The Twig-Age method was designed by Dr. Donald Waller of the University of Wisconsin-Madison. It is a simple method that allows us to estimate the browsing impacts that deer are having in a forest’s understory. This method involves measuring the height of a sapling in centimeters and aging two separate twigs using terminal bud-scale scars to differentiate between years.
Click here to read Dr. Waller’s original research paper describing the Twig-Age method.
The figure below is from the original research paper and applies to a field site in the northern Upper Peninsula of Michigan. This figure shows how the method has been applied to three species of maple over the course of three years. We can see here that the Twig-Age method is a more sensitive indicator of deer presence and differences among sapling species than seedling height is on its own.