Learn about the comparison between non-poisonous and poisonous snakes.
Comparison # Non-Poisonous Snakes:
1. Non-poisonous snakes are usually not brightly coloured, but pythons, common sand boa, red sand boa, anaconda, wart snakes (Acrochordus granulatus) etc. are brightly coloured.
2. Shape of head is usually narrow and elongated in non-poisonous snakes.
3. No constriction in the neck of non-poisonous snake.
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4. Hood is absent in non-poisonous snakes.
5. Tail is tapering and long except burrowing snakes. In Typlopidae and Leptotyphlopidae the tail is short and stumpy. In Uropeltidae the tail is very short and rough. In sand boas the tail is also short and blunt.
6. Head scales− Scales on top of the head are large but in sand boas (Eryx conicus) the head scales are small.
7. Dorsal scales− Scales on the dorsal surface are longer but spinal (vertebral) scales are neither larger nor hexagonal.
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8. Ventral scales− Ventral scales are either across the belly completely (e.g. Colubridae), or may not across the belly completely (e.g. Boidae, Uropeltidae)
9. Loreal shield is absent in non-poisonous snakes.
10. Mental shield is small in non-poisonous snakes.
11. Caudal scales− Undivided.
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12. Teeth of non-poisonous snake is uniform and solid.
13. Poison gland is absent in non-poisonous snakes.
14. Non-poisonous snakes have well-developed muscular system.
15. Both lungs are present in non-poisonous snakes.
16. Hypophysis− Hypophyses absent or present on the posterior dorsal vertebra.
17. Streptostylism− Less marked.
Examples− Rat Snake (Ptyas mucosus), Indian Python (Python molurus), Sand Boa (Eryx conicus), Checkered keel back [Natrix (Xenocrophis) piscator], Wolf Snake (Lycodon aulicus), Striped Keel back (Amphiesma stolata) etc.
Comparison # Poisonous Snakes:
1. Poisonous snakes are generally brightly coloured.
2. Shape of head− Head long, triangular and the posterior portion is wide.
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3. Neck of poisonous snake is always constricted.
4. Hood− Present in majority cases; highly developed in Cobra group (Naja spj; absent in Coral snakes, Krait, Russell’s viper etc.
5. Tail− Tail tapers abruptly. In sea snakes (Hydrophidae) the tail is flattened to form an oar-shaped structure and in land snakes the tail is cylindrical.
6. Head scales− Scales on top of the head are usually small.
7. Dorsal scales− Dorsal surface scales are smaller but the spinal (vertebral) scales are larger and hexagonal in kraits.
8. Ventral scales− Ventral scales are usually completely across the belly, but in sea snakes ventral scales are present not across the body.
9. Loreal shield is present and shapes may be variable in poisonous snakes.
10. Mental shield− Fourth one is large.
11. Caudal scales− Mostly undivided except in coral and cobra snakes.
12. Teeth− Most of the teeth are solid and uniform except maxillary teeth which are large, and provided with groove or canal. These large teeth are called ‘Fangs’.
13. Poison gland− Present. Paired poison glands are on upper jaw.
14. Poisonous snakes have less-developed muscular system.
15. Lungs− One of the lungs has either been reduced or absent
16. Hypophysis− Hypophysis developed throughout the vertebral column
17. Streptostylism− Well-marked
Examples− Saw Scaled Viper (Echis carinatus), Common Krait (Bungarus caeruleus), Banded Krait (B. faciatus), Russel’s Viper (Vipera russelli), King Cobra (Ophiopagus Hannah), Indian Monocled Cobra (Naja naja kaothia) etc..