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Asta loves exploring and studying the exciting world under the sea. Each week, she will attempt to learn and answer her reader's most burning marine science questions, and provide some resources that help turn the question into a lesson plan! This week, she delves into the world of the prickly pinnipeds, to answer a reader's question: "Why do Seals need Whiskers? What do they do with them?" -Sam, Age 10  Photo courtesy of http://www.cafeknaus.ch/sites/default/files/flying_burger.jpg Imagine this.... You come home from a busy day at school and your tummy's rumbling with hunger. You go into the kitchen to try and make your dinner, but the power's out and you can't see a thing! Worse yet, every time you grab for a bite of your favorite food, it zooms off away from you! What senses would you rely upon to relieve the rumble?  Photo courtesy of asknature.org. We may not have to worry too much about our food escaping from our refrigerator, but for the common harbour seal (also known as Phoca Vitulina), chasing their food in the dark is a pretty common problem. Harbour seals are members of the taxonomic clade "Pinnipedia". In Latin, this word means "feather or fin foot". This order includes 33 different types of marine mammals, but all of them share some characteristics, like long flat flippers, both at the front and rear of their bodies. Harbor seals are a member of the Phocidae family, also known as "true seals". They can be differentiated from other pinniped species by their lack of external ears, streamlined bodies and their long facial whiskers, known as mystacial vibrissae. Check out this great video from Lunchbox Lectures to learn more about the physiology of the Harbour Seal!  Are these cool? Photo From https://pbs.twimg.com
Harbour Seals don't just think whiskers look cool, like some humans do. They actually use their whiskers (also known as mystacial vibrissae) to receive tactile (touch) information from their surroundings. As harbor seals grow and mature into adulthood, they grow a series of long white hair like white bristles (called vibrissae) on either side of their noses. These long hairs are attached to the seal's muzzle, and are surrounded by motion sensing cells and nerves. The vibrissae have a "specialized undulated surface structure" which allows them to detect the speed and direction of water currents. The nerves attached to the vibrissae tell the seal's brain which direction a fish or animal might have moved through the water nearby by identifying its " hydrodynamic trail" (also known as a wake pattern.) Noticing an animals wake pattern can help seals discover another animal's direction, location, size, and other details about where the animal is going, and fast! This is really helpful info for a seal swimming in dark or noisy water.  A very cool study was conducted using a seal named Henry at the Marine Science Center in Germany recently (2011). A scientist called W. Hanke and his colleagues wanted to find out how seals used their vibrissa to hunt for prey, so they covered Henry's ears and eyes, and trained Henry to follow the trail of a variety of differently shaped fish tails. Even 35 seconds after motion had been created in the water, Henry could accurately track the movements of the tails, and was able to tell the types of tails apart!  Another interesting study last year showed that seals can actually use their vibrissae to measure the relative size of their food. Seals can judge the size of a fish based on the wake they leave as they move through the water, and decide between a bigger fish and a smaller one.
More than just a fashion statement, the harbour seal's whiskers help it survive! References: Bates, M. July 13, 2012. "Whiskers Seal the Deal."Psychology Today online. Retrieved February 6, 2014.http://www.psychologytoday.com/blog/animal-minds/201207/whiskers-seal-the-deal Hanke W, Witte M, Miersch L, Brede M, Oeffner J, Michael M, Hanke F, Leder A, Dehnhardt G. August 2010. "Harbor seal vibrissa morphology suppresses vortex-induced vibrations." Retrieved February 6, 2014. J Exp Biol;213(Pt 15):2665-72. doi: 10.1242/jeb.043216. Davies, E. 17 Feburary, 2013. "Seals judge size using their whiskers." BBC Nature article. Retrieved, February 6, 2014 from http://www.bbc.co.uk/nature/21442501 Daily Mail, 12 May 2011. "Harbor Seals use whiskers to detect fattest fish." Daily Mail Article.Retrieved February 6, 2014 from http://www.dailymail.co.uk/sciencetech/article-1386368/Harbour-seals-use-whiskers-detect-fattest-fish.html The Journal of Experimental Biology.May 16, 2011. "Seals sense shapes using their whiskers to feel wakes". ScienceDaily. Retrieved February 6, 2014 from www.sciencedaily.com/releases/2011/05/110512083141.htm
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