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Aquatic Predators-Crocs-2
J. Moore (j#d#.moore@canrem.com)
Mon, 26 Jun 95 10:13:00 -0500
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This quote is from a recent post by Elaine Morgan:
EM> On the matter of crocodiles .. Instead of all these
EM> hypothetical crocodiles, read what really happens when the
EM> extant tribesmen in the Danakil area need to cross a
EM> crocodile-infested river today. They wade across it, with
EM> their cattle. The apparent reason is that the river is
EM> swarming with tilapia fish. Your average croc will not go
EM> through the strenuous business of grabbing the leg of a large
EM> mammal and threshing and twisting around to tear it off, if
EM> he is full of tilapia and simply not hungry. (Source:
EM> Africa's Rift Valley, in the World's Wild Places series by
EM> Time/Life books)
[my note: reading the above-mentioned book one is struck by Elaine
Morgan's research style; it is in this case at least, I must say,
somewhat lax. The passage doesn't mention cattle, but rather "camels
and goats", and the fish are catfish, not tilapia.
But the question is not really whether or not Morgan gets her facts
straight, or even whether author Collin Willock can actually spot
"apparent fear or even watchfulness" from his perch in a helicopter
flying overhead, but rather whether Nile Crocodiles are, as Morgan
implies, merely peaceful fish-eaters who wouldn't harm a small aqautic
biped. Let's see what the experts say.]
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Evolution and Biology: Living Crocodilians
Chapter by Charles A. Ross (Museum Specialist, Department of Vertebrate
Zoology, National Museum of Natural History, Smithsonian Institution,
Washington, D.C., USA) and Dr. William Ernest Magnusson (Research
Scientist, Instituto Nacional de Pesquisas de Amazonia, Brazil)
pg. 67:
Nile Crocodile (*Crocodylus niloticus*)
Habitat: Known to occupy a wide variety of freshwater habitats, this
species also frequents coastal areas in West Africa, and in southern
Africa one was spotted nearly 11 kilometers (7 miles) off the Zululand
coast. From time to time crocodiles are washed out from East African
river mouths to the sea; some of these have been able to cross to the
island of Zanzibar [note: Zanzibar is 22 miles off the coast of
Tanganyika, which together form the republic Tanzania] and crocodiles are
occasionally found on beaches or river mouths in Kenya.
Distribution: The widespread crocodilian of the African continent, it is
found throughout tropical and southern Africa, and Madagascar. its
historical distribution included the Nile River delta and the
Mediterranean coast from Tunisia to Syria. Isolated populations of the
Nile Crocodiule are known to have existed in lakes and waterholes in the
interior of Mauritania, southeastern Algeria, and northeastern Chad in
the Sahara Desert.
Diet: Very large animals eat antelope, zebra, warthogs, large domestic
animals, and humans.
pg. 68:
Indopacific Crocodile (*Crocodylus porosus*)
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[I'm not suggesting that the aquatic hominids were romping about in Asia,
and note only that the Indopacific Crocodile may have had a wider range
at one time. The main reason I've listed info on them is that it gives
a clear picture of the abilities of crocodiles to live even in oceanic
waters, travel great distances, and colonize new areas. It has also
been found that in areas where Indopacific Crocodiles *do not* live,
such as when and where they were hunted out in the 1950s and 1960s,
other corodiles took over those habitats, including salt-water habitats.]
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Habitat: Commonly encountered in marine habitats, the common names
Estuarine or Saltwater Crocodile are, however, misleading since this
species is often found in freshwater habitats such as large rivers and
lakes.
Distribution: The most widely distributed of all living crocodilians,
the Indopacific Crocodile is found throughout the tropical regions of
Asia and the Pacific, wherever there is suitable habitat. Its
distribution is still not fully known but recent research suggests that
it is found from the islands of the Indian Ocean, coastal India and Sri
Lanka, through mainland Southeast Asia, the Indonesian and philippine
islands, northern Australia, New Guinea, as far as the Belau Islands and
perhaps Fiji in the Pacific Ocean. The ability of this species to
survive in the open ocean has enabled it to reach, and sometimes
colonize, many small islands such as the Cocos Islands (nearly 1,000
kilometers from land) and the New Hebrides. Stories of these crocodiles
out in the open ocean abound and some individuals have been seen with
pelagic barnacles attached to their scales.
Diet: Large animals eat whatever they want, including a variety of
mammals and some birds. Fish also form part of the diet.
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[More on food and hunting styles of these crocodiles.]
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Behavior and Environment: Food and Feeding Habits
Chapter by A.C. (Tony) Pooley (Consultant on Crocodile Farming,
Conservation, and Education, Scottburgh, South Africa)
pg. 83:
The Nile Crocodile has an extremely wide range of mammals in its diet
ranging from cane rats to Cape buffaloes, which can be as heavy as
itself. Mugger, Indopacific, and Nile crocodiles also include humans in
their food range.
pg. 83
Crocodilians are usually regarded as idle hunters that lie in wait in
the offshore shallows for the approach of unsuspecting prey. They rely
on camouflage and an ability to lie submerged with only their nostrils,
eyes, and ears above the surface to scent, see, and hear approaching
prey. From this concealed position they can launch themselves out of
the water with astonishing speed, and may make a rush of several meters
up a beach to snap at prey approaching the shoreline. Even large
crocodilians are capable of vaulting almost vertically out of the water
to a height of more then 1.5 meters (5 feet) to snap at birds or animals
on river bancks above them.
pg. 86:
Sometimes the crocodile erupts from the water into the midst of a herd
of drinking antelope then uses its massive bony head to deliver
sledge-hammer side-to-side blows to stun prey, break limbs, or knock an
antelope into the water.
pg. 86:
Many of the larger crocodilians are known to take advantage of the
habitual behavior of their prey, taking up position in the water on
regularly used game trails, or at well-used river crossings or watering
sites for humans and livestock, particularly if previous attacks at
these sites have been sucessful.
pg. 86 (picture of crocodile attacking a wildebeest, captioned):
On their long migrations vast herds of wildebeest have to cross many
streams and rivers. With so many animals to choose from this crocodile
does not even bother to submerge before attacking.
pg. 90:
In other Zululand rivers similar behavior may be seen in summer when
rivers flood and water spills over into channels leading to natural
pans. The crocodiles form a barrier where a channel enters the pan,
facing the inrushing water and snapping up river fishes such as bream
(genus *Tilapia*) and catfish.
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[Okay, it's clear that crocodiles, and Nile Crocodiles in particular,
are not the peaceful, fish-eating creatures Morgan suggested. But
surely they aren't really capable of killing and eating humans! Keeping
in mind that the humans of today, even those with the most primitve of
weapons, are better-armed than our earliest hominids.]
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Crocodilians and Humans: Attacks on Humans
Chapter by A.C. (Tony) Pooley (Consultant on Crocodile Farming,
Conservation, and Education, Scottburgh, South Africa), Tommy C. Hines
(Consultant on Alligator and Crocodile Management, Florida, USA), and
John Shield (Veternarian, Cairns, Australia)
pp. 173-174:
Adult Nile Crocodiles weighing as much as 1,000 kilograms (2,200
pounds) and up to 6.5 meters (21 feet) in length have been recorded.
The Nile Crocodile has evolved on a continent where it has had to
contend and compete with a far greater variety of competitors, as well
as potential prey species, than any other crocodilian in the world.
Competitiors in the aquatic habitat include predatory fish and sharks,
monitor lizards, three other crocodile species, and hippopatamuses. On
land, it needs to defend territory, nest sites, and offspring against a
range of predators and competitors ranging from small mongooses to
elephants, and, of course, humans. Consequently, the Nile Crocodile is
one of the most aggressive of all crocodiles. In order to survive in
habitats populated by such a diverse fauna, it has become a versatile
and opportunistic hunter, and master predator of the aquatic
environment.
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[So it's good at its job, but what about defense? What about
spotting it coming and getting out of the water?]]
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Continued next message...
Jim Moore (j#d#.moore@canrem.com)
* Q-Blue 2.0 *
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