Size and Shape

All snakes have fundamentally the same form, long and thin with no limbs. Yet, different species can differ considerably in size, and there is even some difference in shape. The smallest snakes may be barely longer than a human finger, while the largest can extend five or six times the height of a person. These variations are a result of natural selection as evolving species have adapted to different environments and ways of life.

Large Snakes

The six largest snakes belong to just two families, the boas and the pythons. The two largest species are the Green Anaconda and the Reticulated Python. The python is usually regarded as the longest, growing to about 33ft (10m), but the green anaconda is far heavier. Not surprising, wild stories about the sizes of both species abound. In 1907 explorer Sir Percy Fawcett claimed to have killed an anaconda in Brazil measuring 62 ft (18.9 m).

Somewhat smaller are the giant pythons from India and Burma, Python molurus, and from Africa, Python sebae. Both species reportedly to grow to 20 ft (6m), although large specimens are becoming rarer as their habitats dwindle. The equivalent snake in Australia is the amethystine python, Morelia amethystina, which has been reliably recorded at over 26 ft (8 m), although it is more usually 10-13 ft (3-4 m).

The smallest of the “Big Six” is the Common Boa. This has only once been reliably recorded at over 13 ft (4 m) and usually grows to about 10 ft (3 m).
There are few species of large snakes for two main reasons. First, such snakes need to eat a lot, but their size restricts them to hunting by ambush, which can limit the food available to them. Second, snakes rely on outside sources to raise their body temperatures, and large snakes take a long time to warm up. All activity, whether hunting, breeding, or self-defense, is curtailed until they can do so. It is significant that the six largest snakes as well as several other large species, including the king cobra, Ophiophagus hannah, the Taipan, Oxyuranus scutellatus, and the Gaboon viper, all live in or near the tropics. Toward the poles, the average size of snakes decreases, as does the number of species.

Small Snakes

In contrast, there are many species so small that they are often overlooked. Snakes in the three most primitive families – leptotyphlopids, anomalepids, and typhlopids – rarely grow to more than 12 in (30 cm). These families total about 300 species – over 10 percent of all snakes. The smallest may be the Martinique thread snake, Leptotyphlops bilineatus, the longest of which was recorded at just 4 ¼ in (10.8 cm). Small snakes require little food – most eat ants or termites and their larvae – and their bodies warm up quickly. However, their size makes them easy prey.

From “Snake” by Chris Mattison © 1999