19 August 2007

A mother bottlenose dolphin mourning her dead newborn calf in the Amvrakikos Gulf, Greece

On the 3rd and 4th of July, 2007, one common bottlenose dolphin Tursiops truncatus was observed interacting with a dead newborn calf in the semi-closed waters of the Amvrakikos Gulf, Greece.

The behaviour of the presumed mother was observed by Tethys researchers Joan Gonzalvo Villegas and Zsuzsanna Pereszlenyi and by Earthwatch volunteers for approximately 4.5 hours under an oppressive summer heat, in a dead-calm sea.

Whilst researchers must avoid being driven by their own feelings and make arbitrary interpretations, in this case it was quite clear that the mother was mourning. She seemed to be unable to accept the death, and was behaving as if there was any hope of rescuing her calf.

She lifted the little corpse above the surface, in an apparent late attempt to let the calf breath. She also pushed the calf underwater, perhaps hoping that the baby could dive again. These behaviours were repeated over and over again, and sometimes frantically, during two days of observation.

The mother did never separate from her calf. From the boat, researchers and volunteers could hear heartbreaking cries while she touched her offspring with the rostrum and pectoral fins. Witnessing such desperate behaviour was a shocking experience for those on board the research boat.

From time to time, other dolphins from the Amvrakikos Gulf population (estimated by Tethys researchers at approximately 150 individuals), approached briefly to see what was going on. But they did not show much interest, and the mother was soon left alone with her grief.

A source of concern for the researchers was that the mother was never observed diving or feeding during about 2 hours of observations on the first day, and another 2.5 hours on the second day. Bottlenose dolphins are large warm-blooded marine mammals with high metabolic rates, and are supposed to take much food to stay healthy. Spending long hours or even days after a dead calf could potentially weaken the mother and threaten her survival.

The observations were documented by 532 digital photos taken on the first day, and 138 photos taken on the second day. A selection of 48 photos has been posted online and can be viewed at http://www.tethys.org/projects/IDP/deadcalf2007/. The photos refer to both observation days.

Because of the heat, the calf - floating dead at the surface - was quickly decomposing, and the last photos show a bloated calf lacking large pieces of skin and with wounds caused by the decomposition processes. The mother was seen removing pieces of skin and tissue from the corpse - possibly an attempt to 'clean' the calf.

The researchers on board did not feel like taking the calf away from the mother to perform scientific investigations (e.g. a necropsy of the calf). Their decision was intended as a form of respect towards a highly-evolved animal, the deep suffering of whom was obvious enough. All the researchers did was recording behavioural information at 1-min intervals, throughout the observations, and collect a small sample of the calf's skin for future genetic analyses.

The mother is a known animal (ID: 03046) who has been observed in the Gulf since 2003. In September 2004 she had another calf, who apparently survived.

Although Tethys researchers conduct photo-identification surveys in the Gulf almost on a daily basis, at the time when this report is being written the mother was not encountered again. The researchers are now planning to write a scientific note to report this event in full detail. It would be interesting to see if the mother will be encountered in the future, and how she behaves. We hope that eventually she let go, accepting the loss of her baby as an event that - albeit grim - is not infrequent among wild dolphins.

Giovanni Bearzi


For additional information on bottlenose dolphins in the Amvrakikos Gulf see:

Bearzi G., Agazzi S., Bonizzoni S., Costa M., Azzellino A. 2007. Dolphins in a bottle: abundance, residency patterns and conservation of bottlenose dolphins Tursiops truncatus in the semi-closed eutrophic Amvrakikos Gulf, Greece. Aquatic Conservation: Marine and Freshwater Ecosystems 17. doi: 10.1002/aqc.843.

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