For some years, when the austral winter begins in the Reunion island, everyone tries to observe the first humpback whales of the season. The first individuals arrive in June or July, then pregnant mothers appear with singles looking for partners. All have traveled between 5,000 and 7,000 km, from the feeding areas of Antarctica to the tropical waters of the Indian Ocean.
In these warm waters the humpback whales give birth to their calves and breed ... as scientists say. The whales sail around Reunion island, Madagascar, Mayotte before returning to the South to feed. They usually leave the warm waters between late September and mid-October.
How to recognize a humpback whale?
- Humpback whale (calf) in Reunion Island
- The humpback whale is considered an adult when it reaches the size of 10-11 meters at about 4-5 years old; it is then sexually mature. - © M. Dupuis
TENDUA’s volunteers accompany the sea excursions organized by the diving club the DODO PALME to encounter these graceful giants. The humpback whale (Megaptera novaenglea) is one of the most recognizable cetaceans thanks to three characteristics:
- Pectoral fins reaching 1/3 of the length of its body, i.e. about 5m for 15m. Females are slightly larger than males and can measure between 16 to 19 meters long (from 14 to 16m for a male) ;
- The head and lower jaw are covered with rounded protuberances called tubercles, which are hair follicles, characteristic of the species. These “knobs” come from the vibrissae of his ancestor called Pakicetus some 50 million years ago. Up to now, it seems that each knob includes a single hair. These follicles would be sensors indicating the quality of water such as temperature, salinity, deep.
- Finally, humpback whales are famous for their spectacular breaching that you are never tired of admiring.
- Humpback whale jumping out of water in Reunion Island
- To get his body out of the water - about 30 tons - the humpback whale must reach a speed of 15 NM! - © M. Dupuis
Described as “playful and joyful” by Herman Melville in 1851 the most acrobatic whale performs amazing breaching out of the water. To propel its thirty tons out the water, the humpback whale must reach the surface at a speed of 15 NM! It thus manages to make tendrils above the water, but these are not the only breaches it can do.
It is not known exactly why they breach. In fact, it is such a good question that scientists themselves are still trying to answer it.
There are a number of different hypotheses.
Nevertheless, people mostly agree that this spectacular behavior occupies an essential place in their communication system. Breaching may be a way to communicate (“Here I am! Over here!”), by generating a large splash and a loud noise.
Is this marking territory? a call? a complex game? or simply a show of strength?
Behaviors include breaching, spy-hopping, lob-tailing, tail-slapping, fin-slapping, peduncle throws, charging and parrying. This has led to speculation amongst scientists that lobtailing is, like breaching, a form of non-vocal communication. A breach or a lunge is a leap out of the water also known as cresting. The distinction between the two is fairly arbitrary: cetacean researcher Hal Whitehead chooses to define a breach as any leap in which at least 40% of the animal’s body clears the water, and a lunge as a leap with less than 40% clearance.
The humpback whale can also hit the surface with its two pectoral fins (the whale is on its back) or only with one pectoral fin : Australian scientists consider that a female that hits the surface such a way is “inviting” males to come closer....But when a whale hits the surface with its tail (it is then on the belly), in a such called “tail-slapping”, it is a sign of nervousness and agressivity: do not forget that the caudal fin (tail) is about 4 m wingspan, it makes a huge noise and better not to be around...
Spy-hopping is when the humpback whale puts only the head out of water, much like a periscope; its vision is both earthly and submarine. Is it to see or rather to hear what it does not see under water, like the specific sounds of the near shore? We observed a young whale calf poking out its head several times (“spy-hopping”), just before his mother did a full twist out of the water a twenty meters from him: teaching by observation?
Also, on several occasions a “spyhopping” whale calf was observed, just before it repeated per series of 10 the same “gesture” that his mother had shown him once or twice ...
When spy-hopping, the whale rises and holds a vertical position partially out of the water, often exposing its entire rostrum and head. Spy-hopping is controlled and slow, and can last for minutes at a time if the whale is sufficiently inquisitive about whatever it is viewing. Generally, the whale does not appear to swim by fluke propulsion to maintain its “elevated” position while spyhopping, instead relying on exceptional buoyancy control and positioning with pectoral fins. Typically the whale’s eyes will be slightly above or below the surface of the water, enabling it to see whatever is nearby on the surface.
Spy-hopping often occurs during a situation, where the focus of a whale’s attention is on a boat, such as whale-watching tours, which they sometimes approach and interact. Often spyhopping might not be used for looking but instead for hearing, for exemple in order to hear better when they are near the line where waves begin to break in the ocean as this marks out their migration route. It can therefore be said that spy-hopping behaviour is used for many different reasons across a wide range of species.
Lobtailing and slapping
Lobtailing is the act of a whale lifting its fluke out of the water and then bringing them down onto the surface of the water hard and fast in order to make a loud slap. Whales tend to lobtail by positioning themselves vertically downwards into the water and then slapping the surface by bending the tail stock. They are likely to slap several times in a single session. Lobtaling often occurs in conjunction with other aerial behaviour such as breaching. They may also slap their fin against the water for a similar effect, known as pectoral or fin slapping.
The sound of a lobtail can be heard underwater several hundred metres from the site of a slap. This has led to speculation amongst scientists that lobtailing is, like breaching, a form of non-vocal communication. Thus the lobtail is probably important visually as well as acoustically, and may be a sign of aggression.
One hypothesis of breaching is that whales are trying to shake parasites off of their skin. Another popular theory says that they might breach simply to scratch an itch. The impact of the animal hitting the water may have the same effect for the whale as a dog rubbing itself against a tree to try to scratch fleas off of its back. It is thought that breaching helps remove barnacles and lice from their skin. A whale when arriving from the Pole can have up to 500kg of parasites!
Acrobatics is not the only art that masters the humpback whale; it is also distinguished for its songs.
The male is a Distinguished singer : it composes an annual real “tube” that it performs together with other males. It sings head down, motionless at 10-20 meters deep, or it moves slowly at 2-3 km/hour. This position seems to allow it to save energy for passing the air from his lungs to his laryngeal bag near his vocal cords in melodious back and forth, and without any bubbles. Without stopping to sing, the whale goes breathing on surface every 10 to 20 minutes and comes back quietly to its position.
These compositions, among the most complex in the animal kingdom, seem to obey a score that does not leave room for improvisation. Discovered in the late 50s by the US Navy sonars, these “songs” were decrypted by Payne and McVay in 1971. The humpback whales are the only ones to have such a repertoire!
The song is composed of sounds with very different resonances: acute squeals, more serious trumpet tunes, squeaks, whistles, clicks, screaming, humming, roaring, bellowing ... All these sounds are quite strange ! they constitute basic elements of the song : they are organized into sequences to form sentences that last a few seconds. The repetition of phrases (ten times) composed a theme. The theme is in turn repeated several times before the whale performs other sounds that will produce new phrases and new themes. A song is composed of about 6 themes that are repeated in the same order every time. At the end of the sixth theme, the whale takes its melody at the beginning of the first theme.
These “songs” cover tens or hundreds or thousands of kilometers; they are produced by air movement within the respiratory tract of the animal, without no need for the latter to exhale: there is therefore no bubbles, making the phenomenon almost “supernatural”.
Why do they sing?
That’s a good question! Because we can’t ask them, so we’ll never really know. Scientists have many hypotheses (or guesses?) as to why whales sing.
- Their songs could play a major role in guiding animals during the migration through the ocean ;
- Another hypothesis is that of the «lek mating system». A lek is an aggregation of males that gather to engage in competitive displays, in order to entice visiting females who are surveying prospective partners for copulation. Leks are commonly formed before or during the breeding season. By singing, whales males take on some territories that are in visual and auditory range of their congeners. To occupy maximum of space and multiply opportunities to mate with a female, they stay away from each other, separated with some kilimetres, rather like a beacon to allow reproductors to locate themselves on a territory of several thousand kilometres.
The similarity of their song shows quite clearly that they are not seeking to distinguish themselves from each other, the selection will be later during the clashes;
- The songs would be the expression of a secondary sexual characteristic under hormonal control, capable of stimulating ovulation in females. Thus, humpback whales males that escort a lactating female would sing, perhaps, to excite and stimulate ovulation, which is considered possible soon after birth. It is also possible that the lament of solitary males also have the same vocation melody;
- The Whale songs are assumed to have an important role in mate selection; however, they may also be used between males to establish dominance.
And what about females?
- Humpback whale (calf) in Reunion Island
- Ventral grooves run from the lower jaw to the umbilicus about halfway along the underside of the whale. These grooves are less numerous (usually 14–22) than in other rorquals but are fairly wide. The humpback’s pectoral fins are proportionally the longest fins of any cetacean. - © M. Dupuis
Whales females do not either remain silent!
We know that in addition to all the attentive and impregnated gestures with tenderness that can be observed, mother whale also communicates vocally with her calf : her vocals are more acute and much shorter than the males’ singing, there are more like short and clear signals ! ...
And the calf vocalises to in response but is it really rehearsing ... or answering to his mother?
The humpback whale is a rather good-natured: it tolerates quite well our human curiosity, provided of course that we respect the current Approach Chart instructions in the Reunion island, to respect the animals and in no case to prosecute or harass them!
Sometimes, the Indo-Pacific dolphins swim around whales.
Humpback whales are also known to appear in mixed groups with other species, such as the blue whale, fin whale, minke whale, gray whale, and sperm whale.
Humpback whales also know how to stay immobile. Some individuals were observed remaining immobile on the surface for more than 45 minutes, but also vertically, upside down and the caudal fin to the outside, for 15 min. The latter attitude was seen particularly among breastfeeding animals. It can be also thermo-regulating, the tail being irrigated by many blood vessels, it would lower the overall temperature of the body, or why not? a rest position, but that is not innate: we saw whales calves training but to no avail!
Their apnea last up to 30 minutes. We observed that when they are navigating, they breath every 6-8 minutes. The humpback whales breathe voluntarily.
Probably like dolphins, for each sleep phase, the two cerebral hemispheres take turns, one at rest while the other remains active. While sleeping, the whale can navigate; it then rises to the surface to breathe then plunges just as slowly. A whale can repeat about 6 times in one day these rest cycles. Each cycle lasts about 20 to 30 minutes. Scientific observations indicate that a “relaxed” whale rests with its swinging arms (= pectoral fins downwards) and the caudal fin inclined downwards. Be relax...
Just over forty years after its creation in 1946, and after noting the near extermination (90%) populations of humpback whales, the International Whaling Commission established in 1986 a moratorium to stop commercial whaling, which 3 countries have still not signed and continue to hunt whales: Japan, Iceland and Norway.
This moratorium does not mean a total cessation of whaling, despite the loss recorded of over 200 000 humpback whales only in the Northern hemisphere. Phillip Clapham, a leading global specialist, estimated from 90 000 to 100 000 the number of humpback whales that lived In the Southern hemisphere, before the industrial fishing years. In the 80s, they remained just over 5000 ...
A moratorium’s clause provides that “the Commission would draw up a” comprehensive stocktaking “of the effects of this decision on whale stocks and consider modification of this provision and the establishment of new catch quotas.”
The Scientific Committee of the IWC now identifies populations of various cetaceans, includingthe humpback whales of the northern and southern hemispheres.
Although populations of humpback whales are doing better now, they are still facing many threats: hunting, of course, but also the underwater gas and oil and the mining exploration activities, construction and urbanization of coastlines and side effects of industrial fishing, and the global warming that rarefy their food.
Our ignorance remains high...
Do not forget all the questions still unanswered.
Because they live in an open environment, in a vast maritime domain, mostly underwater, humpback whales are difficult to observe and remain poorly understood. The researchers therefore emit more hypotheses than certainties. There are many questions, and every answer brings on new questions!
To date, for example, no one has been able to explain how whales learn to sing: by imitation? By cultural transmission of “musical notes”? How and why they are changing their songs?
Males sing only under two different circumstances: when they are alone, and when they accompany a lactating female. The songs are the same, but do they have the same goal?
Can all the males sing? Is it a privilege reserved for an elected member with a particular mission within the group? Is there a specific geographic areas to sing, as might suggest some observations? What triggers the start of a song? And its end? ...
Beyond the song, do the humpback whales use a “vocabulary” ? Is it common to all the humpback whales or is it “regional” ? A “sound library” emitted by the humpback whales of the Indian Ocean is under creation ...
Watching and swimming with humpback whales is an extraordinary opportunity.
They are exceptional ambassadors of the underwater world, then, please, let’s learn to respect their environment, our oceans, our seas, our rivers, our mountains, our countryside and cities by our daily actions! Thank you for them ... and for all of us!