23 August 2023

The white-tailed deer population in the City of Pittsburgh has been so high for so long that most people think the browse line in our parks is normal, but the light-gap you see under the trees above is not normal in a balanced forest. It’s a sign of deer overpopulation. Here’s what a browse line is and how deer maintain it.

Browse line: A phenomenon that occurs when herbivores consume all of the vegetation in the woods between the ground and the level of their highest reach. A clearly visible line is formed between the leafed and the leafless areas.

— paraphrased from Blue Jay Barrens: Fallen Trees and Browse lines, May 2011

Is the browse line hard to recognize in the photo above? Here’s an extreme example.

This eye-level view of the Grande Allée of horse chestnut trees at the Tuileries in Paris is a man-made browse line in which gardeners trim the trees and clear the ground to maintain an opening beneath the trees at uniform height. Nothing is growing between the ground and the trimmed height.

An individual deer browsing the ground and lower branches of trees does not create the browse line. It’s the cumulative effect of too many deer eating at the same location over and over.

Last Friday I watched two 8-point bucks, antlers in velvet, maintain the browse line next to the Upper Trail at Schenley Park. The current browse line, seen in the video, is that clear view straight through the woods to the cars passing on the road beyond.

In the video the bucks eat herbaceous stems and leaves on the ground, then switch to twigs, leaves and stems of trees. About halfway in, the buck on the right stands on his hind legs to reach the lowest branches. The buck on the left wrestles with a tree to yank off the branches. Deer only have lower teeth so they can’t sharply bite off a branch like a beaver would.

In late August, when forage should be quite plentiful, these bucks are forced to eat their own cover and what little remains of the edible plants.

p.s. Here’s what the forest would look like if there was no browse line.

(photos by Kate St. John)

13 August 2023

In the city of Pittsburgh there are so many white-tailed deer that it’s easy to see them in August. The bucks are eating, eating, eating to bulk up. The does are hanging out with their adolescent fawns in this brief period between birthing and mating. It’s the calm before the rut.

Last Friday morning I found eight deer resting in dappled shade in Schenley Park. My cellphone photos don’t do them justice except for this: The photos show how hard it is to notice deer that are lying down and not moving.

A few of them moved, however, grooming to shed their chestnut brown summer coats for gray-brown winter pelage. The photo above shows four bucks with antlers in velvet, each with a different point count: 4-point, 6-point, 7-point and 8-point.

Two does and two fawns rested a short distance from the males. The fawns gave the group away. They did not hold still for long. (The second doe is not in the photo.)

One week earlier it was impossible not to see this six-point buck browsing the hillside right next to the Lower Trail.

He’s leaving a lot of greenery behind but the leaves he’s not eating are unpalatable invasive aliens called goutweed. The buck is nosing through them to re-browse the deer-food plants hidden below the goutweed. Those food plants won’t recover this late in the season. All the food will be gone and he won’t be back to this spot.

In August the days are still longer than the nights and deer hormones are not surging yet but it’s only a matter of time and the Equinox before their sedate demeanor ends. According to the PA Game Commission, after 12 weeks of rut excitement from mid October through early January:

• 98% of the mature does will have bred
• 40% of the fawns will have bred at only 6-7 months old (city/suburb phenomenon)
• 85% of the pregnancies will result in twins or triplets, some with different fathers.

It’s calm now before the storm.

Schenley Park suffers from its overabundant deer population. See this article for more information: The Forest Lives in Mortal Fear of Its Deer.

A NOTE TO COMMENTERS: Some interesting threads have developed in the comments with new readers weighing. Please note that comments on this blog are moderated and may be edited for clarity. Comments that could inflame others will be edited or deleted.

(photos by Kate St. John)