Wildlife
Alien / Invasive Species
Island
Dilemma
Since the beginning of time, islands have developed their
own sets of plants and animals – a web of life more fragile than on more
complex mainland areas. Threads of that web quickly and devastatingly break when
new animals, especially predators, are added to the islands – by accident
or design.
The following are some of the alien or non-native animals that
have invaded some of the island ecosystems of the Alaska Maritime Refuge.
Foxes
The first recorded introduction of alien wildlife was of
foxes in 1750 when Russians brought arctic foxes (Alopex lagopus) to Attu
Island (western end of the Aleutians) from the Commander Islands of Russia. The
Russians were already hunting sea otters for their fur and wanted a source for
additional fur. Farming for fur continued until World War II.
Foxes feast on the abundant seabirds, waterfowl, ptarmigan, and songbirds that evolved
on these islands without defenses against such voracious predators. They have
wiped out some populations of island birds and endangered others. The refuge worked
almost 40 years to return the Aleutian
cackling goose to safety.
Rats
In 1780 rats escaped
from a sinking Japanese fishing boat on the western Aleutian Island later named
"Rat Island." This incident began a series of "rat spills"
that proved more deadly than oil spills to island ecosystems including island-nesting
birds – rats crawl into nesting burrows and along narrow cliff ledges, stealing
eggs and killing chicks and adults.
Rats continue to be a plague on island
wildlife today. The refuge has a shipwreck
response program to prevent new rat invasions and is developing a program
to fight rats already on islands.
Reindeer / Caribou
Reindeer
and caribou belong to the same species. Reindeer are the domesticated form native
to Europe and Asia. Caribou are native to most of Alaska, including a few coastal arctic areas of the refuge
and along the Alaska Peninsula.
Caribou or reindeer were introduced to
some refuge islands, especially as a source of emergency food or recreation for
remote military outposts – now abandoned.
On an island without human
or animal predators, a herd can grew so quickly and so large that it destroys
its own food source and changes the island’s normal plant and soil stability
balance. That happened on St. Matthew Island. Learn
more. The refuge has encouraged removal of introduced reindeer and
caribou herds in their entirety or by hunting.
Cattle
Domestic cattle were dropped off on several
refuge islands off the Alaska Peninsula, starting in the late 1800s. Sometimes
farmers stayed nearby, but often the cattle were left to fend for themselves.
Like caribou and reindeer, the grazing and trampling of cattle changes
an island’s plant and soil balance – causing erosion and crushing nesting
burrows of seabirds such as tufted puffins and storm-petrels. Without the normal
lush grass cover to hide their nests, ducks, geese, gulls, and terns stop nesting
on these islands.
In the 1980s, the refuge removed cattle from several islands
to restore the plants and encourage recovery of native birds. Lush native grasses
have stabilized the sand dunes and stream banks of Simeonof Island a decade after
cattle removal. Cattle remain on several other islands.
Ground Squirrels
After
1819, when the Russian-American Company encouraged adding foxes to islands, fur
trappers released ground squirrels to provide food for the foxes. Only they forgot
that ground squirrels hibernate in winter, the lean time for foxes.
Some
ground squirrels eat bird eggs and chicks, especially those of puffins. Burrow
nesting seabirds are now scarce on islands with alien ground squirrels.
Last updated: January 26, 2009
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