Best described as a "unicorn from hell", the sturmbeest fills the same ecological niche as Terran buffalo or other comparable large bovines. Sturmbeest live in large herds often numbering in the hundreds. There are several species of sturmbeest, some adapted to life in the jungle, while others live in plains and forest-steppes. Like most Pandoran wildlife, they are hexapedal to better deal with the low traction caused by low gravity and dense atmosphere of their native homeworld. In Terran ecosystems, adapted forms of sturmbeest tend to be considerably smaller but no less sturdy.
Sturmbeest are massive animals, the largest bulls weighing at 15 tons, towering almost 5 meters at the shoulder and dwarfing even Terran elephants. Because of their massive size, an extremely verdant ecosystem is needed to provide enough biomass for herds of these mighty beasts. Even the somewhat reduced forms adapted to Terran ecosystems through genetic engineering easily rival elephants in size.
Clad in a thick hide with subdermal armor plating that can shrug off even most small arms fire, the sturmbeest has few vulnerabilities, at least compared to Terran fauna. One vulnerability exploited by hunters is it's auxiliary breathing orifices on the shoulders, a feature characteristic to many Pandoran animals with their elaborate respiratory systems. While capable of breathing through mouth and nostrils like Terran beasts, Pandoran animals also have large auxiliary orifices resembling turbine vents near the shoulders, allowing to simultaneously inhale and exhale large amounts of air, providing plentiful oxygen during physical exertion. This excellent respiration is theorized to be one of the reasons why Pandoran animals grow so massive and powerful, and rather easily adapt to the higher-gravity lower-oxygen Terran ecosystems.
The most prominent feature of the sturmbeest, however, is it's massive hammer-like head topping with a single large pointed horn. It serves as the beast's main defensive weapon, the sturmbeest charging and attempting to gore threats much like a bull. A smaller horn-like feature also adorns the beast's chin and is used primarily for digging up roots and scraping bark.
Sturmbeest herds are led by a dominant bull with its harem of cows and their calves, with young beta males tagging along until opportunity arises to start their own herd or displace the old bull. During rut, bulls fight viciously, occasionally goring each other to death. Like all Pandoran megafauna, sturmbeest are placentals, but not mammals, instead feeding their young by regurgitating half-digested plant matter until the calves mature enough to eat solid food on their own.
Because of it's massive size and typically-bovine temper, a sturmbeest should definitely be respected and given it's due space. However, sturmbeest rarely attack unprovoked and will usually prefer to retreat when possible. An individual sturmbeest is more likely to be aggressive and charge, since a herd can easily repel most predators simply by forming an impenetrable circle bristling with sharp horns or simply stampeding the enemy, making further aggression unnecessary. If left alone and not startled, sturmbeest will usually ignore explorers as long as they keep their distance.
Because of their size, sturmbeest have few natural predators besides human and Sidh hunters. Juveniles are preyed on by viperwolves, leonopteryxes and pantheraptors. Lone, sick or injured adults are taken by adult pantheraptors.
Efforts have been made to domesticate sturmbeest with varying degrees of success - a beast this massive would make an excellent source of protein. However, the original Pandoran forms are unfit for human/Sidh consumption, their flesh being toxic to humans and Sidhae from the atmosphere they breathe, only adapted smaller breeds being readily edible. Furthermore, the meat tends to come off as somewhat coarse, requiring further processing to be considered reasonably palatable. Providing such massive beasts with enough fodder and building a suitably sturdy enclosure is also challenging, as is controlling the beast before slaughter. That being said, domesticated sturmbeest are occasionally used as beasts of burden on jungle worlds. The Skargh have also found such use of these animals, adding them to their menagery of draught beasts like the bor'kan.