Humpback whales have changed their behaviour when looking for a mate with which to start a family. Back in the day when the humpback whale had been decimated to less than 500 in the 1960s off the east coast of Australia, they were far more dispersed and therefore they had to vocalise their presence over long distances in order to find a mate. But today, there is an estimated 30,000 humpback whales in this region.
They don’t have the need any more to communicate their presence in the same way. They have a different need which is to see off competition. And therefore, their behaviour has shifted from singing to fighting with other males. This is the result of a new study.
Earlier studies found that whales temporarily stopped singing when there was noise from shipping nearby. And they also found that the purpose of singing may have been to order socially the male whales. It appears to have been a way of establishing dominance.
Of course, fighting also establishes dominance but in a different way. The change in behaviour is due to very successful conservation efforts.
The Times reports that there has been an eightfold increase of humpback whales in the South Pacific. The difficulty, as mentioned, is no longer announcing one’s presence to females in order to find one but to stop rival males from claiming the female of choice.
The study was conducted by scientists from the University of Queensland. They visually tracked humpback whales from the coastline with acoustic monitoring to see how male whales approached females between 1997 and 2015.
Rebecca Dunlop, a co-author of the study said:
“We found that a large proportion of male whales sang in earlier years”.
The Conversation reports that in 1997 males were twice as likely to sing to attract a female. However, by 2014-2015 non-singing males were five times more likely to be seen joining a group with a female.
They also report that in 2003-2004 2 in 10 male humpback whales employed singing but in 2014-2015 only 1 in 10 did so. And in the earlier years they also found that males were less likely to sing when there was a higher proportion of male competition in their social circle.
The logic of this change in behaviour is very apparent. With such a large increase in population a different strategy had to be employed in order to successfully compete with other males to find a mate. This came down to fighting rather than singing.
The study is published in Communications Biology. It appears that the default behaviour is to fight but because the population numbers were reduced so dramatically the whales learned to sing. This appears to have been a non-standard behaviour. Fighting is more of a standard behaviour.
On the basis that that is true, it appears that humpback whales off the east coast of Australia now behave normally when looking for a partner.
- I have added one or two of my own observations.
- The study: Dunlop, R., Frere, C. Post-whaling shift in mating tactics in male humpback whales. Commun Biol 6, 162 (2023). https://doi.org/10.1038/s42003-023-04509-7
Below are some more articles on whales.