other. You can also enlarge your photos and look for details you may have missed in the field.
Tips for the Field
FILL THE FRAME When taking an image of a single track, position the camera directly above the print and fill as much of the frame as possible. This may require being on your knees and elbows, but photos taken from a standing position rarely have enough detail.
STEADY THE CAMERA Supporting the camera on a tripod is the best method of track and sign photography, because a tripod allows you to use the necessary large F-stops to capture an entire image in focus even in shaded area or low-light conditions. It is possible to take good-quality images by hand when there is adequate light. If you are hand-holding a camera, it may help to stabilize your elbows against the ground or some other object. A general rule of thumb is to use the smallest aperture possible that allows you to use a shutter speed fast enough to avoid blur. Traditionally the slowest hand-holdable shutter speed is the numerical equivalent of the focal length of the lens. Thus, if you are using a 100-mm lens, never use a shutter speed slower than 1/100th of a second.
SHADE THE TRACK Unless the sun is at a very low angle (sunrise or sunset), it is preferable to shade the track. Direct, overhead sunlight removes contrast and may create shadows that distort the shape of the footprint.
Common Poorwill tracks in shade. The penny is ¾ in. (1.9 cm) in diameter and is a useful scale you might have in your pocket.
The deeper, darker impressions in the snow are the trail of a hunting Ermine tracking down a deer mouse that left the smaller, lighter tracks grouped in fours. Photo by Jonah Evans
USE A SCALE Try to place a ruler or other object of known size in the image. In some situations, the absence of a scale can make it much more difficult to identify the track. This is especially important when recording data and documenting the presence of a rare or controversial species.
TAKE SEVERAL IMAGES The great thing about digital cameras is that taking photos is free. Take several photos of each track and vary the shutter speed, aperture, zoom, and other camera settings. When you get home you can select the best image and delete the rest. Taking a few extra photos is well worth the effort when compared to the disappointment of finding that the one photo of a track you took is blurry.
Carnivore Scent Stations
Carnivore scent stations are a fancy name for a human-made track trap. Scent stations were developed by researchers to attempt to maintain a probability of detecting an animal across locations, time, or both. One of the challenges of using tracks in research is that substrates vary, and it is easier to find tracks in some areas than in others. Thus, if few tracks are recorded in an area, this might mean that few animals inhabit the area, or it might be a result of poor tracking conditions.
Scent stations include a scent lure and either an artificial tracking surface such as sand or gypsum, or an enhanced surface obtained by raking an area or sifting local soils. Researchers place scent stations across a landscape and use visitation rates of different species to estimate a variety of parameters including relative and actual abundances. See Long et al. (2008) for a detailed presentation of methods and scientific designs using both scent stations and prepared tracking substrates without baits.
Sooted Track Plates
Sooted track plates are another method developed by researchers to equalize the probability of detecting an animal's tracks. While more difficult to set up than scent stations, they have the advantage of providing a record of the track that can be carried out of the field for further inspection. Track plates come in a variety of forms to suit different species, but the basic principle is the same: an animal is lured across a board or “plate” covered with soot, chalk, or some other powdery substance, and then a sticky paper (contact paper) catches the soot from the bottom of the foot. The resulting two-dimensional tracks can be incredibly detailed or a blur of black dust; they are also very different from the three-dimensional tracks we see in earth and snow. For that reason, we have provided here a brief guide to common tracks you might catch when you do this in California, which begins after page 30. This resource was compiled from three resources: (1) tracks caught as part of a southern Sierra Nevada carnivore monitoring program managed by Rick Truex, wildlife biologist for Sequoia National Forest, (2) the collection of William J. Zielinski and Ric Schlexer at the Redwood Sciences Laboratory of the U.S. Forest Service Pacific Southwest Research Station, and (3) several private libraries, primarily Mark Elbroch's, but with generous contributions by Preston Taylor, Casey McFarland, and Neal Wight.
Track plate methodology has been particularly refined for marten and Fisher detection. Herzog et al. (2009) developed a technique to identify individual Fishers from footprints on track plates and thereby found a noninvasive means of gathering capture-recapture data for quantifying population estimates. Slauson, Truex, and Zielinski (2008) determined that total track length (as defined in the accompanying visual) was an effective method to determine the sex of marten tracks collected on track plates in California. In the Sierra Nevada, the cutoff point is 30.75 mm—larger measurements are males, smaller are females. In the northern Humboldt region, martens are smaller, and the cutoff between the genders was 29.70 mm. Slauson and colleagues (2008) also presented a more complex equation to determine the sex of Fishers from their tracks in California: (1.046 × 13 height) + (1.011 × total length) + (0.361 × 13–14 width). Refer to the illustration to see how to measure these variables. The cutoff point for this equation is 62.17; larger numbers are males, and smaller are females.
Measurements used in determining gender of marten, and one of the measurements needed to determine gender of Fisher tracks as described by Slauson et al. (2008). Note track is not to scale.
Additional measurements useful in determining gender in Fisher tracks on soot plates. For this animal, we calculated 60.93, or female. As described in Slauson et al. (2008). Track is to scale.
For additional information on track plates, see Long et al., Noninvasive Survey Methods for Carnivores (2008), Zielinski and Kucera, American Marten, Fisher, Lynx and Wolverine: Survey Methods for their Detection (1996), and Halfpenny et al., Track Plates for Mammals—A How-To Manual and Aid to Footprint Identification (2010).
Camera Traps
There has been an abundance of relatively cheap remote cameras flooding the commercial market in recent years. Hunters often use them to monitor trails, so that they know exactly when and where large bucks prowl. Researchers use them to document the presence of numerous species, especially rare and elusive ones.
Camera traps are a wonderful complement to traditional tracking skills. They provide a visual confirmation to our interpretations, and provide a way to learn more about tracking. If there is a mystery path created by some animal in your backyard, perhaps a well-placed camera trap can teach you what species created it.
DIGITAL VERSUS FILM The primary disadvantages of digital remote cameras remain shorter battery life and shutter delay, but these are being resolved with each new generation of cameras. The benefits of not needing to pay for film developing, as well as the ability to instantly see photos (and make adjustments as needed), make digital cameras a better choice for most situations.
SOOTED
