Daily Decay (25th January 2018)

Daily Decay (25th January 2018): Changeable Lizard (Calotes versicolor) @ Lorong Halus

Changeable Lizard (Calotes versicolor) (L) and Green Crested Lizard (Bronchocela cristatella) ® @ Singapore Botanic Gardens

What’s the connection between the Changeable Lizard and the Green Crested Lizard? Final couple of hours to drop by the Festival of Biodiversity to learn more about Singapore’s flora and fauna!

Changeable Lizard (Calotes versicolor)
Lim Chu Kang, 17th December 2015

This Changeable Lizard carcass was impaled on barbed wire. It’s possibly that it had been caught by a Shrike, which are known to use thorns and barbed wire to hold prey in place while smaller chunks of flesh are ripped off and swallowed. This is also a way to cache food, especially if the prey item is too large to be consumed in one sitting. Three species of Shrikes are known from Singapore, the Long-tailed Shrike (Lanius schach) is a resident breeder here, whereas the Tiger Shrike (Lanius tigrinus) and Brown Shrike (Lanius cristatus) are migratory species that appear in Singapore during the migration season.

Changeable Lizard (Calotes versicolor)
Kranji, 16th May 2015

Common Gliding Lizard (Draco sumatranus)
Sungei Buloh, 21st March 2014

This Common Gliding Lizard was still alive (albeit weak and not very responsive) when first spotted in the vicinity of the Visitor Centre of Sungei Buloh Wetland Reserve, but was subsequently found dead a while later that day. Based on the size and bluish colour of the gular flag, this individual was a female.

Three very common non-native vertebrates of Singapore:

Green Chromide (Etroplus suratensis) (Left)
This native of river estuaries and coastal lagoons of southern India and Sri Lanka was first recorded in Singapore in 1995. Since then, it has spread to many coastal areas of Singapore. It’s possible that it was introduced to our waters through escaped or released pets, as the species has been imported in the past for the aquarium trade. Another possible route of introduction is dispersal from southern Johor, where feral populations of Green Chromide also exist. The Green Chromide is a member of the cichlid family, and several other species have also become established here. For instance, Tilapia (Oreochromis spp.) from Africa and the Mayan Cichlid (Cichlasoma urophthalmus) and Midas Cichlid (Amphilophus citrinellus) from Central America are now widespread and abundant in many urban waterways, whereas South American Peacock Bass (Cichla orinocensis) and Eartheater Cichlid (Geophagus altifrons) can be found in several of our ponds and reservoirs. Man-made hybrids commonly called Flowerhorn Cichlids or Luohan are also now present in many locations, due to irresponsible owners abandoning their pets.

Changeable Lizard (Calotes versicolor) (Upper Right)
This lizard is commonly found in open areas such as parks, gardens, roadside vegetation, and scrubland, where it may be seen basking on tree trunks and fences. Able to change the colour of skin to aid in camouflage, the Changeable Lizard is sometimes mistakenly called a “chameleon”. During the breeding season, male Changeable Lizards develop bright orange heads with a large black blotch on the cheek and throat, displaying to females and rival males by nodding their heads and doing push-ups. This lizard, which is widely distributed through much of mainland South and Southeast Asia, was first recorded in Singapore in the 1980s, and likely reached our shores due to accidental transportation of stowaways in cargo and goods from Thailand and the northern states of Peninsular Malaysia. Since then, however, it appears to have displaced the native Green Crested Lizard (Bronchocela cristatella), which used to be commonly seen in urban green spaces. Today, the Changeable Lizard has taken over many of the areas once occupied by the Green Crested Lizard, with the latter largely restricted to forests.

Red-eared Slider (Trachemys scripta elegans) (Lower Right)
The turtle species most commonly seen for sale in local pet stores, this native of the Mississippi River drainage in the United States has been introduced to many areas outside of its original range, often with negative ecological impacts. Rampant abandonment of pets and release of captive turtles as (misguided) acts of religious goodwill mean that the Red-eared Slider is now the most widespread and most commonly encountered turtle species in Singapore, and can be found in large numbers in most urban ponds, reservoirs, and some canals. The large populations seen in some areas are likely to be a combination of continual release of pets, as well as successful breeding in feral turtles. It is possible that the sheer number of Red-eared Sliders has an impact on native turtle species, which may be unable to compete with the Red-eared Slider for resources such as food and basking and nesting sites.

These were some of the many specimens featured at the recently-concluded Festival of Biodiversity 2014, which was held at VivoCity over the weekend.