The basic 'vocabulary' of Richardson's ground squirrels consists of a variety of squeals, chirps, chirrs, whistles, and teeth clatters. They also give two distinct alarm calls, which humans can easily learn to recognize.
The first alarm call is for aerial predators, which tend to approach rapidly in a straight line. It consists of a short, low-pitched chirp that changes frequency. Upon hearing this call, ground squirrels run for cover.
The other alarm call is for terrestrial
predators, which tend to approach relatively slowly. This one consists
of a long, high-pitched whistle with a constant frequency. When this
call is heard, ground squirrels stand up and scan the area.