Yellow anacondas are solitary animals, except in breeding season. Females attract mates through pheromones. Male anacondas will follow this pheromone trail and, once the potential mates encounter one another, they communicate by rubbing one another and proceed with courtship. All anacondas (Eunectes) have heat-sensing pits located along their mouths. These pits are used to find prey by detecting body heat given off by warm blooded animals. Like most snakes, yellow anacondas do not hear well, although they can pick up vibrations through their jaws. Yellow anacondas, like most snakes, rely heavily on their fork-like tongues and chemosensation to navigate their environment and help find prey. The tongue is flicked in and out of the mouth to taste the air, chemicals collected by the tip of the tongue are deposited in the vomeronasal organ on the top of the mouth.
Communication Channels: visual ; tactile ; chemical
Other Communication Modes: pheromones
Perception Channels: visual ; infrared/heat ; tactile ; acoustic ; vibrations ; chemical
Yellow anacondas are on the IUCN Red List as threatened due to poaching. It is illegal to hunt yellow anacondas in most of South America. This law has helped population numbers to increase, but pet trading and zoos still threaten their survival.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Females, after a 6 month gestation period, give birth to fully-developed live young. These young are immediately able to live on their own. Yellow anacondas seem to have indeterminate growth.
Development - Life Cycle: indeterminate growth
Yellow anacondas are large and aggressive snakes that can inflict damage on humans if approached or threatened. They may even pose a predation risk to small children, but attacks on humans by yellow anacondas are exceptionally rare.
Negative Impacts: injures humans (bites or stings)
Yellow anacondas are hunted for their skin to make merchandise such as purses, shoes, and belts. Yellow anacondas are also taken for the pet trade. However, anacondas are unpredictable and dangerous and few people take on the challenge of keeping an anaconda as a pet. Yellow anacondas are kept by zoos, where they are a popular attraction. People are intrigued by these species and also terrified by them.
Positive Impacts: pet trade ; body parts are source of valuable material
Adult yellow anacondas are keystone species; they are one of the top predators in the ecosystems they inhabit. Yellow anacondas influence the number of prey animals, which influences the populations of other prey animals and predators. Ticks from the family Ixodidae are found on yellow anacondas. However, yellow anacondas produce an odor that deters ticks from attaching themselves.
Ecosystem Impact: keystone species
Commensal/Parasitic Species:
Yellow anacondas are generalist carnivorous, preying mainly on animals found in wetland and riparian areas throughout their range. Their diet consists of birds, bird eggs, small mammals, turtles, lizards, occasional fish or fish carrion, and caimans. Wading birds may be their most common prey in some areas. They can reach sizes sufficient to take larger prey, such as brocket deer, peccaries, or capybaras. Yellow anacondas are considered ambush hunters and constrictors. They lay in wait in the water or in vegetation and strike at prey that pass. When prey are grabbed, they begin to wrap their body around the prey and begin constriction. With each exhalation of the prey, the constrictor can squeeze tighter, eventually causing asphyxiation. They may also pull the prey under water during constriction. Yellow anacondas then swallow prey head first by unhinging their jaws, as do other snakes. Along with their incredible jaw flexibility, yellow anacondas have more than a 100 recurved teeth that help to hold and swallow prey. Their digestive system is relatively slow and yellow anacondas may eat only every few days or months, depending on the size of their last prey item. Like other snakes, yellow anacondas can survive long periods without prey. In the wild most predation occurs from June to November, during the relatively dry periods when wetlands areas have shrunk.
Animal Foods: birds; mammals; reptiles; fish; eggs; carrion
Primary Diet: carnivore (Eats terrestrial vertebrates)
Yellow anacondas occur in southern South America, including Paraguay, southern Brazil, northeastern Argentina, and Bolivia.
Biogeographic Regions: neotropical (Native )
Yellow anacondas can be found in swamps and marshlands with slow-moving rivers or streams. They can also be observed in forests searching for large game, such as brocket deer or peccaries. During droughts they can be found using caves for shelter and along river banks in holes that retain water. During the rainy months, yellow anacondas can be found in flooded, treeless areas, where they hunt for aquatic species such as fish or caimans (Caiman).
Habitat Regions: tropical ; terrestrial ; freshwater
Terrestrial Biomes: rainforest
Aquatic Biomes: rivers and streams
Wetlands: marsh ; swamp
Other Habitat Features: riparian ; caves
Most mortality in yellow anacondas occurs as young, when they are smaller and vulnerable to predation. Once they reach adult sizes, yellow anacondas have few natural predators. The typical lifespan for yellow anacondas in the wild is from 15 to 20 years. In captivity yellow anacondas can live up to 23 years. Humans greatly influence the lifespan of yellow anacondas in the wild, as poaching has decreased the number of yellow anacondas to a dangerously unstable level.
Range lifespan
Status: captivity: 23 (high) years.
Typical lifespan
Status: wild: 15 to 20 years.
Although yellow anacondas are much smaller than green anacondas (Eunectes murinus, the world's largest snakes) they do reach lengths of up to 4.6 meters (typical adult range 3 to 4 m). Yellow anacondas have yellowish-green scales with brown or blackish bands and overlapping spots that wrap around the entire body. This provides camouflage in murky water or in forest vegetation. Females grow longer than males and generally weigh more as well. Male yellow anacondas can reach up to 3.7 m in length while a female can reach a length of 4.6 m.
Range mass: 40 (high) kg.
Average mass: 30 kg.
Range length: 2.4 to 4.6 m.
Average length: 3.7 m.
Other Physical Features: heterothermic
Sexual Dimorphism: female larger
Adult yellow anacondas have no natural predators. Humans are their main predators and they are hunted for their skin, for the zoo and pet trade, persecuted out of fear, and their habitats are destroyed. Predators of juvenile yellow anacondas include crab-eating foxes (Cerdocyon thous), tegu lizards (Tupinambis merianae), caimans (Caiman crocodilus), and larger anacondas (Eunectes). In order to avoid predation, young anacondas are camouflaged, as their dark-spotted patterns hides them in the vegetation.
Known Predators:
Anti-predator Adaptations: cryptic
For the most part, yellow anacondas are sequentially monogamous. Males become attracted to females when she produces pheromones released into the air. Males then follows the scent to the female and begin courtship. This courtship normally will take place in water and may last for quite some time. Yellow anacondas have been known to form breeding balls, consisting of one female and multiple males. These breeding balls have been known to stay together for up to a month. In the breeding ball, males compete for mating access to the female. Normally the largest male will win successfully outcompete other males. Larger males may successfully breed with more females as a result.
Mating System: polygynous ; polygynandrous (promiscuous)
Yellow anacondas breed between April and May every year. Females incubate eggs in their bodies and give birth to already hatched young. The gestation period is 6 months, after which the female gives birth to from 4 to 82 young at a size of about 60 cm in length. After giving birth, female anacondas leave her young to defend for themselves. Young anacondas reach sexual maturity at 3 to 4 years old.
Breeding interval: Yellow anacondas breed once yearly.
Breeding season: Breeding occurs in April and May.
Range number of offspring: 4 to 82.
Average number of offspring: 40.
Average gestation period: 6 months.
Range time to independence: 0 (low) days.
Average time to independence: 0 days.
Range age at sexual or reproductive maturity (female): 3 to 4 years.
Range age at sexual or reproductive maturity (male): 3 to 4 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization ; ovoviviparous
Females provide significant resources to their young during incubation, but the young are independent at birth and there is no further parental care.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
The yellow anaconda (Eunectes notaeus), also known as the Paraguayan anaconda,[2] is a boa species endemic to southern South America. It is one of the largest snakes in the world but smaller than its close relative, the green anaconda. No subspecies are currently recognized. Like all boas and pythons, it is non-venomous and kills its prey by constriction.
The Neo-Latin specific name notaeus derives from Ancient Greek: νωταίος, romanized: nōtaios, lit. 'dorsal' (νωταίος is a poetic form of νωτιαίος/nōtiaios). In distinguishing his new species Eunectes notaeus from Eunectes murinus, Edward Drinker Cope stated, "Dorsal scales are larger and in fewer rows."[3]
Adults grow to an average of 3.3 and 4.4 m (10 ft 10 in and 14 ft 5 in) in total length. Females are generally larger than males,[4] and have been reported up to 4.6 m (15 ft 1 in) in length.[2][5] They commonly weigh 25 to 35 kg (55 to 77 lb), but specimens weighing more than 55 kg (121 lb) have been observed.[6] The color pattern consists of a yellow, golden-tan or greenish-yellow ground color overlaid with a series of black or dark brown saddles, blotches, spots and streaks.[2]
The range of the yellow anaconda encompasses the drainage of the Paraguay River and its tributaries, from the Pantanal region in Bolivia, Paraguay, and western Brazil to northeastern Argentina[7] and northern Uruguay.[8] [9] It prefers mostly aquatic habitats, including swamps, marshes, and brush-covered banks of slow-moving rivers and streams.[4] The species appears to have been introduced in Florida, although it is unknown whether the small population (thought to derive from escaped pets) is reproductive.[10]
The yellow anaconda forages predominantly in shallow water in wetland habitats. Most predation occurs from June to November, when flooding has somewhat subsided and wading birds are the most common prey. Observations and analysis of gut and waste contents from regularly flooded areas in the Pantanal region of southwestern Brazil indicate that they are generalist feeders that employ both ambush predation and wide-foraging strategies.
Their prey consists nearly exclusively of aquatic or semi-aquatic species, including a wide variety of mammals, birds, reptiles, amphibians, fish and eggs.[11] Larger specimens can prey upon larger animals, such as brocket deer, capybaras or peccaries.[4] The prey-to-predator weight ratio is often much higher than for other types of Boidae.[12] Cannibalism has been observed in this species, though it is not clear how often this occurs.[13]
The yellow anaconda has few predators. Juveniles and the occasional adult may be taken by caimans, larger anacondas, jaguars, cougars, some canids such as the crab-eating fox, mustelids, and raptors. The species is also hunted by humans for its skin.[10]
In captivity the species has a reputation for being unpredictable and somewhat dangerous to humans.[2][4] In the United States, the import, transportation and sale of the species across state lines were banned in 2012 to try to prevent the yellow anaconda from becoming an invasive species in areas such as the Florida Everglades.[14] The conservation status of the yellow anaconda has not been assessed by the IUCN.
The yellow anaconda (Eunectes notaeus), also known as the Paraguayan anaconda, is a boa species endemic to southern South America. It is one of the largest snakes in the world but smaller than its close relative, the green anaconda. No subspecies are currently recognized. Like all boas and pythons, it is non-venomous and kills its prey by constriction.
