The squirrel population at Boston Public Garden is quite high. At times, it feels as if there are two per square foot. Since visitors frequently feed the squirrels, they have become bold. When I visited Thursday morning, one came up, grabbed my leg with its paws, and then moved a couple feet away, staring at me. Among all the gray squirrels, though, one stood out.
This is a white morph of the Eastern gray squirrel (Sciurus carolinensis). According to Untamed Science, it is a rare, naturally occurring trait.
The squirrel is not an albino, because it does produce some pigment. It has black eyes, for instance, rather the the red eyes one would expect of an albino.
Apparently, there are multiple white squirrels nearby at Massachusetts General Hospital. MGH has produced a video explaining the phenomenon: