Wetland Mammals: Species and Their Roles in Aquatic Ecosystems

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Wetland MammalsSpecies and Their Roles in
Aquatic Ecosystems

• By Patrick Gaskin

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Wetland Fuctions and Values

• Hydrological
• Help control floodwater and erosion
• Contribute to aquifer and groundwater recharge
• Geochemical
• Natural Filters
• Biological
• Provide habitat for fish and wildlife
• Socio-economic
• Support timber production
• Support shellfish production and aquaculture
• Provide water sources for irrigation
• Provide recreational opportunities
• Aesthetic values

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Examples of Various Wetlands
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Wetland use by Mammals

• Feeding
• Shelter
• Source of drinking water

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Importance of Mammals to Wetlands

• Beaver dams flood surrounding land
• Enhance habitat for a variety of wildlife
• Reduce water velocity and erosion
• Reduce the peak and frequency of flooding
• Liberates fertile substrate at the abandonment of
  dam or draining of pond

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Economic Value of Wetland Mammals

• Many types of wetland mammals are harvested
• Sport hunting (deer, raccoons, etc.)
• Fur-trapping (mink, beaver)

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The Origin of Mammals

• Cotylosaurs- Stem reptiles
• Named for their cup-shaped vertebrae
• First appeared in the Pennsylvanian Times
• Anapsid skull type, with no temporal openings on
  side of head
• Pelycosauria
• Also of the Pennsylvanian Times
• Had a synapsid type of skull
• With one temporal opening on either side of the
  head

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Almost to Mammals

• Therapsida- Mammal-like
• Had many advances over the stem reptiles, closer
  to mammals
• Double occipital condyles in the skull
• Thecodont-type teeth
• Heterodont dentition
• Vertical posture of limbs
• Secondary palate present

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On to Mammals

• General Characteristics
• Homeothermic
• Usually viviparous birth
• Young nourished by milk from mother
• Vertical limb posture
• Often covered with hair/fur
• Thecodont teeth with heterodont dentition
• Terrestrial and aquatic
• One group (bats) can fly
• Others have membranes between limbs that allow
  them to glide (flying squirrels and sugar
  gliders)

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Classification of Wetland Mammals

• Kingdom- Animalia
• Phylum- Cordata
• Sub-phylum- Vertebrata
• Class- Mammalia
• Orders- Artiodactyla, Insectivora, Rodentia,
  Lagomorpha, Carnivora

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On to the Representatives

• Order Artiodactyla
• Family Cervidae
• Moose (Alces alces)
• Large North American Ruminant mammal
• Very large, flattened antlers
• 2.5 to 2.7 m in length, stands over 2 m at
  shoulder
• 550 to 700 kg
• Relatively poor eyesight

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• Behavior
• Moose are browsers
• Feed on aquatic vegetation (esp. horsetails and
  pondweed)
• Ruminants
• Four-chambered stomach
• Regurgitate swallowed food to be chewed at a
  later time
• Excellent swimmers
• Can swim up to 6 mph

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Order Insectivora

• Includes two Families
• Soricidae- the shrews
• Talpidae- the moles

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Family Soricidae

• Arctic shrew, masked shrew, Pacific shrew,
  Pacific water shrew, smoky shrew, and water shrew
• Small, mouse-sized insectivores
• Throughout most of North America
• Feed primarily on insects, but also on small
  vertebrates
• Prolific breeders
• Up to 3 litters per year with 2 to 10 young

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Arctic shrew Sorex arcticus

• 10.1 to 12.6 cm
• Fairly aquatic
• Lives in swamps, bogs, marshes, and grass-sedge
  meadows
• Smaller in size than its southern counterparts

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Masked shrew Sorex cinereus

• 7.5 to 11 cm
• Semi-aquatic
• Marshes, moist fields, bogs, moist or dry woods
• nocturnal

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Pacific shrew Sorex pacificus

• 12.9 to 16 cm
• More terrestrial
• Lives in spruce and redwood forests, often found
  along the edges of streams

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Pacific water shrew Sorex bendirii

• 14.7 to 17.4 cm
• Semi-aquatic
• Lives in marshes, along streams, occasionally in
  moist forests
• Largest of the shrews
• Can run on surface of water due to fringed hairs
  on toes that give it buoyancy

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Smoky shrew Sorex fumeus

• 11 to 12.7 cm
• Semi-aquatic
• Lives in various types of moist wooded areas,
  swamps, and along streams
• Will often utilize tunnels made by other small
  insectivorous mammals (other shrews, moles, etc.)

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Water shrew Sorex palustris

• 14.4 to 15.8 cm
• Semi-aquatic
• Lives in an around boulders along mountain
  streams or sphagnum moss around lakes
• Excellent swimmers, with webbed 3rd and 4th toes
• All toes have stiff hairs on the sides to
  increase swimming efficiency

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Family Talpidae

• Moles
• Tiny eyes and no external ears
• Broad spade-like fore feet
• Feed on a variety of insects and other small
  invertebrates
• The star-nosed mole is the only member of this
  family that is adapted to living in muddy wetland
  soils

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Star-nosed mole Condylura cristata

• 15.2 to 21.1 cm
• Semi-aquatic
• Water-proof fur
• Spade-like feet are used as paddles to swim
• Use tail as a rudder
• Hunts in stream bottoms or forages in tunnels
• 22 tentacle-like fleshy projections around tip of
  nose
• These are used in searching for prey, probing and
  navigation

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Order Rodentia

• Four families
• Family Zapodidae- meadow mice
• Family Muridae- mice, rats, voles, muskrats, and
  lemmings
• Family Capromyidae- nutria
• Family Castoridae- beaver

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Family Zapopidae

• Meadow jumping mouse Zapus hudsonius
• 18.7 to 25.5 cm
• Nocturnal
• Semi-aquatic
• Lives in moist fields, marshes, woodlands and
  fields with thick vegetation
• Omnivorous
• Feeds on invertebrates in spring, mostly on
  seeds, green plants and fungi in summer and fall

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Family Muridae

• Cotton mouse, golden mouse, marsh rice rat,
  meadow vole, southern red-backed vole, water
  vole, muskrat, southern bog lemming
• Small to medium-sized rodents
• Active year-round
• Omnivorous
• Feed on fungus, seeds, fruits and vegetation, but
  also terrestrial and aquatic invertebrates as
  well as small bird eggs and young
• Number of litters and young vary among species,
  but generally is fairly prolific

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Cotton mouse Peromysus gossypinus

• 15.2 to 20.5 cm
• Semi-aquatic
• Swamps, moist woodlands, beaches, rocks, and
  brushlands
• Strong swimmers
• Forage and escape predators in water

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Golden mouse Ochrotomys nuttali

• 15 to 19 cm
• Arboreal, but often lives in wetland areas
• Swamps, greenbrier thickets, and rocky hemlock
  slopes
• Excellent climber, uses long tail for balance
• Prevalent golden coloration

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Marsh rice rat Oryzomys palustris

• 18.7 to 30.5 cm
• Semi-aquatic
• Lives mostly in marshes
• Excellent swimmer, can submerge
• Water repellent fur
• Omnivorous
• Subterranean fungus Endogone is important diet
  component

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Meadow vole Mircotus pennsylvanicus

• 14 to 19.5 cm
• Semi-aquatic
• Marshes, swamps, woodland glades and fields
• Good swimmer
• Commonly forages in water
• Active day or night
• Short tails and small eyes of lemmings and voles
  contrasts with mice and rats

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Southern red-backed vole Clethrionomys gapperi

• 12 to 15.8 cm
• More terrestrial
• Cool, damp forests, swamps and bogs
• Swims and climbs well
• Mostly herbivorous
• Primarily fungi, and succulent plants
• Will forage on invertebrates

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Water vole Arvicola richardsoni

• 19.8 to 26.1 cm
• Semi-aquatic
• Upland creek and stream banks and marshes
• Strong swimmer
• Burrows along stream banks
• Lives in colonies
• Lives in SE and SW British Colombia and Alberta,
  also in eastern Washington and Oregon, northern
  Idaho, central Utah and western Wyoming

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Southern bog lemming Synaptomys cooperi

• 11.8 to 15.4 cm
• Mostly terrestrial
• Burrows about 6 inches below ground, also other
  animal burrows
• Lives in grassy meadows, but occasionally bogs,
  always in areas with heavy vegetation
• Will forage algae and other aquatic vegetation

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Muskrat Ondatra zibethicus

• 40.9 to 62 cm
• Marshes, and edges of ponds, lakes, rivers and
  streams
• Aquatic rodents
• Hind feet partially webbed and flattened
• Long scaly tail used for swimming
• Build cone-shaped houses out of vegetation
• May live together communally during cold weather
• Feed on aquatic vegetation
• Roots and shoots of cattail and other emergents,
  but also clover, fruits and occasionally aquatic
  invertebrates
• Valvular mouth allows them to feed underwater
• Glands near anus produce musky odor
• Water-proof fur, and valuable skins

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Muskrats continued

• Muskrats are instrumental in the Marsh-cycle
• As muskrats feed, they create openings in marshes
  with dense, emergent vegetation
• Create random openings initially
• Can consume most of the vegetation and return the
  marsh to an open state if left unregulated

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Family Capromyidae

• One species Nutria
• South American rodents, escaped or introduced
• Have been introduced in 22 states across the US
• Well-established in areas of the southeast,
  especially Louisiana
• Foraging and burrowing activities can have
  detrimental effects

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Nutria Myocastor coypus

• 67 to 140 cm
• Semi-aquatic
• Feeds on aquatic vegetation
• builds nests of vegetation on the surface of
  water
• Excellent swimmer
• Found in marshes, ponds, swamps, and lakes

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Family Castoridae

• One species Beaver Castor Canadensis
• Largest living rodents in North America
• Range over most of Canada and the US
• Construction of dens often dams rivers and
  streams, flooding surrounding land
• Beaver presence can have a huge impact of the
  state and stability of a particular wetland
• Can enhance habitat
• Herbivorous
• Feed mostly on tree bark and green twigs

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Beavers continued

• 88.9 to 131.3 cm
• Aquatic
• Webbed feet, rudder-like tail, nictitating
  membrane over eyes, valvular ears, nose and
  mouth, fur contains water-repellent oil
• Build stick and mud lodges that dam rivers and
  streams
• Used for denning and food caching

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Order Lagomorhpa

• One Family Leporidae
• Marsh and Swamp rabbits
• Similar to cottontail rabbits, but are associated
  with bottomland hardwood forests of the southeast
  US
• Have smaller ears
• Good swimmers
• Will take to the water when threatened
• Also forage wetland plants
• Restricted to the southeast coast in wet
  bottomlands and wetlands

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Marsh rabbit Sylvilagus palustris

• 35 to 45 cm
• Semi-aquatic
• Wet bottomlands, swamps, hummocks, lake borders
  and coastal waterways
• Good swimmer, will flee predators by taking to
  water
• Herbivorous
• Forages on wetland and terrestrial vegetation

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Swamp rabbit Sylvilagus aquaticus

• 53 to 54 cm
• Semi-aquatic
• Good swimmer
• Swamps, marshes, wet bottomlands and canebreaks
• Can cause damage to crops near swamps

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Order Carnivora

• Two families
• Mustelidae- Mink and Otters
• Procyonidae- Raccoons
• Semi-aquatic
• Forage in and around wetlands for plant and/or
  animal matter

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Mink Mustela vison

• 49.1 to 72 cm
• Semi-aquatic
• Excellent swimmers
• Water-proof fur
• Forages in water, feeding on crayfish, frogs, and
  fish, but also small mammals and birds
• Releases musk from scent glands in anal region
  when agitated
• Were the first American furbearers to be raised
  in captivity due to their valuable furs

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River otter Lutra canadensis

• 88.9 to 131.3 cm
• Semi-aquatic
• Excellent swimmers, catch prey in water
• Webbed feet, stream-lined bodies, and dense oily
  underfur
• This dense oily underfur limits the market value
  of their pelts
• Carnivorous
• Feed on fish, crayfish, herps, and some
  vegetation
• Sociable
• Often play together, chasing each other, and
  repeatedly sliding down slopes into the water

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Family Procyonidae

• Raccoon Procyon lotor
• 61 to 91 cm
• Semi-aquatic
• Excellent swimmers
• Slight webbing of toes
• Forage in and around water
• Very intelligent
• Problem solving skills often allow for detection
  of traps
• Omnivorous
• Fruits, grains, and vegetation, also fish,
  shellfish, herps, small mammals and birds
• Can be destructive
• Destroy all or parts of corn and other crops
• Kill poultry and raid nests

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Predator-Prey Relations

• Although they are often the predator, raccoons
  can find themselves on the prey side of the food
  chain

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Other mammals

• Other mammals that frequently visit wetlands
• Black bears
• Often wade into streams and lakes to forage on
  animal and plant foods
• White-tailed deer
• Will forage a variety of aquatic vegetation, as
  well as seek cover in wetland areas

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Habitat management for wetland mammals

• Generally directed toward a specific wildlife
  species
• Can be aimed at increasing the overall
  biodiversity of wetlands
• Successful efforts usually increase seed sources,
  invertebrate populations, and other wetland
  mammal foods