Archives for August 2022

Part 2: Amphibians

Roger Downie, Froglife and University of Glasgow

In Croaking Science (July, 2022), I introduced the topic of the international trade in wildlife, and then focused on reptiles. This article is a companion piece, concentrating on amphibians. It will cover the frogs’ legs and pet trades, discussing their impact on wild amphibian populations, disease spread and amphibian welfare. As I was researching the topic, an excellent report on the frogs’ legs trade appeared (Altherr et al., 2022), and I have drawn heavily from it.

The existence of trade implies that people make use of amphibians. Let’s start by summarising such uses. First, amphibians as food. We may think mainly of frogs’ legs as a delicacy in French cuisine (and certainly not as a dietary essential), but amphibians form part of the diet in many cultures, with frog meat for sale in markets across Africa, Asia and Latin America. The mountain chicken (Leptodactylus fallax) was long the national dish of the Caribbean island of Dominica, until declining numbers led to a hunting ban: chytrid then nearly finished the species off, but major conservation efforts are in progress (Nicholson et al. 2020). Second, people have long been aware of the rich variety of substances in amphibian skins. Traditional healers around the world have employed concoctions from frog skin as medicines and the Amerindians of Latin America famously tip their hunting arrows with the secretions of Poison Dart Frog (dendrobatid frog) skin. Modern research is testing amphibian skin derivatives for substances of real medical benefit (see Crump, 2015: reviewed in Natterchat, Spring/Summer 2017) Third, amphibians have long played a role in scientific research: for example, Galvani and Volta’s 18^th century experiments with electrical stimulation of frogs’ legs.  More recently, the African clawed frog Xenopus laevis became a fixture of hospital laboratories when it was discovered that urine from pregnant women stimulated female Xenopus to ovulate: the basis of the first reliable pregnancy test. Stimulation of ovulation then allowed Xenopus eggs to be the model of choice for studies on embryonic development. Finally, some people like to keep amphibians as ‘pets’: this often involves colourful and exotic species.

Traditional uses, such as being a small component in a local diet or in medicine, do not necessarily involve international trade, nor are such uses likely to create a conservation threat, unless exploitation becomes unsustainable, as in the case of the mountain chicken. However, the frogs’ legs and pet trades are problematic, and this article focuses on them.

Import/export of frogs as food The USA and Europe are the main importers of frogs for food. The USA imports four species: the bullfrog Lithobates catesbeianus from Mexico, Ecuador and China; the East Asian Hoplobatrachus rugulosus from Thailand and Vietnam; Forrer’s leopard frog Lithobates forreri  from Mexico; and the pig frog Lithobates grylio from China. The dominant species was L. catesbeianus, with 14.5 thousand tonnes imported as live individuals or frozen meat over the period 2015-20. Frogs were both wild caught and farmed (note that this species is a USA native, but has been both released and farmed in many other countries).

During the period 2010-19, the European Union (still including the UK) imported 40.7 thousand tonnes of frogs’ legs, derived from 814 million to two billion adult frogs (a wide range because of frog size differences). The most significant importing country was Belgium (69.9%), with France second (16.7%) and the Netherlands third (6.4%). However, much of the Belgian consignments moved on to France which is the predominant consumer country. Indonesia is the main supplier (74%), followed by Vietnam (21%), Turkey (4%) and Albania (1%). India and Bangladesh were formerly major suppliers, but the relevant species were CITES listed in 1985 and exports stopped, with Indonesia becoming the main new source. The species mainly imported into Europe are not reliably known: Ohler and Nicholas (2017) used DNA sequencing to show that 99% of frogs’ legs  for sale in French supermarkets were incorrectly labelled as to their species identity. This is not necessarily deliberate: it is common for collectors of wild frogs in Indonesia not to know the identity of the species, and most of the Indonesian ‘crop’ is wild caught. However, this is clearly a problem if there is a need to conserve species from over-harvesting.

The frogs’ leg trade is mainly as frozen meat, so there are no welfare issues in the transportation phase, but there may well be welfare issues during capture and killing, so far negligibly reported. The Indian trade was halted because of worries that natural populations were becoming severely depleted, but also because of a realisation of the ecological role played by healthy frog populations, especially in rice paddy fields where they help control biting insects: the use of pesticides as an alternative is an extra cost to farmers, as well as adding risks of toxicity (Propper et al. 2020). It is so far unclear whether frog harvesting in Indonesia is having similar effects, but shifts in the species make-up of frog imports suggest some impact on native populations.

Frog farming is seen by some as a means of making the frogs’ leg trade sustainable: frog farming will be discussed in a future Croaking Science article.

Amphibians in the international pet trade Tapley et al. (2011) estimated that 127 species of amphibians were on sale from UK pet shops in 2004-5, an increase of 160% from 1992-3. They argue that the pet trade can benefit source economies and provide a stimulus for conservation by providing local people with an incentive for sustainable harvesting (a similar argument is used to justify trophy hunting in countries where there is potential conflict between large mammals like lions, and local farmers). However, Tapley et al. acknowledge the problem that local people are the least likely to obtain significant financial benefit from live frog collecting. Altherr and Lameter (2020) found 352 amphibian species in the German pet trade in 2017-18. Their particular concern was the number of species offered for sale which had only recently been described by science, and whose status in the wild was usually still unknown. They found 46 species of reptiles and amphibians offered for sale that had been first described in the period 2008-17, one within 3 months of description. It was clear that collectors were able to use the locality details in the scientific description to capture individuals which could then be sold at high prices on the basis of their novelty and rarity. It was also clear that the motivation driving some hobbyists is to possess a collection of rare and exotic species: a live animal collection of this kind is therefore more similar to a collection of artefacts like paintings than it is to possessing pets which can be classed as ‘companion animals’. Auliya et al. (2016) contend that the global trade in amphibians has helped bring many species to the brink of extinction, and that trade regulation urgently needs strengthening. It is noteworthy that, while amphibians are the vertebrate group with the highest proportion of species threatened with extinction (about one third of species), only 197 species (2.1% of the total) are listed in CITES appendices 1 and 2.

One of the causes underlying the worldwide declines in amphibian populations is the spread of chytrid disease. Schloegel et al. (2009, 2012) documented the role of the live wildlife trade in the spread of the disease: they found a prevalence of 62% for chytrid and 8.5% for ranavirus in live frogs imported into the USA. Grear et al. (2021) reported on the ban on live urodele importation into the USA, which has so far been effective in stopping the spread of the urodele-specific species of chytrid, Batrachochytrium salamandrivorans : this disease is a particular worry because of the large number of endemic urodeles in the USA. Borzee et al. (2021) note that the amphibian trade may not only have a role in the spread of amphibian diseases: by affecting insect vector populations, amphibian harvesting may contribute to the spread of diseases of humans and domestic animals.

Finally, welfare. It is likely that the risks to individual amphibians from the live animal trade are higher than to reptiles, given their stringent physiological needs, especially for water. Lambert et al. (2022) discuss the risks to amphibians inherent in the way that they are collected, transported, sold and kept. Ashley et al. (2014) reported on the police raid on the warehouse of US Global Exotics that found large numbers of amphibians in such poor condition that 44.5% died within 10 days of discovery, despite skilled efforts to help them recover.

Conclusion Both the frogs’ legs and amphibian pet trades are highly problematic and need further investigation. It is hard to argue against Auliya et al’s (2016) plea for improved regulation. It may be of interest here that in the Australian state of Victoria, only native species of amphibians and reptiles can be kept by private owners, and that they have to be licenced (Howell et al., 2020). Could such a legal framework be effective elsewhere?

References

Altherr, S. and Lambert, K. 2020. The rush for the rare: reptiles and amphibians in the European pet trade. Animals 10, 1-14.

Altherr, S. et al. 2022. Deadly dish- role and responsibility of the European Union in the international frogs’ legs trade. Pro Wildlife and Robin des Bois. Munich and Paris. Published on-line.

Ashley, S. et al. 2014. Morbidity and mortality of invertebrates, amphibians, reptiles and mammals at a major exotic companion animal wholesaler. Journal of applied animal welfare science 17, 308-321.

Auliya, M. et al.  2016. The global amphibian trade flows through Europe : the need for enforcing and improving legislation. Biodiversity and Conservation 25, 2581-2595.

Borzee, A. et al.  2021. Using the global 2020 pandemic as a springboard to highlight the need for amphibian conservation in eastern Asia. Biological Conservation 255, 108973.

Crump, M. 2015. Eye of newt and toe of frog, adder’s fork and lizard’s leg: the lore and mythology of amphibians and reptiles. University of Chicago Press, Chicago.

Grear, D.A. et al.  2021. Evaluation of regulatory action and surveillance as preventive risk-mitigation to an emerging global amphibian pathogen Batrachochytrium salamandrivorans (BSal). Biological Conservation 260, 109222.

Howell, T.J. et al. 2020. Self-reported snake management practices among owners in Victoria, Australia. Veterinary Record 187 (3), 114.

Lambert, H. et al. 2022. Frog in the well: a review of the scientific literature for evidence of amphibian sentience. Applied Animal Behaviour Science 247, 105559.

Nicholson, D.J. et al. 2020. Cultural association and its role in garnering support for conservation: the case of the mountain chicken frog in Dominica. Amphibian and Reptile Conservation 14, 133-144.

Ohler, A. and Nicholas, V. 2017. Which frog’s legs do froggies eat? The use of DNA barcoding for identification of deep-frozen frog legs (Dicroglossidae: Amphibia) commercialized in France. European Journal of Taxonomy 271, 1-19.

Propper, C. et al. 2020. Role of farmer knowledge in agroecosystem science: rice farming and amphibians in the Philippines. Human-Wildlife Interactions 14, 273-286.

Schloegel, L. et al.  2009. Magnitude of the US trade in amphibians and presence of Bd and ranavirus infection in imported North American bullfrogs. Biological Conservation 142, 1420-1426.

Schloegel, L. et al. 2012. Novel, panzootic and hybrid genotypes of amphibian chytridiomycosis associated with the bullfrog trade. Molecular Ecology 21, 5162-5177.

Tapley, B. et al. 2011. Dynamics of the trade in reptiles and amphibians within the UK over a ten year period. Herpetological Journal 21, 27-34.