Imantodes cenchoa

Geographic Range

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.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

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).

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest
• mountains mountains

Physical Description

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.

• Other Physical Features
• venomous venomous

• Sexual Dimorphism
• female larger

Development

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.

• Development - Life Cycle
• indeterminate growth indeterminate growth

Reproduction

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.

• Mating System
• polygynandrous (promiscuous) 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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• year-round breeding year-round breeding
• sexual sexual
• fertilization fertilization
• oviparous oviparous

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.

• Parental Investment
• no parental involvement

Lifespan/Longevity

No published information exists regarding the average lifespan of these snakes; it is suspected to be highly variable throughout their broad geographical range.

Behavior

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.

• Key Behaviors
• arboreal arboreal
• nocturnal nocturnal
• sedentary sedentary
• daily torpor
• solitary solitary

Home Range

These snakes are not known to have a specific home range or to defend territories.

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.

• Communication Channels
• visual visual
• tactile tactile

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Blunthead tree snakes forage at night, feeding on small arboreal lizards (primarily anoles, such as Anolis capito , Anolis latifrons , Anolis limifrons , Anolis mariarum , and Anolis tropidogaster ). In addition to small lizards, these snakes have been known to target adult frogs (such as Eleutherodactylus crassidigitus and Eleutherodactylus 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.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • eats eggs

• Animal Foods
• amphibians
• reptiles
• eggs

Predation

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.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

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.

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.

• 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.

• Negative Impacts
• injures humans
  • bites or stings

Conservation Status

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.

Additional Links

Encyclopedia of Life

Contributors

Justin Link (author), Michigan Technological University, Amy Schrank (editor), Michigan Technological University, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

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