of the croc to Jaffna
By Charles Santiapillai and S. Wijeyamohan
A recent survey carried out in the Jaffna peninsula, in and around
the Thondamanaru lagoon confirmed the presence of crocodiles. It
appears that crocodiles are among those species that benefited from
the 18-year armed conflict in the area. The conflict seems to have
favoured the return of the crocodiles following the displacement
of many people from the area. It is one of the few instances where
war may have helped improve biodiversity.
did occur in the distant past in the Jaffna peninsula. In 1672,
the Dutchman Reverend Phillipus Baldaeus observed them in the fens,
ponds, and lakes of the Jaffna peninsula. In the 19th century, Sir
Emerson Tennent referred to the still waters and tanks of the northern
provinces "teeming with crocodiles".
with increased urbanization, crocodiles began to decline both in
range and number in the peninsula and for some time, they were generally
believed to have become locally extinct there for several decades.
An island-wide survey of the crocodiles carried out by Rom and Zai
Whitaker in 1977 could not find any in the Thondamanaru lagoon,
although they mentioned that Chundikulam Sanctuary, noted for its
birds, might harbour occasional crocodiles moving in from the tanks
and water holes.
Two species of crocodile are found in Sri Lanka: the 'freshy'
or marsh or freshwater crocodile (Crocody-lus palustris) and the
'salty' or estuarine crocodile (C. porosus). Both are listed on
Appendix I of CITES, and so their international trade is banned.
In Sri Lanka, the two species would meet the IUCN criteria for being
‘endangered’ and ‘critically endangered’
the survey of crocodiles by Rom and Zai Whittaker, it was not possible
to determine the status of the crocodiles in the Jaffna peninsula
for almost two decades on account of the armed conflict. However,
with the declaration of a ceasefire, it was possible to travel to
the north and carry out surveys. Our preliminary survey of the Thondamanaru
lagoon in the Jaffna peninsula confirmed the presence of both species
of crocodile. Locals refer to them by their vernacular names Chaanakan
(the 'freshy') and Semmookan (the 'salty'). Both species were recorded
from the northern extension of the Chundikulam Sanctuary, while
freshwater crocodiles was known to be present in Pallai. Two crocodiles
were killed in early January at Naharkoil. Crocodiles were also
recorded from places such as Varani, Ampan, Maruthankerni, Maanviluntha
kooru, Mulliyan and from the extensive mangroves along the Thondamanaru
Although crocodiles are excellent predators, they are
often indiscriminate and opportunistic feeders. They hunt at night,
waiting half-submerged for land-bound prey such as spotted deer,
wild boar, or even a buffalo calf to disturb the water surface.
They have specialized sensory organs known as dome-pressure-receptors
on their faces that can detect tiny disruptions in the surface of
water. Prey varies from crabs, prawns or shrimps in the case of
hatchlings, to fish, aquatic birds and large terrestrial herbivores
in the case of adults. Before a croc can attack a large herbivore
in water, it needs to rotate its head sideways by 45 degrees. This
is achieved by making the rest of the body rigid through the contraction
of the longitudinal muscles along the back and tail. This results
in 'tail-arching' which allows the head to be swung efficiently.
The muscles that help close the jaws are strong and extremely powerful,
while those that are involved in opening them are weak.
can hear over a wide range of frequencies, and are among the few
reptiles that have a voice. They have also good eyesight and their
vision is greatly enhanced by a layer of guanine crystals behind
the retina, known as the retinal tapetum, which reflects any light
that reaches it, and so intensifies the image, making it easy for
crocs to see even under low light intensity. Furthermore, in a croc
that is 5 m long, the two eyes are separated by only 7 cm. Such
close placement of the eyes makes it possible for crocs to have
binocular vision - a feature that helps estimate depth.
have a very good sense of smell. They have no salivary glands and
their fleshy tongue is immobile since it is attached along its length
between the lower jaws. Despite its size, a croc usually cannot
eat larger prey whole given its small stomach. This is why it often
stashes its prey underwater or in a swampy area, and returns at
intervals to feed. Prey is swallowed in large pieces.
unusual feature of the stomach is the presence of stones or gastroliths,
which help in digestion by tearing up the parts of prey swallowed.
The digestive enzymes are so strong (low pH levels) in the stomach
that they can digest even bones. But their activity depends on ambient
temperature. If the outside temperature is too low, crocs may stop
feeding completely. At low temperatures, food will rot before it
can be digested and assimilated. Crocs are efficient in converting
what they eat - about 22% on a fish diet - and can go for long periods
without feeding, during which they rely on the fat stored in the
tail. They can also feed on carrion. Teeth may be lost but they
are replaced throughout life.
Crocs are polygynous, with single males mating with a
number of females. Dominant saltwater crocs occupy well-defined
territories from which other males are excluded. Such territories
may include the nesting sites of several females. Stimulus for ovulation
is the onset of the rainy season. Mating always takes place in water
and is preceded by courtship. 4-6 weeks after mating, the female
would start laying 10-50 hard-shelled eggs. Freshwater crocs are
'hole nesters' in that the females excavate a hole into which they
would deposit their eggs, like turtles. Saltwater crocs are 'mound
nesters" since they construct a mound using earth and vegetation,
in the centre of which the female would deposit her eggs.
crocs are also 'pulse nesters' - all the females within a population
would nest within a few weeks. Saltwater crocs are said to be 'prolonged
nesters' since nesting may go on for 6 months. Since sex is determined
by temperature in crocodiles, females select their nest sites with
great care. Often, a number of 'trial nests' are made to reduce
the risk of predation. As hatching time approaches, the young crocs
would produce a cheeping sound to alert the mother who would come
to excavate the nests and carry the newly hatched young in her mouth
eggs fail to survive to produce hatchlings due to desiccation, infertility,
flooding, predation or inadequate gas exchange. Out of 1000 eggs
that hatch, only 8 crocs would survive up to 5 years of age! But
crocs, like elephants, continue to grow all their lives. When they
reach a certain length, they expand in bulk. Although parental care
is rare among reptiles, female crocodiles are very protective of
their nests. Maternal behaviour includes nest defence, nest opening,
manipulation of eggs to release hatchlings, and mouth transport
of eggs and the young.
That the crocodiles have managed to survive in the Jaffna
peninsula points to their tenacity and ability to bounce back if
and when conditions in their environment improve. The 18-year civil
war may have been a blessing in disguise to the crocodiles since
most of the people were moved from the peninsula and resettled in
the Vanni region. This reduction of human pressure enabled the crocodiles
to return and recolonize the Thondamanaru lagoon. It also reduced
the hunting pressure on crocodiles.
the Thondamanaru lagoon and its mangroves represent the last stronghold
of the crocodiles in the Jaffna peninsula. More intensive surveys
are needed to identify clearly the range and number of the two species
of crocodiles in the Jaffna peninsula if they are to be conserved.
difficulty in surveying wildlife in general and the crocs (and birds)
in particular is that the use of binoculars is prohibited by the
military. This greatly restricts the ability to identify species
at a distance. Though ordinary fishermen are using GPS to catch
fish in the sea the military has banned the use of binoculars in
in Sri Lanka have a poor image and hence their long-term survival
in the wild will depend on the attitude and tolerance of the local
people. Rural people are often intolerant of large and dangerous
predators in their backyard. Thus there is a need to provide incentives
to the local people to maintain crocodiles and their habitats in
have declined both in range and number since they were indiscriminately
hunted in the past for skin and meat. Intensive inland fishing has
also led to the decline of freshwater crocs in some areas, and crocs
also get entangled in fishnets and drown. Contrary to the popular
belief, crocs are beneficial to reservoir fishery. They do control
a number of avian predators of fish such as storks, darters and
crocodiles needs relatively large, diverse and undisturbed wetlands,
since crocodiles increase in size from hatchlings to adults through
several orders of magnitude. Reclamation of swamps, draining of
coastal wetlands, conversion of mangroves to prawn farms, and the
removal of riverine forests are some of the threats faced by crocodiles.
are especially important for the protection of hatchlings which
seek shelter among the roots of Rhizophora spp, where they are safe
from predators. Mangroves in the Jaffna peninsula are extensive
and they support a variety of wildlife. They provide support for
the marine food web, nurseries for valuable fish and crustaceans,
and habitat for plants and animals.
"keystone species", crocodiles are important for the maintenance
of ecosystem structure and function. They should also be regarded
as "flagship species" for the conservation of the mangroves
in the Jaffna peninsula.