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What our animals are doing this month…

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As we approach the end of summer our newt larvae will absorb their gills and depending on their development, will start to leave the water as ‘newtlets’ or efts in August. Great crested newt larvae are the biggest of our newt species, reaching lengths of 50-90cm before metamorphosis.

Great Crested newt larvae, palmate newt larvae and smooth newt larvae develop better in warmer waters as metamorphosis can happen faster. Indeed, cooler conditions and shaded ponds mean that larvae develop slower. In terms of what larvae eat when they are developing, they eat amphibian larvae and a variety of aquatic invertebrates, yum!

However, some newts will decide to overwinter as larvae and develop in the following year. Adult newts can still be seen in and around ponds searching for, and hunting for food in August.

From September onwards, our newts will be seeking shelter and somewhere to overwinter during the autumn and winter months.

 

If you have spotted any newt larvae or newtlets, make sure to record them on our Dragon Finder App!

Spreading Frogtopia: Matt Turpin

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Froglife follower and pond-enthusiast, Matt Turpin has been busy building and restoring his neighbours ponds in Nottingham whilst he has been on furlough. Learn more about why he was inspired to do so by his article below!

I was furloughed from my job with an educational charity in June. While I was happy to devote most of the free time I now had to looking after my three year old son, I felt a real need to do something, anything to make the world a better place. It didn’t take long to figure out what that was.

When I moved into a new house a year ago, one of the first things I did – before I’d unfinished unpacking everything – was to get into the back garden and dig a wildlife pond. I’ve been digging ponds since childhood, when my gran I would have varying degrees of success creating frog-friendly habitats for her garden. I would sit by the completed pond for hours once it was finished, taking a sense of peace and serenity from being near water that I still find. Sitting by water, and seeing life beneath the surface – the amphibians, the invertebrates, the tiny, barely-visible tiny creatures – and above the surface – the visiting dragonflies, bees, hoverflies and, if lucky to be out at dusk, bats – was, and has remained one of my favourite ways to relax.

Put water in a garden, and life will proliferate: it’s that simple. I had seen the benefits in my own garden; why not spread that elsewhere? After all, the weather was nice, the gyms were closed and a promising summer lay ahead. It was time to grab some tools, visit some gardens and break some ground. I put out a call over the internet that I would only charge for materials and minor expenses – enough to cover what I lost through furlough, at most – and the offers began to arrive into my inbox.

Some people wanted a pond from scratch, and we’d carefully work out the best place: away from trees and their subterranean roots; plenty of sunlight; near foliage to shade and hide creatures. Often, gardens are full of what seems like rubbish: old rocks, slabs, roof tiles, bricks, remnants from long-completed garden projects. I’d incorporate these into the design, creating caves, banks and other features that would provide the best possible habitat for a range of species. Every pond would have a ‘beach’ – a gently sloping area of shingle that would allow easy entry and exit from the pond -as well as providing a handy area for garden mammals to drink from.

Other clients would want an old  long neglected pond rescuing and transformed into a nature pond. The reeds, sedges and grasses that had run riot in these places would be cut back, replanted and passed onto the new ponds to give them a vegetative kick. I’d spend days thigh- deep in mud, turning an ugly, sterile area into a thriving wildlife sanctuary. It was hugely satisfying, even if my knees were never truly clean during the whole Summer.

After finishing each job, i’d ask the client to keep in touch: partly because I could monitor any issues that arose, partly because I could therefore share any foliage or tips with a growing network of local wildlife pond owners, but mainly because I wanted to find out what happened to the garden once I’d gone.

“Went out this afternoon: never seen so many birds visit, all drinking from the pond. Then this evening three frogs!” said one client, who I’d built a large, rockery lined pond for. “How could we already have newts??” queried another. A swell of pride accompanied these messages: in some tiny way I’d given wildlife a hand, and sported a decent tan too.

Yet the greatest seal of approval came recently, with a pond rescue. After turning a drained and leaf-bound old pond back into a haven for life, I revisited to see how it was a week after the build. 

As I sat by the pond, assessing water levels, seeing if the water buttercups I’d potted and positioned would be better elsewhere, I felt that curious feeling you get when you are being looked at. I glanced to my side, and there, sitting on a rock overhanging the water, was an adult frog, surveying her domain. She seemed oblivious to me, rather she seemed to be joining me in appreciation. We both sat there for a good ten minutes, before I decided I better head off to my next job,  and she decided to go check out a little more of her new home. It felt remarkably satisfying. Next spring, once the ground softens and warms, I’ll be out there again, creating frogtopias across my town.

If you feel inspired to make your own wildlife pond, feel free to download our FREE Just Add Water guide.

Croaking Science: Newts that never grow up!

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Newts that never grow up – paedomorphosis in salamanders

The majority of pond-breeding salamanders have a biphasic metamorphic life cycle where free-swimming larvae living in ponds and other water bodies metamorphose into terrestrial living adults. The advantage of this life history is that it allows adults to exploit different habitats to larvae, utilise a wider range of ecological niches and escape from potentially hostile environments e.g. a desiccating pond. However, a number of salamander species within Europe and North America have evolved a unique life history where free-swimming larvae to do not metamorphose into terrestrial living adults, but remain within the water and retain larval characteristics. Known as paedomorphosis these individuals develop into sexually reproductive adults but retain larval traits e.g. free-swimming larval form (Figure 1). It appears that the phenomenon of paedomorphosis has evolved several times within salamanders and has been of great interest to biologists for centuries. One theory suggests that paedomorphosis is most likely to evolve when environmental conditions experienced by adults are inhospitable relative to conditions experienced by larvae. For example, if water bodies remain constant throughout the year but temperature regimes and environmental factors on the land are hostile, such as in mountainous regions, arid landscapes or nutrient poor regions, it may be more favourable to remain in the larval form. Within southern Europe, paedomorphic populations often occur in deep, permanent and cool alpine lakes, where the terrestrial habitat has poor nutrient availability (Denoël et al., 2005). In an attempt to resolve many questions relating to the evolution of paedomorphosis in salamanders Bonnett et al. (2014) examined DNA sequences of a sub-family of plethodontid salamanders from North America. The authors concluded that within this group, paedomorphosis is more likely to occur in species dwelling in caves and those occurring in more arid climates. Here there are more resources in water bodies than in terrestrial habitats. An interesting finding of this study is that paedomorphosis has evolved and re-evolved serval times in the same species. The Valdina Farms Salamander (Eurycea troglodytes), from the western Edward Plateau, Texas, existed in a paedomorphic form 22 million years ago, before evolving into a metamorphic form (i.e. larvae metamorphosed into terrestrial adults). Subsequently, several million years later, it re-evolved back into a paedomorphic form (Bonnett et al., 2014). This is likely to be due to changing environmental conditions over this time period. However, there is a cost to being paedomorphic. Bonnett et al. (2014) found that paedomorphic spelerpine plethodontids from eastern North America have significantly smaller geographic range sizes than metamorphosing species and have not dispersed between biogeographic regions.  This has resulted in these species being more at risk from environmental events or human disturbance than species with wider geographic ranges and as a result have a higher rate of extinction.

Figure 1: Cave salamanders such as the Mexican axolotl (Ambystoma mexicanum) exist in paedomorphic forms due to hostile terrestrial habitats. Note the retention of gills which is normally a characteristic of larvae.

In some populations of salamanders, individuals exhibit facultative paedomorphosis, i.e. when both metamorphic and paedomorphic forms coexist and the occurrence of the latter within a given population depends on the advantages of living in the aquatic and terrestrial habitats. Whether an individual is metamorphic or paedomorphic may depend on a range of environmental factors including temperature, pond desiccation rate, terrestrial aridity and resource availability. Facultative paedomorphosis is an adaptive strategy which has been reported from several European newts. For example, great crested newt (Triturus cristatus), palmate newt (Lissotriton helveticus), alpine newt (Ichthyosaura alpestris) and southern banded newt (Omatotriton vittatus) all exhibit paedomorphosis, especially in the south of their range (Oromi et al., 2014). Facultative paedomorphosis has been regularly observed in populations of the smooth newt (L. vulgaris), particularly those in southern and eastern Europe (Figure 2). In this species, the key environmental factors are prey and predator abundance and habitat composition, with paedomorphosis generally occurring in areas with permanent, nutrient-rich water bodies without predators (Bozkurt et al., 2015). When fish are introduced to water bodies, paedomorphosis generally disappears since the aquatic environment becomes a less favourable habitat (Denoël et al., 2005).

Figure 2: Facultative paedomorphosis in the smooth newt (Lissotriton vulgaris) is most common in southern parts of its range. However, it can occur anywhere, such as in this individual from eastern England. Photo © Liz Morrison.

In 2017, Mathiron et al. (2017) tested theories in relation to how climatic factors impact on paedomorphosis in facultative populations of the palmate newt (L. helveticus) living in the Department of Hérault, France. The authors found that temperature and water availability each play a significant role in metamorphosis and explain the persistence of paedomorphosis in certain populations. These results have major implications as they show that droughts through evolutionary history have been a primary factor in promoting the evolution of paedomorphosis in this species. When terrestrial environments experience persistent drought, this has promoted the evolution of paedomorphic populations. This has significance in relation to a warming climate where the occurrence of severe droughts in Mediterranean parts of this species’ range, may result in an increase in paedomorphic populations in the near future. Mathiron et al. (2017) also found a sex-biased effect highlighting the role of sex in the metamorphosis of paedomorphs. Both water level and temperature affected the metamorphosis of males more than females. More metamorphic males occurred than females and, in drying conditions, started metamorphosis earlier than did females, which resulted in a female biased sex-ratio of paedomorphs. The reason why males metamorphose more than do females may be due to differences in levels of hormones in males compared to females. Also, males tend to disperse more than females so being metamorphic and turning into terrestrial adults would allow them to seek new water bodies and promote gene flow between populations.

 

References

Bonnett, R.M., Steffen, M.A., Lambert, S.M., Wiens, J.J. & Chippindale, P.T. (2014) Evolution of paedomorphosis in plethodontid salamanders: ecological correlates and re-evolution of metamorphosis. Evolution 68 (2): 466–482.

Bozkurt, E., Olgun, K. & Wielstra, B. (2015) First record of facultative paedomorphism in the Kosswig’s newt Lissotriton (vulgaris) kosswigi (Freytag, 1955) (Urodela; Salamandridae), endemic to northwestern Turkey. Turkish Journal of Zoology, 39: 976-980.

Denoël, M., Joly, P. & Whiteman, H.H. (2005) Evolutionary ecology of facultative paedomorphosis in newts and salamanders. Biological Reviews, 80: 663–671.

Mathiron, A.G.E., Lena, J., Baouch, S. & Denoël, M. (2017) The ‘male escape hypothesis’: sex-biased metamorphosis in response to climatic drivers in a facultatively paedomorphic amphibian. Proceedings of the Royal Society B: Biological Sciences, 284 (1853):

DOI: 10.1098/rspb.2017.0176.

Oromi, N., Amat, F., Sanuy, D. & Carranza, S. (2014) Life history trait differences between a lake and a stream-dwelling population of the Pyrenean brook newt (Calotriton asper). Amphibia-Reptilia, DOI:10.1163/15685381-00002921.

Croaking Science: Courtship & Reproductive Behaviour in Newts and Salamanders

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Courtship and reproductive behaviour in newts and salamanders

Courtship behaviour in newts and salamanders is very different to that of frogs and toads (anurans). In anurans, fertilisation is external so the male expels his sperm whilst the female lays her eggs. However, in newts and salamanders, fertilisation is internal. The male deposits a sperm package, the spermatophore, and the female uptakes this into her reproductive tract to fertilize her eggs. Male newts and salamanders have evolved a range of complex behaviours to encourage the female to uptake the spermatophore. This may involve contact between the male and female, but in aquatic newts of the family Salamandridae, there is no contact and the male encourages the female through complex courtship displays.

male showing belly Matt Wilson spring11
Great Crested Newt ©Matt Wilson

Newts in the genera Triturus (e.g. great crested newt) and Lissotriton (e.g. smooth newt), have similar courtship displays. During an initial orientation phase, the male will move in front of a female and attempt to gain her attention. The female may show no interest and swim away. If successful, the male moves into a static display which involves intense tail fanning and wafting pheromones towards the female. Once the female is fully engaged the male will start to retreat backwards facing the female, still tail fanning. He will then turn around, creeping away from the female with his tail quivering and her following. The male will pause, deposit his spermatophore onto the substrate, walk one body length forward and stop, turning 90 degrees. This allows the female to move so that her cloaca is directly over the spermatophore. She now uptakes the spermatophore for successful fertilisation. Unfortunately, spermatophore uptake by the female will not always be successful so the male has to perform the courtship display from the beginning.

Although males will develop secondary sexual characters during the spring (e.g. tail crest, webbing on the feet), the courtship display takes place in underwater in darkness, so visual cues are likely to be irrelevant. Recent research has shown that the courtship pheromones produced by the male are crucial in ensuring mating success. When a male employs tail fanning, he sends sex-specific pheromones towards the female and these directly impact her responses. In the laboratory, female palmate newts (Lissotriton helveticus) exhibit all the sexual responses up until spermatophore uptake, when in the presence of male pheromones, but no male present. This demonstrates the importance of pheromone production and effective transfer to the female during mating. Previous research has demonstrated that male newts which perform their displays more energetically, have higher mating success. In addition, in male smooth newts (L. vulgaris), males with higher body mass and crest height achieve higher mating success, possibly due to enhanced pheromone production and more effective transfer to the female. This research demonstrates the importance of effective transfer of pheromones by the male towards the female for reproduction.

Smooth newt ©Mike Toms

Male pheromones may have additional effects on females. In the aquatic Spanish ribbed newt (Pleurodeles waltlm), which has both contact and non-contact displays, the male has special glands in the cloaca. When these are released they induce the female’s cloaca to expand and uptake the spermatophore. It has previously been thought that the female doesn’t have a choice over whether she receives the spermatophore from a particular male, once he has clasped her and released his pheromones. However, recent research has demonstrated that females of this species may exhibit thanatosis (feigning death) during courtship prior to the crucial moment of pheromone production by the male. This avoids spermatophore uptake by the female and therefore may provide an escape strategy by a female, should she not want to be persuaded by the male to mate. Thanatosis has previously only been known as an escape strategy by amphibians and has not been observed in a sexual context.

Male newts and salamanders exhibit a range of complex sexual displays. Although many of the behaviours exhibited are widely understood, there are still areas where we have less understanding, such as the effects of pheromones, importance of secondary sexual characters and female choice in mate selection.

 

References

Halliday, T. R. (1974) Sexual behaviour of the smooth newt, Triturus vulgaris (Urodela, Salamandridae). Journal of Herpetology, 8 (4): 277-292.

Green, A. J. (1991) Large male crests – an honest indicator of condition, are preferred by smooth newts, Triturus vulgaris (Salamandridae) at the spermatophore transfer stage. Animal Behaviour, 41 (2): 367-369.

Janssenswillen, S. & Bossuyt, F. (2016) Male courtship pheromones induce cloacal gaping in female newts (Salamandridae). Plos One: DOI:10.1371/journal.pone.0144985.

Teyssedre, C. & Halliday, T. (1986) Cumulative effects of male’s displays in the sexual behaviour of the smooth newt, Triturus vulgaris vulgaris (Urodela, Salamandridae). Ethology, 71: 89-102.

Treer, D., Bocxlaer, I.V., Matthijs, S., Four, D. D., Janssenswillen, S., Willaert, B. & Bossuyt, F. (2013) Love is blind: indiscriminate female mating responses to male courtship pheromones in newts (Salamandridae). Plos One, 8 (2): e56538.

Last chance: Share your frog thoughts & enter our prize draw

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Froglife’s national survey about perceptions of amphibians and reptiles is coming to an end on the 14th of March.  We are asking people what they think about snakes, newts, frogs, lizards and toads as part of a project supported by the Heritage Lottery Fund to investigate how the animals are viewed.  We would love to know your thoughts about wildlife and charity, and you can find the online survey here.

Questions include your favourite animals and thoughts about wildlife conservation, your opinions on amphibians and reptiles, a bit of an ID quiz as well as about the charitable causes closest to your heart.

We’re not looking for right or wrong answers; we’re really interested in honest responses to help us get a better understanding of the challenges we face when talking about our work.  You can find out more about the aims of The Scale of the Problem project here.

Through taking part, you can also enter a prize draw to win over £50 worth of goodies from the Froglife online shop, with a prize for over 18s and under 18s who take part.

Under 18s prize
The prize for under 18s includes a cuddly frog, pond dipping kit and frog back pack from the online shop

The results so far have been really interesting, with Hedgehogs the most popular answer to the favourite animal question. 95% of the respondents so far have seen a frog in the wild in the UK, compared to 64% having seen a snake.  We are also hearing, perhaps unsurprisingly, that many people are affected by  financial concerns when choosing to support charities, and have cut back donations.  All of the information we gather through the survey will be analysed by marketing experts Emerald Frog to help us strengthen our fundraising and campaigning techniques, enabling us to better support amphibians and reptiles into the future.

It would be wonderful if you could take the time to share your thoughts and experiences before the 14th of March, to help shape the future of Froglife’s communications and campaigns. Thank you!

You can read more about the Scale of the Problem project here