Estuarine crocodiles are sea swimmers that travel very long distances using tidal and even ocean currents.
“OF all the reptiles of Borneo by far the most important, when it is considered in relation to man, is the Crocodile.” Robert WC Shelford wrote this in his book ‘A Naturalist in Borneo’, which was published posthumously in 1916. No truer words have ever been written!
It was in 1999 on Sabah’s Kinabatang River that my first close encounter with a crocodile happened as I took a shallow bottomed boat, when what I saw as a drifting log was identified by the boatman in shriek of “Buaya!” Immediately he started the outboard motor and this stealthily approaching reptile faded into the distance. My next encounter in the wild was whilst, in 2006, at a camp in the Masai Mara National Reserve in Kenya when I observed a very large Nile crocodile basking in the late afternoon sun on a pebbled slip-off slope on the Mara River. It was awaiting the Mara river-crossing of the seasonal migration of wildebeests, zebras, and antelopes from the Tanzanian Serengeti National Park to Masai Mara.
As we have seen on TV documentaries, these crocodiles seize, in frenzy, weaker young and elderly mammals. Eight years ago, I accompanied a group of Kuching teachers and primary students on a field trip to Semenggoh Wildlife Centre. Whilst mildly interested in the orang-utans, they totally focussed their attention on an enclosure housing five or six salt water crocodiles awaiting release into appropriate habitats. Besides the saltwater crocodile, there are two other most threatened species of crocodile in Borneo.
Saltwater or estuarine crocodile
The Crocodylus porosus species was once widespread along the coasts of eastern India, Bangladesh, Thailand, Cambodia, Vietnam, and southern China. Today only occasional sightings are found south of Port Dickson in Peninsular Malaysia but established populations are observed in Sumatra, East Timor, Celebes, Papua New Guinea, the Solomon Islands, with large populations along the north Australian coastline. Not and far from least, the Borneo coastline of East Malaysian states and Indonesian Kalimantan probably see many more than other locations.
Sarawak is world-renowned for its man-eating crocodiles and frequent reports are recorded in this newspaper of crocodile attacks and captures in riverside kampungs. The latter seized for later release by Bomba and Sarawak Forestry personnel together with the help of villagers.
Despite the high losses of humans, here in Sarawak, population densities of these reptiles are largely unknown. Essentially living in coastal brackish waters in mangrove swamps and mudflats along river deltas they are found along the Bako and Santubong rivers and east of Kuching in the Samarahan, Batang Lupar, Saribas, and Sebuyau rivers.
Dimensions and behavioural tendencies
Compared to other crocodile species, this reptile has a wider and larger snout with a pair of ridges running from its eyes along the centre of its snout and a wider body. From young to older male crocodiles its bodily length is between 3.5 and six metres, and weighing from 200kg to over 1,000kg. Much depends upon its habitat, location, and interaction with humans. Mature females are up to 4.3 metres long and weigh between 120kg and 200kg.
Relative to other large crocodile species, this female species is slightly smaller. It is thought that male crocodiles far exceed female dimensions because of their need to protect their territorial rights against other younger marauding males. Unlike other crocodile species, the saltwater croc is a sea swimmer travelling very long distances using tidal and even ocean currents in its quest for ‘greener pastures’ or when a particularly unseasonal cold spell hits a region.
Males reach sexual maturity at about 16 years of age and females at 13 years. Mating occurs when river levels are at their highest, during the wet season. Mound nests are created of a mixture of mud and vegetation with a small entrance in which the female lays between 40 to 60 eggs and then she scratches up mud to close the entrance. Outside, she will guard the nest for at least 80 days accompanied by her male. As soon as she hears the ‘yelpings’ of the hatchlings, she digs out the nest and rolls the eggs in her mouth to remove the newborn. Both eggs and hatchlings are open prey to sudden rises of river levels and to monitor lizards, rats, and sea eagles resulting in only 1 per cent survival rates. A lucky hatchling has a possible life expectancy of 70 years plus.
Bites are bigger than their bellies
A hypercarnivorous apex predator, its huge muscles and tendons at the base of its snout provide this species with the largest bite force of all creatures measuring in laboratory conditions of up to 16,000 Newtons. These lower jaw muscles are so arranged to clamp down on its prey with only weak muscles to allow its jaw to open. Thus it is possible to duct tape or rope its jaws closed but only by professional rescuers, as we see captured in press photos. It can swim at three times faster than any humans, on average at 26km per hour. Robert Shelford observed that it could knock crab eating macaques out of riverbank tree branches by a swish of its muscular tail.
As they mature, estuarine crocodile diets see greater variety ranging from crabs to water birds, mouse deer, rats, otters, pangolins, proboscis monkeys, flying foxes, small water buffalos, and humans. There are many reports in Sarawak of their ventures into kampungs to seize villagers chicken, dogs, and cats let alone children and adults swimming or bathing in rivers. They will even attack turtles and sharks. In northern Australia riverside signs abound warning innocent visitors of crocodile presence.
Crocodylus siamensis is a medium size crocodile that inhabits slow moving rivers, lakes, and freshwater marshlands. — Photo by Marco Almbauer
Siamese crocodile
The Crocodylus siamensis is a medium size crocodile of just over three metres long, weighing up to 70kg, and inhabiting slow moving rivers, lakes, and freshwater marshlands. Ranging over the rivers of Southeast Asia, particular concentrations are found in Borneo, Cambodia, and Java. Their actual habitats are not clearly demarcated for few studies have been made and thus they are classified on the International Union for Conservation of Nature (IUCN) Red List Appendix 1 of Cites as critically endangered. Its green colouring and smooth, unridged snout make it distinct from other species but they too breed in the wet season.
Between five and 50 eggs are laid carefully in their nests, which are composed of plant litter bound together with mud. As with saltwater crocodiles, both females and males guard the nests until incubation time when the female assists the hatchlings out of their eggs and gently carries them in her jaws to the nearest freshwater location. Feeding mostly on fish, snakes, amphibians, and small mammals, they tend to be wary of and unaggressive towards humans with only a handful of attacks recorded.
Threats to their very existence
Until a recent ban, commercial crocodile farms in Thailand and Cambodia, at Tonle Sap, have relied on the capture, in the wild, of this species to produce skins for export markets. Today the major threat to this species is the reclamation of wetlands for rice cultivation with inevitable pesticide use and cattle farming. Hydroelectric dam constructions, leading to a loss in wetland habitats, could see a 50 per cent loss of breeding colonies within a few years.
All is not lost
Various governmental schemes are now in place for the protection of Siamese crocodiles, ensuring the survival of a true breed throughout its habitats in Southeast Asian countries. Cross breeding with saltwater crocodiles on crocodile farms has now been banned.
Borneo crocodile
Very little is really known about the Crocodylus raninus species, which was first identified by Muller and Schlegel in 1844 and reidentified as a valid species through the study of crocodiles in museum collections by Charles Ross in 1990. Hitherto this species had been misclassified as the estuarine crocodile but it was quite distinct and was to be found only in freshwater rivers.
Could it be that this species still exists? If so, then a likely environment is in the Heart of Borneo away from human interaction. There lies further fieldwork by reptilian experts.
Fortunately in Malaysia crocodiles are conserved and protected reptiles with heavy penalties imposed on hunters and traders. It is inevitable that attacks on humans and domestic animals and birds become more frequent especially in estuarine locations. There, as population increases so the crocodile’s natural habitat decreases.