| Articles | Mindo | Green Sipo (Chironius exoletus) | Linnaeus 1758 |
Spanish name: Machete verde
Recognition: ♂♂ 1044–1531 mm ♀♀ 1298–1545 mm. Chironius exoletus is a large, powerful, aglyphous colubrid that's separable from all other Mindoan snakes by possessing 12 dorsal scale rows at midbody. It also is one of the few snakes that, as adult, is completely yellow-green above (though it can range from olive-drab to dark bluish green, and almost anything inbetween). Juveniles, on the other hand, are usually brownish and faintly marked with light crossbands. That said, other entirely green snakes in Mindo exist (i.e. Dendrophidion brunneus and Liophis albiventris), as do other little, banded forms, but none of these have 12 dorsal scale rows at midbody.
Natural history: Fairly uncommon to locally abundant. Chironius exoletus is a diurnal, heliophilic, terrestrial to arboreal colubrid that sleeps in bushes or trees up to 4 m above the ground at night, and descends to the forest floor during day to actively and visually hunt for amphibians (mainly hylids, but ranids, leptodactylids and tropicanders are also eaten) and lizards. It also is a very alert, lively and witty snake whose defense mechanisms include, threatening positions, swift escape and striking. That said, Chironius exoletus is docile at times, and lacks venom glands, so the snake is harmless to humans. Regarding habitat type, this snake prefers riparian situations within evergreen lowland forests (primary, secondary and even cultivated fields and roads), but is marginally present in foothill and low-montane forests. It lays between 4–12 eggs per clutch. Chironius exoletus is internally parasitized by the trematode Ochetosoma heterocoelium.
Distribution: 41–1471 m. Lowlands and both Atlantic and Pacific foothills and lower-montane areas of Costa Rica south to western South America to Ecuador, northern South America, the Guianas, and the Amazon basin to Peru, southern Brazil, and extreme northeastern Argentina. In Ecuador, Chironius exoletus occurs in the provinces of Azuay, Carchi, Chimborazo, Esmeraldas, Guayas, Imbabura, Manabí, Morona Santiago, Napo, Orellana, Pastaza, Pichincha, Santo Domingo, Sucumbíos, Tungurahua and Zamora Chinchipe. In Mindo, the Green Sipo is known from Hacienda San Vicente and from other unspecified locations near the town.
Conservation status: Least Concern. Chironius exoletus is a widely distributed, genetically variable, and highly adapted snake. Plus, it appears to cope well with at least a minor degree of habitat modification. That said, the population distributed west of the Andes is significantly more threatened than the eastern one, as the percentage of native vegetation cover left in the former is approximately 24% of the original extent. Even more so considering that the remaining percentage is fragmented in a series of poorly connected islands that limits genetic flow between populations.
Etymology: The generic name Chironius was coined by Leopold Fitzinger in 1826, but likely originated in 1790 with Blasius Merrem's work, who used the common name Chirons Natter for Linnaeus' Coluber carinatus. In Greek mythology, Chiron was a centaur reputed for his healing abilities. Likewise, in ancient Greek civilization, sick people hoping for a cure flocked to temples where sacred snakes were carefully tended and presented to the sufferers. Therefore, the term Chironius was likely used as a reference to the healing power of snakes, a believe that lies at the very foundation of medicine and crosses many cultures worldwide. The name exoletus is a Latin derivative and literally means "full grown" or "mature", and probably refers to the large adult specimen (holotype) used for the original description.
Notes: Chironius exoletus shows pronounced ecological and morphological variation across its disjunctive distribution, which is partitioned by the world's longest continental mountain range. Therefore, it seems likely that two distinct species are subsumed under this name.
Other taxonomic problem involves the limit between Chironius exoletus and Chironius monticola, as both forms have historically been confused, and remain so within many scientific collections. This need not be so, because C. exoletus differs from its congener by having a divided anal plate (in ca. 86% of the individuals), apical pits, and by lacking a longitudinal black stripe on the sides of the tail. Moreover, the two snakes have proven to be phylogenetically distinct, and also appear to be altitudinal replacements for each other (with Chironius monticola usually occurring above 1500 m).
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Arteaga AF (2012) Chironius exoletus. In The Amphibians and Reptiles of Mindo. Version 2012.a., eds Arteaga AF, Bustamante-Enríquez LM and Guayasamin JM. Available at: www.tropicalherping.com/articles/inventories/mindo/main.html