Tossing marine flares ( not normal flares) and shooting them repeatedly (possibly even if you manage to flat out kill one in a single shot) will be necessary to get them to quit bothering you.
Defending yourself with a close-range tool isn't reliable as they may instead circle around you and take turns performing Hit-and-Run Tactics against you instead of jumping on you to cause a struggle. Wolves used to be this until a patch changed the close combat system since it was hard to figure out what to do with the wolf attacking you.
There's not a whole lot you can do against them unless you've got a safe place to shoot them.
