Mammals of Connecticut

43 established wild species in Connecticut. Plus 19 range-listed species with few or no digitized records.

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Neotoma magister

Allegheny Woodrat

Neotoma magister

Marginal occurrence · 1 record
Size 31–45 cm12.2–17.7 in Weight 357 g12.6 oz active by night rocky outcrop
Beaver swimming low in murky green pond water with only its wet head and back above the surface

American Beaver

Castor canadensis

Common in Connecticut 614 sightings
Size 60–90 cm2–3 ft Weight 11–32 kg24.3–70.5 lb active day & night river

Sightings by month

Oso negro (Ursus americanus), Parque natural provincial Tatshenshini-Alsek, Yukón, Canadá, 2017-08-25, DD 85

American Black Bear

Ursus americanus

Common in Connecticut 940 sightings
Size 1.2–2 m3.9–6.6 ft Weight 40–250 kg88.2–551.2 lb active by night conifer forest

Sightings by month

Mustela Erminea head

American Ermine

Mustela erminea

Occasional in Connecticut 23 sightings
Size 17–33 cm6.7–13 in Weight 70–260 g2.5–9.2 oz active by night coniferous forest

Sightings by month

Norka amerykańska (neovison vison)

American Mink

Neogale vison

Common in Connecticut 118 sightings
Size 33–45.7 cm13–18 in Weight 0.5–1.4 kg1–3 lb active day & night lake

Sightings by month

Tamiasciurus hudsonicus James Gardens

American Red Squirrel

Tamiasciurus hudsonicus

Common in Connecticut 492 sightings
Size 17–23 cm6.7–9.1 in Weight 140–310 g4.9–10.9 oz active by day wetland

Sightings by month

American water shrew swimming at the surface of a stream, seen from above

American water shrew

Sorex palustris

Marginal occurrence · 4 records
Size 8 cm3.1 in Weight 8–18 g0.3–0.6 oz active day & night river
Atlantic white-sided dolphin leaping clear of the water at Stellwagen Bank, showing the yellow blaze on its tail stock

Atlantic White-sided Dolphin

Leucopleurus acutus

Marginal occurrence · 2 records
Size 2.1–2.8 m6.9–9.2 ft Weight 180–230 g6.3–8.1 oz active day & night continental shelf

Sightings by month

Big Brown Bats (Eptesicus fuscus)

Big Brown Bat

Eptesicus fuscus

Common in Connecticut 104 sightings
Size 7.5 cm3 in Weight 17 g0.6 oz active by night agricultural

Sightings by month

Bobcat (Lynx rufus)

Bobcat

Lynx rufus

Common in Connecticut 1,696 sightings
Size 30–60 cm11.8–23.6 in Weight 4–18 kg8.8–39.7 lb active by night forest edge

Sightings by month

Common Raccoon in Hugh Taylor Birch State Park

Common Raccoon

Procyon lotor

Common in Connecticut 1,102 sightings
Size 40–70 cm1.3–2.3 ft Weight 3.5–9 kg7.7–19.8 lb active by night mixed forest

Sightings by month

Mother Coyote Sitting, Watching Over Den, Photo 1 of 2 (47924154788)

Coyote

Canis latrans

Common in Connecticut 1,064 sightings
Size 0.8–1 m2.5–3.3 ft Weight 7–21 kg15.4–46.3 lb active day & night urban

Sightings by month

Eastern Chipmunk (Tamias striatus)

Eastern Chipmunk

Tamias striatus

Common in Connecticut 1,386 sightings
Size 16.6 cm6.5 in Weight 93 g3.3 oz active by day urban

Sightings by month

Blacklick Woods - Eastern cottontail feeding 1

Eastern Cottontail

Sylvilagus floridanus

Common in Connecticut 2,049 sightings
Size 36–43 cm14.2–16.9 in Weight 0.8–1.5 kg1.8–3.3 lb active day & night lake

Sightings by month

Grey squirrel (Sciurus carolinensis) 01

Eastern Gray Squirrel

Sciurus carolinensis

Common in Connecticut 3,469 sightings
Size 23–30 cm9.1–11.8 in Weight 400–710 g0.9–1.6 lb active by day wetland

Sightings by month

Eastern Mole (Scalopus aquaticus)

Eastern Mole

Scalopus aquaticus

Occasional in Connecticut 41 sightings
Size 14.8 cm5.8 in Weight 75 g2.6 oz active day & night river

Sightings by month

Eastern red bat roosting among green leaves, disguised as a dead leaf

Eastern Red Bat

Lasiurus borealis

Occasional in Connecticut 29 sightings
Size 9.3–11.7 cm3.7–4.6 in Weight 7–13 g0.2–0.5 oz active by night desert

Sightings by month

Eastern small-footed myotis clinging to a weathered wooden post in daylight, unhandled and alert

Eastern Small-footed Myotis

Myotis leibii

Marginal occurrence · 2 records
Size 7.5–8.5 cm3–3.3 in Weight 5 g0.2 oz active by night cave
European rabbit feeding in dry vegetation

European Rabbit

Oryctolagus cuniculus

Marginal occurrence · 5 records
Size 34–50 cm13.4–19.7 in Weight 1–2.5 kg2.2–5.5 lb active by night grassland

Sightings by month

Martes Pennanti

Fisher

Pekania pennanti

Occasional in Connecticut 40 sightings
Size 75–95 cm2.5–3.1 ft Weight 3.5–6 kg7.7–13.2 lb active dawn & dusk wetland

Sightings by month

Gray fox standing in dappled woodland

Gray Fox

Urocyon cinereoargenteus

Common in Connecticut 144 sightings
Size 0.8–1.1 m2.5–3.7 ft Weight 3–9 kg6.6–19.8 lb active day & night brushy woodland

Sightings by month

Silver-gray wolf walking along a gravel bank in Alaska

Gray Wolf

Canis lupus

Occasional in Connecticut 62 sightings
Size 1.1–1.6 m3.4–5.2 ft Weight 23–80 kg50.7–176.4 lb active day & night cave

Sightings by month

Groundhog (Marmota monax)

Groundhog

Marmota monax

Common in Connecticut 876 sightings
Size 50.6 cm19.9 in Weight 3.4 kg7.5 lb active by day woodland

Sightings by month

Common seal (Phoca vitulina) 2

Harbor Seal

Phoca vitulina

Occasional in Connecticut 86 sightings
Size 1.4–1.9 m4.6–6.2 ft Weight 55–170 kg121.3–374.8 lb active by day coastal

Sightings by month

Phocoena phocoena.2

Harbour Porpoise

Phocoena phocoena

Marginal occurrence · 8 records
Size 1.4–1.9 m4.6–6.2 ft Weight 45–70 kg99.2–154.3 lb active by night coastal
Harp Seal (Pagophilus groenlandicus), Greenland Sea IMG 5032

Harp Seal

Pagophilus groenlandicus

Marginal occurrence · 5 records
Size 1.8 m5.8 ft Weight 141.1 kg311.1 lb active by day coastal
House mouse in dry plant litter

House Mouse

Mus musculus

Occasional in Connecticut 17 sightings
Size 5–10 cm2–3.9 in Weight 12–30 g0.4–1.1 oz active by night agricultural

Sightings by month

Humpback whale (Megaptera novaeangliae) with calf Moorea 2

Humpback Whale

Megaptera novaeangliae

Marginal occurrence · 1 record
Size 12–17 m39.4–55.8 ft Weight 25000–40000 kg55115.6–88185 lb active by day marine
Indiana bats roosting in a dense cluster on a cave ceiling with several individuals in flight below

Indiana bat

Myotis sodalis

Range-listed · no digitized records yet
Size 5.5 cm2.2 in Weight 5–10 g0.2–0.4 oz active by night agricultural
Long-tailed weasel standing alert in grass with its black-tipped tail curled behind it, Sonoma County, California

Long-tailed Weasel

Neogale frenata

Occasional in Connecticut 40 sightings
Size 24.8 cm9.8 in Weight 170 g6 oz active day & night wetland

Sightings by month

Sorex cinereus, Harwich, Chatham, Ontario, Canada 1

Masked Shrew

Sorex cinereus

Occasional in Connecticut 21 sightings
Size 6.9 cm2.7 in Weight 5 g0.2 oz active day & night grassland

Sightings by month

Cow moose standing in a marshy Alaska wetland

Moose

Alces alces

Occasional in Connecticut 48 sightings
Size 2.4–3.1 m7.9–10.2 ft Weight 200–490 kg440.9–1080.3 lb active day & night wetland

Sightings by month

Mountain Lion (Puma concolor)

Mountain Lion

Puma concolor

Marginal occurrence · 3 records
Size 1–1.5 m3.3–5.1 ft Weight 36–120 kg79.4–264.6 lb active day & night montane forest

Sightings by month

Muskrats resting on a floating log in open water

Muskrat

Ondatra zibethicus

Common in Connecticut 192 sightings
Size 25–36 cm9.8–14.2 in Weight 0.6–2 kg1.3–4.4 lb active day & night wetland

Sightings by month

New England cottontail

New England Cottontail

Sylvilagus transitionalis

Rarely seen in Connecticut 3 sightings
Size 38–43 cm15–16.9 in Weight 1–1.5 kg2.2–3.3 lb active dawn & dusk shrubland

Sightings by month

Deer Mouse (Peromyscus maniculatus) (9310532204)

North American Deermouse

Peromyscus maniculatus

Occasional in Connecticut 10 sightings
Size 8–10 cm3.1–3.9 in Weight 21 g0.7 oz active by night river

Sightings by month

North American least shrew moving through short grass

North American Least Shrew

Cryptotis parvus

Range-listed · no digitized records yet
Size 5–8 cm2–3.1 in Weight 6 g0.2 oz active by night grassland
Erethizontidae Erethizon dorsatum 3.2

North American Porcupine

Erethizon dorsatus

Common in Connecticut 160 sightings
Size 60–90 cm2–3 ft Weight 3.5–12 kg7.7–26.5 lb active by night mixed forest

Sightings by month

River Otter (Lontra canadensis)

North American River Otter

Lontra canadensis

Occasional in Connecticut 65 sightings
Size 0.7–1.1 m2.2–3.5 ft Weight 5–15 kg11–33.1 lb active day & night river

Sightings by month

Northern Flying Squirrel (Glaucomys sabrinus)

Northern Flying Squirrel

Glaucomys sabrinus

Range-listed · no digitized records yet
Size 25–37 cm9.8–14.6 in Weight 148 g5.2 oz active by night mixed conifer
Hoary bat in flight against blue sky, wings spread to show its yellow throat patch and heavily frosted fur

Northern Hoary Bat

Lasiurus cinereus

Marginal occurrence · 5 records
Size 13–15 cm5.1–5.9 in Weight 26 g0.9 oz active by night cave
Northern myotis hanging head-down from a rock ceiling, long ears and tan fur visible

Northern Myotis

Myotis septentrionalis

Range-listed · no digitized records yet
Size 8.6 cm3.4 in Weight 6 g0.2 oz active by night coniferous forest
Northern Short-tailed Shrew (Blarina brevicauda)

Northern Short-tailed Shrew

Blarina brevicauda

Common in Connecticut 218 sightings
Size 11.1 cm4.4 in Weight 21 g0.7 oz active day & night riparian

Sightings by month

Live Norway rat beside shallow water

Norway Rat

Rattus norvegicus

Common in Connecticut 87 sightings
Size 15–28 cm5.9–11 in Weight 140–500 g0.3–1.1 lb active by night urban

Sightings by month

Live pygmy sperm whales logging at the sea surface, backs and dorsal fins exposed

Pygmy Sperm Whale

Kogia breviceps

Marginal occurrence · 2 records
Size 2.7–4 m8.9–13.1 ft Weight 320–450 kg705.5–992.1 lb active day & night urban

Sightings by month

Red Fox (Vulpes vulpes)

Red Fox

Vulpes vulpes

Common in Connecticut 1,305 sightings
Size 43 cm16.9 in Weight 5–10 kg11–22 lb active day & night desert

Sightings by month

Silver-haired bat tucked into loose bark

Silver-haired Bat

Lasionycteris noctivagans

Occasional in Connecticut 9 sightings
Size 9.5–11.5 cm3.7–4.5 in Weight 11 g0.4 oz active by night river

Sightings by month

Smoky shrew moving through dense green grass

Smoky Shrew

Sorex fumeus

Rarely seen in Connecticut 5 sightings
Size 7.4 cm2.9 in Weight 8 g0.3 oz active day & night river

Sightings by month

Lepus americanus 5459 cropped

Snowshoe Hare

Lepus americanus

Range-listed · no digitized records yet
Size 41–52 cm16.1–20.5 in Weight 1.4–1.6 kg3.2–3.4 lb active by night coniferous forest
AI-generated image: Southern bog lemming alert among wet sedges and sphagnum at a bog edge. No public-domain photograph of this species exists. This image was generated with AI from verified reference material and reviewed by our editorial team for accuracy

Southern Bog Lemming

Synaptomys cooperi

Marginal occurrence · 6 records
Size 11.8 cm4.6 in Weight 35 g1.2 oz active day & night mixed conifer
Southern Flying Squirrel-27527-1

Southern Flying Squirrel

Glaucomys volans

Occasional in Connecticut 82 sightings
Size 17.1 cm6.7 in Weight 65 g2.3 oz active by night deciduous forest

Sightings by month

Southern red-backed vole feeding among sunflower seeds on snow

Southern Red-backed Vole

Clethrionomys gapperi

Occasional in Connecticut 12 sightings
Size 12–16.5 cm4.7–6.5 in Weight 6–42 g0.2–1.5 oz active by night mixed forest

Sightings by month

Star-nosed mole's fleshy 22-ray nose organ fanned out, close-up macro

Star-nosed mole

Condylura cristata

Occasional in Connecticut 17 sightings
Size 12.1 cm4.8 in Weight 52 g1.8 oz active day & night urban

Sightings by month

Mephitis mephitis in Dierenpark Zie-ZOO

Striped Skunk

Mephitis mephitis

Common in Connecticut 353 sightings
Size 46.5–81.5 cm1.5–2.7 ft Weight 0.6–6.3 kg1.3–13.9 lb active by night grassland

Sightings by month

Two Tamanend's bottlenose dolphins surfacing together, an adult with a smaller paler calf alongside

Tamanend's Bottlenose Dolphin

Tursiops erebennus

Marginal occurrence · 3 records
Size 2.3–2.9 m7.6–9.4 ft coastal
Tricolored Bat hibernating on a limestone mine wall

Tricolored Bat

Perimyotis subflavus

Occasional in Connecticut 17 sightings
Size 7.7–8.9 cm3–3.5 in Weight 5–8 g0.2–0.3 oz active by night cave

Sightings by month

Virginia Opossum clinging to a tree branch in a snowy winter woodland

Virginia Opossum

Didelphis virginiana

Common in Connecticut 831 sightings
Size 40.8 cm16.1 in Weight 1.1–1.6 kg2.5–3.6 lb active by night river

Sightings by month

Little brown myotis roosting alertly on a wooden beam

Western Little Brown Myotis

Myotis lucifugus

Rarely seen in Connecticut 3 sightings
Size 8–9.5 cm3.1–3.7 in Weight 6–13 g0.2–0.5 oz active by night cave

Sightings by month

White-footed mouse on a fallen log in leaf litter

White-footed Mouse

Peromyscus leucopus

Common in Connecticut 177 sightings
Size 10.1 cm4 in Weight 20–30 g0.7–1.1 oz active by night urban

Sightings by month

White-tailed Deer (Odocoileus virginianus)

White-tailed Deer

Odocoileus virginianus

Common in Connecticut 3,529 sightings
Size 0.9–2.2 m3.1–7.2 ft Weight 68–136 kg149.9–299.8 lb active day & night mixed forest

Sightings by month

Adult wild boar foraging in grass

Wild Boar

Sus scrofa

Marginal occurrence · 9 records
Size 85–90 cm2.8–3 ft Weight 40–50 kg88.2–110.2 lb active day & night lake

Sightings by month

Microtus pinetorum - crlevy - 550023152

Woodland Vole

Microtus pinetorum

Occasional in Connecticut 12 sightings
Size 10.3 cm4.1 in Weight 26 g0.9 oz active day & night woodland

Sightings by month