There are a few reasons whales tail slap but the main reason is to warn off predation or over bearing males &/or females. It is a defensive action and depending upon the energy in the tail slap generally indicates what the communication is all about.
Today was an excellent example as from over 2 mile away we could see Mum & Calf tail slapping with high energy, as we approached there was further commotion and a continued surface action indicating that there was some source of predation in the area as the energy was very high, both Mum & Calf were agitated and there were no other whales or boats in the area.
After 15 minutes the energy slowed and Mother & calf moved in close to our vessel and just sat comfortably going back into a resting state, the calf was very inquisitive but you could see that Mum was overdue for a rest so late in the season to be expressing such energy.
On closer inspection we did sight a smallish fresh shark bite to the tail of the Mother and that was the evidence we were looking for to confirm the aggressive tail slapping we watched from further off in the tour.
There was a similar episode a few weeks back with a similar shark bite of a similar size and that Mother was also with calf but displayed with a tail lob and some breaching.
Tail slapping can be very gentle at times and we often watch when two whales might lightly touch the top of the water when in courtship and even toward vessel’s if they are deemed to be too close, all signs of energy we constantly interpret in understanding the Language of the Whales™.
Another form of tail sapping is when whales snake, which means moving their tail like a fish or snake (move side to side horizontally), this is often witnessed in competition pod’s when the males advances are being rejected by the female or when males are competing for the pole position next to the female, a very interesting side of these gentle giants.
If you do see whales tail slapping please understand it is a defensive move no matter what the circumstance are and as whale watchers we must respect this and be sure not to approach too close and always be aware we are to watch whale behaviour and not influence whale behaviour, as best as we can.
-Whale Watch Western Australia
This post was adapted from a blog, read the original here