Field Guide to Animal Tracks and Scat of California. Lawrence Mark Elbroch

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СКАЧАТЬ Three radically different sets of tracks, all made by the same species.

      When loose windblown sand has accumulated in a footprint that was made in damp or wet sand, it is sometimes possible to carefully blow away the loose sand to reveal the features of the footprint underneath. Footprints in mud may in fact be preserved for quite a long time underneath a layer of loose sand or leaf litter. When leaves are covering the track, or even when the animal has stepped on top of leaves, they can be carefully removed to reveal the track. When studying tracks in loose sand or other difficult substrates, you should try to visualize the shape of the footprint before the sand grains, snow, etc., slid together to obliterate the welldefined features.

      What Else Can Tracks Tell Us?

      While species can be identified by characteristic features, there also exist individual variations within a species. These variations make it possible for an expert tracker to determine the sex as well as estimate an animal's approximate age, size, and mass. A tracker may also be able to identify a specific individual by its footprint. For example, Stander et al. (1997) tested these abilities in four Ju/'huan trackers in Namibia, and they correctly answered 557 of 569 questions. The Ju/'huan team correctly identified the species that made the track in 100 percent of tests. They correctly identified the relative ages of Cheetahs and Leopards (that is, cub, juvenile, young adult, adult) 100 percent of the time in 30 tests, but the relative age of African Lions only 34 out of 39 times (87 percent). Their mistakes were all in calling a subadult animal a full adult. They correctly identified the sex of Lions in 100 percent of 39 tests, Cheetahs in 12 of 13 tests, and Leopards in 16 of 17 tests. It is also in principle possible to identify an individual animal from its track. It may have a unique way of walking or a particular habit that distinguishes it from other individuals. The Ju/'huan trackers correctly identified the individual Lion, Leopard, or Cheetah by its tracks in 30 of 32 tests (96.4 percent).

      Determining the Gender of an Animal

      Many mammal species show characteristic sexual dimorphism, meaning that one sex is significantly larger and heavier than the other. In the case of California's mammals, it is likely to be the male that is larger. Sexual dimorphism is especially prevalent and blatant in California's carnivore species, including canids, felids, pinnipeds, mustelids, and bears, where adult males are always the larger sex. In species where dimorphism is especially pronounced, such as Cougars and Fishers, the tracks and trails of adult males and females can quite easily be differentiated. In other species, such as river otters and skunks, sexual dimorphism is minimal, and therefore track size alone is not as useful a character in differentiating males from females.

      On the left are the tracks of a mature male Fisher, and on the right the much smaller tracks of an adult female.

      What follows are some useful track characters to consider in determining the sex of select carnivore species. With considerable aid from numerous African trackers who have determined how to sex Leopard and Lion tracks, one of us (Mark Elbroch, unpublished data) has developed this list to aid researchers in identifying the sex of Cougars from their tracks. He has identified the sex and relative age correctly in 100 percent of trials with wild Cougars (n = 28), where the animal was subsequently caught as part of larger research efforts to verify the interpretation. The ability to reliably determine the sex of Cougars from their tracks is widespread in Cougar houndsmen that hunt them for sport, with depredation permits, or for a living, and this skill would be a valuable one to document further and quantify.

      When studying the following track characters, you should build a case for a particular gender; that is, determine how many characters indicate female and how many male. Sometimes a track yields conflicting evidence, and the gender cannot be determined with certainty.

      The left front and hind (lower right) tracks of a young adult male Cougar, approximately three years of age, which means he still had a bit more growing to do.

      Track features: (1) Tracks of adult male Cougars are larger than those of adult females, and the areas of the metacarpal and metatarsal pads are also larger. Measure the width of the metatarsal pads (palm) in the hind track, and use a cutoff of 50 mm to determine sex. This is a very reliable tool in determining the sex of Cougars, especially when the other characters described here provide conflicting evidence. This method has also been used by other researchers (Shaw 1979; García et al. 2010). Only the odd female will approach this cutoff, but adult male palm pads typically start at 53 mm wide and can be much larger. García et al. (2010) also report that in captive Cougars they used to study tracks, the “shape of the heel pad in males can be described as relatively narrow in the middle, while that of females is more extended in this zone.” (2) The toes of males in both front and hind tracks are blockier than females; the toes of females are more slender and more teardrop-shaped. (3) The front tracks of males are almost always wider than long and are at least as wide as long; the front tracks of females are often narrower than long or as wide as long. (4) There is a smaller area of negative space between the metacarpal pads and the toes in the front tracks of males than those of females. It is as if the palm fills the track more in male tracks than in female ones. (5) The negative space between the metatarsal pads and the toes in the hind tracks of males is much smaller than that found in hind tracks of females; typically male palm pads nearly touch the toes, and in females there is a significant rectangular gap. (6) There is less space between the toes of the hind tracks in males than in females. (7) The hind track of males is generally narrower than long, but not to the degree that the hind tracks of females are.

      Front and hind (above) tracks of an adult female Cougar, with penny for scale.

      Trail characteristics: (1) The strides of females (measured from left hind track to left hind track, or right to right) average about 36 in. and the strides of males about 40 in. (Boone Smith, personal communication). (2) The width of walking trails is much wider in males than in females.

      Elbroch has applied these same characters to other species, including Gray Foxes, Ringtails, Bobcats, American Minks, and Fishers. Preliminary results are very positive yet not so much so that we can say with certainty that they work all of the time. We encourage you to start gathering the data needed to develop these skills further, and the track and trail measurements from known-sex animals, so that we can begin to compile useful parameters for species in North America.

      In hooved species, the relative weight difference between an individual animal's front and hind ends is proportional to the discrepancy in size between its front and hind tracks. In Bighorn Sheep and Mule Deer, where males are adorned with large horns or antlers, their front ends are much larger than their hind ends to support this additional weight; their feet and footprints reflect this discrepancy, and their front tracks are much larger than their hind ones. Female Bighorn Sheep and Mule Deer also have larger front tracks than hind tracks, but only slightly larger, and their front and hind tracks are much more similar in size. Females of both species carry their weight more evenly distributed between their front and hind ends than do their male counterparts. It is the larger difference between the length—and more often the width—of front and hind tracks of males that helps trackers determine an animal's sex. That difference in size between front and hind tracks of females is much smaller.

      Carefully note the large disparity between the length and width of the front track above and hind track below in a mature Mule Deer buck.

      The sexes may also be distinguished by association. The track of an adult in close association with a juvenile is probably that of a female with her young. Nursery СКАЧАТЬ