What raises the male sex drive? Homosexual necrophilia in the Sand Martin Riparia riparia

Abstract

We observed three Sand Martin Riparia riparia repeatedly attempting to copulate with a dead bird lying face down on the ground, with its wings spread and lowered. One of the three remained on the ground close to the dead bird and guarded it against copulation from the other two birds. Then, the guarding bird itself attempted to copulate with the dead bird. Based on subsequent dissection the dead Sand Martin was identified as an adult male. Based on our observations, we propose that the observed homosexual necrophilia may be partly explained by the absence of sexual dimorphism in this species and the posture of the dead martin. We suggest that posture is an important trigger arousing male sex drive in a sexually monomorphic species.