The mating season starts at the onset of the monsoon season in December and lasts until February. Oestrus and preoestrus behavior is characterized by adult males pursuing adult females. Males emit chattering, and appear to be extremely excited. They also chase each other and fight. Females do not actively choose a partner among the male participants of chases. The dominant male gains access to females. In tropical rainforest habitats in West Malaysia, population density varies from two to five animals per hectare. Their annual breeding coincides with the abundance of invertebrates after the dry season. Their main reproductive period is between February and June, and their litter size is invariably two. Some females breed more than once a season, and the age at first pregnancy is seven months. The main period of emigration or mortality of young is during the breeding period or monsoon. The species was first described in February 1820 by the French explorers Pierre-Médard Diard and Alfred Duvaucel in their jointly written article ""Sur une nouvelle espèce de Sorex — Sorex Glis"", which is preceded by an illustration. They observed specimens in Penang and Singapore, and considered them a species of "Sorex", and not as a new genus. Between 1821 and 1940, several zoologists described the species from other areas. The species still retains many forms of uncertain rank and validity, and is pending a detailed study. Some forms were formerly considered synonyms of "Tupaia glis"; some were elevated to species level. Synonyms include: Common treeshrews are threatened due to deforestation and ensuing human activities in agriculture (for example, using trenchers to dig ditches), plantations, and commercial logging. Moreover, other pressures, such as hunting for food and sport, can create pressure to the species. "Tupaia glis" is used by researchers as animal models for human diseases because of their close relationship to primates, and their well-developed senses of vision and hearing. Research studies have included hepatitis. Another instance has been documented where an individual of "Tupaia glis" developed breast cancer.