The pet trade and Traditional Chinese Medicine (TCM) consumption are major drivers of global biodiversity loss. Tokay geckos (Gekko gecko) are among the most traded reptile species worldwide. In Hong Kong, pet and TCM markets sell tokay geckos while wild populations also persist. To clarify connections between trade sources and destinations, we compared genetics and stable isotopes of wild tokays in local and nonlocal populations to dried individuals from TCM markets across Hong Kong. We found that TCM tokays are likely not of local origin. Most wild tokays were related to individuals in South China, indicating a probable natural origin. However, two populations contained individuals more similar to distant populations, indicating pet trade origins. Our results highlight the complexity of wildlife trade impacts within trade hubs. Such trade dynamics complicate local legal regulation when endangered species are protected, but the same species might also be non-native and possibly damaging to the environment.

Sampling Design

Both G. gecko gecko and G. gecko reevesii seem to occur in different areas of Hong Kong, with two main populations described on Lantau Island and Lion Rock Country Park, and smaller populations possibly established through intentional or unintentional release from the pet trade [23]. We surveyed seven field sites across Hong Kong for which the presence of tokay geckos was known, between August and November 2020. Precise locations are kept confidential to limit risks of poaching [27]. We caught geckos by hand or butterfly net. Upon capture, we collected morphological information on snout-vent length (SVL), total length (TL), sex, morph (red- vs. black-spotted), and mass. We took pictures of ventral and dorsal sides with a uniform background for further reference. We collected a small tail clipping (~0.5cm) from each animal, half stored in 70% ethanol (for genetic study) and half in an empty tube (for stable isotope analysis). As the tail is capable of regeneration this was deemed the least invasive method for this study [28]. For dried specimens, we purchased 19 pairs of dried tokay geckos (Figure S1) allegedly originating from China, Thailand, and Vietnam from 18 shops in Hong Kong (Table S1). All shops were given an identification letter to preserve anonymity. We also obtained shed skins from two pet tokays that had been in captivity more than 1.5 years, from volunteer pet owners. The two pet owners mentioned that the tokay geckos they purchased from local pet shops were allegedly sold as “wild”. Additionally, we received the corpse of one wild individual, found dead in Lantau Island. 

Stable Isotope Analysis

We used stable isotope analyses (SIA) to infer breeding conditions and/or geographic origin of TCM geckos. We compared δ¹⁵N and δ¹³C from tail samples from wild-caught and TCM geckos. We selected tail tissue as it has a lower turnover in isotopic ratios compared to other tissues in lizards and therefore represents better the long-term diet. SIA has previously been used on a wide range of animals, including reptiles, to differentiate diet between different breeding conditions (captive, semi-captive, or wild) based on differences in the ratios of heavy to light isotopes of C and N in their diet (δ¹³C and δ¹⁵N). Here, we studied the potential overlap between the diet of TCM shops and HK wild-caught tokay geckos.

For SIA, 0.5cm of the tip of the tail of the wild and TCM shop individuals was dried at 60°C in a chamber for 24 hours minimum and subsequently cut into small aliquots of ~1mg (1.35±0.12 mg) and loaded into tin capsules. Analysis was conducted using an EA-IRMS (Eurovector 3028-Nu Instruments Perspective IRMS) at the Stable Isotope Ratio Mass Spectrometry (SIRMS) Laboratory at HKU, using a certified standard (Indiana University acetanilide, (δ¹³C = −29.53 ‰, δ¹⁵N = +1.18 ‰) to correct the resulting sample values. Results were reported as a ratio to the reference values from Hong Kong and expressed in δ units in the conventional permil notation, where δ = [(R_sample/R_standard)−1]×1000. 

Shop Surveys

We visited 18 registered TCM shops on three different days between February and April 2021 in three main districts of Hong Kong (Sham Shui Po, Sheung Wan, and Yau Ma Tei) and carried out nine interviews in Cantonese. Questionnaires were composed of a series of open- and closed-ended questions (Table S2; adapted from Landry Yuan et al.), around several main themes: background on the shop, consumption of geckos, origin of the products and import, and trends. Interviews were conducted by the same interviewers in Cantonese following a semi-structural oral format. Answers from interviewees were written down and later translated into English for further analysis. Each interviewee gave consent and was offered the option to skip any question he or she was not comfortable answering. Surveys were later anonymized.

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