Monogamy without biparental care in a dwarf antelope

Abstract

The only widely accepted explanations for the evolution of monogamy in mammals have been based on the benefits of biparental care of offspring. This is probably because, unless biparental care is important, the most competitive males would be expected to monopolize more than one female. This study investigates whether males are important for offspring survival in a monogamous dwarf antelope, Kirk's dik-dik (Madoqua kirkii), by testing three hypotheses that have been proposed to account for monogamy in mammals. In dik-diks, males could help their mates and young by: (i) defending resources; (ii) defending against infanticide by other males; and (iii) reducing predation risk. Because territorial defence was mainly sex-specific, males did not defend resources for their mates or offspring. Males also made no attempt to kill infants they had not sired, so there is no risk of infanticide. Nor was there any evidence that males reduced predation risk: females were not alerted to an approaching predator sooner when males were present, and only mothers responded to playbacks of the call of a predator which preys on juvenile but not adult dik-diks. This is the first conclusive evidence of the absence of paternal care in any monogamous mammal.