PLEASE PICK UP & HANDLE THE SKULLS CAREFULLY !!!

  1. Each lab table has two mammal skull specimens on each side of it. The skulls are sitting on some paper towel with a number written on it. As you begin looking at them, find the number on this sheet and fill in the data on the correct line for the skull you're looking at.
  1. On Each lab table is a computer which has opened and ready to use as a reference for this lab. YOU MUST STAY ON THIS WEBSITE AND NOT GO TO ANY OTHER WEBSITES.
  1. On each lab counter you will also find a guide to help you identify the specimens. Good Luck!

PROCEDURE

  1. Count the incisors. PLEASE DO NOT USE THE WRITING TIP OF A PENCIL OR PEN TO TOUCH EACH TOOTH. This can leave a mark and ruin the specimen. Write this number down in the 'Number of teeth - incisor" column. If teeth have fallen out be sure to count them or the space.
  1. Then count the canines and then the molars and record the data the same way you did for the incisors
  1. Next you must look for other characteristics that will help you identify this mammal. Below are listed some characteristics you can use.
  1. Eye Location -- eyes forward indicate animal was a hunter or a predator
  2. eyes to the side indicate the animal was hunted or was prey
  1. Size of Nasal Cavity -- the larger nasal cavity, the better the animal's sense of smell was
  1. Size of Auditory Bullae -- the larger the auditory bullae, the better the animal's hearing was
  1. Size of Brain Case -- the larger the brain case (in general) the smarter the animal was
  1. Sagittal Crest Size -- The larger the sagittal crest the more powerful the jaw muscles
  1. Now you need to decide what this animal eats. Is it a carnivore, omnivore, or herbivore?

Remember your definitions for each. Below are some clues to help you determine what the

animal's diet was? Record your answer in the data table.

  • CARNIVORE -- Mostly sharp, pointed teeth for ripping and shredding flesh
  • HERBIVORE -- Flat for grinding plant material
  • OMNIVORE -- Have some of both (Think of your own teeth - yes you are an omnivore)
  1. After you have considered all the evidence and written down all the data on your data table, take a guess on what the animal is, there is a list on the board to help you, this part is Extra Credit.

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Skull Adaptations In Wisconsin Mammals

Unit 4 – Natural Systems & Cycles

Skull Adaptations and Diet

CARNIVORES

Have long canine teeth (fangs) for ripping and tearing, similar to the beaks of hawks & eagles used to grip or stab moving prey to immobilze it

Upper back teeth (molars) overlap the lower teeth for shearing, similar to sheep shears, only coming from both directions. Molars cut the meat into small pieces, then swallow. Carnivores do not grind meat with their back teeth like humans do.

HERBIVORES

Have cutting incisors to grip or cut vegetation off.

Back teeth (molars) are usually flat this is so vegetation can be thoroughly ground up.

Often lack canines (fangs) because these animals “prey” is not mobile.

OMNIVORES

Have adaptations of both the herbivores and carnivores since they eat plants & animals.

Incisors for cutting

Canines (fangs) for ripping and tearing

Molars (back teeth) overlap on the outside to shear but they also come together to provide an area where food can be ground.

MAMMAL GROUPS

Mammals will be grouped into orders or families of closely related species. Not all mammal species in the state are included on the list but the most common, non-domesticated are included.

Order Insectivores - Moles & Shrews

Group overall has relatively small skulls on average 1.5 to 4.0 cm long.The zygomatic arches (near where the eyes would be located) are not very rounded and are close to the skull in this group.

  1. Star-nosed mole – carnivore

Smallest of the group. Note the slender snout. The skull in general is long and narrow. The top of the skull is rounded. The auditory are very small if visible at all. Teeth – 44 total

  1. Eastern mole – carnivore

The nose is elongated into a snout, although it is not as slender as the star-nosed mole. The top of skull is flat and the braincase is broad. Teeth – 36 total, lower canines not present.

  1. Short-tailed shrew – carnivore

The overall size of the skull is small. The length rarely exceeded 2.5 cm. Arches underneath where eyes are located (zygomatic arch) are not present. The zygomatic arch is found in most other species of mammals. Tips of the teeth have a chestnut color to them. The top of the skull is rather flat. Teeth – 32 total

Order Chiroptera – Bats

There are several species of bats found in Wisconsin only 1 species will be described here

  1. Little Brown Bat – carnivore

Small skull usually under 2 cm in length. The skull is relatively broad. Sagittal crest is usually fairly tall in the back but shorter or not even present if you follow it forward. Braincase is relatively flat. Teeth – 38 total

Order Rodentia – Mice, Squirrels, Voles, & Lemmings

Several members of this group are opportunistic carnivores meaning they will scavenge carrion or take an easy meal like unguarded eggs or young. But usually they do not hunt prey for most of their meals.

  1. Porcupine – herbivore

Note the colored incisors and ribbon-like flat molars for grinding like the beaver. Porcupine skulls tend to be smaller than beaver. Like beaver skulls the top of the skull is relatively flat. Average skull length 9 to 11cm. Teeth – 20 total, lacks canines

  1. Beaver – herbivore

Note the self-sharpening, continuous-growing front incisors. The orange-brown color is a special pigment for making the enamel on the teeth harder. The white inside part of the tooth wears faster creating a continuously sharp leading edge. Also notice the ribbon-like grinding teeth. The enamel is involuted (ridged) to make the teeth stronger just like cardboard in corrugated to make it stronger. Skull is rather flat on top and does not have a prominent sagittal crest. On average the skull is 12 to 14 cm long Teeth – 20 total, lacks canines

  1. Woodchuck – herbivore

Woodchucks are part of the rodent group. Its molars are typically whiter than other rodent’s incisors. It tends to feed on tender succulent plants unlike the beaver. It is actually more closely related to the squirrels than to beavers. The skull is 9 to 10 cm in length on average. Teeth – 22 total

  1. Eastern chipmunk – herbivore

Skull is fairly flat. Skull slopes forward. Skull usually measures about 4.0 cm in length and about 2.5 cm wide. Upper incisors short compared to other rodents. Teeth – 20 total, lacks canines

  1. Least chipmunk - herbivore

Skull overall is slightly rounded and not very flat on top. Skull usually measures 3.0 to 3.5 cm in length. Teeth – 22 total, lacks canines

  1. Flying squirrel – omnivore

Generally, flying squirrel skulls are smaller than other squirrels. It is fairly reclusive and noctural. It feeds on berries and seeds and also will catch insects, moths, beetles and sometimes young birds. Length of skull averages 3.0 to 4.0 cm.Teeth – 22 total, lacks canines.

  1. 13-Lined ground squirrel – herbivore

Skull is generally narrow and weak. The braincase is narrow. Skulls average 4.0 to 4.5 cm in length. Skull narrows into a short snout. Front surfaces of incisors are pale to deep yellow. Teeth – 22 total, lacks canines.

  1. Red squirrel – herbivore (opportunistic omnivore)

Of the squirrels the red squirrel is the smallest. The length average 4.0 to 5.0 cm and the average width is 2.5 to 3.0 cm. Red squirrels tend to feed on spruce, pine, and balsam fir seeds but will opportunistically prey on bird eggs or young if it comes across it. Teeth – 20 or 22, lack canines.

  1. Grey squirrel – herbivore (opportunistic omnivore)

Grey squirrel skulls are slightly larger on average than red squirrels. The lengths range from 6.0 to 7.0 cm and are 3.0 to 4.0 cm wide. Like red squirrels it will opportunistically prey on bird eggs or young if it comes across it, but will not hunt to obtain food. Grey squirrels tend to eat walnuts, acorns, and other seeds it can forage for. Teeth – 22, lacks canines.

  1. Deer mouse – herbivore

Skull is smoothly rounded but little ridged and thin walled. Length of skull between 2.0 to 3.0 cm. The zygomatic arches (located under where the eyes are located) are level with the top of the inside of the mouth in most specimens. Teeth –16, lacks canines

  1. Muskrat – omnivore

Note the diamond shaped grinding surfaces on top of the molars. The muskrat eat aquatic vegetation such as cattails and arrowroot but will opportunistically feed on snails, crayfish, & clams. Teeth – 16 total, lacks canines

  1. Meadow vole – herbivore

Auditory bullae of meadow voles large for the size of the skull and are rounded. Skull length 2.5 to 3.0 cm long. Skull more heavier than the deer mice. Teeth – 16 total, lacks canines.

Order Lagomorphs – Rabbits and Hares

This group of species is difficult to tell apart from the skulls alone

1. Eastern Cottontail – herbivore

This is not a rodent. This animal also has self-sharpening, continuously-growing front incisors. Cottontails have little “peg” incisors found right behind the primary incisors. Teeth – 28 total, lacks canine

  1. Snowshoe hare – herbivore

Skull of snowshoe hare is slightly larger than the cottontail rabbit on average

Order Artiodactyla – Ungulates including Deer, Goats, Bison, Sheep
  1. Whitetail Deer – herbivore

Note the presence or absence of antler pedicels. The molars have crescent-shaped ridges for grinding vegetation, these are called selenodont teeth. Notice the position of the eye more to the side of the skull. Typical of animals which are prey. Upper incisors are absent. Teeth – 32, upper canines absent

  1. Elk – herbivore (reintroduced to WI)

Elk skull is generally larger than a whitetail deer but smaller than a moose. Like whitetail deer, males can only have antlers. Upper incisors absent. Teeth – 34 total

  1. Bison – herbivore (extripated from WI)

Horns project from top of skullTeeth – 32 total, upper canines absent

  1. Moose – herbivore (extripated from WI, although occasional wanderers appear from UP of MI)

Upper incisors absent. Teeth – 32 total, upper canines absent

  1. Caribou – herbivore (extripated from WI)

Teeth – 34 total

  1. Pronghorn – herbivore (not native to WI)

Is the only antelope in North America. Found west of Wisconsin on the Great Plains and western U.S. Note the flat crescent-shaped molars for grinding plant material and the absence of upper incisors. They use the bony plate (palate) on the roof of their mouth instead. Orbits where eye are located project from side of the skull.

Order Carnivores - Divided into families

Canids Family – All members of this family in Wisconsin have 42 teeth

  1. Eastern Timberwolf - carnivore

Note the tall sagittal crest at the rear of the skull. This is where very powerful muscles attach and then connect to the lower jaw. These strong muscles are need to crush bones of their prey which sometimes are large than the wolf itself. Skull tends to be a couple centimeters wider and longer than the coyotes on average

  1. Domestic Dog – (introduced to WI) carnivore

Has a rather short, stout upper fangs compared to the coyote. Large dogs like german shepherds can be difficult to distinguish from wolf or coyote skulls. Wolves, coyotes, and dogs can interbreed. Their skulls are often close to impossible to classify

  1. Coyote – carnivore

Has longer upper fangs than dogs or wolves. Skull tends to be a couple centimeters thinner and shorter than the wolves on average. Sagittal crest tends to be slightly shorter than the wolves.

Foxes – overall tend to have smaller proportions than coyotes and wolves

  1. Grey Fox – carnivore

Main distinguishing characteristic is the pattern of ridges on the top of the skull (temporal ridges). In grey foxes the temporal ridges form a “U” or “V” with rounded bottom if looking from the back of the skull. Temporal ridges are taller or more prominent than red foxes Grey fox skulls upon careful measurement are, on average, a centimeter or two smaller than red foxes

  1. Red Fox – carnivore

Main distinguishing characteristic is the pattern of ridges on the top of the skull (temporal ridges). In grey foxes the temporal ridges form a ““V” with a pointed bottom if looking from the back of the skull. Temporal ridges are shorter than in grey foxes Red fox skulls upon careful measurement are, on average, a centimeter or two larger than red foxes

Feline Family - All members of this group have a high sloping forehead. The molars in felines completely overlap (the most of the carnivore) which is very useful in shearing prey.

  1. Domestic Cat – (introduced to WI) carnivore

Arch that defines where eye is located are oval and are connected. Compared to its wild cousins domestic cats have lost some of their sense of smell. Domestic cats still having excellent sense of hearing. Sagittal crest is present but is not very tall. Teeth – 30 total,

  1. Bobcat – carnivore

Arches that define eye sockets not connected. Animal has excellent hearing and sense of smell. In general, the bobcat skulls are slightly larger than the domestic cat but smaller than the lynx. Sagittal crest and ridges at the back & base of skull are taller than on the domestic cat but shorter than lynx. Teeth – 28 total

  1. Canada Lynx – carnivore

Arches that define eye sockets not connected like in the bobcat. Animal has excellent hearing and sense of smell. In general, the lynx skulls are larger than the bobcat but smaller than the lynx. Sagittal crest and ridges at the back & base of skull are larger than other felines except the cougar. Teeth – 28 total

  1. Cougar or mountain lion (presumed extinct in Wisconsin) – carnivore

Largest american feline after the jaguar. Skull large with tall sagittal crest. Teeth – 30 total.

Mustelid (Weasel) Family – number and arrangement of teeth in this family varies from species to species.

  1. River Otter – carnivore

Note the streamlined form which is an adaptation for speed in the water where the otter does most of its hunting. The very forward set eye sockets give the otter excellent depth perception which is need to catch fish or crayfish, the otter’s principle prey items. Has an acute sense of smell seen in the relatively larger sinus cavity. Teeth – 36 total

  1. Skunk – omnivore

It is thought that the skunk has evolved into a omnivore diet fairly recently (with the past few thousand years) from a more carnivorous diet. Since this adaptation was recently the bone structure may not have evolved to reflect this change yet. Skunks eat berries and fruit of plants, insects, eggs of birds, turtles, and frogs, small mammals. Teeth – 34 total

  1. Pine Marten – carnivore

Marten and fisher are very similar except for size. The pine marten is smaller than the fisher. On average pine marten skulls are 7.0 to 9.0 cm in length. Sagittal crest is not as produced as in the fisher but is raised towards the back. Teeth – 36 total

  1. Fisher – carnivore

Skull in general is larger than the pine marten. The average length ranges from 10 to 12 cm in length. Sagittal crest on the fisher is slightly raised where large muscles connected to the jaw would attach . And the top of the skull is rounded. Teeth – 36 total.

  1. Badger– carnivore.

Large Skull within this grouping of species. It is the only with such a broad back to the skull. The reason for the broad back is because this is area where the strong neck muscles attach to the skull. Sagittal crest in back in very prominent.

Teeth – 34 total,

  1. Mink – Carnivore

Relatively small skull. The length can range from 5.5 to 7.5 cm long. The mink has an excellent sense of hearing and smell. Sagittal crest slightly raised especially toward the back of skull. Teeth – 36 total

  1. Weasel – Carnivore

Zygomatic arches (where eyes would be on skull) do not extend much further past width of skull. Braincase relatively broad. Sagittal crest not very tall and may not be present if skull is from a juvenile. Teeth – 34 total.

Other Groups

  1. Black Bear – omnivore

Note the very large hind molars. Molars are the same size do matter what age, sex, or size of the animal. Male bear skulls tend to be slightly larger than females. Black bear skulls are the largest of any native / wild mammal in Wisconsin. Teeth – 42 total.