Bold and shy individual differences in zebrafish: is there reliability between profiles?

Abstract

Behavioral variation between individuals is related to the species’ biology and the life history of each individual. While boldness is the most studied behavioral dimension in animals, evaluations of behavioral consistency over time and between contexts, as well as which differences matter for separating profiles are still debatable. Here, we divided zebrafish into bold and shy profiles by applying an emergence test (black to the white entrance) three times with the same population of fish. The two groups formed (bold and shy) went through six different behavioral tests: novel tank, open field, sociability, novel object, aggressiveness, and black and white preference, which were employed twice, with an interval of 30 days. Bold animals showed less anxiety-like behavior and higher aggressiveness compared to shy animals, and this pattern remained consistent over time for these two aspects. These features were considered the main factors to classify zebrafish into bold and shy profiles. In addition, the consistency appeared to be context-dependent. The differences noted in the behavioral profiles allowed us to understand how individuals behave facing environmental challenges. in different situations.