Communal nesting behavior in mearns's squirrels (Tamiasciurus mearnsi)

Communal nesting has been observed frequently in arboreal squirrels of the genus Sciurus and Glaucomys, but only occasionally in Tamiasciurus. During 2006 and 2007, we trapped and radiocollared 38 adult Mearns's squirrels (Tamiasciurus mearnsi) in Baja California, Mexico, to examine their nesting behavior. We report for the first time instances of communal nesting in Mearns's squirrels. Same-sex groups were more common than mixed-sex groups. Females engaged more in communal nesting than males. Communal nesting behavior in Mearns's squirrels seems to be similar to other species of arboreal squirrels; decreasing as mean monthly temperature increases and during the breeding season.