SHOULD WE DO ABOUT BENIGN EXOTICS?
introduced plants and animals such as fire ants and kudzu are classified
as disruptive invasive species. In contrast, other well-known species
not native to America such as apples and honey bees are viewed favorably
and considered part of our culture.
between are species that are considered neither detrimental nor beneficial;
they do no apparent harm to people or native wildlife. I recently received
questions about two of these benign exotic introductions.
Can you identify a creature I found crawling across my sidewalk? It
looks like a soft and slimy yellowish worm with black stripes down the
body and an arrow-shaped head. I've never seen anything like it before.
Is this some kind of invasive species? Should we destroy any that we
That is a type of flatworm known as a land planarian or greenhouse flatworm.
Several species are known. One that is common in many areas was introduced
into the United States from Asia more than a century ago.
stretch out to be over a foot long. They require moist conditions and
are predatory on earthworms. They are slimy to pick up but do not bite
or sting. They also can leave a shiny, silvery trail where they have
lay eggs but also can reproduce by breaking off the rear portion of
the body and crawling forward, leaving the end piece sticking to the
ground to become another individual. Thats bizarre enough, but
they also have no circulatory or respiratory system, no legs and no
external or internal skeleton. They are so abundant in New Orleans that
a colleague of mine caught land planarians for lab demonstrations in
zoology classes at Tulane University.
are ubiquitous in warm, humid habitats and have been around for decades,
trying to get rid of them is probably not worth the effort. Im
not aware that they do any harm environmentally, aside from eating a
lot of earthworms.
farmers and greenhouse owners, where earthworms are important for soil
aeration, would disagree that they cause no harm and might want to eliminate
them. Ironically, however, most earthworms are not native to America
either, so whos to say that land planarians shouldnt be
here also? Plus they are kind of cool creatures to show off to folks,
as my grandsons often demonstrate when they discover one in the backyard.
I live in southern Georgia and am wondering what kind of gecko I keep
seeing. They are all over my yard, house and garage. They are super
That is a Mediterranean gecko, one of our most widespread nonnative
lizards. They are recognizable by the small tubercles visible all over
the body and tail.
first reported in the United States in Key West, Florida, in 1910, probably
introduced from cargo ships. They have made their way from southern
Florida into urban areas in many parts of the South and Southwest over
the last century, generally as an unseen hitchhiker on vehicles.
geckos live around man-made structures, so they have little or no impact
on natural habitats or native wildlife. They come out mainly at night
and are especially prevalent around houses or buildings in the vicinity
of an outdoor light.
To my knowledge,
they are totally inoffensive not only in regard to our picking one up
but also to pets. One neat feature is that during their breeding season
the eggs are visible inside the body of females. Mediterranean geckos
are indisputably interesting little animals to have around.
many other benign introductions from other continents that live around
us and cause no appreciable environmental harm. In fact, the number
of nonnative species that thrive here now exceed the number of native
representatives of some taxonomic groups in many regions. And the disproportionate
ratio of exotic to natives continues to grow. We might as well learn
to enjoy them.
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