are many known extinct species. Pronghorns have unique horns that are bony with a keratin sheath, but are shed and regrown each year. This combines features of both deer antlers and bovid horns. The pronghorn's closest living relatives are the Giraffinocarpi in Giraffidae. Found only in Africa, these species have horn-like protrusions called osteoderms, which are permanent bony growths covered in skin. The last clade includes the deer in Cervidae. They are known for their bony antlers, which they shed annually. Unlike pronghorns, deer antlers lack a keratin sheath, and are covered in velvet, a tissue made of skin, short hair, and blood vessels. Next are the musk deer in Muscadet. Interestingly, these resemble chevrotains more than their actual closest relatives. They lack antlers and instead have elongated canines. Unlike chevrotains, where both sexes have elongated canines, these are only present in male musk deer. The last family is bovidae, the focus of this video. All male bovids have horns, as do the females of some species. These horns are bony projections, usually unbranched and covered in a keratin sheath. Unlike the pronghorns, the horns of bovids are permanent and are not shed and regrown. This family is not only large, but also quite diverse, consisting of 10 sub-families. Although there isn't enough time to cover all of them, they include various antelopes, gazelles, waterbucks, sheep, goats, wildebeests, oryxes, and more. The sub-family that contains the four-horned antelope is bovidae, so that is the one I will focus on. Bovidae is the most basal sub-family and contains about 30 living species in 9 genera. Bovidae is further subdivided into three tribes. Most of the genera are in bovini, also known as the wild cattle. This includes the water buffalos, gaua, yaks, cattle, African buffalos, and bison. Next is the tribe Tregolophinae. This consists of two genera that contain antelope-like bovines, such as kudus, bongos, nihalas, bushbucks, and elands. Finally, the smallest of these tribes is Bozelephinae. They are distinguished by horns with a keeled edge and lacking rings. Bozelephinae has two living genera, each with a single species. The four-horned antelope is one of these two species, so let's have a closer look at Bozelephinae. Several extinct species are also part of Bozelephinae. One of the earliest known is Protracoceros from 11 to 13 million years ago. Although the living species are only found in Asia today, Protracoceros was widespread, with fossils discovered in France, Kenya, Saudi Arabia, and India. Early members of this tribe, including not only Protracoceros, but also Myotracoceros and Tragoportax, are sometimes argued to belong in their own now-extinct tribe, separate but closely related to Bozelephinae. This phylogenetic debate remains unresolved. Most definitely part of Bozelephinae is the Boisea santang, or Dubois antelope. This species lived in Indonesia and Thailand, but went extinct about 750,000 years ago. Estimated to weigh between 32 to 84 kilograms, or 70 to 185 pounds, it was a forest-dwelling browser, eating leaves and woody stems. Both sexes had horns which could grow up to 9 centimeters or 3.5 inches long. The first living species in this tribe is the Nilgai, Bocelephus tragocamelus. Its common name means blue cow in Hindustani. Often referred to as the largest antelope in Asia, its status as an antelope is debatable due to the loose definition of the term antelope. In fact, the scientists naming it clearly weren't sure what type of animal it was either. Its scientific name derives from Greek. The genus name combines bos, meaning cattle, with alephis, meaning deer, and the species name combines trago, meaning a male goat, and camelus, meaning camel. Thus, its full scientific name, Bocelephus tragocamelus, literally means cattle-deer-goat-camel. This brings us to the focus of the rest of this video, the four-horned antelope, Tetracerus quadricornus. It is sometimes also known as the Chausinga, which is Hindi for four horns, but has a variety of other local names in Hindi, Nepalese, and Tamil. Like I did with the nil guy, let's break down the scientific name of the four-horned antelope. Its genus name comes from Greek, combining tetra, meaning four, with cerus, meaning horn. Given its common name, that is not surprising, but what about its species name? This changes the language to Latin, and combines quad, meaning four, and cornus, meaning horn. So, its name is literally four-horned four-horned the four-horned antelope. I'm not sure if that is lazy or creative, but at least it uses different languages to do it. Since its name highlights its horns, let's start there. The four-horned antelope has, you guessed it, four horns. This trait is extremely rare among living animals. While several extinct animals, such as the giraffe relative Dechinotherium rex, had four horns, the four-horned antelope is almost unique among living species. The only exceptions are polycerate sheep and goats. Polycerate is a rare genetic condition that causes them to have more horns, up to eight in some cases. The condition is becoming increasingly rare, as it is being bred out of domestic animals due to the increased risk of injury to farmers. While many breeds of sheep and goats are able to be polycerate, it is considered the normal condition for Jacob's sheep from Britain, and the Wehrhornzieger goats from Austria. In the four-horned antelope, only males have horns. The longer pair are located further back on the head between the ears, while the smaller pair protrude from the forehead. The longer horns can get up to 12 centimetres or 4.7 inches long, while the short ones are only 2 to 5 centimetres or 0.7 to 2 inches long. Like other bovids, these horns are permanent bony growths covered in a keratin sheath. The four-horned antelope is only found on the Indian subcontinent, with the main population in India and a smaller one in Nepal. It prefers dry, deciduous lowland forests, and can be found in both flat terrain and foothills. This shy animal can easily be confused for a skittish steer due to its long legs and slender build. However, its lack of antlers immediately distinguishes it. It is one of the smallest bovids in Asia, weighing only 17 to 22 kilograms or 37 to 49 pounds. These antelopes are generalist herbivores, primarily feeding on leaves and grasses, but also consuming herbs, shrubs, flowers, and fruits when they are available. They are cautious when feeding, often raising their heads to scan for predators. They hide in tall grasses or foliage, with their pale brown coat providing good camouflage. Four-horned antelopes maintain home ranges, particularly the males. These ranges may overlap with others, but are not as defined as in some other species. They mark their home range using both preorbital glands and their horns. The glands release chemicals that other antelopes can detect, while the horns leave visible marks. Although both sexes have preorbital glands, only males have been observed marking their range in this way. Sometimes they use both methods of marking, while at other times they use exclusively one or the other. Females sometimes smell or lick these marks, possibly gathering information about potential mates. Males have also been seen rubbing their preorbital glands on females directly, likely marking them with their scent to claim them or make them more receptive to mating. However, the exact purpose of this behaviour is not fully understood. Despite being solitary, four-horned antelopes do interact with others occasionally, especially during mating. These behaviours are most often seen in males towards females, but have extremely rarely been observed in females to males or in females to other females. They will rub their nose on the other's flanks, usually sniffing as well. They will occasionally groom each other, primarily on their hindquarters, which is an exceptionally rare behaviour among bovids. During the breeding season, males can display dominant behaviours. When he approaches a female, even peacefully, she often responds by lowering her head and neck to the ground. Occasionally, she will sometimes lower her entire body as well, although this is much less common. The male makes her stand up by licking, smelling her or nudging her with his horns. While fighting can occur between females, it is much more common among males. Fights between males and females are exceptionally rare. These encounters usually involve a brief bout of headbutting rather than extended battles. A single hit is typically enough to make the less dominant individual lower its head in submission and flee. These interactions are more about displaying their relative strength than causing injury. Males and females only interact during the breeding season, remaining solitary for the rest of the year. Although little is known about their reproductive habits, breeding is believed to occur so that the births happen after the rainy season. Interestingly, individuals in captivity in England give birth during the winter. This timing coincides with the rainy season in India, suggesting that they adhere to their native breeding season instead of adapting for their local conditions. Pregnancy lasts for approximately 8 months, which is relatively long compared to other similar sized ruminants. Females give birth to one or two young, which will remain hidden in dense foliage or grass for the first few weeks of life. They then start following their mother as she forages, and stay with her for about a year. Based on captive studies, females are thought to reach sexual maturity at less than 2 years old. In males this is unknown, but they begin to grow their horns from around 10 months old, with sexual maturity likely occurring later. Most reproductive information comes from captive individuals, so there may be differences in the wild. Four-horned antelopes often have difficulty reproducing in captivity, especially when compared to other ungulates of a similar size. It is unclear whether this is due to low reproductive success in the species, or if captivity negatively affects their reproduction. Either way, they are not common in zoological parks, which could pose a challenge for their conservation if the wild populations ever become reliant on captive breeding for survival. Four-horned antelopes are estimated to live for 12 to 17 years. Interestingly, there is no difference between the life expectancy in males and females. This is unusual, since females of most species tend to live slightly longer. This longevity estimate is based on captive individuals, and could be biased, as they may live longer than their wild counterparts due to the absence of predators and other threats. The four-horned antelope is listed as vulnerable by the IUCN with an estimated population of 7,000 to 10,000 individuals remaining. Their range has significantly decreased from their historical distribution. While they were always restricted to the Indian subcontinent, their current populations are very patchy and disjointed. Habitat loss is the primary cause of this fragmentation. As a shy and reclusive species, the four-horned antelope struggles with human encroachment. Deforestation, urbanisation, and pollution are major drivers of their decline. All remaining subpopulations are believed to be quite small, with less than 1,000 individuals estimated in each fragment. Habitat fragmentation poses a significant problem for many species, with reclusive animals being particularly vulnerable. I have already mentioned that four-horned antelopes struggle with increased human interactions. Fragmentation will escalate these encounters, as antelopes are forced to venture into open areas more frequently. Although they can adapt to a variety of habitats, from forests to grasslands, the concern is heightened when fragmentation results from expanding human cities and infrastructure. As their remaining viable habitats shrink, their access to resources such as finding enough food or clean drinking water may become increasingly limited. Additionally, a major issue is the isolation of the remaining individuals, making it more difficult to find mates and disrupting gene flow between populations. The reduced genetic diversity that this causes can result in weakened resilience against diseases and environmental changes. Finally, isolated populations are more susceptible to local extinctions, and the loss of any populations can have a cascading effect on the overall survival of the species. Four-horned antelopes occur in several protected areas, which is a good start for their protection. Unfortunately, due to landscape fragmentation, these national parks and reserves are not connected, isolating the populations from each other. The Indian government has even established wildlife sanctuaries specifically for their protection, such as the Rangayana Durga four-horned antelope wildlife sanctuary. This is in the Indian state of Karnataka, and was established in 2011. The sanctuary covers an area of 77 kilometers squared, or just under 30 miles squared. In 2017, an eco-sensitive zone was established around the sanctuary, prohibiting commercial or industrial activities that could harm the environment within the sanctuary. The antelopes are further protected by India's Wildlife Protection Act, which outlaws their hunting and harvesting. Since over 90% of the remaining four-horned antelopes are in India, this law protects most of their population. The Nepalese four-horned antelopes are not protected by this law, but are included in CITES Appendix 3. This, at least, restricts their international trade, as CITES requires people to obtain a permit before trading them. Habitat fragmentation is certainly not their only threat. Their unique four-horned skulls make them popular targets for trophy hunters. Despite the Indian laws and CITES restrictions, poaching is still common. The skull is considered a status symbol, and sells for a high price on the black market. They are also sometimes killed for their meat, as some believe it is very high in protein, despite its reportedly bad taste. Poaching incidents often go undiscovered because the small size of the antelope makes its remains easy to hide. Even in reserves, four-horned antelopes face several threats, such as competition with nearby livestock. Farmers often let their livestock graze inside the reserves, which reduces the availability of the healthy plant parts that four-horned antelopes prefer. Additionally, there is the risk of disease transmission from cattle or feral dogs. Diseases like foot and mouth disease or rabies can be devastating, and can be transmitted through shared water sources. I hope you enjoyed this video. Four-horned antelopes are not only the sole member of their genus, but they are also unique as the only wild animals alive today with two pairs of horns. Due to their shyness, they are rarely seen by humans. Thankfully, measures are in place to protect them from the numerous threats they face. However, habitat fragmentation remains a significant issue and exacerbates many of the other pressures. This makes their continued conservation essential to ensure their survival. Thank you for listening. Feel free to suggest another group of animals you'd like to see me cover in the comments below.