Steve's Herpetological Blog

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#SciFri: Why you shouldn’t move spawn between ponds

Every spring, nature lovers across Great Britain (myself included) eagerly await for the first clusters of frogspawn to appear, a sign of the renewal of life in our ponds after the long winter months. For me, it is an undeniable sign that spring has finally sprung! Drawn by a deep kinship with these tiny, jelly-like orbs, many people feel compelled to help by moving spawn to new or seemingly empty ponds, hoping to give frogs a better chance at survival, especially when the frogs have laid their spawn in seemingly hopeless locations. It’s an instinct rooted in care. After all, amphibians have long shared our gardens, thriving in ponds and damp corners with plenty of rough grass. Their lifecycle a familiar rhythm of the changing seasons and many of us are fine-tuned to watch for it. This is the time of year when I am often asked about whether it is wise to move spawn into a garden pond, if frogs haven’t left any behind as a gift. Yet, despite good intentions, relocating spawn can have unintended consequences, disrupting delicate ecosystems and putting the very creatures we cherish at risk. Below, I hope to highlight a number of these and help educate those that may be tempted to move spawn.

Common frogs at a breeding pond in Cambridge surrounded by spawn

Moving frogspawn between ponds may seem harmless, but it can unknowingly spread deadly amphibian diseases, threatening local populations. Chytridiomycosis, caused by a fungal pathogen, attacks the skin of frogs, impairing their ability to breathe and regulate internal water levels, often leading to mass die-offs (which have been observed around the world). Similarly, Ranavirus, a highly contagious and often fatal disease (also known as red leg), causes severe internal bleeding, haemorrhaging and organ failure in amphibians. These diseases can linger in the water, soil, or even on equipment like nets and buckets, making transmission easy but detection difficult. By relocating frogspawn, well-meaning nature enthusiasts may unknowingly introduce these silent killers to healthy ponds, putting entire frog communities at risk. If you want to know more about the disease risks to our native amphibians, may I suggest this helpful review or the Garden Wildlife Health website. Additionally, if you want to become more informed about how to disinfect your equipment to prevent the spread of pathogens between ponds, then please check out these guidelines produced by the Amphibian and Reptile Groups UK and their partners.

Moving frogspawn between ponds also carries the hidden risk of introducing invasive species, which can disrupt delicate ecosystems (such as garden ponds). Small aquatic creatures like non-native snails, insects, or parasites can hitch a ride on the spawn or in the water used to transport it. Invasive plants, such as floating weeds, duckweed or New Zealand pigmyweed (Crassula helmsii) might also be unknowingly introduced, quickly spreading and outcompeting native vegetation. These unintended arrivals can alter food chains, compete with native species, and even degrade water quality, making the habitat less suitable for frogs and other wildlife. By keeping frogspawn in its natural location, we help preserve the ecological balance of each pond, ensuring that local species thrive without the threat of new, potentially harmful invaders.

One factor that isn’t offered considered is that frog populations in different areas have adapted over generations to their local environments, developing genetic traits that help them survive specific conditions such as water quality, climate, and predators. When frogspawn is moved between ponds, it can introduce genes that may not be suited to the new habitat, potentially weakening the local population rather than strengthening it, especially when move across vast distances. This mixing of genetic material can also reduce the natural resilience of frogs to diseases and environmental stressors. Protecting the unique genetic diversity of each frog population ensures they remain well-adapted to their surroundings and better equipped to face challenges like climate change and habitat loss.

Ethically, interfering with wild amphibian populations can disrupt ecosystems, spread disease, and undermine conservation efforts aimed at protecting native species. Wildlife experts and conservation organisations, such as the Amphibian and Reptile Conservation Trust (ARC), strongly discourage the relocation of frogspawn to prevent unintended harm. Legally, while common frogspawn is not specifically protected, the movement of certain amphibian species—such as great crested newts—is regulated under the Wildlife and Countryside Act 1981, making it illegal to handle or relocate them without a license. It is however illegal to sell the spawn of native amphibians and the charity Froglife runs an annual campaign titled #StopSpawnSales to educate the public in this regard. Additionally, if moving spawn leads to the introduction of invasive species or diseases, it could contribute to broader environmental damage, potentially falling under laws related to invasive species control. By respecting natural processes and focusing on habitat conservation rather than intervention, we ensure that frogs and other amphibians can thrive in a way that supports long-term biodiversity.

If frogs are absent from your garden pond, it may be due to a variety of environmental factors that make it less suitable for them. A lack of aquatic plants or sheltered areas can leave tadpoles and adult frogs vulnerable to predators, while fish in the pond may consume frogspawn before it has a chance to develop. Poor water quality, caused by pollution, pesticides, or excessive algae growth, can also deter amphibians from breeding. Additionally, if your pond is too new, it may simply take time for local frogs to discover it and establish a population. Connectivity to other water sources and damp hiding spots nearby are also crucial, as frogs travel between habitats and need safe passage to reach breeding sites. Rather than introducing frogspawn, improving pond conditions by adding native plants, maintaining clean water, and creating nearby refuge areas can naturally attract frogs over time. Advice is plentiful online, but I would probably start with this handy guide produce by ARC.

With all of this is mind, if a pond has no frogspawn, it’s best to improve the habitat (e.g., adding plants or reducing pollutants) rather than introducing spawn from elsewhere. Frogs won’t breed every year and so my skip some springs before returning to the pond to breed. It is during these years that you need to sit on your hands, and not give into temptation to stock your pond with wild spawn for the reasons listed above. Frogs will also lay their spawn in seemingly awful places, but to them, it could be a goldmine. Those rain-filled Land Rover tracks are perfect! There are no predators which drastically increase the odds of their offspring surviving during their most vulnerable stage, tadpoles. Frogs have been doing their thing for approximately 200 million years, it is best to leave them to it. If there are frogs in your local environment, they will colonise your pond naturally using the guidance above.

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