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Philodryas baroniBaron's Green Racer

By Taylor Schoen

Geographic Range

Baron's Green Racers are found in South America and have been collected from Northern Argentina, Paraguay and Bolivia. The Gran Chaco region of Argentina, a semi-arid, sparsely populated lowland, has been reported as the center of their range. (Sanchez, et al., 2014)

Habitat

Baron's green racers are a strictly arboreal species and inhabit savannas, tropical and subtropical forests. (Sanchez, et al., 2014)

Physical Description

Baron’s green racers are a medium sized snake and can reach up to 2 m in length, making them the largest species within the genus Philodryas. They have a slender body, narrow head and relatively long tail. Green is the most common coloration among Baron’s green racers, however, blue and brown varieties may also be found. A brown variety inhabits the northern parts of Argentina and is known as Philodryas baroni var. fuscoflavescens. The eyes of Baron’s green racers are less than one third the snout length and have a round pupil. The snout often comes to a prominent point made of extending rostral scales which are more developed in males than in females, but do occur in both sexes. There are 21 or 23 rows of smooth, single-pitted scales. Some specimens display two longitudinal black lines which pass through the eyes laterally and extend from the rostrum through the anterior third of the body. The upper lip is white and the ventral body surface is often a greenish white. Baron’s green racers are opisthoglyphous, with their fangs located in the rear of the mouth.

There are several morphological features of Baron’s green racers which appear to be well-adapted to these snakes’ habitat choice and activity patterns. A long tail and slender body are common traits of arboreal snakes as these features allow for swift and balanced movement through an arboreal habitat. Green racers are also well-camouflaged amongst tree branches. Their green coloration is advantageous as it allows these diurnal snakes to remain cryptic to both predators and prey. There is little published data on sexual dimorphism in P. baroni, however, closely related arboreal species such as P. olfersii display dimorphism in body size. Females of P. olfersii tend to have a larger body length than males, possibly to increase reproductive potential while remaining slender enough to successfully navigate an arboreal habitat. Similar patterns have been reported in P. baroni by herpetoculturalists. (Boulenger, 1896; Hartmann and Marques, 2005; Sanchez, et al., 2014)

  • Sexual Dimorphism
  • female larger
  • Range length
    2 (high) m
    6.56 (high) ft

Reproduction

The mating system of Baron's green racers is not referenced in the literature, but studies on related species have indicated that multiple mating events may occur within one breeding season. Whether or not these mating events are monogamous, polyandrous, polygynous or polygynandrous is unspecified. (Mesquita, et al., 2013)

Baron’s green racers are oviparous. Herpetoculturalists have reported that females will produce greater than 20 eggs per clutch, but the average clutch size is around 10. Unfortunately there are currently no published field studies which broach the topic of their reproductive cycle. Perhaps inferences can be drawn from a more frequently studied arboreal relative that shares a home range with P. baroni, P. olfersii. P. olfersii have been reported to ovulate for roughly 3 months of the year between November-January, but reproductive individuals of both sexes have been collected year round. Clutch size in this species varied between 4 and 11 eggs, however, there may be potential for multiple mating events and multiple clutches throughout the reproductive season. Males experience a period of reproductive dormancy during the colder months of the year. Baron's green racers return to communal nesting sites each year. ("South American Green Snake", 2015; Mesquita, et al., 2013)

  • Breeding interval
    The breeding interval of Baron's green racers is undocumented in the wild, however, other members of Philodryas breed in the warmer months of the year.
  • Breeding season
    Baron's green racers may breed year round, with a increase in reproductive frequency from November through January.
  • Average number of offspring
    10
  • Range gestation period
    83 to 90 days
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Females invest in resources for their eggs, but little additional information on parental investment is available in the literature.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

No information on longevity in Baron's green racers is reported in the literature.

Behavior

Baron’s green racers are diurnal and peak activity has been reported in the warmer and wetter months, especially in autumn. They are reported to be less aggressive than other members of the genus Philodryas, but may still coil and strike repeatedly if threatened. If threatened, Baron's green racers are also known to excrete a foul-smelling substance from the cloaca in defense. ("South American Green Snake", 2015; Leynaud, et al., 2008)

Home Range

Home range size is not reported in the literature.

Communication and Perception

Like other lizards, Baron's green racers have keen eyesight that they use to capture prey. They also sense chemicals in the air with their tongues. Forms of communication are not reported in the literature for this species.

Food Habits

Baron's green racers are carnivorous and their diet mainly consists of arboreal frogs, lizards, and small mammals. Both constriction and envenomation are used to subdue prey items. Cannibalism of immature individuals by larger members of the species has also been reported. ("South American Green Snake", 2015; Hartmann and Marques, 2005)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • mammals
  • amphibians
  • reptiles

Predation

Baron's green racers are cryptically colored as their green coloration provides camouflage in the foliage. There is no information available concerning the predators of P. baroni. (Hartmann and Marques, 2005)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

No information is available regarding the ecosystem role of Baron's green racers, however, based on their diet it can be inferred that they are an important generalist predator.

Economic Importance for Humans: Positive

Baron's green racers have become popular in the exotic pet trade. They are owned and bred by people all over the world. (Sanchez, et al., 2014)

Economic Importance for Humans: Negative

While reportedly non-aggressive, Baron's green racers have bitten and envenomated humans. No human deaths as a result from a green racer bite have been recorded but bites should be considered medically significant and be treated by a medical professional. The bite symptoms include pain, swelling, hemorrhaging, and lesions on the affected area. (Sanchez, et al., 2014)

  • Negative Impacts
  • injures humans

Conservation Status

Baron's green racers are considered least concern by the IUCN and are not on any lists of endangered or threatened animals.

Contributors

Taylor Schoen (author), Michigan State University , James Harding (editor), Michigan State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

2016. "Baron's green racer Philodryas baroni" (On-line). Accessed May 04, 2016 at http://www.hellabrunn.de/en/animal-dictionary/animals-a-z/barons-green-racer/.

"Philodryas baroni Berg 1895" (On-line). Accessed May 02, 2016 at http://www.philodryas.com/indexENG.htm.

2015. "South American Green Snake" (On-line). Accessed May 04, 2016 at http://sfzoodocents.org/notebook/FactSheets/REPTILIA/SnakeSAGreen.pdf.

Boulenger, G. 1896. Catalogue of the Snakes in the British Museum. London: Taylor and Francis.

Hartmann, P., O. Marques. 2005. Diet and habitat use of two sympatric species of Philodryas (Colubridae), in south Brazil. Amphibia-Reptilia, 26: 25-31.

Leynaud, G., G. Reati, E. Bucher. 2008. Annual activity patterns of snakes from central Argentina (Córdoba province). Studies on Neotropical Fauna and Environment, 43: 19-24.

Mesquita, P., G. Sa-Polidoro, S. Cechin. 2013. Reproductive biology of Philodryas olfersii (Serpentes, Dipsadidae) in a subtropical region of Brazil. Herpetological Journal, 23: 39-44.

Sanchez, M., A. Timoniuk, S. Marunak, P. Tiebler, O. Acosta, M. Peichoto. 2014. Biochemical and biological analysis of Philodryas baroni (Baron’s Green Racer; Dipsadidae) venom: Relevance to the findings of human risk assessment. Human and Experimental Toxicology, 33: 22-31.

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