The great amphibian migration

Migrating with purpose
We don't have wildebeests migrating across the Surrey grasslands but we do have frogs, toads and newts that make, the annual trek to a pond or other watery habitat to breed. Each year, often on the first damp nights of late winter, something remarkable happens across Britain. As temperatures rise above about 5°C and rain softens the ground, frogs, toads and newts begin ancient journeys back to water. Their destination: the ponds where they were born. 

For many of us involved in pond watching these movements feel almost magical — sudden, purposeful, and deeply rooted in instinct. But behind the wonder lies a growing body of ecological evidence explaining how and why these migrations occur.

The Common Frog is often the first amphibian to move. In southern England, migrations can begin as early as February. They travel mostly at night, especially on warm, wet evenings and can travel between 100 metres to over 1 kilometre from overwintering sites. While toads may travel up to 2–3 kilometres to breeding ponds migrating en masse over a few nights, newts generally migrate over a few hundred metres.

How do they do it?
On a mild, wet evening in late winter, when the air smells of damp soil and the ground shines under streetlight or moonlight, something ancient is stirring. Frogs, toads and newts are on the move. But how do they know where the water is? Can they actually sense it? The short answer is: yes — but not in quite the way we might imagine.

Amphibians use landscape structure to guide their movement. They have a preference for descending slopes - water collects in the lowest topographic areas and they tend to follow linear features (walls, hedges, field margins).

Amphibians have extraordinarily sensitive skin. Unlike mammals, their skin is permeable and must stay moist. This makes them finely tuned to changes in humidity. They can detect subtle differences between damp and dry ground and are strongly drawn to cool, humid conditions. Water bodies create slightly cooler, more humid air and damp soil nearby. At short range — within a few tens of metres — amphibians can follow these moisture gradients. In effect, they move towards comfort: away from drying conditions and towards humidity.

They also have a keen sense of smell. Research suggests that frogs and newts can recognise the chemical signature of their home pond. This helps explain why many individuals return year after year to the very same breeding site. It is less about “finding any water” and more about returning to known water.
 
But what if an amphibian were placed in a completely new habitat?
If suitable water lies nearby and the landscape is connected by hedgerows, rough grass, woodland edges or ditches, there is a good chance that an amphibian would eventually find water. Amphibians tend to follow natural linear features and often move downhill, where water is more likely to collect. However, they are not long-distance water detectors. Beyond a few hundred metres — especially across roads or dry open ground — their chances of successfully locating a new pond decrease sharply.
This is why pond networks are so important. A cluster of ponds within a few hundred metres of one another allows amphibians to expand gradually and safely. Isolated ponds, by contrast, are much harder to discover and colonise.

Young froglets and toadlets, which sometimes emerge in their hundreds on warm, wet days, disperse widely into surrounding habitat. They are not immediately searching for new ponds. Instead, they spend several years maturing on land before returning — often to the pond where they themselves began life.

So yes, frogs, toads and newts can sense moisture. They can detect humidity and recognise familiar water chemistry. But their abilities evolved in landscapes rich in wetlands — marshes, meadows and pools scattered across the countryside. In such landscapes, water was rarely far away.

When we create ponds — especially clusters of small, fish-free garden ponds — we are not simply adding water. We are restoring the subtle environmental signals that amphibians have evolved to follow.

Visit our Amphibian webpage

This amazing movie by wildlife photographer Robert Fuller is a glorious celebration of our humble frog.

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4Bs Amphibian Survey & Talk
Where are our frogs? Its a question we would like to answer. If you would like to contribute to our Amphibian Survey across the villages of Betchworth, Buckland,  Brockham and Box Hill, please send your sightings, and photographs of frogs, toads or newts if you have them, to biodiversityinitiative1@gmail.com with location information.


Local amphibian expert Rick Anstis is supporting our work. He is giving a talk to help us launch our survey. A recording of the talk will be posted here.