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Wagler’s Viper Site - Natural History

Borneo

Newborn from Borneo (Kalimantan), about 19 cm long About 2.5 years old and 50 cm long. Note that some white markings and the red lateral stripe crossing the eye are still present. 8 months later, the female is gravid for first time. The white markings have disappeared, the red band of the head has turned blue, the eyes have darkened, and some more of the green scales on the back have turned yellow or blue. More than 5 years old and about 80 cm long. Yellow and blue coloration is further pronouced. Thailand Captive-bred Thai juvenile female, 1 month old and about 19-20 cm long. Note the somewhat flatened head, which becomes more voluminous when it grows. Same female 7 month old. 15 month old Thai female, 2 years old and about 40 cm long. The typical juvenile coloration is still dominant, but labial scales already show yellow and blue elements. 32 month old. Change to the adult pattern starts by red bars turning black in the mid and posterior part of the body. The head has become broader and bulkier. Like its siblings, this female has become increasingly aggressive, day and night, snapping at everything that appears to be prey and moves. Here, the female is 3 years and 3 months old, about 50 cm long. The hind body already shows the typical adult pattern (yellow and black intensify, green scales become fringed with black), whereas the neck and anterior parts still feature reddish bars. Again, the width of the juvenile red bars does not indicate the width of the yellow bars that appear later on.
Female Wagler’s vipers from Thailand appear to develop slower than Sumatran females (see Table below), which may complete ontogenetic change at 2 years of age. It also appears that adult Sumatran females can become longer and heavier than their Thai counterparts. However, regardless of geographical origin, when females are only 2-3 years old, they are probably not ready for breeding. I never found gravid females of this stage in the wild. Gravid females were usually about 60-100 cm long. The table (below) shows a comparison of increase of body weight between individuals from southern Thailand and northern Sumatran, all born and raised in captivity. Interestingly, the divergence in growth rates between males and females can set in after one year already, in the case of Sumatran vipers. In contrast, Thai individuals show this split after 3 years. After 3 years, Sumatran females are much heavier (at around 50 cm body length) than their Thai counterparts.
Similar to Thai populations, Western Malaysian temple pit vipers also appear to develop slower. In the following example, transition to adult coloration was not complete after 3 years.
Juvenile female from Malaysia (about 40 cm; exact age unknown) with early indications (black spots on the head) of an approaching change in coloration. Same animal 7 months later. The red markings on the back and head have turned black. Dorsal scales gradually become fringed with black. Another 7 months later, yellow elements have become stronger and more scales on the head have turned black. Another 12 months later; the animal is now more than 3 years old. This image of a juvenile female from Penang (taken in the Snake Temple) illustrates that the juvenile red-white markings do not necessarily indicate the full length (or even position) of the transversal bands that appear later on. Here, the adult pattern is indicated by the yellowish coloration. This is why juvenile females with 'male markings' may develop a perfectly normal banding pattern in adulthood. Western Malaysia
© 2004-2021 Thomas Jäkel
Made with MAGIX
Ophiotropics.com
Wagler’s Viper Site - Natural History
Made with MAGIX
© 2004-2018 Thomas Jäkel

Borneo

Newborn from Borneo (Kalimantan), about 19 cm long About 2.5 years old and 50 cm long. Note that some white markings and the red lateral stripe crossing the eye are still present. 8 months later, the female is gravid for first time. The white markings have disappeared, the red band of the head has turned blue, the eyes have darkened, and some more of the green scales on the back have turned yellow or blue. More than 5 years old and about 80 cm long. Yellow and blue coloration is further pronouced. Thailand Captive-bred Thai juvenile female, 1 month old and about 19-20 cm long. Note the somewhat flatened head, which becomes more voluminous when it grows. Same female 7 month old. 15 month old Thai female, 2 years old and about 40 cm long. The typical juvenile coloration is still dominant, but labial scales already show yellow and blue elements. 32 month old. Change to the adult pattern starts by red bars turning black in the mid and posterior part of the body. The head has become broader and bulkier. Like its siblings, this female has become increasingly aggressive, day and night, snapping at everything that appears to be prey and moves. Here, the female is 3 years and 3 months old, about 50 cm long. The hind body already shows the typical adult pattern (yellow and black intensify, green scales become fringed with black), whereas the neck and anterior parts still feature reddish bars. Again, the width of the juvenile red bars does not indicate the width of the yellow bars that appear later on.
Female Wagler’s vipers from Thailand appear to develop slower than Sumatran females (see Table below), which may complete ontogenetic change at 2 years of age. It also appears that adult Sumatran females can become longer and heavier than their Thai counterparts. However, regardless of geographical origin, when females are only 2-3 years old, they are probably not ready for breeding. I never found gravid females of this stage in the wild. Gravid females were usually about 60-100 cm long. The table (below) shows a comparison of increase of body weight between individuals from southern Thailand and northern Sumatran, all born and raised in captivity. Interestingly, the divergence in growth rates between males and females can set in after one year already, in the case of Sumatran vipers. In contrast, Thai individuals show this split after 3 years. After 3 years, Sumatran females are much heavier (at around 50 cm body length) than their Thai counterparts.
Similar to Thai populations, Western Malaysian temple pit vipers also appear to develop slower. In the following example, transition to adult coloration was not complete after 3 years.
Juvenile female from Malaysia (about 40 cm; exact age unknown) with early indications (black spots on the head) of an approaching change in coloration. Same animal 7 months later. The red markings on the back and head have turned black. Dorsal scales gradually become fringed with black. Another 7 months later, yellow elements have become stronger and more scales on the head have turned black. Another 12 months later; the animal is now more than 3 years old. This image of a juvenile female from Penang (taken in the Snake Temple) illustrates that the juvenile red-white markings do not necessarily indicate the full length (or even position) of the transversal bands that appear later on. Here, the adult pattern is indicated by the yellowish coloration. This is why juvenile females with 'male markings' may develop a perfectly normal banding pattern in adulthood. Western Malaysia