Tim provided two excellent sources (I use both on a regular basis). Here's how we keep our Gaboon (a very large female) that is on exhibit at my wildlife center:
Enclosure: Currently in a 5' wide x 3' deep x 2' high cherry wood custom cage by Crescent Moon Creations. The cage is lined by contact paper on the interior and all seems are caulked with non toxic caulk.
Set up: We provide 3-4" of soil, forest humus, and leaf mulch (all stirred together). We then place 3-4" of dried oak leaves on the surface. This not only looks fantastic but the leaves help to trap the soil's humidity and moisture levels (kept dry but does retain moisture). Gaboons love to just partially bury themselves in leaves. Once every other week I stir up the substrate to keep it oxygenated; doing this will allow you to not have to continually change the substrate; it will last a LONG time. For water, we provide a large, shallow plastic planter saucer. Contrary to popular beliefs, you do not have to soak your gaboon every week; mine have never, ever been soaked and they have done just fine for many years.
Humidity: We heavily mist the cage every other day or even every third day. Between this and a steady source of easy to get to water (as stated above), your snake will do fine. They WILL find the water source. Having the right substrate also helps quite a bit.
Heat/Light: Our exhibit is heated by a Pro Product Radiant Heat Panel connected to a Spyder Robotics thermostat. Basking temperatures reach 90 degrees F. for 8 hours per day but the snake always has areas in its cage where temps drop to the low to mid 70's. Without a cooler area, your gaboon will NOT do well (regurge, death). A healthy gaboon will move back and forth (you'll notice after a big meal that they will spend more time basking). Night temps drop to around 74-78 degrees (thermal gradient). Light is provided by a Zoo Med fluorescent full spectrum....shows off the colors very nicely.
Feeding: our big girl gets one jumbo rat PER MONTH. These snakes have very slow metabolisms and its easy to over feed them. Every snake is different so you need to keep an eye on overall appearance. ONLY USE LONG TONGS when feeding these snakes. They may look sluggish, but they have lightning fast strikes that can reach quite a distance. This is the single most important factor when keeping this species safely. NO MISTAKES (and have a good source of A/V in your area). I do supplement with vitamins every third feeding as we do feed only frozen/thawed prey.
There's much more involved but these are the Cliff Notes version.
Rob Carmichael, Curator
The Wildlife Discovery Center
>>I am planning on getting a Gaboon Viper in the future and was wondering about their enclusure reqirements. Is a four foot long by two feet deep by two or three feet high appropriate? Also, what are their humidity and tempereature requiements? Are there any good books about keeping Gaboons in captivity?
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Rob Carmichael, Curator
The Wildlife Discovery Center at Elawa Farm
Lake Forest, IL