The true phylogenetic classification of tree shrews is controversial. Some argue they should be placed in the Primata order, even though tree shrews and primates don't share any derived characteristics. Genetic analyses of the group have put them variably in proximity to the primates. At present tree shrews have been placed in the Scandentia order, which is composed of 20 species and 5 genera. These small mammals have relatively small body mass, average body weight is 142 grams with a body length of 19.5cm. Interestingly, the tree shrew has the highest brain to body mass ratio of any mammal, including humans. Tree shrews are typically monogamus in mating and produce up to 3 offspring from each pregnancy. At approximately 40 days, young are weaned and rapidly become sexually mature, typically at 3 months of age.
The tree shrew is broadly distributed across Southeast Asia. Most often found in the tropical rainforests, although they are best described as semi-arboreal (tree-dwelling).
The tree shrew species Tupaia belangeri, will be sequenced as part of an initiative to expand sequencing of mammalian genomes for the purpose of expanding the annotation of the human genome. The plan is to create a draft sequence assembly from 6X whole genome coverage of a female tree shrew. The tree shrew DNA source was obtained from Dr. Eberhard Fuchs, German Primate Center, Goettingen, Germany. For more information on the mammalian genomes represented in this initiative please visit the Genome Sequencing Proposal page. The National Human Genome Research Institute (NHGRI), National Institutes of Health (NIH) is providing funding for the sequence characterization of the tree shrew genome.