Editing Virginia opossum (section)

===Tracks===
{{more citations needed section|date=March 2018}}
{{Multiple image
| image1            = Opossum and vole tracks in mud.JPG
| caption1          = Opossum tracks (photo center) in mud: Left-fore print appears on left center of photo, right-hind print appears right center. The small, circular tracks at bottom center of photo were made by a meadow vole. The yellow ruler (top) is in inches.
| image2            = Pacing diagram opossum.png
| caption2          = Pacing diagram for Virginia opossum - key: rectangles represent hind tracks, ellipses are fore tracks, left tracks are red, right are green. (a) the position of the four feet frozen in mid-pace. (b) the opossum brings right fore and hind feet forward. (c) the opossum brings left fore and hind feet forward. One grid square represents one square inch.
| total_width       = 350
}}
Virginia opossum tracks generally show five finger-like toes in both the fore and hind prints.<ref name=Krause>Krause, William J.; Krause, Winifred A. (2006).[https://web.missouri.edu/~krausew/Histology/Home_files/opossum.pdf  ''The Opossum: Its Amazing Story''] {{Webarchive|url=https://web.archive.org/web/20121211214644/https://web.missouri.edu/~krausew/Histology/Home_files/opossum.pdf |date=2012-12-11 }}. Department of Pathology and Anatomical Sciences, School of Medicine, University of Missouri, Columbia, Missouri. 80 pages.</ref> The hind tracks are unusual and distinctive due to the opossum's opposable [[thumb]], which generally prints at an angle of 90° or greater to the other fingers (sometimes near 180°). Individual adult tracks generally measure 1.9 in long by 2.0&nbsp;in wide (4.8 × 5.1&nbsp;cm) for the fore prints and 2.5 in long by 2.3 in wide (6.4 × 5.7&nbsp;cm) for the hind prints. Opossums have claws on all fingers fore and hind except on the two thumbs (in the photograph, claw marks show as small holes just beyond the tip of each finger); these generally show in the tracks. In a soft medium, such as the mud in this photograph, the foot pads clearly show (these are the deep, darker areas where the fingers and toes meet the rest of the hand or foot, which have been filled with plant debris by wind due to the advanced age of the tracks).

The tracks in the photograph were made while the opossum was walking with its typical pacing [[gait]]. The four aligned toes on the hind print show the approximate direction of travel.

In a pacing gait, the limbs on one side of the body are moved simultaneously, just prior to moving both limbs on the other side of the body. This is illustrated in the pacing diagram, which explains why the left-fore and right-hind tracks are generally found together (and vice versa). If the opossum was not walking (perhaps running), the prints would fall in a different pattern. Other animals that generally employ a pacing gait are [[raccoon]]s, [[bear]]s, [[skunk]]s, [[badger]]s, [[woodchuck]]s, [[porcupine]]s, and [[beaver]]s.

When pacing, the opossum's 'stride' generally measures from 7 to 10&nbsp;in, or 18 to 25&nbsp;cm (in the pacing diagram the stride is 8.5&nbsp;in, where one grid square is equal to 1 in<sup>2</sup>). To determine the stride of a pacing gait, measure from the tip (just beyond the fingers or toes in the direction of travel, disregarding claw marks) of one set of fore/hind tracks to the tip of the next set. By taking careful stride and track-size measurements, one can usually determine what species of animal created a set of tracks, even when individual track details are vague or obscured.