Amphibians

The midwife toad

October 1, 2024 by Admin

Written by Emma Byrne, Transforming Lives Trainee.

What is a midwife toad and how did it get its name?!

Midwife toads are native to Western Europe and arrived in Britain at the end of the nineteenth century. They are small and plump, about 5 cm (about half the length of the long edge of a credit card), with warty, mostly dull grey, but occasionally green or brown skin. The females sometimes have red spots on their flanks. They’re similar in appearance to common toads, except their snout is more pointed and the pupil of the eye has a vertical slit as opposed to the common toad’s horizontal split.

Midwife toads are nocturnal and have a very distinct call which sounds like a high-pitched beeping noise. This noise is very different from the croaking sounds produced by our native frogs and toads, and is exceptionally loud for a small toad, making it easy to track them down in the darkness.

So why the name midwife toad? This name stems from the toad’s breeding habits. The female expels a strand of eggs, which the male fertilizes externally. He then wraps them around his legs and carries the string of fertilised eggs on his back to protect them from predators in the water, hence the name “midwife”. The male will carry the eggs until they are ready to hatch, at which point they are deposited in shallow water.

So where can you find these delightful little toads? Midwife toads can be found throughout several different habitats from arable land, forests and wetlands. In the UK, they are mainly restricted to urban areas close to their initial release sites with populations across England and Wales including Bedfordshire, Yorkshire, Worksop and South Devon. That said, possible sightings have been made in other areas of the country, so ensure to listen out for that electronic beeping sound…there could be a midwife toad closer than you think!

To find out more about this species click here.

Remember to record your sightings of native and non-native amphibians and reptiles on our free Dragon Finder app.

Reference: Stidston, R. (2012) Midwife toadlet. Available at: https://www.uksafari.com/midwifetoads.htm

Toe tapping frogs: is it a lure?

October 1, 2024 by Admin

Written by Dr. Laurence Jarvis (external contributor)

Anurans (frogs and toads) are well known for their vocal abilities, particularly during the breeding season. However, visual cues are less studied and understood. Toe tapping is an unusual and interesting behaviour exhibited by a range of amphibian species. Also known as toe twitching, wiggling or trembling amphibians will typically raise or wave one or more legs or feet in the air. This may be slow or very fast. The behaviour appears to be performed by a range of amphibian species as a recent study found reports of toe tapping from 42 amphibian species from 12 families¹. There is currently no consensus on the exact reason for toe tapping that can be applied to all amphibian species. The behaviour often appears to occur in response to the presence of prey and may be linked to prey capture. It has also been noted to occur in relation to mate attraction and courtship, such as in the Southern Hispaniola Crested Toad (Peltophryne guentheri), as well as aggression. However, toe tapping may vary widely within a species with individuals sometimes performing the behaviour and not at other times². When the movements are slow with a raised limb, this is referred to as pedal luring and this is thought to attract prey through mimicking vibrations produced by the prey, as observed in the South American horned frogs (Ceratophrys spp.). However, Sloggett & Zeilstra (2008) proposed that instead, toe-tapping may cause additional vibrations that keeps the prey moving in order to allow detection by the frog³. In support of this hypothesis, a recent study of poison dart frogs (Dendrobatidae) found that individual frogs increased their toe tapping behaviour when prey were inactive which resulted in increased prey movements and more effective detection².

Figure 1. Dyeing poison frogs (Dendrobates tinctorius) may tap their toes to enable prey capture.

Dyeing poison frogs (Dendrobates tinctorius) of South America have often been observed to tap their posterior toes⁴. This tapping can be incredibly rapid with reports of up to 500 taps per minute, which is near the limit of vertebrate muscular vibration⁴. Adults of this species feed on a range of small and fast-moving prey such as flies and other arthropods so effective prey capture is essential. Research carried out by Parrish and Fischer (2024), found that frogs performed toe tapping more whilst feeding and when on a surface that would carry the vibrations, such as smooth leaves⁴. The frogs performed toe tapping much less when sitting on soil which transmit vibrations more slowly. The researchers also found that individuals increased their toe-tapping whilst in the presence of a breeding partner. The reasons for this are unclear but shows that this species may adapt its tapping behaviour depending on the presence of other individuals, particularly breeding partners. Overall, this study supports the work of Sloggett and Zeilstra (2008) and suggests that toe tapping may agitate small arthropods by substrate vibrations and thereby help the individuals to detect their prey⁴.

Figure 2. The Yellow-striped Poison Frog (D. truncates) exhibits accelerated toe tapping.

The Yellow-striped Poison Frog (D. truncatus) is a poison dart frog native to Colombia. In an attempt to further understand the function of toe tapping in this species Vergara-Herrera et al. (2023) designed an experiment to examine the vibrations produced during toe tapping⁵. The results confirmed that toe tapping was performed in relation to prey capture. In addition, the researchers found that tapping rate accelerated during their sequence of attacks on prey during foraging⁵. This is analogous to the foraging behaviour of species including bats, dolphins and sperm whales, all of which increase call rate as they approach their prey. In these species it is thought that the increase in call rate immediately prior to capturing their prey helps to confirm its location, speed and movement and thus aid in capture. It is not known whether this is the reason for increasing tapping rate in the Yellow-striped Poison Frog but the acceleration is likely to aid in final prey capture. If the toe tapping serves to further agitate the prey, as proposed by Sloggett & Zeilstra (2008), then more rapid toe tapping would make the prey more detectable, and thus easier to capture by the frogs.

Figure 3. The Southern Corroboree Frog (Pseudophryne corroboree) is a critically endangered species native to Australia.

Toe tapping is an under recorded behaviour but is being noted in an increasing number of species worldwide. The genus Pseudophryne consists of 14 endemic Australian species, all of which are small, cryptic ground-dwelling species. Toe tapping has only previously been recorded in one other species within the genus⁶. The Southern Corroboree Frog (Pseudophryne corroboree) is a critically endangered species, restricted to areas above 1300 m elevation in New South Wales, Australia. Recently it was not thought to exhibit toe tapping behaviour. However, during captive breeding, McFadden et al. (2008) observed rapid toe tapping prior to being fed crickets⁶. In this species, for the vast majority of individuals, the tapping foot was raised off the substrate and waved as in the South American horned frogs. This is in contrast to poison frogs, which usually tap their feet whilst in contact with the substrate. The behaviour of the Southern Corroboree Frog would suggest that the moving foot is used to attract prey, rather than trigger movement. Alternatively, as stated by the researchers of the study, it is possible that the tapping could be simply an excited response to the presence of prey.

Overall, toe tapping is an interesting behaviour which has been observed in a wide range of amphibian species. Increased observations and studies on a wider range of species are demonstrating that the behaviour is more widespread than previously thought. Although the exact functional significance is not always fully understood, and may vary between species, it demonstrates the capacity for varied visual cues to be utilised by frog and toad species.

References

¹Erdmann J.A. (2017). The function of toe movement in feeding by the gulf coast toad (Incilius nebulifer). Masters thesis, Southeastern Louisiana University.

²Claessens L.S.A., Ganchev N.O., Kukk M.M., Schutte C.J., and Sloggett J.J. (2020). An investigation of toe-tapping behaviour in anurans by analysis of online video resources. Journal of Zoology, 312 (3): 158–162. https://doi.org/10.1111/jzo.12815.

³Sloggett J.J. and Zeilstra I. (2008). Waving or tapping? Vibrational stimuli and the general function of toe twitching in frogs and toads (Amphibia: Anura). Animal Behaviour, 5: e1–e4.

⁴Parrish T.Q. and Fischer E.K. (2024). Tap dancing frogs: Posterior toe tapping and feeding in Dendrobates tinctorius. Ethology, p.e13465.

⁵Vergara-Herrera N., Cocroft R. and Rueda-Solano L.A. (2023). Eating to the beat of the drum: vibrational parameters of toe tapping behavior in Dendrobates truncatus (Anura: Dendrobatidae). Evolutionary Ecology, 1-17. https://doi.org/10.1007/s10682-023-10277-x

⁶McFadden M., Harlow P.S, Kozlowski S. and Purcell D. (2010). Toe-twitching during feeding in the Australian myobatrachid frog, Pseudophryne corroboree. Herpetological Review, 41(2): 153-154.

Natterjack Toads (Epidalea calamita)

October 1, 2024 by Admin

Written by Eve Goddard, Transforming Lives Trainee.

Natterjack toads are the lesser known of the two native UK toad species.

Smaller than the common toad, natterjacks are up to 7cm in length and have shorter legs, which they use to run in short bursts. Unlike the common toad’s bronze iris, natterjacks’ are bright green. Their most distinguishing feature is the yellowy stripe which runs down the centre of their back.

Their common name is said to come from their distinguished rasping call which can be heard up to two km away. Males take advantage of this in spring, the louder their call, the more chance they have of attracting females.

You can hear their call by clicking this link (© Slitere National Park)

Habitats

Natterjacks live in saltmarsh, heathland and coastal areas. They use warm freshwater ponds for breeding. One example being ponds that form in sand dunes. Their spawn is laid in singular rows, unlike the common toad’s double rows. In preferable conditions their spawn can mature very quickly – in as little as six weeks, which creates an evolutionary advantage for avoiding predators, and leaving a pond that may be both porous due the sandy substrate and/or seasonal.

For hibernation in the winter, their shorter strong limbs come into play. They dig burrows in sand or light sandy soils. Natterjacks will also use the same technique in the summer to protect themselves from particularly hot weather.

Conservation

As one of the UK’s rarest amphibians, natterjack toads are a protected species by law, it is an offence to kill, injure, capture or disturb them; damage or destroy their habitat; or possess them or sell or trade them in any way. This also applies to larval stages and eggs.

Although their populations are few and far between, owing largely to habitat loss, there are some simple steps we can all take to protecting their habitats. When visiting saltmarsh, heathland or coastal areas taking litter home with you, keeping to designated footpaths, and keeping dogs on leads and out of ponds all helps.

Remember, if you spot a natterjack toad or any of our reptiles or amphibians – the Dragonfinder App will allow you record your findings and help us in our conservation efforts.

On The Brink – Britain’s most vulnerable Amphibians and Reptiles

September 1, 2024 by Admin

Written by Charles Bonnett, Transforming Lives Trainee.

Many species across this country – and the wider world – are experiencing population declines. Reptiles and amphibians are no different, as 4 out of Britain’s 13 reptiles and amphibians are considered under threat of extinction. In this vein, let’s take a brief look at our rarest amphibian and reptile.

Northern pool frog

Pool frogs are our rarest amphibians; not only that, but they are also the most vulnerable out of our 13 reptiles and amphibians. They were presumed extinct in 1995 but have since been reintroduced in East Anglia from pool frog populations in Sweden. Similarly to common frogs, male pool frogs are around 6cm in length, with the larger female reaching up to 9cm. They are generally brown or green in colour, with a cream or yellow dorsal stripe, and have a pair of ridges along their back. A distinct feature of the pool frog is their vocal sacs found on the sides of a male’s mouth, which can produce a loud call during breeding season.

Rare ponds named ‘pingo’s’ (the result of glacial activity during the last ice age) are their favoured habitat for breeding, and therefore the succession and destruction of these landscape features has contributed to the decline of the pool frog.

Smooth snake

Smooth snakes are our rarest reptile. Not only are they uncommon, but they are incredibly secretive animals, rarely basking in the open. Their name is derived from their scales, which are smooth in comparison to the keeled scales of their counterparts, the grass snake and adder. Adults reach about 60-70cm in length, with females often being the larger sex. They possess quite an understated colouring, consisting of grey and brown, with a distinctive eye stripe extending from the eyes across the side of the head.

As rare as the smooth snake themselves, is their favoured habitat. They are restricted to heathland primarily in Dorset and Hampshire. They prefer mature heathland vegetation, which can provide suitable cover and a supply of food. Unfortunately, heathland habitat suffers from degradation, due primarily to development, farming, human activity, and natural succession. All these factors impede upon the already diminished smooth snake’s habitat.

Despite the difficulties our amphibians and reptiles are facing, there are many ongoing amazing projects and initiatives with the intent to aid the survival of these animals. As time progresses, we will surely need to stay vigilant regarding the health of reptiles and amphibians and their habitats.

Every little helps, so if you spot any amphibians and reptiles whilst out and about, consider recording them on our free Dragon Finder app.

What our animals are doing this month

September 1, 2024 by Admin

Written by Paul Arestides, Transforming Lives Trainee

Natterjack Toad

The natterjack toad (Epidalea calamita) is very rare and smaller in size compared to our common toad. They are more olive green in colour, with a very distinguishing yellow stripe running along their backs. These toads are mainly nocturnal, so are best seen in the evenings as the sun is setting. It is also a pioneer species, meaning it is one of the first to set up a home in newly formed habitats like young sand dunes. They bury themselves in the warm, loose sand around pools during the day.

Did you know?

The natterjack toad is also known as the ‘running toad’ because they tend to run rather than walk or hop.

Their average lifespan is 10-15 years

Their length can be up to 8cm

Ecology

In springtime you’ll see gathering males in full chorus singing together attempting to attract a female. These calls can be heard up to a mile away! The spawning season is between April and June. Males find a mate and spawn in warm shallow ponds, pools or puddles in dune slacks and sandy heaths. Females lay thousands of eggs in single rows (unlike our common toad that lay them in double rows) along two spawn strings. It only takes six to eight weeks for the spawn to develop in to toadlets with the yellow dorsal stripe clearly visible.

Females lay thousands of eggs in single rows. Image Credit: Matt Wilson

Mainly found in coastal sites across the northwest of England and the Solway Firth in Scotland, they cling on in just a few other places in the sand dunes of East Anglia and heathlands of Surrey and Hampshire.

At this time of year, adults and metamorphosed toadlets spend time building up plenty their reserves in preparation for the winter months ahead. Through winter they will take shelter burying themselves in the mud or sand, under logs and rocks.

Threatened by habitat loss, the natterjack toad has declined massively over the last few decades. As a result of this, it is strictly protected by British and European law which makes it an offence to kill, injure, capture or disturb them; damage or destroy their habitat; or possess them or sell or trade them in any way. This also applies to larval stages and eggs.

Remember, if you spot a natterjack toad or any other amphibians and reptiles (including young and eggs), log your sighting on our free Dragon Finder app.

Croaking Science- Horned frogs: specialised predators

September 1, 2024 by Admin

Written by Dr. Laurence Jarvis (external contributor)

Horned frogs within the genus Ceratophrys are highly specialised frogs with particularly interesting ecology and behaviour. The eight recognised species are endemic to South America and inhabit grassland and rainforest habitats.

Their appearance is somewhat unusual with extremely wide heads and a relatively large gape. This allows adults to feed on a large range of prey including insects, small mammals and in many cases other frog species¹. They are sit-and-wait predators spending many hours motionless, often concealed under leaf litter waiting for prey to move past.

For the majority of the year the adults burrow underground, often concealed in dry soil, unlike that of many other hibernating or aestivating amphibians which burrow into damp habitats². During this period adult horned frogs develop a cocoon of dead skin around themselves to prevent desiccation. After the first seasonal rains, the adults emerge and breed with a highly explosive breeding strategy laying several thousand eggs in temporary water bodies. Unusually, the tadpoles are voracious carnivores, feeding on a range of other invertebrates, even members of its own species. This enables them to grow and metamorphose within a few short weeks before the water bodies dry.

Figure 1. Horned frogs, such as the Suriname Horned Frog (C. cornuta), have an unusual appearance with a large gape and head.

Horned frogs have evolved a range of unique adaptations to enable them to catch fast moving and difficult to seize prey. Research by Lappin et al. (2017)³ showed that the bite force of Cranwell’s Horned Frog (C. cranwelli) can reach 500 N which is exceptional and rivals that of many medium-sized reptiles or mammals³. This enables them to subdue many species of frogs, lizards, snakes, birds and rodents. In addition, the teeth of horned frogs are sharp, pointed and curved and resemble those of predatory reptiles³. They also have a pair of long fangs enabling them to catch their prey.

Figure 2. The unusual teeth of horned frogs with sharp tips and curved fangs.

In addition to strong jaws, horned frogs possess highly sticky tongues which allows them to latch onto rough substrates such as mammal fur and bird feathers. These allow the tongues of horned frogs to have extremely high adhesive forces which are beyond their own body weight and also outweigh any potential prey item⁴.

It appears that the high adhesive properties are due to a combination of adaptations. First, their tongues are covered in mucus, which enhances adhesion. However, this alone is not enough to explain the high adhesive properties. It appears that the mucus spreads across the surface of the tongue as contact is made with the prey which results in stronger adhesion⁴. Second, a high contact pressure, due to the fast movement of the tongue, allows an additional adhesive property. This is quite unlike the method of attachment of many reptiles such as geckos, which rely on small hair-like projections to adhere to the substrate’s surface⁴.

Furthermore, two species of horned frogs have also been observed carrying out complex pedal luring behaviour to capture their prey⁵. This involves the adult sitting partly concealed in the leaf litter and waving its back legs to attract moving insect or vertebrate prey.

Figure 3. Bell’s Horned Frog (C. ornata) burrow into soil to wait for passing prey.

In 2011 a novel discovery on the tadpoles of Bell’s Horned Frog (C. ornata) in Brazil was made by Natale et al. (2011)⁶. The researchers provide the first evidence for sound production by anuran larvae. Prior to 2011, sound production by anuran larvae was totally unknown⁶. It appears that the larvae of Bell’s Horned Frog produce underwater sounds only with physical contact with others of the same species. The reason for this is unclear but it may be that sound production reduces the chances of larval cannibalism in aggressive, rapidly developing predators.

Although four of the eight species of horned frog are relatively common across South America, two species are declining and threatened due to a combination of habitat loss, urbanisation and illegal collecting from the wild.

In addition, two species are Data Deficient with very little known of their ecology and distribution. Field-based research studies are beginning to reveal important aspects of their ecology¹ but more information is required to enable effective conservation measures to be implemented. Horned frogs are a group of fascinating species and it would be a great loss to see them decline further throughout their range.

References:

¹da Silva Jorge J., Sales R.F.D., de Carvalho Kokubum M.N. and Freire E.M.X. (2015). On the natural history of the Caatinga horned frog, Ceratophrys joazeirensis (Anura: Ceratophryidae), a poorly known species of northeastern Brazil. Phyllomedusa, 14 (2): 147-156.

² Faivovich J.L., Nicoli B.L., Blotto M.O., Pereyra D., Baldo J.S., Barrionuevo, M., Fabrezi, E.R. and Haddad, C.V.B. (2014). Big, bad, and beautiful: phylogenetic relationships of the Horned Frogs (Anura: Ceratophryidae). South American Journal of Herpetology, 9: 207–227.

³ Lappin A.K., Wilcox S.C., Moriarty D.J., Stoeppler S.A., Evans S.E. and Jones M.E. (2017). Bite force in the horned frog (Ceratophrys cranwelli) with implications for extinct giant frogs. Nature Scientific Reports, 7 (1): 11963.

⁴ Kleinteich T. and Gorb S.N. (2014). Tongue adhesion in the horned frog Ceratophrys sp. Nature Scientific Reports, 4 (1): 5225.

⁵ Radcliffe C.W., Chiszar D., Estep K., Murphy J.B. and Smith H.M. (1986). Observations on pedal luring and pedal movements in leptodactylid frogs. Journal of Herpetology, 20 (3): 300-306.

⁶ Natale G.S., Alcalde L., Herrera R., Cajade R., Schaefer E.F., Marangoni F. and Trudeau V.L. (2011). Underwater acoustic communication in the macrophagic carnivorous larvae of Ceratophrys ornata (Anura: Ceratophryidae). Acta Zoologica, 92 (1): 46-53.

Amphibians

Habitats

Conservation

Natterjack Toad

Did you know?

Ecology

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