Tentacular struggle

Abstract

The common octopus, Octopus vulgaris, is a solitary animal. When two octopuses meet, one of the following situations can result: (1) if they are male and female, both sexually mature, they can mate; (2) if they are of very different sizes  and the small one cannot escape, the large one kills and devours it1; (3) if they are more or less similar in size, a physical fight may result. The third of these possibilities has been carefully documented for the first time in nature by a sequence of photographs2, some of which are presented here.