The Great Humpback Whale Trail, Sep 2015
The humpback whale is one of our ocean’s greatest voyagers. Many of the Polynesian movements throughout the Pacific, including those to and from New Zealand, have humpback whales as part of the narrative. The whales leave their Antarctic feeding grounds in early autumn and travel thousands of kilometres to their sub-tropical breeding grounds. They do not feed during the ~7 month migration and breeding period and when spring comes they move south again to the rich Antarctic waters. Pre-whaling, these whales were abundant in our seas, now they are rarely sighted as they travel south and are still recovering from exploitation; we would like to understand the challenges these whales face by studying the humpback whales migrating past Raoul Island.
Scientists from the South pacific Whale Research Consortium have spent the past 18 years determining the population size and ranging behaviour of Oceania’s humpback whales. Once the prized catch of land-based whaling operations in NZ and Antarctica these whales disappeared from our waters suddenly in the early 1960s. They had been hunted to near extinction by legal and illegal whaling operations; reduced to less than 1% of their pre-whaling abundance.
Almost 50 years later we have used sophisticated non-lethal research techniques including genetic fingerprinting, photo-identification of whale flukes and recordings of whale song to track the gradual but slow recovery of Oceania’s endangered humpback whales on their breeding grounds. With our knowledge of the whales’ breeding grounds, it is time to examine their feeding grounds for possible answers to reasons behind their slow recovery. In 2010, we undertook the Southern Ocean Research Partnership Antarctic Whale Expedition (http://www.marinemammals.gov.au/sorp), a joint Australia – NZ whale research voyage and travelled over 5,800 nm south of 60° (from 150°W to 150°E). Surprisingly there were few whales sighted in Antarctic waters east of NZ and almost all the humpback whales found at the Balleny Islands, due south of NZ, were from east Australia. So where are the humpback whales of Oceania feeding?
In 2008, Karen Baird working for DOC on Raoul Island reported high numbers of whales passing Raoul from September – November with counts of over 100 humpback whales reported during four hour shore-based observation periods. This density is astonishing and suggests the Kermadec Islands are an important route for whales migrating south. Whales are infrequently sighted on their southern migration past mainland NZ, so Raoul is the southernmost location we find humpbacks in the South Pacific as they travel back to Antarctica to feed for the summer.
The Antarctic waters below the South Pacific are extremely remote and hostile so satellite telemetry is currently the best way to understand their southern migration to their feeding grounds. This technology has been successfully used in New Caledonia, the Cook Islands and east Australia showing a general trend for whales to migrate in a south-easterly direction. If this holds true, then whales passing Raoul may be feeding in the Ross Sea region and further eastwards perhaps even towards the Antarctic Peninsula. If we know where they go, then we may be able to determine whether the feeding grounds are a factor in the slow recovery of these whales.
We are undertaking a three week voyage on the vessel Braveheart to Raoul Island in 2015 to satellite tag, photo-identify flukes, record song and collect small tissue samples of humpback whales on their southern migration. We have an international team of scientists from NZ, Australia, the USA and New Caledonia capable of conducting this research and we have access to all historical genetic and photo-identification data from this region. It will be ground-breaking and it will dramatically enhance our knowledge of why these whales are still endangered.
This research is only possible because of support from the following: Ministry for Primary Industries, the Australian Antarctic Division, Southern Ocean Research Partnership – International Whaling Commission, The University of Auckland, Pew Foundation, Conservation International, Blue Planet Marine and Operation Cétacés – New Caledonia. The work will be done under Department of Conservation and UoA Animal Ethics permits issued to Rochelle Constantine.
Raoul Island seabirds
Many South Pacific Islands, including New Zealand, have seen population declines of birds caused by the introduction of alien predators. A significant example is Raoul Island, the largest of the Kermadec Islands located 1,100 km NNE from the New Zealand mainland. Population declines of at least 10 species of seabirds resulted from predator introductions following human visitation and settlement from the 1400s.
The loss of seabirds from Raoul is on a scale almost unimaginable: millions of seabirds would have been wiped out after humans reached the island. One of the world’s great seabird colonies had been all but annihilated. Pest animals were eradicated in 2004 and since then there have been increasing numbers of seabirds breeding. The Meyer and Herald Islands are a few kilometres from Raoul. Seabirds burrow or nest in every suitable place on these islands and the islands provide a source population for seabirds recolonising Raoul Island.
Although recolonisation by seabirds is evident at Raoul, there has been no consistent surveying and monitoring programme to chart the recovery. This expedition will allow Chris, together with Mark Miller (James Cook University, Cairns, Australia), together with members of the DOC team on Raoul to:
- Resurvey sites where Chris and others confirmed seabird breeding from 2008 (Chris’s previous visit to Raoul; some keen DOC staff have provided some information since)
- Visit acoustic attraction sites on the island and check for burrows/sign of breeding around the speakers. Acoustic attraction systems are used to play calls of seabirds and encourage them to start nesting. To date this approach appears to be working very well with some birds found nesting close by.
- Develop with DOC a survey plan for future monitoring of seabird recolonisation. This could be at two levels – one for DOC staff and volunteers to do each year as time permits, and the other for a seabird researcher position one year every five years.
- Fieldwork related to Kermadec Petrels and Wedge-tailed Shearwaters (one of Mark’s study species).