26.02.2024: The East African Lake Tanganyika is known worldwide for its colorful ornamental fish. The Princess of Lake Tanganyika (Neolamprologus pulcher), one of the most popular of these small cichlids, has now been studied by a team of scientists from the University of Veterinary Medicine, Vienna. The aim was to develop for the first time a simple test to investigate cognitive abilities of a wide range of fish in their natural habitat.

Cognitive abilities vary within and between species. Scientists propose several hypotheses to explain this variation. Two of the best-known hypotheses on the evolution of cognition relate an increased social complexity on the one hand and habitat complexity on the other to higher cognitive abilities.

Several studies have tested predictions derived from these two hypotheses, but only rarely under natural conditions with wild animals and not at all using free-living fish. "However, this is of particular importance if we want to link cognitive abilities with fitness-relevant factors in order to better understand the evolution of cognition," says study first author Arne Jungwirth from the Konrad Lorenz Institute of Ethology (KLIVV) at the University of Veterinary Medicine, Vienna.

First test to investigate cognitive abilities of fish in their natural habitat

According to the researchers, the biggest hurdle in assessing cognitive abilities in the wild has so far been finding a suitable set-up that is easy to use under field conditions. The research team set itself the goal of creating a test that was as simple as possible and could also be used with a variety of fish in their natural habitat.

Stefan Fischer from KLIVV, last author of the study, explains how this was achieved: "We developed a detour test in which the fish had to swim around an obstacle in order to reach a food reward." By altering the difficulty of the task, the behavioural researchers confirmed that this set up is a valid test for investigating the cognitive abilities of wild groups of Neolamprologus pulcher.

Hypothesis testing yields inconsistent results

They then tested specific predictions of the two main hypotheses on cognitive evolution using the most difficult test configuration. "In particular, we examined the differences in cognitive abilities between groups of different sizes inhabiting habitats of different complexity. However, neither hypothesis could be clearly verified in this first pilot study," says Arne Jungwirth. However, the scientists emphasise that the experimental set-up they have developed opens up the possibility of answering a whole range of research questions. Stefan Fischer comments: "We expect that the test we have developed will contribute to a better understanding of the evolution of cognitive abilities in the wild."

 

The article „Estimating Cognitive Ability in the Wild: Validation of a Detour Test Paradigm Using a Cichlid Fish (Neolamprologus pulcher)“ by Arne Jungwirth, Anna Horsfield, Paul Nührenberg and Stefan Fischer was published in „Fishes“.

Scientific article