Snails used for human consumption: The case of meat and slime

by Daniela R. Waldhorn25 min read6th Feb 20208 comments

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Sentience & ConsciousnessFarmed Animal Welfare
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Executive summary

The number of snails produced for human consumption increases gradually every year. Still, there is very little awareness about the details of snail production or how serious an ethical problem it might be. In this report (full version available here[1]), I assess snail production and farming-specific welfare concerns, and discuss some scale, neglectedness, and tractability considerations. Some of our main findings are:

  • Welfare concerns:
  • In the farm: High density, movement restrictions, and different kinds of diseases result in high mortality rates.

  • Processing: Commonly traded alive, and again with virtually no space to move.

  • Slaughter: Typically boiled to death.

  • Scope: It can be estimated that between 2.9B to 7.7B[2] snails were slaughtered for their meat worldwide in 2016.

  • Neglectedness: invertebrate welfare is an issue that has not gained much attention within the effective altruism community. Even in academia, there is a general lack of concern for studying welfare-related issues about snails.

  • Tractability: The most prevalent snail pathologies and their possible treatments need to be identified. We know of no large-scale initiatives to improve the situation of snails used for human purposes.

Although the snail market looks strong, a sharp increase in production is not expected. All things considered, I conclude that investing specific efforts on behalf of snails used as food may not be cost-effective. Still, further research may uncover specific welfare measures on behalf of these animals.

Introduction

For the last while, Rethink Priorities has been studying invertebrate sentience, invertebrate welfare, and more recently, the lives of farmed invertebrates. All our work on invertebrates is available here. Currently, we are focusing our efforts on farmed invertebrates because ameliorating their suffering is likely to be more tractable than intervening in nature to help wild invertebrates. Additionally, the number of farmed invertebrates for different purposes stands to increase in the future, while that is unclear regarding invertebrates living in the wild.

Understanding the situation of farmed snails seems relevant since these animals are consumed by humans in many cultures. Presumably, the problem is of considerable magnitude, and it may be increasing steadily. Indeed, according to FAO (2019a) data[3], the tonnes of snails produced for human consumption (e.g., 18,331 tonnes in 2017) rise gradually every year. However, not much is known about these animals' quality of life and the conditions in which they are raised. Still, it is known that snails are typically slaughtered by boiling. If these animals have valenced experiences, it is probably an extremely painful way to die.

While snails are used for different purposes–e.g., to eat their meat, to eat their eggs as a type of caviar, or to obtain snail slime for use in cosmetics–, this report focuses on what appears to be, nowadays, the main driver of snail farming: snail meat consumption. Since the use of snails in cosmetics is rapidly growing in popularity, relevant aspects about snails exploited for extracting their slime are addressed, where possible.

This report is organized as follows: First, some general aspects of snail production are assessed. Second, some welfare issues associated with snail production and consumption are raised. Third, I discuss some scale, neglectedness, and tractability considerations. Fourth, I suggest key issues that further research should attend to, in order to improve our current understanding of snail sentience and welfare. Lastly, I conclude by emphasising some directions for future work on snails used for human purposes.

Still, this work has some inescapable limitations. Although snails are consumed in several parts of the world, this report focuses on Europe, because it is the main center of global snail consumption. For the same reason, most of its findings refer to Helicidae snails, that is, to the snail species that are typically produced or consumed in Europe.

Furthermore, scientific literature and official data on snail farming and collection are remarkably scarce. Moreover, most of the relevant literature is in the languages of the countries where snail production is a relatively important activity–mostly, Mediterranean countries. However, because of time constraints, only sources in English and Spanish were exhaustively researched for preparing this report. Thus, it is likely that relevant literature in other languages was missed[4].

Snail production

Which snail species are caught or reared for human consumption?

Though not all land snails are considered "food", different sources estimate there are dozens of edible species (e.g., Cobbinah et al., 2008: 12). Broadly, two main groups of snail species are used for human consumption: the European and African ones.

Most of the European snail species (e.g., Cornu aspersum, Helix pomatia) belong to the Helicidae family. The snails usually farmed or gathered in other non-tropical regions (e.g., in North America) belong to this family as well (e.g., Helix lucorum). African species (e.g., Achatina achatina, Archachatina marginata or Achatina fulica), for their part, belong to the Achatinidae family (Cobbinah et al., 2008: 10-21; Elmslie, 2005: 97-101).

Snails collected from the wild

Traditionally, snails were not farmed, but directly collected from the wild during the rainy season, either for sale or for direct consumption (Cañas, 2018; MAPAMA, 2019; Ngenwi et al., 2010).

Snail gathering is a relevant source of livelihood for rural dwellers in the humid forest and derived savanna zones of West and Central Africa (Hardouin et al., 1995; Ngenwi et al., 2010).

In European countries, picking snails from the wild has been a traditional and ancestral activity, common in several regions of France or Spain (Duhart, 2009). However, during the twentieth century, the overcollection of these animals and other factors depleted snail populations in the wild (Conte, 2015; Gheoca, 2013a). Concomitantly, the tradition of collecting and eating wild snails has declined over time (Elmslie, 2005: 93-94).

Snail farming: Systems of production

In Europe, the revitalized interest in heliciculture mostly results from the shortfall in collection of wild snails (Conte, 2015; Gheoca, 2013a). Thus, snail farming is considered necessary “to prevent overexploitation [of snails living in the wild]” and ensure a “sustainable production” (Çelik et al., 2018: 189). Similarly, indiscriminate snail harvesting and climate change in West Africa have encouraged the development of small-scale production systems in that region as well (Hardouin et al., 1995; Ngenwi et al., 2010).

As far as housing is concerned, at least three types of snail farms are identified. In increasing order of complexity, management, and financial inputs, these farming systems are: extensive, semi-intensive or mixed, and intensive (FAO, 2013; Iglesias & Castillejo, n.d.; Thompson & Cheney, 2008; see also Padilla & Cuesta, 2003: 94-102. For images of different types of snail farms see Iglesias & Castillejo (n.d.) –in Spanish):

  • Extensive system: Also known as the free-range system. This is an outdoor farming method that replicates the snails’ natural habitat. Hence, environmental conditions are not controlled. In these farms, the animals feed on the plants they are provided with in the pen, and animal density is low. Typically, in extensive farms, animal density is low.
  • Semi-intensive or mixed system: In these cases, snails are reared part indoors, part outdoors. First, egg-laying and hatching occur in a controlled indoor environment. After 6-8 weeks, snails are removed to outside pens until they grow to maturity.
  • Intensive system: The entire production cycle is carried out in an indoor environment, where temperature, humidity, light, and feed are strictly controlled. These closed systems may be plastic tunnel houses, greenhouses, or other buildings with a controlled climate such as industrial units. In these facilities, animal density is usually high.

After reproduction and hatching, snails raised under optimal conditions may go through three other stages of their life cycle (Padilla & Cuesta, 2003: 94):

  • Newborn snails: the first 1-2 months of a snail's life –in C. aspersum;
  • Growing: snails reach their maximum weight. It lasts around 6-7 months in C. aspersum;
  • Fattening: snails reach sexual maturity and some of them may be used for breeding.

Welfare concerns

Production of farmed snails and snails living in the wild

Demand, the overexploitation of wild snails, together with the fact that heliciculture does not require a substantial investment (Conte, 2015; FEAGAS, 2015), suggest that, in the future, snail production will progressively depend on snail farming. In light of the foregoing, this section mostly refers to farmed snails. In particular, two main topics are addressed: first, factors associated with habitat and environmental conditions; and, second, health indicators.

Habitat and environmental conditions

Health indicators

Some of the main threats affecting snails are infectious and parasitic pathologies and predation (Padilla & Cuesta, 2003: 102). All of these factors can affect the well-being of snails to varying degrees, and may result in high mortality rates.

  • Diseases and parasites: Snails can suffer various infectious diseases, but probably the most harmful are epizootic[6] diseases. These pathologies are usually related to bacterial agents (Padilla & Cuesta, 2003: 102; Raut, 2004: 599-611). In general, these diseases can quickly appear and decimate farmed snail populations–around 70-80% of individuals (Padilla & Cuesta, 2003: 102). In these facilities, diseases are often caused by poor farm maintenance or abrupt environmental changes (i.e., in humidity or temperature) (Cuéllar et al., 1986).

Similarly, numerous species of diptera, mites, helminths, protozoa, and fungi are known to parasite snails and affect their health. Additionally, these animals can act as vectors (intermediate hosts) of parasites for other animals in the wild (Padilla & Cuesta, 2003: 102-103).

Although snails are subject to a range of pathologies, very little is known about them (Raut, 2004: 599-611). Typically, no preventive or curative treatment is applied to these animals "due to poor knowledge of snail pathology” (Dupont-Nivet et al., 2000: 454).

Additionally, mortality rates among breeding snails seem to be higher. According to different sources, at least 21% and up to 70% of breeding snails typically die (Cuéllar et al., 1986: 123; Daguzan et al., 1981; Daguzan et al., 1985).

It is not known whether mortality rates are higher or lower for snails living in the wild.

To summarize, the following table (fig. 1) lists the welfare problems described above, and estimates which of them are more prevalent in snails under different farming systems. Based on our literature review, each aspect is ranked from "low," "medium" to "high" importance for each method of exploitation:

Fig. 1. Importance of potential snail welfare issues, in different systems of exploitation.

Transportation and sale of snails used as food

Collection and preparation

Typically, only adult snails are harvested, either in farms or when snails are collected from the wild (Iglesias & Castillejo, n.d.). Images suggest that snails are collected manually and stored in sacks (see fig. 2)

After collection, snails are purged of anything unhealthy they may have eaten. Traditionally, purging involves a period of fasting of five or six days. (Thompson & Cheney, 2008). Then, snails are washed, examined and cleaned. Commonly, juvenile individuals and small adult snails are discarded, since they are not commercially desirable (Iglesias & Castillejo, n.d.; Thompson & Cheney, 2008).

Fig. 2. Collection and storage of live snails. Source: Touchstone Snail, 2015a.

Afterward, snails are packed together, and practically impeded of all movement. It is known that frequent handling can place significant stress on these animals (Çelik et al., 2018), and overcrowded conditions typically have a negative impact on snail health (Cobbinah et al., 2008; Daguzan et al., 1981; FAO, 2013; Thompson & Cheney, 2008). Hence, probably, all this process is extremely stressful for the animals.

Shipping conditions

For shipping–whether for processing or direct commercialization–snails are packed in containers (e.g., into sacks in plastic crates). Several pictures regularly show snails packed in sacks in overcrowded conditions, crushing each other (see e.g. Touchstone Snail, 2015a).

Live animals are transported in refrigerated containers by truck, ship, and also by plane (Touchstone Snail, 2015b). The low temperatures in these containers (around 4º C) should neither kill the animals nor freeze them either, but induce hibernation (Thompson & Cheney, 2008; Touchstone Snail, 2015b).

Processing and commercialization

In Africa and some European countries (e.g., Spain, Portugal), snails are commonly sold live in markets, packed in sacks or baskets. Snails are crowded together, crushing each other (see e.g. Aloise, 2012). Since–unlike when shipped–animals are not now usually exposed to low temperatures, they remain active and foraging[7]. Even so, snails can hardly move at all. These conditions often result in very high mortality rates (Hardouin et al., 1995).

In other cases, snails are processed to be sold blanched, frozen, or canned to be ready for consumption (Escargot World, 2016-17; Touchstone Snail, 2015a).

Slaughter conditions

Typically, snails are slaughtered by boiling. First, the animals are washed and soaked in water. Then, snails are put in boiling water and cooked to death (Thompson & Cheney. 2008). Discussing whether snails are sentient is beyond the scope of this report. However, it is worthwhile to consider that Helicidae snails do display avoidance behavior in response to high temperatures (see Balaban, 2002, and Ierusalimsky & Balaban, 2007 in Crook & Walters, 2011).

Furthermore, in countries like Spain, other killing methods are employed, like low temperature cooking and drowning. The second technique consists in placing the animals in a plastic bag, or into a large bowl, full of water, for at least six hours. While the animals are being slowly cooked or while they are drowning, they try to escape, even leaving their shells behind. Hence, when using these methods, snails typically die out of their shells (Chilla, 2019; CocinAdictos, 2012).

Thus, after being excessively handled during washing, snails die slowly by boiling or drowning. If these animals are sentient, any of these methods is likely to cause severe suffering. In particular, drowning and cooking on low fire possibly cause a prolonged period of agony.

Welfare concerns: production of snail slime

Snails secrete mucin not only to move but when they are perturbed or threatened (Greistorfer et al., 2017; Newar & Ghatak, 2015). Hence, traditionally, slime is obtained from snails that are physically stressed by different forms of stimulation (Alcalde & del Pozo, 2008). This process is called “milking” snails.

A widespread method of “milking” snails consists in exposing them to substances that these animals tend to repel–vinegar (acetic acid) or salt (Sampò, 2017 in Mitzman, 2017). The noxious substance is poured on them (Bucher, 2007 in Diario Sur, 2007), or snails are dunked in pots of water with those substances (Vogt, 2017). These elements quickly suck the water out of the animals’ cells by osmosis. As the snail dries out, its body secretes slime to protect itself. If snails are sentient, being immersed in a saline solution would probably feel like being burned alive (UCSB ScienceLine, 2017). Due to the severe dehydration it causes, this process kills the animals (Sampò, 2017 in Mitzman, 2017; UCSB ScienceLine, 2017).

Snail mucin producers appear to be reluctant to give details about their techniques[8]. Overall, their methods and implications for snail welfare remain obscure or vague.

Scale, neglectedness and tractability considerations

Scale

According to different sources, it is almost impossible to get reliable production and consumption numbers of snails, since a large percentage of them are collected from the wild (Cuttelod et al., 2011; MAPAMA, 2019; Touchstone Snail, 2015a).

FAO (2019a) estimated that 18,331 tonnes of snails were produced worldwide in 2017 (see fig. 3)[9]. However, according to Irina Kovrova (personal communication, 29 August 2019), statistician of the Crop, Livestock, and Food Statistics Team at FAO, “since no country provides us the snail production data [emphasis added], our snail production data are underestimated.”

Fig. 3. Tonnes of snails produced worldwide per year, from 1987 to 2017. No data for previous years was found. Own elaboration based on data from FAO (2019a).

If the tonnes of snails produced annually are higher than the numbers provided by FAO, the question that now arises is by how much. Without official statistics on the matter, answering this question is especially tricky. This lack of official data led us, then, to consider other sources. Out of all of them, and after contrasting further evidence, it was concluded that the data provided by Indexbox (2018 in Food Dive, 2018)[10]was worth taking into account.

Indexbox (2018 in Food Dive, 2018), a market research company, states that in 2016, the global snail market amounted to 43,000 tonnes–that is 2,500 tonnes less than in 2010 (Indexbox, 2019). The same source claims that the five major producers of snails worldwide are Morocco (15,000 tonnes), Spain (6,500 tonnes), Indonesia (5,900 tonnes), China (2,900 tonnes), and Romania (2,000 tonnes). These five countries represent around 75% of global snail production.

Based on Indexbox’s (2018 in Food Dive, 2018) data, I estimate that between 2.9B to 7.7B snails were slaughtered worldwide in 2016 for their meat (see the Appendix section). Of this interval, let’s consider the worst-case scenario–that is, the one where the highest number of snails are killed[11]. 7.7B snails equals more than five times the recorded number of pigs slaughtered in 2016 for their meat (i.e., 1,480,741,771 animals, according to FAO, 2019b[12]). Nevertheless, this estimate represents about 11.7% of the recorded figure of chickens slaughtered for their meat in that same year (i.e., 65,787,732,000 animals, according to FAO, 2019b). The following graph (fig. 4) illustrates these differences:

Fig. 4: Comparison of number of snails, pigs and chickens slaughtered for their meat in 2016, based on FAO (2019a) and Indexbox (2018 in Food Dive, 2018) data.

For a more complete assessment of the scope of the problem, it is also necessary to consider how many snails may be alive in the industry at any time. Given the underestimation of the FAO (2019a) figures, I calculated that number based solely on the data provided by Indexbox (2018 in Food Dive, 2018), as detailed in Appendix. In this case, I estimate that in 2016 between 3.8B to 12B snails were alive at any time, in order to meet the market’s annual demand.

How to interpret the magnitude of these figures? Again, comparing them with the number of pigs and chickens alive at any moment can help to better understand the scope of the problem. As previously, let’s consider the worst-case scenario–that is, the highest number of the interval, or 12B snails alive at any time. 12B equals more than 12 times the recorded number of pigs alive at any moment in 2016 (i.e., 978,466,142 animals, according to FAO, 2019c[13]). Still, this number is far less than the number of chickens alive at any time that same year (i.e., 22,562,532,000, according to FAO, 2019c). In particular, it is slightly more than half (53.2%) the number of live chickens in the meat industry in 2016. These differences can be observed in the following graph (fig. 5)[14]:

Fig. 5. Comparison of number of snails, pigs and chickens alive at any time in 2016, based on FAO (2019c) and Indexbox (2018 in Food Dive, 2018) data.

In the meantime, we can conclude that, even assuming that snail meat production causes massive suffering, this problem is of much lesser magnitude than the exploitation of some farmed vertebrates like chickens–or fishes caught from the wild (see Fishcount.org.uk, 2019)–both because of the greater number of individuals involved and because there is much more solid evidence that these vertebrates are sentient.

Overall, given the gradual reduction of the international trade value of edible snails during the past years (see Chatham House, 2019; IndexBox, 2018 in Food Dive, 2018; Indexbox, 2019; Tridge, 2019; United Nations, 2019), a similar trend may be expected in the near future. Additionally and except for Morocco, it seems unlikely that the production of snails for their meat will grow significantly. Rather, production may tend to remain relatively stable in the short term. In some countries (e.g., Spain), consumption may progressively diminish throughout the next decades. Furthermore, given the cultural specificity of eating snails (Elmslie, 2005), I consider that existing markets for snail meat are limited and that it is unlikely to expand to new ones.

Nevertheless, the situation may be different for snails used for slime production. Seemingly, the boom of snail mucin-based cosmetic products is one of the major causes of positive trends in the snail farming industry and its future growth, at least in countries like Italy and Morocco (Kasraoui, 2017; Vogt, 2017). However, no data was found about the amount of snails used by this industry.

Neglectedness

As outlined in a previous post, invertebrate welfare is an issue that has not attracted much attention within the effective altruism community. In particular, beyond the effective animal advocacy ecosystem, very few organizations are concerned about snail welfare (in the Anglo-Saxon world, see e.g. PETA).

Nevertheless, it must be stressed that neglectedness, in itself, is not a sufficient argument for considering snail welfare to be important. We should also examine whether there are good reasons why effective altruism or animal welfare organizations are not investing resources in a given issue. It might be, for example, that the problem–as such–does not exist. That would be the case if we found out that snails are possibly not sentient. But even assuming our current uncertainty about snail sentience, we may have other good reasons (e.g., tractability-related reasons) for not prioritizing their welfare. For instance, suppose we concluded that the exploitation of snails for their meat will start declining in the near future. If so, in a few years’ time, without any kind of intervention on our part, the problem may disappear or, at least, become much less serious. In this scenario and considering the opportunity cost of helping snails and not other individuals, we may have good reasons for not investing additional resources in this cause.

In this respect, we may have good reasons for not openly promoting snail welfare– or, at least, for not promoting it among the general public. First, because of our uncertainty about snail sentience and snail welfare tractability. Second, because of the psychological barriers that make the moral consideration of animals like snails especially difficult for us (see Invertebrate welfare: Thinking about directions for future work, Part 3). Therefore, we must be cautious when assessing to what extent the neglectedness of snail welfare should be considered a strong consideration in favor of working on this issue.

Tractability

If there is minimal information about snail welfare, even less knowledge is available about possible interventions on behalf of these animals. Nevertheless, I believe there are a few, specific recommendations that can be made to improve snail welfare:

  • Developing optimal rearing conditions: Rearing densities is a crucial aspect for snail welfare. Although there is no explicit agreement on optimal density conditions, Charrier and Daguzan (1978 in Dupont-Nivet et al., 2000) suggest an optimal growth performance density of 133 individuals (C. aspersum) per m2. Therefore, we can assume that density levels above this limit are detrimental to snail welfare.

Additionally, researching on the most prevalent snail pathologies and their possible solutions can potentially make a significant difference in snail welfare.

  • Developing better methods for handling and transportation: The adverse welfare effects of shipping can be ameliorated if it is carried out between late fall and before spring begins when snails are naturally “dormant” (hibernating). However, it should be noted that in dry regions, snails may remain inactive during the hot dry season, which is usually during the summer months (estivation)[15].
  • Discouraging the sale of live snails for direct consumption: If snails are sentient individuals, the deprivation conditions in which they are sold live in popular markets probably imply prolonged suffering. However, if these conditions are likely to create sanitary problems or threaten food security, this is a good reason for an eventual ban on the sale of live snails for direct consumption.

Although banning the sale of live snails may seem promising, in some European countries (e.g., France), most of the snail meat commercialized is already processed, either frozen or blanched (Touchstone Snail, 2015a). If this trend is progressively adopted by other countries–as it seems to be happening in Spain, for example–, promoting a ban on the sale of live snails may not be cost-effective.

  • Developing better methods of killing: According to Dr. Donald Broom, “cooling them [snails] right down in the freezer to slow their nervous processes, and making sure that the water you drop them into is already boiling, is the best way to ensure they are killed quickly” (CooksInfo, 2004; Rivera, 2016). Furthermore, a recent investigation suggests dipping snails in beer to sedate the animals before killing them (Gilbertson & Wyatt, 2016).
  • Implementing better methods of slime production: The Muller One is a device that consists of a metal base, with two plexiglass domes under which snails are placed (see Lumacheria Italiana, n.d.). In this apparatus, snails are exposed to ozone, and other natural (undefined) substances, which stimulate them to produce slime (Lumacheria Italiana, n.d.; Mitzman, 2017). By the same token, one Italian cosmetics brand has developed a very similar device, called the OzoSnail (Vlifestyle, 2017). The creators of both devices claim that these methods do not harm the animals in a significant way. However, the high price of the Muller One[16] probably makes this device not affordable for a large part of producers.

As observed, large-scale interventions on behalf of these animals were not found. Thus, I consider that the tractability of snails consumed for their meat is low, or at least, uncertain.

Other general considerations

Given current demand and trends, any initiative aimed at improving the situation of most of the snails consumed for their meat should target Spain, Morocco, and to a lesser extent, France. However, if production remains relatively stable and the market continues to slow down, along with the low or uncertain tractability of the problem, it can be argued that investing efforts on behalf of snails used for their meat may not be cost-effective.

Nevertheless, the boom of snail mucin-based cosmetic products has boosted the snail farming industry. Given the above, improving the exploitation conditions of snails used for cosmetics could have a more significant impact in the future than affecting the breeding of snails for other purposes.

Key issues that should be addressed

Are snails sentient individuals? If so, how should they be morally considered?

Whether snails have a capacity for valenced experience is still uncertain. Studying extant evidence about these animals will be of interest not only because of the extensive use of snails, but also to better understand the distribution of sentience within Mollusca.

Mollusca is a very broad phylum with over 100,000 species, encompassing organisms of enormous diversity (Crook & Walters, 2011). Thus, albeit snails are part of the Mollusca phylum, we are much less confident about whether they are conscious than we are regarding other Mollusca members such as coleoid cephalopods (see our previous work on this matter here). Hence, further research is needed about whether these animals are conscious, and if they are, how we should morally consider snails compared to other moral patients.

How can we improve the life of snails under human control?

One major challenge to improving snail welfare is that further recommendations on this matter seem to be unavailable. Snail health problems, for example, although an essential aspect of the animals’ welfare, are a much neglected topic. In this regard, further research on the most prevalent snail pathologies, preventive health care, and treatment of these diseases is highly needed. Similarly, other welfare indicators should be assessed, including adequate feeding and, if relevant, behavior-related indicators specific to these species (e.g., deviations from normal behavior). Further research is also needed to discover the preferences and understand the positive experiences of these animals. This empirical data, together with expert validation surveys, may contribute to elaborating a framework for assessing snail welfare, similar to the FOWEL model for hens raised for their eggs. Such a framework can help (i) determine the farming conditions that provide the highest levels of welfare; (ii) identify specific measures for improving snail conditions; (iii) advance in standard farming procedures, as well as (iv) evaluate which killing methods cause less suffering.

Conclusion

This report explores the use of snails for their meat, and to a lesser extent, for extracting their slime. Some factors that affect snail welfare, along with scale and tractability considerations were also discussed.

As stated, between 2.9B to 7.7B snails were slaughtered for their meat worldwide in 2016. Although snail meat production possibly causes massive suffering if snails are sentient, the scope of the problem is of lesser magnitude than the exploitation of some farmed vertebrates like chickens or fishes. Moreover, it is likely that the scope of the problem will progressively diminish, in line with certain market trends. Additionally, despite the problem’s neglectedness, there may be good reasons for not publicly advocating on behalf of snails, especially because we know of no large-scale initiatives to improve their well-being. In this sense, tractability appears as a limiting factor for ameliorating snail suffering, at least in the short to medium term. Still, further research may uncover specific welfare measures and forms of intervention on behalf of these animals.

Nevertheless, the prospects may be different for snails used for slime production. In this regard, further market research may contribute to a better understanding of how important this industry is, its prospects, and how the scale of the problem is likely to evolve.

Finally, if we eventually aim to design forms of intervention that help both snails farmed for different purposes and those living in nature, future work should primarily assess snail biology. That knowledge is fundamental to determine the likelihood of snails being sentient and to obtain a better understanding of the determinants of their well-being.

Credits

This report is a project of Rethink Priorities. Please note, this is a summary of a longer report, available here.

It was written by Daniela R. Waldhorn. Thanks to David Moss, Eze Paez, Jane Capozzelli, Dr. Joseph Heller, Jason Schukraft, Kim Cuddington, Marcus A. Davis, Dr. Pavel Balaban, Peter Hurford, and Saulius Simcikas for their contribution.

If you like our work, please consider subscribing to our newsletter. You can see all our work to date here.

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Appendix: Estimating the number of snails

Number of snails killed

I developed two guesstimate models for the estimates presented in this report: one of them, using FAO (2019a) data, and the second one, employing Indexbox’s (2018 in Food Dive, 2018) figures. Both models (available here and here) are based on the following assumptions:

  • Helicidae snails represent around 70-85% of the world snail market (based on Gheoca, 2013b and Iglesias & Castillejo, n.d.)[17];
  • Therefore, Achatinidae snails represent around 15-30% of the remaining world snail market;
  • The market for Helicidae snails is dominated by C. aspersum (35-45%), H. pomatia (23-33%), and H. lucorum (17-27%). Other Helicidae species represent around 5-15% of Helicidae snails used for human purposes (based on Conte, 2015);
  • The market for Achatinidae snails is dominated by A. achatina, A. marginata, and A. fulica;
  • Snails are harvested when they are adults (Iglesias & Castillejo, n.d.; Padilla & Cuesta, 2003);
  • The weight of Helicidae and Achatinidae snails, as detailed here;
  • A mean mortality rate of newborn snails of 15-25% (based on Padilla & Cuesta, 2003: 99);
  • A mean mortality rate of growing snails of 16-26% (based on Dupont-Nivet et al., 2000).

I assigned wide intervals to Gheoca’s (2013b) and Conte’s (2015) original estimates of snail species in the world market, given that their primary sources and the methodology of their estimates are not specified. However, I could not find any other source with more precise information on the proportion of the different snail species used. Regardless, the data provided by these authors is consistent with assertions from other sources about (i) the relevance of Helicidae snails in the international market, and (ii) the importance of C. aspersum and H. pomatia in comparison to snails of other Helicidae species.

Furthermore, it is highly likely that small quantities of snails reared in pens or harvested from the wild (e.g., for domestic consumption) were not accounted for, as they may represent quantities that are not economically significant in themselves. However, this does not mean that these quantities, as a whole, are not significant. But since no reliable estimates on domestic breeding or collection of snails were found, it is not possible to estimate the importance of this activity.

Number of snails alive at any time

I developed an additional model to estimate the number of snails alive in the industry at any time (available here). Given that the FAO (2019a) snail production data is an underestimate, this model is solely based on the production figures provided by Indexbox (2018 in Food Dive, 2018).

This third model followed the same assumptions as the two previous calculations. In this case, however, I also incorporated the age at which snails of different species are harvested. It should be noted that, in most cases, this information was not directly available. Hence, it was deduced from the age at which snails reach their maximum body weight, or the age at which these mollusks reach sexual maturity –as Iglesias and Castillejo (n.d.), and Padilla and Cuesta (2003) suggest. This information, compiled for Helicidae and Achatinidae snails, is available here.

Nevertheless, these age estimates vary widely since several factors can significantly influence snail growth, including population density, environmental conditions, food availability and quality, and the breeding system and technology used (Thompson & Cheney, 2008). This variability in growth rates–even from one egg batch–is not exclusive to snails, but a common feature of land mollusks (Blinn, 1963; Wagge, 1952; Wolda 1970 in Pollard, 1975).



  1. The full version of this report was reviewed by zoologist-malacologist Dr. Joseph Heller, Professor Emeritus at the Department of Ecology, Evolution and Behavior at the Hebrew University of Jerusalem, and academic curator of the National Molluscs Collection at the same university. I am especially grateful to him for his helpful feedback on this work. Nevertheless, Dr. Heller’s assistance should not be in any way construed as an endorsement of any views expressed in this report. Any possible factual errors and all value judgments are entirely my own. ↩︎

  2. For brevity, I use B for a billion. ↩︎

  3. Parameters: Livestock Primary; World + (Total); Production quantity; Snails, not sea; All years. The complete FAO data is available here ↩︎

  4. Still, some additional literature in French, and to a lesser extent, Portuguese, Italian, and Catalan was surveyed. ↩︎

  5. Following Padilla & Cuesta (2003: 90-92), humidity should be between 80-90%. Temperature, for its part, should be between 10ºC and 30ºC, with an optimum of 17–25ºC. Regarding light, it is recommended that snails have a photoperiod of at least 8-12 hours of light. ↩︎

  6. An epizootic disease is analogous to an epidemic in humans, though occurring in a nonhuman animal population. ↩︎

  7. Generally, low temperatures (and low humidity) inhibit snail activity (CABI, 2018). ↩︎

  8. In addition to surveying the literature, I contacted two other companies about their methods of snail slime extraction –Elicina, one of the first ones to produce snail cream, and Darvėja, an important European producer. However, I received no response. ↩︎

  9. Parameters: Livestock Primary; World + (Total); Production quantity; Snails, not sea; All years. The complete FAO dataset is available here. ↩︎

  10. Unlike other sources, Indexbox’s figures of the main worldwide producers are consistent with United Nations (2019) data on international snail trade. Similarly, its data on snail consumption in Spain is close to the figures estimated by the Spanish government for 2017 (MAPAMA, 2019). Therefore, I assumed that Indexbox’s figures are more reliable than other sources. Still, given the disparity in data on snail production in general, all estimates here presented should be considered with caution. ↩︎

  11. Since there is no data available about mortality rates during transport, numbers of breeding snails used and breeding snails’ mortality rates, the real number of snails slaughtered is probably closer to the upper bound than to the lower limit of the interval –i.e., 7.7B individuals. ↩︎

  12. Parameters: Livestock Primary; World + (Total); Producing Animals/Slaughtered; Meat, pig; Meat, chicken; 2016, 2017. The complete FAO dataset is available here. However, it should be noted that FAO figures mentioned here do not include animals killed in domestic slaughters, animals that die while transported or in any other circumstances before being slaughtered –e.g., animals that die in the farm before reaching their fattening weight. ↩︎

  13. Parameters: Live Animals; World + (Total); Stock; Chickens; Pigs; 2016. The complete FAO dataset is available here. ↩︎

  14. To make these comparisons more meaningful, ideally, we might also consider the severity of harms inflicted on the animal species here compared. However, such an assessment is beyond the scope of this report. ↩︎

  15. I thank Dr. Joseph Heller for this point. ↩︎

  16. Starting from 33,000€ (or $36,788), plus additional delivery and training costs (Donatella Pistagna, personal communication, 17 October 2019). ↩︎

  17. While Gheoca (2013b) states that Helix snails represents over 70% of the world snail market, Iglesias and Castillejo (n.d.) claim that only C. aspersum accounts for 80% of total demand. However, Iglesias and Castillejo estimates seem to be from well before Gheoca's figure. Additionally, it may exclusively refer to farmed snails, since other sources also assert that C. aspersum is the most farmed species in Europe (Padilla & Cuesta, 2003; Martínez, n.d.; Touchstone Snail, 2015a). ↩︎

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