Dolphins and bubbles

Chinese version

Playing with bubbles is an important part of dolphins' life. It is well known that dolphins enjoy riding waves (e.g. those generated by boats) and jumping between the two bow waves of a moving catamaran.

Bottlenose Dolphin surfs the wake of a research boat on the Banana River near the Kennedy Space Center.From Wikimedia Commons.

Dolphins can also create and manipulate bubbles and show a complex behavior during their play with bubbles. The bubbles generated by dolphins  mainly include: bubble stream, bubble burst, bubble cloud, single bubble trail, (sing or double) bubble ring (McCowan et al., 2000). Dolphins can play interactively with those bubble through biting bubbles, swimming through the bubble rings and manipulating the bubble ring using their rostrum (e.g. turning the ring in a vertical fashion). More sophisticated behaviors has been observed during dolphin's play with bubbles, e.g. generation of a second bubble ring which joins the first bubble ring to form a larger bubble ring; generation of the third bubble ring passing through the second ring to catch and join the first ring.

Bubble ring generated by a dolphin. Source

Bubble ring made by a dolphin in the aquarium. From YouTube.

Bubble stream generated by a dolphin. From YouTube.

A burst of bubbles from dolphin blow hole. Source.

Both wild and captive dolphins can blow bubble rings. Sometimes, the size of the bubble ring can be large enough for dolphin to swim through. More interestingly, blowing bubble rings takes practice i.e. those dolphins who can not blow bubble rings can learn it after watching others and taking experiments (Walke, 2008, p.30; video). How smart dolphins are! It has been reported by BBC that two beached whales in New Zealand were rescued by a bottlenose dolphin. 

A dolphin passing through the bubble ring. Source.

Although dolphins are talented swimmers, it has been observed that the swim speed of dolphin is below 54 kilometers per hour near the surface. According to a recent study by Iosilevskii and Weihs (2008) (also reported by New Scientist), it is cavitation which limits the speed of the dolphin. Based on a series of calculations, they found that cavitation bubbles could be formed near the tail of dolphin due to the movement of the fins. When the generated bubbles collapse, they will cause damage to the dolphins. Cavitation happens when the speeds of dolphins reach 36 to 54 kilometers per hour near a few meters of the water surface. Different with bony tail of tuna without nerve endings, dolphin can feel the pain if they swim too fast. 

References

Iosilevskii, G. and Weihs, D. (2008). Speed limits on swimming of fishes and cetaceans, J. R. Soc. Interface, 5, 329-338. doi: 10.1098/rsif.2007.1073

McCowan et al. (2000). Bubble Ring Play of Bottlenose Dolphins (Tursiops  truncatus): Implications for Cognition, Journal of Comparative Psychology, 2000, Vol. l14, No.1, pp.98-106.pdf

Walke, S.M. (2008). Dolphins, Lerner Publishing Group.