Animal Personality Relates to Thermal Preference in Wild-Type Zebrafish, Danio rerio.

It has been widely supported that individual animals express different strategies to cope with environmental challenge. In ectothermic species such as fish, individuals must use behavioral thermoregulation mechanisms to optimize physiological performance. In the present study, thermal preference was tested in groups of wild-type zebrafish, Danio rerio, screened for proactive and reactive animal personalities. Three replicate groups of proactive, reactive, and naive randomly sampled non-screened controls were used for the experiments. The frequency distribution of the animals was recorded in a custom-built multichamber tank under both constant temperature (temperature restricted conditions: TR) and a continuous thermal gradient profile (temperature choice: TCh ranging from 21°C to 35°C). Proactive and reactive animal personalities expressed significantly different thermal preferences and general activity within the temperature gradient. Our results show that proactive fish, generally characterized as being more aggressive, bold risk takers, and prone to routine formation, have a preference for higher temperature environments. Reactive fish, which are shy, less risk-prone, and more flexible, favor medium colder temperatures. This is the first report of thermopreferendum in zebrafish where individual animal personality coupled to freedom of thermal choice has been applied to understand variation in individual preferences within a population.