Final necropsy results for a deceased Māui or Hector's dolphin that washed up on a remote Port Waikato coastline could not determine the cause of death.
The juvenile dolphin was reported to DOC by a member of the public on Thursday 26 February and taken to Massey University for a necropsy to try and understand what happened to it.
The dolphin was gifted the name Māui Pōtiki from mana whenua, derived from the karakia Pai Mārire. The remains have been returned to Ngaa Iwi o Te Puaha o Waikato and were buried over the weekend. Mana whenua invited DOC to take part in the burial proceedings alongside multiple whaanau from Ngaa iwi o Te Puaha o Waikato.
DOC senior marine technical advisor Anton van Helden says unfortunately, the remains were severely decomposed which meant the necropsy could not definitively determine a cause of death.
"As well as a physical examination, tissue samples were examined under the microscope to try and see whether there was any evidence of disease. The severe decomposition meant this was inconclusive."
An initial assessment had noted some criss-cross patterned cut marks on the dolphin's body. International experts were consulted and did not think they were caused by a fishing net. They suggested a possible cause could be from the dolphin washing back and forth over shellfish beds.
Anton says, "we know there's been speculation these marks were caused by entanglement, however international experts reviewed the marks, and agreed they did not look like they were caused by a net.
"Experts noted the shape, depth and irregular distances between cuts, absence of visible knot marks – which are normally present after entanglement – and the angle which the cuts crossed at.
"There are many reasons this dolphin may have died, including toxoplasmosis or other disease and separation from its mother. Unfortunately, due to the severe decomposition, we don't know in this case."
Results from genetic testing is still pending. The two sub-species of dolphin (Māui and Hector's) look so similar they can't be identified without a genetic test - but based on the location it's likely to be a critically endangered Māui dolphin. At the last survey there were just an estimated 48 to 64 individuals left.
Anton says every dolphin counts and DOC tries to find the cause of death for any deceased Māui or Hector's dolphin that's found, to learn more about the threats facing the species.
"Given how rare these small dolphins are, we need to try and learn anything we can, to better understand the threats facing these iconic dolphins, which are found only here in Aotearoa New Zealand."
Spokesperson says anyone out naturing on our coasts who sees a dead dolphin is asked to call it in to DOC as soon as possible, with an accurate location, so we can collect it quicky.
"The sooner we can get to the animal, the better condition it will be in for necropsy which means we will learn more from it. Every hour is critical."
People out naturing on the water can also help by reporting any sightings using the SeaSpotter app or through DOC's online: Marine mammal sighting form. Māui and Hector's dolphins can be identified by their distinctive rounded dorsal fin, which looks a bit like one of Mickey Mouse's ears.
"If you see a rounded fin, please call it in. Sightings from the public, especially off the west coast of the North Island from Maunganui Bluff to Whanganui, help us learn more about the Māui dolphin."
NATURE LOOKS DIFFERENT FROM HERE
Nature isn't scenery. Nature is a society that we rely on for everything, every day. It's behind our identity and our way of life.
