The Effects of Different Types of Intruders on the Level and Characteristics of Territorial Defence Response of Domesticated Male Siamese Fighting Fish

Abstract

This study investigated the effects of types of intruders on the level and types of male aggressive acts at different stages of the egg guarding period in domesticated fighting fish (Betta splendens). The degree of aggressiveness was measured at two reproductive phases in response to three types of intruders: male, female and female that had laid eggs. The nest-holding males displayed the same level of aggressiveness towards intruders before and after the hatching of eggs. Male intruders elicited the highest number of aggressive acts followed by female, and mated female intruders. The highest incidence of gill cover erection, biting, and tail beating by nest-holding males was directed towards male intruders whilst female and mated female intruders were subject to lower and lowest incidence of these aggressive acts respectively. However, female intruders were attacked and chased most frequently and mated female intruders comparatively less frequently whereas male intruders were least subject to these types of aggression.