The reproductive models of animals can be categorized into three types, based on the supply of nutrients to the embryos and the method of parturition:
(1) Viviparous, the embryos are nourished by the placenta of the mother, and grow to full infant size before parturition (e.g. cows);
(2) Ovoviviparous, the embryo supplies its own nutrients and remains inside the maternal body until fully grown (e.g. Indian Forest Skink);
(3) Oviparous, the embryo supplies its own nutrients, matures in an egg and incubates through ambient temperature (e.g. short-legged japalura).
Nowadays, scholars studying lizard reproduction no longer categorize species by embryo development; instead they group the lizards according to their parturition morphologies. For example, lizards born from eggs are oviparous and lizards that born as infants are viviparous. The mode of reproduction of the Indian Forest Skink belongs to the latter, viviparous. What determines the modes of reproduction in a lizard? Why are some lizards viviparous and some oviparous? Is it related to temperature? Are the skinks in tropical or subtropical zones oviparous? Are the skinks in cold climates viviparous? Do predators influence their modes of breeding? Aside from the Indian Forest Skinks, other lizards that inhabit the alpine regions of Wushe, including Five-tailed skinks, short-legged japaluras, Swinhoe's japaluras, Formosan grass lizards and Hart's glass lizards, are all viviparous. Why do these lizards select different modes of reproduction in an environment that is equal for everyone? Questions and issues of evolution, mentioned in the above, have yet to be answered.
The Indian forest skinks were first discovered in 1912 by Van Denburgh, an American. The holotype specimen was collected from Guanziling, Tainan County , and is now preserved at the California Academy of Sciences. These lizards are distributed in Southern China and the Indochina peninsula. In Taiwan , they are widely distributed, ranging from plains to areas 1200 above sea level. The mature individuals weigh between 22 grams (females with embryos) and 5 grams, and the body length measures between 60 to 90mm .
Diet
Indian forest skinks have a diverse repertoire of diets, ranging from annelids to insects. The invertebrates in the detritus at the bottom layer of the forest are also enjoyed by these lizards. I have once seen a forest skink, mouth full of earthworms, quickly dart into the leaf mould when it sees me approach. I have the habit of leaving any feasting animals (or humans) to their own business. During summer and spring, the thorny polygonum on the mountain sides bloom with pink flowers, attracting bees and butterflies to their nectar. These lizards will wait patiently in the polygonum bushes and prey on these insects. They store everything they ate as energy, however they do not store it in adipose tissues like other lizards (e.g. Hsuehsan grass lizard). Instead, they store it primarily in their livers. The liver mass of an Indian forest skink reaches its maximum during August and September, months before its scheduled hibernation. Liver mass drops to its lowest during reproductive months from March to July, especially in females; their liver masses drop to the lowest during June, their spawning period.
Color
The forest skinks are colored brown, which help them move about in fallen leaf piles. If not for their highly sensitive nature toward invasions, we would have a hard time finding them among the leaves. The high sensitivity of these lizards ensures their survival from predators like snakes; however, it is also our clue to their whereabouts. Once approached by an intruder, these lizards immediately react and escape, either hiding in leaf piles or darting up the mountain sides. If it's the former, then we may stand a chance catching them, although it's a slim chance; if it's the latter, then the chase is unlikely, due to their incredible speeds and the thick patches of thorny polygonums where they hide from. Therefore, few specimens can be caught between the cliff sides, which can range from 2 to 3 km long. The skinks awake from hibernation in March, and disappear in September to October when temperature gradually drops.
Habitat
These lizards dwell on the bottom layers and edges of forests, preferring hiding places like the fallen tree bark on the grounds. These areas provide them with ample food and excellent shelter; we often found signs of forest skink activities on tree bark that has fallen onto roads or lake sides. The forest is a humid and warm place, which gives birth to many types of animals, especially the shredders that feed on detritus and rotten leaves. The time needed for the leaves to decompose and their food energy to return to the food web is long; however, if these leaves were first broken down by shredders, then the skinks eats these animals, and predators like snakes and birds prey on these lizards, the flow of energy will be accelerated. Therefore, these lizards play an important role in the balance of food chain in the forest ecosystems. There are a few five-tailed skinks that also dwell on the bottom forest layers, but their numbers are not as many as the forest skinks which dominate the area.
Activity
As mentioned before, Indian forest skinks are highly sensitive to foreign intrusions. They are incredibly agile, able to escape up the mountain sides as high as 3 -4 m above ground. They are usually gone by the time we find their presence. These lizards have different feet structures than the japaluras; forest skinks have shorter feet, their bodies are closer to the ground and are adapted for running; japaluras have longer feet and sharp claws, suitable for climbing. During the two years of the study period the author has never seen a forest skink climb up a tree.
Breeding
After the monsoon seasons have passed, the Indian forest skinks reproduce primarily during the months of June and July. Mature eggs can be observed inside female bodies during April, and by June the infant lizards take shapes in fully grown embryos. The infants are born in July, and can be seen everywhere in the wild. The juvenile lizards weigh about 0.36 grams and measures 28mm from snot to anus. They can grow rapidly; the body weight increases to 1.15 grams and the length up to 38mm after a month. Females can give birth to between 4 and 11 juveniles individually. Based on data from 20 female skinks, it was found that the number of spawning is positively correlated with body length; those that are larger can give birth to more juveniles. This is in stark contrast with the species of Agamidae. The evolutionary significance of this development is yet to be delineated.
To summarize, the reproductive cycle of an Indian forest skink can be grouped into the following: (1) active reproductive periods, March to July, (2) Energy storage, August to September; (3) Hibernation periods, October to February.