Animals That Borrow Other Species as Defenses, Disguises, and Shelters

Young blanket octopuses possess one of the more startling examples of weapon theft in the ocean. Individuals have been documented carrying pieces of tentacle from Portuguese man-of-war colonies, whose stinging cells can remain functional even after separation from the original organism. The octopus holds these dangerous fragments with its arms, potentially using them as a defensive weapon against predators. This is particularly remarkable because Portuguese man-of-war tentacles contain nematocysts capable of delivering powerful venom to other animals. Blanket octopuses appear to have resistance that allows them to handle the tentacles without suffering the consequences expected for many potential victims. The behavior is most famously associated with smaller or juvenile individuals rather than representing something every blanket octopus spends its entire life doing. Adults develop other striking characteristics, including the enormous web-like membranes displayed by females that inspired the “blanket” name. The species are also notable for extreme sexual size differences, with females growing vastly larger than males. Yet the borrowed-tentacle behavior may be the strangest feature of all.