When the weather gets warmer the weasels trade their warm fur coats for shorter, darker colors. They are always in fashion and like to blend in with their area. How big they are: Male Long-tailed Weasels are larger (13-16 inches in length; 6-16 oz) than females (11-14 inches in length; 3-9 oz). Their tails are nearly half the size of their head and body combined. It has a pretty black tip that looks like it was dipped in black ink.