Subject: Humpback mating behaviour

Bete Jones (bjones@cats.ucsc.edu)
Tue, 16 Nov 1999 08:38:35 -0800

Would you please comment on the following:
We live on the East Coast of South Africa, and have been keen humpback
watchers. We noticed tailsailing and could not get satisfactory answers to
our questions. A single humpback would tailsail for 6, 7, 5, 7 minutes at a
time, with about the same time breaks in between. Each time, we would
notice other whales in the distance, +- 2-3 km away. From their blows we
could determine that it was a mature whale and a calf, presumably
mother/calf pair.  Each time, the "mother/calf" pair would move towards the
tailsailer. At quite a close range (+- 300-500m) "he" would stop
tailsailing, move towards the mother/calf pair approaching him, and for a
while they would be together. The mother/calf pair would then return to the
way they first came, and the tailsailer would continue on his way, and
tailsail again.  A few days later, we would observe the same sequence of
events.
Could this tailsailing be part of their vocalisation, and specifically be
"mating-songs", being bounced off the ocean floor?  Each time we noticed
the tailsailing (which can continue for days) there were always whales
approaching from a distance, and as soon as the whales met (+- 1/2 hour to
an hour), the tailsailing stopped, and the whales went their own way.
The place where the tailsailing took place, is too deep for them to touch
the ocean floor; the tailsailer also seemed to be moved by a strong
easterly wind into a southwesterly direction, which did not prevent his
tailsailing. He would sail about 3 more times, and then go back to one of
the previous locations and start sailing again.  All this happened inside
the drop-off.  The tailsailer seems very aware of sound around him, as he
was approached by some jetski's at one point(+- 300 - 500m), and
immediately stopped sailing.
Our question is specifically whether this could possibly be a matter of
bouncing "mating-songs" off the oceanfloor, in order to attract females to
him for mating.
(We are home-schoolers and have been studying cetaceans - been on a
southern right whale watch, and daily watched the humpbacks from our
verandah!)
Thanking you
Storm Family, East London, South Africa
storma@iafrica.com

Dear Dr. Storm,

I am not familiar with this tailsailing behavior, the only mating behavior
I have seen is in Hawaii.  Humpback males usually sing suspended at 20-30
meters depth.  Their song lasts, on average, from 12-20 minutes at which
time the whale comes up for air.  This pattern can continue for hours.  The
sounds the whales make are not directed at the ocean floor so they will
bounce up and travel - the sound usually spreads out omnidirectionally and
can travel long distances via the deep sound channel.  The singing males
are often approached by mother/calf pairs.  At this time they will stop
singing, travel together with the mom/calf pair and then either return to
singing after a while or the female will "choose" the male for a mate.

I hope this has shed a little light on your question.

Best,
Bete Jones