Herpetology Notes, volume 14: 309-315 (2021) (published online on 09 February 2021)

Checking back two centuries: a key criterion to identify the wolfsnake, Lycodon aulicus (Linnaeus, 1758), in the Mascarene Islands

Gernot Vogel1, Jean-Michel Probst2, Grégory Deso3, Oliver Hawlitschek4, Nik Cole5, F. B. Vincent Florens6, and Nicolas Dubos7,*

Abstract. The wolfsnake of the genus Lycodon present in the Mascarene Islands has recently been referred to as L. capucinus in the literature, but this identification has never been formally confirmed by any morphological study. The taxonomy of the genus Lycodon is poorly resolved, and recent photographs suggest that this identification may be erroneous. Using a comparative table of the distinguishing characteristics of L. aulicus and L. capucinus, we clarify the identity of 19 historical specimens collected in the Mascarenes during the 19th and 20th centuries based on colouration patterns. We show that the species present in Réunion and Mauritius should be referred to as L. aulicus. We highlight the importance of specimens from natural history collections in resolving taxonomic questions, especially regarding the identity of introduced species.

Keywords. Lycodon capucinus, Mauritius, Morphology, Museum specimens, Réunion, Western Indian Ocean

Introduction 2019). Consequently, alien reptiles are often detected several years after their introduction (Cheke, 1987; Deso The introduction of small reptile species is generally et al., 2020) and their exact origins remain uncertain. non-intentional, except for species used as pets (e.g., The case of Lycodon aulicus and its introduction to the Phelsuma grandis; Dubos, 2013; Fieldsend and Krysko, Mascarene islands of Réunion and Mauritius provides a good example of such a knowledge gap. Multiple scenarios were proposed a posteriori in an attempt to elucidate the possible pathways this species could have 1 Society for Southeast Asian Herpetology, Im Sand 3, 69115 used to reach the Mascarenes (Probst, 1993; Cheke and Heidelberg, Germany. 2 Association Nature and Patrimoine, 1 rue des Amarantes, Hume, 2008). Résidence Valeriane 2, Bat C, Appartement 15, 97490 Sainte Snakes of the genus Lycodon Boie, 1826 are non- Clotilde, Île de La Réunion, France. venomous, oviparous, nocturnal snakes inhabiting 3 Association Herpétologique de Provence Alpes Méditerranée, large parts of Asia (David and Vogel, 1996; Vogel et al., Maison des Associations, 384 route de Caderousse, F-84100 2009; Uetz et al., 2020). They usually feed on lizards but Orange, France. also small mammals. Nineteen species of Lycodon are 4 Centrum für Naturkunde, Universität Hamburg, Martin-Luther- currently known from the Indian subcontinent (Daniel, King-Platz 3, 20146 Hamburg, Germany. 5 Durrell Wildlife Conservation Trust, Les Augrès Manor, Trinity, 2002; Whitaker and Captain, 2008; Uetz et al., 2020), Jersey JE3 5BP, United Kingdom; and Mauritian Wildlife and whereas some of these species are quite common Foundation, Grannum Road, Vacoas, Mauritius. (e.g., L. aulicus), others are rare and have extremely 6 University of Mauritius – Tropical Island Biodiversity, Ecology limited distributions (e.g., L. gammiei Blanford, and Conservation Pole of Research, Réduit, 80837, Mauritius. 1878, L. deccanensis Ganesh et al., 2020). Species of 7 Centre d’Ecologie et des Sciences de la Conservation (UMR this genus are often found in degraded habitats close 7204), Sorbonne Université, Muséum National d’Histoire to human settlements, hidden under wood piles or in Naturelle, 55 rue Buffon, 75005 Paris, France; and Institut National de Recherche pour l’Agriculture et l’Alimentation et crevices of walls, and are frequently encountered in l’Environnement, Territoires, Environnement, Télédétection houses and on roofs (David and Vogel, 1996). et Information Spatiale, Maison de la Télédétection, 500 Rue Jean François Breton, 34090 Montpellier, France. Plausible Colonisation History of Lycodon aulicus * Corresponding author. E-mail: [email protected] The very first mention of a wolfsnakeL. ( aulicum, © 2021 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0. now L. aulicus) in the Mascarenes was by Duméril et al. 310 Gernot Vogel et al.

(1854:376). The authors, who received specimens from and Vogel, 2018). This provides an opportunity for a Réunion in 1839, wrote: “Les individus que le Muséum a formal identification of the species present on Réunion reçus de cette colonie y ont été recueillis par MM. Louis and Mauritius, and for clarifying the taxonomy of Rousseau8 et Pervillez.” [The specimens received by the wolfsnake species in the Mascarenes, which has yet to museum from this colony were collected there by Mssrs. be assessed. The Lycodon species in the Mascarenes is Louis Rousseau and Pervillez.] In a footnote to their considered an invasive alien predator of endemic reptiles earlier remark, Duméril et al. (1854) stated that accounts (Cheke and Hume, 2008), which makes the clarification made by the inhabitants of Réunion documented the of its identity particularly desirable. In this study we great abundance of wolfsnakes and their possible arrival examined preserved specimens collected in both islands from India with shipments of rice around 1830 (Cheke, during the 19th and 20th centuries to formally determine 1987). The species was also described as abundant a few which species were present during these time periods. years later by Louis Maillard (1862). It probably reached Mauritius in 1879 according to Daruty de Grandpré Materials and Methods (1883:144), who reported a specimen9 and stated that the Study region. The Mascarene Archipelago includes species may have been established for some time since three main islands, Reunion, Mauritius, and Rodrigues its putative introduction from the flourishing coastal in the western Indian Ocean). This study focuses on settlements of southern India. Réunion (centred on 21.13°S, 55.53°E; surface area 2512 km²), around 700 km east of Madagascar, and on The ‘Emergence’ of L. capucinus in the Mascarenes Mauritius (centred on 20.30°S, 57.58°E; surface area The subspecies L. aulicus capucinus (now elevated 1865 km²), around 200 km northeast of Reunion (Fig. 1). to L. capucinus Boie, 1827) was first reported from At the time of the first snake introductions, Réunion was Mauritius by Austin et al. (2009). Lycodon capucinus called “Île Bourbon” and Mauritius was called “Île de was then mentioned in regional articles and in France” (Bernardin de St Pierre, 1773; Lougnon, 1992). syntheses (Hawlitschek et al., 2011; Cole and Payne, Museum specimens. We examined 15 Lycodon 2015; Mauritian Wildlife Foundation, 2015), which specimens from the collections housed in the Muséum probably led to the integration of L. capucinus into the National d’Histoire Naturelle, Paris, France (MNHN), herpetological checklists of the Mascarenes. Indeed, one from the Museum für Naturkunde, Berlin, further findings of Lycodon individuals in this region Germany (ZMB), and three from the Zoologisches were assigned to L. capucinus (see O’Shea et al., 2018). Forschungsmuseum Alexander Koenig, Bonn, Germany Nevertheless, other authors continued to report the (ZFMK). Eight of these were collected on Réunion and presence of L. aulicus (Bour and Moutou, 1982; Deso eight in Mauritius between 1864 and 1988, whereas and Probst, 2007; Bissessur and Probst, 2018). To date, the collection date of the remaining single specimen there is no evidence that two distinct wolfsnake species occur in sympatry in the Mascarenes. The taxonomy of L. aulicus and L. capucinus has been debated (Lanza, 1999; Siler et al., 2013), and because of their 9 The original text reads: “M. Bewsher vous a présenté un identification criteria, individuals of these species have petit serpent qui semble se propager depuis quelque been variably referred to either as L. aulicus, L. a. temps, c’est le Prœpeditus linéatus, tout-à-fait inoffensif d’ailleurs.” [Monsieur Bewsher introduced you to a small capucinus, or L. capucinus (O’Shea et al., 2018). snake which seems to have been spreading for some time, The taxonomy of L. aulicus and L. capucinus has it is the Prœpeditus lineatus, which is also quite harmless.] recently been reassessed, clarifying the identification It appears that Daruty de Grandpré may have mistaken the criteria and allowing the two species to be distinguished wolfsnake specimen collected by the British naturalist and from each other (Vogel and Harikrishnan, 2013; Ganesh Mauritius resident Charles Edward Bewsher (1839–1890) for Praepeditus lineatus Duméril & Bibron, 1839, a nearly legless lizard now known as Lerista praepedita (Boulenger, 1887). Bewsher was an influential person in colonial Mauritius, and his activities are documented by mentions \8 Louis Rousseau (1811–74) was an aide-naturaliste [assistant in several volumes of the Transactions de la Société Royale naturalist] and photographer in the zoological department des Arts et Sciences de Maurice between 1869 and 1884. He of the Museum National d’Histoire Naturelle in Paris (for was also active on nearby Anjouan in the Comoros, where a his biography see Sigurjónsdóttir, 1999). The identity of bird (Turdus bewsheri Newton, 1877) and a snail (Bulimus Monsieur Pervillez appears to be lost to history. bewsheri Morelet, 1877) are named for him. Identifying Lycodon aulicus in the Mascarenes 311

Figure 1. The islands of Réunion and Mauritius in the Indian Ocean (red box in the inset map). from Réunion and the two specimens from Mauritius Cercaspis Wagler, 1820 (Pyron et al., 2013a,b), Dinodon is uncertain (Table 1). The date and the collector of the Duméril, 1853 (Guo et al., 2013; Siler et al., 2013), last three were not indicated, but the state of preservation Dryocalamus Günther 1858, and Lepturophis Boulenger, of the specimens suggested that they are historic (pre- 1900 (Figueroa et al., 2016) were synonymised with the 1900). Six of them were photographed, and two of genus Lycodon, making a morphological definition of the these are presented here (Fig. 2). Recently, the genera genus difficult. However, the two species treated here

Table 1. List of specimens examined for this study. Museum abbreviations are explained in the text.

Museum Specimens Locality and Date of Collection MNHN RA-1888.182 Mauritius, 1888 RA-0.9837 Réunion, St André, 1963 RA-1917.168–70 Mauritius, 1917 RA-1922.274–76 Mauritius, 1922 RA-1981.209–12 Réunion, 1981 RA-1982.170 Mauritius, Roches Noires (Flacq), 1982 RA-1988.334–35 Réunion, 1988 ZMB 8158 Réunion, 1864 ZFMK 21766 Réunion 29976 Mauritius 29077 Mauritius

312 Gernot Vogel et al.

Figure 2. Lycodon aulicus collected on (A) Réunion (ZFMK 21766) and (B) Mauritius (ZFMK 29976). Photographs by Gernot Vogel. were placed in Lycodon before the synonymising of the wider in L. aulicus, but the shape of the head is variable other genera, so the definition given by Smith (1943) is in this species and can become altered depending on still relevant. The most recent identification criteria are preservation or circumstances of death. Therefore, described in Vogel and Harikrishnan (2013) and Ganesh head dimensions remain a poor identification criterion. and Vogel (2018). However, the brown dorsal part of the body is often Distinction between Lycodon aulicus and L. characterised by the presence of transverse bright capucinus. Lycodon aulicus is a species whose native stripes in L. aulicus, while this part is more reticulated range is on the Indian subcontinent, characterised by and marbled with bright white to light yellow scales in a dark blackish-brown dorsal part of the body with L. capucinus (Table 1; Fig. 3). Despite the similarity distinct creamy white transversal bars (Ganesh and between L. aulicus and L. capucinus and the high Vogel, 2018). Lycodon capucinus occurs natively in variability in the colouration patterns of the former Southeast Asia and the Indo-Malaysian region and is (Ravichandran and Siliwal, 2010; O’Shea et al., 2018), characterised by a light-brown to reddish-brown dorsal museum specimens and key identification criteria part of the body with reticulated marbled bright scales enabled the formal distinction between both species. (O’Shea et al., 2018). The comparative table of L. aulicus and L. capucinus provides a description of external traits that can be used Results in the field (Fig. 4), but the final identification must be based on the observation of dorsal colour patterns The 19 specimens collected on Mauritius and Réunion (Ganesh and Vogel, 2018). However, the validity of this between 1864 and 1988 were all formally identified as criterion still needs to be cross-validated with genetic L. aulicus based on colour patterns (Fig. 2). Despite analyses. the earlier reports of L. capucinus in the Mascarenes For a long time after the description of the genus (O’Shea et al., 2018), we found no evidence to back this by Linnaeus (1758) very few Lycodon species were assertion after examining known museum material and known and very little information was available on photographs from the literature and amateur naturalists their distribution. Only six species had been described (Mauritian Wildlife Foundation, 2015). by 1839. The distribution of Lycodon is now better documented, and the genus includes 76 species (Adler Discussion and Zhao, 1995; Mukherjee and Bhupathy, 2007; Vogel The confusion between L. aulicus and L. capucinus et al., 2009; Dutta et al., 2013; Uetz et al., 2020). The dates back centuries and persisted until recently known native range of L. capucinus extends from (O’Shea et al., 2018). This is perhaps unsurprising central Myanmar to New Guinea (David and Vogel, since the biometric measures overlap and the scalation 1996; Wogan and Chan-ard, 2012; Siler et al., 2013; is highly similar in both species. The head tends to be O’Shea et al., 2018) and Christmas Island (Fritts, 1988; Identifying Lycodon aulicus in the Mascarenes 313

Figure 3. (A) Lycodon aulicus, photographed in a dry area of Réunion (Pierrefond). (B) Lycodon capucinus from Western Malaysia. Note the clear transverse bright stripes in L. aulicus and the reticulated pattern in L. capucinus. Photographs (A) by Laurent Barthe and (B) Gernot Vogel.

Smith, 1993). The identity of the species established Réunion and Mauritius from continental India, although in Sri Lanka and the Maldives remains to be formally the mechanism of colonisation (human-mediated, some determined (O’Shea et al., 2018). Hence, there is no other biogeographic event) remains unresolved. The evidence of the presence of L. capucinus in the Indian origin of wolfsnakes in these islands remains unstudied Ocean so far. This supports the hypothesis proposed by and there is no evidence that the species was introduced Duméril et al. (1854) of a colonisation of L. aulicus on to the Mascarenes from a single population. Further

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Accepted by Justin Bernstein