New York State Mammals

Order Lagomorpha Order Rodentia

FAMILY: LEPORIDAE

• Rabbits and hares • Conspicuous tail • Fenestra appears as bony latticework • Some species molt seasonally • Presence of a second incisor directly posterior to an anterior, larger incisor on top jaw (incisors white) • Females are often larger than males Eastern cottontail Sylvilagus floridanus Habitat: – Generalist, can use open or densely-vegetated areas Notes: – Often misidentified with the New England cottontail – Altricial young ID: – Pelage: Dorsally brown & gray, ventrally white, white spot between eyes New England cottontail Sylvilagus transitionalis Habitat: – Densely-vegetated areas Notes: – Recently split into S. transitionalis and S. obscurus (Appalachian cottontail) ID: – Anterior edge of ears black, black spot between ears – Otherwise similar in appearance to S. floridanus Snowshoe hare Lepus americanus Habitat: – Dense softwood – Spruce Notes: – Molts seasonally – Precocial young ID: – Pelage: dorsally rusty brown, ventrally grayish, black tips on ears – Skull: Supraorbital process triangular and wing-like New York State Mammals

Order: Rodentia

FAMILY: SCIURIDAE

• Most are diurnal • Varied niche strategies -Tree squirrels -Flying squirrels -Ground squirrels

Rodent Pear-shaped at dorsal view skull

Postorbital process Diastema

• 4 incisors, diastema • Pear-shaped skull • Well-developed postorbital process Red squirrel Tamiasciurus hudsonicus Habitat: – Primarily softwoods Notes: – Most aggressive of squirrels – “chattery” ID: – Smaller, 200 g – Rusty color with ventral lighter (in summer a black line separates the two colors) – White ring around eyes Eastern gray squirrel Sciurus carolinensis

Habitat: – Generalist Notes: – Caches nuts in trees & ground – Constructs dreys ID: – Large (520 g) gray colored squirrel with big bushy tail – Also melanomic morph • Melanin = darker color

Squirrel Drey Fox squirrel Sciurus niger Habitat: – Prefers more open forest with large trees than eastern gray Notes: – 800 g = larger than S. carolinensis ID: – Mixture of red and gray pelage in New York – Brown-red fringe along tail Northern flying squirrel Glaucomys sabrinus Habitat: – Mixed Coniferous forests Notes: – Nocturnal; glides – Patagium, tail – Diet: nuts, acorns, fungi and lichens ID: – Ventral hairs are white with gray base (vs. southern) – ~ 100 g Southern flying squirrel Glaucomys volans Habitat: – Hardwood forests Notes: – Nocturnal, glider – Diet: nuts, fungi, lichens ID: – Small; 70 g – Gray or silver dorsally, ventral hairs with white base

Eastern chipmunk Tamias striatus Habitat: – Forested areas and woodlots Notes: – Undergo torpor (~hibernation) through winter ID: – 120 g – 5 stripes on back Woodchuck Marmota monax Habitat: – Grassland and fields Notes: – True hibernator – Solitary ID: – 3.5 kg; Brown pelage, short tail, black feet – Skull: white incisors, wide flattened skull, post-orbital process at right angle FAMILY: CASTORIDAE

• Only 2 species worldwide

• 2nd largest rodents in the world

• Semiaquatic adaptations:

– Nictitating membrane (eye cover)

– Ear and nostril muscles

– Insulating pelage

• Castor sacs: type of scent gland, used to mark territory Beaver Castor canadensis Habitat: – Lakes, ponds, and rivers Notes: – Able to remain underwater for 15 minutes – Tail slap often used as alert ID: – 15 – 30 kg; Webbed feet – Chocolate colored pelage – Skull: Large, pigmented incisors

FAMILY: MURIDAE

• Old World rats, mice, gerbils, etc. • Found worldwide • Contains 13% of all extant mammalian species • Most nocturnal

House mouse Mus musculus Habitat: – Found in proximity to humans Notes: – Introduced from Europe ID: – Naked or sparsely haired tail, – smaller orbits than deer mouse Norway rat Rattus norvegicus

Habitat: – Cosmopolitan species Notes: – “Sewer rat” or “Brown rat” ID: – 500 g – Brown rat with naked tail, tail shorter than length of body Black rat Rattus rattus Habitat: – Coastal areas of US Notes: – Introduced ID: – 200 g; smaller than R. norvegicus – Usually black pelage – tail is longer than the length of the body FAMILY: CRICETIDAE

• New World rats, mice, voles, hamsters, etc. • Diverse & species rich

• Most terrestrial, 1 in NYS is aquatic Muskrat

• Subfamily Neotominae- deer mice, woodrats et al. – Long tails & prominent ears

• Subfamily Arvicolinae - lemmings & voles – Stout bodies, with small, rounded ears, short legs & tails White-footed mouse Peromyscus leucopus Habitat: – Forested areas Notes: – Common Peromyscus in the east ID: – 20 g – Tail not sharply bicolored, shorter tail than P. maniculatus Deer mouse Peromyscus maniculatus Habitat: – Forested areas Notes: – Widely distributed ID: – 20 g – Tail sharply bicolored, longer tail than P. leucopus, tuft of hair at end of tail – Difficult to distinguish from white-footed mouse w/o genetics

Old World vs. New World Molar cusp morphology

New World (Cricetidae/Neotominae/) Rattus, Mus

Sharper peaks, longitudinal orientation

Old World (Muridae/Murinae/) Peromyscus

Rounder peaks (lobes), lateral orientation

Lazzari et al. 2008 R. norvegicus and R. rattus

Lobed cusps New World molar morphology Neotominae vs. Arvicolinae

• Arvicoline (vole) molars are easy to spot – essentially consist of a large number of triangles

• Can immediately distinguish voles from rats and mice

• Also useful for keying voles to species (advanced) Arvicoline (vole) dentition

*Note squarish/blocky shape of cranium (when viewed from top) – another Arvicoline characteristic Rattus vs. Rattus R. norvegicus R. rattus (brown) (black)

Temporal Temporal ridges ridges nearly parallel convex Rattus vs. Rattus

• Temporal ridges on R. rattus are more convex, suture lines on parietal bone meet angle on temporal ridge.

• R. norvegicus has more parallel temporal ridges, and suture lines intersect temporal ridge a little behind the main angle on temporal ridge. More examples

Which Rattus is which?

Distinguishing Peromyscus Not for the faint of heart

Tail bicoloration: Both have white feet!

• Sharper contrast in P. maniculatus Both species have overlapping ranges • Less distinct contrast in P. leucopus for hind foot length and tail length, thus • Longer tail in P. maniculatus absolute length is not a reliable • Tufted tail tip in P. maniculatus indicator

Photos © Hilton Pond Center Key points for skeletal diagnostics

• Tree squirrels all have rounded, pear- or lightbulb- shaped skulls with prominent postorbital processes

• Not easy to tell tree squirrels apart by skull, except for Sciurus carolinensis (Eastern Gray Squirrel), which has an additional pair of anterior peg teeth

• Woodchucks (Marmota monax) are squirrels (sciurids); beavers (Castor canadensis) are not

• Look for the white incisors and pointed, angular postorbital process to distinguish M. monax from beaver/muskrat Key points for skeletal diagnostics

• Arvicolines (voles) can easily be distinguished from rats and mice by looking at molars

– Arvicolines can be distinguished from one another based on the pattern of triangles, shape of the palatal shelf, and other cranial characters

• Shape of molar cusps can help distinguish Peromyscus from Mus and Rattus

• Shape of temporal ridges can distinguish Rattus norvegicus from Rattus rattus