Substance over Style: Calf characteristics drive maternal care in Indo-Pacific bottlenose dolphins
Description
Individual variation in behavior is the substrate for selection. In bottlenose dolphins, individuals have been shown to have repeatable behavioral strategies that persist over decades. To what extent might such persistent individual differences impact maternal care (i.e., maternal style), or is care instead determined more by calf characteristics? Based on 40+ years of study of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Shark Bay, Australia, we investigate patterns of maternal care and its impact on post-weaning survival. Using focal follow data (n=428 follows) of 22 mothers of 68 calves, we examine maternal behavior when calves were <2 years old. Behavioral metrics include infant position, a type of mother-infant contact and ‘carrying’ used as a proxy for direct maternal care, time spent together, and behavior while together. Maternal care metrics were not individually repeatable; rather, calf characteristics such as age and condition were more important in determining the amount of maternal care. Somewhat paradoxically, calves that did not survive to age 4 (average age of weaning in this population) and those who weaned later than average, received more direct maternal care than those who survived, suggesting mothers try to compensate for calf condition. In sum, unlike altricial mammals where mothers have direct control over offspring (by carrying and caching), patterns of maternal care are largely driven by the attributes of the calf in this precocial species.