Blunthead tree snakes are found in Central America (eastern Mexico to Panama) and throughout the coastal countries of northern and western South America (Venezuela, Columbia, Ecuador, Peru, Bolivia, French Guiana, Brazil, Paraguay, Peru, and Argentina), as well as the islands of Trinidad and Tobago. (Hallermann, 2012; Henderson and Knickerson, 1976)
Blunthead tree snakes occupy primary and secondary growth forests as well as plantation areas in lowland moist and wet forests. They also occur in premontane wet forests and rainforests, as well as lower montane wetforests and rainforests. These snakes are arborial, often found in low vegetation including coffee trees and bromeliads, and can be found up to 2000 meters above sea level (most often 1500 meters or below). ("Blunt-headed Tree Snake: Imantodes Cenchoa", 2012; Zug, et al., 1979)
- Range elevation
- 0 to 2000 m
- 0.00 to 6561.68 ft
Blunthead tree snakes have long, slim bodies and very thin necks, with large heads. Their eyes, which have vertical pupils, account for approximately 25% of the length of the head and protrude from the side of the head, enabling the animal to look downward. Snout to vent length for this species is generally around 800 millimeters, but can reach over 901 millimeters; total body length can exceed 1 meter. This snake has an adaptive, enlarged middorsal scale row, which provides stability when climbing. Blunthead tree snakes are primarily white ventrally and pale brown dorsally. The dorsal surface is overlaid with 29-56 dark brown blotches (the number of dorsal blotches varies across this species' range). These snakes have rear fangs. Northern populations of these snakes exhibit sexual dimorphism, with males having slightly longer tails (southern populations do not share this characteristic). Additionally, in some regions head size is variable between males and females, with females typically having greater head lengths and widths. (Myers, 1982; Pizzatto, et al., 2008; Zug, et al., 1979)
- Other Physical Features
- Sexual Dimorphism
- female larger
- Range length
- 232 to 901 mm
- 9.13 to 35.47 in
- Average length
- 800 mm
- 31.50 in
Young develop in eggs laid by females, nourished by yolk. Eggs average 30.7 mm in length. Juveniles hatch, appearing as small adults (average SVL 279.7 mm), typically from March through August, and grow approximately 3.5 millimeters per week for their first two years of life. After this time, they will typically have achieved sexual maturity. (Zug, et al., 1979)
- Development - Life Cycle
- indeterminate growth
Mating may occur in this species year round throughout its range, although the mating season may be correlated with the rainy season in some regions. Areas with long rainy seasons tend to produce longer reproductive seasons, whereas areas with shorter rainy seasons call for a much more rapid reproduction and development process. A few instances of mating related male-male fighting have been recorded for this species, both in the Brazilian Amazon and in a Peruvian rainforest. This is particularly notable, as no other record of ritualistic male-male combat has been reported for any other species within the dipsadine clade. One account of such behavior records a male of a mating pair approaching another nearby male and using the anterior portion of his body to force away this potential rival. (Dos Santos-Costa and da Costa Prudente, 2005; Pizzatto, et al., 2008; Zug, et al., 1979)
- Mating System
- polygynandrous (promiscuous)
Blunthead tree snakes generally exhibit continuous reproduction. However, in areas that have seasonal rainfall, egg laying and hatching is found to correlate positively with local wet seasons; for example, in Guatemala and Mexico, eggs are laid in June and July, with hatchlings appearing in July and August, corresponding with the wet seasons of these countries. In Brazilian rainforests, continuous reproduction occurs; vitellogenesis (yolk production) takes place from September through November or December, eggs are laid from November through January, and hatchlings appear from March through August. These snakes are oviparous. An average clutch will contain 2-3 eggs; clutch size is dependent on factors such as female body size, habitat and feeding habits. Female blunthead tree snakes reach sexual maturity at about 620 mm SVL; males mature around the same size, typically about two years after hatching. (Pizzatto, et al., 2008; Stuart, 1948; Zug, et al., 1979)
- Key Reproductive Features
- seasonal breeding
- year-round breeding
- Breeding interval
- Blunthead tree snakes may breed multiple times throughout the year, depending on the region where they live.
- Breeding season
- Some populations of blunthead tree snakes breed year round while other have breeding seasons correlating to rainy seasons.
- Range number of offspring
- 1 to 3
- Average age at sexual or reproductive maturity (female)
- 2 years
- Average age at sexual or reproductive maturity (male)
- 2 years
There is no literature currently available that describes the parental care in these snakes. Brooding is uncommon in all species of snakes apart from those in the family Pythonidae. Therefore, it is a reasonable assumption, as this species is oviparous, that the female most likely leaves her eggs after laying them and that neither the male nor female looks after the hatchlings. (Zug, et al., 2001)
- Parental Investment
- no parental involvement
No published information exists regarding the average lifespan of these snakes; it is suspected to be highly variable throughout their broad geographical range. (Zug, et al., 1979)
Blunthead tree snakes are nocturnal, arboreal snakes. During the day, they may be found resting in a coiled position in shaded bromeliads, between coffee tree leaves, at tree bases, and in leaf litter. They are noted to prefer shaded resting places. At night, these snakes forage, primarily from ground level up to two meters, throughout various forms of dense vegetation (vine tangles, bushes, small trees). This species is fairly active at night and has been found, in captivity, to travel an average of 5-10 meters in 5 minutes. Although arboreal, blunthead tree snakes will readily travel across the forest floor. They tend to be docile and solitary outside of breeding season, and are not known to bite humans. ("Blunt-headed Tree Snake: Imantodes Cenchoa", 2012; Henderson and Knickerson, 1976; Landy, et al., 1966; Myers, 1982; Slevin, 1939; Stuart, 1948; Taylor, 1951; "Blunt-headed Tree Snake: Imantodes Cenchoa", 2012; Henderson and Knickerson, 1976; Landy, et al., 1966; Myers, 1982; Slevin, 1939; Stuart, 1948; Taylor, 1951)
Communication and Perception
Apart from male-male combat that may occur during mating, very little is known about intraspecific interactions between individuals. Blunthead tree snakes rely primarily on their binocular vision and vertically slit, protruding eyes to hunt at night. Like all snakes, they have well developed olfactory, tactile, and hearing systems. (Dos Santos-Costa and da Costa Prudente, 2005; Myers, 1982; Zug, et al., 2001)
Blunthead tree snakes forage at night, feeding on small arboreal lizards (primarily anoles, such as Norops capito, Anolis latifrons, Norops limifrons, Norops mariarum, and Norops tropidogaster). In addition to small lizards, these snakes have been known to target adult frogs (such as Craugastor crassidigitus and Craugastor raniformis) as well as frog (Agalychnis callidryas) and reptile eggs. Female blunthead tree snakes from Panama are known to be capable of consuming larger prey, such as Anolis frenatus due to their larger heads, leading to a difference in feeding trends not only regionally but between males and females in this area. (Gutierrez-C and Arredondo-S, 2005; Henderson and Knickerson, 1976; Landy, et al., 1966; Myers, 1982; Stuart, 1948; Zug, et al., 1979)
- Primary Diet
- eats terrestrial vertebrates
- eats eggs
- Animal Foods
While no information regarding specific predators of blunthead tree snakes currently exists, main predators of other snakes in Latin America include birds of prey such as laughing falcons (Herpetotheres cachinnans) and crane hawks (Geranospiza caerulescens). These nocturnal snakes hide during the day and their coloration acts as camouflage, helping them to avoid predation. (Campbell and Lamar, 1989)
- Anti-predator Adaptations
These snakes are primarily predators of Anolis lizards and frogs. While no published information exists regarding specific predators of this snake species, it is likely a food source for various bird of prey species. (Asmundsson, et al., 2001; Bursey and Brooks, 2011)
- Eimeria cenchoae (Order Eucoccidiorida, Phylum Apicomplexa)
- Kalicephalus costatus (Order Strongylida, Phylum Nematoda)
Economic Importance for Humans: Positive
No economic benefits to humans from this snake are currently known. Due to their small, thin bodies and general fragility, they are not commonly seen in the pet trade. The general lack of knowledge regarding this species, however, does leave the potential for additional research. (Zug, et al., 1979)
- Positive Impacts
- research and education
Economic Importance for Humans: Negative
Although these snakes are venomous, their bite is not particularly harmful to humans. These snakes are typically docile and are well hidden during the day, limiting any potential human interaction. (Costa, et al., 2010; Myers, 1982; Pizzatto, et al., 2008)
- Negative Impacts
- bites or stings
Blunthead tree snakes have not yet been evaluated by the IUCN and are not considered threatened by any conservation agency. Their cryptic nature and nocturnal habits make population size estimations difficult, though they are known to have low population densities in various areas throughout their large geographical range. (IUCN, 2012; Costa, et al., 2010)
Justin Link (author), Michigan Technological University, Amy Schrank (editor), Michigan Technological University, Jeremy Wright (editor), University of Michigan-Ann Arbor.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
Referring to an animal that lives in trees; tree-climbing.
an animal that mainly eats meat
uses smells or other chemicals to communicate
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.
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- indeterminate growth
Animals with indeterminate growth continue to grow throughout their lives.
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).
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
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.
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
- year-round breeding
breeding takes place throughout the year
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