A dead adult Hector's dolphin was discovered at a Southland bay over the weekend.
A Hector's dolphin. (File pic) Photo:
It was the 15th Hector's dolphin that has been found dead around the South Island since November.
The Department of Conservation said the adult female was found on Saturday at Te Waewae Bay and its body has been sent to Massey University for examination.
Its aquatic director, Elizabeth Heeg, said they did not know why so many Hector's dolphins had washed up over the past six months.
"We're waiting for the remaining necropsy results to understand more about possible causes of death," Heeg said.
Thirteen of the dolphins found since November last year have been sent to Massey University.
"They are gradually being examined by the pathologist. So far, we've had results back from necropsies on eight of the dolphins," Heeg said.
Eight of the recent deaths were calves.
On Christmas Day, a decomposed and scavenged Māui dolphin was also found at Muriwai, west of Auckland, but it was not collected.
None of the dolphins showed evidence of being caught in fishing nets.
The results to date have indicated a mix of natural causes including maternal separation for calves, disease and predators.
"There are approximately 15,700 Hector's dolphins around the South Island. The death of any dolphin is always unfortunate, but not entirely unexpected, and isn't likely to have an impact on the population as a whole," Heeg said.
"Clusters of death raise questions about whether they might be connected and a sign of something else going on in the dolphins' environment.
"Equally it could just be a coincidence, and a year in which the number of deaths is at the high end of 'normal' mortality for the population."
She thanked the member of the public who reported the dead dolphin.
"When people are quick to alert us to discoveries of dead dolphins, it increases the volume and value of the information we can obtain," Heeg said.
"We urge anyone finding a dead Hector's or Māui dolphin to report it to DOC via 0800 DOC HOT. It is also important for the public to report live sightings via the DOC webpage, or the hotline."
DOC manages a Hector's and Māui dolphin sightings database, and incident database.
They help to inform management to protect the dolphins.