Evidence for this arms race between male and female partners derives from pre-copulatory sexual conflict where males are harmful to females during copulation [ 2, 9, 51, 52].
Copulation with decapitated females was never observed even though males bent their abdomen and attempted to copulate, which suggests that positive feedback from the female is crucial for copulation (M13).
For example, low chamber heights inhibit copulation [16].
In O. furnacalis, the ultrasonic songs cause females to freeze, facilitating copulation [7], [8].
In contrast, short (<0.3 s) 50-kHz USVs are emitted during play [6], copulation [7], and aggression [2].
Males transfer few sperm during copulation [35]; [36], and additional non-sperm direct benefits are unlikely as spermatophores are small [37].
When a female is exposed to conspecific courtship song, she reduces her locomotion to accept copulation [26].
In M. pruinosa, the volume of sperm removed by males increases with the duration of copulation [27], such that removal is not complete for shorter copulations.
The frequency of successful copulation (17.9% of all trials) was similar to the 16.7% found by Houtman [11] under very similar cage conditions.
Some bilateral stimulation of the MAN likely occurs when male sharks and rays approach to bite the female pectoral fins or body during courtship and copulation [23], [46] [48].
Conchs rely on mate-pairing and copulation [4], rather than broadcast spawning or other mating strategies that would require fewer reproductive males.
