Squirrels constitute a very large group of mammals in the USA. Here are two examples of very common ground squirrels.
Harris Antelope Squirrel
The Harris antelope squirrel is very common in the Phoenix area of Arizona. A colony of them lived in a 1-acre plot of scrub beyond the house where we stayed in November 2003.
California Ground Squirrel
The California ground squirrel is extremely common in central California around San Luis Obispo County. In fact, this was the most common form of road kill we saw as we drove the back roads around Lake San Antonio in February 2004. This particular citizen was spotted on the the rocks at the side of the harbor at Morro Bay on the coast. California ground squirrels are 14 to 19 inches long, one-third to one-half of which is tail. Unfortunately, when startled they instinctively run for their home burrow hole rather than the nearest one. For those living on roadsides (a preferred habitat for some reason), running for the home burrow may be fatal.
This image was made in dim morning light at 260 mm focal length with a Canon 100-400 mm L IS lens at f/5.6 and 1/20 sec exposure using an ISO speed of 200. The value of image stabilization is clear!