(repeat)  SMS isn’t the original instant messaging system.  Plants can send chemical warnings through their leaves in a fraction of a second.  And while we love being in the messaging loop – frenetically refreshing our browsers – we miss out on important conversations that no Twitter feed or inbox can capture. That’s because eavesdropping on the communications of non-human species requires the ability to decode their non-written signals. Dive into Arctic waters where scientists make first-ever recordings of the socializing clicks and squeals of narwhals, and find out how climate shifts may pollute their acoustic landscape.  Also, why the chemical defense system of plants has prompted one biologist to give greenery an “11 on the scale of awesomeness.” And, you can’t see them, but they sure can sense one another: how communicating microbes plan their attack. Guests: Susanna Blackwell – Bio-acoustician with Greeneridge Sciences. Hear her recordings of narwhals here. Simon Gilroy – Professor of botany, University of Wisconsin, Madison. His video of glowing green caterpillar-munched plants can be viewed here. Peter Greenberg – Professor of microbiology, University of Washington, Seattle