Jessen, R. R., G. H. Palmer, and J. L. Koprowski. 2013. Neotropical pygmy squirrels (Sciurillus pusillus) share termite nests. Ecotropica 19:73-76.

Nest-site selection is important for reproduction (Benson et al. 2008) and also provides a place for other activities such as resting and shelter or protection from weather and predators (Sealander Jr. 1952, Steele & Koprowski 2001). Nesting habits are also influenced by level of sociality, and can confer fitness advantages (Alexander 1974). Communal nesting is an example of increased sociality found in mammals, including tree squirrels (Wolff & Lidicker Jr. 1981, Layne & Raymond 1994, Koprowski 1996, Ebensperger et al. 2004). Sociality among tree squirrels is poorly understood and communal nesting occurs only rarely in some species of tree squirrels in temperate forests (Halloran & Bekoff 1994, Layne & Raymond 1994, Koprowski 1996).

Tree squirrels in temperate regions nest in cavities of trees, dreys (arboreal bolus structures constructed of twigs and leaves), and occasionally also in burrows (Steele & Koprowski 2001, Thorington Jr. et al. 2012). Diversity of tree squirrels is highest in the tropics, with 19 species occurring in the Neotropics, but few studies have been conducted in these areas (Koprowski & Nandini 2008). Little is known about nesting habits of Neotropical tree squirrels but they appear to use drey and cavity nests (Emmons & Feer 1997). Many Neotropical tree squirrels are believed to be solitary (Emmons & Feer 1997) but some species, such as northern and southern Amazon red squirrels (Sciurus igniventris, S. spadiceus), and Neo-tropical pygmy squirrels (Sciurillus pusillus, Geoffroy 1803), forage in groups of ≤ 4 individuals (Heymann & Knogge 1997, Eason 2010, R. Jessen, pers. obs.). Neotropical pygmy squirrels are diurnal and the smallest tree squirrels in the western hemisphere, but there is a substantial lack of information about their life history and ecology (Emmons & Feer 1997, Koprowski & Nandini 2008). Here we report our observations of Neotropical pygmy squirrels using termite nests to nest communally.