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Not Your Average Penguin
How Evolution Has Shaped the Galapagos Penguin
Andrew Easton
Sophomore College
Stanford University
©2008
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There is something so breathtaking about the thought that, as an environment
changes, living organisms actually adapt, generation by generation, to accommodate the
new features that may arise. And yet, this is a reality. The concept of evolution accounts
for these slight changes in species over time as they adjust to their surroundings.
However, many people are misled by this notion. For example, in many discussions with
educated individuals about the dangers of global warming, I have heard the response,
“but the species will just adapt to the new conditions.” Many people are under the
impression that evolution can adapt any species to any environment. Sadly, this is simply
not the case. The Galapagos Penguins are a perfect example of a species that is
endangered by environmental change in such a way that it will not be able to adjust if the
trend continues in the future. These penguins have significantly adapted to the warmer
climate of the Galapagos in such a way that they are unable to conform to new
environmental pressures while still remaining successfully reproductive in the warmer
temperatures.
Known to the Spanish
sailors as Las Islas Encantadas (or
the
Enchanted
Galapagos
Islands),
the
Archipelago
is
comprised of several volcanic
landmasses.
These
islands,
located directly on the equator,
The view from Bartoleme
have an incredibly unique ecosystem. There are several important reasons for this. First,
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the Galapagos is located at a confluence of currents. One of the currents, the Panama,
brings warm water down from Mexico while a second, the Humboldt, carries cold water
as it streams up the coast of South America.
Meanwhile, the South Equatorial Current,
caused by the rotation of the Earth, forces all
the surface water to cycle across the Pacific
Ocean from east to west. These waters then
cycle back as an undercurrent, known as the
Cromwell Current, which surfaces as it hits the
western shores of the islands. Because the
*1 The currents of the Galapagos
Humboldt Current brings Antarctic waters to the eastern islands and the Cromwell
Current delivers water from the depths of the ocean, the water surrounding the Galapagos
is, surprising, quite cold. The Cromwell Current, however, also brings with it a bountiful
and nutrient rich marine life, which acts as food for many of the birds in the area
(Galapagos Ocean Currents).
The unique marine environment is not the only interesting factor controlling life
in the Galapagos however. The air above the Pacific Ocean is cycled as well, caused by
the same forces as the Equatorial Current. The air is lower traveling from east to west,
and then rises before circling back over the vast expanse of water. As a result, the air
becomes very moist in the west as it absorbs water from the surface of the ocean. As it
rises, it becomes less dense and dumps rain onto the South Pacific. It then cycles back
towards the Galapagos and sinks, absorbing all the water that exists in the air and moving
it away, back towards the east (TAO Project). Because of this, and also partially because
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much of the volcanic soil of the Galapagos is infertile, the land is often dry and barren.
As a result, very few land species have successfully adapted to the harsh conditions of the
islands (Kricher 2002: ). The penguin is one of the lucky few.
But the process wasn’t easy, and the penguin varies significantly from its
Antarctic counterparts. The Galapagos Penguin (Spheniscus mendiculus) is the only
penguin that can be found in the northern hemisphere, for example. Of the seventeen
different species of penguin, sixteen are confined entirely south of the equator. Fifteen of
these species breed only south of the Tropic of Capricorn, located more than 23° south. It
is quite clear that penguins typically live in very cold climates. As a result, they are
normally fairly large, and coated with both fat and feathers to trap in all the heat it can
possibly retain. Also, species of penguins that breed further south are larger than their
more northerly counterparts. The average height of penguins breeding in Antarctica is
about 100cm. In the sub-arctic islands and the tip of Africa, they grow to an average of
80cm. Those on the coast of South America general measure around 70cm, and those
found on Australia or New Zealand are, on average, 65cm. Essentially, the warmer the
climate, the smaller the penguin. This trend applies not only to height, but to girth and
insulation as well. Two more trends of penguins worth noting are that sixteen of the
seventeen species moult once a year, directly preceding their breeding season. Also, on
average, a penguin is known to swim as far as thirty-five kilometers from its breeding
ground when it hunts for food (Penguins).
While all seventeen species of penguin evolved from a common ancestor, it is
quite clear that the Galapagos Penguin most recently diverged from the Humboldt
Penguin. This species roams the western shores of South America, mostly in northern
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Chile. The Humboldt Penguin is most similar to the
Galapagos
both
physically
and
genetically.
The
divergence probably occurred as a result of the Humboldt
Current. Recall that this current runs up the coast of
South America and funnels straight to the islands. All that
the ancestor penguin had to do was swim off shore and
catch a ride directly to the Galapagos Islands. At this
point, the separate penguin populations continued
*2 Comparing the
Humboldt Penguin
speciating slightly differently until, three million years
later, they are the separate species as we now see them (Vargas 1997: 30).
In many ways, the Galapagos Penguin continued
following the same evolutionary trend as all penguins that
venture further north. On average, the Humboldt Penguin is
seventy centimeters tall. The Galapagos Penguin is only
fifty. The Humboldt Penguin also has more insulating fat
than the Galapagos variety (Penguins). Because of the
warmer climate of the islands, the smaller size was selected
for, and the Galapagos Penguin adjusted by adopting a
*3 Comparing the
Galapagos Penguin
smaller body size in order to help regulate heat and stay cool (Boersma 2008). However,
because this trend is not found only in the Galapagos and, instead, is true of all penguins
that venture north, it is an exaptation rather than an adaptation.
But there were Galapagos specific adaptations as well. These came mostly in the
form of changes in breeding and feeding behavior. Because the penguin’s food source
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depends almost entirely on the Cromwell Current, and because this current is not entirely
regular (there are sometimes fluctuations in the South Equatorial Current), they became
opportunistic breeders. This means that instead of having one breeding season like every
other species, they breed whenever there is
sufficient food to feed their young. As a result,
the penguins moult twice a year, instead of once
directly preceding their breeding behavior. Also,
in order to be able to return to their nests quickly,
the penguins began hunting closer and closer to
shore. In fact, they never search for food more
*4 Feeding range of the Galapagos Penguin
than two kilometers from their nests (Boersma
1978: 1481-83). However, part of this limited feeding range is hypothesized to also be
influenced by a ridge approximately two kilometers of shore, after which hammerheads
and other predators become much more prevalent. The penguin’s abnormally small size
makes it easy prey for these animals, and thus it avoids their territory (Boersma 2008).
For thousands of years these adaptations continued to benefit the penguins of the
Galapagos Islands.
However, there is one environmental situation in which the Galapagos Penguins
do not fair well. El Nino events are very harmful to the population, and almost every time
one occurs, hundreds of penguins die (Boersma 1998: 245). El Nino’s occur when the
trade winds causing the South Equatorial Current to move from east to west change
directions. It is still unknown exactly why this phenomenon occurs, however the effects
are tremendous. All of the warm surface water on the equator is directed towards the
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Galapagos
instead,
drastically
increasing
the
temperature surrounding the islands. At the same
time, the Cromwell Current is completely cut off, and
a significant amount of the marine life simply
disappears. In addition, the dense moist air that once
hung above the south pacific now accumulates
directly above the archipelago and pours rain onto the
islands, transforming the land conditions from dry to
almost tropical (TAO Project). While many land
species thrive in these conditions, the penguins, which
rely on the delicate balance of currents for food, are
*5 Diagram of how El Nino works
decimated (Vargas 2005: 3-5). It is the adapted traits tailored to the usual environment
that harm the penguins during these times. Because of both their new opportunistic
breeding habits and their smaller size, which makes them more vulnerable to predators,
the penguins are not able to swim the distances required to find food.
Unfortunately for the Galapagos Penguin, El Ninos are becoming more and more
frequent in recent times, giving the population less time to recover between events. Many
people are speculating that humans are causing this change, however regardless of the
accuracy of these claims, these alterations pose a major problem for the penguins. In the
past, there has been enough time between El Ninos for the penguin population to
convalesce, and over extended periods of time the population has remained fairly
constant. However, this is slowly changing and is no longer the case. With the events
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occurring more frequently, the penguin population is beginning a steady decline (Vargas
2005: 371-73).
In the El Nino of 1982-1983, 77% of the penguin population died. During another
El Nino, from 1997-1998, 66% of the penguin population died. What is even more
unnerving, however, is that from 1980 until 2006, the population decreased by more than
50%. This includes eight years of recovery time since the last major El Nino (Boersma
1998: 248). If this trend continues, penguins will not reside on the Galapagos Islands for
long.
But El Ninos are not the only cause of this decline. Introduced predators are also
playing their part. Because life on the islands is so arduous, and because it was incredibly
difficult for land animals to reach the archipelago, there have been no real land predators
of the adult penguin (rice rats and snakes, among others, attack the eggs) (Bingham). This
is one reason that the major decrease in body size was not detrimental. However, with
feral cats and dogs being introduced to the islands, the penguin’s small size makes them
perfect prey (Vargas 2005: 6).
With an increasing number of predators, and an increasing need to swim further
from shore, one may postulate that the penguin would begin to adapt for a larger size and
swimming range. However, these are
the exact traits that were selected
against when the penguin first came
to the islands and this poses a major
problem. A large penguin would
overheat in the warm climate, but a
Swimming of the coast of Floreana
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small penguin would be easy prey for the new predators. Essentially, if these new
phenomena subsist, the penguin will not be able to successfully adapt to the new
environment. Most specialists believe the Galapagos Penguin will be extinct in less than
two hundred years and my research fully supports these claims.
The only way to stop the current decimation of the penguin population is to
address these two major issues. El Nino is tricky because it is hard to say if, or how much
of, the increase in frequency is caused by
humans. As such, we should continue
studying these events in order to ascertain the
cause of the increase in frequency. However,
eliminating
A penguin resting on Isabela Island
the
introduced
species
will
certainly immediately help the penguin, as
well as many other species on the islands, so this should be the major conservation focus
at this time.
If we do not address the problem, or do not succeed in fixing it, the Galapagos
Penguin will become extinct. In the increasingly prevalent ecosystem, the penguin will
survive neither as small nor large, and neither as a long-range nor short-range swimmer.
It simply cannot adapt to these new conditions. This relationship demonstrates how
evolution is not a theory in which any species can successfully change to fit and thrive in
any environment. Evolution is the process in which organisms adapt to their changing
surroundings, however the process is not perfect. Using the theory of evolution as an
excuse for humans to change the world is simply unacceptable considering that the
majority of current species, like the penguins, would not survive.
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WORKS CITED
*1 underlying image from commons.wikimedia.org
*2 underlying image from www.theanimalfiles.com
*3 underlying image from www.spallek.net
*4 underlying image from wallpapers.jerko.net
*5 from TAO Project
Bingham, Mike. “Galapagos Penguin.” International Penguin Conservation Work Group.
5 Sept. 2008. < http://www.penguins.cl/galapagos-penguins.htm>.
Boersma, Dee. 1977. “An Ecological and Behavioral Study of the Galapagos Penguin.”
Living Bird 15: 43–93.
Boersma, Dee. 1978. “Breeding Patterns of Galapagos Penguins as an Indicator of
Oceanographic Conditions.” Science200: 1481–1483.
Boersma, Dee. 1979. “Penguins in the Galapagos.” Noticias de Galapagos 29: 15 – 16.
Boersma, P. D. 1998. “Population Trends of the Galapagos Penguin: Impacts of El Niño
and La Niña.” The Condor 100: 245-253.
Boersma, P. Dee. Personal Emails. 5 September, 2008. 7 September, 2008.
Fitter, Daniel and Julian and David Hosking. Wildlife of the Galapagos. Princeton, NJ:
HarperCollinsPublishers Ltd., 2007.
“Galapagos Ocean Currents.” Galapagos Online. 4 Sept. 2008.
<http://www.galapagosonline.com/Galapagos_Natural_History/Oceanography/Curren
ts.html>
Kricher, John. Galapagos. Washington D.C.: Smithsonian Institution, 2002.
Muller-Schwarze, Dietland. The Behavior of Penguins: Adapted to Ice and Tropics.
Albany, NY: State University of New York Press, 1984.
"Penguins." Wildlife of Antarctica. Antarctic Connection. 4 Sept. 2008
<http://www.antarcticconnection.com/antarctic/wildlife/penguins.shtml>.
TAO Project. "What is an El Nino?" NOAA. US Department of Commerce. 4 Sept. 2008
<http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html>.
Vargas, Hernán, et al. 1997. “First Report of Penguins Nesting on Isla Floreana.”
Noticias de Galapagos. 58: 30 – 32.
Vargas, Hernán F., et al. 2005. “Biological Effects of El Niño on the Galapagos
Penguin.” Biological Conservation: 1-6.
Vargas, Hernán, et al. 2005. “Population size and trends of the Galapagos Penguin
Spheniscus mendiculus.” Ibis. 147 (2): 367 – 374.