Yesterday, I happened to catch up briefly with New Zealand orca scientist Ingrid Visser, and she gave me an update on the nine New Zealand orcas who died after stranding last week.
Visser raced to the scene after hearing about the stranding. She has spent decades studying and swimming with local New Zealand orcas, and she feared she was going to know these particular animals. If these killer whales had been from the group Visser studies, it would have meant that 4-5% of New Zealand’s local orca population had stranded and died at one time, a devastating blow.
However, when Visser arrived she didn’t recognize any of the orcas and doesn’t believe any appear in her photo-ID catalogue. In addition, many of the orcas had healed Cookie Cutter shark bites on their dorsals, and worn teeth, which is not typical for the New Zealand coastal orca population that Visser studies.
Visser and others worked pre-dawn to post-dusk collecting samples from the orcas, with the cooperation and support of the local Maori people. In addition to blubber and organ samples, Visser said the heads from all nine orcas were collected. The heads and tissue samples will be analyzed in an effort to better understand why the orcas stranded and died. Visser says that there were no obvious indications of what might have driven the orcas ashore. No obvious trauma, and no blood from the eyes, ears or anus, which can indicate acoustical trauma. None of the orcas was pregnant.
“we’ll do more studies later,” Visser concludes. “At this stage there is nothing that we can tell immediately, and nothing that we could tell might have triggered the stranding.”