Small Mammals

Question 1

What are the distinguishing characteristics common to all mammals

Answer 1

All mammals have mammary glands and hair, although hair may be drastically reduced or present only in foetal stages before birth.

Question 2

What are common characteristics common to most mammals

Answer 2

• Viviparous: the young are developed in-utero.
• The only exceptions are the monotremes which include echidnas and platypus.
• heterodont

Question 3

What are the distinguishing characteristics of the Order Lagomorpha (lagomorphs: rabbits, hares, pikas)

Answer 3

• They have two pairs of upper incisors, with one pair being directly behind the other
• Both their upper and lower incisors have longitudinal grooves on the anterior surface
• 26-28 teeth depending on species, compared to 16-22 in rodents

Question 4

What are the distinguishing cranial characteristics of the Family Leporidae (hares & rabbits)(2) (Lab)? a. Name 2 species that are red- or blue-listed (sub)species. b. Name two introduced species in this family

Answer 4

• distinctive skulls with well-developed supraorbital processes and lattice-like fenestration.
• Two species which are red-listed are Lepus americanus (snowshoe hare, subspecies) and Lepus townsendii (white-tailed jackrabbit).
• Two introduced species of Leporidae in BC are Oryctolagus cuniculus (European rabbit) and Sylvilagus floridanus (eastern cottontail).

Question 5

What isthe distinguishing cranial characteristic of the pika family (Ochotonidae) ((Lab)? i. Name a listed (sub)species.

Answer 5

• skulls lack supraorbital processes.

- Ochotona collaris (collared pika) is a blue-listed subspecies of pika.

Question 6

What are the 2 distinguishing cranial characteristics of the order Rodentia (Rodents)

Answer 6

• 2 upper and lower ever-growing incisors and a lack of canine teeth.
• distinguished by a layer of hard, yellowish enamel which is harder than the dentine surface of the tooth.

Question 7

What are the 2 distinguishing cranial characteristics of the mountain beaver family

Answer 7

• distinct projection on upper cheek teeth

- flask-shaped ear.

Question 8

What is a distinguishing cranial characteristic of the squirrel family

Answer 8

All species of squirrels have well-developed postorbital processes.

Question 9

What are the 2 distinguishing cranial characteristics of the pocket gopher family

Answer 9

• The lower mandible has a small shelf

- hourglass shaped chewing surface of 1st upper cheek tooth

Question 10

What are 4 distinguishing cranial characteristics of the pocket mouse family

Answer 10

• Easily visible external, furlined pocket on either side of mouth,
• infraorbital opening on the side of the rostrum,
• upper incisors grooved,
• auditory bullae huge.

Question 11

How do you identify a skull belonging to the beaver family (Castoridae)

Answer 11

Auditory bullae are elongated for aquatic life.

Question 12

How do you distinguish between a lagomorph skull and rodent skull

Answer 12

Lagomorphs have the following distinguishing characteristics:
They have two pairs of upper incisors, with one pair being directly behind the other
Both their upper and lower incisors longitudinal grooves on the anterior surface
They have 26-28 teeth depending on species, compared to 16-22 found in rodents.

Rodents are distinguished by only 2 upper and lower ever-growing incisors and a lack of canine teeth. These incisors are distinguished by a layer of hard, yellowish enamel which is harder than the dentine surface of the tooth.

Lagomorph skulls won’t have the same prominence of front teeth, while rodent skulls will lack the second pair of incisors behind the first. Rodent skulls will also commonly have a notch in the lower jaw which is missing in lagomorphs.

Question 13

What is a distinguishing cranial characteristic of the voles & lemming subfamily (Arvicolinae)

Answer 13

• complicated patterns of tooth enamel that form closed triangles or transverse folds.

Question 14

What is a distinguishing cranial characteristics of the old world rats and mice (Murids) family

Answer 14

• Molar teeth with 3 rows of tubercles

- palate extends far posterior to the level of the last molar.

Question 15

What is a distinguishing cranial characteristics of the North American rats & mice (Neotominae) family

Answer 15

The tubercles (cusps) on the molar teeth are arranged in two longitudinal rows rather than three rows (see figures 68 & 94 in R & L of B.C.) and do not appear as closed triangles (compare with the subfamily Arvicolinae)

Question 16

What are the 2 best distinguishing cranial characteristics of the jumping mice family

Answer 16

• Upper incisors are narrow and grooved in front.

- Infraorbital opening on the side of the rostrum is large.

Question 17

What four families of rodents and lagomorphs have grooved front upper incisors? Would you change your answer to question 17 with this in mind

Answer 17

Dipodidae (jumping mice)
Heteromyidae (pocket mice)
Leporidae (hares and rabbits)
Ochotonidae: (pikas; 2 species).

Question 18

What is a distinguishing cranial characteristic of the porcupine family

Answer 18

The infraorbital foramen is large

Question 19

How do you distinguish between a beaver skull and porcupine skull

Answer 19

Beaver skull is massive with a relatively narrow braincase, auditory bullae are elongated, and cheekbone is expanded.

Porcupine skull has large infraorbital foramen, a large jaw process, and a forward-projecting tooth-bearing bone structure.

Question 20

What are the distinguishing cranial characteristics of the order Insectivora (insectivores)

Answer 20

All are essentially insect eaters, small in size, and usually have molariform teeth (like that of a molar; premolars and molars when similar in shape) distinctly ‘W’ shaped, primitive in nature.

Question 21

What are the 3 distinguishing cranial characteristics of the shrew family

Answer 21

Skull lacking either complete zygomatic arch or auditory bullae. Teeth with dark red pigment on cusp tip.

Question 22

What are the 2 distinguishing cranial characteristics of the mole family

Answer 22

• Skull with complete zygomatic arch and auditory bullae;

- 11 teeth.

Question 23

What is the distinguishing cranial characteristic of the marsupial order? What other features are unique to this order

Answer 23

Skull unique in shape with 50+ teeth.

Marsupials also have either pouches or only two longitudinal folds of skin enclosing the teats located near midline of the abdomen.

Question 24

List as many red- and blue-listed (sub)species of small mammals as you can

Answer 24

Lepus americanus: snowshoe hare (R-listed subspecies).
Lepus townsendii: white-tailed jackrabbit (R-listed).
Sylvilagus nuttallii: Nutall’s cottontail (B-listed).
Ochotona collaris: collared pika. (B-listed subspecies)
Neotamias minimus: least chipmunk (R- & B- listed subspecies)
Neotamias ruficaudus: red-tailed chipmunk (R- & B- listed ssp)
Marmota vancouverensis: V-Island marmot (R-listed)
Thomomys talpoides: Northern pocket gopher (R-listed ssp.)
Perognathus parvus: Great Basin pocket mouse (B-listed)
Myodes gapperi: southern red-backed vole (R-, & B-listed ssp.)
Synaptomys borealis: northern bog lemming (B-listed ssp.)
Microtus townsendii: Townsend’s vole (R-listed ssp.)
Reithrodontomys megalotis: western harvest mouse (B-listed)
Zapus hudsonicus: meadow jumping mouse (B-listed ssp.)
Sorex bendirii: Pacific water shrew (R-listed)
S. merriami: Merriam’s shrew (R-listed)
S. navigator brooksi: Western water shrew (B-listed)
S. rohweri: Olympic Shrew (R-listed)
S. palustris: American water shrew (B-listed)
S. preblei: Preble’s shrew (R-listed)
S. trowbridgii: Trowbridge’s shrew (B-listed)
S. tundrensis: tundra shrew (R-listed)
Scapanus townsendii: Townsend’s mole (R-listed)

Question 25

Coprophagy, and which order it is common to?

Answer 25

A unique digestive process where a secondary type of pellet is eliminated from the digestive tract (soft green pellet) and then re-ingested, allowing for absorption of nutrients which were released in the initial digestion process. Common to lagomorphs.

Question 26

Heterodont vs. homodont

Answer 26

Heterodont refers to a variety of teeth which are differentiated along the jaw. In a homodont, all teeth are the same or alike.

Question 27

Polyphodont

Answer 27

A polyphyodont is any animal whose teeth can be replaced many times.

Question 28

Hypsodont vs. Brachydont

Answer 28

Brachyodont–low crowned teeth, enamel covered, determinant growth.
Hypsodont–high crowned teeth, ridges of enamel run longitudinally; can be open
rooted and ever-growing.

Question 29

Diphyodont vs. Monophydont

Answer 29

Diphyodont: milk (baby) teeth that are succeeded by another set of (adult) teeth.
Monophydont: single set of teeth throughout life.

Question 30

Lophodont

Answer 30

• Lophodont teeth have elongated ridges called lophs that run between cusps.
• The molars and premolars of many rodents are lophodont.

Question 31

Bunodont

Answer 31

Bunodont– Many mammals, including humans, pigs, bears, andraccoons, have cheek teeth with low, rounded cusps. These upper and lower cheek teeth are termed bunodont.

Question 32

Selenodont

Answer 32

• cusps are elongated in an anterior-posterior direction.
• increasing the number and size of enamel cutting surfaces
• cheek teeth of deer and cattle

Question 33

Cheek teeth

Answer 33

Cheek teeth are those that come after the canine teeth (premolars and molars).

Question 34

Incisors, canines, molars, premol

Answer 34

Incisors: clipping teeth
Canines: fighting, tearing flesh, grasping
Premolars: simple and before the molars
Molars: more complicated crowns and more roots