Effect of sex, hunger and relative body size on the use of ripple signals in the interactions among water striders Gerris latiabdominis

• Gerris latiabdominis produces the ripple signals to compete with others for resources.
• The probability of using signals depends on relative size difference and hunger.
• Relatively small individuals use signals frequently in hunger state.
• The context-dependent signaling pattern is observed only in females, not in males.

Water striders use ripple signals in aggressive interactions between individuals for access to food. We asked whether water striders produce ripple signals more frequently when they are hungrier and when the value of food resources is higher. We also asked if and how the use of signals depends on the size difference between interacting individuals. We found that females used ripple signals more often than males did. The experiment suggested that use of aggressive ripple signals is affected by hunger in females – the sex with high demands for food resources. Among females, but not males, we found out that the probability of using signals in response to the approaching intruder depended both on the degree of hunger and on the size of the focal animal relative to the size of the intruder. Before starvation, the probability of a female using a signal in an interaction with an intruder was higher when the individual's size was larger relative to the intruder. After starvation, the focal individuals were more likely to signal when their size was smaller relative to the intruder. The results are consistent with the idea that these signals may reveal information about the signalers weight or hunger level, and specific hypotheses are suggested for the future studies.

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