By: Morgan Osborn, Texas A&M WFSC '16
Learning
from past mistakes, the Department of Natural Resources in many New England
states including Michigan and Rhode Island is trying to nip a new potential
epidemic of an invasive non-native species in the bud. The feral
hog
epidemic, introduced in the 1500s, is at an all-time high in the multimillions.
If we knew five hundred years ago what we know now, would feral hogs be at such
alarmingly high rates across the globe? Here’s our chance to find out! A mere century
and a half ago, mute swans (Cygnus olor)
were introduced to the United States from Eurasia and have several potentially
alarming similarities to feral hogs.
How can one compare
dirty pigs to these magnificently sophisticated waterfowl? However, that is exactly
what they are: foul. Mute swans, much
like feral hogs, can be rather dirty as they indiscriminately defecate and
introduce their fecal coliform filled scat into the water, raising concerns to
their impacts on water quality (Swift et al. 2013). Drinking water,
recreational water, and fishing water are all put into more distress as water
quality decreases. Correlation between these two insidious invasives continues
with the depletion of native resources in areas of inhabitation. These less
than graceful creatures do not migrate and have been reported as eating over
3.8 kg of the aquatic plants they don’t trample (Reese, 1975). That’s over 8
pounds of aquatic vegetation each day! With these prolific pests eating so much
vegetation year round, many fear that the vegetative community may be altered
causing a depletion of food sources for other waterfowl and cover for fish
and aquatic vertebrates and
invertebrates. Swift et al. (2013) found, through a preliminary short study,
mute swans consumed 70-80% of the aquatic vegetation within study plots.
Although feral hogs are much larger and stronger, both can be aggressive. Mute
swans, which can grow up to 35 pounds, have been noted forcefully removing
other birds and fowl from their territory in both mating and non-mating seasons
(Allin, 2014). Some have even been documented attacking chained dogs that were
just a little bit too close or a child who had no food left to spare (Allin,
2014). Damage to infrastructure is often noted with feral hogs. However,
generally one doesn’t think a bird is capable of such force or damage. Contrary
to this belief, mute swans often crash into power lines due to their poor
vision, causing power outages (Allin, 2014).
Potential differences
between the increasing spread of mute swans and feral hogs are favorable areas
of habitation and reproduction rates. While feral pigs prefer certain habitats
over others, they can survive just about anywhere. This allows feral hogs to
spread very easily as most terrain can be suitable. For the most part, non-migrating mute swans
are located in the middle part of the Atlantic Flyway, a migratory area located
on the eastern coast (Swift et al. 2013). However, according to the Museum of
Zoology at the University of Michigan, they have the potential to live in many
different areas ranging from saltwater to freshwater with all the marshes,
ponds and streams in between (Ivory, 2002). This poses a potential problem
similar to that of the feral hog. Feral hogs have the potential to breed after
only six months of age but usually don’t have their first litter until around a
year or later when they have on average 5-6 piglets per litter around 1.5 times
a year according to Texas
A&M AgriLife Extension
Service. In
contrast, mute swans do not mature until at least three years of age when they
can have an average of 5-7 young, known as cygnets, which take up to twelve
months to achieve independence (Ivory, 2002).
What next? We’ve identified the problems. Now, let’s find
some solutions. Get rid of the swans in some form or fashion. Sounds simple,
right? The visual and emotional attachment of people to these swans is
hindering some efforts (Reese, 1975). One business journalist in New York,
representing a presumed to be large proportion of the population, disparages
the efforts to alleviate pressures presented by the elegant and beautiful swans
on the habitats they occupy (Ghosh 2014). People find it easier to try and
remove feral hogs, because they aren’t aesthetically pleasing and are hunted
for food and sport. On the opposite side of the spectrum from the business
journalist, a food editor from Los Angeles wrote a post discussing the
implications of eating the birds which used to be feasted on by royalty
(Blackmore 2014). Although mute swans are not yet considered game, they are no
longer protected by the Migratory Bird Treaty Act and are left to the devices
of each state (Swift et al. 2013). If the state and national parks and
Department of Environmental Management can’t control the populations as well as
they hope, will we see mute swans becoming a popular game bird? Will they
become as bountiful as feral hogs, if they continue to be so successful? Within
the next few decades, we may either see increased control over the situation or
feasting on mute swans to assuage a potential wetland famine left in their
paths.
The hyper-linked resource document below will provide you with quick access to many of our online feral hog resources including publications, fact sheets and videos.
Works Cited
Allin, Charles C.
"Mute Swan An Invasive Species And Its Management In Rhode Island."
Rhode Islande Department of Environmental Management, n.d. Web. 14 May 2014.
Blackmore, Willy.
"Should Swan Be on the Dinner Menu?" TakePart. N.p., 12
May 2014. Web. 14 May 2014.
"Coping with Feral Hogs." Frequently Asked Questions-Wild
Pigs. Texas A&M AgriLife Extension, n.d. Web. 14 May 2014.
"DNR - Frequently
Asked Questions About Mute Swans." DNR - Frequently Asked
Questions About Mute Swans. Michigan Department of Natural Resources, n.d.
Web. 14 May 2014.
Ghosh, Palash. "NY
State Plans To Exterminate Mute Swans, Calling Them 'Invasive
Species'" International Business Times. N.p., 31 Jan. 2014.
Web. 14 May 2014.
Ivory, Alicia.
"Cygnus Olor." Animal Diversity Web. University of
Michigan, n.d. Web. 14 May 2014.
Reese, Jan G.
"Productivity and Management of Feral Mute Swans in Chesapeake
Bay." The Journal of Wildlife Management 39.2 (1975):
280-87. Print.
Swift, Bryan L., Kevin
J. Clarke, Robin A. Holevinski, and Elizabeth M. Cooper. "STATUS AND ECOLOGY
OF MUTE SWANS IN NEW YORK STATE." New York State Department of
Environmental Conservation, Dec. 2013. Web. 14 May 2014.