Inconspicuous Hermit? Conservation Management Implications from a Decade of Online Wildlife Trade Trends for Land Hermit Crabs

doi:10.21203/rs.3.rs-5274064/v1

Download PDF

Article

Inconspicuous Hermit? Conservation Management Implications from a Decade of Online Wildlife Trade Trends for Land Hermit Crabs

https://doi.org/10.21203/rs.3.rs-5274064/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

Wildlife trade poses a significant challenge to biodiversity conservation, yet invertebrate species often receive less attention. In this study, we focused on land hermit crabs to analyze 10 years of data from Japan's largest online selling platform, alongside public interest trends. Our findings reveal that a total of five species and 6,862 individuals were sold over the past decade. Notably, the number of individuals sold annually and the total revenue significantly increased, correlating with Google Trends data, which suggests rising popularity and demand. The price of these crabs may reflect consumer preferences and potential impacts on species conservation. Our analysis shows that body size, species, and the number of individuals per sale influence price. Additionally, while price is also affected by coloration in certain species and body sizes, no clear pattern was observed. A significant trend we identified is the increase in the proportion of small-sized crabs sold, alongside a decrease in large and extra-large sizes, which could indicate over-fishing. The selling season peaked during the summer, with a small number of sellers accounting for a large share of sales, most of whom were based in Okinawa. This study offers valuable insights for policymakers, including the need to manage catch volumes and sizes, collaborate with local stakeholders, and re-evaluate selling certifications. Importantly, it provides the first evidence of long-term trade in land hermit crabs, offering critical information for the conservation of these popular exotic invertebrates globally.

Biological sciences/Ecology/Biodiversity

Scientific community and society/Social sciences/Interdisciplinary studies

Wildlife trade is a significant issue for biodiversity conservation¹. It can impact wild species populations positively and negatively, with its sustainability depending on effective governance of the intricate interactions among biological, economic, and social factors². Well-managed, sustainable wildlife trade can benefit both humans and wildlife conservation and should be promoted^3,4. However, unsustainable wildlife trade is a major factor contributing to the decline of target species populations and overall biodiversity¹. Additionally, unsustainable wildlife trade causes numerous problems for both the environment and human society, including the introduction of invasive species, bycatch, disease transmission, increased crime, and negative impacts on local and global economies⁵. These complex challenges highlight the urgent need for comprehensive research and effective management strategies.

Grasping trends in wildlife trade are crucial for understanding the dynamic changes in the conditions of selling flora and fauna ⁶. Many studies on wildlife trade rely on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) database, which is one of the most powerful and comprehensive global data sources (e.g., ⁷). However, it has been argued that the lack of direct empirical evidence can lead to a significant risk of misunderstanding the impacts of harvesting on dynamic populations of wild species⁸. In recent years, the internet has become a significant platform for wildlife trade⁹. Therefore, collecting comprehensive, consistent, and objective online trade data is crucial. Stringham et al. (2021) developed guidelines to quantify the online wildlife trade, providing a valuable tool for this purpose¹⁰. Beyond understanding trade trends in volume, it is also vital to analyze the price of individuals and the factors influencing these prices. This analysis is essential for understanding species rarity and consumer preferences, which are critical for informing conservation policy.

Understanding the price of species in the wildlife trade is essential as it often reflects consumer preferences and the rarity of the species¹¹. Therefore, exploring the complex economic and ecological interactions is essential for devising effective conservation strategies against the Anthropogenic Allee Effect, particularly where high market prices coincide with dwindling wild populations¹². Consumers have a strong preference for species rarity, and results from a choice experiment show that buyers of caged birds indeed value this rarity, which can lead to wildlife overexploitation and species extinction¹³. Moreover, numerous studies on different taxa have demonstrated consumers' preference for rarity associated with high prices, such as beetles, butterflies, and turtles^14–16. For crustaceans, most species are considered as food, except for a few species kept as pets, like crayfish¹⁷. In this study, we focus on a recently popular exotic crustacean species, land hermit crabs, to explore trade trends and provide management implications globally.

Land hermit crabs are becoming increasingly popular as exotic pets. However, because they are very difficult to breed in captivity for commercial purposes (e.g., high costs and high mortality rates)¹⁸, most of the land hermit crabs on the market are wild-caught. Some reports have revealed the unsustainable and unregulated trade of land hermit crabs^19,20. However, land hermit crabs play important roles in coastal ecosystems; they help disperse plant seeds²¹, accelerate the nutrient cycle²², and serve as food sources for other animals²³. Additionally, they provide cultural services for coastal residents. For example, they hold significant life memories for residents in coastal communities in Taiwan²⁴ and they play sacred roles in linking humans and heaven in Okinawa, as they consume human corpses left on coastal sites as part of funeral practices²⁵. Accordingly, if over-harvesting occurs without proper management, it can negatively impact ecological and cultural services, ultimately affecting human well-being.

In this study, we used 10 years of data from the online market platform to reveal trade trends of land hermit crabsWe aim to analyze trends in the sale of individual crabs and prices, and to examine whether these trends align with Google Trends data. Google Trends has become one of the reliable data sources for exploring trends in wildlife trade and conservation issues (e.g., ^26–28). Additionally, we aim to identify the characteristics that impact price, such as species, color, or body size. Seasonal variations in crab sales and their sourcing locations are also important for policymakers and enforcement agencies to consider. Since land hermit crabs are protected under the law in Japan, analyzing 10 years of consistent data is vital for creating effective conservation policies. Additionally, this study offers valuable insights for developing global management strategies for invertebrates.

Research on invertebrate species, particularly their conservation status, policies, and management strategies, remains limited^29–32. Invertebrates constitute a significant proportion of the world's biodiversity and play a crucial role in global ecosystems^33,34. However, many invertebrates are becoming extinct without notice^35–37. Therefore, it is important to understand how invertebrates are used and their status in the market. This lack of information highlights the need for further investigation into the trade of these less-studied species.

Trade and Google trends over the past 10 years

Our results by the generalized linear model (GLM) indicate that from October 2013 to December 2023, there was a positive and significant increase in the monthly average number of individuals sold (p < 0.001), the average monthly total price ( p < 0.01), Google website search trends (p < 0.01), and Google image search trends (p < 0.001) (Fig. 1). This suggests a growing interest in and demand for these land hermit crabs over the past decade. Furthermore, the significant correlations among all these dimensions (p < 0.001, Pearson correlation) indicate that Google trends can effectively reflect trade trends (Fig. 1).

Influencing factors for individual prices

According to the GLM analysis, several factors influence the prices of individual crabs. Body size has a significantly positive impact on price. Using C. rugosus as the reference level, C. brevimanus and C. purpureus command significantly higher prices, while C. cavipes and mixed species are priced significantly lower than C. rugosus. Sales with fewer than 5 or more than 10 individuals are priced significantly higher or lower, respectively, compared to sales with 6 to 10 individuals. Additionally, there are no significant price differences related to season or area. Fig. 2 reveals the significance and estimated values of all the variables, and the results are detailed in Supplementary 1.

Since color is specific to certain species, color, and body size were separately analyzed by species using the comparison analysis (Supplementary 2). Regardless of the species, body size is a critical factor influencing price. However, within certain species of specific body sizes, coloration significantly affects prices. According to Supplementary 2, no general pattern was found indicating which color mainly influences prices.

The body size trends in online trade over the past ten years

By using the GLM assuming a beta distribution to analyze the size structure proportions in the online market over the past ten years, we found that the proportion of S-sized crabs has significantly increased (p < 0.01) (Fig. 3). The proportion of M-sized crabs did not show a significant change (p = 0.62) (Fig. 3). However, the proportions of both L and XL-sized crabs have significantly declined (p < 0.001, both) over the past ten years (Fig. 3).

Sale Season, Sale Proportion of Sellers, and Sellers’ Locations

In terms of selling season, the results reveal a significant difference in crab prices (p < 0.01, ANOVA). Crabs sold during the summer are significantly higher than those sold in other seasons (p < 0.05 for spring and autumn; p < 0.001 for winter, post hoc Duncan test), indicating that crabs are predominantly sold in the summer (Fig. 4A).

Regarding sellers, among 63 sellers, the top 9 accounts for 97% of the crab sales (Fig. 4B). This result indicates that a small number of sellers are responsible for the majority of crab sales. Concerning the selling location, 59.3% of the crabs were sold in packages containing mixed species. Of all the crabs, 84.6% were sourced from Okinawa, while only 15.4% came from Saitama, Aichi, Chiba, Osaka, and other areas (Fig. 4C).

Wildlife trade and Google trends

According to our study, the sale of land hermit crabs and their total price significantly increased over the past ten years, indicating a growing demand for these crabs as pets. Although individual prices did not change, the total volume sold increased, leading to a corresponding rise in total sales. Notably, data from Google Trends showed a high correlation with the number of crabs sold, both in Google search and image trends. When consumers are interested in acquiring certain pets, they simultaneously search for related information and images to verify the species' appearance. Valdez (2021) also utilized Google Trends data to assess the global popularity of the most common pets between 2004 and 2020, comparing these findings with results from an online survey distributed to individuals active in the reptile trade²⁸. However, while Valdez (2021) lacked the trade data to demonstrate that Google Trends aligned with actual trade trends, our study provides this evidence²⁸.

Therefore, search trends could serve as an indicator for future wildlife trade trends. If the search trends for a particular species increase, it may signal a rise in trade activity, whether online or in physical pet shops. We acknowledge that these trends may not be entirely accurate, as they could be influenced by other factors like news or specific events. However, our long-term data reveals a strong correlation, suggesting that search trends could be a useful index for understanding the popularity of certain species in the wildlife trade.

Notably, the trends from 2019 and 2020 showed a dramatic increase, coinciding with the COVID-19 pandemic. The pandemic was initially reported to have originated from wildlife species sold and slaughtered at a live-animal market in Wuhan, China³⁸. Due to increased discussion and awareness of human-wildlife interactions, scientists anticipated significant changes in human behavior regarding wildlife trade during the pandemic³⁹. However, Morcatty et al. (2021) noted that despite the closure of physical markets, online wildlife trade remained active and even increased during the lockdown period⁴⁰. Additionally, illegal hunting also rose during the pandemic⁴¹. Our long-term data allowed us to examine these trends during the pandemic. Our research species, being non-mammalian and not directly related to COVID-19, likely experienced a lower impact from consumer concerns about the virus. We hypothesize that the increase in trade during COVID-19 was due to lockdown boredom, prompting people to consider acquiring pets, thus increasing sales during that time.

What factors determine the price and their implications for conservation?

Understanding the value of wildlife is essential for biodiversity conservation. In conservation practice, it is important to recognize that a high price often indicates rarity and high demand, necessitating greater concern for high-priced species and individuals ^12,42. In our study, we found that C. brevimanus commands a higher price than other species and is the rarest species in the entire online land hermit crab selling database (Fig. 2). This phenomenon aligns with previous research (e.g.,^13,43), suggesting that rarity might be one of the preferences for consumers when valuing the price. However, the second and third rarest species, C. cavipes and C. violascens, were not priced as highly as C. brevimanus (Fig. 2). Thus, we believe there are other major factors determining the price in the online market for land hermit crabs.

We discovered that larger body sizes generally command higher prices, regardless of species, consistent with the observations from land hermit crab trade in Taiwan⁴⁴. Besides, within the same species and body size, the coloration of the crabs also influences the price. For example, in C. purpureus of both L and M sizes, pink individuals are the most expensive, and in C. rugosus of M size, orange and pink individuals are the most expensive (Supplementary 2). In conclusion, body size is the primary factor in determining price, but there seems to be no general pattern regarding the influence of coloration on price.

Accordingly, these results provide two significant conservation implications for land hermit crabs. First, the larger body size of females usually indicates higher fecundity for crustaceans ⁴⁵. If large individuals are in high demand and are over-exploited, the breeding capability of the population might face challenges. Our analysis also shows that the number of small (S) individuals is significantly increasing, while large (L and XL) individuals are significantly decreasing in the online market (Fig. 3), indicating a potential over-fishing situation [e.g., the crab species Hepatus pudibundus⁴⁶]. Land hermit crabs, like their relatives, coconut crabs, are long-lived and late-maturing creatures¹⁸. Coconut crabs, the only species in the Family Coenobitidae listed on the IUCN Red List with a status of Vulnerable, are estimated to live up to 100 years and reach maturity around five years old^47–49. These characteristics make such species highly susceptible to over-exploitation. Due to over-exploitation, the population of coconut crabs has decreased, leading to local extinctions in certain areas and prompting scientists to call for the cessation of their consumption⁵⁰. Therefore, we should be concerned about the overfishing of land hermit crabs, which belong to the same genus as coconut crabs.

In terms of coloration, it is unclear what mechanisms cause the diverse body coloration in land hermit crabs. For other crustaceans, factors such as food, genetics, and environment might contribute^51–53. Besides, body size may influence body coloration, with larger individuals often displaying more colorful patterns due to reduced pressure to remain cryptic from predators (e.g., ^54,55). Therefore, if people selectively catch individuals of certain colors, it could decrease genetic diversity, impact sexual selection, influence population structure, and affect other evolutionary aspects of land hermit crabs.

Season, sale proportion, and sellers’ locations

Regarding seasonal fluctuations in price, we found that crab prices do not differ significantly among seasons (Fig. 4), but the number of crabs sold was significantly higher in summer (Fig. 4A). The peak in sales during summer aligns with the land hermit crabs' active season⁵⁶. These findings highlight the impact of seasonal variations on wildlife sourcing.

Our result highlights a concerning trend where a small number of companies exert significant control over the online market for land hermit crabs (Fig. 4B). The uncertainty surrounding whether these entities possess the necessary permits raises substantial concerns about regulatory compliance and environmental sustainability. Even if permits are obtained, the management practices, including the volumes of crabs caught and sold, need to be revised. This concentration of authority over natural resources and ecosystem services underscores broader concerns regarding fair access and the equitable distribution of benefits. Given that these crabs are public goods, it is crucial that their exploitation benefits local communities and aligns with broader societal interests. This necessitates the implementation of thoughtful governance and management strategies to ensure sustainable and equitable outcomes for all stakeholders involved.

Furthermore, most of the land hermit crab trading originates from the sellers in Okinawa, the primary habitat of these crabs. Past reports indicate that crabs were sold by tons annually during the 1975-1984 period²⁵. Although the Japanese government issued permits to some fishermen to legally catch these crabs in the past, such permits are no longer being issued and are now rare. This scarcity increases the likelihood of illegal catching and sales directly from Okinawa. Therefore, collaborating with local communities is imperative for combating illegal wildlife trade and ensuring effective enforcement. Enforcement efforts and community engagement can and should complement each other⁵⁷. Last year, some smuggling (i.e., ⁵⁸) attempts were thwarted thanks to local residents who identified suspicious individuals and activities and reported them to the authorities.

Management implicaiton

Based on our ten-year analysis of online marketing data for land hermit crabs, we present several key management implications. Firstly, although all land hermit crab species are protected in Japan, it remains unclear whether all captured individuals are taken by those with valid licenses, similar to other protected species that require specific permits for catching or selling, such as those listed in CITES⁵⁹. Authorities should re-evaluate the regulations for catching and selling these crabs. Although only a small number of individuals hold legal permits for crab collection, the volumes sold continue to rise, suggesting a potential gray area for illegal activities. Additionally, trade data often underrepresents annual volumes due to unrecorded mortality between harvest and final destination⁶⁰.

Despite declining populations and fewer large individuals, proper management can aid in recovery. Policymakers should implement regulations that restrict catching crabs of certain sizes, prohibit catching ovigerous females, and regulate annual volumes for certified industries. Further research is required to determine specific size ranges and allowable volumes. Immediate action is crucial to prevent the population from declining to a critical level, potentially causing irreversible bottleneck effects.

The highest selling volumes occur in the summer, which coincides with the crabs' active season. Therefore, enforcement and monitoring during this period are essential to prevent illegal catching. Strengthening connections with local communities, such as through citizen science projects, can help protect natural resources, monitor crab populations, provide valuable data for policymaking, and engage the public in scientific research^61,62.

Regarding smuggling, our data revealed naturally distributed species in the online market, indicating the possibility of domestic smuggling in the islands of Okinawa and Amami. Land hermit crabs are small and cold-blooded, making smuggling detection challenging ⁴. Numerous smuggling incidents involve foreigners attempting to traffic land hermit crabs from Japan⁵⁸. As exotic pets, land hermit crabs—particularly C. purpureus, which has a relatively small distribution limited to Japan region⁶³—are becoming increasingly popular worldwide and are prime targets for poaching⁴⁴. Current penalties are insufficient deterrents due to the high profits involved⁶⁴. Therefore, advancing enforcement technology and updating regulations are imperative for the future conservation of these invertebrates.

Limitation

First, we acknowledge that our analysis, based on a single dataset, likely underestimates the volume of land hermit crab sales in Japan. Relying solely on online data repositories rather than obtaining direct empirical evidence carries a substantial risk of misunderstanding the impacts of harvesting on dynamic populations of wild species ^8,65. Future research should include data from physical pet shops and other platforms to comprehensively understand the full scope of land hermit crab trading in Japan or worldwide. Additionally, field studies of land hermit crab populations would be valuable for a more thorough understanding of their conservation status.

Despite its limitations, our study's advantage lies in focusing on the largest platform, ensuring more consistent data than if multiple sources were used. Furthermore, this platform provides ten years of data, allowing us to analyze long-term trends and price fluctuations. This approach offers more objective insights into the decade-long trend of online trade in Japan.

Second, we acknowledge that our visual methods for measuring body size and color might introduce certain biases. However, if our visual measurements were significantly biased and unable to categorize body size accurately, no significant differences would be observed. The good news is that many of our analyses based on these categories show significant differences (e.g., body size vs. price), indicating that our visual categorizations are reliable. Although we rely on only two people (one for measurement and one for double-checking), we recognize that this method may introduce systematic biases.

Third, we acknowledge that we cannot judge the legality of all sales. Moreover, we should clarify that legality does not equate to sustainable trade, and vice versa. Based solely on wildlife trade data, we lack the population data of land hermit crabs needed to assess whether the trade is sustainable. Further research is necessary to understand the full picture of land hermit crab conservation in Japan and globally.

In conclusion, our study highlights a significant rise in the sale of land hermit crabs over the past decade, driven by growing consumer demand for these pets. Despite external factors such as the COVID-19 pandemic impacting wildlife trade dynamics, our research indicates sustained demand and sales in online markets. We found strong correlations between Google search and image trends with sales data, suggesting search trends could predict future trade activity. Understanding these trends provides valuable insights into consumer behavior and the dynamics of the wildlife trade market.

Moreover, our study reveals significant factors influencing land hermit crab market dynamics, with direct implications for conservation efforts. Preferences for larger crabs and specific colors, like pink, suggest consumer-driven selection pressures that could harm population sustainability. Over-exploitation of larger individuals threatens population health, as evidenced by declining numbers of large crabs and an increase in smaller ones in markets. Seasonal price fluctuations reflect market influences, with winter peaks and summer sales patterns mirroring natural activity cycles. Conservation strategies must therefore focus on reducing over-exploitation, protecting reproductive individuals, and preserving genetic diversity.

Our analysis of ten years of online land hermit crab sales data underscores the need for revised policies and enhanced enforcement to ensure sustainability. Legal protections must be rigorously enforced, with stricter oversight of permit issuance and trade volumes. Regulations should include size limits, bans on harvesting ovigerous females, and annual quotas for licensed industries. Strengthening community involvement through citizen science initiatives can bolster conservation efforts and provide critical data for informed decision-making. Addressing smuggling through improved detection and updated regulations is essential to safeguard these species from exploitation while balancing economic interests with long-term conservation goals.

Background

Only a few countries, such as Australia, Bermuda, and Japan, have management strategies for the land hermit crab trade⁴⁴. In Japan, land hermit crabs are designated as natural monuments and protected under national regulations. Many local governments, including those in Okinawa and Kagoshima prefectures, have also issued local regulations to protect these crabs. However, a gray area exists because, many years ago, the Japanese government allowed some fishermen to catch and sell land hermit crabs with certificates legally. Nowadays, the government no longer issues new certificates, and very few people still have the authority to sell these crabs. Thus, we aim to understand the complete picture of the land hermit crab wildlife trade in the online market over the past 10 years and provide conservation management implications.

Data collation and compilation

We extracted information using the term “オカヤドカリ (land hermit crab)” from Aucfan, which collects all selling information from the largest online trading platform in Japan Yahoo Auction, including date, price, picture, sellers’ ID, number of individuals, and delivery location. The data period spans from October 1, 2013, to December 31, 2023. In total, we gathered 5,377 sales related to land hermit crabs. After researchers reviewed the sales, we excluded 2,866 items that were not land hermit crabs but rather accessories such as sand, plants, and shells. Additionally, 68 set selling sales, which included crabs along with other items like boxes, shells, and crab food, were excluded from the analysis because the inclusion of other goods could affect the individual price of the crabs. One sale mentioned by sellers had a damaged leg, so it was also excluded as it might influence the crabs’ price. We also identified 290 sales with a final price of 1 JPY, indicating reputation laundering. Some sellers used “internal trade” to boost their online shop's reputation and trading record; these sales were excluded from our analysis as well. Eventually, 2,152 sales remained. The data compilation framework is in Fig. 5 A.

After cleaning the data, we manually checked the selling photos of each sale to identify the crabs’ species, body size, and color. The first author of this paper is an expert in land hermit crab ecology, having measured thousands of crabs in the wild, which ensures reliable species identification, body size measurement, and color recognition. Drawing on his experience in measuring body size and referencing standards (such as bottles or rulers) in sales photos, we were able to obtain rough body size estimation data. We followed^56,66, using shield length as an indicator of land hermit crab’s body size (Fig. 5 BS). If the shield length is approximately 0-0.5 cm, the size is classified as S; 0.5-1 cm as M; 1-1.5 cm as L; over 1.5 cm as XL; and the body size mixing package as Mix.

The crabs' coloration was classified based on the predominant color of their bodies. We identified 11 coloration categories from 5 species of crabs: deep purple (DP), deep blue (DB), light purple (LP), light blue (LB), brown (B), gray (G), green (GN), orange (O), pink (P), red (R), white (W), and color mixing packages (M). Besides, each sale title indicated the number of individuals sold, and we recorded these data. Finally, the 2,152 transactions contained 6,828 land hermit crab individuals across five species—namely, C. brevimanus, C. cavipes, C. purpureus, C. rugosus, and C. violascens—or mixed species sales, with a total price of 29,067.6 USD over 10 years (exchange rate averaged 112.63 JPY per 1 USD from 2013 to 2023) (Fig. 5 B~V). The division of sales and individuals by species, along with the totals, is presented in Supplementary 3.

Data analysis: Trade and attention trends

We explored the trade trends of sold individuals and prices by calculating the yearly averages and standard deviations of the total monthly individual sales and prices. Identifying trends involved performing a linear regression analysis on the monthly average number of crabs sold and the total monthly average price over ten years to determine if there was a significant increase.

The attention trends of land hermit crabs were assessed using Google Trends data. We searched for the category "オカヤドカリ" (land hermit crabs in Japanese) from October 1, 2013, to December 31, 2023, corresponding to the period covered in our trade data analyses. The search was limited to Japan. Google search trends were divided into web search and image search categories, based on the hypothesis that individuals interested in owning a pet might search for care information online and use image searches to see what different species look like. Google Trends data represent search interest relative to the highest point on the chart for the given region and time, with a value of 100 indicating peak popularity, a value of 50 indicating half as popular, and a score of 0 indicating insufficient data. Monthly data were used to calculate yearly averages and standard deviations, followed by GLM with a Poisson distribution to determine if the trends showed a significant increase.

The correlation between trading trends and Google trends was examined using Pearson correlation analysis to determine if there were significant correlations among the individual number of crabs sold, total price, Google web search trend, and Google image search trend.

Data analysis: The influence factors for the individual price of land hermit crab

We employed GLM to analyze the factors influencing individual crab prices. A log link function was used in the GLM to address the non-normal distribution of the data. In our model, the response variable is the price of an individual crab, while the explanatory variables include year, body size, species, number of individuals sold per sale, season, and the source area of the crabs. The GLM variable definitions are provided below.

Variables:

Price: The individual price, is calculated by dividing the total price of the sale by the number of individuals in the sale.
Year: The year of the online dataset, ranging from 2013 to 2023.
Size: The body size, is considered as continuous data (e.g., S = 1, XL = 4).
Species: The species in online trade: B ( brevimanus), C (C. cavipes), P (C. purpureus), V (C. violascens), and Mix (mixed species in one sale). R (C. rugosus) is used as the reference level.
Number: The number of crabs in one sale. ≤ 5 indicates a sale with five or fewer individuals, and ≥11 indicates a sale with eleven or more individuals. Sales with 6 to 10 individuals are used as the reference level.
Season: The season of the sales. March to May is spring, June to August is summer, September to November is autumn, and December to February is winter. Summer is used as the reference level in the model.
Area: The selling source area. The top five seller areas in this model are Okinawa, Saitama, Aichi, Chiba, and Osaka. Other areas are combined into "Others." Okinawa is used as the reference level in the model.

We did not include coloration in the GLM analysis because we found that coloration is highly related to specific species, which led to non-random data and restricted the application of GLM. Instead, we divided the data into subsets and used the Kruskal-Wallis Rank Sum Test to analyze the significance of price, species, body size, and coloration. If significant differences were found among the subsets, we used Dunn’s test to conduct pairwise comparisons of the prices based on coloration within a subset and body size within a species. Notably, Dunn’s test has some limitations, such as requiring a sample size larger than three, so we excluded groups with fewer than three samples from the comparison analysis. The results are provided in Supplementary 2.

Data analysis: Body size structure of annual change over the past 10 years

To understand the body size structure of land hermit crabs in online trade over the past 10 years, we analyzed the proportions of body size categories annually. Since all five species in the study can grow to XL size and some species are relatively less common in the online market, we did not separate the species to analyze body size structure. This approach allows us to observe overall trends in body size structure over the past decade. Additionally, since the data for 2013 only covered three months, we excluded 2013 from this analysis. Finally, we used the GLM assuming a beta distribution to assess the positive or negative trends of each size category over the 10 years.

Seasonal sales volumes, sellers' sales proportion, and sellers' locations

We categorized the selling time into four seasons (using the same date periods as in the GLM). However, unlike the GLM, which analyzes price, we focused on the seasonal variation in the number of crabs sold. Since the data for each season followed a normal distribution (p > 0.05 for all seasons, Shapiro-Wilk normality test), we used ANOVA to analyze seasonal differences. If ANOVA revealed significant differences, we applied Duncan's Multiple Range Test to determine the differences among seasons.

We used a lollipop chart for descriptive statistics to assess the sellers' contributions to the proportion of individuals sold over the past 10 years. For the sellers' locations, we employed a Sankey plot to illustrate the relationship between species and sellers’ areas, with areas defined by prefectures.

All statistical analyses and visualizations in the Methods and Materials section were performed using R software⁶⁷.

Competing interests

All authors declare no financial or non-financial competing interests.

Author Contribution

Hsu: Conceptualization, Methodology, Formal analysis, Investigation, Data Curation, Writing - Original Draft, Writing - Review & Editing, Visualization. Kang: Methodology, Software, Formal analysis, Data Curation, Visualization. Zhao: Conceptualization, Software, Investigation, Data Curation. Uryu: Methodology, Software, Validation. Imagawa: ValidationEndo: Validation. Kubo: Conceptualization, Validation, Resources, Data Curation, Supervision, Project administration, Funding acquisition.

Morton, O., Scheffers, B. R., Haugaasen, T. & Edwards, D. P. Impacts of wildlife trade on terrestrial biodiversity. Nat Ecol Evol 5, 540–548 (2021).
Hutton, J. M. & Leader-Williams, N. Sustainable use and incentive-driven conservation: realigning human and conservation interests. Oryx 37, 215–226 (2003).
Kasterine, A. & Lichtenstein, G. Trade in vicuña: the implications for conservation and rural livelihoods. Geneva, Switzerland: International Trade Centre (2018).
Fukushima, C. S. et al. Challenges and perspectives on tackling illegal or unsustainable wildlife trade. Biol. Conserv. 263, 109342 (2021).
Cardoso, P. et al. Scientists’ warning to humanity on illegal or unsustainable wildlife trade. Biol. Conserv. 263, 109341 (2021).
Challender, D. W. S. et al. Mischaracterizing wildlife trade and its impacts may mislead policy processes. Conserv. Lett. 15, (2022).
Luiselli, L., Bonnet, X., Rocco, M. & Amori, G. Conservation implications of rapid shifts in the trade of wild African and Asian pythons. Biotropica 44, 569–573 (2012).
Natusch, D. J. D., Aust, P. W. & Shine, R. The perils of flawed science in wildlife trade literature. Conserv. Biol. 35, 1396–1404 (2021).
Lavorgna, A. Wildlife trafficking in the Internet age. Crime Science 3, 5 (2014).
Stringham, O. C. et al. A guide to using the internet to monitor and quantify the wildlife trade. Conserv. Biol. 35, 1130–1139 (2021).
Hall, R. J. & Milner-Gulland, E. J. Endangering the endangered: the effects of perceived rarity on species exploitation. Conservation Letters (2008) doi:10.1111/j.1755-263X.2008.00013.x.
Courchamp, F. et al. Rarity value and species extinction: the anthropogenic Allee effect. PLoS Biol. 4, e415 (2006).
Krishna, V. V. et al. Wildlife trade and consumer preference for species rarity: an examination of caged-bird markets in Sumatra. Environ. Dev. Econ. 24, 339–360 (2019).
Tournant, P., Joseph, L., Goka, K. & Courchamp, F. The rarity and overexploitation paradox: stag beetle collections in Japan. Biodivers. Conserv. 21, 1425–1440 (2012).
Slone, T. H., Orsak, L. J. & Malver, O. A comparison of price, rarity and cost of butterfly specimens: Implications for the insect trade and for habitat conservation. Ecol. Econ. 21, 77–85 (1997).
Sung, Y.-H. & Fong, J. J. Assessing consumer trends and illegal activity by monitoring the online wildlife trade. Biol. Conserv. 227, 219–225 (2018).
Faulkes, Z. The global trade in crayfish as pets. Crustac. Res. 44, 75–92 (2015).
Liu, S.-S., Fang, W.-T. & Hsu, C.-H. Filling the knowledge gap in the reproductive biology of land hermit crabs (Decapoda: Anomura: Coenobitidae): captive breeding to explore incubation times and frequency. J. Crustacean Biol. 41, ruab056 (2021).
Bundhitwongrut, T. Unregulated trade in land hermit crabs in Thailand. Nat. Hist. Bull. Siam Soc. 63, 27–40 (2018).
Hsu, C.-H. & Choi, S.-T. The paradise of Coenobita brevimanus-Dongji Island, Taiwan. Nature Conservation Quarterly (2016).
Bennett-Vaz, R. M., Arauz, G., Vega-Rovira, Y. A. & Gálvez, D. Ants vs crabs: competition over seeds on a tropical island ecosystem. Arthropod Plant Interact. 18, 493–499 (2024).
Alexander, H. G. L., Stoddart, D. R. & Westoll, T. S. A preliminary assessment of the role of the terrestrial decapod crustaceans in the Aldabran ecosystem. Philos. Trans. R. Soc. Lond. B Biol. Sci. 286, 241–246 (1997).
Huang, S.-H. & Hsu, C.-H. First record of crab-eating mongoose (Herpestes urva formosanus) in coastal forest and use of anvils during predation on land hermit crabs in Taiwan. Acta Ethol. 25, 185–189 (2022).
Hsu, C.-H. et al. Utilizing Local Residents’ Social-ecological Memories as References for Biodiversity Restoration and Conservation Action. (2024) doi:10.31219/osf.io/z9sw7.
Okinawa Prefecture. Amam: Report on the Actual Condition of Land Hermit Crab Habitat. vol. 29 (Ryokurindo, 1987).
Troumbis, A. Y. Google Trends and cycles of public interest in biodiversity: the animal spirits effect. Biodivers. Conserv. 26, 3421–3443 (2017).
Burivalova, Z., Butler, R. A. & Wilcove, D. S. Analyzing Google search data to debunk myths about the public’s interest in conservation. Front. Ecol. Environ. 16, 509–514 (2018).
Valdez, J. W. Using Google Trends to Determine Current, Past, and Future Trends in the Reptile Pet Trade. Animals (Basel) 11, (2021).
Cardoso, P., Erwin, T. L., Borges, P. A. V. & New, Tim R. The seven impediments in invertebrate conservation and how to overcome them. Biol. Conserv. 144, 2647–2655 (2011).
Scheffers, B. R., Oliveira, B. F., Lamb, I. & Edwards, D. P. Global wildlife trade across the tree of life. Science 366, 71–76 (2019).
Eisenhauer, N., Bonn, A. & A Guerra, C. Recognizing the quiet extinction of invertebrates. Nat. Commun. 10, 50 (2019).
Cardoso, P., Borges, P. A. V., Triantis, K. A., Ferrández, M. A. & Martín, J. L. Adapting the IUCN Red List criteria for invertebrates. Biol. Conserv. 144, 2432–2440 (2011).
Wilson, E. O. The Little Things That Run the World (The Importance and Conservation of Invertebrates). Conserv. Biol. 1, 344–346 (1987).
Prather, C. M. et al. Invertebrates, ecosystem services and climate change. Biol. Rev. Camb. Philos. Soc. 88, 327–348 (2013).
Régnier, C., Fontaine, B. & Bouchet, P. Not knowing, not recording, not listing: numerous unnoticed mollusk extinctions. Conserv. Biol. 23, 1214–1221 (2009).
Dunn, R. R. Modern insect extinctions, the neglected majority. Conserv. Biol. 19, 1030–1036 (2005).
Black, S., Shepard, M. & Allen, M. Endangered Invertebrates: the case for greater attention to invertebrate conservation. Endanger. Species Res. (2001).
Chen, N. et al. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. Lancet 395, 507–513 (2020).
Moorhouse, T. P., D’Cruze, N. C. & Macdonald, D. W. The Pandemic as a Conservation Marketing Intervention: Could COVID-19 Lower Global Demand for Wildlife Products? Frontiers in Ecology and Evolution 9, (2021).
Morcatty, T. Q., Feddema, K., Nekaris, K. A. I. & Nijman, V. Online trade in wildlife and the lack of response to COVID-19. Environ. Res. 193, 110439 (2021).
McNamara, J. et al. COVID-19, Systemic Crisis, and Possible Implications for the Wild Meat Trade in Sub-Saharan Africa. Environ. Resour. Econ. 76, 1045–1066 (2020).
Holden, M. H. & McDonald-Madden, E. High prices for rare species can drive large populations extinct: the anthropogenic Allee effect revisited. J. Theor. Biol. 429, 170–180 (2017).
Lyons, J. A. & Natusch, D. J. D. Effects of consumer preferences for rarity on the harvest of wild populations within a species. Ecol. Econ. 93, 278–283 (2013).
Hsu, C.-H. et al. Exploring Interdisciplinary Aspects for Conservation Management: The Case of Land Hermit Crab Wildlife Trade in Taiwan. (2024) doi:10.31235/osf.io/xpjmr.
Somers, K. Characterizing size-specific fecundity in crustaceans. Crustacean egg production 357–378 (2020).
Teles, J. N., Mantelatto, F. L., Miazaki, L. F., Fransozo, A. & Bertini, G. A 20-year gap evaluation of the population biology of the crab Hepatus pudibundus in an area overexploited by fisheries. Biologia 76, 147–158 (2021).
Cumberlidge, N. et al. Troubled giants: The updated conservation status of the coconut crab (Birgus latro). Raffles Bull. Zool. 70, (2022).
Drew, M. M., Smith, M. J. & Hansson, B. S. Factors influencing growth of giant terrestrial robber crab Birgus latro (Anomura: Coenobitidae) on Christmas Island. Aquat. Biol. 19, 129–141 (2013).
Schiller, C., Fielder, D. R. & Brown, I. W. Reproduction, early life-history and recruitment. The coconut crab (1991).
Hsu, C.-H. Stop eating the largest land-dwelling marine creatures. Zoo’s Print 36, 3–5 (2021).
Jones, P. L., De Silva, S. S. & Mitchell, B. D. The effect of dietary protein source on growth and carcass composition in juvenile Australian freshwater crayfish. Aquac. Int. 4, 361–376 (1996).
Zhang, D. et al. The comparison of morphology and transcriptome in the inner membrane reveals the potential mechanism of the heritable carapace color of the Chinese mitten crab Eriocheir sinensis. Gene 897, 148058 (2024).
Nokelainen, O., Hubbard, N., Lown, A. E., Wood, L. E. & Stevens, M. Through predators’ eyes: phenotype–environment associations in shore crab coloration at different spatial scales. Biol. J. Linn. Soc. Lond. 122, 738–751 (2017).
Yoshikawa, A. et al. Colour variation of the intertidal hermit crab Clibanarius virescens considering growth stage, geographic area in the Indo–West Pacific Ocean, and molecular phylogeny. J. Mar. Biol. Assoc. U. K. 100, 1107–1121 (2020).
João, M. C. A., Duarte, R. C., Freire, A. S. & Pinheiro, M. A. A. Intraspecific color diversity and camouflage associated with ontogeny in an insular land crab. Behav. Ecol. Sociobiol. 77, 120 (2023).
Hsu, C.-H., Otte, M. L., Liu, C.-C., Chou, J.-Y. & Fang, W.-T. What are the sympatric mechanisms for three species of terrestrial hermit crab (Coenobita rugosus, C. brevimanus, and C. cavipes) in coastal forests? PLoS One 13, e0207640 (2018).
Cooney, R., Roe, D. & Dublin, H. Wildlife, wild livelihoods: Involving communities in sustainable wildlife management and combatting the illegal wildlife Trade. Combating illegal Wildlife (2018).
Hsu, C.-H. et al. Highlighting the urgency of conservation strategies for land hermit crabs in the light of current incidents. Crustaceana 96, 1191–1194 (2023).
Nijman, V. An overview of international wildlife trade from Southeast Asia. Biodivers. Conserv. 19, 1101–1114 (2010).
Auliya, M. et al. Trade in live reptiles, its impact on wild populations, and the role of the European market. Biol. Conserv. 204, 103–119 (2016).
Hsu, C.-H., Chang, Y.-M. & Liu, C.-C. Can Short-Term Citizen Science Training Increase Knowledge, Improve Attitudes, and Change Behavior to Protect Land Crabs? Sustainability 11, 3918 (2019).
Hsu, C.-H., Fang, W.-T., Chiu, H.-K., Jiang, B.-R. & Huang, T.-S. Coastal citizen science monitoring and suggested conservation strategy: ghost crab survey at Suao Dakenggu, Taiwan. J. Coast. Conserv. 28, (2024).
Hamasaki, K., Iizuka, C., Sanda, T., Imai, H. & Kitada, S. Phylogeny and phylogeography of the land hermit crabCoenobita purpureus(Decapoda: Anomura: Coenobitidae) in the Northwestern Pacific Region. Mar. Ecol. 38, e12369 (2017).
Hsu, C.-H. An update on the incident involving illegal catching of land hermit crabs in Okinawa, Japan. Crustaceana 97, 159–160 (2024).
Hughes, A. et al. Determining the sustainability of legal wildlife trade. J. Environ. Manage. 341, 117987 (2023).
Hsu, C.-H. & Soong, K. Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan. PLoS One 12, e0174319 (2017).
R Core Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/ (2022).

No competing interests reported.

Download PDF

Version 1

posted

You are reading this latest preprint version

Inconspicuous Hermit? Conservation Management Implications from a Decade of Online Wildlife Trade Trends for Land Hermit Crabs

Status:

Version 1

Abstract

Figures

Introduction

Results

Discussion

Conclusion

Methods

Declarations

Competing interests

Author Contribution

References

Additional Declarations

Supplementary Files

Status:

Version 1