The Gentle Goliath of the Ocean

Capable of diving more than two kilometres beneath the surface, the sperm whale (parāoa) has the largest brain of any creature to have lived on Earth. Though widespread, the waters off Kaikōura remain one of the few places worldwide where these elusive creatures are found close to shore year-round.

Thousands of people flock to Kaikōura each year to view New Zealand’s magnificent sperm whales in their natural environment. With its unique marine topography, the Kaikōura submarine canyon (part of a mountainous coastal region, dropping up to half a mile deep just off the coast) provides the perfect deep-water habitat and high food availability to sustain a year-round population of mature and adolescent male sperm whales.

Made famous by Herman Melville’s novel Moby Dick, sperm whales were widely hunted by whalers during the 18th, 19th and 20th centuries for their spermaceti (a mysterious waxy substance found in their heads) used to power oil lamps, lubricants and candles, decimating populations before finally being outlawed by the International Whaling Commission in 1986. Globally, it’s estimated there were more than two million sperm whales before commercial whaling, dropping to just 750,000 after.

Sperm whales are a taonga species holding special cultural significance for Māori and other Pacific peoples.

Since 1990, the University of Otago’s Marine Megafauna Research Group has studied the sperm whale population at Kaikōura, making it one of the world’s longest-running studies on cetaceans. With the support of the NZ Whale and Dolphin Trust and Whale Watch Kaikōura, research has looked at population dynamics, behaviour, ecology, and responses to anthropogenic and environmental impacts, as well as novel techniques for measuring the body size of sperm whales.

Dr Will Rayment of the university’s Department of Marine Science has been involved with Kaikōura sperm whale research for more than 20 years and still finds them mesmerising. ‘It’s a real privilege to be able to see them. Nowhere else can you see them this close to shore or so routinely. We are fortunate to have them in our waters. They are simply awe-inspiring.’

Easily recognised by their gigantic heads and prominent rounded foreheads, sperm whales are the largest of the toothed whales. Males can grow up to 18 metres long, twice as long as their female counterparts, and weigh almost three times as much – up to 57 tonnes. They can live for up to 80 years. Females reach sexual maturity at around nine years and give birth roughly once every five years to one calf weighing about a tonne. Gestation lasts approximately 14–16 months. Males appear not to reach sexual maturity until their late twenties.

Female sperm whales live their entire lives in matriarchal groups, rarely leaving the warmth of tropical and subtropical waters. By contrast, males live quasi-solitary lives, and can be found from the Antarctic to the Bering Sea. Young males often hang out in groups until they’re about 30 years of age, where they tend to go their separate ways.

Spending much of their lives hunting in the deep for their prey, sperm whales perform some of the deepest and longest dives of any marine mammal. They can hold their breath underwater for an incredible two hours. At those dark depths, sperm whales rely on highly sophisticated echolocation to stun and hunt their prey.

As part of their ongoing study, Dr Rayment says they’ve come to know more than 200 individual sperm whales, which they have identified using photographs of their distinctive tail flukes. Each individual has a unique identifying code and nickname. In some cases, they’ve known the whales for 30 years.

While the information they have collected at Kaikōura has been invaluable, Dr Rayment says little is known about the status of other sperm whale populations and how they are interconnected. But funding from Coastal People: Southern Skies, a Centre of Research Excellence (hosted at the University of Otago) has allowed the group to expand its research to Northland and Otago.

Building on what they have learned at Kaikōura, Dr Rayment hopes the new research will give them a more comprehensive look at the ecology, movements, and conservation status of sperm whales across New Zealand and the wider Pacific.

‘We think we know about the Kaikōura population, but we don’t know where those males breed or where they are born. There is still so much about their population that we don’t know. Numbers are declining. To better understand it, we need to broaden the picture. Hopefully, this new research will help us discover if and how these populations are connected. We know that individuals don’t stay at Kaikōura the whole time. Some drop in for a day or two, while others are there for a few months.’

For the first time in New Zealand, scientists can study female and young sperm whales, who generally inhabit warmer waters. To assess individuals’ movements in the new sampling locations, they plan to use techniques including photo-identification and comparison of acoustic dialects.

Studies have shown that sperm whales live in distinct clans, each with their unique dialect of morse-code-like clicks called ‘codas’, which they use to communicate. With vocalisations ranging from 100 to 30,000 Hz, it’s estimated that the lower frequencies can be heard by whales up to 60 km away. Canadian sperm whale scientist Hal Whitehead, together with his colleagues, established the existence of seven such clans in the Pacific Ocean.

By using state-of-the-art sequencing and genotyping techniques to analyse both maternal and paternal genetic markers across the genome (obtained from skin samples from sloughs of dead skin whales naturally shed when they swim), it’s also hoped they’ll be able to identify the whakapapa of individual whales, where they are coming from and who else in the Pacific are their relations.

Establishing such connections and looking at the historical and cultural relationships with parāoa is at the core of the project. ‘Our aim is to learn from and empower communities with important relationships with parāoa, including hearing from experts to better acknowledge other forms of knowledge regarding these whales,’ Dr Rayment says.

‘By working with communities to interweave mātauranga (Māori knowledge) and Pacific traditional ecological knowledge with insights from this study, we will gain a greater understanding of parāoa and the impacts they are facing so that traditionally important connections may persist and thrive into the future.’

Acknowledging the relationships coastal communities have with parāoa will help promote those people’s physical and spiritual health and their connectedness with the environment, he adds. The research is intended to support the sustainability of Kaikōura’s whale-watch industry and inform future marine policy in New Zealand.

The mission of Coastal People: Southern Skies is to connect, understand and restore coastal ecosystems through transformative research and local action, with mauri ora (flourishing wellness) of coastal communities guiding its overall vision. With its concerns for changing climate, oceanic conditions and connected communities, the parāoa research is a natural fit, says Dr Rayment.