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A "circus of chipmunks" proposed as a venery term |
To anyone spending any time outside, this has been the year
of the chipmunk. Yards and gardens are punctuated by holes about the size of a
silver dollar. Under bird feeders, along the Rail Trail, these striped critters
are always scurrying, scurrying, scurrying. The name “chipmunk” is derived from
Native American “jidmoonh,” from the Odawa tribes that lived in the Great Lakes
region. The Anglicized “chip” refers to the high-pitched “chip-chip-chip” alarm
call made when a possible predator (fox, cat, dog, human) is seen.
Chipmunks are rodents, albeit cuter than rats. Within the
species family Sciuridae (squirrel) there is a division between tree squirrels
and ground squirrels, the latter including not just chipmunks but also prairie
dogs and groundhogs. Massachusetts is host to the Eastern chipmunk. Out west
there are 23 chipmunk species – all not to different visually from the Eastern –
but genetically different enough to not interbreed. There is one more species,
the Siberian chipmunk, in northeast Asia, which has become an invasive species
in western Europe via escapees from the pet trade. There is a strong
resemblance across all of the species: brown, striped, furry tail and cheek
pouches in which to stash food so that it can be brought back to the nest.
Eat and be eaten: Chipmunks are omnivorous. Their diet is primarily
seeds, nuts, berries, fruits and the tender plant shoots and buds, but also
insects, worms and the occasional bird egg. Same for squirrels. Chipmunks can
be garden pests and wreak havoc on bulb plantings. Unlike squirrels, which
scatter-bury acorns for digging up later, chipmunks bring nuts and seeds back
to their nests. There, along the 10-20 feet of tunneling, they will have a larder
of food set aside for winter consumption. The burrows extend below the frost
line.
Chipmunks utilize an
intermittent hibernating state. From a body temperature close to 100F degrees
and a heart rate of 200-300 beats per minute, body temperature approaches 40F
degrees and heart rate to 10 bpm. Every few days the chipmunks rewarm to normal
temperature, become active, eat, and then cool down again. The net effect is
less food needed to survive winter, and for the females, more body fat reserves
for a successful spring pregnancy.
As to what eats chipmunks, think hawks, feral and pet cats,
weasels, foxes, coyotes, snakes… As chipmunks’ diurnal lifestyle can extend to
near-dawn and -dusk hours, they can also fall prey to owls. Great blue herons
have been known to stalk near bird feeders for the foraging chipmunk, oft times
dipping the struggling animal into a birdbath or other water before swallowing
it whole.
As to why this was the year of the chipmunk, last year was
the year of the acorn. Last year’s abundance of food carried over into this year,
allowing for larger litters and better survival from the spring and summer
pregnancies. The young, who at birth are hairless, blind and about the size of
a small bumblebee, emerge from the burrow after about six weeks and strike out
on their own two weeks later. With the exception of mating, chipmunks leave
solitary lives; males have no part in raising infants. In normal times,
population density is roughly 1-2 per acre. In good years, this can increase five-fold.
The abundance of acorns in 2019 occurred because oaks do not
produce the same yield every year. Evolution research posits that a same-sized
crop every year will support stable populations of acorn eaters, which includes
chipmunks, squirrels, woodchucks, skunks, turkeys and deer. By producing a
large crop every other or third year, populations of seed-eaters are curtailed,
and a greater portion of seeds will remain uneaten in good years. The key to
this strategy is coordination—it works only if trees of the same species do it
at the same time. How tree species coordinate is still somewhat of a mystery,
but this synchronicity is probably aided by some combination of chemical
signals passed through the air or through underground root/fungal connections. Regardless,
this year’s chipmunk (and squirrel) population explosions were newsworthy across
New England.
We say a “pride of lions, gaggle of geese, school of fish,”
but why? As it turns out, social standing among Medieval European nobility
required that men knew their venery – the proper naming of groups of animals –
else be taken for crass and uneducated. Collections of these “terms of venery”
culminated in a master list compiled in The Book of St. Albans, in 1486. Thus,
we have a “colony of ants, a pack of wolves, a murder of crows,” and so on. A
group of squirrels is a scurry. Sadly, a group of chipmunks is also a scurry,
which lacks the alliterative appeal of a “scurry of squirrels.” Chipmunks are
not native to Europe, which perhaps explains the lack of a better venery term.