Carnivora Study Guide

ORDER CARNIVORA - CARNIVORES As the ordinal name implies, members of this order are primarily designed for eating meat. This is best reflected is the structure of their teeth. The fourth (last) upper premolar and first lower molar are modified to act as a shears for cutting off chunks of meat. These teeth are known as the carnassials and reside in the area of the jaw that is capable of generating the greatest force. Most members of Carnivora are actually ominvorous and some, such as the pandas, are completely herbivorous. The extent to which the carnassials are developed is a good clue as to how important meat is in the diet of a particular species. Carnivores also have well-developed canine teeth that are used for gripping prey, but these teeth have other applications and are still prominent in the omnivorous and herbivorous members of the group. The claws are always well-developed, but not necessarily sharp. There are usually five toes on each foot although in some families, one toe may be vestigial or completely lost. Some members are plantigrade, some are digitigrade, and some are a combination of both. Carnivores are also generalized as having acute eyesight, hearing, and/or a good sense of smell to help them locate prey. The eyes are positioned such that they are facing forward on the head. This allows for extensive overlap in the field of view for each eye, resulting in excellent depth perception. Species that actively hunt are usually fast, muscular, and agile. The baculum is well-developed. The brain is relatively large and carnivores are considered to be among the most intelligent of the mammals. This is a large order with many diverse forms, and many characteristics do not hold true for every member of the order. Similar Species: For the study skins, there is no one key characteristic that will tell you that what you are looking at is a carnivore because there is so much variation present in this order. Look in the accounts for specific families, genera, and species below for ways to differentiate them from other orders that may resemble them. Carnivore skulls can usually be distinguished from other mammals by the carnassial teeth and large canines. Remember that not every skull with pointy teeth is a carnivore. The opossum, insectivores, and bats also have pointed teeth. You can separate carnivore skulls from these other orders as follows: Opossum: 1.) The opossum lacks auditory bullae (1A); these structures are usually prevalent in carnivores (1B). 2.) The opossum has 5 pairs of upper incisors; carnivores only have 3 pairs of upper incisors. Opossum Skull Carnivore Skull Insectivores: 1.) The shrews can easily by recognized by their lack of zygomata (1A); these structures are prominent on all carnivore skulls (2A). Shrews also lack auditory bullae, a feature that is present (although not always conspicuous) on all carnivore skulls. 2.) The moles can be a bit more tricky since they have zygomatic arches and auditory bullae. However, in moles, the first two upper teeth are longer and sharper than the subsequent teeth. These two incisors are located immediately next to one another and look like the enlarged canines in carnivores (1A). However, true carnivores have six incisors (2B) between the two upper canine teeth (2A), and these incisors are much smaller than the canines. The weasels are the only carnivores with skulls small enough to be confused with the mole, but weasels have a much shorter rostrum (4B) and the last upper molar is dumbell-shaped (3B) and curved inward on an angle; the mole has a long rostrum (4A) and the last molar is about the same size and shape as the previous tooth (3A). 1B  1A  1A  2A  Left: Mole skulls Right: Weasel skulls Bats: 1.) Bats have a large gap between the upper incisors (1A); these incisors are closer together in carnivores (1B). 2.) Just as with the insectivores, bat skulls are very small and the only carnivore skull they approach in size is that of the least weasel. The last upper molar in bats is similar to the preceding tooth (2A) and is not dumb-bell shaped as in the weasels (2B). Bat Skull Weasel Skull 1A  2A  2B  3B  3A  4A  4B  1A  1B  2B  2A  Family Canidae - Wolves, Dogs, Foxes Canids have a general body plan designed for long-distance running (although some species have since developed adaptations for other hunting techniques). They possess incredible endurance and often catch their prey by exhausting it. The legs are fairly long and the feet digitigrade. There are four toes on each hind foot and five toes on each front foot. The first (innermost) toe on the front foot is located higher up and is greatly reduced in size. This toe is referred to as a dew claw and it plays an important role in helping the animal to maneuver at high speeds. The claws on all the toes are non-retractile and blunt; they provide traction while running, but are not important for subduing prey. The tail is bushy and moderate in length. The ears are large and pointed and the snout long and slender. Similar Species: All of the Wisconsin canids are medium to large-sized carnivores. They are likely to be confused only with other carnivores. The presence of only four toes on the hind feet separates them from all other members of the order except for cats. The tail can be used to separate them from the Wisconsin felids: wild canids have bushy tails while felids do not. In addition, the lynxes have very short tails. Skull The canid skull is long and slender with a long rostrum. The braincase is narrow. The carnassial teeth are well-developed, but the shearing edge is only present on the front half of the tooth; the posterior edge of the tooth is flat and adapted for crushing bones. There are two pairs of upper molars located posterior to the carnassials. The last upper molar is slightly smaller than the adjacent molar. The upper palate terminates at the last molar. Dental Formula: I: 3/3 C: 1/1 P: 4/4 M: 2/3 = 42 Similar Species: the canid skull can be differentiated from the bear and raccoon by the well-developed carnassial teeth (these are absent in bears and raccoons). Felids have a much shorter rostrum and a single molar behind the upper carnassials (2A) while the canids have a longer rostrum and two molars behind the upper carnassials (1A). Most of the mustelids and skunks have a much shorter and broader rostrum. The fisher and marten have the most dog-like skulls in the group, and as in most of the other mustelids, the last upper molar is nearly the size of the previous one, dumb-bell or 8-shaped, and turned so that it forms a 90° angle with the previous molar (3A). The opossum skull may be mistaken for a fox skull. Look in the account for the order to separate the opossum from the Carnivora. Coyote, Canis latrans Specimen The coyote is a medium-sized canid with long legs and small feet. The muzzle is narrow. The fur is rather long, buff to yellowish gray with long, black guard hairs intermixed. The tip of the tail is blackish. 1A  2A  3A  Similar Species: The gray fox is smaller with a different color pattern that includes bright orange fur on the sides. The coyote is most likely to be confused with the wolf. The wolf is larger and has longer legs with very large feet. Size comparison of study skins of wolf (top) and coyote (bottom). Skull The skull is as described for the family. The braincase has a median sagittal crest. The canine teeth extend below the mental foramina of the dentaries. The upper incisors are lobed. Similar Species: The foxes have smaller skulls with the temporal ridges converging near the posterior edge of the braincase (1B) such that the sagittal crest is absent or very short; in the coyote the ridges converge in the interorbital area (1A) so that the sagittal crest covers the entire braincase. In addition, the upper incisors of Canis are lobed (2A); in the foxes, the lobes on the upper incisors are inconspicuous (2B). The wolf skull is very similar to the coyote, but is much larger with a relatively broader rostrum. In the wolf, the canine teeth fall above a line drawn through the anterior mental foramina. 1A  1B  2A  2B  Wolf, Canis lupus Specimen The wolf looks like a larger version of the coyote, weighing about twice as much. The legs are very long and the feet are large. The muzzle is broader than in the coyote. The fur is usually grayish, yellowish, or brownish with long black guard hairs intermixed. Color variants including entirely black and entirely white individuals occur, but are rare in Wisconsin. Size comparison between the coyote (left) and wolf (right) skulls; also note the broader rostrum of the wolf skull. Coyote skull (left) and wolf skull (right) with a dotted line passing through the anterior mental foramina (indicated by arrows on coyote skull). Note whether the canines fall above or below the line. Similar Species: Because of its size, the wolf is likely to be confused only with the coyote. See the account for the coyote for distinguishing characteristics. Skull The skull is massive with a rostrum that is broader than in the coyote. The canine teeth fall above a line drawn through the anterior mental foramina. The upper incisors are lobed. The sagittal crest is very prominent in older animals. Similar Species: The coyote is the only other canid with a skull even close in size to the wolf. See the account for the coyote for distinguishing characteristics. Red Fox, Vulpes vulpes Specimen The red fox is a small canid about the size of a large house cat (9-13 lbs). The tail is long and bushy with a white tip. The general color is reddish-orange above and whitish below. The backs of the ears and lower parts of the legs are black. Color variants occur, some of which may look more like a gray fox than a typical red fox. Even in these variants, the tail tip is always white. Similar Species: In the normal color pattern, no other animal is likely to be confused with the red fox. In certain color mutations, it may resemble the gray fox, but can always be separated by the white tip on the tail (black in the gray fox). The foxes are much smaller than both the coyote and the wolf and have different color patterns. Skull The red fox skull is slightly less slender than in Canis. The rostrum is narrow and delicate, and the brain case somewhat inflated. The temporal ridges are not as prominent as in the gray fox, but are still visible. They converge gradually and meet at the posterior end of the brain case, forming a V-shaped pattern. Because the ridges do not meet until the back of the skull, the sagittal crest is either lacking or extremely short. The upper incisors may be weakly lobed, but not as prevalently as in Canis. Similar Species: The skull can be distinguished from the coyote by the traits specified under the account for that species. It differs from the gray fox by the V-shaped pattern formed by the temporal ridges (1A); in the gray fox, the temporal ridges converge in a U-shaped pattern (1B). 1A  1B  G ray Fox, Urocyon cinereoargenteus Specimen Similar in size and general appearance to the red fox, but with a different color pattern: grizzled gray above, bright orange on the sides, and whitish below. A black stripe runs the entire length of the tail on its upper side, terminating at the black tail tip. The backs of the ears are orange. Similar Species: See account for red fox and coyote. Skull The temporal ridges converge abruptly near the end of the braincase, forming a U-shaped pattern. The upper incisors are unlobed. The skull is otherwise much like that of the red fox. Similar Species: See account for red fox. Family Ursidae - Bears Bears are large, stocky carnivores with a short tail. There are five toes on each foot. Bears are plantigrade with the hind foot somewhat resembling that of a human. The ears are short and rounded and the eyes small. With the exception of the polar bear, ursids are largely omnivorous. This is manifested in the loss of the shearing edge on the carnassial teeth. The premolars that also serve as shearing teeth in most carnivores are reduced in size and frequently drop out of the mouth at an early age. The molars are the largest of any carnivore and are designed for crushing. Black Bear, Ursus americanus The black bear hardly needs a description. It is the largest carnivore in Wisconsin and can be recognized by size alone. Adults average 120-350lbs although the largest individuals can exceed 600lbs. The fur is entirely glossy black except for the lighter-colored muzzle. There may be a white patch on the chest on some individuals. Skull The skull is very large and rather dog-like. The auditory bullae are inconspicuous. The anterior premolars are small and vestigial (1A); often one, two, or more of the premolars are missing, giving this species a variable dental formula. The last upper molar is longer than the preceding molar (1B) - a trait that distinguishes the skull from all other large Wisconsin carnivores. The palate terminates well behind the last upper molar. Dental Formula: I: 3/3 C: 1/1 P: 2-4/2-4 M: 2/3 = 34-42 1A  1B  Similar Species: The bear skull is likely to be confused only with the wolf skull. The latter is smaller, has well-developed carnassial teeth, the last molar smaller than the preceding molar, and the palate terminating at the last upper molar. Family Procyonidae - Raccooons Procyonidae is a New World family with its distribution centered in Central and South America; it is represented by a single species in Wisconsin. The procyonids are very closely related to the bears and share several characteristics in common with them: five toes on each foot, plantigrade foot structure, and the lack of a shearing edge on the carnassial teeth. Unlike bears, procyonids have long tails and most species have bold markings on the face and tail. The feet are very dexterous. As suggested by their tooth structure, members of this family are highly omnivorous. Raccoon, Procyon lotor Specimen The raccoon is such a common and familiar animal that it hardly needs a description. Its bushy tail with alternating dark and light brown rings is diagnostic. The dark patches surrounding the eyes are also a key identification mark. The fur is grayish (sometimes more brownish) and appears quite grizzled. The soles of the feet are naked. Similar Species: The badger, with its black and white facial pattern is the only Wisconsin mammal that comes close to resembling the raccoon. You can separate the badger from the raccoon by the badger's shorter tail which lacks the ringed pattern. Skull The raccoon skull resembles that of a small bear except that the anterior premolars are more well- developed and the auditory bullae are large and inflated. The braincase is large. The shearing edge is absent from the carnassials and the molars are rather human-like. The palate terminates well behind the last upper molar. The sagittal crest is usually absent, but if present, is not prominent. Dental Formula: I: 3/3 C: 1/1 P: 4/4 M: 2/2 = 40 Similar Species: The raccoon skull is about the same size as the fox skull and can be distinguished from it by the lack of well-developed carnassial teeth and the palate extending well beyond the last molar. Mustelid skulls have well-developed carnassial teeth and the last upper molar has an unusual shape (see accounts and skull pictures for those species). The felids have a very short rostrum, large shearing edges on the carnassials, and a single small upper molar behind the carnassial tooth. The opossum skull differs as described under the account for the order Carnivora. Family Mustelidae - Weasels, Badgers, Otters The diverse mustelids include a wide variety of body plans making it difficult to describe characteristics that hold true for every member of the family. The group is defined primarily by the presence of a pair of musk glands located near the anus (a trait shared by the skunks). The general body plan includes a long, cylindrical body, short legs, and a long tail (although some members of the family such as the wolverine and badger are stocky and lack the elongated body and have a shorter tail). The feet are somewhat in between plantigrade and digitigrade and are often referred to as semi-plantigrade. There are five toes on each foot and the soles of the feet are furred. The fur is of high quality making mustelids the most valuable furbearers in our state. Several species of mustelids are raised on fur ranches, and one species (the domestic ferret) is commonly kept as a pet. Occasional exotic individuals may escape and be encountered in the wild. In the early 1970's several stone martens (Martes foina) escaped from a fur farm in southeast Wisconsin. The animals have since spread to several counties, but the population appears to be growing slowly. The stone marten is often found in suburban and agricultural areas in Europe (where it is native), and it has great potential to spread throughout the Midwest. The ecological impacts of the introduction are unknown. Most mustelids demonstrate sexual dimorphism in which the males are much larger than the females. The purpose of this seems to be related, at least in part, to the breeding habits of these animals. Males use their large size to subdue the unwilling female and mate with her. Females do not undergo normal estrous cycles as in most mammals, and it is the act of forced (and often violent) copulation that induces the release of eggs. The fertilized eggs undergo delayed implantation until conditions are right (in Wisconsin this is timed so that the young are born in spring). The delayed implantation probably evolved to accommodate the unpredictable mating habits of males. Mustelids are well-known for their aggressiveness, a trait that may have been selected for by this unusual mating system. The badgers and otters are quite different from other members of the family, and some taxonomists now place the badgers and otters in their own separate families. Similar Species: Mustelids can be separated from most other Wisconsin carnivores by the presence of five prominent toes on each foot. The raccoon and bear are the only other carnivores with five toes and the raccoon has the distinctive ringed tail and the bear is much larger than even the largest of the mustelids. Some small mustelids may resemble other mammalian orders. These are listed under the individual species accounts. Skull Mustelids have only one upper molar and it often has an unusual shape (hourglass or 8-shaped or triangular) and may be turned such that it forms a 45° or 90° angle with the rest of tooth row. The carnassials are well-developed. Many mustelid skulls have a distinct look when viewed from the side: the rostrum is short and the braincase elongated. In this view, the toothed portion of the jaw makes up less than half of the total length of the skull. The top of the skull is also flattened in side view because there is little to no downward slope of the rostrum. The palate extends well beyond the last molar. The sagittal crest is well-developed in most species. Similar Species: The skunk skulls most closely resemble the skulls of the mustelids, but the palate in skunks ends at the last upper molar (it ends well behind the last upper molar in mustelids). Because of the short rostrum, the skull may be confused with that of a felid. The latter has the last molar greatly reduced in size and a brain case that is not elongated. The Canidae have the palate terminating at the last upper molar. The raccoon lacks carnassial teeth and the last upper molar is not unusual in shape. The opossum skull differs as described under the account for the order Carnivora. The bat and insectivore skulls are smaller, but still may be confused with the smaller weasels. The characteristics that differentiate them are also listed under the account for the order. Genus Martes - Martens Specimen Martens are often considered the most primitive of the mustelids (due to the dental formula). They are weasel-like in form, but have a longer and bushier tail - an adaptation to their semi-arboreal lifestyle. The study skins are best recognized by color pattern and the long, bushy tail. Skull The skull is the least mustelid-like of the group with a more elongated rostrum. The last upper molar is 8- shaped and looks to be turned sideways such that it forms a nearly 90° angle with the previous tooth. On older animals, the sagittal crest is well-developed and juts out past the back edge of the skull. The zygomatic arches are long and thin. Dental Formula: I: 3/3 C: 1/1 P: 4/4 M: 1/2 = 38 Similar Species: The marten skull can be separated from the otter and badger by the shape of the last upper molar (triangular in the badger and rectangular in the otter). Mustela and Neovison species have a similarly shaped last upper molar, but the skulls of Mustela are smaller and the last upper molar forms a 45° (or less) angle with the previous tooth. The wolverine has a nearly identical upper tooth pattern, but the skull is larger and more heavily built with much thicker zygomatic arches. The martens can also be separated from all other mustelids by their dental formula. Approximate angle formed by the inner edges of the last upper molar and carnassial tooth of Mustela or Neovison (left) and Martes (right). Fisher, Martes pennanti The fisher is the largest of the martens, about the size of a fox. The fur is dark brown, often with a few silver hairs intermixed. The head is usually lighter in color and the legs and tail a darker brown than the rest of the body. There may be a single or several white blotches on the chest, chin, and/or stomach, but many individuals have no distinct markings. The tail is long and bushy like that of a fox. The ears are small and rounded. 45°  90°  Similar Species: The American marten is smaller (about half the size) and has a large conspicuous buff or orange-colored patch covering the chin, bottom of the neck, and chest. The marten also has larger and somewhat pointed ears. The wolverine has the distinctive "saddle" pattern on the back, is much larger, and has a shorter tail. The otter is lighter brown in color, has webbed feet, and has shorter fur (especially on the tail). The mink has a nearly identical color pattern, but always has a white chin patch and is about half (or less) the size of the fisher. Skull The skull is as described for the genus. It is differentiated from the marten skull primarily by its larger size. American Marten, Martes americana Specimen This species is a mink or cat-sized marten with a distinct yellow or orangish-colored patch covering the chin, lower surface of the neck, and chest. The fur is yellowish-brown on the back and sides; the legs and tail are darker in color. The ears are conspicuous, somewhat pointed and fox-like. Similar Species: The color pattern and yellowish chest patch separate it from the mink and fisher. The introduced stone marten is similar but has a large white (instead of yellowish) chest patch. Skull The skull is as described for the genus. It is differentiated from the fisher skull primarily by its smaller size. Genera Mustela (Weasels) and Neovison (Mink) These genera consist of small mustelids with long, cylindrical bodies, short legs, short ears, and long tails. The body design allows weasels to pursue their prey into enclosed spaces such as burrows. The tail is furred, but not as bushy as in the martens. See individual species accounts for other mammals that might be confused with this group. The mink was once grouped with the weasels in the genus Mustela. The designation of Neovison has been controversial and many taxonomists fail to recognize the split since there are few characteristics separating the genera. For this class, you may use either genus to describe the mink. Skull Mustela and Neovison have an especially elongated brain case, and the top of the skull is flat in profile. A low sagittal crest is often present. The last upper molar is dumb-bell shaped and looks like it is turned inward, creating a 45° angle with the previous tooth. Dental Formula: I: 3/3 C: 1/1 P: 3/3 M: 1/2 = 34 Similar Species: The small size alone is usually enough to distinguish this group from the other mustelids. The marten skull may approach the mink skull in size, but the marten has the last upper molar forming a 90° angle with the previous tooth and an obvious downward slope of the snout beginning at the front of the orbits. The pattern of the last upper molar is diagnostic for Mustela and Neovison. Weasels The weasels are the smallest of our mustelids. In summer pelage, they are brown to reddish-brown above with a white or cream-colored venter and a black tip on the tail. In winter, most animals turn completely white with the possible exception of the tail tip which remains black in two species. Three species of weasel occur in Wisconsin. Two of these, the long-tailed weasel and the short-tailed weasel can be very difficult to distinguish from one another. Tail length (expressed as percent of head and body length) is often considered important for identifying specimens, but there is great individual variation and much overlap exists. Although there is a significant overall size difference between the two species, identification is complicated by sexual dimorphism; this results in size overlap between female long- tailed and male short-tailed weasels. Male long-tailed and female short-tailed weasels can be more reliably identified. The same is true of the skulls. Unless the sex is known, identification to species may not be possible. Similar Species: The summer weasel specimens are sometimes confused with members of the squirrel family, particularly the red squirrel. The latter has only four conspicuous toes on the front foot and has a much bushier tail that lacks a black tip. The least weasel is small enough to be confused with a vole, but the number of toes on the forefoot and conspicuous two-toned color pattern will differentiate them. The insectivores lack noticeable ears and none of the Wisconsin species have a similar color pattern. Long-tailed Weasel, Mustela frenata This species is the largest of our weasels and has a long tail (40-70% of head and body length) that terminates in a black tip. Females may be smaller than male short-tailed weasels. Of our three species, this is the only weasel that may not undergo a winter color change. Although most individuals turn white, some specimens only turn partially white (being blotched white and brown) or retain the summer coloration throughout the winter. This lack of color change is most prevalent in southeast Wisconsin and for reasons that are unclear, it is much more frequent in males than females. The feet usually contain some degree of brown coloration in the summer (this is not particularly reliable, but compare with the account for the short-tailed weasel). Similar Species: The criteria described above are helpful for distinguishing the long-tailed weasel from the short-tailed weasel (at least in theory): overall size (if sex is known), relative tail length, and foot color. The least weasel is much smaller with a shorter tail that lacks a conspicuous black tip. The mink is much larger, lacks the whitish underside in summer and does not turn white in the winter. Skull There are no good criteria other than size for separating the skulls of the weasel species. Male long- tailed weasel skulls exceed the maximum measurements for all short-tailed weasel skulls. Unless sex is known, the skulls of female long-tailed and male short-tailed weasels cannot be differentiated. Short-tailed Weasel, Mustela erminea The short-tailed weasel is nearly identical to the long-tailed weasel, but slightly smaller. The tail is less than 40% of the head and body length. The feet are often entirely white in summer (once again, not a reliable trait). This species always changes color in winter. Skull See description under long-tailed weasel. Least Weasel, Mustela nivalis This is the one species of weasel that is easy to differentiate from the others. It is very small (the smallest of the Carnivora), about the size of a vole but with a more elongated body. The least weasel evolved to hunt mice and voles by pursuing them through their runways. As with other animals adapted to life in tight passageways, the tail is very short: less than 20% of the total length (1-1.5"). There is no black tip on the tail although a few scattered black hairs may be present at the tip. In winter, it is pure white except for the eyes, nose, and the few black hairs at the end of the tail. The fur fluoresces a magenta color under UV light, a good identifying characteristic if the tail is missing from the specimen. Similar Species: Large males may overlap small female short-tailed weasels in general body size. Use the short tail and its lack of a distinct black tip to separate it from the other weasels. Skull The skull of the least weasel is less than 1.5" in length. Small short-tailed weasel skulls may overlap in size with large male least weasel skulls. Comparison in size and tail length of the short-tailed weasel (top) and least weasel (bottom) American Mink, Neovison vison The mink is larger than our weasels; males are about the size of a rabbit, females are squirrel-sized. The body is shaped like that of a typical weasel, but the tail is bushier (although not as bushy as in the martens). The fur is dense and glossy, almost entirely dark brown except for a small white patch on the chin and/or throat. Domestic mink come in a wide variety of colors and may be encountered in the wild (as they frequently escape from fur farms). Unlike the weasels, the mink does not change color in the winter. The toes are partially webbed. Similar Species: The mink is most likely to be confused with the martens. It is similar in color to the fisher, but is smaller in size, has a less bushy tail, and is uniform brown (no grizzling) without the darker color tones on the legs. The American marten is around the same size as the mink, but also has a bushier tail, darker colored legs, and a large yellowish patch covering most of the chest. The two larger weasels have a different color pattern which involves a whitish underside and a black tail tip. Skull The mink skull is essentially a larger version of the weasel skull. Similar Species: the mink skull is always larger than that of the weasels although that of a large male long-tailed weasel may approach it in size. It differs from the marten skulls as described under the account for the genus Martes. Wolverine, Gulo gulo Specimen A very large (dog-sized) and stocky mustelid that is bear-like in general form with a broad heavy head and small rounded ears. The tail is short (c. 1/5 of the total length) and bushy, the legs short and thick, and the feet large. The fur on the back is rather long; that of the face and legs is shorter. The overall color is dark brown with two broad yellowish stripes that extend from the upper shoulders along the sides and merge across the rump, forming a saddle-like pattern. A yellowish band is also present on the forehead. The legs and tail are often darker in color. There is an irregularly shaped creamy patch on the chest. Similar Species: The wolverine is unique in its size, form, and color pattern and is apt to be confused with few other Wisconsin mammals. It most closely resembles the badger, but is much larger with longer legs and lacks the giant foreclaws and striped facial pattern. The saddle-back pattern, size, and short bushy tail should help you distinguish it from all other species. Skull The skull is quite formidable, large and heavily built with a distinctly arched profile. The zygomatic arches are very thick. The sagittal crest is especially prominent with the hind edge overhanging the back of the skull. The carnassial teeth are massive, and the last upper molar is 8-shaped and intrudes onto the upper palate, forming a 90° angle with the previous tooth (similar to the martens). Dental Formula: I: 3/3 C: 1/1 P: 4/4 M: 1/2 = 38 Similar Species: The last upper molars of the wolverine skull will identify it as a mustelid. The last upper molar is 8-shaped, separating it from the badger which has a triangular-shaped last upper molar. The skull most closely resembles that of the fisher. It can be separated by its larger size and thick zygomata; the zygomata in Martes are thin and appear more delicate. River Otter, Lutra canadensis Specimen The otter is a large mustelid. It follows the classic weasel blueprint having an elongated body, short legs, and a long tail. It differs from other mustelids in that the feet are webbed and the tail is thick and muscular. The face is short and lacks a prominent snout. The ears are very small; the nose is large and conspicuous. The entire body is covered in dense, short fur. The fur is brownish (with lighter grayish- brown underfur) dorsally, but is usually lighter in color on the belly. Similar Species: The otter can be distinguished from all other carnivores by its webbed feet and long, thick tail. The tail is furred unlike that in the muskrat and beaver. Skull The otter skull appears rounded in top view due to the rounded zygomatic arches and extremely short, blunt rostrum. The braincase is large and round. There is usually no sagittal crest, but the postorbital process is very prominent compared to most other mustelids. In side view, the skull looks remarkably like that of a weasel, being severely flattened on the top. The first upper premolar is small and peg-like (1A). The upper carnassial teeth are triangular in shape, the shearing edge occurring in the middle of the tooth. The last upper molar is rectangular (1B). The lower jaw is often inseparable from the upper skull. The auditory bullae are flattened. The infraorbital foramen is large for a carnivore. The upper palate terminates beyond the last upper molar. Dental Formula: I: 3/3 C: 1/1 P: 4/3 M: 1/2 = 36 Similar Species: Because the last upper molar is not 8-shaped, the otter may be confused with other families of carnivores. The raccoon has no shearing edge on the carnassials, has a longer rostrum, inflated auditory bullae, and a much smaller infraorbital foramen. The skull superficially looks like a felid because of the short snout, but in the otter, the last upper molar is not reduced in size as it is in felids. The shape of the last upper molar or the peg-like first upper premolar will separate the otter from all other mustelids. The extension of the upper palate beyond the last molar differentiates the otter skull from that of the skunks. 1B  1A  American Badger, Taxidea taxus Specimen The badger is a short, stout animal well-adapted for digging. In size, it is about equivalent to a medium- sized dog or raccoon. The head and body are dorso-ventrally flattened and the legs very short. The feet are large, the front ones equipped with extremely long, thick claws. The tail is short and bushy. The fur on the body is shaggy; that on the head and legs is shorter. The fur is grayish or tan with a good amount of black hairs intermixed, creating a grizzled pattern. The legs and feet are black or dark brown. The unique facial pattern consists of white and black striping. Similar Species: The facial pattern will distinguish the badger from all other Wisconsin mammals. The facial markings of the raccoon include black encircling the entire eye whereas white fur touches the eye in the badger. The badger also lacks the obvious ringed tail. Skull The skull is heavily built. The most conspicuous characteristic is the braincase which forms a nearly perfect equilateral triangle. In older animals there is a large sagittal crest and the jaws cannot be separated. Behind the zygomatic arch, the braincase appears to be "winged" due to an enlarged nuchal crest (1A). The palate terminates well beyond the last upper molar. The last upper molar and upper carnassial tooth are both triangular in shape (2A). The infraorbital foramen is triangular. Dental Formula: I: 3/3 C: 1/1 P: 3/3 M: 1/2 = 34 Similar Species: No other mustelid has the last two upper teeth triangular in shape. Other similar-sized carnivores lack the triangular-shaped braincase and enlarged nuchal crest. See traits listed under the family for ways to differentiate it from other carnivores. Mephitidae - Skunk Family The skunks were once classified as mustelids, but were separated based on genetic evidence that suggests that they are distinct from other members of the weasel family. Although they are structurally similar, there are several differences that support the genetic findings. The most noteworthy of these is the presence of a nipple associated with the scent gland in skunks, allowing for greater control over the directional spray of musk; in the other mustelids, this nipple is absent. Despite these differences, the skunks are still more closely related to the mustelids than they are to other groups within Carnivora. In Mephitidae, the body is somewhat elongated, the legs are moderately short, and there are five toes on each foot. The posture is plantigrade. The ears are short and rounded. The front claws are long and stout, an adaptation for digging. The tail is long and very bushy. All skunks are boldly marked with black and white to advertise their potent defense system. Similar Species: the black and white coloration and bushy tail will separate the skunks for all other Wisconsin mammals. Skull The skunk skull is mustelid-like with a large brain case and short rostrum. The upper carnassial is triangular and the last upper molar is large and somewhat rectangular as in the otter. The palate terminates at the last upper molar. The auditory bullae are flattened. Dental Formula: I: 3/3 C: 1/1 P: 3/3 M: 1/2 = 34 1A  2A  Similar Species: The skunk skull is most likely to be confused with the mustelids, particularly the otter, from which it can be separated by the palate which extends beyond the last upper molars in Mustelidae, but terminates at the last upper molar in Mephitidae. In felids, the last upper molar is tiny and peg-like. The canids have a much longer and narrower rostrum and braincase, have two upper molars behind the carnassials tooth, and have inflated auditory bullae. The raccoon lacks a shearing edge on the carnassial tooth and has inflated auditory bullae. Comparison of the skunk skull (left) and the otter (mustelid) skull (right). The dashed line indicates the posterior edge of the upper palate. Note the position of the last upper molars in relation to the edge of the palate. Striped Skunk, Mephitis mephitis Specimen The striped skunk is the larger of the two Wisconsin species; roughly the size of a house cat. The body is rather stout. The fur is mostly black with a white band on the back of the head and neck that diverges into two broad stripes along the sides and onto the tail. Aberrant color patterns exist that may range from a complete lack of the back stripes to the two stripes being fused such that one broad stripe covers the entire back. Similar Species: the spotted skunk is smaller, more slender, and has a different coat pattern consisting of irregular white spots or blotches on a black background and a conspicuous white blotch on the forehead. Color variants should be distinguished primarily by size. Size comparison of the striped skunk (top and middle) and spotted skunk (bottom). Also note the variation in the white markings for the striped skunk specimens. Skull See characteristics for the family. The striped skunk skull is about the size of a mink skull (c. 3" in length); this larger size separates it from the spotted skunk skull. The spotted skunk skull also tends to have a more pronounced postorbital process. The skulls of the two species of skunk are otherwise difficult to differentiate. Spotted Skunk, Spilogale putorius This is a small skunk, roughly the size of a large squirrel (museum specimens are often overstuffed and appear larger). The body is relatively slender and elongated: somewhere in between that of a weasel and the striped skunk (once again, study specimens may look just as chunky as the striped skunk). The fur is black with white spots. The spots are often elongated and appear as broken stripes or may be so large that the animal has a black and white marbled pattern. The two specimens collected from Wisconsin are mostly black with smaller white spots (see specimen picture below). There is a white spot in the center of the forehead (1A). Similar Species: The spotted skunk is smaller than the striped skunk, is more slender, and has spots or a marbling pattern instead of two continuous broad parallel stripes on the body. The striped species also has the entire top of the head covered in white with a thin narrow line connecting this to the nose, whereas the spotted skunk has an isolated white spot on the center of the forehead. Skull The skull is similar to the striped skunk skull, but is smaller (usually 2" or less in length) and with a slightly more conspicuous postorbital process. Family Felidae - Cats Compared to the other large families of carnivores, cats show little diversity in body form. All members have a high-domed head with a very short face and forward pointing eyes. The legs are usually long with four toes on each hind foot and five toes on each forefoot; one of the toes on each front foot is a dewclaw. The foot posture is digitigrade. Despite the similarities in foot structure, felids are not closely related to the canids. The tail is usually long and thin, although in some species it may be short or bushy. The feline form is designed for short bursts of speed. The claws are sharp and important for capturing prey; 1A  consequently they are retractile to prevent them from wearing down and becoming dull when the animal is walking or running. Cats are the most carnivorous family of the order and this is reflected in their unique dentition. The carnassial teeth are very large with a sharp shearing edge. The premolar preceding the carnassial is also sharp and aids in shearing. There is only one molar on the upper jaw and it is greatly reduced in size and essentially nonfunctional. The tongue has horny protrusions that help tear flesh. Similar Species: The best way to identify the study skin of a felid is to count the number of toes. Only the canids have the same toe pattern. All Wisconsin cats can be differentiated from the canids by their non-bushy tails which are either shorter than (lynxes) or longer than (cougar) those of our native canids. Skull The cat skull is very distinctive with its short rostrum and reduced dentition. The postorbital process is conspicuous and there is an extension on the zygomatic arch (1A) that reaches toward the pointed end of the postorbital process, creating a round eye socket. The palate terminates slightly behind the last molar. The last upper molar is peg-like (2A). The auditory bullae are inflated. Similar Species: The short rostrum and small last upper molar separates the cat skull from all other carnivores. Some species of mustelids have a short rostrum, but it is never as reduced in size as in the felids. Also, the last upper molars in mustelids are large, not vestigial as they are in the cats. Genus Lynx The lynxes evolved in cold climates of the northern hemisphere. Their tail is short to reduce heat loss, and the legs long and feet large for walking through snow. There is a distinct tuft of hairs on the ear tips and a small "mane" is present on the cheeks and lower jaw. Members of this genus are about twice the size of a typical house cat. Similar Species: The two species of lynx in Wisconsin can be differentiated from the cougar by their smaller size, ear tufts, and short tail. 1A  2A  Skull The skull is classically cat-like. There are only 28 teeth due to the presence of only 3 pairs of upper cheek teeth. Dental Formula: I: 3/3 C: 1/1 P: 2/2 M: 1/1 = 28 Similar Species: The cougar skull is larger and has 4 pairs of upper cheek teeth (instead of 3). Canada Lynx, Lynx canadensis Specimen The lynx has very long legs and enormous feet to aid in walking through the deep snow of the boreal forest. The hind feet are about twice the size of the short tail. The color is grayish brown. There may be faint spots or blotches, but often the coat is more or less uniform in color. Black fur completely encircles the tail tip. The black ear tufts are very long. Similar Species: The lynx closely resembles the bobcat. The best way to differentiate them is by the tail tip; the black fur is only present on the top of the tail in bobcat, but it completely encircles the tail in the lynx. The lynx can also be identified by its larger feet, longer legs, and longer ear tufts. Comparison of the black tail tip in the lynx (top) and bobcat (bottom). Comparison of the length of the ear tufts in the lynx (left) and bobcat (right). Skull The skull is as described for the genus. It can be differentiated from the bobcat by two characteristics: 1.) the anterior condyloid foramen and jugal foramen have separate openings near the auditory bullae in lynx, but share a common opening in the bobcat. 2.) the presphenoid is broad posteriorly but is greatly constricted anteriorly, forming a spade-like pattern in the lynx; in the bobcat it is narrow throughout its length. Underside of skull of lynx (left) and bobcat (right) Bobcat, Lynx rufus The bobcat is a more southern version of the Canada lynx with shorter legs and smaller feet. The dorsal fur is brownish or tan in color, intermixed with reddish or grayish hairs and with some blotches or spots (which may be faint). The spots are especially prevalent on the inner surface of the legs. The underside is whitish. The ear tufts are conspicuous, but shorter than in the lynx. The tail has a black tip on the upper surface only; the lower surface is whitish. Similar Species: See account for lynx. Skull See account for lynx. Cougar, Felis concolor Specimen The cougar is a large felid (about the size of a wolf) with a very long tail. The fur is rather short and is yellowish-brown to reddish-brown in color. The backs of the ears and tail tip are usually black. The ears lack the tufts of hair present in the lynxes. Similar Species: The much larger size, long tail, and lack of ear tufts separates this species from the other native Wisconsin cats. Skull The cougar skull is conspicuously larger than the lynxes' and there is an extra peg-like premolar (1A) on the upper jaw (for a total of 4 pairs of upper cheek teeth). The skull of the domestic cat (Felis cattus) has the exact same dental pattern, but is much smaller. Dental Formula: I: 3/3 C: 1/1 P: 3/2 M: 1/1 = 30 1A  Jeff