''Drymobius margaritiferus'', commonly known as the speckled racer, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of nonvenomous

colubrid Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ever ...

snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...

native to the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''margaritiferus'', means "pearl-bearing" in Latin, referring to the pearl-like spots on the

dorsal scales In snakes, the dorsal scales are the longitudinal series of plates that encircle the body, but do not include the ventral scales. Campbell JA, Lamar WW (2004). ''The Venomous Reptiles of the Western Hemisphere''. Ithaca and London: Comstock Publis ...

Geographic range and habitat

This species ranges throughout

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

from the Isthmus of Tehuantepec and Yucatán Peninsula, southward to

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...

and adjacent areas of northwest

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

, occurring at elevations from sea level up to 4,750 feet (1,453 m). Northward, it is found in the coastal lowlands and lower exterior slopes of the Sierra Madres of

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, up the west coast to

Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...

, and up the east coast to northern

Tamaulipas Tamaulipas (), officially the Free and Sovereign State of Tamaulipas ( es, Estado Libre y Soberano de Tamaulipas), is a state in the northeast region of Mexico; one of the 31 states which, along with Mexico City, comprise the 32 Federal Entiti ...

. The northern limit of its distribution ranges into extreme south

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

, USA, where it is uncommon to rare in a few of the southernmost counties of the state.Werler, John E. and James R. Dixon. 2000. Texas Snakes: Identification, Distribution, and Natural History. University of Texas Press. Austin, Texas. xv, 417 pp. Köhler, Gunther. 2008. Reptiles of Central America, 2nd. ed. Herpeton Verlag. Offenbach, Germany. 460 pp. Speckled racers occur in a wide variety of habitats, including: forest, forest edges and clearings,

secondary growth In botany, secondary growth is the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips of ...

, riparian zones, savannahs,

marshlands A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found a ...

pastures Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep, or swine ...

, and roadsides.Savage, J. M. 2002. The Amphibians and Reptiles of Costa Rica, A Herpetofauna between Two Continents, between Two Seas. University of Chicago Press, Chicago, Illinois. xx, 934 pp. It is often said to favor humid and wet areas with permanent water sources.Lee, J. C. 1996. The Amphibians and Reptiles of the Yucatán Peninsula. Comstock Publishing Associates, Cornell University Press, Ithaca, New York. xii, 500 pp. However, these snakes have been found in areas where no water was apparent, and habitats include

tropical dry forests The tropical and subtropical dry broadleaf forest is a habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive ...

and tropical arid forests.Wilson, Larry David, and John R. Meyer. 1985. The Snakes of Honduras, 2nd. ed. Milwaukee Public Museum. x, 150 pp. Farr, William L. and David Lazcano (2011). Natural History Notes: Drymobius margaritiferus, Thanatosis. Herpological Review, 42(4); 613.McCranie, J. R. 2011. The Snakes of Honduras: Systematics, Distribution, and Conservation.. Contributions to Herpetology, Vol. 26. Society for the Study of Amphibians and Reptiles. x, 714 pp. In

Costa Rica Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...

, it is described as "ubiquitous in ''all but'' the most humid lowland and pre-montane zones," including dry lowland forests.

Description

The speckled racer is typically black in color, with distinctive yellow and blue spotting, and one light-colored spot on each scale, 365 pp. (''Drymobius margaritiferus'', pp. 131-133, Figure 31.) which gives the snake an overall greenish hue. The labials are yellow, with black sutures. The underside is typically yellow to green. They average 30–40 in. (76–102 cm) in length, with a record specimen documented at 50 in. (127 cm). 429 pp. (paperback). (''Drymobius margaritiferus'', p. 186 + Plate 32 + Map 142.) The

, which are feebly keeled middorsally, but smooth on the flanks, are arranged in 17 rows. The

ventrals In snakes, the ventral scales or gastrosteges are the enlarged and transversely elongated scales that extend down the underside of the body from the neck to the anal scale. When counting them, the first is the anteriormost ventral scale that cont ...

number 142–168; the subcaudals, 85–126.

Natural history

As the name "racer" implies, it is a fast and agile species that is predominantly diurnal. It has been described as a nervous species, and will not hesitate to bite in self-defense when restrained or handled. Death feigning behavior, or

thanatosis Apparent death, colloquially known as playing dead, feigning death, or playing possum, is a behavior in which animals take on the appearance of being dead. It is an immobile state most often triggered by a predatory attack and can be found in a ...

, was reported for two out of seven (28.5%) specimens that were caught and handled during field surveys conducted in

, Mexico. They will consume a wide variety of prey, but primarily feed on

frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

s and

toad Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. A distinction between frogs and toads is not made in scientif ...

s. One study of 36 Guatemalan and Mexican specimens with food items in their stomachs found 86% had anurans (predominantly '' Eleutherodactylus''), 8% lizards, 4% reptile eggs, and 2% small mammals. Juveniles are known to eat insects. They are

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

, typically laying eggs in the spring, although in southern areas, the species is known to deposit eggs as early as February and March. Clutch sizes range from two to eight eggs that are usually 1.5 inches (3.8 cm) in length. Incubation is typically eight to nine weeks, with hatchlings measuring 6 to 10½ inches (15.2–27.6 cm) long.

Subspecies

There are four recognized

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

of ''D. margaritiferus'': * ''Drymobius m. margaritiferus'' ( Schlegel, 1837), Northern speckled racer:Liner, Ernest A. and Gustavo Cass-Andreu. (2008). Standard Spanish, English and Scientific Names of the Amphibians and Reptiles of Mexico (2nd. ed.). Herpetological Circular No. 38. Society for the Study of Amphibians and Reptiles. iv, 162 pp. Atlantic versant, Texas to Colombia, and sections of Pacific in

Chiapas Chiapas (; Tzotzil language, Tzotzil and Tzeltal language, Tzeltal: ''Chyapas'' ), officially the Free and Sovereign State of Chiapas ( es, Estado Libre y Soberano de Chiapas), is one of the states that make up the Political divisions of Mexico, ...

, Mexico and southern range. * ''Drymobius m. fistulosus'' ( H.M. Smith, 1942), Central American speckled racer: Pacific versant, from southern Sonora to the Isthmus of Tehuantepec. * ''Drymobius m. occidentalis'' ( Bocourt, 1890), Western speckled racer: Pacific versant, from eastern

, Mexico to

El Salvador El Salvador (; , meaning " The Saviour"), officially the Republic of El Salvador ( es, República de El Salvador), is a country in Central America. It is bordered on the northeast by Honduras, on the northwest by Guatemala, and on the south b ...

. * ''Drymobius m. maydis'' (

Villa A villa is a type of house that was originally an ancient Roman upper class country house. Since its origins in the Roman villa, the idea and function of a villa have evolved considerably. After the fall of the Roman Republic, villas became s ...

, 1968): Corn Islands, Nicaragua.

Conservation status

The speckled racer is a

threatened species Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensa ...

in the state of Texas, USA, where it is uncommon to rare. In some regions of Mexico and Central America, it is a common species.

References

External links

* {{Taxonbar, from=Q973272 Drymobius Reptiles described in 1837 Reptiles of Central America Reptiles of Mexico Fauna of the Rio Grande valleys Reptiles of Guatemala Reptiles of Colombia Taxa named by Hermann Schlegel