Sciurillus pusillus
Creators: name: Wilson, Don E.
name: Thomas E. Lacher, Jr
name: Mittermeier, Russell A.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Sciuridae
Sciurillus
Sciurillus pusillus

description: 1. Neotropical Pygmy Squirrel <i>Sciurillus pusillus</i> <b>French:</b> Ecureuil pygmée / <b>German:</b> Neuwelt-Zwerghérnchen / <b>Spanish:</b> Ardilla pigmea neotropical <b>Other common names:</b> Pygmy Squirrel <b>Taxonomy.</b> Sciurus pusillus E. Geoffroy Saint-Hilaire, 1803 “Cayenne” in French Guiana. Distribution of subspecies is not well defined. Probably represents several dis- tinct species; molecular data suggest divergence between the populations occurring in Peru and French Guiana (perhaps ten million years ago). Three subspecies are recognized. <b>Subspecies and Distribution.</b> S.p.pusillusE.GeoffroySaint-Hilaire,1803—theGuianasandNEBrazil. S.p.glaucinusThomas,1914—LowerBrazilianAmazonandinteriorGuyana. S. p. kuhlii Gray, 1867 — Upper Amazon of NE Peru, and likely W Brazil and SE Colombia. It has been reported in Venezuela S of the Orinoco, but data are not adequately substantiated. <b>Descriptive notes.</b> Head-body 89-115 mm, tail 89-120 mm; weight 33-45 g. The Neotropical Pygmy Squirrel has a gray dorsum, suffused with yellow; head is cinnamon to red. Ears are black-tipped with prominent white-to-buff post-auricular patches. Venter is buff to gray. Nominate subspecies pusillus is more buff to brown on body and reddish on head, glaucinus is the palest subspecies, and kuhlii generally lacks post-auricular patches. Baculum has distinctive axe-like shape when viewed from side; shaft resembles axe handle and distal portion resembles axe head. Base of baculum is thick and cylindrical and tapers distally along shaft forming a neck or constriction. <b>Habitat.</b> Mature evergreen lowland Amazon forests. Densities of the Neotropical Pygmy Squirrel do not appear to be high, with 0-3 ind/km* of transect in French Guianan and Peruvian rainforest. They mainly use high and low restinga (coastal moist broadleaved forest) and areas with a higher density of trees that are greater than or equal to 30 cm diameter at breast height/ha compared to random areas in igapo (seasonally inundated black-water) forest. They use trees that are larger in diameter, taller, and have a larger live crown compared to random trees, which suggests that the Neotropical Pygmy Squirrel is associated with mature forests. <b>Food and Feeding.</b> Major food sources of the Neotropical Pygmy Squirrel are sap and other exudates of large trees that these squirrels frequent on a regular basis. Food trees are often distinguished by an accumulation of bark chips at the base. Foraging is almost exclusively arboreal as the Neotropical Pygmy Squirrel rarely descends to the ground. <b>Breeding.</b> Breeding in the Neotropical Pygmy Squirrel is preceded by several males chasing an estrous female. Pregnant and lactating females have been documented in June with litter size of one or two. <b>Activity patterns.</b> The Neotropical Pygmy Squirrel is diurnal and energetic and active from 06:00-17:00 h with a peak in activity from 08:00-12:00 h. Adults and juveniles quickly dart through the canopy and ascend and descend large trees. Much of the day is spent on tree trunks. Solitary individuals or family groups are seen feeding at nearly every layer of the canopy, but the Neotropical Pygmy Squirrel appears to be most common in high-to-mid canopy. Termite nests can be used by solitary individuals and groups for nocturnal nests; fibers of the machimango tree (Eschweilera, Lecythidaceae) serve as nest material. The Neotropical Pygmy Squirrel tolerates modest levels of forest fragmentation. Alarm call is given at varying levels of intensity but sounds much like a cricket with a more uncommon trill also heard. Vocalizations are frequent and permit easy detection. <b>Movements, Home range and Social organization.</b> Young siblings will often play with each other and an adult. Solitary individuals or family groups feed at nearly every layer of canopy but appear common around 10 m. Agonistic chases are common. In Peru, six individuals including adults and young shared the nest. Most frequent locomotory mode of the Neotropical Pygmy Squirrel is claw-climbing. While foraging and feeding,tail is extended, not reflected over body as in many other species of tree squirrels. <b>Status and Conservation.</b> Classified as Data Deficient on The IUCN Red List. No information on current population status is available, but the major threat to the Neotropical Pygmy Squirrel is destruction of its forest habitat. <b>Bibliography.</b> Amori, Koprowski &amp; Roth (2008), Anthony &amp; Tate (1935), Calderén-Capote et al. (2015), Dalecky et al. (2002), Hafner et al. (1994), Heymann &amp; Knogge (1997), Jessen, Gwinn &amp; Koprowski (2013), Jessen, Palmer &amp; Koprowski (2013b), Palmer &amp; Koprowski (2015), de Vivo &amp; Carmignotto (2015), Youlatos (2011).
description: Published as part of <i>Don E. Wilson, Thomas E. Lacher, Jr &amp; Russell A. Mittermeier, 2016, Sciuridae, pp. 648-837 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions</i> on page 711, DOI: 10.5281/zenodo.6840226