Male and Female Mating Behavior is Dependent on Social Context in the Butterfly Bicyclus anynana Erica L. Westerman & Caroline B. Drucker & Antónia Monteiro Revised: 27 January 2014 /Accepted: 11 February 2014 # Springer Science+Business Media New York 2014 Abstract Reproduction is often more costly to females than it is to males, leading to the evolution of ornamented or competitive males and choosy females. Reproduction costs to females, however, can be reduced through nuptial gifts provided by males. These gifts, by increasing female survival or fecundity, can promote the evolution of mutual mate choice, ornamentation, or competition in both sexes, as well as plasticity in mating behavior dependent on social context. We tested for plasticity in male and female mating behavior in a species of butterfly, Bicyclus anynana, where male spermatophore gifts contribute to female survival and fecundity, and where mutual mate choice and ornamentation were previously established. We examined the effect of a sexual competitor on male–female interactions by observing and comparing the behavior of male–female pairs with that of triads containing either an extra male or an extra female. In the presence of a sexual competitor both males and females copulated less than when in male–female pairs, regardless of the direction of sex- ratio skew. Active males increased their own likelihood to copulate, while active females increased their likelihood of being courted. In addition, there was an effect of social context on relative rates of male and female courting and flying. These results J Insect Behav DOI 10.1007/s10905-014-9441-9 Electronic supplementary material The online version of this article (doi:10.1007/s10905-014-9441-9) contains supplementary material, which is available to authorized users. E. L. Westerman (*) : C. B. Drucker : A. Monteiro Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect Street, New Haven, CT 06511, USA e-mail: ewesterman@uchicago.edu Present Address: E. L. Westerman Ecology & Evolution, University of Chicago, 1100 E. 58th St, Chicago, IL 60615, USA Present Address: C. B. Drucker Duke Institute for Brain Sciences, Duke University, Durham, NC 27708, USA Present Address: A. Monteiro Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore