The young Irrawddy dolphin that was spotted swimming with a pod of humpback dolphins in a river Kampot province on May 30. MCC
Marine Conservation Cambodia (MCC) and the Kampot provincial Fisheries Administration (FiA) observed an unusual member of a pod of humpback whales swimming in the Prek Tnaot River in Kampot province on May 30.
During one of the MCC’s regular surveys, a young Irrawaddy dolphin and its presumed mother were seen swimming with the pod, said the MCC on May 31.
“This is extremely unusual, as although the two species share some range and can sometimes be found in mixed groups, most interactions that we have seen during our surveys are due to foraging in the same area, not actively seeking one another out,” they explained.
The Ministry of Agriculture, Forestry and Fisheries expressed their excitement at the new-born calf, saying: “Congratulations on the presence of the new baby Irrawaddy dolphin which was spotted by the MCC”.
Provincial FiA director Sar Sarin said a conservation team is continuing to monitor the pod, as it is an unusual sight.
“The baby is an Irrawaddy dolphin, but it is swimming with Indopacific humpback dolphins. It is not clear whether it is the baby of the Irrawaddy dolphin and a humpback dolphin or a case of alloparenting. We are studying it closely,” he added.
There is a population of between 40 and 46 humpback dolphins and 20 to 30 Irrawaddy dolphins in the three protected fishery communities in Prek Tnaot commune, he added.
According to the MCC, when the picture was taken, an adult Irrawaddy dolphin (the presumed mother) was also with the group.
The calf has all of the physical features of an Irrawaddy dolphin calf so although hybridisation has been documented in the past (though extremely rarely), they do not think that this is the most likely situation.
They are continuing to monitor the case. The MCC suggested two main possibilities: Alloparenting, where care is provided to the calf from a non-parent. This can happen within or across species and has been documented before in these species, though rarely.
The second possibility is that the mixed pod is the result of aggressive or sexually-aggressive behaviour. This has been documented several times between these species, often involving a group of male Indo-Pacific dolphins trying to separate a mother and calf.
The MCC is unclear which one of these is the case, but is continuing to monitor the situation. The calf has been seen several times, suggesting it is allowed access to the mother to feed.
The MCC stated that they have been able to identify the dolphins involved through Photo ID although they cannot determine the sex other than by social interactions, for example, if a dolphin is always with a calf, it is presumably a female and its mother.
