Mammalogy Lab 2: Didelphimorphia and Soricomorpha ...goheen/mammalogy course/lab--2... · Mammalogy...
Transcript of Mammalogy Lab 2: Didelphimorphia and Soricomorpha ...goheen/mammalogy course/lab--2... · Mammalogy...
Mammalogy Lab 2: Didelphimorphia and Soricomorpha (opossums, shrews and moles)
Order Didelphimorphia, Family Didelphidae—American opossums Virginia opossum—Didelphis virginiana
1) dental formula = I5/4 C1/1 P3/3 M4/4 2) prominent sagittal crest 3) fenestrated palatines 4) angular process medial from mandible
Didelphis virginiana
• Up to 25 young in a litter • 2g at birth • ~ 3 months in the pouch • ~ 8-9 young emerge
• Only species in the Didelphidae that ranges north into the US & Canada
• Omnivorous – insects, beetles, small mammals and birds, grain, berries and fruits, grass, carrion…garbage!
Order Soricomorpha, Family Soricidae—shrews
1) incomplete zygomatic arches 2) at least some teeth tipped with red or black 3) cheek teeth dilambdodont 4) bicuspid I1
Soricidae • Need to eat every few
hours – very fast metabolism
• Eat twice their own body weight daily!
• Rarely live longer than 18 months
• Several large litters • Red on teeth is iron –
differential wear creates sharp cutting edges
pygmy shrew—Sorex (Microsorex) hoyi
1) only 3 unicuspids readily visible from side
1 2 4
• Smaller (1-3g) in southern parts of range • Larger (4-7g) in Alaska and Northern regions • Variable habitat – open fields to wooded slope; wet
and dry soils
Sorex hoyi
• Range across Canada and northern USA
• Quite rare – abundance underestimated due to trapping methods? (pitfall traps better than typical small mammal traps)
water shrew—Sorex palustris
1) skull length > 19 mm 2) rostrum short, relative to S. bendirii
Pacific water shrew—Sorex bendirii
1) skull length > 19 mm 2) rostrum longer and more downcurved,
relative to S. palustris
Sorex bendirii
Sorex palustris
Adapted for swimming – stiff hairs on feet increase SA for aquatic propulsion.
arctic shrew—Sorex arcticus masked shrew—Sorex cinereus tundra shrew—Sorex tundrensis
1 2 3 4
1) 3rd unicuspid not smaller than 4th
Sorex arcticus
• Range: most of Canada – NE BC • Tri-colored pelage – dark back, lighter
sides and venter • Aquire tricolored
pattern at first Autumn moult, and retain it throughout life
Sorex tundrensis
• Range: Alaska, NW Canada, and extreme NW BC
• Summer coat tricolor – winter coat bicolor – retain dark back, sides take on similar light color to venter
Sorex cinereus
• Range – Alaska, most of Canada and USA
• Largest distribution of any N American shrew
• 9 subspecies recognised
dusky shrew—Sorex monticolus Trowbridge’s shrew—Sorex trowbridgii
vagrant shrew—Sorex vagrans
1) 3rd unicuspid smaller than 4th
4 3
Sorex monticolus
• Range – throughout BC; found in Alaska, W Canada and through W USA.
• Prefers wet areas; willow and alder thickets, grassy stream banks and alpine tundra
Sorex vagrans
• Range – S BC and W USA • Found in wet, grassy areas, marshes and
muddy streams
Sorex trowbridgii • Range: Extreme SW BC; along Pacific coast to California. • Usually the most common shrew found in forests of the
Pacific NW USA • Prefers mature forest – avoids wet, marshy soil
• Has been observed climbing high into Douglas Fir trees!
Order Soricomorpha, Family Talpidae—moles
1) complete zygomatic arches 2) teeth entirely white
Talpidae
• Fossorial – reduced eyesight – no pinnae – front feet modified
for burrowing – fur lies either way
shrew-mole—Neurotrichus gibbsii
1) dentition: I3/3 C1/1 P2/2 M3/3 2) auditory bullae incompletely formed
coast mole—Scapanus orarius
1) dentition: I3/3 C1/1 P4/4 M3/3 2) auditory bullae completely formed 3) skull < 37 mm
coast mole—Scapanus orarius
Townsend’s mole—Scapanus townsendii
1) dentition: I3/3 C1/1 P4/4 M3/3 (usually) 2) auditory bullae completely formed 3) skull ≥ 37 mm
Townsend’s mole—Scapanus townsendii