Bats of Iowa
Vespertilionidae
Myotis septentrionalis (Trouessart)
Northern Myotis
Etymology
Greek: "mys" - mouse; "ous"- ears.
Latin: septentrion "northern."
Appearance
Fur: Yellowish (or reddish) brown above, pale (yellowish) below;
hair-dark base, yellowish brown tip.
Tail membrane: Dark brownish, few hairs.
Calcar: Usually slight keel.
Ears: Long (16+ mm), extending more than 2 mm beyond nostrils when
laid forward, darkish, naked and pointed.
Tragus: Longer than one-half ear length; pointed, not obviously
curved.
Total length: 76-87 mm. Forearm: 32-39 mm. Wingspan: 228-258 mm.
Total weight: 5-9.5 g.
Tooth number and formula: 38 total; I 2/3, C 1/1, P 3/ 3, M3/3.
Confusing Species
Similar in size and appearance to other Myotis; little brown myotis
(M. lucifugus) and Indiana myotis (M. sodalis) have shorter ears «16
mm), shorter and blunter tragi.
Distribution and Status
Overall: From North and South Dakota, southern Canada, and Maine to
Arkansas, Alabama, and Georgia. Iowa: Statewide, but few records
from western counties.
Natural History
Although similar in size and appearance to the little brown myotis,
the northern myotis has a very different lifestyle. It is more of a
forest dweller and, in summer, can be seen foraging for insects over
water and clearings, often flying low under the tree canopies.
Because of its largish ears, the northern myotis is thought to
locate some of its prey on surfaces. Foraging activity begins
shortly after sunset and continues throughout the night, peaking
before midnight and again just prior to sunrise. The little food
data available suggests consumption of a variety of insects,
including several kinds of true bugs, leaf-hoppers, ichneumon wasps,
moths, and flies.
In summer, females primarily utilize forested hillsides, rivers and
streams, and cluster in groups of 50 or more to form nursing
colonies in tree cavities or under loose bark where they give birth
to their young. Occasionally, this species is also found in
buildings. Males usually roost singly, often in tree cavities,
caves, mines, and small caverns in the vicinity of nursery sites.
Most mating probably occurs in fall with uterine storage of sperm
cells until fertilization in spring. Usually a single young is born
in June and the earliest born begin flying by the first week of
July. The nursery colonies disband shortly thereafter; by early
August most individuals have left their summer roosts. In late
summer, some congregation occurs, perhaps associated with mating.
During both spring and fall migration, males and females may roost
in or on the sides of buildings, increasing human contact with the
bats.
Although many migrate southward in the fall, some of both sexes
spend the winter in eastern Iowa caves and mines, hibernating either
singly or in small clusters.
They often locate near the little brown myotis, big brown bat and
eastern pipistrelle.
To maintain Northern Myotis populations in Iowa, there must be
preservation of both summer and winter habitats. This species
requires forest and forest-edge sites in summer, including roost
trees, and caves and mines throughout the year.