South American Bushmaster

Lachesis muta 

Length: an average of 6.6 ft to 8.2 ft (2 to 2.5 m), although 9.8 ft (3 m) is not too unusual. The head is broad and very distinct from the narrow neck. The snout is broadly rounded. There is no canthus. A pair of small internasals is present, separated by small scales. The supraoculars are narrow. Other parts of the crown are covered with very small scales. Laterally, the second supralabial forms the anterior border of the loreal pit, while the third is very large. The eye is separated from the supralabials by 4-5 rows of small scales. 

The body is cylindrical, tapered and moderately stout. At mid-body, there are 31-37 non-oblique rows of dorsal scales that are heavily keeled with bulbous tubercles and feebly imbricate. There are 200-230 ventral scales. The tail is short with 32-50 mainly paired subcaudals, followed by 13-17 rows of small spines and a terminal spine.  The color pattern consists of a yellowish, reddish or grey-brown ground color, overlaid with a series of dark brown or black dorsal blotches that form lateral inverted triangles of the same color. The lateral pattern may be precisely or indistinctly defined, normally pale at the center.








East of the Andes Mountains in Colombia, eastern Ecuador, Peru, northern Bolivia, eastern and southern Venezuela, Guyana, Surinam, French Guiana and much of northern Brazil


Primary and secondary forests; adjacent fields and cleared areas

Life Expectancy

About 12 – 18 years in captivity; wild - unknown

Sexual Maturity

About 4 years of age


In the wild, they feed on rodents, birds, amphibians and insect. In the Zoo they are fed rats.


Not listed; AZA – managed population


The bushmaster is an oviparous species, which means they lay eggs rather than bear live young. The bushmaster is the only egg-laying pit viper in the Americas. Bushmasters are solitary except when mating. Males find receptive females by following scent trails left by females. Finding a female, he rubs his head and flicks his tongue along the sides of her body to state his intentions and make sure she is receptive. If so, he flips his body upside down on top of hers and rubs his spinal ridge back and forth in a sawing motion against her body to stimulate her. If she is coiled up, he may also strike her with the side of his body to encourage her to loosen her coils and allow him access. When she uncoils, they wrap their bodies around one another and mate in that position, sometimes remaining together for five or more hours. When a female bushmaster is ready to lay her eggs, she finds a burrow built by another small animal to claim as her own, sometimes sharing the burrow with the animal that built it. She then lays 8 to 16 eggs, each of which is white and slightly larger than a chicken egg. After laying her eggs, the female coils her body around them and guards them until they hatch 76-79 days later. She will not leave her eggs even to hunt during this period. Newborn bushmasters are about 20 inches (50 cm) long. Color ranges from pale to vibrant like the adults with a bright orange or yellow tail tip they gradually lose as they get older. This may help the young bushmasters attract small, insectivorous mammals to eat. The colors of the young bushmaster will usually change to their dark adult pattern when the snake is between 1-2 years old. Sexual maturity is typically reached around 4 years.


The bushmaster, like other pit vipers, has a special adaptation that helps them detect their warm-blooded prey. They have two heat-sensitive pits, one on each side of their heads, halfway between their eye and nostril. These pits allow the snake to sense the heat difference between a small mammal and the cooler rocks, plants and other objects in the area. When a warm-blooded animal ventures closer than 20 inches (50 cm), the bushmaster can detect the prey entirely by its body heat, even aiming its strike without any other sensory information. Their heat-sensitive pits allow a bushmaster to detect a heat difference of just 0.0036° F (0.002°C).

Special Interests

There are four bushmaster subspecies. The subfamily Crotalinae is comprised of species commonly known as pit vipers, such as rattlesnakes, copperheads, and water moccasins. The bite of Lachesis muta muta can be fatal. It is one of the largest and most dangerous snakes in South America. Victims will usually complain of pain at the bite site and swelling may be evident. Significant local tissue destruction can ensue, along with a substantial coagulopathy. Victims may also experience additional symptoms which are unique. These include abrupt hypotension, decreased heart rate, intense colic, and bloody diarrhea. Prompt medical therapy avoids these problems. These signs and symptoms will usually manifest earliest, though their development will vary considerably from case to case. Not all of these will necessarily occur, even with severe envenomation: edema & pain, hemorrhage (gingival, wound, rectal), blister formation around wound site, abdominal pain (intense colic), bloody diarrhea, hypotension (diastolic & systolic), bradycardia, diminished heart sounds, brief loss of consciousness, blurry vision, dizziness and/or vomiting.


Lachesis is one of the three Fates in Greek mythology and was supposed to assign to man his term of life—something this species is certainly capable of doing. The species is similar in appearance to rattlesnakes and vibrates its tail vigorously when alarmed, but has no rattle and was therefore called mutus (later muta), which is Latin for ‘dumb or mute’. Together, Lachesis muta means “silent fate.”


The population of bushmasters in the wild is unknown, due to their secretive habits and the dense forests and difficult terrain they typically inhabit. The extensive degradation and destruction of the tropical rain forests of South America is a major threat to this and many other plant and animal species. The Association of Zoos & Aquariums (AZA) manages this species captive population in AZA accredited institutions. Called a PMP (Population Management Plan), basic population management is necessary if zoos and aquariums are to maintain stable, self-sustaining populations for their display and conservation purposes. In 1994, the AZA’s Wildlife Conservation and Management Committee (WCMC) created Population Management Plans (PMPs) to provide basic population management for various captive populations. PMPs are established for studbook populations that do not require the intensive management and conservation action of Species Survival Plans (SSPs). Proper population management can ensure the long-term survival of the captive population and the health of individual animals.

Jacksonville Zoo History

This largest of Neotropical vipers has been in the Jacksonville Zoo collection since 2003. It has successfully bred at our Zoo.


Range of the Jaguar