A dolphin that echolocates a human in water can perceive not only the human’s outer shape but also what is inside, including skeleton and lungs. Tree frog embryos — ensconced inside their unhatched eggs — can detect the vibrations of an attacking predator and release an enzyme from their faces that dissolves the casings that house them, allowing them to exit and escape.
That I found myself surprised at so many moments while reading "An Immense World,” Ed Yong’s new book about animal senses, speaks to his exceptional gifts as a storyteller — though perhaps it also says something regrettable about me. I was marveling at those details because I found them weird; but it turns out, if I try to expand my perspective just a bit, they aren’t so weird after all. One of Yong’s themes is that much of what we think of as "extrasensory” is "simply sensory.” A term like "ultrasound” is "an anthropocentric affectation.” The upper frequency limit for the average human ear may be a measly 20 kilohertz, but most mammals can hear well into the ultrasound range.