Friendly neighbour or fiendish invader: individual recognition in the upland bully (Gobiomorphus breviceps).

Individual recognition behaviour is where an organism can identify another based on its individual characteristics. This behaviour is widespread throughout a variety of taxa. To be used successfully, an organism must be able to both send and receive signals. There are plenty of studies identifying recognition both intra- and inter-specifically, particularly in social animals. Territorial fish are a commonly used study species for recognition behaviour studies as these animals need to be able to differentiate threats and rivals from potential mates and familiar neighbours. This study aimed to investigate individual recognition through visual cues in a native New Zealand territorial fish. In chapter two, a literature review was conducted on individual recognition, with a particular focus on visual cues. This review demonstrates that although individual recognition is widely studied, there are gaps in our understanding of the cues used for individual recognition. In particular, I focus on identifying pattern location on an animal’s body and how this influences communication between individuals. There is a lack of research exploring how and why the visual cues need to be placed in a specific location on the body to allow for more direct communication. Another area which was covered in the review was how morphological constraints impact an organism’s ability to use extravagant ornaments as visual cues. Animals’ lifestyles vary among species, but for those with restricted body shapes, like fish, the use of a visual cue other than morphology is crucial for communication. This review provides a comprehensive review on individual recognition and what areas need further investigation. In chapter 3, 30 upland bullies (Gobiomorphus breviceps), a native New Zealand territorial freshwater species, were collected from two locations in north Otago. Fish were paired together for a week to create a familiar pairing before being exposed to their familiar pair and then to an unfamiliar pair. Behaviours of the fish were filmed for 30 minutes when exposed to familiar and unfamiliar fish. The behavioural response of the upland bullies when exposed to familiar and unfamiliar fish were measured using video recordings analysed in BORIS (Behavioural Observation Research Interactive Software). Five behaviours were observed for analysis, aggression, movement, resting, duration inside the territory, and duration spent at the connective wall area. Neither males nor females showed any evidence for individual recognition, as none of the behaviours differed between familiar and non-familiar neighbours, which was likely due to a small sample size and seasonal restrictions due to the COVID-19 pandemic. The repeatability of the behaviours were also estimated. Overall, all behaviours, for both males and females, were highly repeatable, suggesting that the upland bully exhibits consistent individual differences in behaviour (i.e., personality). While the results did not support the hypothesis that upland bullies would differentiate familiar from unfamiliar fish based on visual cues, it poses new ideas around visual recognition cues and shows that the upland bully is displays consistent individual differences in behaviour study species, and thus could be a promising study species for more personality related studies. Future research should focus more on the specific cues used by territorial fish for identification.