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 skull Pear-shaped at dorsal view Postorbital process Diastema 4 incisors, diastema Pear-shaped skull Well-developed postorbital process
Red squirrel Tamiasciurus hudsonicus Habitat: Primarily softwoods Notes: ID: Most aggressive of squirrels chattery 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 Habitat: Sciurus niger Prefers more open forest with large trees than eastern gray Notes: ID: 800 g = larger than S. carolinensis Mixture of red and gray pelage in New York Brown-red fringe along tail
Northern flying squirrel Habitat: Glaucomys sabrinus Mixed Coniferous forests Notes: ID: Nocturnal; glides Patagium, tail Diet: nuts, acorns, fungi and lichens 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
Habitat: Eastern chipmunk Tamias striatus Forested areas and woodlots Notes: ID: Undergo torpor (~hibernation) through winter 120 g 5 stripes on back
Habitat: Grassland and fields Notes: ID: True hibernator Solitary Woodchuck Marmota monax 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 2 nd 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 Habitat: Castor canadensis Lakes, ponds, and rivers Notes: ID: Able to remain underwater for 15 minutes Tail slap often used as alert 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 Habitat: Mus musculus Found in proximity to humans Notes: ID: Introduced from Europe Naked or sparsely haired tail, smaller orbits than deer mouse
Norway rat Rattus norvegicus Habitat: Cosmopolitan species Notes: ID: Sewer rat or Brown rat 500 g Brown rat with naked tail, tail shorter than length of body
Black rat Habitat: Rattus rattus Coastal areas of US Notes: ID: Introduced 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 (brown) R. rattus (black) Temporal ridges nearly parallel Temporal ridges 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: Sharper contrast in P. maniculatus Less distinct contrast in P. leucopus Longer tail in P. maniculatus Tufted tail tip in P. maniculatus Both have white feet! Both species have overlapping ranges for hind foot length and tail length, thus absolute length is not a reliable indicator Photos Hilton Pond Center
Key points for skeletal diagnostics Tree squirrels all have rounded, pear- or lightbulbshaped 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