Lucas Bustamante / Red tailed boa constrictor (Boa constrictor constrictor) juvenile, portrait, with tail wrapped round head, Cuayabeno, Sucumbios, Ecuador.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

Michael D. Kern / Red Tailed Boa {Boa constrictor constrictor} captive, from South America

Mary McDonald / Boa constrictor (Constrictor constrictor). South America

Pete Oxford / Boa Constrictor (Boa constrictor) coiled around a mossy tree branch in the rainforest, South America

George Sanker / Everglades racer (Coluber constrictor paludicola) with tongue out. Everglades National Park, Florida, USA. March.

George Sanker / Everglades racer (Coluber constrictor paludicola). Everglades National Park, Florida, USA. March.

George Sanker / Everglades racer snake (Coluber constrictor paludicola). Everglades National Park, Florida, USA. March.

Karine Aigner / Eastern yellow-bellied racer (Coluber constrictor flaviventris), eating a checkered garter snake (Thamnophis marcianus). Texas, USA, July.

Jen Guyton / Pale morph Boa constrictor (Boa constrictor) from Tayrona National Park, Colombia. Controlled conditions.

Jen Guyton / Boa constrictor (Boa constrictor) Tayrona National Park, Colombia.

Lucas Bustamante / Red tailed boa constrictor (Boa constrictor) on fallen tree over water, Yasuni National Park, Orellana, Ecuador.

Ingo Arndt / Madagascar boa constrictor {Acrantophis madagascariensis} captive

Pascal Kobeh / Dumeril's ground boa (Acrantophis dumerili) held by a guide, Nosy Be, Madagascar

MYN / JP Lawrence / Blackmask racer (Coluber constrictor latrunculus) coiled. Oxford, Mississippi, USA, April. Meetyourneighbours.net project

MYN / JP Lawrence / Young Boa constrictor (Boa constrictor) Gamboa, Panama. Meetyourneighbours.net project

Nick Garbutt / Juvenile Colombian Red-tailed Boa Constrictor (Boa constrictor constrictor) moving along a barbed wire fence. Unamas Reserve and Ranch, Los Llanos, Colombia, South America.

Nick Garbutt / Juvenile Colombian Red-tailed Boa Constrictor (Boa constrictor constrictor) moving along a barbed wire fence. Unamas Reserve and Ranch, Los Llanos, Colombia, South America.

Nick Garbutt / Juvenile Colombian Red-tailed Boa Constrictor (Boa constrictor constrictor) moving along a barbed wire fence. Unamas Reserve and Ranch, Los Llanos, Colombia, South America.

Nick Garbutt / Dumeril's Boa (Acrantophis dumerili) basking in late afternoon sunshine on forest floor. Berenty Private Reserve, southern Madagascar.

MYN / JP Lawrence / Young Boa constrictor (Boa constrictor) Gamboa, Panama. Meetyourneighbours.net project

Tim Fitzharris / Boa Constrictor (Boa constrictor), Costa Rica

Suzi Eszterhas / Boa Constrictor (Boa constrictor imperator) Northern Costa Rica, Central America

Suzi Eszterhas / Boa Constrictor (Boa constrictor imperator) Northern Costa Rica, Central America

Claudio Contreras / Dumeril's boa (Acrantophis dumerili), captive.

Daniel Heuclin / Red-tailed Boa constrictor (Boa constrictor constrictor) captive from South America

Claudio Contreras / Boa (Boa constrictor), Calakmul Biosphere Reserve, Yucatan Peninsula, Mexico, October.

Claudio Contreras / Boa (Boa constrictor sigma) camouflaged against leaf-litter. Maria Madre Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, July.

Claudio Contreras / Boa (Boa constrictor sigma). Maria Madre Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, July.

Claudio Contreras / Boa (Boa constrictor sigma) on branch. Maria Madre Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, July.

Claudio Contreras / Boa (Boa constrictor sigma) in strike-ready pose. Maria Madre Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, June. Captive.

Claudio Contreras / Boa (Boa constrictor sigma) in strike-ready pose. Maria Madre Island, Islas Marias Biosphere Reserve, Sea of Cortez (Gulf of California), Mexico, June. Captive.

John Cancalosi / Boa constictor (Boa constictor constrictor) on branch, Costa Rica, July

John Cancalosi / Boa constictor (Boa constictor constrictor) on branch, Costa Rica, July

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Tropical Milksnake (Lampropeltis triangulum)with neck coiled in striking pose. This is a non-venemous constrictor. Santa Rosa National park tropical dry forest, Costa Rica.

John Cancalosi / Tropical Milksnake (Lampropeltis triangulum) coiled around tree trunk. This is a non-venomous constrictor. Santa Rosa National park tropical dry forest, Costa Rica.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Tropical Milksnake (Lampropeltis triangulum) on trunk in strike pose. This is a non-venemous constrictor. Santa Rosa National park tropical dry forest, Costa Rica.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

Pete Oxford / Eastern Racer (Coluber constrictor) in defensive posture, Little St. Simon's Island, Georgia

Pete Oxford / Northern Black Racer (Coluber constrictor constrictor) snake amid ferns, northern Georgia

Daniel Heuclin / Boa constrictor (Boa constrictor constrictor) climbing a branch in forest habitat. French Guyana, August.

Daniel Heuclin / Boa constrictor (Boa constrictor constrictor) resting on a log in forest habitat. French Guyana, August.

Pete Oxford / Redtail Boa (Boa constrictor constrictor) captive, Ecuador

Pete Oxford / Redtail Boa (Boa constrictor constrictor) captive, Ecuador

Pete Oxford / Black racer (Coluber constrictor) Little St Simon's Island, Barrier Islands, Georgia, USA

Mark Carwardine / Boa constrictor (Boa constrictor) captive, from South America

Mark Carwardine / Boa constrictor (Boa constrictor) captive, from south America

Mark Carwardine / Boa constrictor (Boa constrictor) captive, from South America

Michael D. Kern / Red tail boa (Boa constrictor constrictor) with mouth wide open, captive, from South America

James Christensen / Western Yellow-bellied Racer (Coluber constrictor mormon) near Imnaha, Oregon

Pete Oxford / Boa Constrictor (Boa constrictor) coiled up on leaf litter, native to Central and South America

Pete Oxford / Boa Constrictor (Boa constrictor), native to Central and South America

Pete Oxford / Boa Constrictor (Boa constrictor), native to Central and South America

Pete Oxford / Southern Black Racer (Coluber constrictor priapus), Little St. Simon's Island, Georgia

Pete Oxford / Southern Black Racer (Coluber constrictor priapus) in leaf litter, Little St. Simon's Island, Georgia

Pete Oxford / Southern Black Racer (Coluber constrictor priapus), Little St. Simon's Island, Georgia

Pete Oxford / Southern Black Racer (Coluber constrictor priapus) with tongue extended, Little St. Simon's Island, Georgia

Edwin Giesbers / Boa constrictor {Constrictor constrictor} captive, from South America

Edwin Giesbers / Close up of scales and skin pattern of Boa constrictor {Constrictor constrictor} captive, from South America

James Christensen / Boa Constrictor (Boa constrictor) coiled, Colon, Panama

Sebastian Kennerknecht / Western Yellow-bellied Racer (Coluber constrictor mormon) snake held by biologist, Pescadero, California

Eric Baccega / Guards capturing Peruvian boa (Boa constrictor ortonii) Chaparri Ecological Reserve, Peru, South America

Tony Phelps / Boa Constrictor {Boa constrictor constrictor} head portrait with tongue flicking, Captive, from south America

John Cancalosi / Boa Constrictor (Boa constrictor) juvenile, Sonora, Mexico

Shattil & Rozinski / Yellow bellied racer snake {Coluber constrictor} emerging from hole in log, Colorado, USA

Tim Fitzharris / Boa (Boa constrictor constrictor) on tree trunk, Costa Rica

Pete Oxford / Boa Constrictor (Boa constrictor), Loja, Ecuador

Thomas Marent / Boa Constrictor (Boa constrictor) flicking tongue to taste surroundings, French Guiana

Pete Oxford / Boa constrictor {Constrictor constrictor columbianus} amongst leaf litter, South America

Nick Garbutt / Madagascar boa constrictor {Acrantophis madagascariensis} Lokobe Reserve, North West Madagascar

LYNN M. STONE / Boa constrictor {Constrictor constrictor} captive

LYNN M. STONE / Rainbow boa constrictor swallowing rat {Epicrates cenchris} captive

LYNN M. STONE / Boa constrictor {Constrictor constrictor} captive

Ross Couper-Johnston / Argentine boa {Boa constrictor occidentalis} climbing tree, Argentina, Ibera marshes.

Luiz Claudio Marigo / Boa constrictor in tree {Constrictor constrictor} Amazonas, Brazil

Luiz Claudio Marigo / Boa constrictor in tree {Constrictor constrictor} Amazonas, Brazil

Todd Pusser / Southern black racer {Coluber constrictor priapus} coiled under log, North Carolina, USA

Todd Pusser / Southern black racer {Coluber constrictor priapus} North Carolina, USA

Barry Mansell / Southern black racer snake {Coluber constrictor priapus} Florida, USA.

Pete Oxford / Boa Constrictor (Boa constrictor) preparing to molt, Machalilla National Park, Ecuador

ZSSD / Boa (Boa constrictor constrictor) mass of babies, native to South America

Michael & Patricia Fogden / Boa Constrictor (Boa constrictor) coiled on buttress root, rainforest, Costa Rica

Michael & Patricia Fogden / Boa Constrictor (Boa constrictor) coiled on buttress root, rainforest, Costa Rica

Pete Oxford / Boa Constrictor (Boa constrictor) at the edge of a stream, Ecuador

Pete Oxford / Boa Constrictor (Boa constrictor) climbing buttress root, Ecuador

Pete Oxford / Boa Constrictor (Boa constrictor) climbing buttress root, Ecuador

Pete Oxford / Boa Constrictor (Boa constrictor) climbing buttress root, Ecuador

Pete Oxford / Boa Constrictor (Boa constrictor) crossing a stream, Ecuador

Michael & Patricia Fogden / Boa Constrictor (Boa constrictor) portrait in the rainforest, Costa Rica