Atheris squamigeraAfrican Bush Viper, Rough-scaled Bush Viper

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Geographic Range

Atheris squamigera (green bush viper) inhabits arts of western and central Africa. Its geographic range extends into Kamanyola, a province of Kivu, Congo and Takamanda Forest Reserve in Cameroon. Atheris squamigera has been recorded in the lower elevation forests of Cameroon, particularly those with dense vegetation. (Chifundera, 1990; Corniskey, et al., 2003; Cundall, 2009; Spawls, 1978)

Habitat

Atheris squamigera occurs primarily in tropical forests and areas with dense vegetation where small rodents and other prey animals are abundant. This species is most commonly found at elevations ranging from 100 to 400 m in elevation. The climate of the Takamanda Forest Reserve, Cameroon, where this species is particularly abundant, alternates between rainy (April to November) and dry seasons. Rainfall in the Reserve varies from 1500 mm to 10,000 mm per year. In other forest habitats, such as the Guinean Forest in West Africa, A. squamigera occurs most often at lower elevations, which tends to support greater vegetation densities. In general, A. squamigera resides in moist, terrestrial, and arboreal habitats throughout its geographic range. (Chifundera, 1990; Corniskey, et al., 2003; Cundall, 2009)

  • Range elevation
    100 to 400 m
    328.08 to 1312.34 ft

Physical Description

Atheris squamigera has a compressed body, with scales that are strongly keeled. The dorsal surface of the head is covered with small keeled scales, one of its most distinct features. Typical coloration for is yellowish-green on the dorsum and venter, helping to camouflage it in its natural habitat. Females tend to be slightly larger than males, reaching an average length of 71.2 cm. The average recorded size for males is 65.7 cm. The head is typically larger than their neck, and is triangular. Nasal orientation is lateral, and the openings are partly divided. The snout has a roundish tip and is reltively short. Compared with most other snake species, A. squamigera also has relatively large eyes. It has long, tubular, hollow fangs, which are supplied with venom by a gland located on the upper jaw, between the eyes and mouth. These retractable fangs are connected to a bone that can shift posteriorly within the upper jaw to house the fangs. (Branch and Bayliss, 2009; Chifundera, 1990; Corniskey, et al., 2003; Cundall, 2009; Ota and Hidida, 1987)

  • Sexual Dimorphism
  • female larger
  • Range length
    50 to 79.9 cm
    19.69 to 31.46 in
  • Average length
    65 to 70 cm
    in

Development

After fertilization, Atheris squamigera gives birth to live young (ovoviviparous). Growth is indeterminate, but slows as the snake matures. Juveniles are born venomous and are responsible for capturing their own food. Young snakes can be recognized by the unique coloration of their scales. In addition, the end of their tail is distinctly different and is used as a lure to attract small prey. Time to maturity has not been documented. As individuals age, the coloration of their scales becomes more uniform and may change completely in some cases. (Paukstis and Fredric, 1991)

Reproduction

Although the specific mating system of Atheris squamigera is currently unknown, vipers are typically seasonally monogamous. During courtship, male and female vipers face one another, followed by head and body gestures, which allow for mounting. For example, males often approach their mate while swaying their head side to side in order to engage a female. (Antonio, 1980; Minakami, 1979)

Atheris squamigera reproduces once yearly, typically during the wet season (May to August). Mating occurs most often at night cycle, between 6 pm to 2 am. Once the eggs are fertilized, gestation lasts for 2 months. On average, 7 to 9 offspring are produced. Females reach reproductive maturity 42 months after birth. Males are capable of reproduction much earlier, typically after 24 months. (Luiselli, et al., 2000; Shine, 1980)

  • Breeding interval
    Atheris squamigera breeds once yearly.
  • Breeding season
    Atheris squamigera breeds during the wet season, from May to August).
  • Range number of offspring
    2 to 19
  • Average number of offspring
    7 to 9
  • Average gestation period
    2 months
  • Average age at sexual or reproductive maturity (female)
    42 months
  • Average age at sexual or reproductive maturity (male)
    24 months

As an ovoviviparous species, female green bush vipers carry their unborn young internally, protecting them in the pre-birth stage. Like many vipers, green bush vipers abandon offspring immediately after birth. Neonates are venomous and completely independent. (Graves and Duvall, 1995; Luiselli, et al., 2000)

  • Parental Investment
  • pre-hatching/birth
    • protecting
      • female

Lifespan/Longevity

Average lifespan for green bush vipers has not been documented. Most vipers live 10 to 20 years in the wild. It has been suggested that captive vipers may live longer because risk factors such as predation, disease, and diet are controlled. (Minakami, 1979)

Behavior

Atheris squamigera is nocturnal and like other vipers, is an ambush predator. As such, it spends a large amount of time laying in wait for potential prey to enter its immediate environment. Once in range, A. squamigera strikes very rapidly, with speeds recorded in milliseconds. It spends large amounts of time in one place due to this predatory behavior. Except during mating periods, A. squamigera is a solitary species. (Chifundera, 1990; Cundall, 2009; Freiria, et al., 2006)

Home Range

There is no information available regarding the average home range size of Atheris squamigera.

Communication and Perception

Atheris squamigera uses primarily vision for communication and perception, but also makes use of tactile and olfactory senses. When threatened, it extends its body and raises the anterior portion of its body into the air, settling into a striking position. Posturing is used to ward of predators and during intrasexual competition for mates. During male-male competition, the individual that makes himself appear larger is most often dominant. Communication between sexes is done primarily for reproduction. In order to attract potential mates, males perform a number of different motions, including tail waving, rubbing, biting, and rhythmic body motions. Atheris squamigera lacks the heat-sensing pit organs present in many other viper species. Instead, they rely on visual, tactile, and olfactory senses to detect and capture prey. (Akani, 2000; Carpenter, 1977)

Food Habits

Atheris squamigera is carnivorous. It does most of its hunting at night and is an ambush predator. It feeds mainly on small, nocturnal mammals such as shrews and rodents. Less commonly, it feeds on birds and small reptiles. Juveniles feed on reptiles more often than their adult counterparts. Like other vipers, A. squamigera adults often prey on adolescent snakes of their own species. The venom of A. squamigera is lethal and is used to subdue and kill prey prior to ingestion. In humans, the bite of A. squamigera often causes fever, hemorrhaging, and death. (Akani, 2000; Freiria, et al., 2006; Mueller, 1998)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • reptiles

Predation

Atheris squamigera has few predators. The most commonly noted predators are other snakes, including conspecifics. Humans living near A. squamigera habitat sometime capture it for food, but typically only when it threatens fishing or agricultural activities. (Chifundera, 1990; Corniskey, et al., 2003)

To avoid predation, green bush vipers rely on the same mechanisms used for hunting. Their camouflaged scale patterns allow them to blend in with the surrounding environment. This coloration serves a two-fold purpose, allowing the viper to strike and surprise potential prey, and go unnoticed by potential predators. This ambush-based hiding and hunting behavior allows the snake to sometimes hide rather than engaging in defensive or aggressive behavior. The bright coloration also serves as a warning of the snake's venomous nature to potentially threatening animals. (Chifundera, 1990; Corniskey, et al., 2003)

  • Known Predators

Ecosystem Roles

Because it feeds primarily on small rodents, many of which may carry zoonotic diseases and be considered agricultural pests, Atheris squamigera may help control pest species throughout its geographic range. Parasites of this species have not been documented. (Butynski and McCullough, 2007; Edirisinghe and Bambaradeniya, 2006; Mallet and Joron, 1999)

Economic Importance for Humans: Positive

Many vipers, including Atheris squamigera are farmed for their venom, a process is known as "milking". The venom is used to produce antivenom and for medical and biological uses. Although it is not hunted as a primary food source, it is occasionally captured in fishing nets as by-catch and thus sometimes used as food source. (Chifundera, 1990; Corniskey, et al., 2003; Cundall, 2009)

Economic Importance for Humans: Negative

Green bush vipers are venomous, and as such pose a potential threat to humans. Many unprovoked attacks occur during agricultural activities, as this species is an ambush predator and lies in wait for potential prey. (Chifundera, 1990; Raab and Fitzal, 2005)

  • Negative Impacts
  • injures humans

Conservation Status

Atheris squamigera has not been evaluated by the IUCN and is not listed as a species of concern on any known threatened species lists.

Contributors

Michael Berces (author), Radford University, Patrick Moore (author), Radford University, Christine Small (editor), Radford University, John Berini (editor), Animal Diversity Web Staff.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

visual

uses sight to communicate

References

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