Mountain Moment: Call of the Pika

Why does the pika call? To warn of predators or entice mates? Maybe to just say "hi" to a friend? Pika (Ochotona princeps) calls may all sound like "eep!" to human ears, but to a pika they can be very distinct. There is research that pikas can recognize other individual pikas by their call! Sounds is an important way to connect when you are a small animal in a big landscape. What do you think this pika is saying?