Information depends on context: behavioural response to chemical signals depends on sex and size in crayfish contests

Securing information about oneself or an opponent can be crucial to update the likelihood of winning a contest and the relative costs of continuing or escalating. This information can subsequently reduce costly errors. However, information encoded in signals exchanged by opponents can differ based on context. We sought to unravel these differences by pairing male and female crayfish (Orconectes rusticus) under varying sex and size conditions. A pre-optimized technique was used to visualize a well-studied contest signal in crayfish (i.e., urine). Behavioural responses were quantified prior to and after the release of that signal. There was a characteristic de-escalation of behavioural intensity after an opponent released urine. However, behavioural changes after the release event were dependent on the sex and the relative size of the opponents. Urine also significantly altered both sender and receiver behaviour, but lack of behavioural differences suggests urine plays a role in both opponent and auto-communication.