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It's long been known that humans and birds can recognise sounds while they are still embryos, and now experts have discovered snails even learn survival skills before they hatch.

Pond snails are able to sense chemicals released by their predators while they are still embryos in the egg, scientists claim.

And the tiny creatures even alter their behaviour, giving them the best possible start in life when it comes to avoiding danger.

Responsive: Pond snails are able to sense chemicals released by their predators while they are still embryos in the egg (pictured), scientists claim, and the tiny creatures even alter their behaviour after they hatch

Researchers at Aberystwyth University, the University of Exeter and Plymouth University have shown that when snails are exposed to predator smell during this very early developmental stage, they are better able to avoid predatory fish once they hatch.

This 'pre-programmed' response may be extremely important for snails to be able to survive just after hatching when they are small and vulnerable.

Pond snails are crucial to freshwater environments and help to control the growth of plants, which can clog up rivers.

But they are under threat from invasive predators including the killer shrimp, originally from Turkey, and signal crayfish.

Understanding how snails are able to learn about predators at different life stages, from embryo to adult, gives a good indication about how capable they may be of surviving under these increasingly risky conditions, the experts said.

When snails are exposed to a predatory smell, signifying the presence of tench (pictured), during the very early developmental stage, they are better able to avoid predatory fish once they hatch, the study found

To get an idea of how snails respond to predators, the team looked at how pond snails, Lymnaea stagnalis, reacted to a smell from a predatory fish called tench.

The snails were exposed to the predator smell throughout their embryonic development in egg capsules, according to the study, published in the journal Freshwater Biology.

Once they hatched out, they were kept in a predator-free environment for a week and were then tested for how they responded to predator smell.

Snails exposed to the smell as embryos reacted strongly to it when they re-encountered it as juveniles, by crawling out of the water to get away from the dangerous source of the stench.

'We were quite surprised at how well the snails were able to learn during this very early phase of development,' said lead author Dr Sarah Dalesman of Aberystwyth University.

'The ability to respond to potential predators while still in the egg may be extremely important in allowing young vulnerable snails to survive.

'We also found embryos exposed to the predator smell hatched out at a smaller size than those kept in predator-free conditions'.

This mirrors effects of stress on development in mammals, including humans, where foetuses of stressed mothers are often smaller at birth than their more relaxed counterparts.

Dr Simon Rundle, of the University of Portsmouth, explained: 'One of the most important findings in this study was that there appeared to be a genetic component to the snails' behaviour, with those animals whose grandparents had experienced fish predators in the wild showing the biggest response'.