What moose scats tell us...
Copyright © John A. Vucetich — All rights reserved
Moose pellets are pretty easy to find in the forest, and they contain clues about what moose eat.
Here’s how we learn what a moose has been eating. First we prepare the scats in this way: drying the scat, grinding it up into little fragments, putting it through a series of sieves (so you can examine scat fragments of a certain size), and bleaching it with acids (so there is less color, which is distracting in the identification process).
Once prepared the pellets can be examined under a low-power microscope.
Moose make two basic kinds of scat. During the summer, moose make what look like cow pies. During the winter, moose make what we call pellet piles. Our work focuses on the collection and analysis of winter pellets.
Image to be added soon.
Under a microscope the pellet fragments look like this...
These ground-up fragments from moose pellets are plant parts. More specifically, each fragment represents several dozen plant cells from twigs and needles. Each species’ cells have a distinctive appearance.
Aspen
Cedar
Balsam fir
From each pellet pile that we sample in the forest, we examine 100 fragments. Each year we collect 45 pellet piles from 15 different locations throughout Isle Royale.
From the analysis of these samples, we know that during winter moose eat about equal amounts of balsam fir and deciduous plants (e.g., aspen, hazel, dogwood). Also, about 15% of their diet is cedar.
Winter diet of an average moose
By conducting large-scale plant surveys in the area where we collect pellet-piles, we also know something about the relative abundance of these winter food types.
Much can be learned by comparing the diet with what is available in the environment. For example, notice that cedar is about three times more common in the diet than it is in the environment. This means that moose prefer cedar.
However, deciduous twigs are more common in the environment than in the diet. This means that when moose find a deciduous twig they often pass it up. They prefer this food type less than cedar.
Relative abundance of winter food types on Isle Royale
Image to be added soon.
Image to be added soon.
Image to be added soon.