Rodent Natural History, Identification and Care Class

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Rodent Natural History, Identification and Care
Class

• Pam Nave and Jean Yim
• Lindsay Wildlife Museum
• January 2004

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Topics

• Natural History
• Identification
• Set-up and Care

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Gnawing MammalsOrder Rodentia

• Characterized by having only 2 incisors above and
  2 below with a distinct space between the
  incisors and the grinding teeth.
• Kinds of rodents include
• Beavers, squirrels, chipmunks, gophers, mice,
  rats, voles and porcupines

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Rodents Commonly Brought to Lindsay Wildlife
Museum

• Native Rodents
• California Vole
• Deer Mouse
• Dusky-footed Woodrat
• Valley Pocket Gopher
• Western Harvest Mouse

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Rodents Commonly Brought to Lindsay Wildlife
Museum

• Non-native Species
• House Mouse
• Norway Rat (Sewer Rat)
• Black Rat (Roof Rat)
• Old World species introduced from Europe

House Mouse
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Rodents Commonly Brought to Lindsay Wildlife
Museum

• Squirrels
• California Ground Squirrel
• Western Gray Squirrel
• Eastern Fox Squirrel

Fox Squirrel
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Other Rodents in the San Francisco Bay Area

• Brush Mouse
• California Mouse
• California Pocket Mouse
• Piñon Mouse
• Salt Marsh Harvest Mouse

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Species Sometimes Confused as Rodents

• Order Insectivora
• Shrews
• Ornate Shrew
• Trowbridge Shrew
• Broad-footed Mole

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Natural History

• Native
• Valley Pocket Gopher
• Western Harvest Mouse
• Deer Mouse
• Dusky-footed Woodrat
• California Vole
• Introduced
• Norway Rat
• Black Rat
• House Mouse

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Rodent Natural History

• Tend to be nocturnal
• High fecundity
• Often several litters produced in one year
• Necessary because of estimated 95 annual
  mortality
• Deer mice
• Few deer mice live beyond a year due to predation
  pressure, climatic hardships and natural
  mortality
• (Life expectancy in captivity has sometimes
  exceeded 8 years.)
• Deer mice breed at 5-6 weeks, 2-4 litters of 3-5
  young a year

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Valley Pocket Gopher

• Range throughout California and western US
• Throughout range, extremely variable in size and
  coloration (range from nearly white to nearly
  black)
• Adapted to subterranean living
• External cheek pouches
• Incisor teeth always exposed when mouth is closed
• Front claws large and curved for efficient
  digging tools
• Eyes and ears small
• Skin loose, can turn easily in tunnels
• Solitary much of their lives, active day and
  night throughout the year

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Valley Pocket Gopher

• Presence of pocket gophers easily identified by
  fan-shaped mounds of dirt
• Dont leave their burrows open for long
• Seldom seen aboveground
• Prefer soil that is moist and easy to work
• Feed largely on roots and tubers as well as some
  surface vegetation
• Sometimes comes above ground to forage but often
  pull plants down through surface soil into burrow
  system
• Important soil-forming agents
• Bring subsoil to surface
• Aid in conservation of water and aeration of soil

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Western Harvest Mouse

• Range throughout California from Pacific Coast
  to Great Lakes
• Habitat Grassland, open desert, weed patches
  usually in dense vegetation and near water
• Nocturnal and crepuscular but more active on
  moonless and rainy nights
• Makes use of ground runways of other rodents
• Nimble climber
• Birdlike nests of woven dried vegetation are
  usually on surface of ground in thick grass or
  weeds or at base of shurbs and frequently lined
  with fine grasses or down

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Western Harvest Mouse

• Primarily seedeater
• In spring, also eats new growth from ground and
  bushes
• In summer, insects, especially grasshoppers, and
  fruit
• Search and consume foraging strategy
• Stores surplus food, such as seeds, in
  underground caches
• Adapted to aridity, capable of extreme urine
  concentrations and can exist on saline water

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Deer Mouse

• Range North American dry lands, widely
  distributed
• Habitat Burrows, hollow logs, decayed tree limbs
  and roots
• Reduces predation by constructing burrows under
  snow
• Owls can hear them and punch through the snow to
  capture them
• Foxes can smell them and dig them out
• Strong homing instinct will travel more than a
  mile to return to native range
• Renowned climber
• Named because fur similar to that of a deer (soft
  pelage of long, dark-tipped guard hairs)

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Deer Mouse

• Due to small size and high energy requirement,
  must stay active all winter
• Generalist seeds, nuts, acorns, insects
• Ferocious appetite
• Can consume own body weight in 24 hours
• Food storage critical to survival
• Caches scattered near nest and surrounding
  territory can contain up to one gallon of seeds
  during times of abundance

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Dusky-footed Woodrat

• Range throughout California
• Habitat Heavy chaparral, streamside thickets,
  deciduous and mixed woods
• Feeds on variety of seeds, nuts, acorns, fruits,
  green vegetation, fungi
• Stores food in house near nest
• Builds large stick houses on ground or in trees

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California Vole

• Range Widespread and common in California
• Occurs in wide variety of habitats
• Meadows and grasslands with viable soil, marshy
  ground, saltwater and fresh wet meadows, dry
  grassy hillsides, seashore to mountains
• Territorial behavior weak
• Presence often detected by narrow runways, 1-2
  inches, through matted grasses
• Seeks cover in dense grass, beneath plant
  residues, in brush piles, beneath logs and in
  underground burrows. Burrows are constructed in
  soft soil.
• Nest of dried grass is built in a shallow
  underground burrow
• Breeds throughout the year, reaching peaks
  whenever food and cover are abundant

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California Vole

• Feeds mainly on leafy parts of grasses, sedges
  and herbs
• Forages on ground
• In winter, eats mostly roots and other
  underground parts of plants
• Drinks water in captivity, but under natural
  conditions water can be obtained from succulent
  vegetation
• Active by day as well as by night
• Abundance and widespread distribution along with
  daylong activity makes it an important prey
• Predators include nocturnal (owl) and diurnal
  (hawks) birds of prey, predatory mammals (incl
  weasels) and snakes

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Norway Rat

• Range throughout the continent where people are
  concentrated
• Colonial. Burrows along foundations of buildings
  or beneath rubbish piles
• Feeds on anything edible

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Black Rat

• Range Chiefly seaports has been reported as far
  inland or Urbana, Illinois
• Black and brown color phases
• Lives mostly on tops of buildings, does not
  require soil to burrow into

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House Mouse

• Range throughout continent where people are
  concentrated
• Occasionally found in fields, but usually in
  buildings
• Eats anything edible
• Breeds year round

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Rodent Identification

• Key
• Mammal Field Guides
• Overall Impression
• Gestalt
• Jizz (general impression and shape)
• Photographs
• Mounts

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Dichotomous Key

• Organizes animals by sharply distinguished
  classifications
• Key for Adult Rodents
• Key for Naked or Slightly Furred Rodents
  (Subjective because animals still developing
  requires knowledge of adult sizes and
  characteristics)

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Key p1
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Key p2
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Key p3
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Use of Key

• 2. Head large and muzzle distinctively blunt
  (Squirrels). . . . . . . . . .
  . . . . 11
•  
• 2a. Head small and muzzle somewhat pointed. .
  . . . . . . . . . . . . .
  . . . 3

Fox Squirrel
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Use of Key

• 3. Dorsum and venter similar color all around.
  . . . . . . . . . . . .
  . . . . . . 4
• 3a. Venter significantly lighter than dorsum,
  definite demarcation along side. . . . .
  . . 10
• 4. Tail very short (Mole, Gopher, Vole). . .
  . . . . . . . . . . . . .
  . . . . . . . 5 
• 4a. Tail long (Rats, Mice). . . . . .
  . . . . . . . . . . . .
  . . . . . . . . . 7

Norway Rat
Deer Mouse
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Use of Key

• 3. Dorsum and venter similar color all around.
  . . . . . . . . . . . .
  . . . . . . 4
• 3a. Venter significantly lighter than dorsum,
  definite demarcation along side. . . . .
  . . 10
• 4. Tail very short (Mole, Gopher, Vole). . .
  . . . . . . . . . . . . .
  . . . . . . . 5 
• 4a. Tail long (Rats, Mice). . . . . .
  . . . . . . . . . . . .
  . . . . . . . . . 7

California Vole
Western Harvest Mouse
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Judging Rodent Ages

• Most born naked
• Determine how well-furred animal is
• Dusky-footed Woodrat born furred
• Umbilicus falls off at about 7 days
• Eyes open at 10 days
• Important to know approximate age when
  identifying
• Adult vs Immature size can be very different

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Use of Key

• 7.(4a) Total length large (Black and Norway Rats
  are more developed at a smaller size). . . 8
•  
• 7a. Total length small, head pointier (Mice).
  . . . . . . . . . . . . .
  . . . . . 9

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California Vole

• Short tail
• Bi-colored tail
• Adult head and body length 120-143 mm
• Adult wt 42-100 g

BW 4.9 g
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Valley Pocket Gopher

• External cheek pouches present
• Tail shorter than head and body
• Adult head and body length 122-178 mm
• Adult tail length 51-95 mm
• Adult wt 71-250 g

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Deer Mouse

• Highly variable color morphs
• Pale grayish buff to deep reddish brown
• Sharply bicolored tail
• Adult head and body length 71-102 mm
• Adult tail length 51-127 mm
• Adult wt 18-35 g

BW 8.3 g
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Deer Mouse

• Widely distributed throughout North America
• Highly variable color morphs

• Even when naked, can see definite demarcation of
  dark dorsum and light ventrum in skin

BW 2.0 g
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Western Harvest Mouse

• Brownish above, buffy along sides, whitish below
• Indistinctly bicolored tail
• Adult head and body length 71-76 mm
• Adult tail length 59-81 mm
• Adult wt 9.1-21.9 g

BW 1.8 g
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Western Harvest Mouse

• Young tend to be buffy in color
• Distinctive black line where eye will open

BW 2.1 g
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House Mouse

• Grayish-brown with gray or buffy belly
• Tail same color all around
• Adult head and body length 81-86 mm
• Adult tail length 71-97 mm
• Adult wt 11-22 g

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Comparison of Western Harvest Mouse and House
Mouse

• Easily confused with the non-native House Mouse
• Mature more slowly than House Mouse therefore
  young and immature will have rounder (less
  pointy) snout than House Mouse

House Mouse
Western Harvest Mouse
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Dusky-footed Woodrat

• Body grayish brown above, whitish below
• Hind feet sprinkled on top with dusky hairs
• Adult head and body length 193-229 mm
• Adult tail length 173-220 mm
• Adult wt 227-390 g

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Dusky-footed Woodrat

• Born at 15-18 g
• Furred when born
• 1-3 babies per litter
• Young are grayish above and molt into a brownish
  pelage when older

BW 17.3 g
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Norway Rat (Sewer Rat)

• Ventrum and dorsum color similar
• Tail not as long as head and body
• Adult head and body length 178-254 mm
• Adult tail length 127-203 mm
• Adult wt 200-283 g

BW 19.7 g
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Black Rat (Roof Rat)

• Can be black or brown
• Ventrum and dorsum color similar
• Tail longer than head and body
• Adult head and body length 178-203 mm
• Adult tail length 214-253 mm
• Adult wt 142-283 g

BW 15.9 g
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Comparison of Adult Black Rat and Norway Rat

• Black Rat
• Tail longer than head and body
• Black Rings on Tail
• Slender
• Muzzle pointed
• Eyes large
• Ears large and can be pulled over eyes

• Norway Rat
• Tail not as long as head and body
• Tail lacks rings
• Stocky
• Nose blunt
• Eyes small
• Ears small and do not reach eyes when pulled
  forward

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Comparison of Black Rat and Norway Rat
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Comparison of Black Rat and Norway Rat Tails
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Comparison of Naked Black Rat and Norway Rat

• Black Rat
• Tail about ¾ length of body

• Norway Rat
• Tail about ½ length of body

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Woodrat vs Norway Rat
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Woodrat vs Old World Rats

• Old World Rats sometimes have very light ventrums
• Demarcation of dark dorsum (back) and light
  ventrum (abdomen) more defined in Dusky-footed
  Woodrat

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Rules Arent Always Black and White

• Very confusing!

Dusky-footed Woodrat
Black Rat
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How to Set-up

• Immature and Adults
• Mice and Voles
• Rats
• Native baby mice and voles
• Neonates with nursing mother domestic mouse
• Domestic Mice

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SPF Mice

• Specific Pathogen Free Mice
• Not free of all pathogens
• We know they are free of bad ones
• Nursing mothers used as surrogate mothers for
  wild mice
• Assure health of the wild mice population
• Colony can be used as food

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Where to Find Information

• What We Know Book
• Natural History
• Identification
• Written descriptions
• Key
• Mammal Field Guides
• Immediate Care Book
• Mounts in staff office
• Western Harvest Mouse
• House Mouse
• Examples of different species in carcass freezer
  in hallway
• Holding Room
• How to set-up domestic mice
• Photos at http//www.escape.org/lwm/gallery/