What is the Origin of the Flying Squirrel?
While the fly-by-night mammal is the most widely distributed rodent species, its diversity was very low during the Miocene, when open habitats dominated the landscape. Only the genera Petauristodon and Sciurion have been discovered from the middle and early Miocene. The wide-open habitats of central North America are the most suitable for flying squirrels, but a lack of suitable habitats would have restricted the radiation of this species across the continent.
The Miocene origin of the flying-squirrel phylogeny is still unclear. Previous estimates, based on molecular data, placed the split between the flying-squirrel and tree a few million years earlier than now. However, a recent study found that the earliest records of new genera in Europe and North America coincide with the early Miocene. A similar pattern was observed in North America, where the small genus Blackia was first recorded.
The initial diversification of the flying-squirrel’s population during the early Miocene coincided with a time of high mean global temperatures. These temperatures peaked at around 17 to 15 Ma, coincident with the Mid-Miocene Climatic Optimum. These high temperatures favoured the development of humid warm-temperate broadleaf and mixed forests at mid-latitudes in Eurasia and North America. These forests provided an ideal environment for flying squirrels to spread and evolve.
The flying squirrel family comprises many endemic species found throughout the world. The fossil record of the flying squirrel family contains a wealth of paleoclimatic data. The glans on the penis of the Himalayan Large-Eared Flying Squirrel are extremely long, a trait found in few other species. The species is known by its Chinese name, the Himalayan Flying Squirrel.
The phylogenetic tree of the flying squirrel family provides a timeline for the evolution of the species. Although the phylogenetic trees of different groups overlap, the estimates of when flying squirrels diverged from each other are consistent. Extant flying squirrels are categorized into two subtribes, and the most recent extant genera diverged in the early Miocene. The species of the flying squirrel derived from the extant genera during this period.
The phylogenetic tree of the flying squirrel reveals that the flying squirrels originated in the early Miocene, when they were related to their New World cousins. However, the species diverged from their Asian relatives in the late Miocene, when Beringia was a newly-emerging continent, indicating that trans-Beringian dispersal may have played an important role in shaping their evolutionary history.
The distribution of the flying squirrel is varied and depends on the climate. One season sees an aggregation of a large number of flying squirrels, while the other is marked by fewer animals. In winter, the flying squirrels remain mainly inactive, staying in their nests for the duration of the breeding season. Their aggregation tendencies correlate with temperature. This is a species with wide geographical distribution, and this diversity may be beneficial for human conservation efforts.
The two species of flying squirrels are found in parts of the Appalachian region. The southern flying squirrel occupies tree cavities and feeds on insects. The northern flying squirrel lives in southeastern Alaska and extends northwards to Tennessee and the western United States. It is found throughout the United States. Both species have very similar ranges. However, their distributions overlap in areas of the Appalachian region. They also occur in southern Canada.
The Northern flying squirrel is listed as an endangered species by the IUCN Red List. Threats to its habitat are deforestation, human interference and hemlock wooly adelgid infestation. In addition, small-scale logging, which has been common in Kerala and the neighboring states of Tamil Nadu, is a threat to the flying squirrel population. Also, acid precipitation is a threat to its soil and vegetation.
Flying squirrels can be cute, but if you approach them or even try to kill them, they may retaliate. Their droppings contain Salmonella, which causes diarrhea and vomiting. Severe cases may require medical treatment. Another disease that may be transmitted through squirrel feces is Leptospirosis. The disease manifests itself as flu-like symptoms that require medical treatment. Hence, it is important to prevent flying squirrel infestation.
Jessica Watson is a PHD holder from the University of Washington. She studied behavior and interaction between squirrels and has presented her research in several wildlife conferences including TWS Annual Conference in Winnipeg.