Viper Facts

There are over 330 viper species¹.
According to The Reptile Database there are 364 viper species².

References:
1. Maritz et al. 2016 | 2.THE REPTILE DATABASE 2021 January 05 https://reptile-database.reptarium.cz/advanced_search?taxon=Viperidae&submit=Searc)

Vipers can be easily visually distinguished by certain traits they don’t share with other snakes such as:

• Shorter and stouter bodies
• Large triangle-shaped heads
• Longer jaws
• Large eyes with vertically slit pupils

Other characteristics of vipers include:

• Presence of venom glands located between the eye and the jaw joint.
• They are ambush predators that rely on camouflage (crypticism) and also on luring techniques to catch prey. Indeed, vipers can sit and wait for a long time and use their tail movements to attract and bring prey close enough to catch (practice called caudal luring).
• Unlike the other snakes many vipers are viviparous, which means that females give birth to live young.
• Vipers females also take care of their young which is not very common among snakes.
• Vipers have relatively low metabolic rates and energy requirements.

References:
1. Silva et al. 2016 | 2. Pough and Groves, 1983 | 3. Greene 1997 | 4. Fenwick et al., 2011; Greene et al., 2002 | 5. Cundall and Greene, 2000 | 6. Nowak et al., 2008

Vipers are snakes that are present in all continents except Australia and Antarctica. They can be found in most of terrestrial ecosystems, from deserts to moist tropical forests.^1,2,3

Most viper species live on land (terrestrial species) or in the trees (arboreal species). However some of them are adapted to digging and live partially underground (semifossorial species). There is also one species that is semiaquatic and spends part of its time in water. ^4,5

Vipers are the snakes that can be found at the highest latitudes (over 65° North in Vipera berus and 47° South in Bothrops ammodytoides) and elevations. Indeed, Gloydius Himalayanus, also called Himalayan pit vipers, is the highest living snake and can be found up to 4800m above sea level in Nepal. Crotalus Triseriatus, also called Dusky rattlesnake, can be found at elevations up to 4570m in Mexico.⁶

References:
1. Mallow et al., 2003 | 2. Campbell and Lamar, 2004 | 3. Gumprecht et al., 2004 | 4. Young and Morain 2003 | 5. Greene 1992 | 6. Maritz et al. 2016

Vertical pupils grant two advantages to vipers. It allows them to be active during the day as well as at night because they are able to avoid daylight dazzle and they have better visual acuity than snakes with circular pupils. The disruption created by vertical pupils due to the outline of the eyes makes vipers less conspicuous and so, more efficient in surprising their prey.¹

References:
1. Brischoux et al. 2010

Fangs are long and pointed teeth. In vipers, fangs are long, hollow and hinged and allows vipers to inject venom. Indeed, fangs are connected to  vipers’ venom gland located behind the eyes at the back of the upper jaws.

Vipers can open their mouth widely and have highly mobile fangs. This enables vipers to extend their fangs when biting but also to fit them into their mouth when not in use. In vipers fangs are so long that the bone that bears them must be rotated backward to fit the fang into the closed mouth, a feat permitted by remarkably mobile connections between the upper jaws and the braincase.

References:
1. Kardong 1974; |2. Kardong et al. 1986; |3. Cundall 2002, 2009

Vipers can bite without injecting venom. This phenomenon is called dry bite and can happen in human snakebites. Dry bites can happen because of a failure to inject venom, due to several factors however, most of the time dry bites result from a decision of the vipers to conserve their venom which can run out and takes time to replenish. Indeed, it takes about 14 days for vipers to reach their maximal level of venom after having been milked.¹

References:
1.  Pucca et al. 2020

Among vipers, very different diets can be found depending on their size but also on their habitat. Prey are very diverse and can include centipedes, insects, fish, amphibians, reptiles, birds, and mammals.^1,2

References:
1. Greene, 1997; | 2.Martins et al., 2002 

Like other snakes, vipers don’t eat often. In the wild, the frequency of the meals depends on various factors including the snake’s age, size, activity level and also hunting success rate.

Many species of vipers are adapted to eat really large meals, and while some can eat smaller items every few weeks, particularly young vipers, there are some that eat prey so large that a single meals can be enough to sustain them for months.

Up until 2016, Asia was the VSG region with the highest number of vipers species with 100, followed by Mesoamerica with 85, South America with 55, Africa with 49, Middle East with 34, North America with 25, and Europe with 17.¹

References:

1. (Martiz et al. 2016)

Females tend to be longer than males. However, males have longer tails since they have specialized copulatory organs called hemipenes and muscles used for the expulsion of these.¹
Females also have more robust heads and wider mouths than males.²

References:

1. King, 1989; Shine, 1993; Greene, 1997 | 2.da Silva et al. 2017

All vipers are snakes, but not all snakes are vipers. Vipers belong to a family technically called Viperidae. All members of this family are descendants of a common ancestor and share characteristics that differentiate them from other groups of snakes.¹

The 364 species of Viperidae are grouped into 35 genera that belong to three subfamilies: Viperinae known as true vipers has 101 species, Azemiopinae with two species, and the most diverse, Crotalinae known as pit vipers with 261 species.²

References:

1. Alencar et al. 2016 | 2. Uetz et al. 2020