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Rustling winter leaves may not
excite the average Missourian, but
the sound sends Dr. Lynn Robbins
running to investigate. Recently
Robbins, a Missouri State University biology
professor, heard crunching leaves
while surveying the university
field station in Taney County. He
discovered a scrawny armadillo
sniffing its narrow snout in
search of food.
One week after this winter's snow melted, Robbins saw the
armadillo at the Bull Shoals Field Station, a center for research and
education in an outdoor setting. The Field Station is located on the western
end of Bull Shoals Lake and adjacent to the 6,000-acre Drury-Mincy Conservation
Area. Missouri State faculty, graduate students and visiting scientists conduct
research here throughout the year. Robbins spotted three other skinny
armadillos that day while working at the Field Station. All were slow
to react to the presence of humans, which he attributes to the animals'
lack of energy.
Armadillos are found throughout southeast and southcentral
regions of the United States, currently as far north as Missouri. They
first arrived in Missouri in the early 1980s. Southern Missouri had an
abundant population last summer, but biologists suspect the harsh winter
may have significantly reduced their numbers. Robbins was surprised to
find the animal because research shows armadillos should not have survived
the severe conditions of this past winter.
Armadillos cannot tolerate cold climates, limiting their
ability to live far north. The arid climate of the west is also insufficient
because the soil is not moist for digging and burrowing.
Compared to other mammals, armadillos have relatively low
body fat, which limits their ability to maintain body temperature. To
burn calories and stay warm, they need to eat a lot of insects, larvae,
ants and beetles (and occasionally a snake or lizard). Winter temperatures,
ice and snow limit the armadillo's ability to forage for these soil-dwelling
prey. Their acute sense of smell and long claws are useless for digging
frozen or snow-covered ground.
They also keep warm using "reta mirabila," a system of veins
and arteries in the legs. Hot blood leaving the body, going into the legs,
is cooled by cold blood coming back into the body and vice versa. Cold
weather means frostbite is more likely for these already cooler extremities.
Robbins is conducting a statewide survey to determine whether
the serious winter conditions had a negative impact on the distribution
and abundance of armadillos in Missouri. He is sending surveys to biologists,
conservationists, land specialists and state agency officials asking them
to record armadillo sightings. The same survey will be distributed again
in fall 2001, and final results will be available in summer 2002.
If results show a high frequency of armadillo sightings,
Robbins says he will not immediately conclude that the winter had little
effect on the population. Armadillos that survive will be hungry and will
come out to hunt more frequently, which makes them more likely to be seen.
People may report seeing several armadillos although they actually see
the same animal more than once.
Although research suggests armadillos are unlikely to have
lived through the winter, Robbins is optimistic that the population will
recover because of the peculiarities of armadillo reproduction.
A female armadillo gives birth to four identical young
developing from the same fertilized egg. After her egg is fertilized,
she may delay implantation if environmental conditions are stressful.
Surviving female armadillos are likely to be weak and may wait to begin
pregnancy, giving future generations a better chance to survive.
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Bull
Shoals Field Station
