Is blood thicker than water? The role of kin and non-kin in non-mother-calf associations of captive bottlenose dolphins (Tursiops truncatus)

• Calves with kin available associated with more conspecifics than calves without kin, suggesting potentially different social strategies.
• Calves showed no conclusive association preference in frequency, but a potential early preference for kin might be present for some individuals.
• Calf identification, calf age, and associate age are likely much more influential in calf associations than kinship.
• Calf association durations did not differ significantly between kin and non-kin and no obvious differences in context were observed.
• Though kinship has proven important in older dolphins, it does not appear to be as important in early, developmental bonds.

Relationships are important for social animals and kinship can play a vital role. Still, occurrence and function of kin bonds (aside from mother) in delphinid calf associations, alloparenting, or calf rearing are poorly represented in the literature. This study examined the role of kin and non-kin in non-mother-calf associations for a managed population of bottlenose dolphins. Calf associations were event sampled to determine if kin and non-kin differences existed in frequency or duration. Calves with kin present exhibited a higher average number of associates than calves without kin. Yet calves showed no conclusive association preference in frequency; though some individuals showed early signs of developing kin preferences. Duration and context of associations did not differ between kin and non-kin, suggesting they serve the same developmental purpose. However, personality, calf age, and associate age played a greater role in the formation of calf associations, supporting the notion that calves choose associates with similar traits, aiding in their development in difficult and changing environments. Though kinship is important in the formation of relationships in older dolphins, it appears that outside the mother-calf bond, there are other more influential factors, such as age, personality, and sociality in the formation of early developmental bonds.