What the Western Grey Squirrel Needs to Thrive

Photo from Oregonconservationstrategy.com

Photo from U.S. Fish and Wildlife Service (fws.gov)

The Western grey squirrel (Sciurus griseus) is the largest tree squirrel native to the western United States! 🐿🌲 These silver-tailed beauties provide an important service to the forests by helping to plant trees and maintain healthy mushroom communities by burying acorns and dispersing fungus along the forest floor. 🌰🍄

Once incredibly abundant throughout California and Washington, their populations are declining. In 1993 the Washington State Department of Fish and Wildlife listed them as a threatened species [1]. In California the western grey squirrel has been pushed to more rural areas at higher elevations. 

One reason why the western grey squirrel is struggling is habitat loss [2]. This species of squirrel is very picky when it comes to were to live. Western greys rely on mature forests with an abundance of oak 🌳 and pine  🌲trees in order to build nests, find proper food, and escape from predators effectively.  

The number and size of mature oakwood lands is decreasing as cities expand and the need for preventative wildfire suppression increases. Gaining a deeper understanding of how western grey squirrels utilize the forest to survive can help us better protect the remaining populations. 

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Two 'must-haves' for  western grey squirrel habitat

​1. High Canopy Connectivity 

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High canopy connectivity is another way of saying 'a lot of connected branches.' Tree squirrels prefer to travel up in the trees to avoid predators on the ground. They use this interconnected branch network as a super highway to move through the forest. In order to do this they need large areas that have a lot of mature trees whose branches overlap. Research has shown that squirrels prefer to leap about 3 feet across at the maximum [3]. Thus, an area with high connectivity would have lots of branches at this distance or less. 

​2. Oak Trees for Nesting 

Western grey squirrels prefer to use oak trees to build their nests. 🌳  Mother squirrels will use cavities in these trees to raise their babies. The cavities provide warmth and protection for their young and are more stable than nests made out of leaves or sticks. Without cavities squirrels will build nests also called dreys out of leaves and sticks. Greys also prefer to select oak trees for nesting that contain mistletoe [3]. Mistletoe brooms are used as a part of the nest structure providing support for the interior leaves and cushion.  

​What can we do to help the western grey squirrel? 

To keep the remaining western grey squirrel populations thriving we need to work together to maintain oak woodlands and encourage their restoration [4]. The forestry service and conservation groups in Washington and Oregon are utilizing data from ecological research on the land use and activity patterns of this species to aid in managing oakwood lands in ways that will promote grey squirrel populations. The more we can learn about what a healthy population of western grey squirrels needs to survive and thrive the more informed our decisions about city planning, land management, and fire suppression can be and the happier the western grey squirrel will be. 🐿💕🌳

​Citations: [1] ​Chris 1981 USDA General technical report PNW no. 133. [2] ​King 2014 Doctoral dissertation, UCLA. [3] ​Gregory et. al. 2010 The Journal of Wildlife Management, 74(1), 18-25. [4] oregonconservationstrategy.com