Condition‐Dependent Variation in Male Drumming Displays, Female Responses and Mating Success in the Jumping Spider <scp> <i>Saitis barbipes</i> </scp>

ABSTRACT Male courtship signals are generally a product of strong selection on their capacity to attract mates and convey signaller quality to achieve mating success. Given the costly nature of courtship signals, their expression may also be influenced by the quality of the courted female. However, such effects are rarely considered. I tested how male and female nutritional conditions affect male drumming intensity, female abdomen lifting behaviour and mating success in the jumping spider Saitis barbipes , known for its elaborate drumming displays. As expected from a condition‐dependent signal, well‐fed males drummed more intensely than hungry males and thereby increased their mating success. Yet, contrary to expectations, males often reduced drumming towards well‐fed females. Well‐fed females were observed to frequently lift their abdomens, which strongly reduced male drumming and mating success. Curiously, males that achieved mating despite female abdomen lifting did so with lower drumming intensity than in nonabdomen lifting trials. These results illustrate that condition‐dependent behaviours in both sexes can interact in unexpected ways, shaping male investment and influencing courtship outcomes.