The hardest thing to notice in Nature is the date of an absence. When did the last junco leave in the spring? When did the last groundhog go into hibernation?
Right now eastern chipmunks (Tamias striatus) are busy gathering nuts to store in their underground burrows for the winter. As the season changes and temperatures drop they will disappear into their burrows to enter torpor, sleeping off and on through the winter.
The warm winters of climate change can fool them into not entering torpor but the result is deadly. Only 10% survive. Find out why in this vintage blog:
Meanwhile I will hope our chipmunks disappear and will try to figure when they do it.
Here’s how I notice an absence: I write down every day when I do see them and then scan my notes for days when I’ve not logged them anymore.
(photo from Wikimedia Commons; click on the link to see the original)
In western Pennsylvania, where we have a high deer population, gardeners have learned from experience that white-tailed deer will eat some plants and not others. They heavily browse their favorites to the point of killing them but leave others untouched, even plants in the same genus.
In Schenley and Frick Parks you can look straight through the forest if you duck your head below four feet high. In Schenley Park the ground is often bare and most plants in that four-foot zone are gone. But one flower, wingstem (Verbesina alternifolia), is doing just fine in the city parks.
The absence of cover from the ground to 4 – 5 feet is called a browseline (below) and is evidence of an overpopulation of white-tailed deer.
According to this KDKA report, the deer population in Schenley Park is estimated at 80-150, which roughly equates to 100-200 deer per square mile. A healthy population in a balanced forest would be 20-30 deer per square mile, so any plant that survives in the Pittsburgh’s city parks is something that deer don’t eat.
At this time of year the birds are not singing but you often hear a “chip” note in the woods. It’s not the sound of a bird but instead a chipmunk, making the noise that puts “chip” in his name.
“Chip” is warning sound that means Danger From the Ground. Chip Chip Chip Chip, the speaker is warning of a ground-based predator — a cat, raccoon, snake, etc.
Chipmunks “chip” at different speeds, even during the same chipping session, as seen in the 4.5 minute video below. The tonal quality and variable speed give us a hint that it’s a chipmunk speaking, not a bird.
The second most common chipmunk sound is another warning.
“Tock” means Danger From The Air — a clue that birders should look for a raptor. Tock Tock Tock Tock. Listen and learn in this vintage article.
I had never seen the word “synanthrope” until I found it attached to this photo.
House sparrows are synanthropes. So are pigeons.
A synanthrope (syn-anthrope) [from Greek: syn-anthrope: syn=”together with” + anthropos=”man”] is a wild animal or plant that lives near, and benefits from, an association with humans and the somewhat artificial habitats that people create around themselves.
Two local mammals may be recent synanthropes, formerly shunning humans but now benefiting from our habitat.
Squirrels love our birdseed and shelter (attics).
White-tailed deer (Odocoileus virginianus) prefer forest edges next to open areas, a landscape often created by humans. Have deer become synanthropes?
p.s. (*) Merriam-Webster explains that the word was introduced by botanist Theodor von Heldreich at a botanical conference in Paris, 16-24 August 1878, making its first-ever use almost exactly 144 years ago.
Twelve years have passed. According to deer experts “Urban deer can live for 10 years; the deer population, if unchecked, doubles about every two years.” Schenley Park now has as much as 64 times the number of deer we had in 2010. This is truly unsustainable, even for the deer themselves.
Schenley’s deer have completely consumed all the good food plants and are starting to nibble the poisonous ones. The browse line is painfully obvious. In the process deer have eradicated their favorite plants from Schenley Park.
Orange jewelweed and yellow jewelweed provide nectar for hummingbirds and bumblebees and are a favored food of deer.
Both jewelweeds were prolific in Schenley Park as recently as four years ago.
But this year all the accessible plants have been eaten down to bare stems. The only ones that flower are those in spots unreachable by deer — on extremely steep slopes or hidden among thick cattails in Panther Hollow Lake.
Jewelweeds are annuals that must re-seed every year but no seeds are produced in this deer-browsed landscape. Impatiens will disappear from Schenley Park when the seed bank is exhausted.
False Solomon’s seal used to grow throughout Schenley Park and it carpeted the ground in an area near the Bridle Trail. All of it has been eaten to the ground since 2014. Here’s what it looked like eight years ago.
White wood asters used to bloom in Schenley’s woods. Not anymore. Here’s what they looked like in 2013.
Eradicated plants are indirect evidence of too many deer in Schenley Park. Direct evidence is their visibility every day.
A sustainably-sized deer herd would hide in the underbrush while sleeping during the day, but the browse line in Schenley is so severe there is no cover for them. The large herd has coped by becoming accustomed to people and leashed dogs.
I stood near this group of three deer on Sunday 21 August using my snapshot camera zoomed to 90mm (approximately 2x). This 8-point buck did not care that I was there.
Yews are popular landscaping shrubs but they don’t last long in the face of deer overpopulation.
All yew species are toxic to some degree, but our native Taxus canadensis is less toxic than others and was used medicinally. Deer don’t read the warning labels. They love yew.
Every night they creep up behind Carnegie Museum and browse the yews along the driveway to the parking garage. They nip off the small branches and eat all the leaves. The shrubs struggle to grow new leaves for photosynthesis before the deer return.
Deer have killed the yews closest to the sidewalk (dead twigs), overbrowsed the middle shrubs (green knobs), and cannot yet reach the tallest branches. But they are eating their way there.
Don’t assume their love stops with yew. There are more delectables in Schenley Park that they adore. Soon we’ll explore more.