Animal Diversity Web

Geographic Range

Lachesis muta is a viperid snake native to several Central American and South American countries. In Central America, bushmasters can be found in tropical forest areas of Panama, Costa Rica, and Nicaragua. In South America, their range consists of tropical areas of Brazil, Ecuador, eastern Peru, Bolivia, the Guianas, Colombia, Trinidad, and Venezuela. (Bartlett and Bartlett, 2003; Kohler, 2003; Leenders, 2001; Ripa, 1994; Vial and Jimenez-Porras, 1967; Zamudio and Greene, 1997)

At least three subspecies have been described are now considered full species by many authors (see Kohler 2003, Zamudio and Greene 1997, Ripa 1994). Lachesis stenophrys, the Central American bushmaster, occurs from southeastern Nicaragua to the Pacific coast of Columbia and Ecuador. Lachesis melanocephala, black-headed bushmaster, occurs in southeastern Costa Rica (Osa Peninsula and adjacent rain forest areas). Lachesis muta muta encompasses the remainder of the range in South America. (Bartlett and Bartlett, 2003; Kohler, 2003; Leenders, 2001; Vial and Jimenez-Porras, 1967; Zamudio and Greene, 1997)

• Biogeographic Regions
• neotropical
  • native

Habitat

Bushmasters primarily inhabit tropical moist forested areas. In addition, they live in habitats that receive plenty of precipitation, and maintain temperatures of 24 degrees Celsius or more. Due to this preference, bushmasters are only found at altitudes below 1000 m. (Bartlett and Bartlett, 2003; Kohler, 2003; Vial and Jimenez-Porras, 1967)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• rainforest

• Range elevation

  1000 (high) m

  3280.84 (high) ft

Physical Description

Bushmasters are large snakes, with individuals often exceeding 2 meters in length, and with the potential to grow over 3.5 meters; these are the longest venomous snakes in the Americas and the second longest venomous snake in the world (after king cobras). The body ranges from reddish-brown, tan, or even a pinkish color, with very distinct dark, diamond-shaped markings down the back, often edged with yellowish coloring. They have light colored bellies and usually a dark stripe extending from the eye to the back corner of the mouth. The scales are heavily keeled above and there is typically a central vertebral ridge along the dorsum. (Armed Forces Pest Management Board, 2011; Bartlett and Bartlett, 2003; Kohler, 2003; Leenders, 2001)

• Other Physical Features
• heterothermic
• venomous

• Sexual Dimorphism
• sexes alike

• Range length

  2 to 3.6 m

  6.56 to 11.81 ft

Development

Bushmasters are oviparious, typically laying a clutch of 5 to 19 eggs. Bushmasters are the only egg-laying pit vipers in the New World. The females brood the eggs, which have an incubation period of roughly 60 to 79 days. The young hatch at approximately 30 to 50 cm with bright orange or yellow tail tips, used to lure prey; this color fades over time. They gain their adult coloring at 1 to 2 years old and reach sexual maturity at about 4 years old. (Armed Forces Pest Management Board, 2011; Bartlett and Bartlett, 2003; Kohler, 2003; Woodland Park Zoo, 2011)

Reproduction

Bushmasters are solitary except during mating. Males find females by following a scent trail. During the courtship, a male will rub the female's head and flicks his tongue across the female's body. This can escalate to the male flipping himself upside down to rub his back on the female's and striking the female with his body. If successful, the pair can mate for over five hours. (Leenders, 2001; Woodland Park Zoo, 2011)

• Mating System
• polygynous
• polygynandrous (promiscuous)

Females lays 5 to 19 eggs in a burrow, often an abandoned agouti burrow, and guard the nest. They do not eat during incubation and only leave the nest briefly to drink. Incubation requires 60 to 79 days. Newly hatched bushmasters are typically 30 to 50 cm long. Sexual maturity occurs at around 4 years of age. (Bartlett and Bartlett, 2003; Kohler, 2003; Woodland Park Zoo, 2011; de Souza, 2007a; de Souza, 2007b)

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

• Breeding season

  Breeding occurs throughout the year.

• Range number of offspring

  8 to 12

• Range gestation period

  60 to 78 days

• Average age at sexual or reproductive maturity (female)

  4 years

• Range age at sexual or reproductive maturity (male)

  3 to 4 years

Females guard their nests until the eggs hatch. Young are independent once they hatch. (Woodland Park Zoo, 2011)

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

Lifespan/Longevity

Lifespan of wild individuals is unknown. Captive specimens generally live 12 to 18 years, though have been recorded to live up to 24 years. (Woodland Park Zoo, 2011)

• Range lifespan
  Status: captivity

  24 (high) years

• Typical lifespan
  Status: captivity

  12 to 18 years

Behavior

Except during breeding activities, bushmasters are solitary creatures, usually active at dusk or after dark. Many of their habits are unknown as they are so secretive. (Bartlett and Bartlett, 2003; Jacksonville Zoo, 2006; Kohler, 2003; Leenders, 2001; Ripa, 1994; Woodland Park Zoo, 2011)

• Key Behaviors
• terricolous
• crepuscular
• aestivation
• solitary

Communication and Perception

During mate seeking, courtship, and mating, bushmasters use chemical trails and tactile stimulation. Their forked tongues supply the vomeronasal organ, which connects with the accessory olfactory bulb in the brain. Like other vipers, they rattle their tails when threatened, but there are no actual rattles. Bushmasters also have paired pit organs on the face, between the eye and nostril (as do other pit vipers), to sense infrared energy (heat). (Jacksonville Zoo, 2006; Kohler, 2003; Woodland Park Zoo, 2011)

• Communication Channels
• visual
• tactile
• chemical

• Other Communication Modes
• scent marks
• vibrations

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

Food Habits

Bushmasters are crepuscular or nocturnal predators that mostly eat small mammals, such as rodents, in the wild. Birds and reptiles may occasionally be eaten. Spiny rats (Proechimys species) are favored prey items in Costa Rica. Bushmasters are mainly ground-living, sit-and-wait predators; they conceal themselves near likely areas of rodent activity and wait for a prey animal to come within striking range. (Gutiérrez, et al., 1990; Jacksonville Zoo, 2006; Kohler, 2003; Leenders, 2001)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates

• Animal Foods
• birds
• mammals
• amphibians
• reptiles

Predation

Young bushmasters are presumably subject to various predators, such as other snakes or raptors, but adults may have few predators other than humans. (Armed Forces Pest Management Board, 2011; Kohler, 2003)

• Anti-predator Adaptations
• cryptic

Ecosystem Roles

Bushmasters are primary predators of a wide variety of small mammals and perhaps frogs and birds. They are probably preyed on by relatively few species. Bushmasters presumably are subject to various parasites and diseases, but there is little information in the literature. (Kohler, 2003; Leenders, 2001; Woodland Park Zoo, 2011)

Economic Importance for Humans: Positive

Bushmasters, like many other snakes, help reduce rodent populations. In addition, bushmaster venom may offer possible applications for use in medical research and medicines. (Woodland Park Zoo, 2011)

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

Economic Importance for Humans: Negative

Bushmasters are of concern due to their venomous bites. Their venom attacks the circulatory system and can cause death without treatment. The cryptic nature and sit-and-wait predation habits of these snakes makes accidental envenomation a possibility. Bushmasters have been known to follow people for several meters, head held high, after being disturbed and may follow to attack. Bushmasters are greatly feared in some places. (Armed Forces Pest Management Board, 2011; Kohler, 2003; Ripa, 1994; Terence M., 2012)

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

Conservation Status

Bushmasters are listed as vulnerable under the Red List due to habitat destruction. (IUCN, 2011)

• IUCN Red List

  Vulnerable

Other Comments

The scientific name Lachesis muta means "silent fate" referring to their tail shaking, though they lack a rattle. Due in part to their large size, bushmasters produce much more venom than many other species of vipers. For comparison, a bushmaster produces eight times more venom than an American copperhead (Agkistrodon contortrix). (Jacksonville Zoo, 2006; Woodland Park Zoo, 2011)

Contributors

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

References

Armed Forces Pest Management Board, 2011. "Venomous Animals-L" (On-line). Armed Forces Pest Management Board. Accessed November 16, 2011 at http://www.afpmb.org/content/venomous-animals-l#Lachesismuta.

Bartlett, R., P. Bartlett. 2003. Reptiles and Amphibians of the Amazon. Gainesville, FL: University Press of Florida.

Gutiérrez, J., C. Avila, Z. Camacho, B. Lomonte. 1990. Ontogenetic changes in the venom of the snake Lachesis muta stenophrys (bushmaster) from Costa Rica. Toxicon, 28:4: 419-426. Accessed December 09, 2011 at http://www.sciencedirect.com/science/article/pii/004101019090080Q.

IUCN, 2011. "Red List: Lachesis muta" (On-line). IUCN Red List. Accessed December 09, 2011 at http://www.iucnredlist.org/apps/redlist/details/39903/0.

Jacksonville Zoo, 2006. "Bio Facts: Bushmaster" (On-line). Jacksonville Zoo. Accessed December 09, 2011 at http://www.jacksonvillezoo.org/animals/reptiles/bushmaster/.

Kohler, G. 2003. Reptiles of Central America. Offenbach, Germany: Herpeton, Verlog Elke Kohler.

Leenders, T. 2001. A Guide to Amphibians and Reptiles of Costa Rica. Miami, Florida: Distribuidores Zona Tropical, S.A..

Ripa, D. 1994. Reproduction of the Central American bushmaster (Lachesis stenophrys) and the black-headed bushmaster (Lachesis melanocephala for the first time in captivity.. Bull. Chicago Herp. Soc., 29: "165-183".

Terence M., D. 2012. "Bushmaster Lachesis muta muta" (On-line). Accessed December 09, 2011 at http://drdavidson.ucsd.edu/Portals/0/snake/Lachesis.htm.

Vial, J., J. Jimenez-Porras. 1967. The Ecogeography of the Bushmaster, Lachesis muta, in Central America. American Midland Naturalist, 78: 182-187.

Woodland Park Zoo, 2011. "Bushmaster Fact Sheet" (On-line). Accessed November 26, 2011 at http://www.zoo.org/page.aspx?pid=413.

Zamudio, K., H. Greene. 1997. Phylogeography of the bushmaster (Lachesis muta, Viperidae) implications for neotropical biogeography, systematics, and conservation.. Biol.J. Linn. Soc., 62: "421-442".

de Souza, R. 2007. Reproduction of the Atlantic Bushmaster (Lachesis muta rhombeata) for the First Time in Captivity. Bulletin Chicago Herpetological Society, 42: 41-43. Accessed December 01, 2011 at http://www.sos-itacare.org/uploads/media/Prima-reproducao_01.pdf.

de Souza, R. 2007. Reproduction of the Atlantic Bushmaster (Lachesis muta rhombeata) for the First Time in Captivity. Bulletin of the Chicago Herpetological Society, 42: 41-43.