Each drop bear nest the player builds contains one drop bear, which will automatically leap onto enemies who walk within its attack radius. It kills any enemy instantly, making it perfect for taking out strong, expensive enemies. However, its slow attack rate means it is poor at fighting off multiple enemies attacking the nest at the same time, so can easily fall to groups of cheap, weak enemies. Its attack rate can be upgraded to help counter this, but it still should not be placed in areas where it can easily be swamped.
Unlike other towers, Drop Bear nests don't require a Scotsman to operate them, making them a perfect way to beef up your defences without needing to increase your population. This also means that you don't have to worry about the operator being killed by ranged attacks.