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Sounds and behaviour of
sperm whales off Kaikoura
Kaikoura
is a unique area to study sperm
whales, as it is the only known place in
the world where they are present
year-round so close to the shore. Research
started there in 1990. Our team is investigating
several aspects of sperm whale ecology,
developing new acoustic techniques to locate and survey sperm whales, and
assessing the impacts of tourism on the
population.
Sperm whales are among the
most vocal cetaceans, producing their
characteristic clicks between 50 and 70%
of the time. Their vocal behaviour presents a powerful way of investigating their behaviour while
underwater and is also invaluable
for management purposes.
Several types of clicks
have been attributed to sperm whales
(usual clicks, creaks, codas and slow
clicks). However, some of the clicks which
are commonly heard off Kaikoura (surface
clicks) have never been described before,
and their functions are still a mystery.
Off Kaikoura, we are
recording entire dive cycles of
individually identified male sperm whales,
and we are using these recordings to
investigate sperm whale vocal behaviour
and variability in vocal behaviour within
and between individuals, among depths,
locations and seasons.
The diving
ability and pelagic distribution of the
sperm whale has hampered efforts to study
this animal. With increasing pressure
from a few countries to resume commercial
whaling, the need for reliable population size and other ecological data becomes clear.
Sperm whales typically
spend 80% of the time diving, and are
easily missed by visual surveys. On the
other hand, sperm whales click almost
continuously while diving. Acoustic research methods are the obvious way to go with an animal like this. For example, there has been
a trend towards developing methods to use
sounds produced by sperm whales to
acoustically census them.
At Kaikoura, recordings of
sperm whale vocalisations (clicks), are
made with directional and omnidirectional hydrophones. A
directional hydrophone is used to find out the
direction tothe whale and to track the
whale throughout its dive cycle. ID
photographs of the whale's tail are taken
when the whale dives. Software is being developed at
University of Otago to analyse sperm whale sounds and in particular to determine their location in 3 dimensions (latitude, longitude and depth).
Key Researchers: Brian Miller, Miranda van der Linde, Steve Dawson, Liz Slooten
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Behaviour and ecology of bottlenose dolphins in Fiordland
The Fiordland bottlenose dolphin project started in 1990 and has focussed on studying abundance, seasonal movements, diving
behaviour, surface behaviour, sounds, social organisation and the impact of tourism. This
population lives at the southern limits of
the species' distribution.
Human impacts in the area include tourism, freshwater input from the Manapouri Power Station and fishing. There is very little current fishing inside the fiords, but past fishing activity may have had direct and indirect impacts on the dolphins. The effect of freshwater input is likely to be indirect, through ecological changes affecting fish populations. Most of the dolphins are found inside the fiord year-round.
There are seasonal
differences in habitat usage. The dolphins move
along a gradient of surface temperature.
In summer the dolphins are found
predominantly in the inner ends of the fiords, in shallower water where they
give birth. In winter the entrance
areas of the fiord system are preferred.
These
dolphins dive to just over 200 metres water depth, feeding both individually and cooperatively. Behaviours include a 'surface' cluster and an 'aerial'
cluster of behaviours which may describe
different motivational states. Associations among the resident
dolphins of the population showed that the
community is matrifocal; organised around
old and probably post-reproductive
females, together with mothers of young
calves near the centre of interest. Males
are either associated with each other in
the periphery or associated to females in
the centre.
Mark-recapture analyses indicate that the population is declining. Calf survival rates are particularly low.
Key researchers: Rohan Currey, Lucy Rowe, David Lusseau, Oliver Boisseau, Karsten Schneider
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Hector's dolphin behaviour and population biology
Our Hector's dolphin research started in 1984, with a population survey, followed by an intensive study at Banks Peninsula. Since then, the research programme has included a series of population surveys throughout the entire range of the species, as well as research on survival, reproductive rates, movements, behaviour and ecology. Study sites have included the North Island west coast, Westport, Greymouth, Jacksons Bay, Kaikoura, Banks Peninsula, Moeraki, Porpoise Bay and Te Waewae Bay.
Key researchers: Will Rayment, Trudi Webster, Judy Rodda, Liz Slooten, Steve Dawson
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Maui's dolphin
movements and ecology
North Island Hector's dolphins, also known as Maui's dolphins are critically endangered. Their very small population of only 111 individuals (CV 0.44) is found off the North Island west coast from about Dargaville to New Plymouth. Their distribution was much more widespread around the North Island.
This study involves population surveys, acoustic monitoring of harbours and sound recordings. Summer and winter surveys show a seasonal trend in offshore distribution. Like the South Island Hector's dolphins, Maui's dolphins have a strong preference for shallow, inshore waters during summer and are more spread out during winter.
Acoustic surveys of the Manukau Harbour show that Maui's dolphins regularly use the harbour and venture beyond the protected area in the entrance and 'neck' of the harbour. Maui's dolphin sounds are indistinguishable from sounds made by other (South Island) Hector's dolphin populations.
Key researchers: Silvia Scali, Steve Dawson, Liz Slooten
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