Shrews

Northern Short-Tailed Shrew, Spruceline Farm (August, 2014)

Northern Short-Tailed Shrew, Spruceline Farm (August, 2014)

This shrew had a notably short tail. I observed its long whiskers and recognized that shrews must have a highly developed sense of touch. He/she also had tiny eyes.  I learned that they have poor vision and cannot see objects but they can detect light from dark.  They use a form of echolocation, similar to what bats use, to “see” objects. They send out a series of ultrasonic clicks and then listen for the returning echoes. I wonder if they sense the vibration of the returning echo with their whiskers as well?  I noticed that this shrew’s ears are well hidden underneath its fur. You can also see from this photo that the shrew’s claws are quite big. I also learned that northern short-tailed shrews are the best (out of all of the NA shrews) at burrowing. They are good at tunneling through leaves, plant debris, and snow with their strong paws and tough snouts.

Northern Short-Tailed Shrew (Spruceline Farm, August 2014)

Northern Short-Tailed Shrew (Spruceline Farm, August 2014)

The Northern Short-Tailed Shrew is the largest shrew in North America with a skull length of 25mm.  It is also one of the very few venomous mammals in North America. This shrew has poisonous saliva that can paralyze or kill insects or even subdue larger prey such as frogs or mice. They do not use their venom like a snake or a spider might, instead, they chew the venom into the prey until the prey is subdued. Venomous shrews – amazing.

Shrew Skull

Shrew skull

This tiny skull was found in a conifer forest beside a wetland on the Kinghurst Forest Nature Reserve in Grey County.  After comparing various skulls in the Peterson’s Guide to Mammals, the best match seems to be a Least Shrew. According to the Peterson’s Guide to Mammals, “all North American shrews have reddish tipped teeth.  Least Shrews are social in comparison to other shrews.  Up to 31 adults may share a nest together.  They also have very short tails.”*

Shrew Teeth

Least shrews have 4 unicuspids (teeth) but the 4th is very tiny.*  Unicuspids are the small teeth between the big incisors (at the front) and the molars (at the back). This photo is a bit blurry (sorry about that) so exact species identification is quite challenging really.  The skull lenth was approximately 18mm.  In comparison, the least shrew has an average skull length of 16 mm and the masked shrew has an average skull length of 17 mm*.  However, the masked shrew has 5 unicuspids but the 5th is tiny*.  As already stated – challenging to identify.

*Reid, F. A., 2006, Mammals of North America, Houghton Mifflin Company, NY.

Northern Short-Tailed Shrew Trail

Northern Short-Tailed Shrew Trail (Algonquin Park, February 2015)

Northern Short-Tailed Shrew Trail (Algonquin Park, February 2015)

This Northern Short-Tailed Shrew trail measured 1 and 1/4 inches wide.  The shrew used a bounding gait on top of deep snow.  Amy, from the White Pine Program in Maine, showed me an awesome trick called “Snow Glow”.  If you hollow out the snow from underneath a track, the track will glow as the sunlight backlights it from underneath.  Thanks Amy:)

Shrew Track Snow Glow (Algonquin Park, February 2015)

Shrew Track Snow Glow (Algonquin Park, February 2015)

Shrew Trail in a “cursive e” shape:

Shrew Trail in "Cursive e" shape (Guelph Lake Nature Centre, February 2015)

Shrew Trail in “Cursive e” shape (Guelph Lake Nature Centre, February 2015)

One of our adorable young naturalists (Isaac) observed a similarity between this shrew trail and a cursive “e” shape.  I love that.  I have seen this type of pattern a couple of times with Northern Short-tailed shrews travelling on the surface of the snow.  Classic “cursive e” pattern – something to look for:)

Shrew Tracks

Vole, Shrew or Mouse Tracks (Algonquin Park, February 2015)

Vole, Shrew or Mouse Tracks (Algonquin Park, February 2015)

While tracking with Dan Gardoqui in Algonquin Park, he showed me what to look for when identifying clear tracks for voles, shrews and mice. Voles and mice have four toes on their front feet and five toes on their rear feet. Shrews have five toes on their front and five on their rear feet.

Shrew Incisor Marking

Shrew Chewing (September, 2014)

Shrew Chewing (September, 2014)

We observed these chews underneath a snake board in Kiera’s Forest.  We have previously seen a Northern Short-tailed shrew living under the board.

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