Finger-Painting: Track Tubing for Small Mammals
Text and drawings by Tiffany Shao
During the month of October 2006, WildMetro
experimented with a new technique to monitor small mammal populations,
called track tubing. Track tubes can give us information on what species
are found in the area and the relative abundance of each species. Unlike
Sherman live traps, with track tubes we can work in colder weather and
with 0% mortality because the animals can come and go as they please from
the tubes. A track tube is composed of a piece of contact paper lying
inside a tube made of pieces of gutter. Pieces of felt soaked with black
ink (made from charcoal and mineral oil) are placed on both ends of the
tubes, and bait (peanuts and sunflower seeds) is positioned in the middle
of the contact paper. Small mammals are attracted to the bait and step
onto the inkpad, leaving their tracks on the paper as they
head toward the food. We can then collect the contact paper and study
the tracks, identifying what animals are in the area. We conducted a trial
run, which yielded interesting results.
We placed track tubes in two areas of Marshlands Conservancy, located in Rye, NY. Both areas are overgrown with invasive plant species, such as multiflora rose, porcelain berry, and Japanese knotweed. The Conservancy has plans to remove these invasive plants in one area in February 2007, and the other area will not be manipulated. In the spring, we will reset our track tubes to examine how the removal of these invasive plant species has affected the small mammal community. How will altering the environment affect the populations? Perhaps there will be a decline in one species and an increase in another. Maybe the whole small mammal population will decline. Even though these plant species are invasive, they provide habitat for many creatures, some of which managers would like to protect. Research on the relationships between a species and its habitat is therefore very important and these results will affect future management decisions at Marshlands Conservancy.
Our track tubes detected a variety of species of small mammals. The tracks were predominantly those of white-footed mice (Peromyscus leucopus), though we also found tracks from raccoons (Procyon lotor), gray squirrels (Sciurus carolinensis), feral cats (Felis catus), and one red-backed vole (Clethrionomys gapperi). The composition of the small mammal communities in each area was comparable.
In the area to be manipulated, 52% of the tracks were white-footed mice , and in the control area, 59%; white footed mouse tracks were dominant compared to the other species. Twenty six percent of all tracks were raccoon tracks. However these are probably from only two or three different animals moving from one tube to another. Larger mammals like raccoons are able to move across a transect easily, making it difficult to estimate exactly how many of them there are. In addition to mice and raccoons, 10% were gray squirrel tracks and 8% were feral cat tracks.
We also set up a grid of track tubes in open
meadow habitat at Marshlands Conservancy during November 2006. Unlike
the survey in October, the data from the meadow showed a fairly low abundance
of animals. These meadow tubes collected a higher number of raccoon tracks
than white-footed mouse tracks, and reported the presence of one gray
squirrel. Interestingly, we did observe several distinctive short-tailed
shrew (Blarina brevicauda) prints, which were absent from the invasive
species management area.