Recently Sighted: Squirrel Midden

Squirrel middens are interesting, but they are often overlooked by casual observers. The word midden means “refuse heap” and is a term that naturalists borrowed from archeology. Originally the term was “kitchen midden” referring to places that humans discarded bones, seeds, food scraps and even broken pottery.

Gray Squirrel midden

Recently, I noticed a pile of Norway Spruce (Picea abies) cone “cobs” and scales. An Eastern Gray Squirrel (Sciurus carolinensis) perched on a branch stub about 30 feet off the ground. She sat with her back to the trunk and dropped cone “cobs” and scales forming a large pile. She must feel safe here and returned frequently to eat. The midden comprised several hundred “cobs” and thousands of cone scales making a pile on the ground 10 inches deep and three feet in diameter. I poked through the pile and I discovered no missed seeds. This is the largest Gray Squirrel midden I have ever found. The cones were collected off the ground or cut out of the tree. Gray Squirrels spread their food hoarding over a wide area because they bury nuts individually. This results in smaller middens.

Red Squirrel (Tamiasciurus hudsonicus) middens are typically larger than Gray Squirrel middens. Red Squirrels store their winter food in caches in hollow spaces in trees or, unfortunately, in buildings. Their middens can accumulate in a local area all winter and sometimes are the refuse from several squirrels. The largest one in my field notes was 5 feet in diameter and three feet deep. It was several layers deep and appeared to have accumulated over at least three winters.

Now is a good time to look for squirrels forming middens. If you are lucky, you might find a squirrel feeding and adding to a midden. They are fun to watch.

 
Copyright 2020 by Donald Drife

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Michigan’s Spruces (Picea)

Spruces have needles less than 20mm (3/4 inch) long with square cross-sections. They never occur in bunches, just one needle per node. They can be confused with Balsam Fir (Abies balsamea) but Firs have needles with flattened cross-sections. If you can roll a needle in your fingertips then it is a spruce.

Balsam Fir and Spruce Needles and Branchlets

Balsam Fir and Spruce Needles and Branchlets

Michigan has two native spruces, Black Spruce (Picea mariana) and White Spruce (P. glauca). Norway Spruce (P. abies) is now naturalized into the state.

Picea mariana branchlets

Black Spruce Branchlets

Picea mariana pegs and cones

Black Spruce pegs and cones

Black Spruce has needles shorter than 16mm (5/8 inch) and densely pubescent, meaning furry, first year branchlets. The needle bases, which sit on a peg-like projection, are difficult to see. These peg-like projections stick out at 90 degrees to the twig. If cones are present, they are about as wide as they are long. In southern Michigan, Black Spruce grows only in cool bogs. North of Bay City, it will also grow in upland forests and interdunal swales. Even in the north, it prefers a damp habitat and often occurs with Tamarack (Larix laricina) and White Cedar (Thuja occidentalis). The common name refers to the dark needles this tree normally has.

Picea glauca needles and cone

White Spruce needles and cone

White Spruce has needles that are normally longer than 16mm (5/8 inch) and hairless first year branchlets. The needle bases are easily seen. The peg-like projections  point forward at approximately 60 degrees from the twig. Cones are two to three times longer than wide. The tree’s native range is north of West Branch. It grows in similar habitats as Black Spruce but will also thrive in drier locations. The common name refers to the waxy layer on the young needles.

Picea abies needles and cone

Norway Spruce needles and cone

The native range of Norway Spruce is central and northern Europe. It is escaping throughout Michigan. The branchlets droop and its cones are large, approximately 130mm (5 inch) long. Norway Spruce is commonly planted and beginning to escape into natural areas. Its needles are stiff and have rows of minute openings properly called stomata.

Picea abies stomata

Norway Spruce stomata

Copyright 2014 by Donald Drife

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