Humpback Whale
(Megaptera novaeangliae)
Humpback whale B405 "Barbillon" breaching
Family: Balaenopteridae
Species: Megaptera novaeangliae (Borowski, 1781)
Length: 12 to 13 meters on average. Can grow up to 16 meters for the females.
Weight: 25 to 30 metric tons.
Life expectancy: Up to 80 years.
Description:
The humpback whale belongs to the family of rorqual whales (Balaenopteridae) in the suborder of baleen whales (Mysticeti) and the sole member of the genus Megaptera. Its main characteristic feature are the enormous pectoral fins (flippers), which can reach one third of the total body length. In fact, that is where the humpback whale gets its Latin name, Megaptera, meaning ‘long-winged’. As in all rorqual whales, females are slightly large than males, a rare exception in mammals. Furthermore, as all other whale species living in both hemispheres, the inhabitants of the southern oceans are larger (Lockyer, 1984).
The humpback whale is moderately large balaenopterid species, with an average size of 13-14 m (Chittleborough 1965). Adult male humpback whales weigh on average 27 metric tons while female mass varies greatly with their reproductive state and ranges between 24.8 and 40.8 tons (Lockyer 1976). Calves are born after a gestation period of 11-12 months and weaned following another 10-12 months (Chittleborough 1958). A two-year calving cycle is possible, and cases of annual reproduction has been observed. However, the average calving interval is around 3 years and varies between populations. Females can start having calves at 5 years of age, but are usually older at the time of their first recorded calf. They reach sexual maturity before the reach physical maturity.
The rostrum of a humpback whale poking out of the water
Humpback whales have a worldwide oceanic distribution and spend the summer on productive high latitude feeding grounds (Chittleborough 1965, Dawbin 1966, 1997) while in the winter they congregate in sub-tropical to tropical waters to breed and mate (Dawbin 1966, Whitehead & Moore 1982). In the summer months they feed on a wide variety of prey, mainly small schooling fish [e.g. herring, Clupea spp. (Watkins & Schevill 1979), capelin, Mallotus villosus (Whitehead et al. 1980), sandlance, Ammodytes spp. (Payne et al. 1986, Payne et al. 1990)] and several species of euphausiids (krill). Humpback whales feed almost exclusively in the productive feeding areas and live off their fat reserves the rest of the year, as most baleen whales do (Lockyer 1984). Observations of feeding in the low latitude breeding areas are rare (Baraff et al. 1991, Gendron & Urbán R. 1993). The migration is staggered by sexual, maturational and maternal classes (Nishiwaki 1959, Dawbin 1966, 1997). In the fall, lactating females leave the feeding grounds first, followed by immature animals, mature males, resting (neither pregnant nor lactating) females and last, by pregnant
females. In late winter the order is almost reversed, with newly pregnant females leading the migration to the feeding grounds. Females with calves are the last to leave the breeding grounds. During the time of maternal care the calf follows its mother to her feeding ground. Thus, site fidelity to these feeding ranges is maternally directed (Baker et al. 1986, Clapham & Mayo 1987, 1990). Mothers wean their calves in the fall of their first year, on the feeding grounds or during the migration to the breeding grounds (Baraff & Weinrich 1993). The general view that the vast majority of whales undertakes the annual migration has been changed recently, and there is evidence that some over-wintering occurs in high or mid-latitudes, especially of juvenile individuals (Swingle et al. 1993, Barco et al. 2002, Robbins 2007).
Social structure and behaviour
The annual life cycle of the humpback whale shows a distinct seasonality, which is reflected by the difference in behaviour in summer and winter (Baker & Herman1984a). Humpback whales display a polygynous mating system (Baker & Herman 1984b, Cerchio et al. 2005). On the breeding grounds male humpback whales compete for females by singing (Tyack 1981), escorting oestrous females and fighting intensively with one or several males for access to presumably oestrous females (Tyack & Whitehead 1983, Baker & Herman 1984b). Clapham et al. (1992) observed repulsive behaviour of some females towards males and interpreted this as female choice. Mother-calf pairs present the only persistent social affiliations (Clapham 1993, Clapham & Mead 1999). Otherwise, brief associations between small groups are prevailing (Mobley & Herman 1985, Mattila et al. 1994). Single males are often engaged in singing (Tyack 1981). Mother-calf pairs are frequently observed with a third animal (called escort), which is usually a male (Clapham et al. 1992). Most encountered larger groups persist of one female and several males (Tyack & Whitehead 1983, Baker & Herman 1984b, Clapham et al. 1992). The single female in such competitive groups is called nuclear animals, while the closest associate is called principal escort (Tyack & Whitehead 1983), which tries to defend its position against secondary escorts or challengers (Tyack & Whitehead 1983, Clapham et al. 1992). Interactions between males are often violent, resulting frequently in superficial wounds (Tyack & Whitehead 1983, Baker & Herman 1984b), although one death was reported (Pack et al. 1998). While males are encountered in competitive behaviour, interactions between females are almost absent. Competitive groups include only one female (Clapham et al. 1992), female pairs are basically unobserved (Clapham, 2000) and lactating females appear to avoid each other (Baker & Herman
1984b, Mobley & Herman 1985). Limited information is available for social
affiliations during migration, but it seems to resemble more the social organization on the breeding grounds (Brown & Corkeron 1995).
Group of humpback whales diving simultaneously
On the feeding grounds, humpback whales form small and unstable groups, typical to fission-fusion societies (Whitehead 1983, Clapham 2000). Lactating females avoid each other (Clapham & Mayo 1987) as on the breeding grounds (Baker & Herman 1984b, Mobley & Herman 1985), but can sometimes be escorted by adult females, and more often by adult males (Sardi et al. 2005). In contrast to the winter months, males are not found in groups, they are rarely found together (Weinrich & Kuhlberg 1991, Clapham 1993). Females are more social (Weinrich & Kuhlberg 1991) and are found in groups with other females and males during feeding and other activities (visible at the surface) (Weinrich & Kuhlberg 1991, Clapham 1993). In general, the behaviour on the feeding grounds has been inferred as not competitive and sometimes cooperative, e.g. during feeding (Whitehead 1983, Baker & Herman 1984a, Weinrich 1991, Weinrich & Kuhlberg 1991, Clapham 1993).
Humpback whales in the North Atlantic and the Gulf of St. Lawrence
In general, we three global humpback whale populations: the northern Atlantic, Pacific, and the southern hemisphere. Theoretically no exchange occurs between those groups, although some exceptions exist. In the North Atlantic, we distinguish six so-called summer feeding aggregations: the Gulf of Maine, the Gulf of St. Lawrence, Labrador and Newfoundland, West Greenland, Iceland and the Barents Sea (Katona & Beard 1990, Palsbøll et al. 1997, Smith et al. 1999). While all animals from the first four regions breed in and around the Caribbean, only half of the animals from Iceland migrate there, as do 10% of whales from the Barents Sea (Stevick et al. 2003). The others migrate to a second breeding round, which is yet unknown, surprisingly. The Cap Verde Islands could be this second breeding ground, but while some humpback whales have been observed there in winter, the vast majority of animals from the eastern North Atlantic have not been seen there (Palsbøll et al. 2001).
Aerial photographs of humpback whales taken by drone (SMRU)
The St. Lawrence
Humpback whales have been observed in the St. Lawrence for centuries. They were hunted in the St. Lawrence since the beginning of the 19th century (Mitchell & Reeves 1983) and were taken along the Gaspe Peninsula, the Quebec North Shore (north of Anticosti Island) and in the Strait of Belle Isle. Mitchell and Reeves (1983) estimated a minimum catch of approx. 200 animals in the St. Lawrence (1858-1888), after whalers had already operated in the area for a considerable time. Up to 3,000 animals were caught in eastern Canadian waters (Reeves & Smith 2002).
MICS started to study whales in the St. Lawrence in 1979, and the first two humpback whales were identified in 1980 (“Splish” and “Splash”). While there were already numerous humpback whales migrating through the Strait of Belle Isle towards Labrador early summer, the number of annual encountered humpback whales in the main Gulf remained very low in the single digits until the end of the 1980s. We then slowly witnessed an increase in numbers, which could be also due to our increasing effort in time and space, thanks to larger boats. The first cow and calf pair (“Fleuret” with her mother “Pseudo”) was observed in 1982. Both are still alive in 2018. Pseudo had a calf in 2016 bringing her reproductive life span to at least 34 years.
The number of humpback whale observations increased in late 2000s, with now over 100 different individuals regularly observed each year. They usually are first sighted off the Gaspe Peninsula in June, but the earliest confirmed sighting is May 3rd. However, there have been observations in almost all months from different regions, depending on the ice coverage. It is highly likely that these were juveniles, who do not yet undergo the full migration cycle of adults. June is the best month to see humpback whales off Gaspe, then the bulk of the animals usually moves north into our main research area - the Mingan-Anticosti area. In fact, it is our main research area because the overwhelming majority of the whales in the St. Lawrence is found here. The animals can be found along the North Shore between Moisie and Havre-St-Pierre, and beyond. In some years they spent the entire summer and early fall with us before leaving the Gulf. In some years, they revisit Gaspe before leaving the St. Lawrence, but it is not a consistent pattern. We lack regular observations in October & November, due to the weather conditions becoming a major constraint in the fall.
MICS researchers and participants to the Whale Research Expeditions observing a humpback whale about to dive
We receive observations from the Estuary, but rarely more than five individuals are sighted there per year. Some more animals prefer to stay in the waters off Gaspe for the season. Often, we observe calves in the Mingan area, that then remain on the periphery during their juvenile years. This include BBR (also known as Gaspar in the estuary), Blizzard, and Aramis. These animals returned to Mingan once they reached a certain age and size. One hypothesis is that they return to the prime feeding areas, when they are large enough to compete with their conspecifics (individuals of they same species).
Over the last 40 years, we observed that both humpback whales and fin whales start to arrive in the St. Lawrence earlier and earlier. They now arrive one month earlier than they did when we began our study (Ramp et al 2015). This could be linked this with the warming temperature of the St. Lawrence. Less and less ice is formed and the peak of the plankton bloom (and resulting therefore food chain) happens earlier. While adaptation to a changing climate has forced other species to change their migrating timing, no other species has changed so fast.
This observation is one of the many results of our long-term photo-ID studies, which are predominantly used for monitoring population parameters. For example, the number of calves has dropped considerably since 2010. While we usually observed between 10-20 calves per year, we are now down to 3 or 4, the calving interval increased from XX to YY. The same females come back, just without a calf. One current hypothesis is that the animals are not in good enough physical condition to sustain pregnancy and have offspring.
Humpback whale H509 "TicTacToe" and her calf in 2017
In general, the females in St. Lawrence seem to become reproductive active later than in other areas. No known female has started to have calves at before 10 years of age. Additionally, the calving rate has increased, meaning there is more time between two subsequent calves (Ramp 2008). The sex ratio is also different from other regions. While it is assumed that in the overall population the sex ratio is 1:1, we seem to observe more females than males on an annual basis, were we see twice as many females as males.
Males and females have been observed to form bonds lasting an entire season, but females seem to have “best female friend” (Ramp et al 2010). Adult females have been seen to hang out together for 3.5 years on average, and up to 6 years in the case of Tracks and Splish. They usually are separated when they care for a calf.
Humpback whales are globally recovering from the whaling era, and are arguably one of the less endangered baleen whales species. They still face numerous threats, however. In addition to the changing environment due to global warming, overfishing, acoustic noise pollution and toxic contaminations; the main direct threats are ship strikes and entanglement in fishing gear. Almost every single animal bears the scars of a previous entanglement, and while a lot of cases go unnoticed, studies in the Gulf of Maine reveal that almost 3% of the population could die every year in fishing gear (Robbins 2009). Although the numbers seem to be increasing across the globe, and the down-listing of humpback whales as endangered species by NOAA in 2016 is a success story and the proof that conservation works; we have to continue to monitor the population. While at the moment no single hazard seems to threaten the population (while they can of course affect individual whales), the accumulation of all these effects could have a negative long-term impact on the overall population health. But at least, with the last 40 years of work on humpback whales, humans have given the species a chance for the future.
