The military ground snake (''Erythrolamprus miliaris'') is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...

in the family

Colubridae Colubridae (, commonly known as colubrids , from , 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest fossil species of the family date back to the Late Eocene epoch, with earlier origins suspected. C ...

, which is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to South America.

Common names

South American common names for ''E. miliaris'' include ''cobra-d'água'' (water snake) and ''cobra-lisa'' (smooth snake) in Portuguese, and simply ''culebra'' (snake) in Spanish.

Taxonomy

''E. miliaris'' was originally described as ''Coluber miliaris'' by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in 1758. ''Erythrolamprus miliaris'' belongs to the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

'' Erythrolamprus'', which contains over 50 species. The genus ''Erythrolamprus'' belongs to the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Dipsadinae, which is sometimes referred to as the family Dipsadidae. The relationships of ''Erythrolamprus'' species located in northern South America can be shown in the cladogram below, based on molecular DNA analysis:

Subspecies

Five

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

are recognized, including the nominotypical subspecies. *''Erythrolamprus miliaris amazonicus'' ( Dunn, 1922) *''Erythrolamprus miliaris chrysostomus'' ( Cope, 1868) *''Erythrolamprus miliaris merremi'' ( Wied, 1821) *''Erythrolamprus miliaris miliaris'' (

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

, 1758) *''Erythrolamprus miliaris orinus'' ( Griffin, 1916) The subspecific name, ''merremi'' is in honor of German herpetologist Blasius Merrem.Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). ''The Eponym Dictionary of Reptiles''. Baltimore: Johns Hopkins University Press. xiii + 312 pp. . (''Liophis miliaris merremi'', p. 176).

''Liophis milaris intermedius'', a taxonomic error

In 1991, ''Erythrolamprus miliaris intermedius'' was described by Henle and Ehrl. However, they made a mistake. It was later discovered by Dixon and Tipton, through various comparisons of morphometrics, that ''Erythrolamprus miliaris intermedius'' was actually ''

Erythrolamprus reginae The royal ground snake (''Erythrolamprus reginae'') is a species of snake in the Family (biology), family Colubridae. The species is Endemism, endemic to northern South America. Classification ''Erythrolamprus reginae'' belongs to the genus ''E ...

''.

Geographic range

''E. miliaris'' is found in South America east of the Andes, from the Guyanas south to Paraguay. The former subspecies extending further south (southeastern Brazil, Paraguay, Uruguay and northeastern Argentina) is now recognized as a full species, '' Erythrolamprus semiaureus''.

Habitat

''Erythrolamprus miliaris'' inhabits aquatic and riparian habitats. It occurs in both lowland tropical rainforest and Atlantic forest at elevations below .

Physical characteristics

''E. miliaris'' is stout-bodied (muscular) and relatively short-tailed. Tail length/total length ratios vary from 15.0%–19.8% with an average of 18.6%. Adults may attain a total length (including tail) of about 50 cm (about 20 in). Boulenger GA (1894). ''Catalogue of the Snakes in the British Museum (Natural History). Volume II., Containing the Conclusion of the Colubridæ Aglyphæ.'' London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xi + 382 pp. + Plates I-XX. (''Rhadinæa merremii'', pp. 168-169). Dorsally, it is pale olive-brown or yellowish, with each smooth dorsal scale edged with black. Ventrally, it is uniformly yellow.

Feeding

''E. miliaris'' feeds on a wide range of prey items. They include primarily

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

s (including eggs and tadpoles), but also fish and even lizards and small

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s. Invertebrates have also been reported but may have been secondarily ingested. However, there is little information on its feeding habits. A study indicated that females with oviductal eggs did not feed, whereas those females with secondary vitellogenic follicles fed more often than did the non-reproductive ones.

Sexual dimorphism

There is

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

with respect to size of adult ''Erythrolamprus miliaris''. Adult females are larger in the subspecies ''merremi'' and ''orinus''. They were seen to be larger than the adult males. The sexual dimorphism index was seen to be similar in the geographic areas of the northern coastal Atlantic forest, southern coastal Atlantic forest, northern inland Atlantic forest and southern inland Atlantic forest. This was indicative of no geographic variation in sexual size dimorphism. It is believed that body size may differ either because of local genetic modification or direct phenotypic effect of food availability on the growth rates. In addition to body size, the comparison of head size in ''E. miliaris'' is seen to show no dimorphism. Head size is considered to be associated with inter-sexual dietary divergence.

Reproductive output

With respect to reproductive output in the northern and southern coast Atlantic forest, and the northern and southern inland forest, the reproductive output recorded for ''Erythrolamprus miliaris orinus'' and ''Erythrolamprus miliaris merremi'' were determined via number of eggs, size of eggs, and number of neonates. The mean egg volume in the southern coast Atlantic forest was seen to be the largest of the four regions. The reproductive frequency was lower in the northern coast Atlantic forest than the other regions.

Parasitism

Parasitism is not understood very well in the context of snake ecology. The only inferences that have been made are those with the influence on natural populations. It is thought to be related to the snakes feeding behavior and immunological resistance. Two parasites were discovered in the subspecies ''orinus'' and ''merremi''. The first were adults of the

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

''Ophidascaris'' sp. in the stomach. Also cystacaths of the acanthocephalan ''Oligatanthorynchus spira'' were in the peritoneum. The prevalence found in the four different regions, northern and southern coastal Atlantic forest and northern and southern inland Atlantic forest, were observed in Pizatto's and Marques' study. The lowest prevalence was seen in the northern coastal Atlantic forest. The level of parasite infestation did not differ between the males and females. Female reproductive status was unaffected by the level of infection, nor was the number of eggs she carried. The male reproductive system was unaffected by the level of infestation as well.