Locomotion, interactions and information transfer vary according to context in a cryptic fish species

Abstract

The behaviour of animals is strongly influenced by the detection of cues relating to foraging opportunity or to risk, while the social environment plays a crucial role in mediating their behavioural responses. Despite this, the role of the social environment in the behaviour of non-grouping animals has received far less attention than in social species. Here, we present the results of an experiment on a cryptic species of goby (Pseudogobius sp.), which does not form social groups in its natural habitat. Gobies were presented sequentially with chemical cues relating to food, conspecific alarm and control, while in the presence of conspecifics. The intermittent locomotory behaviour of the gobies, which is typical of many cryptic animals, was influenced by the type of cues presented. Gobies decreased the duration of bouts of stasis in the presence of food cues and were generally more active. By contrast, those detecting alarm cues decreased the duration of movement bouts and were generally less active. In line with previous studies involving shoaling species, gobies in the presence of food cues adopted a more dispersed distribution, while clustering together in the presence of alarm cues. Finally, we used calculations of transfer entropy as a means of inferring information transfer among experimental subjects. In contrast to previous studies that have focused on social species, transfer entropy between gobies was detectable only in the conspecific alarm treatment. Taken together, our results show that members of this cryptic species detect and respond to chemical cues by adjusting their movement and distancing to conspecifics. Furthermore, they augment their own information with social cues but only when they perceive a threat. Animals are routinely exposed to an array of cues within their environment that convey valuable information about risk and foraging opportunities and must adapt their behaviour accordingly. To facilitate this, animals often use information arising from the behaviour of conspecifics to inform their own responses; however, this has rarely been considered in species which do not exhibit strong grouping tendencies. We used a non-shoaling fish, the goby (Pseudogobius sp.), to examine both their responses to ecologically relevant cues and the effect of the social environment on these responses. The gobies adapted their distances relative to one another according to the cues present and responded most strongly to information arising from conspecifics (measured as transfer entropy) in the presence of a potential threat. This demonstrates the potential importance of social information even to species that do not live in social groups with others of their own kind.