The allometry of ephemeral territory size: insights into interspecific patterns of space use

Abstract

Interspecific patterns of space use in mobile animals have been the subject of considerable study, with allometric slopes often varying between 0.63 and 1.36. Both the slopes and intercepts of these relationships have been typically related to the energetic requirements of the focal animal, in relation to the amount of energy available in the environment. However, other explanations for these patterns are possible, including the ability of the focal animal to move about and/or defend a home range. To provide insight into this issue, we investigated the allometry of patch defence in convict cichlids, Amatitlania siquia , in a laboratory setting while controlling for energetic requirements. By manipulating the distance between two patches of food (0, 20, 40, 60, 80 and 95 cm), we estimated the maximum diameter of an ephemeral territory for 15 dominant fish that differed in body size by almost 40-fold. As expected, dominant fish were less able to defend and monopolize the food as the distance between the patches increased. Furthermore, larger fish were able to defend larger territories than smaller fish. The allometric slope of 1.18 in our study was remarkably similar to the interspecific slopes of home range or territory size in the literature for a broad range of vertebrate taxa. While there are likely multiple causes for the interspecific patterns of space use, our results suggest that the mobility of the defender is just as likely an explanation as energetic requirements.