Kategorie: News
Scientists measure the problem-solving abilities of fish in the wild for the first time
Fish are often regarded as simple creatures, but numerous studies have demonstrated their astonishing cognitive abilities. In laboratory experiments and observations in their waters, fish have shown themselves to be clever animals with often highly developed social behaviour. An international research team has now developed a special intelligence test for fish that makes it possible to analyse their learning and problem-solving abilities directly in their natural habitat.
Traditionally, cognitive tests in fish are conducted in the laboratory. However, stress factors can occur that influence the behaviour of the animals. ‘Fish caught in the wild can show increased stress hormone levels when removed from their natural habitat,’ explains behavioural scientist Alexander Kotrschal from Wageningen University in the Netherlands. This stress can affect the fish's ability to learn and thus reduce the informative value of the tests.
To address this problem, the team developed a mobile apparatus that can be used directly in the fish's natural habitat. The core piece is a plastic ‘feeding board’ with 24 rotating discs attached to it. There is a hole under each disc into which food such as pellets or mosquito larvae can be placed. The fish have to learn to push the discs aside to get to the food. This design makes it possible to test various cognitive abilities, including motor learning and colour recognition. Even simple mathematical tasks have been carried out by providing the discs with different dot patterns.
The flexibility of the apparatus allows it to be placed at different water depths, so that different fish species can be tested in their preferred habitats. A camera attached to the frame records the behaviour of the animals so that the data can be analysed in detail later.
In initial field trials, the intelligence test was carried out on nine-spined sticklebacks (Pungitius pungitius) in the Netherlands and guppies (Poecilia reticulata) in Trinidad. The sticklebacks proved to be adaptive and were able to distinguish colours, with their performance improving steadily over several test sessions. In the guppies, individual differences in behaviour were observed: about 20 percent of the fish acted as ‘producers’, actively opening the discs, while the rest acted as ‘scroungers’ and used the opened feeding sites without becoming active themselves.
This innovative method offers new insights into the cognitive abilities of fish and makes it possible to study their behaviour under natural conditions. This is crucial to obtaining an unbiased picture of their intelligence and social behaviour. Future research could use this approach to uncover further facets of fish behaviour and thus contribute to a better understanding of these often-underappreciated animals.
The intelligence test was presented in a journal article in the journal ‘Methods in Ecology and Evolution’.