Nicky Wiseman

Bryde’s whales

In the Hauraki Gulf

Written by , and      

A resonant whoosh of air and water blasts skywards as a Bryde’s (pronounced “broode­rs”) whale surfaces 60 metres in front of us. The twin blowholes on the top of its head are clearly visible. The whale curves its back and dives, showing its sickle-shaped dorsal fin as it slides silently below the surface.

We stop our inflatable boat’s outboard motor and wait. There’s no way to tell where the whale will come up next apart from following its “footprints”—the oily swirls that appear on the surface as tail thrusts propel the whale along underwater. The nearest is only 20 metres away. A pale patch appears under the surface as the whale rolls slightly and exposes the white underside of its body. It watches us as it cruises alongside the boat, only a metre or so down.

We don’t expect it to surface and blow again just metres away, but that’s what it does. The vapour cloud drifts over, enveloping us with a smell like rotting fish. The whale turns and a huge eye appears above the water as it watches us. Then it dives again, passing only metres below our stern. Its massive tail drives it silently forward, down through the concealing blue.

This isn’t our first encounter with a Bryde’s whale, but it’s by far the closest. As anyone who has had a close encounter with a whale knows, the experience is unforgettable.

There are two groups of whales (order Cetacea): toothed whales (suborder Odontoceti), such as dolphins, orca, beaked whales and sperm whales; and baleen whales (sub­order Mysticeti), which include rorqual, gray and right whales. The name Mysticeti (from Ancient Greek for upper lip, mustax, from which the word moustache derives) is a reference to the baleen plates, made of keratin and fringed with hair, that hang from the upper jaw of these whales and are integral to their feeding (see below). The Bryde’s whale we have just seen is a rorqual whale.

The smooth "footprint" left by a Bryde's whale as a sweep of the tail propels it along a few metres down.
The smooth “footprint” left by a Bryde’s whale as a sweep of the tail propels it along a few metres down.

Rorqual whales, which make up the family Balaenopteri­dae, are unique among cetaceans in bearing pleats on their undersides that allow their bodies to expand during feeding. On Bryde’s whale, these pleats run along the throat and belly, extending to the umbilicus. All six species of rorqual whale have been sighted in coastal New Zealand waters, the others being the blue, fin, sei, minke and humpback whales.

Sei and Bryde’s whales are frequently confused, being similar in size and general appearance, however Bryde’s whales are slightly shorter than sei whales and the sei’s pleats end mid-body. In addition, the principal distinguishing feature of Bryde’s whale is the presence of two raised lateral ridges that run from the tip of the snout to the twin blowholes, one on each side of the median ridge that passes down the centre of the head of all rorqual whales (all baleen whales have two blowholes, toothed whales only one).

Bryde’s whales have been observed in the Pacific (North and South), Atlantic and Indian Oceans and are spot­ted mostly between latitudes 40°N and 40°S. While most baleen whales migrate long distances between polar and tropical seas, Bryde’s whales keep to a relatively restricted home range. Around New Zealand they are most common between North and East Capes but have been reported as far south as Cook Strait. They are found year-round in the Hauraki Gulf, frequently being seen off Tiritiri Matangi and Waiheke Islands. Visible usually as they surface amidst shoals of fish or krill while feeding—which they do individually or in small groups, along with common dolphins, diving Australasian gannets and other seabirds—they are in fact the most commonly sighted large whales in the coastal waters of northern New Zealand. Despite this, surprisingly little is known about them, either in New Zealand or any­where else.

A Bryde’s whale usually reveals itself with a cloud of va­pour as it blows, or by exposing its large black back and distinctive small, curved dorsal fin on the surface. It will often employ the feeding method known as lunge feeding, where­by it rolls on one side to swim through a shoal, its mouth wide open and, usually, a fluke raised out of the water, look­ing rather like an orca’s dorsal fin. The whale gulps in large amounts of seawater containing fish or krill, then contracts its throat pleats to expel the water. Often after gulping a mouthful, it raises its head above the surface at an angle and huge amounts of water cascade from the sides of its mouth as the baleen plates sieve out the solid food (see photo opposite). This is quite a common sight in the Hauraki Gulf. A Bryde’s whale has 285–350 baleen plates. Keratin, the fibrous protein of which they are composed, is the same material as human hair and fingernail. Greyish-white in colour and springy in composition, each plate is about 19 cm wide and 50 cm long.

Bryde’s whales are slender as whales go and grow to an average length of 13 m, with the largest animals about 15 m. Males are slightly smaller than females. Body colour is variable, but usually the back and dorsal fin are dark grey or black and the underside is almost white. The flippers are slender and curved along the front edge to an almost pointed tip. The hooked dorsal fin is similar in shape to that of a bottlenose dolphin. Researchers use photographs and other records of distinctive nicks and cuts in dorsal fins for individual identification.

Both males and females become sexually mature at about 12 m in length. Males are then 9–13 years of age and females about 10. It is thought that females give birth less than once every two years. Gestation lasts about a year, and most births in the Southern hemisphere occur during late summer. Calves are 4–4.5 m long when born and are weaned at around six months old, by which time they have grown to some 7 m in length.

Various populations of smaller rorqual whales around the world are known collectively as Bryde’s whales. As is commonly the case where DNA analysis is used to identify species, several species are now recognised where previously there was thought to be only one, and the picture remains fluid. The common name, Bryde’s, was bestowed in honour of the Norwegian consul and founder of the South African whaling industry Johan Bryde. The whales were first de­scribed in 1879 and the scientific name Balaenoptera edeni (Eden’s whale) was given after Ashley Eden, the British High Commissioner to Burma, who had provided the type specimen (an animal stranded on the Burmese coast). A sim­ilar species, B. brydei, was described in 1913 from the South African coast. Recently the two species were confirmed as separate species, B. edeni being rather smaller than B. brydei. A third genetically distinct species, B. omurai, was described in 2003 by Japanese cetologists following analysis of speci­mens from the Indo-Pacific and the Sea of Japan. Complicat­ing the picture further are a number of other distinct forms possibly meriting species or sub-species status.

The world population of all forms of Bryde’s whale has been estimated by the International Whaling Commission at around 90,000 animals. The whales that frequent the Hau­raki Gulf have been identified as B. brydei, which elsewhere in the world is considered an offshore species.

Although Bryde’s whales are now the most common large whale in northern New Zealand waters, this may not have been the case before the arrival of European and American whalers. Until whaling began around the New Zealand coast in the early 1800s, humpback and southern right whales were common. Between 1843 and 1845 over 100 shore stations hunted southern right whales, and more than 200 whaling ships called at New Zealand ports annually. The effect on whale populations was devastating. By 1850, southern right whales had been almost completely wiped out, and whalers began targeting humpback and sperm whales.

Bryde’s whale grows to 15 m and is very similar to a sei whale in appearance, only a little shorter and somewhat slimmer. This slenderness is likely related to the species’ preference for warm water and hence a reduced need for blubber. It is the only local species of rorqual whale (sei, minke, blue, humpback) not to migrate to Antarctica each summer to feed.

Almost all the whale was utilised, the most important materials being baleen and the high-quality oil obtained from blubber. Baleen was used most notoriously to stiffen corsets. It could be split along its parallel fibres and, after being softened by steam, was easy to shape. Once dry again it held its shape. Come the late 19th century, whale popula­tions had been depleted, and cane, steel and, later, plastic were used in place of baleen. Following a fall in the price of whale oil when cheaper mineral oil became available, the whaling industry virtually collapsed.

New Zealand whaling enjoyed a brief resurgence in the 20th century, and Bryde’s whales were a familiar sight to the whalers who operated from Whangaparapara, on Great Bar­rier Island, until as recently as the 1960s. Several were caught but they were usually considered too slim to be worth pursu­ing. Whaling quotas lumped Bryde’s and sei whales together, so the precise numbers taken are not known.

A preliminary note on Bryde’s whales in the Hauraki Gulf was published by New Zealand cetologist William Dawbin in 1956, while a dead specimen washed up in 1963 was also described. Subsequent study between 1999 and 2002 was un­dertaken by DOC (see sidebar). Since then, one of us—Nicky Wiseman—has been studying the Hauraki Gulf Bryde’s whales for a PhD at the University of Auckland.

“I’ve spent three years on the water,” she says. “In my first year I went out nearly every day, but dropped back to three or four days in my second year and only two or three days last year.”

Most of Nicky’s trips were aboard Dolphin Explorer, a 20 m commercial launch that takes passengers out to view whales and dolphins in the area between Auckland, Kawau Island and the Coromandel Peninsula. These lasted about five hours. Nicky also made longer forays on several smaller vessels belonging to Auckland and Massey Universities, often out to Little Barrier Island. All biopsy samples were taken on these trips.

“In the early days, we’d see whales on about a third of our trips, but towards the end of my research this had risen to 90 per cent. I don’t know whether this was because the whales were more abundant or because we became better at finding them. The whales were spotted by their blows, and sighting birds and dolphins as they are interested in the same aggregations of fish that the whales feed on.”

Nicky and the other passengers aboard Dolphin Explorer have witnessed the full range of Bryde’s whale behaviour: resting, feeding, travelling, milling about and, most dra­matically, breaching, when a whale shoots vertically out of the water. Since the whales are 12+ m long, and the water in the gulf is only 45 m deep, it isn’t easy for a large whale to get up sufficient vertical speed for a decent leap. Breach­ing doesn’t involve a whale taking water into its mouth, so isn’t thought to be a type of feeding behaviour. Feed­ing occupies 50–70 per cent of a whales’ time. Unlike, say, southern right whales, resting Bryde’s whales don’t spend a lot of time lying on the surface. Resting seems to involve slow travelling rather than immobility. Typical activity entails diving for three to four minutes, surfacing to take a couple of breaths about 20 seconds apart, then diving again. Bryde’s whales can travel considerable distances in the course of a single day—for instance, from the west side of Tiritiri to the Coromandel coast.

Whales generally dine in the company of dolphins and gannets on large schools of fish. Find the diving gannets and you’ll often find Bryde’s whales. Despite the size of the mammal, its eye (below) is relatively small.

Apart from mother–calf pairs and feeding aggregates­ up to eight whales have been seen together around a shoal of fish—Bryde’s whales seem to be rather solitary animals. Only rarely—seven or eight times in three years—did Nicky observe pairs of adults, which might have been in­volved in mating or courtship activity. Ten whales were seen regularly, perhaps two or three times a fortnight for a time, whereas others were only encountered occasionally. Some calves, accompanied by their mothers, she observed repeatedly, taking pleasure in their steady growth.

With practice, a blow can be spotted at a considerable dis­tance. Once Dolphin Explorer had approached to within 400 m of a whale, Nicky could determine the animal’s speed and direction. At 200 m, she could start making observations of its behaviour and take photographs of markings that could be used for identification. To obtain biopsy samples, she had to get to within 30 m—only possible and allowable in the smaller university boats.

“During the course of my work, I got 29 biopsy samples, from which I was able to analyse mitochondrial DNA,” she explains. “There turned out to be quite a lot of genetic variation, and some of the individuals showed similarities to whales from the North Pacific.”

Bryde’s whales are unusual amongst rorqual whales in that they inhabit only tropical, subtropical and warmer temperate waters and it seems some individuals may be crossing the Equator.

Over the past 10 years, two of us—Jenny and Tony En­derby—have observed Bryde’s whales from our home at Leigh, from which we look over the Hauraki Gulf towards Tawharanui, Coromandel Peninsula and Little and Great Barrier islands. We have seen whales every month except April, suggesting they are present around the Northland coast and Hauraki Gulf all year.

Most years from October to January, Bryde’s whales move close to the Leigh coast and into Omaha Bay. In Oc­tober 1999, we recorded 42 spouts over a five-minute period from a pod of Bryde’s whales less than a kilometre off Cape Rodney. There were at least 10 whales in a tight group, splashing and rolling. As there were no birds or dolphins with them and they weren’t lifting their heads or lunging, it’s unlikely they were feeding. They eventually dispersed, leaving us to wonder what we had witnessed.

For two to three months over the summer of 2006, Nicky Wiseman found Bryde’s whales close to the coast near Coromandel. This was unusual as in that area the whales are normally further out at that time of year, and on no other occasion did she observe whales spending more than a few days in one place.

Whereas many larger whales, such as sperm, humpback and blue whales, lift their tails clear of the surface as they dive, Bryde’s whales never do. Having surfaced and blown, a whale usually slides its head beneath the water before exposing its dorsal fin, arching its back and disappearing beneath the surface.

Bryde’s whales occasionally spy-hop, lifting their heads clear of the water as if trying to get a view. In 2004 we watched as one whale did this repeatedly in a three-hour period. The lifts became progressively lower, and after each appearance the whale would blow, dive shallowly, roll over and lunge feed with a fluke clear of the water.

Bryde’s whales tend to be shy: approach one in a boat and it will usually move away, dive for five minutes and resurface several hundred metres off. The Marine Mam­mals Protection Act 1978 prohibits boats from approaching closer than 50 m to a whale. This is for the safety of both the whale and the boat. At times, however, whales seem deliberately to approach boats, perhaps out of curiosity. Nicky has had several encounters with whales swimming slowly past a boat and gazing upwards.

“On another occasion, a whale swam seven or eight times around the boat,” she recalls. “I think at least some of them are inquisitive. Probably adolescents.”

All marine mammals within New Zealand’s Exclusive Economic Zone (EEZ), which extends 200 nm offshore, are protected.

A mother and calf blow simultaneously after a five minute dive. The paired blowholes that distinguish baleen whales from toothed whales are clearly visible on the mother.

Japanese whalers, as part of their country’s “scientific whaling” programme in the North Pacific, currently catch and kill up to 150 minke and 50 sei whales annually, along with 50 Bryde’s and 10 sperm whales. It is possible the programme will be broadened to include a quota of humpback whales, listed internationally as vulnerable. Despite the “scientific” label, many scientists argue that such data as are obtained by the programme—which began after the impo­sition by the International Whaling Commission (IWC) in 1986 of a moratorium on commercial whaling—are of no great value.

Possibly the main threat to New Zealand’s Bryde’s whales is collision with large ships. Some whales in the Hauraki Gulf bear scars from collisions, while others have been im­paled on a ship’s bow and carried into port. Such accidents may account for a number of whale deaths in New Zealand waters but the only known fatalities are of animals that wash ashore dead. Carcases are usually towed to a remote beach, and buried above high water. Bones may subsequently be recovered by Maori and used for carving.

Operations such as Dolphin Explorer allow the general public to learn about Bryde’s whales, especially those in the Hauraki Gulf. Nicky became interested in whales as a child through watching Jacques Cousteau documentaries.

“It was only when I got to about 18 that I discovered you could study whales for a living,” she says. “I haven’t become sick of them yet. Almost anything I find out is likely to be interesting new information because these animals have been so little studied. I’ve identified 72 individual whales from dorsal fin marks, and I estimate that there could be about 200 in the gulf, which in turn are likely to be part of a considerably larger population.”

Hopefully, as more New Zealanders become aware of the large cetaceans that live year-round, and breed, on the doorstep of their biggest city, the sea will be managed for the benefit of both whales and people, thereby allowing future generations to enjoy the spectacle of these magnificent crea­tures in the waters they have occupied for eons.