The Relationship Between Male Parental Investment and Interbirth Intervals in Atlantic Bottlenose Dolphins (Tursiops truncatus)

Although male care in mammals is rare, reproductive strategies among males and females presumably transpire for offspring survival, benefits to the caregiver, or increased reproductive output. Researchers have described the rearing and socialization of Atlantic bottlenose dolphin (Tursiops tuncatus) calves as an exclusively female role that occurs via direct maternal care. Research has been unable to give the same amount of attention to male parental investment, thus omitting the idea of male parental investment. Acquiring knowledge of potential evolutionary changes in currently noninvesting species, as well as the potential for male investment among polygamous mammalian species, could increase understanding of, and thus redefine, the concepts of parental investment and parental roles. This case study quantitatively examined the relationship between male parental investment and reproductive output by interbirth intervals. Based on parental investment theory, male investment was measured with a behavioral ethogram, outlining the nature of the relationship. Reproductive strategies were measured by birth intervals. Nonparametric statistics revealed male parental investment in the study population exceeded that of unrelated females. Regression analysis revealed a significant relationship between the contributions of male parental investment and reduced interbirth intervals. However, proper investigation of paternal/male investment may reveal dolphins are more socially complex than once thought. Documenting the evolution of paternal investment from a once believed noninvesting species could supplement unanswered questions about the evolution of male care in many human and nonhuman species. Additionally, finding convergent behaviors between humans and dolphins might possibly drive social change for the greater protection of dolphins.