The genus Cyrtodactylus consists in the neighborhood of 250 species and stands out as the most species-rich in the entire Gekkonid family. These geckos are immediately distinguished by the non-flattened digits that are arched, a feature that has earned them the name “bent-toed geckos” and “bow-fingered geckos”. Nine species are currently known from the Philippines, the most widespread of which is C. philippinicus, otherwise known as Philippine bent-toed geckos.
A number of bent-toed geckos have figured prominently in herpetoculture, particularly in the European Union, and these mostly involve the attractive Thai species C. peguensis. In recent years, the cryptic Malaysian species C. elok has joined the list of Cyrtodactylus being kept by dedicated herpetoculturists.
The species was described by Austrian herpetologist Franz Steindachner in 1867 as Gymnodactylus philippinicus. It is the most widely spread of all Philippine Cyrtodactylus species and has been recorded from several provinces in Luzon, southwards to Mindoro and all the way to Dinagat. Two major islands that hold no population of this species, as far as is known, are Palawan and Mindanao. It should however be noted here that these populations may harbor cryptic species which may prove to be independent taxa pending further investigations.
Introduced populations are said to have been established in both Indonesia and Malaysia, although being almost strictly forest species with aversion to human activities, I do not know the circumstances which could have led to such feral populations.
Appearance
Philippine bent-toed geckos are a medium-sized Cyrtodactylus species attaining lengths of about 9.5 cm from snout to vent, with tails that are about as long. Their bodies are quite roust, particularly for males, with rather large heads and slender limbs ending in typical arching toes for which Cyrtodactylus are known for.
The greyish to yellowish-brown dorsum is crossed with brown to blackish broad bands with wavy margins and darker edging, and the tail has alternating white and black cross bars. Small white tubercles dot its back. The head and limbs have variable dark brown blotches. The venter is from yellowish to blackish-grey.
Ecology
Philippine bent-toed geckos are lizards found from mid-elevation mountainous forests to around 900 meters above sea level. In particular, they prefer regions of either high rainfall or misty zones. This preference seems to have to do with a high moisture requirement than temperatures, as I have also found this species in the province of Quezon at an altitude of only about 200 meters.
However, due to its close proximity to the sea and thus the influence of the Massenerhebung Effect, patches of mosses are prevalent, especially near bodies of water. These bryophytes are a sign of high rainfall and absorb water, thus allowing a more humid climate. I have so far not located the species in areas with a prolonged dry season.
These geckos are also found in limestone forests, caves, as well as near human habitation. However, these altered and man-made habitats are not as favored as intact ecosystems. Compared to other rather common forest gecko species such as the Tokay gecko (Gekko gecko) and the Kikuchi’s gecko (G. kikuchii), Philippine bent-toed geckos are acutely more averse to human activities.
The lower, the better
Cyrtodactylus philippinicus are closely tied to the ground. Despite being arboreal, they are often found 2 meters and below towards the ground, which may hint at diet preferences. Field observations also suggest that these geckos lay their eggs inside rotting logs on the forest floor. Individuals from my group also prefer to anticipate prey low down.
Diet
Indeed, when presented with flying prey items such as moths, these geckos will exhibit a strong inclination to wait for these to blunder within close range than actively stalk like many geckos do. Unsurprisingly, such prey items often linger for at least a couple of nights inside the enclosure before finally being taken down by the lizards. When anticipating prey, the geckos will wait in a heads-down position or will stake out a vertical location and wait for extended periods for prey to come by.
The preference for crawling prey may have to do with competition: In all populations I have so far observed, frogs are a major component, and these include species from the genus Kaloula (the arboreal K. conjuncta), Philautus, arboreal Platymantis, and Rhacophorus. Since most of these frogs are usually active hunters that engage flying insects, the switch to a set of primarily roving prey items as well more stationary ones like katydids nearer to the ground may have allowed the geckos to take advantage of a food source otherwise under-utilized by arboreal anurans.
As mentioned above, C. philippinicus are not averse to staying near ground level and this preference has allowed them to utilize even rocks and boulders fringing streams, rivers, and other flowing bodies of water. In these kinds of habitats, roaming prey are much more frequent and easily caught than do flying ones, which are more prevalent during the day than in the nighttime hours (e.g., damselflies and butterflies).
On trees, C. philippinicus also exploit the frond axils of epiphytic ferns in the genus Asplenium. The “nests” formed from around the fronds catch debris and these layers are inhabited by a variety of arthropods and other microfauna, notably worms, which may be in the list of this species’ food items.
In the province of Laguna, I have observed arboreal worms in the same habitat as these geckos but definitive proof is still lacking. From my current observations, food requirements of these animals are fewer compared to other more active gecko species.
Can geckos see magnetic fields?
An interesting ability of this species is its capability to return to its home range after being relocated on other sites, using magnetic compass orientation. Simply put, there are animals — C. philippinicus included — that can perceive changes in the Earth’s magnetic field for orientation, according to Carina Marek and colleagues in a 2010 article for Salamandra.
One of a kind
Philippine bent-toed geckos are markedly nocturnal, and activities are confined in total darkness. This is in contrast to other common gecko species which are rather crepuscular, or beginning their activity period at dusk.
Behavior
Philippine bent-toed geckos are easily spooked compared to many other gecko species, a trait that was not lost on American herpetologist Edward Taylor in 1922 when he authored The Lizards of the Philippines and said, “They take fright easily, apparently not relying much on protective coloration to escape observation”.
To approach one for photographs, one has to tread slowly and carefully to avoid distressing the geckos. When agitated, they are much more inclined to dash to any nearby retreat rather than putting as much distance as they could to a perceived threat.
The edgy behavior tones down a bit in captivity and the geckos may stay out in the open despite one’s presence, but any sudden movement and they are out of sight again. In the wild, these lizards are usually found singly and far from one another, perhaps to minimize competition; at higher elevations, insect numbers are fewer than at lower altitudes and so competition for food resources are much more pronounced.
The breeding dynamics of this species is still unknown and to the best of my knowledge, C. philippinicus has not yet entered herpetoculture. However, with the speed with which habitats are being converted for agriculture or destroyed for the extraction of timber and minerals, we may need to figure out a way to breed them in captive conditions as a back-up alternative in case of possible localized extirpations.
This appeared in Animal Scene magazine’s January 2020 issue.
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– Little wonder: The frog-eyed gecko
