Curious Chipmunks

by Nancy Olmstead

Crouching chipmunk

A curious chipmunk (photo courtesy of Gilles Gonthier,

A month ago I was walking in the woods and it seemed like I couldn’t go more than a few feet without disturbing another chipmunk.  The little brown stripe-y streaks were running all over the place, stopping to chirp and chatter at me as I passed.  Don’t worry, buddy, I don’t want your nuts.

We’re having a mast year in the northeast.  The oaks, beeches, and other masting trees are making a bumper crop of seed, which chipmunks eat and store by the cheekful.  This probably explains the superabundance of chipmunks.  The eastern chipmunk, Tamias striatus, can tell when the fall harvest is going to be good.  So they go all out making babies over the summer.  Some of the animals I’m seeing now are probably this year’s offspring, rushing to find, secure, and fill their burrows before settling down for their long winter rest.

Eastern chipmunk with full cheek pouches

Eastern Chipmunk with cheeks filled of food supply, Cap Tourmente National Wildlife Area, Quebec, Canada (image courtesy of Cephas,

Scientists have also studied this phenomenon in red squirrels, and chipmunks may be similar.  After all, chipmunks are a kind of squirrel.  They belong to the family Sciuridae, the sciurid rodents, which includes chipmunks, ground squirrels (e.g., prairie dogs), marmots (e.g., woodchuck), and tree squirrels (e.g., gray and red squirrels and flying squirrels).  Red squirrels are also known to anticipate high seed crops and reproduce accordingly.  Females may even have a second litter in the summer that precedes a big fall.

But how do chipmunks and red squirrels know that it’s going to be a good year?  The jury is still out on that question.  It’s hard to measure what individual animals are using as a cue to guide their reproductive “decisions.”  (And by using the word “decisions,” I don’t mean to imply that chipmunks and squirrels have consciousness, just an instinct to reproduce when certain cues are present.)

Scientists involved in these studies have suggested that the visual stimulus of an abundance of flowers may clue the squirrels in, but that explanation is less convincing for chipmunks, who spend more time on the forest floor than up in the tallest trees.  Chipmunks may be able to smell the upcoming bounty by homing in on the subtle scent of all those beech, oak, and maple flowers.  However they do it, it’s pretty cool.

Blue jays and bird colors

by Nancy Olmstead

The woman who lives downstairs from me feeds the pigeons almost every morning.  I know she’s out there when I hear a great swooshing of wings: dozens of pigeons flutter down to our driveway to greet her.  She’ll also put out peanuts for the squirrels.  Sometimes a crafty blue jay slips in there and grabs a peanut.

One of those wily blue jays flew up to the fire escape outside my kitchen window, and as it was adjusting its peanut, I got a good look at it.  Blue jays are such a bright blue color; it’s shocking in our Burlington landscape of brown and gray city birds.

Birds come by their colors in different ways.  The blue of a blue jay is not a pigment; it’s created by the physical structure of the feather.  The color is all in the way the molecules are arrayed.  If you ground up a blue feather, thus breaking apart the structure, there wouldn’t be any color anymore.  If you backlight a blue jay feather, you won’t see the blue anymore.  Next time you find one, place it between your eye and a flashlight beam, or hold it up to the strong sun – no blue.

In contrast, northern cardinals borrow their bright red color from plants.  The carotenoid pigments that make a cardinal red can’t be synthesized by animals; they have to be ingested from plants in a bird’s diet.

What are all those feather colors for, anyway?  Scientists know that birds have good color vision.  In species where the male and female are colored differently, color is usually important in mate choice.  A female American goldfinch is picky about which male she partners up with – a male with lovely, bright yellow color is preferred, while a male with drab plumage could find his partner straying.

Colors can also be structurally important.  The most abundant feather pigment is melanin, which gives strength to areas of the feathers that need to be particularly resistant to wear, like wing tips.  Herring gulls are a good example of a bird with these melanin-rich wing tips – they show up as an almost-black color.  Many terns also have this pattern of dense melanin pigmentation at the wing tips.

I’m not sure what role color plays in the life of a blue jay, but I’d like to find out.  Male and female blue jays look pretty similar to me, so perhaps color isn’t a big deal in mate choice.  Or maybe there are small, subtle color variations that I haven’t picked up on yet.

I should team up with the lady downstairs.  I could bring the blue color chart and maybe she could bring the bag of peanuts.

Canada mayflower – more than meets the eye

By Nancy Olmstead

What is an individual plant?  It’s pretty clear when you are looking at an individual squirrel, or an individual blue jay: it starts at the tail and ends at the head.  The question gets harder to answer when you look at some kinds of plants, including many of our New England forest wildflowers.  Scientists who study forest plants need to be able to tell one individual from another.  If they can’t, their studies might accidentally be made up of many samples of the same few organisms, which would bias the results toward organisms that were sampled multiple times.  One example of an understory plant that presents this challenge is Canada mayflower (Maianthemum canadense).

This cute little plant can be found from the arctic to the Atlantic in a broad swath across northern North America, through the upper midwest and the iron belt states, and down the Appalachian mountains to northern Georgia.  When you’re walking in an upland New England forest during the late spring, summer, or early fall, keep an eye turned toward the understory.  You are likely to see a Canada mayflower plant.  You might see areas where many Canada mayflower plants grow in a loose patch close to the ground.  Some of the plants are just a single, teardrop-shaped leaf growing about four inches above the ground, while other plants have two or three leaves.  From late May to late June, you’ll see a crown of 10-30 tiny, white flowers on the plants with multiple leaves.  Some of the flowers will turn into reddish, round fruits by summer’s end.

If you gently dig up the base of one of these plants, you’ll find a slender root (or two) that runs horizontally into the soil.  If you keep digging carefully, you may be able to follow that slender root right over to a neighboring “plant.”  And you could go on to the next “plant,” and maybe to the next, and so on.  Eventually, some root connections break down, but they are all the same plant.  Canada mayflower has a clonal growth habit – it uses roots like other plants use twigs, to spread out leaves and capture more light.  Some clones cover more than 20 square feet; old ones can reach 30-60 years of age.

So what is an individual, and does it matter?  Maybe it doesn’t matter to a hiker just admiring the flowers.  But for a scientist trying to study plant responses to the environment, it matters a great deal.  If we want to understand how plants are reacting to acid rain, or dealing with a changing climate, we have to know where a plant begins and ends.  Our questions require us to take independent samples.  With molecular techniques, researchers can test individual stems to determine genetic identity.  But it’s expensive and time-consuming.  Our understanding of these beautiful wildflowers will therefore be limited until we discover an easy way to tell who’s who.

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