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DRC Studies Show Dolphin Moms Use Signature Whistles to Reunite with Calves

Grassy Key… Dolphin Research Center (DRC), a not-for-profit research and education facility in the Florida Keys, has announced the publication of two research studies, each of which reveals fascinating information about how bottlenose dolphin mothers use their signature whistles to communicate with their calves.  Each bottlenose dolphin has a unique signature whistle that help them to recognize each other.  Because dolphin babies are mobile immediately after birth and separations can occur, mother-offspring recognition is particularly important.

The study titled Further Insights into Postpartum Signature Whistle Use in Bottlenose Dolphins (Tursiops truncatus), published in the journal Marine Mammal Science, showed that new dolphin mothers produce their signature whistle at much higher rates immediately after their calves are born, and continue to do so for up to a month.  This increase helps the calf recognize its mother and allows mothers and calves to reunite if they become separated.  It is the first study of its kind to be conducted with female calves and supports the theory that the increased use of vocal signatures in the post-partum period serves to imprint the mother’s whistle on her baby.  For the study, researchers used arrays of hydrophones (underwater microphones) and recorded the vocalizations of two female dolphins at Dolphin Research Center, Pandora and Calusa.  Recordings were made for 12 weeks total, five weeks before the dolphins gave birth and then seven weeks after each delivered her baby.  

In the study Maternal Signature Whistle Use Aids Mother-Calf Reunions in a Bottlenose Dolphin, Tursiops truncatus, published in the journal Behavioral Processes, a mother dolphin used her signature whistle when asked to retrieve her baby, but not when asked to retrieve inanimate objects. This shows that signature whistles not only are used by dolphins to broadcast their individual identities, but that maternal signature whistle use is important to facilitate mother-calf reunions.  Merina, an adult female, and her young daughter Windley participated in the study.  In the experimental trials, researchers installed hydrophones  in the natural lagoon where Merina and Windley lived.  When Merina was given the verbal and hand signals to “Go get the baby”, she produced her signature whistle, which researchers were able to record.  Unlike previous studies, this was the first to use controls, which means that Merina was sometimes asked to retrieve a random object, such as a toy, that had been placed in her lagoon.  On those trials, she did not produce her vocal signature.  This further demonstrated that the she used her signature whistle only to call her baby.

For both of these studies, DRC’s research team, led by Dr. Kelly Jaakkola, collaborated with Dr. Stephanie King, Research Fellow at Western Australia University, who is known for her acoustics work with dolphins both in the wild and in human care.

Founded in 1984, Dolphin Research Center is the forever home to a family of bottlenose dolphins and California sea lions. Located at 58901 (mile marker 59) Overseas Highway, Grassy Key, Florida, the center is open daily for the public to see narrated behavior sessions and educational presentations, and to participate in interactive programs. The nonprofit organization is funded by admission and program fees as well as by private donors and members. In addition to being one of the most highly respected education and research facilities in the world, DRC is the Licensed Manatee Rescue Team for the Florida Keys and is an accredited member of the Alliance of Marine Mammal Parks and Aquariums and the International Marine Animal Trainers Association. For more information, visit www.dolphins.org.

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