Ecuador boasts of 369 species which puts it by far in
first place by species per square area and in 9th place worldwide in species found
by country. Most mammals live in tropical regions
and
decrease in number the higher one moves up the
Andes mountain range. The Galapagos
islands have only twelve native mammal species but nine of
them are endemic, only place in the world, where they can be
found. As a whole, Ecuador boasts of 30 endemic species, most of
them members of the rodent family.
There
exists some 100 known rodents but the number is
probably higher as not enough research is yet done.
The largest living rodent in the world is the Capybaraand lives in the tropical
rainforest of the nation's Amazon.
The same problem goes for bats, where 132
species are accounted for in the country but more are believed
to exist. 23 species belong to the marsupial sub-class
with the
opossums, the most visible representatives.The
largest terrestrial mammal found is the tapir,
which can weigh up to 300 kg and belongs to the odd-toed
ungulates (hoofed animals).Three
species of those inoffensive animals are counted however
with one specie on the brink of extinction. Eleven even-toed animals are also part of the landscape with thellamasthe most interesting one. The carnivores have 31
species present in the country with two beautiful members of
the cat family,
the
mighty jaguar and the smaller ocelot
found in the tropical rainforests. But the most
versatile of all cats is the puma,
which adapted to all habitats and can be found in all regions
of the country although it is now under siege by human
encroachment.In the higher Andean
region of the paramo you find two more carnivores, the
Andean fox,
a member of the dog family and the
spectacled bear,
the only bear specie
in the whole national territory. Other
carnivores, which adapted to life in water are the otters with
the giant otter being the most fascinating one and the marine
sea lions.
Many, of course, are interested in the
New World
Monkeys and 19 members of those primates
inhabit the lower tropical regions. Introduced here are the
Woolly,
Spider, Squirrel and Howler Monkeys.
Other mammals found are a lone member of the rabbit
family,a manatee or sea cow in the Amazon rivers, 3 species of
insectivores and 12 members of the armadillo,
anteater and sloth family of Edentata (or Xenarthra).
In the oceans surrounding Galapagos and Ecuador are
furthermore found some 33 species of
whales
and
dolphins,
with two dolphins inhabiting the freshwater rivers and lakes
of the Amazon.
Mutual Grooming is an important
social aspect among mammals, especially primates. Not only helps it
to keep parts of one΄s body clean and free of lice and
other harmful creatures which cannot be easily reached
by oneself but it also establishes relations
and hiearchy among group members.
Capuchin Monkeys and humans alike seem
to enjoy this social activity.
The
natural history of South American mammals is an
interesting case study of evolutionary biology. Mammals need a
large island, a continent, to properly disperse and be able to speciate.
Historically there were only three
cases of that happening, namely in Eurasia, Australia and South America
(which for a long time was an isolated island continent). After the decline of the dinosaurs
beginning at some 65 million years ago primitive
mammals started to radiate and to take over the abandoned
ecological niches (by the once dominating dinosaurs) during the
next 40 million years. At that time also the huge continent of
Gondwana (conglomeration of Antarctica, South America,
Africa, Madagascar, India and Australia) started to break up.
On the new continent known today as South America marsupial
and placental animals got stranded. The interesting part is
that the herbivores were mostly placental and
were hunted
by marsupialcarnivores.
From that early stock all marsupial carnivores are
extinct now and from the earliest placental animals only the
edentates (also called xenarthrans), the armadillos, anteaters and
sloth are still around. After the breakup South America stayed
closest to the African continent, moving away
from it slowly by way of continental drift (presently it moves
at a rate of a few centimeters by decade). A new wave of
mammals invaded the continent from there by island hopping
some 30 million years
ago and that is how the first primates arrived
here. They gave later rise to the New World Monkeys as known
today. Other island hoppers included rodent ancestors
of capybaras, guinea pigs and porcupines. From that time on
South America was separated from all other continents by
broad and unbridgeable seaways. Unique grazing animals like litopterns
(horse like but from a completely different lineage as the
Old World horses) and giant ground sloth (weighing up to 4 tones and
reaching heights of 6m) and many others graced the landscape.
They were preyed upon by marsupial saber-toothed tigers and a
giant carnivorous bird (standing up to 3 meters) among others.
With time South America drifted closer to the North
American continent, which itself broke away from the Eurasian
continent and then some 3
million years ago the Panama isthmus appeared creating a
natural land bridge. This opened up a new route of migrations
and animals from the south migrated to the north and vice
versa enriching both continent's
fauna, the
so-called
Great American Interchange. Over time however most
SA animals had to give in to the northern animals occupying the
same ecological niche and became extinct in the process. It
seems that placental mammals of North America were
exposed to competition for a much longer time and more
intensely than the South
American ones and therefore out competed them. Presently
half of the mammal species (cats, llamas, bear, peccaries,
otters, foxes,...) on the continent are of that recent
foreigninvasion.
For a fascinating account read the book by George Gaylord
Simpson with the appropiate title of Splendid Isolation - The
Curious
History of South American Mammals.
South America is the
only other place apart from Australia where marsupials
still exist. Although not that abundant anymore and reduced to
smaller sized creatures they still hold their place among
placental mammals. One species, the Virginia Opossum even occurs
in the USA having migrated there from South America.
Opossums are found mostly in the lower tropical regions of the
country. But one specie, the White-Faced Opossum makes its
living in the Andes to elevations of up to 3000m. Thus it was a
huge surprise to find one on top of Pichincha volcano at 4900m,
just a few meters below the peak. It seems that it got lost but could
it
be that it makes a living up there in higher altitudes?
Another important
region
of evolutionary biology (but completely unconnected with the
above story) are the
Galapagos archipelago. Those islands located
some 1000km west of the Ecuadorian mainland, arose from the
sea some 3 million years ago and never were connected with
any continent. Terrestrial mammals are
scarce there as they have major difficulties reaching those
remote Pacific islands. They cannot survive long trips
on vegetation rafts as the cold-blooded reptiles are able to do. Only a few mice and
bats arrived thus but always played a secondary role to birds
and reptiles. The most influential mammals therefore are
aquatic species like whales and sea lions, which play
an important role in the marine environment. Nowadays
however, mammal species introduced by humans play an important
role on land, alas seen from the ecological view a very negative
one as they play havoc in the lives of native animals.
Feral goats, pigs, dogs and other formerly domestic
animals compete for scarce food resources or predate on the
animals themselves or their eggs. Also the
opening up of pastures for cattles and horses destroyed many
ecological habitats for native animals.
Natural
History
Mammals are descendants of mammal-like reptiles which lived in the earlier period of
of Mesozoic era some 210 million years ago. For a long
time they co-existed with other reptiles but stayed for a long
time in the shadow of reptiles, especially dinosaurs which
dominated
many ecological niches. Mammals at that time were smaller creatures,
probably burrowing in the soil or living in the trees and active
mostly at night. But the
mass extinction of 65 million years ago changed all that with the
dinosaurs and other reptiles becoming extinct. The mammals had
then the opportunity to fill the abandoned
niches left by the former champions. They did that very successfully and
split into multiple species by adaptive radiation. Some became
grazers, others carnivores preying on them, one group turned to
the skies to evolve into bats, some even returned
to the seas. One specie transformed itself into the huge
whales, the largest animal ever to have lived.
Mammalian
Classification
Monotremata
Monotremes are egg-laying mammals with only a few
species left (e.g. spiny anteater, platypus) in
Australia and surrounding islands. They represent the
most primitive lineage going back to the Mesozoic.
Marsupialia
Marsupials is another sub-class with 282 species,
most of them in Australia and a few (e.g. opossums) on the American continent.
Eutheria
are
the placental animals which comprise the majority
of the over 4600 species of mammals
worldwide. They are found on all continents but
with only a few species living in Australia.
Mammals inhabit all parts of the earth and range in sizes from a few centimeters and weighing a
few grams (mice) to 30 meters and up to a hundred tons (whales) but all are warm-blooded vertebrates (having a spinal column)
with a relatively well-developed brain. Some or all parts of their body are
covered by hair and all have (or had once) four limbs, which
evolved into walking, handling, flying and swimming appendages. Another
distinguishing trait is the sexual breeding through copulation
by male and females and the parental care they give to their young,
nourishing them with milk, produced in the female mammary glands, which gave that class its
name.
Recommended
Books (used in
research)
SPLENDID ISOLATION by
George Gaylord Simpson
NEOTROPICAL RAINFOREST MAMMALS
by Louise H. Emmons
