Bothrops jararaca

Geographic Range

Brazilian pit vipers have a geographic range including southern Brazil, northern Argentina, and northeastern Paraguay. They are primarily found in the Brazilian Atlantic Forest, a region that has undergone many ecological changes due habitat fragmentation. This species continues to be found in Rio de Janeiro and Sao Paulo, with populations extending to Mato Grasso. It also inhabits numerous islands, up to 35 km offshore, off the coasts of Argentina and Paraguay.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Brazilian pit vipers prefer dense evergreen and deciduous tropical forests in the Brazilian Atlantic rainforest, up to 1000 m above sea level. They are also found in scrub, savanna, semitropical upland forests, and cultivated fields with nearby vegetative cover; even when basking, they are found under some sort of cover. They are considered semi-arboreal; adults are largely terrestrial, while juveniles are more arboreal, presumably to avoid predators.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• rainforest rainforest
• scrub forest scrub forest

• Other Habitat Features
• agricultural agricultural

Physical Description

Brazilian pit vipers have flat, sharply ridged heads. Their heads are tan to medium dark brown, with black patterning. On the head is a pronounced dark brown strip, outlined by a definite pale coloration, originating behind the eye and continuing posteriorly to the jaw. Overall dorsal coloration may be olive, brown, gray, tan, yellow, or maroon. Coloration is related to geographical variations in the colors of substrates, suggesting that dorsal background color is subject to selective pressures. Dark brown trapezoidal to subtriangular markings are present on both flanks, surrounded by more pale coloration. These markings can be juxtaposed or opposite each other, most frequently lacking a definite pattern. They are pale green to pale yellow ventrally, with irregular blotching of gray pigment throughout. Their eyes have a gold to greenish gold iris, complemented with somewhat darker interlaced lines and eyelids with a pointed canthus (characteristic of species within their genus). Juveniles most often have a light tip on their tails, used for caudal luring of prey.

Brazilian pit vipers are slender, with weekly-keeled head scalation comprised of 5 to 12 intersupraoculars. Supralabial scales average 8-9 in number, with the second fused to form part of the lacunal scales, a characteristic exclusive to crotaline snakes. Lacunolabials are also present on the head. Midbody is made up of 23-25 rows of body scales. Ventral scales range from 170-218 total in males and females, respectively. The number of subcaudal scales, which are predominantly paired, ranges from 51-71 scales for males and females, respectively. Average length is approximately 60 cm, but there have been individuals of up to 160 cm reported. These snakes are sexually dimorphic, with females larger than males; females also produce significantly more (220 mg vs 40 mg), and more lethal, venom than males. Venom composition varies significantly between males and females, with male venom containing more protein diversity. Female venom is more potent for hyaluronidasic and hemorrhagic activities, and is more lethal. In contrast, male venom is more potent for coagulant, phospholipasic, and myotoxic activities. These developmental characteristics may therefore demonstrate niche partitioning between genders as well, particularly in terms of diet.

There are currently five congeneric species considered possibly sympatric to Brazilian pit vipers, but there are no currently recognized sub-species. All exhibit similarities, inculding fusion of the the supralabial scales anterior to the temporal scales. This species is smaller and lighter than the jaracacussa ( Bothrops jararacussa ), also exhibiting more intersuprascapular and ventral scales than this snake. Distinguishable differences between Brazilian pit vipers and Brazilian lanceheads ( Bothrops moojeni ) include size (Brazilian pit vipers being smaller) and coloration; Brazilian pit vipers have a darker, lower residing canthus with a wider postorbital stripe, and lack a sinuous marking on the nape.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry
• venomous venomous

• Sexual Dimorphism
• female larger

Development

Brazilian pit vipers are ovovivoparous; neonates are venomous upon birth and hunt on their own. At birth, females measure 23.5-26.5 cm SVL (snout to vent length), while males measure 24.0-27.9 cm SVL; females weigh 7.0-8.5 g, while males weigh 6.0-9.0 g. Both sexes grow at similar rates until reaching approximately one year of age, at which point females grow significantly faster; within three years, females are significantly larger and heavier than males. Venom of juveniles has a greater anticoagulant effect than that of adults. As young develop, the differences in venom composition and complexity discussed above become more pronounced.

Reproduction

Males have been observed to mate with more than one female. Generally, male-male fighting occurs in viperids, activated by the presence of sex steroids such as androgens and estrogens, prior to copulation. Male-male fighting, as well as any other establishment of dominance, may be less likely in this species than other viperids, however, as females are significantly larger than males.

• Mating System
• polyandrous polyandrous

Courtship and mating occur between April and May. Females have been found with uterine muscular twisting from April through September, indicating that they store sperm in order to delay fertilization. Females demonstrate secondary vitellogenesis and this, along with ovulation and fertilization, occurs in the spring (October through December or January). Parturition time ranges between February and April, as evidenced by a greater presence of juveniles during these months. Long-term sperm storage ensures that development and birth occur during more suitable resource conditions; birth is correlated with high food availability and seasonal rainy periods. Male testes reach their largest size in the summer, although they possess mobile spermatozoa year round (contained within the ductus deferens). It is believed that individuals of both sexes reach sexual maturity by two years of age. On average, 10-14 offspring are produced per season. Females may only reproduce biennially, depending in part on their own nutritional status, as they must have sufficient nutritional resources to produce egg yolk.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• ovoviviparous ovoviviparous
• sperm-storing sperm-storing
• delayed fertilization delayed fertilization

Females create yolks to nourish developing embryos. Following partution, young are independent.

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

Lifespan/Longevity

There is little information currently available on the life expectancy for this species. They are known to live for at least 6.5 years in captivity, but similar species have significantly longer lifespans, indicating that this may be the case for wild Brazilian pit vipers as well.

Behavior

Brazilian pit vipers are encountered most frequently in a coiled, hunting state at night. During the day, they are often found in foliage, in sites at higher elevations. There is a significant reduction in activity during the colder months of the year and peak activity is usually observed during warmer/rainier months, concurrent with breeding. Young spend much more time in trees or other off-ground cover, to avoid predators, while adults are predominantly terrestrial.

• Key Behaviors
• arboreal arboreal
• terricolous
• diurnal diurnal
• nocturnal nocturnal
• sedentary sedentary
• solitary solitary

Home Range

There is no current information available on any average home range of Brazilian pit vipers.

Communication and Perception

Brazilian pit vipers assess their environments by interpreting tactile, infrared, chemical, and visual stimuli. They have highly acute olfactory organs and can sense sexual chemical cues. They also possess the defining feature of pit vipers: infrared sensory pits located on both sides of the head, between the eyes and nostrils. These pits are externally comparable to nostrils, but house organs that detect a range of infrared wavelengths. They also house heat-detecting nerves and are highly vascularized. This enables the snakes to use this sensory information not only for prey detection, but also for thermoregulation. The location of the pits on either side of their heads allow these snakes to sense small deviations in infrared wavelengths, informing them of a potential prey item's location, as well as the distance of prey while hunting at night. Another common feature of pit vipers is refined binocular vision for depth perception, aided by vertical slits in their pupils.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• visual visual
• infrared/heat infrared/heat
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Brazilian pit vipers are generalist feeders that demonstrate an ontogenetic diet shift from ectothermic prey (up to 75% anurans, as well as arthropods) as juveniles to endothermic prey (small mammals, approximately 80% rodents) as adults. They are ambush predators, and are equipped with intricate camouflage and very toxic venom. Juveniles often employ caudal luring to attract prey, coiling up and moving the tip of the tail, which is light in color, across their bodies. The tip of the tail looks very similar to an insect larva, which serves to lure in prey. These snakes tend to feed infrequently, likely due to their sedentary habits and occurrence in moderate climates. When they do feed, two different strike strategies have been observed. One strategy tends to be used with prey that an individual is less familiar with: a snake envenomates its prey and then retracts its head, allowing their venom to take effect and later retrieving and swallowing its prey. With prey that they are habituated to, their strategy for attack is to bite and hold prey in their mouths, without retracting their fangs, while the venom takes effect.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• insects

Predation

Brazilian pit vipers are prey to many larger animals, likely including mammals, snakes, and birds. In particular, white eared oppossums ( Didelphis albiventris ) have been observed to systematically attack and kill these snakes with a lethal bite to their neck or head. In order to avoid predation, Brazilian pit vipers have developed base colorations similar to local substrate. Additionally, a number of defensive behaviors have been observed for this species, including striking (the most common defensive maneuver), tail vibration (warning of an imminent strike), head/neck elevation, and body thrashing. They may also use cryptic and escape behaviors (such as head hiding and body compression). These snakes may vary their defensive behaviors based on predator type.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

In addition to their roles as predator and prey, Brazilian pit vipers may serve as hosts to a variety of endoparasites. Even heavily infested individuals do not appear to be severely affected, with only minor lesions apparent.

Economic Importance for Humans: Positive

This species was the focus of pioneering work on the use of venom in drug development and discovery. Researchers found the venom of Brazilian pit vipers to contain a peptide that caused a severe drop in blood pressure in mice; it was used in the development of the first angiotensin converting enzyme inhibitors, for treatment of people with hypertension and congestive heart failure. The venom also possesses haemocoagulase enzyme, which is used as an antihemorrhagic drug. These snakes may also help to keep populations of agricultural pests, such as rodents, in check.

• Positive Impacts
• source of medicine or drug source of medicine or drug
• research and education
• controls pest population

Economic Importance for Humans: Negative

Bothrops species account for the most human deaths in the New World, and Brazilian pit vipers pose a significant risk to humans. Encounter rates are high because the species is abundant within its geographical range and its preferred habitats include agricultural fields. The toxins present in their venom cause swelling at the envenomation site, necrosis, blistering, hemorrhagic blebs, systemic bleeding into the skin, gums, and nose, and subconjunctival hemorrhage. Collectively, these effects can lead to death due to shock, renal failure, and intrancranial hemorrhage, compounded by severe hypotension.

• Negative Impacts
• injures humans
  • bites or stings
  • venomous venomous

Conservation Status

This species holds no special conservation status; to date, it has not been evaluated by the IUCN or any other agency.

Additional Links

Encyclopedia of Life

Contributors

Adam Murphy (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

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