Abstract
Boldness and aggressiveness are crucial behavioral traits in the field of animal personality, and both have important ecological and evolutionary significance. As swimming crabs (Portunus trituberculatus) are aggressive, their production is affected; thus, it is important to study their behavior. To assess the relationship between boldness and aggressiveness of male P. trituberculatus and the differences between their different life stages, we determined the individual differences in these two traits in juvenile and adult crabs under laboratory conditions. Based on the k-means cluster analysis, boldness of crabs is classified according to their rush to adventure, and aggressiveness of crabs is classified according to their aggressive behavior toward conspecifics. The results show that the personality classification of juvenile and adult crabs was consistent. Boldness was divided into three levels: bold, middle, and shy. Aggressiveness was divided into two levels: aggressiveness and non-aggressiveness. The personality of juveniles and adults P. trituberculatus males was significantly different; juveniles presented higher aggressiveness and lower boldness than adults. Additionally, a significant positive correlation between boldness and aggressiveness of adult crabs was verified (P = 0.001, ρ = 0.271). However, this correlation in juvenile crabs was not significant (P = 0.702, ρ = 0.042). These preliminary results indicate that the personality of P. trituberculatus males has developmental plasticity and adults have the boldness-aggressiveness behavioral syndrome.
Highlights
Animal personality refers to the consistent individual differences in behavior across time and context (Réale et al, 2007; Biro and Stamps, 2008; Dingemanse et al, 2010)
Boldness and aggressiveness are two personality traits that have received increased attention (Wolf et al, 2007; Ariyomo and Watt, 2012), as these traits affect the interactions between preys and predators (Coleman and Wilson, 1998), individuals, and conspecifics (Su et al, 2019)
The interquartile range (IQR), which represents the dispersion of each variable, of juvenile crabs regarding boldness, was approximately sixfold higher than that of adult crabs (Table 2), indicating that the boldness of juvenile crabs was more dispersed than adult crabs (Figures 3C,D)
Summary
Animal personality refers to the consistent individual differences in behavior across time and context (Réale et al, 2007; Biro and Stamps, 2008; Dingemanse et al, 2010). Boldness behavior refers to the tendency of individuals to take risks and explore new environments (Wilson and Godin, 2009). It is the basis for the study of animal personality and is common in natural populations (Wilson et al, 1994). The juvenile pumpkinseed sunfish (Lepomis gibbosus) exhibits boldness in both foraging and predation-risk environments (Coleman and Wilson, 1998) and the bold male fiddler crab (Uca mjoebergi) is highly aggressive, bold males fight to gain new territory, while shy males avoid fights by evicting females or occupying empty zone (Reaney and Backwell, 2007). Overly bold or aggressive water striders (Aquarius remigis) (Sih and Watters, 2005) and hermit crabs (Pagurus bernhardus) (Bridger et al, 2015) have reduced reproductive success rate, because when extremely aggressive males are present, females are completely inactive and spend most of their time in waters where they rarely mate, indicating that extreme boldness and aggressiveness can be a disadvantage
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