Ursa Major

Ursa Majors are neither the only Ursa nor the only Major species on Ymir, but if you talk about either term, people will assume you mean these. If you instead talk about 'dem vicious murder bears', which is a well-deserved moniker, everyone will still realise what you mean. But in general, the semi-scientific name is used in both official documentation and normal conversations.   Ursa Minors are comparable to bears from back on Earth, both in size and demeanor. They can be scared off and are mostly solitary. Not Ursa Majors, who travel in packs, also called sleuths, and are extremely territorial. If two sleuths meet, there's only two options. They combine, or they maul each other. And once injured in combat, these creatures just keep going, until either side is dead.   And they're not just aggressive when injured, they're also incredibly fast and completely ignore their injuries. Combined with their thick skull and skin, and taking down one or two might be an option, but a large sleuth is a hazard even for a large group of armed men. To have a decent chance at taking them down in one shot, only the best shooters can manage a distance past a hundred meter. But that hundred meter only buys you nine seconds before they're on top of you. And while they're rushing towards you, getting a good shot in is pretty much impossible.   So when it comes to large groups, do not ever engage them. Even a pair is dangerous and might have a third outside sight, but anything more than a pair requires a large number of shooters to safely take down. And a full dozen requires a small army. Because if only a single one survives, when thousands of kilograms of murderous flesh are bearing down on you, it is incredibly normal to freeze up.   Which brings us to the last part of what makes these creatures so dangerous. Black Lung. See, an infected Taurus species might decide to attack an Ursa Major. They will then kill it then eat its flesh, and get infected themselves. Once the fevers start, they become hyper-aggressive, not towards their own but towards anything else alive. Eventually they may start rampaging and at that point you have a stampede. At that point, all you can do is hide, or take dozens of armed people and go down fighting.   The Science Department does have patrol drones to try to detect such stampedes in advance, but with bad weather, they can go undetected. Stay safe and hide when needed. It is far safer to wait for reinforcements, than to make a foolish move that might not just kill you, but also teach the creatures how dangerous our guns are. The last we can afford, is for them to get smart at killing us.