The Carlisle Mosquito Online

Friday, January 30, 2004

Features



The Junco and the Shrew
A surprising incident occurred at about 7 a.m. the morning of January 7, 2004. I was seated at our dining table in a sunroom, which offers a full view of the backyard and bird feeders. There is a simple bird feeder/shelter located near a stone wall about 15 feet from the sunroom. I had scattered birdseed, mostly sunflower seed, millet, and cracked corn, under the shelter. There are a few holes under the shelter, the largest of which is about one inch in diameter at the entrance. Mice, voles and shrews use these holes. Last week my wife D'Ann had seen a Short-tailed Shrew (Blarina brevicauda) emerge from this hole and take seeds back down the hole.

As usual, there were many small birds, including Dark-eyed Juncos, White-throated Sparrows, and a male Eastern Towhee foraging for seeds around and under the shelter. One of the Juncos was scratching for seeds close to the entrance of the hole, and began moving closer to the entrance in search of seeds. As I watched the Junco, I remembered D'Ann's shrew sighting, and thought, "Maybe this is not a good idea." Meanwhile, the Junco had progressed about halfway down the hole, headfirst. As I was watching, the Junco suddenly disappeared down the hole!

Although I can't prove it, I suspect the Junco was grabbed by the shrew. According to Godin, the Short-tailed Shrew is one of the most abundant New England mammals, and is the only mammal known to have a venomous bite. The venom acts to paralyze the prey, in the manner of a cobra bite. Godin states: " A small amount of this venom is enough to kill a rabbit. One scientist, bitten on the fingers while holding a Short-tailed Shrew, suffered shooting pains and swelling which in half an hour reached his elbow. The pain was so great he could not use one of his hands for three days."

The Short-tailed Shrew feeds mostly on insects, earthworms, and other small invertebrates, but will also take larger prey such as mice and voles, and possibly small birds. It also eats vegetative material such berries, fruit, nuts, seeds, and roots. The Short-tailed Shrew is reputed to be the most "fossorial" (burrowing) shrew and will construct its own burrows or use those of other species, especially voles. The shrew's venom allows the immobilized prey to remain alive for several days while being cached within the burrow. Shrews have a very fast metabolism and it is estimated that they can consume three times their body weight in food each day.

We subsequently saw the shrew a week after this incident, at about 4 PM. I had scattered seeds under the shelter the day before. We saw a shrew emerge from a different hole, come out just far enough grab a seed, and then return. It moved too quickly and unpredictably for me to get its photograph. I believe it was taking sunflower seeds. Prof. Philip Myers of the Univ. of Michigan Dept. of Zoology told me that he often live-traps this shrew using black sunflower seed as bait.

The author thanks Massbirders Phil Brown and Andrew Joslin for providing informative URLs cited below, and Prof. Philip Myers for his comments and permission to reproduce his shrew photograph.

References:

1. Alfred J. Godin, Wild Mammals of New England, Field Guide Edition, DeLorme Publishing Co., Yarmouth, ME, 1977, pp.25-27.

Tom Brownrigg is a member of the Carlisle Conservation Commission. His interests include birding, nature study, and digital photography.


2004 The Carlisle Mosquito