Conflict over grooming topography between mandrill groomers and groomees.

Grooming directed to different body areas is likely to imply different costs and benefits for groomers and groomees. In this study, we investigated social influences on grooming topography in captive female mandrills (Mandrillus sphinx). Subordinate groomers preferred to direct grooming to "safe" areas (the back and rump) compared to dominant groomers, while subordinate groomees did not solicit preferentially grooming to safe areas. Groomers tended to initiate grooming episodes from safe areas, while groomees solicited the switch to unsafe areas. Our results highlight a previously unrecognized source of conflict between the partners of grooming, one of the most common cooperative interactions in animals.