Written collaboratively by participants on our Wild Memories project in Somerset
Winter
Ponds in winter
Written by Paul Arestides, Transforming Lives Trainee
At this time of year, especially January and February, our weather can turn cold with ice, frost and snow. It’s a good idea to keep an eye on our garden wildlife ponds and implement these handy tips below when needed.
Amphibians like frogs, toads and newts tend to brumate on land during the colder weather, so its always a good idea to have spaces of the garden left untouched. Compost heaps, log piles or rocky places are good for them to settle down and help protect them from frost.
If you have a pond, or plan to build one, make it deep enough so it will not freeze completely (at least 60cm for amphibians) frogs may overwinter in the deeper areas, so this will give them the best chance to survive. Invertebrates like beetles, water boatmen and dragonfly larvae will dive to the bottom of the pond and stay dormant in deeper water.
Contrary to popular belief, melting a hole in the ice will not help the amount of oxygen diffusing into the water- although it can help amphibians like newts that need a hole to come up to the surface to breathe. Oxygen can be produced simply by having oxygenating plants growing in the pond. If there is heavy snow, remove this from the surface ice with a brush to allow sunlight into the water- allowing the plants to continue photosynthesising and creating oxygen.
Do not break the ice as this can send out shock waves that can kill overwintering creatures. Tipping warm/boiling water into your pond isn’t a good idea either as this can trigger animals to come out of their brumation state earlier than planned.
For further tips, take a look at our Winter Wild Gardening Campaign page.
Winter Walks
Written by Paul Arestides, Transforming Lives Trainee
It’s the most wonderful time of the year.
Our reptiles and amphibians may be tucked away for the winter, but the month of December is a great time to explore our two public reserves in Peterborough. A cold, frosty morning walk or a leisurely afternoon stroll on a winters day is sometimes what’s needed, especially after the festivities!
Eye Green nature reserve is a 12 hectare site in the village of Eye Green in Cambridgeshire just outside Peterborough. It was originally part of the Northam Brickworks and was declared a nature reserve in 1996. The site has a long history very much connected to the local area. We manage the site for the benefit of our reptiles and amphibians and for the enjoyment of visitors throughout the year. A large lake dominates the reserve with an array of birds, visiting otters and other wildlife around the site.
Boardwalks, which runs along the river Nene, is a 7.8 hectare site owned by Peterborough City Council and Froglife help to look after the site for the benefit of not just reptiles and amphibians, but other wildlife visitors too. It makes for a perfect place to relax, walk along the various trails or go for a run.
Both reserves offer an escape from the hustle and bustle of city life and gives a chance to get closer to nature.
12 Days Wild
Written by Emma Byrne, Transforming Lives Trainee
12 Days Wild is The Wildlife Trusts Christmas challenge designed to get everyone back out into nature for the winter holidays (December 25th-January 5th). The festive period is a great time to make a difference to winter wildlife, including those hibernating such as reptiles and amphibians.
Helping reptiles and amphibians survive the winter requires creating safe, sheltered habitats and safeguarding their natural environments. Here are some effective ways to support them:
Create Hibernation Spots: Construct log piles, rockeries, or compost heaps in your garden. These structures offer warm, protected spaces for amphibians like frogs and toads, as well as reptiles such as slow worms and grass snakes.
Maintain a Winter Pond: If you have a pond, keep a small area ice-free by floating a tennis ball or using warm water to create a hole in the ice. Ponds are essential for frogs and newts in winter, allowing them to hibernate at the bottom in a cool, stable environment.
Leave Leaf Piles and Unmown Areas: Piles of leaves, leaf litter, and undisturbed ground can provide shelter for reptiles and amphibians. They also create a habitat for insects, which can serve as a food source when reptiles become active on warmer days.
Avoid Disturbing Potential Winter Shelters: If you encounter leaf piles, log stacks, or compost heaps, refrain from moving them during winter, as they may be home to hibernating wildlife.
Garden Gently: When gardening, be aware of hidden wildlife. Be careful when moving piles of natural debris to avoid disturbing any hibernating wildlife.
Join a Conservation Effort: Supporting local conservation organisations that focus on habitat preservation for amphibians and reptiles can significantly help protect these species. Many wildlife charities including Froglife, host winter events or need assistance with maintaining habitats during the colder months.
By taking one or two of these small actions over the festive period, you can help ensure these vital species survive the winter.
What our animals are doing to this month
Written by Eve Goddard, Transforming Lives Trainee
Deep Sleep December
During the winter months, reptiles and amphibians – who are ectothermic – (regulate their body heat from the surrounding environment) need to minimise their movement and conserve energy to survive the winter.
After spending summer and autumn fattening up for winter, they will move into locations that protect them from the elements. This may be under a leaf pile, inside a tree hollow, under rocks or at the very bottom of a pond for example.
Once there they will overwinter or brumate. How it brumation different from hibernation? Overwintering or brumating involves periods of rest interspersed with feeding and small amount of movement, if the weather heats up this may prompt more prolonged activity.
Climate change and brumation.
The changes we see to our weather patterns, for example warmer winters have an immediate impact on reptiles and amphibians:
- Leaving brumation earlier, at a time when the species they predate upon are less abundant.
- Premature breeding or spawning may fall before the coldest weather has passed and effect reproductive success.
- Rising temperatures produce longer growing seasons for the plants that need to be managed to maintain pond habitats.
With this in mind, there are many things you can do to help our reptiles and amphibians in the winter months, Click here for a great guide. If you are lucky enough to see one of our species on your winter walks, please don’t forget the Dragon Finder App where you can record your sightings and assist us further with our conservation work.
Croaking Science: Alternative strategies for amphibians – neoteny and overwintering
Written by Dr Andrew Smart, Head of Science and Research at Froglife
People often wonder why they occasionally find tadpoles in their ponds over the winter. This is an example of delayed metamorphosis, which can be advantageous to some individuals, particularly in northern latitudes. In newts we find overwintering larvae and also examples of neoteny when the larval form is retained and, in some cases, mature and reproduce.
The classic case of neoteny in amphibians is the axolotl, which retain their feathery gills into adulthood, becoming enlarged larvae that develop reproductive organs and can produce large numbers of fertile eggs. Axolotls evolved to live in two lakes in Mexico where the water levels were stable and food levels high, enabling animals, lacking the thyroid hormone that triggers metamorphosis, to survive and evolve a life-strategy that was more effective than having a terrestrial stage.
In frogs and toads, there are a range of reasons why tadpoles might be found in a pond in the winter months. The first to rule out is the risk of the invasive species Lithobates catesbeianus, the American bullfrog, which has a larval stage than can be anything from 1 to 4 years. Overwintering of this large, predatory species has been found to have a neutral or negative impact on other amphibians in introduced populations in the USA[1]. Thankfully, the bullfrog appears to have been eradicated from the UK since 2015[2].
If you have other ‘normal sized’ tadpoles in your pond, the chances are that a number of things may have happened: in some northern latitudes, frog and toad tadpoles have been shown to adopt different strategies[3], with some animals metamorphosing early while others delay metamorphosis, remaining in the pond to be able to exploit resources early in the spring , outcompeting a new cohort of smaller tadpoles[4]. As well as food availability and temperature, other unknown factors lead to this strategy[5]. This enables them to produce larger metamorphosed froglets or toadlets which have a better chance of survival through the winter.
So why don’t all anurans follow this strategy? It can be high risk; extreme temperatures could kill animals during hibernation or ponds could dry out before the end of the late summer period and kill all the ‘delaying’ tadpoles. Most Anurans have developmental cues that trigger metamorphosis, linked to the proximity of other tadpoles and to reduction in water level; [6] in the case of ‘drying ponds’ reducing water depth[7],[8] leads to faster metamorphosis and smaller froglets.
Anurans that develop into ‘large’ tadpoles do have the capacity to develop gonads but in the case of Xenopus (the African clawed toad) ‘giant tadpoles’ that occur develop gonads but struggle to release eggs and sperm[9] and in any case, a ‘giant tadpole’ would be an unlikely animal to participate in amplexus. A similar situation occurs in Pseudis paradoxa, the paradoxical frog, which has evolved a ‘giant tadpole’ that metamorphoses into an adult rather than a froglet.[10] The tadpoles have developed gonads that are close to maturity but the authors point out that life stages in Anurans are very different and that the opportunity for full neoteny is unlikely because of the need for behavioural changes to enable successful reproduction.
What about Caudata? There is evidence that some individuals, usually young adults, may move into ponds in the autumn and overwinter[11]. Examples of palmate newts overwintering in ponds in Scotland are well recorded[12],[13], again a strategy to enable a more robust metamorph emerging in the summer to face colder winters.
There are now several well recorded cases of neoteny in smooth newts – in a Norfolk swimming pool, numbers of neotenous newts were found, resembling female smooth newts but with feathery gills[14]. Two of these animals were removed for examination and very quickly metamorphosed to adult newts. The authors of the study suggested a number of possible outcomes suggesting that a change in water quality (increase in iodine) or change in water depth could have triggered the change.
Examples of delayed metamorphosis and also total neoteny have also been recorded at a site in Cambridgeshire, where newt larvae have been seen in large numbers in autumn and early spring, after presumably hibernating in the pond. One of the newts was taken to captivity and laid fertile eggs[15]. This animal did rise to the surface for air, a behaviour not normally linked with neotenous newts, which have fully functioning gills. As in many cases of neoteny, the records were incidental and unable to be investigated in detail.
So overwintering tadpoles and newt larvae may be a way of amphibians having two different life strategies within a population, some animals taking the risk in the pond, some taking the risk overwintering as a smaller sized individual. Neotenous individuals may be taking advantage of a stable environment with significant food sources and low levels of competition as an alternative strategy, but to really investigate this further we need more information on the habitats where these animals are found. If you know of a site with neotenous animals, please let us know by emailing: info@froglife.org
References
[1] Boone, M.D., Little, E.E. and Semlitsch, R.D., 2004. Overwintered bullfrog tadpoles negatively affect salamanders and anurans in native amphibian communities. Copeia, 2004(3), pp.683-690
[2] New strategy launched to protect biodiversity and economy from non-native species – GOV.UK (www.gov.uk)
[3] Tattersall, G.J. and Ultsch, G.R., 2008. Physiological ecology of aquatic overwintering in ranid frogs. Biological Reviews, 83(2), pp.119-140.
[4] McNeill, D.C. and Downie, J.R., 2017. Overwintering of smooth and palmate newt larvae in the Gartcosh Nature Reserve, Scotland. The Glasgow Naturalist, 26.
[5] Walsh, P.T., Downie, J.R. and Monaghan, P., 2008. Larval over‐wintering: plasticity in the timing of life‐history events in the common frog. Journal of Zoology, 276(4), pp.394-401..
[6] Walsh, P.T., Downie, J.R. and Monaghan, P., 2008. Larval over‐wintering: plasticity in the timing of life‐history events in the common frog. Journal of Zoology, 276(4), pp.394-401.
[7] Merilä, J., Laurila, A., Pahkala, M., Räsänen, K. and Timenes Laugen, A., 2000. Adaptive phenotypic plasticity in timing of metamorphosis in the common frog Rana temporaria. Ecoscience, 7(1), pp.18-24.
[8] Laurila, A. and Kujasalo, J., 1999. Habitat duration, predation risk and phenotypic plasticity in common frog (Rana temporaria) tadpoles. Journal of Animal Ecology, 68(6), pp.1123-1132.
[9] Rot-Nikcevic, I. and Wassersug, R.J., 2004. Arrested development in Xenopus laevis tadpoles: how size constrains metamorphosis. Journal of Experimental Biology, 207(12), pp.2133-2145.
[10] Downie, J.R., Sams, K. and Walsh, P.T., 2009. The paradoxical frog Pseudis paradoxa: larval anatomical characteristics, including gonadal maturation. The Herpetological Journal, 19(1), pp.1-10.
[11] Beebee, T. & Griffiths, R. , 2000, Amphibians and Reptiles: A Natural History of the British Herpetofauna: Book 87 (Collins New Naturalist Library), Harper Collins, London
[12] McNeill, D.C. and Downie, J.R., 2017. Overwintering of smooth and palmate newt larvae in the Gartcosh Nature Reserve, Scotland. The Glasgow Naturalist, 26.
[13] Walker, G., Fairclough, B. and Paterson, E., 2019. Winter presence of adult male palmate newts (Lissotriton helveticus) in a pond in Scotland. Herpetological Bulletin, 149, pp.24-27.
[14] Allain, S.J. and Phillips, N., 2023. Observations of a neotenous population of Smooth NewtsLissotriton vulgaris from Norfolk. Trans. Norfolk Norwich Nat. Soc, 56(1).
[15] Leeke, C. 1990, An occurrence of neotenous sooth newts (Triturus vulgaris) in Cambridgeshire. Bulletin of the British Herpetological Society 31,