Animals send out messages for very specific reasons, such as to signal danger or for mating rituals. Some of these calls, like the ones that follow, are so loud they can travel through water or bounce off trees for miles to get to their recipient.
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the Editors of Publications International, Ltd.. "7 Animals that Can Be Heard for Long Distances" 30 October 2007. HowStuffWorks.com. <http://animals.howstuffworks.com/animal-facts/7-animals-that-can-be-heard-for-long-distances.htm> 16 September 2014.