Greenland Sharks – Slow and Sluggish Wins the Prey
Sharks are my favourite marine creatures and I am glad to be sharing about the following species of shark here.
The mysterious Greenland shark, Somniosus microcephalus, live in extremely cold waters. It is native to the waters of the Arctic and the North Atlantic, and occasionally found in Canadian rivers. Like most fishes, Greenland sharks are cold-blooded, meaning their body temperature vary with the surroundings. Thus, living in cold waters would lower their body temperature, slow down muscle movements and consequently, reduce swim speed. Unsurprisingly, research suggests that the Greenland shark is the slowest fish in the world, comparable to the “speed of a crawling baby” (Watanabe et al., 2012).
Instead of being vulnerable to faster warm-blooded predators, the Greenland shark actually is a top-level predator (MacNeil et al., 2012). It is at the top of the food chain with no predators of its own. Its larger size and poisonous flesh could have contributed to this.
What interests me about them is that despite being so slow and sluggish, Greenland sharks are actually capable of hunting much faster-swimming, warm-blooded seals for food! The ‘sleeping seal’ hypothesis (Watanabe et al., 2012), tries to explain this behaviour. It explains that these sharks creep up slowly to sleeping seals in the water to attack them. However, support for this hypothesis remains to be seen. It is a pity that this intriguing animal and its foraging behaviour remain understudied due to limitations in technology. I definitely look forward to more discoveries about it.
I believe the foraging behaviour of the Greenland shark reminds us of how there is no one best or essential characteristic which is key to survival. Each characteristic may be advantageous or disadvantageous, and it ultimately depends on the particular environment that an animal lives in and how it eventually adapts.
To find out more about this shark, watch:
MacNeil, M. A., McMeans, B. C., Hussey, N. E., Vecsei, P., Svavarsson, J., Kovacs, K. M., Lydersen, C., Treble, M. A., Skomal, G. B. , Ramsey, M. A & Fisk, A. T. (2012). Biology of the Greenland shark Somniosus microcephalus. Journal of Fish Biology, 80(5): 991–1018.
Watanabe, Y. Y., Lydersen, C., Fisk, A. T., & Kovacs, K. M. (2012).The slowest fish: Swim speed and tail-beat frequency of Greenland sharks. Journal of Experimental Marine Biology and Ecology, 426–427: 5-7.
“Greenland Shark,” by Eagle, D. Florida Museum of Natural History, January 2010. URL: http://www.flmnh.ufl.edu/fish/Gallery/Descript/GreenlandShark/GreenlandShark.html (accessed on 9 Apr 2013)
“Greenland Shark Somniosus microcephalus,” by Oceana, 2012. URL: http://oceana.org/en/explore/marine-wildlife/greenland-shark (accessed on 9 Apr 2013)
“Greenland Sharks,” by Jonathan Bird’s Blue World. URL: http://www.blueworldtv.com/ (accessed on 8 Apr 2013)
“Rare Encounter with Greenland Shark – Adam Ravetch,” by OneWorldOneOcean YouTube Channel, 11 April 2012. URL: http://www.youtube.com/watch?v=JrWEi2SVu8c (accessed on 7 Apr 2013).
“Slow Sharks Sneak Up on Sleeping Seals (and Eat Them)?” by Scales, H. National Geographic News, 26 June 2012. URL: http://news.nationalgeographic.com/news/2012/06/120626-greenland-sharks-seals-sleeping-animals-science/(accessed on 9 Apr 2013)
“View of Greenland shark mouth,” by Doug Perrine. URL: http://www.arkive.org/greenland-shark/somniosus-microcephalus/image-G57861.html (accessed on 8 Apr 2013)