While babies can be housed in glass aquariums, larger snakes will need a custom enclosure, either commercially purchased or constructed at home. Boa constrictors are very powerful and will escape given a chance, so enclosures must be very secure. Cage size for an adult is around 6-8 feet long, 2-3 feet wide, and 2-3 feet tall. The minimum is about 10 square feet of floor space (for a single snake). Remember, this large cage should be easy to clean, and you must be able to maintain it at high temperatures.
A variety of substrates can be used. For young snakes, lining the cage with paper or paper towels is the best option for easy cleaning. For adults, paper can also be used, as can something like indoor/outdoor carpeting (e.g. Astroturf). The benefit of carpeting is that two or more pieces can be cut to fit and a soiled piece can simply be replaced with a spare, and the soiled piece can then be thoroughly cleaned and disinfected. Reptile bark can be used, although it gets to be more expensive. The use of wood shavings is probably best avoided to avoid irritation and accidental ingestion (which can cause impactions). If wood shavings are used, a separate enclosure should be used for feeding and cedar shavings should always be avoided (can cause skin irritation and repiratory problems).
Boa constrictors come from tropical climates, and warm temperatures in the cage are essential. During the day, a temperature gradient between 82-90 F (28-32 C) should be maintained. In addition, a basking spot of 90-95 F (32-35 C) should be provided. At night, temperatures can drop to 78-85 F (26-30 C). The temperatures are critical, so get some accurate thermometers and measure in several locations of the cage (warm end, cooler end, basking spot). A combination of incandescent bulbs, ceramic heating elements, and heating pads can be used to maintain the temperature (follow manufacturer's recommendations precisely). Any bulbs or heating elements in the cage must be shielded to prevent burns, to which snakes are quite susceptible. Hot rocks should never be used.
Humidity and Water
The humidity level can usually be maintained with a large bowl of water in the cage, and a heat source nearby will help evaporation to increase humidity. The snake will likely climb into the bowl for baths so make sure it is sturdy. It should be cleaned regularly, and snakes will often defecate in the water so keep a close eye on the cleanliness of the water. A warm bath can help with the shedding process.
Hides are essential to make snakes feel secure, and a minimum of two should be provided - one at each end of the temperature gradient. Hides can be half logs, commercial reptile caves, upside down plastic containers with a hole cut in the side, or even cardboard boxes. Make sure they are not much larger than the snake, as a close fit will help the snake feel secure. They should be cleaned (or replaced in the case of cardboard boxes) when they become soiled.
A cleaned and sterilized tree branch heavy enough to support the snake's weight should also be provided. Soak it in a bleach solution, rinse very well and dry thoroughly before adding to the cage.
As a rule, younger snakes should be fed more frequently than adults. Smaller snakes can be feed every 5-7 days, intermediate snakes every 10-14 days, and full grown snakes every 3-4 weeks. Feeding should be adjusted to maintain a good body condition in your snake. Keep in mind that many snakes in captivity are overfed, and obesity can be a problem. Hatchling snakes can be fed mice, moving up to rats and then rabbits (one per feeding) as the snake grows larger. An adult will eat a few rats at a meal, or one rabbit.
Never feed a snake a prey item larger than the widest part of the snake. Also, avoid handling the snake for at least 24 hours after a meal, or regurgitation might occur.
Generally boas like to hide with their prey to eat it. Don't be surprised if your snake disappears into a hide with its meal and you don't see it for a while. It is a good idea to feed snakes in a separate enclosure, so that the snake only associates feeding with that location and is less likely to mistake your hand for food everytime you put your hand in the cage. An opaque enclosure will help a boa feel secure while eating.
Feeding time is the time when most care is required handling boa constrictors (as with any other snake). Do not feed by hand (increases risk of accidental bites), and since boa constrictors hunt primarily by their sense of smell, wash your hands really well after handling food, or the snake might strike at your hand. A handling stick can help push the snake away from the cage door at feeding time to help prevent problems.