by Seng Alvin
The Malayan Monitor Lizard, Varanus salvator, is the most common of the three lizard species found in Singapore. It is also the largest, growing up to 3 meters in length. They feed on crabs, fish, frogs and small vertebrates. They are also not fussy eaters helping to clean up rotting fish and carrion.
As an apex predator, their numbers have grown in many parts of Singapore including Pasir Ris Park, my backyard. I likened them to “gangsters” here, attacking all the other species in the park whenever there is an opportunity
One such opportunity came on the morning of 10 March 2021, I was on my usual birding walkabout stopping first at the main bridge across Sungei Tampines. Every thing was calm and peaceful. A few Black-crowned Night Herons, Little Egrets and Striated Herons were happily foraging by the bank of the river.
Suddenly I saw a Black-crowned Night Heron, Nycticorax nycticorax, dropped into the river. I did not see how and why it fell. It was struggling in the water trying to get out, sending ripples across the river. This attracted a Malayan Water Monitor lurking nearby. Immediately it swam over and start attacking the heron in the water. There was nothing I can do except to document the attack.
The heron put up a fight and managed to fend off the monitor lizard. But it was clearly injured from the bite of the lizard. I can see a few of it’s white feathers floating in the water.
The monitor lizard bid its time, circling the wounded heron waiting for the right time to attack again. It’s main concern is from other lizards trying to steal its prize.
After a few minutes the monitor lizard launched a second attack. This time round the heron was too weak to resist. It took less than a minute. It was game over for the heron.
With it’s prey in its mouth, the lizard quickly dragged it to the bushes along the river bank to finish the meal away from the prying eyes of the other lizards. After close to an hour, this “gangster monitor” came out of the bushes with the half eaten carcass and swam across the river, showing off its trophy to the many birders and visitors to the park.
While we have to accept that this is part of the life and death cycle in the natural world, where predation is nature’s way of maintaining the biodiversity, this balance can easily be unhinged if a dominant species expanded out of proportion and becomes a threat to the other wildlife in the ecosystem.
The Black-crowned Night Heron is listed as critically endangered in the 2008 Singapore Red Data Book. The main reason is the destruction and disturbance of its feeding and nesting sites and pesticide poisoning. Our largest colony of 1,200 birds at Khatib Bonsu was wiped out in July 1990 when officials from the Ministry of Environment’s Vector Control and Research Division (VCD) start fogging the mangrove island continuously for months in response to complaints of culex mosquitoes. Since then only a few smaller colonies of 20 odd pairs were found at Jurong Lake, Sungei Buloh and Pasir Ris Mangroves. We need to protect all the breeding sites across the island if we are to see this nocturnal heron survive and thrive.
Reference: Nick Baker & Kelvin Lim. Wild Animals of Singapore.
Yong Ding Li, Lim Kim Chuah and Lee Tiah Khee. A Naturalist Guide to the Birds of Singapore.
G.W.H Davidson, P.K.L. Ng and Ho Hua Chew. The Singapore Red Data Book.
Lim Kim Seng. Vanishing Birds of Singapore.