Parasites may lead in male rodents to the excretion of pecular odours. Females refuse copulation with Mus musculus males parasitized by, e.g., the coccidian Eimeria vermiformis, the nematode Heligmosoides polygyrus, or lice like Polyplax serrata. On the other hand other parasites increase the attractivity of infected males (e.g., tick‐infested Mus musculus). However, also males may refuse infected females (e.g., if the latter are infected with Plasmodium chabaudi).