Recognition of Individual Conspecifics: Evidence From a 3-Chambered Test With Ghost Crab (Ocypode quadrata)

Trent Robinson

doi:10.1111/eth.70047

The ability to recognize conspecifics can benefit the fitness of species members through a number of avenues. But, for this trait to emerge through natural selection, their ecological context needs to be structured to exert the appropriate selection pressure. Ghost crab (Ocypode quadrata) occupy an environment where encounters with conspecifics are common, and it's also possible that they consistently experience the same individuals over multiple occasions. Individual recognition, then, may be present within this species as an evolutionary byproduct of these circumstances. To investigate this potential, the current research exposed crabs to a sociability and individual recognition test, each lasted 30 min. In the former, animals explored a rectangular arena segmented into three equal compartments. Importantly, a conspecific (Stranger 1) was situated in 1 of the radial compartments, while the others remained empty. In the latter test, a second conspecific (i.e., Stranger 2) was added to the remaining radial segment and animals again traversed the apparatus. These tests offered only visual information about conspecifics and results showed that crabs spent roughly equal time in all compartments during the sociability test. However, when both conspecifics were present, crabs spent significantly more time in the compartment housing Stranger 1. Also, crabs displayed more aggression to Stranger 2, compared to 1. Thus, ghost crabs may distinguish novel conspecifics from those with whom they have had prior experience. Several cognitive mechanisms are elaborated to help interpret these findings. In the end, though, individual recognition is a complex process that appears present within this species, although future research is needed to further this notion.