able to browse at higher levels and
perhaps take some of the rougher
graze on offer. To some extent they
filled part of the space that had
been left vacant since the
disappearance of the megafauna.
But the story is not all good. Such
developments imply changes in
ecosystems which – because deer
are not the same as the departed
megafauna – may bring other native
species under pressure. The rusa is
an interesting case in this respect.
To understand why, we need to
know something about the
evolution of the rusa.
At the same time that the
megafauna were disappearing, rusa
were thriving on the Sunda Shelf- the broad, low-lying land mass
that today takes in the Malay
Peninsula and most of the islands of
Southeast Asia. Rusa-type deer first
appeared in the area where China is
today, as a non-specialised grazing
and browsing species living in
sub-tropical forest. As the sub-
tropical forest zone shifted south
and the deer moved with it, at some
point, sambar split off from this
evolutionary line to specialise as a
browser living a solitary life in the
thickets. But the rusa continued as
non-specialists, perhaps evolving
more of a grazing lifestyle as they
settled into the savannahs of the
Sunda Shelf.
Throughout this period of global
history, the Sunda Shelf and Sahul
(Australian landmass) remained
separate, even at times of the lowest
sea level, and animals on the two
land masses developed from
distinctly different lineages – the
placental mammals on the land
mass which included the Sunda
Shelf and the marsupials on Sahul.
The geographic line of separation
is known today as the Wallace Line,
named for the great naturalist Sir
Alfred Russel Wallace, who was the
first to note its significance for the
separation of placental mammals
from marsupials, and for the
development of different species
within those groups. For all practical
purposes, the Wallace Line (which
runs through the Lombok Strait) is a
biologically impassable barrier
separating Asia from Australia and
its associated islands.
When the seas rose at the
beginning of the Holocene, rusa
retreated to the islands of Java and
Bali. From Bali they might have
looked out across the narrow strait
to the island of Lombok, with its
tropical savannahs perhaps more
reminiscent of the now-flooded
Sunda Shelf. But Lombok and the
other islands to the east might well
have been a world away.62 | SPORTING SHOOTER _ MAY 2018
No species over
100 kilograms
survived the
mass extinction.”
DEER
HUNTING3
4
3
Rusa stags
collect grass
and weeds in their
racks as part of
their dominance
display. In this
instance the
challenger failed
to impress.
4
Environmental
change: The
dense clumping
grow th of native
oat grass
(Themeda
avanacea) is too
coarse for
kangaroos and
unpalatable to
cat tle, but the
stands are quickly
reduced once rusa
move in. Thinning
these clumps may
deprive smaller
marsupials of
much needed
shelter.
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