Bethany Wallace

Document Type

Internship Report

Publication Date

Spring 2016


The effect of birth order and/or sex on the frequency of aggression received by conspecifics and proximity to conspecifics within the first year of development in Atlantic bottlenose dolphin calves (Tursiops truncatus) has not been fully documented. We assessed the frequency of interactions of the calf with its mother, as well as other conspecifics, and the frequency of aggressive behaviors directed towards four offspring of a single mother. We analyzed the first year of each calf’s life, divided evenly into four developmental stages. Earlier born calves typically received a higher frequency of aggression and maintained a closer proximity to conspecifics. In theory, this could reflect maternal style and accrued experience with each, successive calf. Additionally, aggression targeted at the calf and the calf’s proximity to individuals other than its mother increased with each developmental stage. Male calves were the recipients of significantly more aggression and exhibited a closer proximity to conspecifics when compared to females, which supports other published literature. With time, as a calf became more independent and spent more time solo, the time spent in close proximity to the mother decreased. The frequency of interactions with conspecifics varied depending on the relation to the calf. The frequency of interactions with the calf’s mother significantly differed from all other conspecific categories while the father and siblings only differed from alloparents and non-related juveniles/calves. These results provide a baseline for continued research on the influence of sex and birth order in social development, as well as calf survivability.


Department: MBE

MPS Track: MMS

Location: Dolphins Plus Oceanside, Dolphins Plus Bayside, Island Dolphin Care

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