Broome's Humpback Whales
WESTERN AUSTRALIA’S GROUP IV POPULATION OF HUMPBACK WHALES
Western Australia’s Kimberley is a world class whale watching region and home to the world’s largest population of Humpback whales. Every year the whales make an epic migration from their feeding grounds in the Antarctic to spend the winter months from June to October in the Kimberley’s warm, tropical waters, between Broome and Kuri Bay.
Join us on a memorable half-day Whale-watching and Wildlife Cruise to witness these magnificent cetaceans in their natural environment, as they sing and perform acrobatic feats in the waters off Broome’s iconic Cable Beach, and the waters of the lower Dampier Peninsula.
The whales have staged a magnificent recovery since the closure of the last Australian whaling station in the late 1970s, with the total population now estimated at somewhere between 28,000 and 42,000 individuals. Kimberley Whale Watching, based in Broome, has been studying the distribution and behaviour of these magnificent Kimberley Whales since 2006, building a database of whale distribution and a film and photographic library of whales, whale behaviour, distribution and tail fluke photos for identification purposes.
Humpback whale information
Order: Cetacea (whales, dolphins and porpoises)
Sub-order: Mysticeti (baleen whales)
Family: Balaenopteridae (rorquals)
Humpback whales are the fifth largest of the baleen whales, giving birth to live young. The whales display sexual dimorphism, with males slightly shorter than females at sexual maturity. Males measure an average of 12.2-14.6 m with females slightly longer at 13.7-15.2 m, although whales of up to 26m have been recorded. Humpbacks have an indistinct dorsal ridge extending from the rostrum (snout). The rostrum, upper and lower jaws and lips, are covered in tubercules (lumps), each containing a single hair, or vibrissa, which may aid in navigation by detecting changes in water temperature and current.
Extending from the lower jaw to the umbilicus are 20-35 ventral pleates, or grooves, which enable the whales to expand their jaws when feeding. From the upper jaw hang 270 and 400 pendulous keratin baleen plates, which the whales use to sieve small crustaceans and bait fish from great mouthfuls of water.
The whales’ pectoral fins are approximately one third the length of their bodies, with 10 phalangic knobs along the outer surface, which correspond with the phalanges and joints. These long pectoral fins allow for both great manoueverability, tactile interaction.
The dorsal, or upper sides of the whales is generally dark in colour, with mottling extending to the pectoral fins, underside and tail flukes. Calves are pale grey when born and then darken with maturity. In front of the carina, the protruberance near the caudal peduncal (the narrowing of the tail) is the anal slit followed by the genital opening and mammary slits in females, which are located on either side of the genital opening. Females are identified by a ‘hemispheric lobe’. In males, the distance between the genital opening and the anus is almost 2.5 times longer than is seen in females, with the genital opening in males more anterior than the female.
Humpback whale gestation takes eleven months. Calves are born at a length of four to five metres and a weight of two tonnes. After birth, the mother will provide nearly 240 litres of milk per day for the calf, feeding the calf for nearly a year. The milk is extremely rich at approximately 40-50% milk fat and the consistency of chewing gum. Humpback whale cows have two mammary slits, and feed on demand by exerting muscular pressure.
By the time the calves are weaned at 11 months, they will have doubled their length to about nine metres. For the first few weeks the cow and calf are rarely more than a few metres apart. The calves are suckled for a further eleven months, during which time they have nearly doubled in length to nine metres. Cow calf pairs keep mainly to themselves, with the exception sometimes of a primary escort, thought to be a male.
Sound is of tremendous importance in humpback communication, and they are thought to produce approximately 640 different vocalizations. Male humpbacks “sing” complex songs comprised of verses and sets, but females and calves also communicate by sound.
“There’s a lot of very close tactile relationship goes on between a cow and a calf” says Micheline Jenner, from the Centre For Whale Research. ” That’s the strongest bond in humpback society. It’s very interesting to watch they are quite beautiful. They swim very closely together, the cow will remain horizontal at the surface resting and the calf will often lie perpendicular to her, under her chin, underneath the water. Or actually, sometimes we’ve seen a calf actually caught under the flipper of an adult humpback whale. That looks really funny when you see a calf sort of stuck under there and the female will just remain still and the calf will then sort of scoot out from underneath the flipper and then pop to the surface like a cork, take a breath and then dive down again. And then they position themselves right across the underside of the belly. At other times you can see a calf lying on the head of the female and you can see the females, the cows are really quite patient and I guess that’s how mums are”.
The east and west coast populations of Humpbacks occupy discreet feeding areas in the Antarctic, with little overlap. Western Australia’s Breeding Group D, or Group lV population of Humpback whales makes one of the longest migrations in the animal kingdom, a journey of nearly 13,000km return, from Antarctic area lV, between 70° and 110° E.
According to current literature, it is thought that cows calve every two or three years. The cows and primary escorts rest at several points along the coast, including Rottnest Island, Exmouth and Pender Bay, finally arriving in the Kimberley around the middle of June.
Mating and birth for Humpback Whales occurs in tropical waters, somewhere between June and November, when water temperatures are at least 25 degrees celsius. Calving is thought to take place at night, but it is an event that is very rarely witnessed.
For the first few weeks the cow and calf are rarely more than a few metres apart. The calves are suckled for a further eleven months, during which time they have nearly doubled in length to nine metres. Cow calf pairs keep mainly to themselves, with the exception sometimes of a primary escort, thought to be a male.
After calving in the pristine Kimberley waters, the cows spend several months with their calves, before making the return journey to the Antarctic waters. Some cow calf pairs remain in the calving grounds until the end of November.
Very little research has been done in the Kimberley to date. Currently research is being carried out by ourselves, Kurt and Micheline Jenner, Chris Burton, Andrew Bowles from Two Moons (Goojar Goonyal), and Doug Coghran (DEC).
In common with other rorquals (baleen whales with throat grooves), Humpback whales exhibit a range of behaviours, including tail slapping, spyhopping, porpoising, breaching and pectoral slapping.The exact meaning of this behaviour is still not fully understood, but behaviour such as breaching may involve demonstrations to other whales to indicate territory or dominance. Behaviour such as lobtailing may be used to school fish into tighter shoals for feeding. Whales also appear to have a good sense of play.
Swimming near the surface with blowhole exposed.
In the turbid waters of the Kimberley, humpback whales rely on sound to navigate and communicate. Humpback whales make over 640 different “social sounds”. Male humpbacks sing complex songs, divided into phrases, sub-phrases and themes. Songs may last up to half an hour and may be repeated over hours and days. The sounds vary in frequency from 20Hz to upwards of 24 kHz. The typical range of human hearing is from 20Hz to 20kHz. The sounds vary by amplitude (loudness) or frequency (the pitch goes up and down).
The songs are only sung in the calving grounds. All males sing a similar song for the duration of a calving season, and songs are unique to individual breeding stocks, thus the west coast song is different to the east coast song. Every year there are subtle differences in the songs, and the song may evolve over the course of a season.
Humpback whales have a larynx but lack vocal chords; it is thought that they circulate air around bony structures such as cranial sinuses to produce sound.
Click on the sidebar to listen to whale song from Broome, and Camden Sound on the Kimberley coast.
Over the past six years, Kimberley Whale Watching has recorded tail fluke imges of Kimberley Humpback whales to add to a MICSPix database designed by Wheelock College in Boston, Mass. These photographs allow researchers to monitor the movement, health and behaviour of individual humpbacks as they migrate up and down the Western Australian coast.
As Humpbacks dive they raise their tail flukes above the ocean surface,enabling us to photograph the markings on the underside, or ventral surface, to add to the database. The first North Atlantic Humpback whale tail fluke catalogue was published in 1976 by Allied Whale. Individual humpbacks are identified by the patterns of black and white pigmentation and scars on the underside of the flukes of their tails, and by the patterns on the tail’s trailing edge, the distinctive S-shaped scalloped part on the outside of the flukes, which has pointed tips and a deep median notch in the centre. Tail flukes can be up to 5.5 m wide.