The question of why some animals are venomous is a very good one. Why would an animal possess venom so potent, that it could kill a human being, yet it has no intention of eating us? It all comes down to Natures arms race.
The answer lies in the millions of years of evolutionary pressure that an animal has been living under, developing, honing and shaping its adaptations, behaviour and lifestyle. Through evolutionary pressures, animals have developed stings, fangs, pincers, venom spraying, cytotoxic venom, haemotoxic venom and neurotoxic venom.
Animals are venomous for two main reasons:
- To catch prey.
- To defend themselves.
Venoms are often designed to immobilise prey. This ensures that once the prey is stung or bitten it cannot escape or cause harm to the predator.
Prey is often paralysed and not killed. Paralysed prey can be stored for a longer period of time compared to dead prey. Spiders will often store captured prey in their webs, to be consumed later.
Venom is also used as a defence mechanism, to ward off would be threats. When an animal is stung by a scorpion, it learns a hard but valuable lesson. The intense pain and discomfort it experiences is often enough to teach the animal to think twice before attacking the venomous animal again.
It’s interesting that highly venomous scorpions are those that forage for prey at night. These scorpions are more likely to come into contact with predators. If they cannot defend themselves they will be eaten. If they can defend themselves with their potent venom, this trait will be passed on to their next generation. As these scorpions evolve, they become more and more venomous.
Bees use their venom to defend themselves and their hive. While wasps also use their venom for defence, many use their venom to paralyse prey onto which they lay an egg, or for food for their developing larvae.
This race for survival can be best seen in harsh and arid environments. For example, the Kalahari Desert contains some of the world's most venomous scorpions, but it also contains animals such as Meerkats that are almost totally resistant to their venom.
Venom is not the only defence that animals have. Other means of defence include camouflage, sheltering in protected places, warning colouration and displays of aggression.