Good listeners 
Galapagos marine iguanas cannot communicate vocally to alert each other to danger, but they have developed an alternative method for dodging predators: eavesdropping on local mockingbirds, whose songs change tune when hunting hawks approach. Ecology and evolutionary biology graduate students Maren Vitousek, James Adelman, and Nathan Gregory and a colleague from the University of Bath in the United Kingdom tested the iguanas’ ability to discriminate between mockingbird songs and alarm calls using digital recordings. For a nonvocal species, the iguanas displayed “a remarkable degree of auditory discrimination,” the authors reported, vigilantly perking up when the alarm call sounded. The study, published in Biology Letters, showed for the first time that a nonvocal species can detect approaching threats by listening to another species’ alarm calls.