Why do monarchs gather on trees?
This is called clustering. There are no definitive answers to the question of why they do it; they could either all be attracted to the same conditions that exist in a particular spot, or they could benefit from being a group. Possible benefits they could gain from being together include protecting themselves from the elements and or overwhelming predators. Perhaps a group of monarchs can share body heat, and thus gain protection from cool temperatures. Alternatively, a single butterfly in a large group would have a smaller chance of being eaten by a predator.
