Question: How do you weigh a baby snake? Answer: very carefully…

by ZSL on

Our doors may be closed to the public, but behind our gates life goes on as normal for the 20,000 animals in the care of ZSL’s dedicated zookeepers.

Senior keeper Daniel Kane takes us into the iconic Reptile House for a health check on our newest arrivals – five recently hatched bushmaster snakes.

In October, the herpetology team at ZSL London Zoo celebrated the arrival of five baby bushmaster snakes, watching them safely hatch one by one in the Reptile House, over the course of three exciting days. 

It was the first time bushmasters, which are a type of pit viper, have hatched at a UK zoo, so the eggs got a lot of attention from the keepers during the 76-78 day incubation period – and now we’re pleased to say they’ve just passed their first health check with flying colours.

The eggs were laid during the first lockdown, while ITV were at the Zoo filming the documentary London Zoo: An Extraordinary Year (still available on the ITV Hub), so they’ll also go down in ZSL history for being lockdown babies. 

These healthy young snakes are large as far as most hatchling snakes go, each weighing between 64 and 70g - already as much as an adult song thrush - and will likely weigh up to 4 kg when they reach adulthood.

All five snakes have already sloughed their skin for the first time and accepted a couple of meals each – two great milestones in any young snake’s life.

bushmaster snake in a box

The parents of these young bushmasters arrived at the Reptile House as juveniles in 2016 so that the ZSL team could learn more about the needs of this amazing species - about which little is known - and share important knowledge about their care.

We’ve learnt a lot in those four years.

While Central American bushmasters are native to the low hilly rainforests of Nicaragua, Costa Rica, and Panama, with their year-round tropical climate, the species thrives in relatively cooler temperatures between around 18 – 25°C.

This is because they spend almost every day hidden in a tight-fitting hide, usually in the form of a disused armadillo burrow or a rotten log, where temperatures are far cooler than in the surrounding land. 
By living this more secretive life deep in the rainforest, bushmasters probably avoid competition with the similar lancehead vipers (Bothrops spp.), which prefer much warmer temperatures, such as those found in forest clearings and human settlements.

Also, despite bushmasters’ requirement for a high-humidity environment, they also need somewhere perfectly dry to sit during the day and overnight to remain comfortable and healthy – a potentially complicated environment that the ZSL team worked hard to perfect.

Bushmaster snake with eggs

How will this breeding success impact the species?

All four species of bushmaster are assessed by the IUCN as ‘Data Deficient’ meaning scientists do not yet know enough about their wild status to reach an informed decision regarding their conservation status.

Vital knowledge gained by keepers at ZSL London Zoo from caring for the parents, accurately replicating their wild climate, and a successful incubation, can now be shared with others in the zoo community looking to care for the same or similar species – vital information for collaborative global conservation breeding programmes.

We also hope to apply what we have learned here to something called a conservation needs assessment for the species - an important precursor to a formal IUCN assessment, which is in turn a vital tool for prioritising conservation action. 
Working collaboratively with conservationists and herpetologists to improve animal care and inform conservation fieldwork is a key part of international conservation charity ZSL’s work – as is educating the public:

There are only 21 other Central American bushmasters in zoos around the world, making this a very rare snake to see – so make sure to look out for the parents of these juveniles in the Reptile House once its doors can reopen. 
The five youngsters will live behind the scenes for a little while longer - getting the expert care they need - before moving on to another good zoo, so that the international zoo community can continue to share knowledge about their needs and care.

Having to close our doors for the second time has put ZSL under immense strain, following the toughest year in our almost 200 year history. Please help us continue vital work like this, by donating at, becoming a ZSL member or buying a gift ticket for a future visit. Everything helps.

snake up close

Quick facts

  • The Four species of bushmasters are native to Central and South America and are jointly the world’s longest vipers, reportedly growing past the 3m mark – although 2-2.5m is more normal.
  • Being pit vipers they have a heat sensitive organ between each eye and nostril with which they accurately discriminate between temperatures as little as 0.001°C from as much as several metres away, aiding in both prey and predator detection.
  • They are quite unusual for vipers in that they lay eggs whereas most other vipers, including all known American vipers, give birth to live young.
  •  Bushmasters feed primarily on mice and rats - quite small prey considering the size these snakes grow to. Possibly this is to avoid competition with other vipers in the same habitat which do eat larger rodents, or because in their relatively cool microhabitat down armadillo burrows, they would not be able to digest a large meal quickly enough. 
  •  Although quite widespread, we really do not know what the wild situation is for bushmasters, but all species seem to be dependent on relatively undisturbed rainforest and are quite strongly associated with burrows of animals such as armadillos where they rest during the day. Loss of large areas of intact forest and associated fauna and microclimates is likely to have a negative effect on these culturally significant species.
  • Some indigenous people living in the habitat of the bushmaster say the snake calls for a mate by emitting a high-pitched whistle – making it easy for people to avoid accidentally encountering one! As well as this there are several military vehicles and pieces of equipment named after this amazing snake, as well as two fictional characters in the Marvel universe.

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