Part II on Sri Lanka’s Crocodiles: Behavioral traits of an apex predator

Picking up from our last piece on Sri Lankan crocodylians, the following blog shares insights to the traits of our apex reptilian predator in hunting its prey and attacks on humans. Having existed virtually unchanged for the past 100 million years, the Saltwater (‘salties’) and Marsh (‘Mugger’) crocodiles that are found in Sri Lanka have been identified over recent years to display traits distinct to each species. 

Habitat

In Sri Lanka, Saltwater crocodiles are found in rivers and lagoons along the coastal belt of both the dry and wet zone, outside of protected areas, and have also been studied to travel far up larger river networks. The Mugger crocodile has a  wider range, spread across land-locked tanks and rivers in the dry-zone.

Croc tool use Credit- Vladimir Dinets et al Ethology Ecology and Evolution

Photo credit:  Vladimir Dinets et al 2015 / Ethology Ecology and Evolution.

FACT: In Sri Lanka, Saltwater crocodiles number in the hundreds, while Mugger crocodiles number in the thousands; an estimated population of 10,000, and are found across the island.

Temperament

The temperament between the two species has been known to vary; while Mugger crocodiles have been observed to show a lighter temperament (due to being more social), the Saltwater crocodile has been observed to display a more aggressive temperament, owing to its territorial nature. Both crocodylians however, are known to be man-eaters.

Hunting

Crocodylians are opportunistic hunters. A crocodylian carries between 300 to 400 kilograms of strength and power behind each attack, but having the slow metabolism that they do, and relying on the sun’s heat for strength, attacks are calculated with extreme precision; its most famed method of hunting is to lie low till prey come their way. Some will actively seek and hunt prey such as frogs and fish in drying pools. Crocodiles and alligators are known to be the only reptiles to use tools: the Mugger crocodiles and the American alligator have been observed to balance twigs and sticks on their snout to lure birds such as Egrets and other wading birds during their nesting season. Their highly camouflaged bodies help them stay partially submerged without detection; excellent night vision and sense of smell of prey from as far as two to three kilometers away, add to the crocodile’s hunting game.

IMG_5878

According to Crocodile researcher Dinal Samarasinghe, domed pressure receptors  (also known as integumentary sensory organs) are found in their millions across a crocodile’s body (alligators and caimans have them only on scales around their head), mostly concentrated about the snout. These receptors are highly sensitive to vibrations created by any disturbance in the water, and a single receptor is known to be about 10 times more sensitive than the human finger tip. This cue helps crocodylians easily track swimming prey such as water birds, fish and frogs, even in murky water. It also helps them accurately locate the source of any disturbance and orient themselves towards such source, so a large disturbance, such as splashing while having a bath in a river or washing clothes can attract crocodylians.

Attacks on humans

Being far more territorial, and as a result, more aggressive, Saltwater crocodiles rank high in un-provoked attacks on humans. According to Samarasinghe, a large contributing factor of attacks lies in the distribution of Saltwater crocodiles: they are found outside protected areas of the island; Saltwater crocodiles are mostly found in tidal rivers and lagoons with suitable vegetation, and rarely in national parks.

FACT: In Sri Lanka, 102 attacks on humans by crocodiles have been reported since 2005, the majority of which have been traced to Saltwater crocodiles and have not been fatal.

Bathing by river banks

Much of the island’s rural population use natural water bodies for bathing, washing cooking utensils, bathing pets, or washing clothes or machinery. This is especially common in poorer, farming communities across the island that depend on water banks for their livelihood, resulting in a high frequency of attacks and conflict between humans and crocodiles. Coupled with this, a culture of travelers jumping into rivers and water bodies, unaware of the presence of crocodiles adds to the conflict.

Wrong time, wrong place

The significance in timing of attacks on humans has also been observed in the recent past; dawn and dusk are reportedly the peak times of crocodylian attacks on humans, a time in which human activity is at its peak, at these water bodies.

Self-defense?

What can you do if you get grabbed by a crocodylian in the water? There’s not much to be done according to Samarasinghe, as a crocodylian will not allow much time for you to take a breath between capturing you and dragging you into the water to drown. The sheer strength of a crocodile can out muscle any man, especially when it’s in the water. “You can try to put your fingers in its eyes or hit it on the nose, as both are sensitive areas. If you have a limb caught in its mouth, your best bet is to push it down even further down its throat, which might cause it to gag and release you, or if you can grab hold of a stick, keep hitting”!

Photo credits: Dinal Samarainghe 

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