The key to survival in the tropics is comfort. If your boots fit, your clothes don't itch, your wounds don't fester, you have enough to eat and you have the comforting presence of a local who is at home in the environment, then you are not likely to go far wrong.

Of course, jungle warfare is something else. The British, Americans and, for all I know, several other armies, have produced detailed manuals on how to survive under the most arduous conditions imaginable and with the minimum of resources. But most of us are extremely unlikely ever to find ourselves in such a situation. Even if you are unlucky enough to be caught in a guerrilla war or survive an air crash in the jungle, I believe that the following advice will be as useful as trying to remember sophisticated techniques that probably require equipment you do not have to hand anyway.

A positive will to survive is essential. The knowledge that others have travelled long distances and lived for days and even months without help or special knowledge gives confidence, while a calm appraisal of the circumstances can make them seem far less intimidating. The jungle need not be an uncomfortable place, although unfamiliarity may make it seem so. Morale is as important as ever, and comfort, both physical and mental, a vital ingredient.

Clothing and footwear

To start with, it is usually warm, but when you are wet, especially at night, you can become very cold very quickly. It is therefore important to be prepared and always try to keep a sleeping bag and a change of clothes dry. Excellent strong, lightweight plastic bags are now available in which these items should always be packed with the top folded over and tied. These can then be placed inside your rucksack or bag so that if dropped in a river or soaked by a sudden tropical downpour - and the effect is much the same - they, at least, will be dry. I usually have three such bags, one with dry clothes, one with camera equipment, notebooks, etc., and one with food. Wet clothes should be worn. This is unpleasant for the first ten minutes in the morning, but they will soon be soaking wet with sweat and dripping in any case, and wearing them means you need carry only one change for the evening and sleeping in. It is well worth taking the time to rinse them out whenever you are in sunshine by a river so that you can dry them on hot rocks in half an hour or so. They can also be hung over the fire at night, which makes them more pleasant to put on in the morning, but also tends to make them stink of wood smoke.

Always wear loose clothes in the tropics. They may not be very becoming but constant wetting and drying will tend to shrink them and rubbing makes itches and scratches far worse. Cotton is excellent but should be of good quality so that the clothes do not rot and tear too easily. There are now many excellent specialist manufacturers of tropical clothing. Some are expensive, but it is worth investing in good quality for comfort and durability. One of the best suppliers is Nomad Camping at 3 Turnpike Lane, London N8 (tel 020 8889 7014).

For footwear, baseball boots or plimsolls are usually adequate, but for long distances good leather boots will protect your feet much better from bruising and blisters. In leech country, a shapeless cotton stocking worn between sock and shoe tied with a drawstring below the knee, outside long trousers, gives virtually complete protection. As far as I know, no one manufactures these yet, so they have to be made up specially, but they are well worth it.

Upsets and dangers

Hygiene is important in the tropics. Small cuts can turn nasty very quickly and sometimes will not heal for a long time. The best protection is to make an effort to wash all over at least once a day if possible, at the same time looking out for any sore places, cleaning and treating them at once. On the other hand, where food and drink are concerned, it is usually not practical or polite to attempt to maintain perfectionist standards. Almost no traveller in the tropics can avoid receiving hospitality and few would wish to do so. It is often best therefore to accept that a mild stomach upset is likely - and be prepared. There is an excellent medical section in this book with the best up-to-date advice on prevention and cure of all the illnesses to which travellers in the tropics are likely to be exposed and they should read it carefully. However, constant use of prophylactics and antibiotics can produce side-effects. Many of us now use homeopathic remedies, including malaria pills, while carrying conventional cures as well. Try Ainsworths of 36 New Cavendish Street, London W1M 7LH (tel 020 7935 5330, fax 020 7486 4313, email enquiries@ainsworths.com, internet www.ainsworths.com), which has a good travel kit.

In real life-and-death conditions, there are only two essentials for survival, a knife or machete and a compass (provided you are not injured, when, if possible, the best thing to do is to crawl to water and wait for help). Other important items I would put in order of priority as follows:

There are few tropical terrains that cannot be crossed with these, given time and determination. Man can survive a long time without food, so try to keep your food supplies simple, basic and light. Water is less of a problem in the jungle, except in limestone mountains, but a metal or lightweight plastic water container should be carried and filled whenever possible. Rivers, streams and even puddles are unlikely to be dangerously contaminated, while rattans and lianas often contain water, as do some other plants whose leaves may form catchments, such as pitcher plants. It is easy to drink from these, though best to filter the liquid through cloth and avoid the 'gunge' at the bottom.

Hunting and trapping are unlikely to be worth the effort to the inexperienced, although it is surprising how much can be found in streams and caught with hands. Prawns, turtles, frogs and even fish can be captured with patience and almost all are edible - and even tasty if you're hungry enough. Fruits, even those that are ripe and being eaten by other animals, are less safe, while some edible-looking plants and fungi can be very poisonous and should be avoided. Don't try for the honey of wild bees unless you know what you are doing as stings can be dangerous and those of hornets even fatal.

As regards shelter, there is a clear distinction between South America and the rest of the tropical world. In the South American interior, almost everyone uses a hammock. Excellent waterproof hammocks are supplied to the Brazilian and US armies and are obtainable commercially. Otherwise, a waterproof sheet may be stretched across a line tied between the same two trees from which the hammock is slung. Elsewhere, however, hammocks are rarely used and will tend to be a nuisance under normal conditions. Lightweight canvas stretchers through which poles may be inserted before being tied apart on a raised platform make excellent beds and, once again, a waterproof sheet provides shelter. Plenty of nylon cord is always useful.

Fight it or like it

The jungle can be a frightening place at first. Loud noises, quantities of unfamiliar creepy-crawlies, flying biting things and the sometimes oppressive heat can all conspire to get you down. But it can also be a very pleasant place if you decide to like it rather than fight it - and it is very seldom dangerous. Snakebite, for example is extremely rare. During the 15 months of the Royal Geographical Society's Mulu expedition, in Borneo, no one was bitten, although we saw and avoided or caught and photographed many snakes and even ate some! Most things, such as thorns, ants and sandflies, are more irritating than painful (taking care to treat rather than scratch usually prevents trouble).

Above all, the jungle is a fascinating place - the richest environment on earth. The best help for morale is to be interested in what is going on around you and the best guide is usually a local resident who is as at home there as most of us are in cities. Fortunately, in most parts of the world where jungles survive, there are still such people. By accepting their advice, recognising their expertise and asking them to travel with you, you may help to reinforce their self-respect in the face of often overwhelming forces that try to make them adopt a so-called 'modern' way of life. At the same time, you will appreciate the jungle far more yourself - and have a far better chance of surviving in it.