Recently, media outlets have been reporting the story of the Antiguan Racer, Alsophis antiguae. Unfortunately, they have been hyping it as the "World's Rarest Snake." Alsophis antiguae is small species with an interesting sexual dimorphism, females are much larger than males and silvery-gray with blotches and stripes, while the smaller males are dark brown with creamy blotches. The species was distributed throughout Antigua and Barbuda, in the West Indies, but in 1926 H. W. Parker declared the species extinct. However, Rick Sajdak and Robert Henderson rediscovered it in 1991 on Great Bird Island off the northeast coast of Antigua. In 1995, Jenny Daltry and colleagues estimated the population at 51 snakes and found the Black Rat was decimating the population. The Jersey Zoo attempted a captive breeding program in 1996 that was unsuccessful. In 1999, ten specimens were moved to Rabbit Island where the Black Rat had been eradicated. The Antiguan Racer population took hold and by 2002 the snakes were reproducing. Subsequently the rats were eradicated on Great Bird Island and the snake population increased by more than 300% over the rest of the decade (see Murphy, 2010 for more details on this story). This is a great snake conservation success story, however, to say Alsophis antiguae is the world's rarest snake is more than a bit misleading, it is just plain wrong.
Some snake species are notoriously difficult to find. They are often cryptic in color, pattern and behavior; have the ability to stay hidden underground, underwater, in tree holes, or other places inaccessible to humans for long periods of time. And, they are often active only at night when diurnal humans are inactive.
There are many, many snake species that are known from only a single specimen, making them much rarer than the Antigua Racer ever was. Thread Snakes of the family Leptotyphlopidae are poorly known fossorial snakes. McDiarmid et al. (1999) list 87 species (more species have been described since this volume was published), 23% of those species listed are known only from their type localities, which in many cases translates to being known from one, or at most a few, specimen.
The Dwarf Pipe Snakes, family Anomochilidae contains three species Anomochilus leonardi, A. monticola, and A. weberi. A. monticola was described in 2008 on the basis of two specimens (Das, et al. 2008). The other two species are known from just a few specimens.
Orlav, et al. (2009) described the new genus and species Colubroelaps nguyenvansangi from Lam Dong Province in southern Vietnam. It is a rarely seen, cryptic, dwarf, fossorial snake combining scale characters both of Colubridae and Elapidae snakes and is known from a single female specimen. The authors tentatively placed in the family Colubridae.
Meyer (2003) noted that South American genus Atractus barely enters the eastern half of the Isthmus of Panama, where it is extraordinarily rare and known from five specimens that had been collected over 39 years, the five Panamanian specimens of Atractus turned out to represent five species. Meyer described four (A. darienensis, A. hostilitractus, A. imperfectus, and A. depressiocellus) based upon a single specimen each. The fifth species A. clarki Dunn and Bailey, was the second specimen of the species previously known only from the Colombia Chocó.
The Reed Snakes of the genus Calamaria are small, ground-soil-leaf litter dwelling snakes of Southeast Asia. Ziegler and Khac Quyet (2005) described Calamaria thanhi (Family Colubridae) from a single adult female specimen that was collected in a primary limestone forest cave. It is the fifth species of Calamaria recorded from Vietnam. Calamaria apraeocularis is known from only four specimens from Cikora, Sulawesi. Calamaria boesemani is known from a single specimen from Pinapuan, Sulawesi. A genus that appears related to Calamaria is Calamorhabdium, it has two species that are known from a total of four specimens. C. acuticeps is known from a single specimen from northern Sulawesi (de Lang and Vogel, 2005).
The Mamberamo River Water Snake, Heurnia ventromaculata (family Homalopsidae) (top photo) was described on the basis of a single specimen in 1926 from West Papua, Indonesia, no other specimens have been found to date. Another homalopsid, Enhydris maculosa, described from a single specimen in 1879, from Myanmar’s Ayeyarwady River delta, has remained known from a single specimen for 131 years.
The family Xenophiidae contains two species: Xenophidion acanthognathus (bottom photo) from Borneo and Xenophidion schaeferi from peninsular Malaysia. Each are known from a single specimen. Thus, the entire family of xenophiid snakes is known from two specimens (Lawson et al. 2004).
William Tanner described the Autlan Long-tailed Rattlesnake, Crotalus lannomi, from a single specimen collected in Jalisco, Mexico in 1966. No other specimens have been found. Even, I spent a few days looking for this snake unsuccessfully. Only recently (Reyes-Velasco et al. 2010) have five more specimens been collected.
The Rough-scaled Python, Morelia carinata was described by L. A. Smith in 1981 from northwestern Western Australia in the lower sections of the Mitchell and Hunter Rivers, near the coast. Originally known from just one specimen, others have now been collected, but the number is far less than that of the Antiguan Racer. The Rough-scaled Python is restricted to islands of forested habitat in the bottoms of rocky gorges.
Cropani's Treeboa, Corallus cropani, is known from only two or three specimens collected in Brazil's highly endangered Atlantic Coastal Forests. Speculation that it is more terrestrial than the other treeboas was due to its stouter body and the fact that at least one of the specimens collected was roadkill. But, the species remains an enigma, with the Instituto Butantan specimens being lost in the fire that destroyed the facility this year, it has become even rarer..
These are just a few examples of snake species known from just one or a few specimens. As paradoxical as it may seem, the world is full of rare snakes.
Cundall, D. and D. A. Rossman 1993, Cephalic anatomy of the rare Indonesian snake Anomochilus weberi. Zoological Journal of the Linnean Society, 109: 235–273.
Das, I., M. Lakim, K. K. P. Lim, and T. Heok Hui. 2008. New Species of Anomochilus from Borneo (Squamata: Anomochilidae). Journal of Herpetology 42(3):584-591.
de Lang, R. and G. Vogel. 2005. The Snakes of Sulawesi. Frankfurt: Edition Chimaira. 312 pp.
Lawson, R., J. B. Slowinski, and F.T. Burbrink. 2004. A molecular approach to discerning the phylogenetic placement of the enigmatic snake Xenophidion schaeferi among the Alethinophidia. Journal of Zoology (2004), 263:3:285-294.
McDiarmid, R., J. A. Campbell, and T. A. Ture. 1999. Snakes Species of the World. Volume 1. The Herpetologists League. 511 pp.
Meyers, C. M. 2003. Rare Snakes—Five New Species from Eastern Panama: Reviews of Northern Atractus and Southern Geophis (Colubridae: Dipsadinae). American Museum Novitates 3391 :1-47.
Murphy, J. C. 2007. Homalopsid Snakes, Evolution in the Mud. Malabar: Krieger Publishing.
Murphy, J. C. 2010. Secrets of the Snake Charmer. Bloomington: iUniverse. 401 pp.
Orlov, N. L., V. E. Kharin, N. B. Ananjeva, N. Thien Tao, and N. Q. Truong. 2009. A New Genus and species of colubrid snake (Squamata, Ophidia, Colubroidae) from South Vietnam (Lam Dong Province). Russian Journal of Herpetology 16:228 – 240.
Reyes-Velasco, J., C. I. Grunwald, J. M. Jones, and G. N. Weatherman. 2010. Rediscovery of the rare Autlan Long-tailed Rattlesnake, Crotalus lannomi. Herpetological Review 41(1):19-25.
Ziegler, T. and L. Khac Quyet. 2005. A new species of reed snake, Calamaria (Squamata: Colubridae), from the Central Truong Son (Annamite mountain range), Vietnam. Zootaxa 1042: 27–38.