One of the most well-documented squirrel species is the Eurasian red squirrel. Much of the research on these animals stems from concerns over that fact that their numbers are currently threatened by foreign gray squirrels, which are replacing them.
Eurasian Red Squirrel
Similar to their American cousins, Eurasian red squirrels typically have reddish topcoats and cream-colored bellies. They’re distinguished by the wispy fur that grows into a high point above their ears. Their range extends throughout both Europe and Asia, and they prefer evergreen forest habitats.1
Eurasian red squirrels can live to be almost 15 years old, but most don’t survive for longer than 12 years in the wild.2 Also, there is some evidence that they tend to live for only 1 or 2 years in regions with high elevations and severe winters.3
Due to the introduction of Eastern gray squirrels into Italy, Ireland, and Great Britain, populations of Eurasian red squirrels in these areas are currently in decline.1,4 Not only do hardy gray squirrels outcompete red squirrels for resources,4 but they can also carry a virus that is fatal to red squirrels.
1 MacKinnon, K. (1978). Competition between red and grey squirrels. Mammal Review, 8(4): 185-190.
2 AnAge: the animal ageing and longevity database. (2014). Retrieved from http://genomics.senescence.info/species/entry.php?species=Sciurus_vulgaris
3 Rodrigues, D., Wauters, L., Romeo, C., Mari, V., Preatoni, D., Mathias, M.,…Martinoli, A. (2010). Living on the edge: can Eurasian red squirrels (Sciurus vulgaris) persist in extreme high-elevation habitats? Arctic Antarctic and Alpine Research, 42(1): 106-112. Retrieved from https://www.researchgate.net/publication/230660296_Living_on_the_Edge_Can_Eurasian_Red_Squirrels_Sciurus_vulgaris_Persist_in_Extreme_High-elevation_Habitats
4 Gurnell, J., Wauters, L., Lurz, P., & Tosi, G. (2004). Alien species and interspecific competition: effects of introduced eastern grey squirrels on red squirrel population dynamics. Journal of Animal Ecology, 73(1): 26-35. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2004.00791.x/full