Filling biogeographical gaps through wildlife roadkills: New distribution records for six snake species from Ecuador (Anilius scytale, Drymarchon corais, Erythrolamprus breviceps, Micrurus lemniscatus, Oxyrhopus vanidicus, Trilepida anthracina)

ABSTRACT

Monitoring wildlife roadkills is a valuable method to identify critical areas where animals are more susceptible to collision with vehicles, likewise, this type of work can let us know which species are more vulnerable to this human impact. Besides these relevant utilities used for mitigation purposes, this effort can provide very important information about the biology, ecology and biogeography of species. In this paper, we report new geographic records found while working on a road ecology study. These data increase the distribution of six snakes’ species (Anilius scytale, Drymarchon corais, Erythrolamprus breviceps, Micrurus lemniscatus, Oxyrhopus vanidicus and Trilepida anthracina), from which, four show scarce and almost inexistent historical records (Anilius scytale, Drymarchon corais, Erythrolamprus breviceps, and Trilepida anthracina). We encourage researchers, especially road ecologists, to notice and report these observations, which can be highly valuable for expanding the knowledge of species distributions, a key factor forconducting integral studies of fauna.

KEYWORDS:

• Bailey’s blind snake
• Coral cylinder snake
• Indigo snake
• Short ground snake
• South American coral snake

Transportation networks constitute a great source of mortality for many groups of fauna. Among these largely affected groups, snakes have shown the highest numbers across several studies [1–3], which is basically given by their slow locomotion and their attraction to warm roads for thermoregulation [2].

Although roads can be a huge threat to snake's survival, it has been found that records (not only from snakes) obtained from road ecology studies are important sources for registering new information on wildlife species around the world.

This approach has been useful to describe diets [4,5], wildlife parasitic loads [6–9], predation behaviors [10], new species [11], and new distribution records [12,13].

Information on road mortality is often, but not exclusively, found across biodiverse areas. In this context, the Tropical Andes Biodiversity hotspot contains the highest number of endemic vertebrates in the world [14], and species inhabiting this area can be scarcely known.

For instance, a previous work conducted in this area found an undescribed species from the genus Atractus [1]. In the same study, the authors reported a high prevalence of roadkills for Caecilians, a group of amphibians, for which uncertainty of species identification is extremely high. Another study conducted nearby this area [2] found a high mortality for Amphisbaena bassleri, an understudied species whose natural history is practically unknown. It is worth noting that despite the relevance of the findings inside these biodiverse areas, we may be losing species before fully understanding their natural history, geographical ranges, or knowing of their existence.

There is a great need for stronger research efforts in these biodiverse regions, as new information on natural history and geographic distributions can be essential for biologists to determine focal areas for future research.

In this work, we report new (local and regional) distribution records for six snake species: Anilius scytale, Drymarchon corais, Erythrolamprus breviceps, Micrurus lemniscatus, Oxyrhopus vanidicus, and Trilepida anthracina. Most of these species have scarce historical records, thus, there are many information gaps in their natural history and geographical distribution.

Our study area is located inside the most biodiverse hotspot of the world, The Tropical Andes [14]. Specifically, in the Province of Napo, Ecuador; between four protected areas: Antisana Ecological Reserve, Sumaco-Napo-Galeras National Park, Cayambe-Coca National Park, and Colonso Chalupas Biological Reserve. This zone ranges between 300 and 3000 m a.s.l. and is mainly surrounded by three ecosystems: Evergreen piemontane, low montane, and north montane forest of the Eastern Andes [15]. The annual average temperature is 18–19 °C, and the annual precipitation varies between 1100 and 3400 mm [16].

Fieldwork was part of a road ecology project conducted from September 2020 to March 2021. Four to five days per week, between 08:00 h and 17:00 h, we surveyed 240 km of primary and secondary paved roads, driving at an average speed of 40 km/h.

Once detected, each roadkill was photographed, identified, and georeferenced with a GPS unit (Garmin Etrex 22X). When an individual could not be identified to the species level, it was taken to Universidad Regional Amazónica IKIAM laboratory to be thoroughly examined. When individuals were taken to the laboratory for identification, they were analyzed using specialized bibliography (e.g [17–19].) in order to review morphological, ecological, and biogeographical indicators.

We found six new biogeographical records belonging to snake species with scarce information on their natural history and distribution (Figure 1).

• Oxyrhopus vanidicus (Figure 2a)

Figure 1. New distribution records

Figure 2. (a) Oxyrhopus vanidicus, (b) Erythrolamprus breviceps, and c) Drymarchon corais

September 20, 2020, 9:16 h, in the Province of Napo, Cotundo Parish, Jondachi locality (-0.714480º S/-77.791179º W), 1231 m a.s.l.. Individual (72 cm SVL) found dead on road in an area surrounded by pasture and forest. The snake's body was in good condition; thus, the identification was reached with confidence.

This species has been reported in the Provinces of Orellana, Morona Santiago, Napo, Pastaza, and Sucumbíos up to 960 m a.s.l [20]. Our record extends 271 m to its prior upper altitudinal limit.

• Erythrolamprus breviceps (Figure 2b)

February 1, 2021, 14:28 h, in the Napo Province, Cotundo Parish, near Cotundo community (-0.856976º S/-77.791704º W), 712 m.a.s.l.. An individual (23 cm SVL) found on a road surrounded by pasture and forest. Due to good conditions of the body, species identification was not difficult. This species, recorded for the provinces of Napo and Pastaza, has been registered up to 500 m a.s.l. [19], thus, our record extends its upper altitudinal limit an additional 212 m. .

• Drymarchon corais (Figure 2c)

December 19, 2020, 10:45 h, in the Napo Province, Ahuano Parish, near Jumandy Airport (-1.065573º S/-77.588057º W), 380 m a.s.l.. A dead individual (52 cm SVL) was found on a road surrounded by pasture. Species identification was possible given the good condition of the body. This species has been reported in Ecuador only for the Province of Orellana at 230 m a.s.l. [21]. At 380 m a.s.l. our record extends this species' upper altitudinal limit an additional 150 m.  

• Anilius scytale (Figure 3a)

Figure 3. (a) Anilius scytale, (b) Trilepida anthracina, and (c) Micrurus lemniscatus

March 13, 2021, 12:54 h, in the Napo Province, Tena Parish (-1.040332º S/-77.7961601 W), 477 m a.s.l.. A dead individual (35 cm SVL) found on a road surrounded by shrubs. The body's good condition allowed us to identify this species, which belongs to a monotypic genus, thus, there was no place to confusing this individual with another species.

Prior distribution information has been reported for the Provinces of Sucumbíos, Orellana, Pastaza, and Morona Santiago, up to 331 m a.s.l [22]. Our report represents the first record for the Province of Napo, as well as an altitudinal record extending the species' upper limit an additional 146 m.

• Trilepida anthracina (Figure 3b)

January 24, 2021, 9:31 h, in the Napo Province, Cotundo Parish, near Sarayacu community (−0.662891º S/-77.792002º W),1617 m a.s.l., A dead individual (27 cm SVL) in a road surrounded by shrubs. Although the state of the body was not in good conditions, we were able to identify this individual considering specific characteristics such as: a) cylindrical body with a diameter of 6 mm, b) three supralabial scales, and c) 10 rows around the middle of the tail [23]. Additionally, this species cannot be confused with others of the genus Trilepida, as this is the only species that occurs in the Amazon region, with priors reports for the provinces of Tungurahua, Pastaza, Zamora Chinchipe, and Bolívar [24]. Therefore, our report constitutes the first within Napo Province, representing the northeastern record for this species that is only found in Ecuador.

• Micrurus lemniscatus (Figure 3c)

October 11, 2020, 8:11 h, in the Napo Province, Cotundo Parish, near Sarayacu community (-0.664671º S/-77.792002º W), 1595 m.a.s.l.. A dead individual (23 cm SVL) found in a road surrounded by shrubs. This individual was not in good condition, however, we were able to reach species identification analysing revelant characteristics such as: a) body with 8–11 triads of black, red, and white rings, b) long slim body, and c) black head tip followed by a white line, black band, and red band [25].

This species has been reported in the Provinces of Napo, Orellana, Pastaza, Sucumbíos, and Morona Santiago, with an upper altitudinal limit of 1500 m.a.s.l [25], therefore, our record constitutes the highest altitudinal registry for this species.

Our findings represent new altitudinal limits and expand geographic ranges for six snake species. These new records highlight the importance of road ecology studies, which, besides providing information for conservation purposes, can also be highly valuable for improving the understanding of species distributions. In our case, most of the new records correspond to species with scarce and almost nonexistent geographic records across their distributions.

Take for example, Anilius scytale. Although there are studies on its trophic ecology [26] and biology [27], much of the natural history of this fossorial species remain unclear [26]. Moreover, given the scarcity of reports for this species in Ecuador (only eight records reported by Rodríguez–Guerra, A. Mármol–Guijarro (2019), the biogeography of this snake in this country is little understood. This is also reflected by the fact that our sole record constitutes a new upper altitudinal limit, and a new region of geographic distribution.

Likewise, natural history knowledge on Drymarchon corais has been unexplored in Ecuador. Scientific research on this species is practically nonexistent, in fact, its conservation status has not been assessed due to lack of data, being catalogued as data deficient [17]. This reinforces the importance of publishing new distribution records for this species.

Erythrolamprus breviceps is another snake lacking information regarding its natural history [28]. When researching its information on one of the most complete platforms on reptiles in Ecuador (https://bioweb.bio/faunaweb/reptiliaweb), only 3 records were found, which demonstrates the need for more biogeographical data to gain knowledge on several aspects of this species.

Another poorly known snake is Trilepida anthracina, which is catalogued as vulnerable by the IUCN. No scientific investigation has been conducted on this species ecology and biology. This lack of research can likely be attributed to its rareness and restricted distribution (four localities) [29]. Our record adds one more locality to the registered distribution of the species.

New records reported in this paper contribute to improving the understanding of diverse biogeography aspects of these species. We hope this information will help to expand scientific knowledge on their ecology, biology, and local conservation status. Gathering roadkill data for snakes is especially important as it has been shown that even low roadkill rates can increase the probability of populations' extinction [30].

Reporting new distribution records can be relevant in several ways. For instance, this information can guide researchers in determining priority areas to address future efforts when collecting specimens. Furthermore, this data can support analyses on species distribution models [31–33], and can be highly valuable for the development of conservation strategies [34].

Acknowledgments

We are grateful to the University of Reading for funding this work and Universidad Regional Amazónica IKIAM for facilitating the use of laboratories to examine specimens. We are also thankful to Manuela González-Suárez for her support and technical advices for fieldwork and Pablo Jarrín for his help accessing IKIAM facilities.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

University of Reading (GS19-042).