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Croaking Science: 2023 so far- what have we learned from the Dragon Finder App?

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As we fast approach the spring and our amphibians and reptiles begin to stir after their winter period of relative dormancy (known as brumation) we can expect sightings to increase in frequency. Whilst the occasional pioneering common lizard (Zootoca vivipara) or adder (Vipera berus) will emerge from their hibernacula to bask in winter sun, it’s the UK’s amphibians that bring the most herptile activity to this time of the year. This is reflected in the sightings that have been reported to Froglife’s Dragon Finder App so far in 2023.

At the time of writing (mid-February 2023), we’ve verified 42 reports submitted to the App; 24 sightings of common frogs (Rana temporaria), 6 encounters with common toads (Bufo bufo), 8 palmate newt sightings (Lissotriton helveticus), 2 smooth newt (Lissotriton vulgaris) sightings and 1 sighting of a great-crested newt (Triturus cristatus) and an alpine newt (Ichthyosaura alpestris) respectively.

All this amphibian action heralds the commencement of their breeding season. Common frogs lead the charge; the earliest report of frogspawn this year came to us from the Isles of Scilly, 45km south-west of mainland Cornwall, reported to us on the 9th January yet seen on Christmas Eve! UK common frogs spawn earliest here due to the archipelago’s unique climate – the moderating oceanic influence on which means that winters are warmer there than anywhere else in the UK and consequently snow and frost (potentially detrimental to spawn) are rare. We’ve received a total of 11 frogspawn reports so far in 2023, with the majority of these coming from Devon & Cornwall, reflecting the relatively warm winters experienced by the southwest more broadly. We’re now looking forward to witnessing reports of frogspawn slowly popping up in increasingly northerly and easterly locations as we pass through February and into March and April.

We’ve received 6 reports of common toads, but only one of common toad spawn, reported from Devon. Interestingly, the Dragon Finder App user that made this sighting was also able to spot a number of instances of a frog and toad engaged with one-another in ‘amplexus’, the act of the male using rough nuptial or ‘thumb’ pads to clasp onto the female whilst she deposits spawn. Common toads often begin to migrate to their ancestral breeding ponds from February, waiting for a comparatively warm and wet evening to do so.

Therefore, be sure to keep a keen eye out for reptiles and amphibians as the winter draws to a close and make sure to report your sightings through our free Dragon Finder App – the data we receive provides a wonderful insight into what our species are up to, as well as when and where this activity is occurring. Happy spotting!

#StopSpawnSales- What you can do to help

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Froglife are running our #StopSpawnSales social media campaign during March to tackle the illegal practice of selling wild-caught amphibian spawn online. 

As most of us are aware, we are now in the peak of amphibian breeding season as our species are laying their eggs in ponds and pools across the country. This time of year also sees an unfortunate sharp rise in sales of wild-caught amphibian spawn (and even tadpoles) on online selling sites. 

We aren’t party poopers! We know how fascinating it can be to take spawn home, watch it grow and release the tadpoles/froglets back into the wild, but we want people to do this legally and safely! Not only is there a massive risk of spreading amphibian disease and viruses, invasive plants and invertebrates, but the sale of wild-caught spawn or tadpoles is an offence under The Wildlife and Countryside Act 1981. 

What you can do to #StopSpawnSales:

  • Never buy wild-caught spawn/tadpoles online! If you decide to raise frogspawn, it is crucial that all tadpoles/froglets/toadlets are released to the ponds where they were found to prevent spreading disease and invasive species
  • If you see wild-caught spawn/tadpoles for sale on social media or online marketplaces, please report it to the marketplace itself in the first instance
  • If further action is needed (i.e the posts aren’t taken down), please report it to your local Police Wildlife Crime Officer (with screen shots of the advert if possible)
  • Spread the word! like and share our social media posts and encourage those around you to #StopSpawnSales 
Photo Credit: David Palmer

 

What our animals are doing this month….

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What are our animals up to in February?

As we ‘hop’ into February common frogs are out and about spawning. Well, this winter they have already started, as the first sighting of Frogspawn was on 23rd December in the Isles of Scilly! Mainland Britain is hot on its heels with milder spells in January creating a great opportunity for spawning.

The deep croaking is a dead giveaway of male frogs trying to attract mates. The males clasp the females in a bear hug waiting for her to spawn so he can fertilise the eggs. The result being large jelly like clumps of spawn that as they mature start to float. This is where the danger sets in as if the weather changes and the pond ices over the spawn on the top may not survive, however, spawn that is submerged has a much better chance of survival.

You can help by submitting your sightings of frogspawn and any other amphibians and reptiles to our Dragon Finder App – these records help us learn more about how our changing environment affects our species.

What our animals are doing this month…

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Late spring or early summer is a good time to be on the lookout for tadpoles! You might spot common frog or common toad tadpoles or, if you are lucky and on the coast, you might even spot natterjack toad tadpoles!

You might have spotted a few tadpoles already as frogs can lay their frogspawn as early as January and it can take two to four weeks for tadpoles to hatch out. As the tadpoles grow, they become faintly speckled with gold/brown and will slowly grow back and front legs!

Common toads breed a little later than common frogs, laying double strings of spawn and wrapping it carefully around vegetation. Again, it will take two to four weeks for the tadpoles to hatch out. To tell the difference between frog and toad tadpoles, you simply have to look at their colour. Toad tadpoles remain jet black and can also form shoals so can be easier to spot.

Common frog tadpoles
Common toad spawn
Natterjack toad spawn. Credit: Matt Wilson

https://www.froglife.org/2022/05/10/what-our-animals-are-doing-this-month/(opens in a new tab)

The natterjack toad is confined to just a handful of sites on the coast in the UK and is only found on the Solway Coast in Scotland. Breeding for natterjack toads takes place in March/April but can continue into the early summer. So, depending on the natterjacks in your area, you may see males waiting by the pond edge (making loud rasping noises to attract the females), natterjack toad spawn or even some tadpoles!  Natterjack toad spawn is laid in single strings with their tadpoles being smaller than common toad tadpoles and sporting a grey spot on their throat.

Always remember to record your amphibian and reptile sightings on our FREE Dragon Finder app. All of the data collected is sent to the National Biodiversity Network Atlas. You can download the app here.

#pawsagainstponds Campaign

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During April, we will be running our #pawsagainstponds campaign! Britain is a nation of dog lovers, there are over 12 million in the UK and here at Froglife we love our furry friends, in fact many of our staff and volunteers are dog owners themselves. However, dogs swimming in ponds can have negative impacts on wildlife and we want to focus on reducing this and raising awareness of the issue.

Keeping dogs out of ponds used by amphibians for breeding is important for three reasons:

  • Dogs swimming and paddling in ponds can stir up sediment, blocking out valuable sunlight for aquatic plants and spawn/tadpole development.
  • Trampling spawn, tadpoles and froglets/toadlets
  • Spot-on flea treatments can have a devastating impact on aquatic ecosystems. If dogs go into ponds shortly after treatment, the powerful pesticides can kill the insect life within the pond. You can find further information on the British Veterinary Association’s webpage here. 

There can also be negative impacts on dogs including:

  • Illness and risk of death from blue-green algae. Please read the British Veterinary Association’s article on the subject (with advice on what you can do to prevent your dog from becoming ill) here
  • Injuries from hidden hazards below the water
  • Infections from existing cuts and injuries or ones sustained whilst in the water  

If you see a pond that is well planted and appears to be a designated wildlife habitat, try to keep your dogs away or even better, on a lead, particularly in spring when amphibians will be breeding and in the summer when young amphibians will be leaving their ponds for terrestrial habitats.

Ziggy being a very good girl!

What alternatives are there?

We still want dogs to enjoy water, but we want to keep wildlife as well as the dogs themselves safe when doing so. There are some brilliant alternatives to swimming in wild water including:

  • ‘Dog swim days’ You can check outdoor pools in your area to see if they provide this service. There are some great suggestions here. 
  • Head for the beach! Remember to check if dogs are allowed on your chosen beach before travelling
  • Sourcing an old paddling pool or sandpit and making a doggy pool in the comfort of your own garden
  • Play with sprinklers- hook one up to your hosepipe and watch your dog enjoy it- you could even join in with them! (be aware of local hosepipe bans in the summer months before doing this)
  • Give them an outdoor bath- if you’ve been on a walk and your doggo is a bit dusty/dirty you can bathe them in the garden. Make it fun by adding their favourite toys and don’t forget a nice treat for afterwards

 What you can do to help the #pawsagainstponds campaign:

  • When walking your dog near wild water, please keep them on a lead
  • Use alternatives to swimming in wild water (mentioned above)
  • When building a wildlife pond, consider creating natural fencing (hedges, willow fencing) to prevent your dog from taking a swim. More info here
  • Spread the word! Please share our social media posts and tell your family and friends about the campaign

Further reading:

Here are some useful articles on dogs in ponds

The astonishing diversity of reproductive modes in amphibians: a new classification

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Written by Roger Downie, Froglife Trustee and University of Glasgow

In the UK, we are accustomed to amphibians breeding in the spring and depositing their eggs in freshwater bodies, usually ponds rather than streams or lakes. Frogs deposit their eggs as a clump of jelly; toads as strings; and newts wrap theirs individually in folded leaves. The embryos hatch as larvae and feed in the water until they are ready to metamorphose into juvenile versions of the adult form. The adults spend no time with their eggs after deposition. So far, so familiar. But, when we look beyond our UK species, we find a wide diversity of reproductive modes. How many, and what are they like?

The term ‘reproductive mode’ (RM) was coined by Breder and Rosen (1966) to help them make sense of reproductive diversity in fish. Later, Salthe and Duellman (1973), in the context of amphibians, defined RM as a set of characters including oviposition site, ovum and clutch characteristics, rate and duration of development, stage and size of hatchlings, and type of parental care, if any. Without using the term RM, Boulenger (1886) had identified 10 amphibian modes. A hundred years later, Duellman and Trueb’s (1986) textbook recognised 29 RMs in anurans, seven in urodeles and two in caecilians. Haddad and Prado (2005) extended this to 39 modes for all amphibians, and there have been a few additions since. However, Nunes-de-Almeida et al. (2021) have now published a new classification, identifying 74 RMs in amphibians, almost a doubling of the 2005 list. How and why?

Their method is to divide the reproductive process into a set of eleven characters where each species can be assigned to one of two (occasionally more) states. The characters are:

  1. Reproduction type: oviparity (egg-laying) or viviparity (eggs not laid: the female gives birth to larvae or juveniles). Viviparity is common in caecilians, but also occurs in a few frogs and salamanders.
  2. Oviposition macrohabitat: eggs are deposited into the environment or they develop in or on the body of either the female or the male parent.
  3. Spawning type: the distinction here is between cases where eggs are immersed in froth, or not. Froth is made from oviduct secretions in two ways: either a foam is generated by beating movements of the adults’ limbs; or bubbles are made by the female’s jumping movements.
  4. Oviposition substrate: either in water, or not in water: on the ground, or in vegetation, or attached to a parent.
  5. Medium surrounding the eggs: the main distinction here is between two kinds of aquatic habitat: lentic (still water, like a pond) or lotic (flowing waters, such as streams). The medium can also be air, as in eggs deposited on the ground, or attached to a parent’s body.
  6. Nest construction: a constructed nest is defined as a place to deposit eggs which the parents have made by digging, or cleaning, or building in some way. ‘Froth’ nests are excluded from this category (I’m not sure this exclusion is fully justified). Constructed nests can be burrows, or depressions, or cleared areas on the forest floor, or leaves folded around the eggs.
  7. Oviposition microhabitat: here, Nunes-de Almeida and colleagues find 15 variables: eggs on the surface of water, at the bottom of a pool, on the ground, on a leaf, on a rock, in a bromeliad tank etc.

The remaining characters distinguish different patterns of development:

  1. Embryonic development: can be indirect, with a larval stage, or direct – lacking a distinct larval form, and progressing directly from embryo to juvenile.
  2. Embryonic nutrition: all amphibians have yolky eggs, and the yolk provides the nutrients needed for embryonic development, but in some cases the mother provides additional nutrients. Where all nutrients derive from the yolk, development is termed lecithotrophic; where the mother provides extra, it is matrotrophic.
  3. Larval and newborn nutrition: when embryos hatch and become free-living, we consider them as larvae. Generally, this marks the stage when they begin to forage for food, although they still have some of the egg-yolk left. However, some species do not feed as larvae, but obtain their nutrition from their large remaining yolk reserves: these are termed endotrophic. Most larvae are exotrophic, obtaining most of their nutrition from external food sources. In a few cases, parents provide this nutrition. For example, so-called trophic eggs, unfertilised eggs deposited by females to feed their hatched larvae. Another example is the feeding of some caecilian young on their mother’s skin secretions.
  4. Place of larval development: mostly this occurs either in a pool (lentic) or a stream (lotic), but there are also cases of larval development on land, or attached to a parent’s body.
Credit: Julia Page

Overall, the authors reviewed RMs in 2171 species on which they could find adequate information: this is 26 % of all amphibians (8393 species, November 2021). Anurans showed 71 of the 74 RMs; urodeles 16 and caecilians seven. Most species showed a single RM, but some fitted up to four of the modes.

Nunes-de-Almeida and colleagues have made a valiant effort to classify the rich diversity of amphibian RMs, but it is not without some problematic aspects. One omitted feature is fertilisation mode: internal or external. This is a crucial feature in research on reproductive strategies relating to certainty of paternity and male competition. Another aspect largely omitted is parental care behaviour. Parental care can be defined as non-gametic investments in offspring that incur a cost to the parent, but which provide a benefit to the offspring. Parental care in amphibians is discussed in Croaking Science (date to come). The new RM classification  explicitly excludes parental care on the grounds that parental care information is lacking for too many species. However, many kinds of parental care are actually included: for example, the provision of trophic eggs to larvae (character 10 above); while others such as larval transportation by adults are omitted. Another omitted feature which I find surprising is the differences in anuran spawn characteristics: single non-adhesive eggs, eggs in clumps, eggs in strings. It is likely that these differences are evolved characteristics important to reproductive success, so should be included in a classification of RMs. Another omission is the diversity of larval forms: there is huge diversity in tadpole form and behaviour, related to the habitats they live in: this may go beyond the usual definition of an RM, but is an important aspect of reproductive success. There are also occasional inconsistencies: phyllomedusine tree frogs wrap their egg clutches in leaves, and this is classed as a constructed nest (character 6 above); newts wrap their eggs individually in leaves, but this behaviour is not acknowledged as a kind of nest construction.

One excellent point made by the authors is about plasticity: i.e. individuals within a species may vary their RM, depending on circumstances. One example I’ve observed is the giant tree frog Boana boans. These frogs generally construct nests, as basins in gravel or sand (character 6 above), just beyond the edge of streams. However, where there is no suitable ‘beach’, the eggs are deposited at the water surface amongst emergent vegetation.

I’m sure that this new RM classification will stimulate discussion and research, and that later versions will include more species and modes. The authors hope that their work will stimulate the development of RM classifications for other taxa: how about reptiles?

References

Breder and Rosen (1966). Modes of Reproduction in Fishes. Natural History Press, New York.

Duellman and Trueb (1986). Biology of Amphibians. Johns Hopkins University Press, Maryland.

Haddad and Prado (2005). Reproductive modes in frogs and their unexpected diversity in the Atlantic forest of Brazil. Bioscience 55, 207-217.

Nunes-de-Almeida et al. (2021). A revised classification of the amphibian reproductive modes. Salamandra 57, 413-427.

Salthe and Duellman (1973). Quantitative constraints associated with reproductive modes in anurans. Pp 229-249 in: Vial (ed.) Evolutionary biology of the anurans. University of Missouri Press, Columbia.