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The influence of group size on learning and problem-solving in New Zealand spotted wrasse (Notolabrus celidotus)

Foraging dynamics are a fundamental ecological process influencing a variety of other important processes including population dynamics and reproduction. This study investigated the influence of group size on the foraging success of 40 New Zealand spotted wrasse (Notolabrus celidotus) using a problem-solving apparatus. A pilot study using four fish was initially carried out to test equipment and gain an understanding of the individual learning capacity of these fish. Following this pilot study, the full study was separated into four stages. Stage 1 involved observing individual fish attempting a problem-solving foraging task on their own. Stages 2 and 3 increased the group size of fish attempting this foraging task to two fish and four fish, respectively. Stage 4 involved individual fish attempting the task on their own, however, mirrors were fitted to the experimental tank to simulate an increase in group size. Results of this research showed that the presence/perceived presence of conspecifics resulted in increased success rates and reduced latency to solve the problem over time. These results suggest that group size is an important contributor to foraging efficiency in the New Zealand spotted wrasse, as larger groups outperformed smaller groups in most cases, and individual fish with simulated increases to group size outperformed individual fish without this effect. There are three potential explanations for these results. (1) The presence of conspecifics provides passive predator vigilance, enabling individual fish to put more time into solving the foraging task instead of scanning for predators. (2) As a function of increased competition for a limited resource, fish put more effort into solving the foraging task. (3) Social learning resulted in fish learning foraging strategies from conspecifics. It is likely that the effects of reduced predator vigilance and increased competition in larger group sizes influenced foraging success rates of the fish in this study concurrently. Additionally, the pair and group treatments displayed a reduced latency for fish to leave the starting arena and to orient toward the food reward than the other treatments. It is unlikely that these results can be attributed to increased chance due to increased fish density, as fish from the pair and group treatments performed similarly in weeks one and three, despite the group treatment having twice as many fish per trial. This indicates the potential effect of a social learning mechanism, such as local enhancement, in the spotted wrasse in this study. Future studies could further assess the influence of social learning through use of reliable demonstrator fish in an observer-demonstrator experiment. Further study is required to conclusively suggest whether the effect of reduced predator vigilance, increased competition, or social learning has a greater influence on increased foraging success with increased group size in New Zealand spotted wrasse.
Type of thesis
Georgeson, S. A. (2020). The influence of group size on learning and problem-solving in New Zealand spotted wrasse (Notolabrus celidotus) (Thesis, Master of Science (Research) (MSc(Research))). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/14426
The University of Waikato
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