Posted on April, 03 2014

A research team comprising of science university students, Fishery Administration and WWF staff are conducting a field research study aiming at understanding whether infanticide could be a plausible explanation for the high calf mortality rate amongst Mekong Irrawaddy dolphins. The activity began in January 2014 and will continue for the duration of the dry season until mid-May. It takes place at the Kampi Pool approximately 15km north of Kratie Town.

In order to learn more about the dolphins’ behaviour, the team is employing a boat-based research method called “focal animal sampling”. This method involves identifying an individual dolphin with a recognizable fin shape – all dolphins have been assigned identification numbers based on their fin shape – and following that animal in the boat for upwards of two hours to observe and record the animal’s behaviour. The team records any acts that indicate aggressive behaviour and also collect more general information at three-minute intervals including whether the animals are resting, socializing, travelling, or feeding.

“While the expectation is that the study will inform whether infanticide could be occurring in the Mekong River dolphin population, it will also ideally provide a better understanding of these animals’ behaviour on a day-to-day basis,” said Ms Julia Goss, lead researcher and a visiting Fulbright scholar from the U.S.

The Mekong River Irrawaddy dolphin is Red-listed by the IUCN as critically endangered. WWF-Fisheries Administration’s dolphin population surveys in 2010 estimated that there are between 78 to 91 surviving individuals, but the population is declining slowly. While entanglement in gillnets is recognised as the leading cause of death in adult dolphins, the cause of calf mortality remains unclear.

The Dolphin Workshop held in Kratie in January 2012 developed multiple recommendations for where to prioritize Irrawaddy dolphin research efforts. One recommendation was to conduct a behavioural study during the calving season to describe interactions between mothers and calves. Scientists hypothesize one reason for the reproductive failure of the population is infanticide by male dolphins, or the killing of an infant, or causing enough harm that it will die. In killing an infant, a male dolphin may increase the probability he will breed successfully with an adult female because the female will begin ovulating shortly after her calf dies.