Let us talk about giraffes and their relatives, just because.
The modern giraffe…consists of no one has a definite
idea of how many species of the modern giraffes there are: an 8, a 4, and a
3-species family trees are proposed, and so far, not a single one out of them
has won, all three theories are equally valid. That said, all of the giraffes
are the world’s tallest mammal; they all are browsers, and eat leaves and other
parts of trees and shrubs rather than grasses and other herbaceous plants. This
is important, as grasses tend to regrow after they had been cropped by such
mammals as the zebra, whereas tree leaves… also regrow, eventually, but at a
much slower pace than how the grasses do. Therefore, many African savanna trees
have evolved… some, as the acacias, have spines and symbiotic relationship with
ants, (rather than termites), while the baobabs are flat-out huge and can
handle the giraffes through their sheer size and bulk… eventually. Still, we
digress.
Regardless of how many species of the modern giraffe
there is, the modern okapis are represented by a single species, the, well,
modern okapi. It is also called ‘the forest giraffe’, ‘the zebra giraffe’ and
the like, but scientifically, it is named Okapia johnstoni. It is smaller, or
rather – shorter than the ‘true’ giraffe of the African savanna, which means
that it is less specialized than its’ cousin (cousins?) is.
Why? Because – proportionally – the okapi has a more
varied diet than the giraffe from the start. It, too, eats foliage rather than
grasses, as does the giraffe… but it does so because there is far fewer ‘true’
grasses in the jungle where it lives. The grasses are plants of open spaces,
because in enclosed spaces bigger plants – shrubs and trees – block out the
sun, and the herbaceous plants that live in forests – whether temperate or
tropical – are more shadow loving than their grassland counterparts are. …Yes,
this is generalization, but you get the point. Back to the okapi.
Again, it eats foliage and other parts of trees and
shrubs, (the non-woody ones), and has many similarities to the giraffe, but
because it lives in a proportionally more abundant and varied ecosystem, it is
smaller and less derived than the giraffe is. In addition, there are fewer big
herbivores in the jungle, as opposed to the savanna, and they tend to be
smaller in size – the okapi, the African forest elephant, the forest antelopes,
the pygmy hippo, even the non-white rhinos of the world – they all are smaller
than their savanna-dwelling relatives are. In part because they’re living in
tighter conditions, in part – because there’s less competition between the
species, and fewer big predators as well – out of Africa’s ‘big five’, only the
leopard enters the jungle, and it doesn’t appear to be attacking okapis
regularly, for example, or giraffes for that matter. As such, the okapis do not
need to get as big as the giraffe, as the giraffe’s size – or height – protects
it from the leopards, lions, etc. (Moreover, the baobab’s size protects it from
the giraffes, elephants, etc.). What next?
From the close relatives, to the more distant ones –
the American pronghorns, the last members of the giraffes’ sister group.
However, it is known as ‘the American antelope’ and ‘the pronghorn antelope’
among other monikers, this mammal – Antilocapra americana – is much less
derived than the ‘true’ antelopes of the Old World is, and proportionally, it
is much more closely related to the giraffe and the okapi. That said,
physically, ‘on the outside’, the pronghorn is reminiscent… of the gazelles of
Africa and Asia.
Eh, ok, gazelles are antelopes, in a matter of
speaking. However, they are also antelopes that evolved for speed; they are
light-bodied, long-legged and gracile, as opposed to something like the eland,
which is built more like a cow, quite robust, or even the gnu, which is more of
an endurance marathon runner instead. The American pronghorn, however, is also
a marathon runner, having evolved in a time period when North America had its’
own cheetah species, (more closely related to the puma than to the modern Old
World cheetah), and cheetahs are the ultimate sprinters – but we digress. These
days, North America has no cheetahs, but what it does have is an Old World
civilization that restricts’ the pronghorns’ (and the bison’s’, the peccaries’,
etc.) prairie habitat, causing their populations to plummet regardless, much
more efficiently than any cheetah would be able to… However, for us, what is
important here and now that while the ‘true’ giraffe is a savanna foliage specialist, and the okapi is a jungle
foliage generalist, the pronghorn is
a prairie grass generalist instead.
Is there anything left?
Actually, yes – the chevrotains or the mouse deer.
Contrary to their names, the ‘rest’ of the deer are not close relatives of these
mammals; the ‘true’ deer, and the musk deer, are much more evolved than the
chevrotains are.
Let us try again. Among the modern ruminants, two
groups stand above the rest. One group are the bovids – antelopes and gazelles,
wild cattle, sheep and goats. Moreover, the second group are the deer. There
are the ‘true’ deer, which consist of two subfamilies – the American deer,
(with some exceptions, such as the moose, the caribou and the roe deer), and
the Old World deer, (with some exceptions, such as the wapiti). The second
family are the musk deer, (6 or 7 species), which are the sister group to the
‘true’ deer. Moreover, the mouse deer/chevrotains?
…They are much less derived than the ‘other’ deer –
in fact, the rest of the ruminant artiodactyl mammals – are, and
proportionally, they are much more closely related to the giraffe, the okapi
and the pronghorn.
What do chevrotains look like? Tiny, vaguely
deer-like animals with hooves, but without antlers. Some have also
proportionally big canine teeth, superficially like the much bigger musk deer.
(Actually, the musk deer are quite smaller than the ‘real’ deer, but they are
still quite bigger than the mouse deer). They live in jungles – one in Africa,
the rest – in Asia. That is because in Africa, their niche is taken over by the
antelopes, i.e. the duikers and the Neotragus
species, but that is another story.
Anything else? Right, the water chevrotain – the outsider
that lives in Africa, rather than in Asia – is omnivorous, the others are less
so, and all are found close to water. Put otherwise, not unlike the giraffe,
the mouse deer are specialized – they have a very specific econiche in which
they live, and this enables them to survive, avoiding competition with more
derived herbivores. Only not, for in Africa that same econiche is taken over by
those more derived herbivores – small jungle antelopes, such as duiker, and so
only the water chevrotain Hyemoschus aquaticus is able to
survive there, by being the most aquatic and most omnivorous out of them all.
As Po the giant panda told the snow leopard villain of the first ‘Kung Fu Panda’
movie, “there’s no ultimate secret”, there is no ultimate solution to anything.
Let us conclude. On our narrative about the giraffe,
we met four very different types of even-toed mammals. As we look at them, we
see the giraffe, browsing from the treetops of the African savanna, the pronghorn,
grazing on the grasses of the American prairie, the okapi, who is eating the
leaves in the African jungle, and the mouse deer, which are scurrying through
the undergrowth of Asian, but also African jungles, eating various general
plant matter. They all look different from each other, but all are also more
closely related to each other – proportionally
– than to any other plant-eating mammal. This, then, is the wonder of evolution.
