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shrew shrew

     Insectivores are known from Upper Cretaceous and the oldest members of modern groups (moles, shrews, hedgehogs) are known from the Late Eocene.  Because of the retention of a number of primitive characteristics, insectivores are considered the most primitive placental mammals alive today.   These primitive characteristics include an auditory bulla (the case over the middle and inner ears) which is rarely ossified, a small brain, a cerebrum which is smooth and doesn’t expand over cerebellum, the condition in which some males have testes in the abdomen or inguinal area (as opposed to the scrotum), the possession of a cloaca in some species (a common opening for the urinary, digestive, and reproductive tracts), the lack of opposable digits, and the primitive number and shape of teeth.

      Some of the mammals classified as insectivores are probably not closely related to each other.  Tenrecs and golden moles (both of which exist only in Africa) seem to be more related to elephants, hyraxes, sirens, the aardvark, and elephant shrews (all of which originated in Africa).  Tenrecs and golden moles should be classified with these other groups in a superordinal clade of African mammals rather than with Insectivores (Stanhope, 1996).

 

FAMILY SORICIDAE  

SHREW SHREW
     Masked shrews (Sorex cinereus) can be active in both day and night.  They feed on insects and other small animals, typically eating more than their own body weight each day.  Their heart rate and respiratory rate can reach 1200 per minute. 
MASKED SHREW  
     Smoky shrews (Sorex fumeus) feed on insects and other small animals.
SMOKY SHREW  
     Longtail shrews (Sorex dispar) feed on insects and other small animals.
LONGTAIL SHREW
     Northern water shrews (Sorex palustris) live in aquatic environments where they feed on small aquatic animals, including some fish.  They can swim well.
SHREW

     Least shrews (Cryptotis parva) feed on insects and other small animals and may consume more than their own body weight each day.

SHREW

     Shorttail shrews (Blarina brevicauda) are active throughout the year, both day and night.  They feed on insects and other small animals and their saliva is poisonous. Shorttail shrews lack external ears (Burt, 1976).

SHORTTAIL SHREW