Tamarins are small primates from the forested areas of South America. There are many species of Tamarin, some of which are restricted to a very small geographical area. Habitat destruction and collection for laboratories, or the pet trade have brought many species to the brink of extinction.

In such a large continent, there is still much to be learned and to discover, particularly in tropical rain forests where survey conditions are difficult.

Tamarins drink sap from trees by scoring the bark and leaves with their long incisor teeth. They are classified as dangerous under the UK Dangerous Wild Animals Act because they can also inflict a savage bite with these incisors. When defending babies, in particular, males can be utterly fearless.

Tamarins live in family groups of 1 or 2 generations, plus the original pair. When 2 or 3 young are born, they are carried around, groomed and generally looked after by the male, moving back to the female to suckle.

Cotton-top tamarins are endangered in the wild. In captivity they have been bred into many generations, and are the subject of an international captive breeding effort. In captivity at least, the Cotton-top Tamarin is in no danger on extinction, and families could be available for reintroduction should it be deemed appropriate.

When we first started to keep this species in 1972, cotton-tops were classified as Vulnerable Endangered Species, whose number had fallen to dangerously low levels. Some estimates put this at about 500 individuals, with very few in captivity. The principal cause of this was over-collecting in the wild for laboratories, with a few going into the pet trade (mainly in other countries, rather than the UK).

In the intervening quarter of a century, a sustained effort has been made around the globe to propagate this attractive species - with startling success. University Psychology departments and laboratories have bred many thousands, whilst hundreds more have been bred in zoos. By the early 1980s when a 'Captive Breeding Management Protocol and Studbook' was set up, there were so many cotton-tops available in captivity that space was becoming a problem.

Space is a problem if, either the animals are over-crowded (they usually live in small family units), or cotton-tops are taking up resources (of space and staff) which could be utilised for a more critically endangered species of marmoset or tamarin. To manage the population properly, studbook keepers were established, and the population was demographically 'mapped', i.e., laid out in family trees. From this it was possible to work out the degree of in-breeding in the different 'families', and whether there were animals available which had not bred - or not bred enough - to widen the genetic base of the captive population. In this way the maximum possible genetic variation could be 'built in' to the captive population.

Once this demographic analysis had been carried out it soon became clear that some families (often originating from laboratories) were 'over represented', i.e., had bred too successfully, and were distorting, through their numbers, the genetic 'family-tree', or pyramid. If this was allowed to remain, the eventual outcome would be a loss of genetic variation in the population. This might even be described as an unnecessary loss of genetic variation, unnecessary because it is within our powers, collectively, to do something about it. That ‘something’ is to instruct those zoos with 'over-represented' blood-lines to slow up or (in some cases) to stop breeding altogether, whilst maximum effort was put into 'under-represented' lines. This is quite a difficult concept to 'sell' to some members of staff, zoo societies and volunteers (never mind the media), especially where the species as a whole, is still described as an 'Endangered Species', and especially a species such as the cotton-top for which, only a decade or so earlier, we had been receiving pats on the back for breeding at all!

After we were informed that our 'family' was, indeed, of an over-represented line, we asked the studbook keeper if we could re-home them to a collection which would be happy to maintain them primarily for exhibition purposes, whilst we kept instead a pair from an under-represented line. A few months later the swaps were arranged, and that is the line that we have been maintaining ever since.

Marmosets and tamarins are fairly straightforward to maintain in captivity. In laboratory animal houses they are housed in large, metal cages, about 1.2 metres in length, and they breed very well under these conditions. In common with most zoos we prefer something much larger and more naturalistic, with heavy planting in the outside enclosure and numerous next-boxes. Ideally, we would like to keep them at semi-liberty, though this has to be carried out with some care.

Tamarins differ from marmosets in at least one important respect; they possess large canine teeth. These suggest a different diet, and this is indeed so, because the teeth are used to score the bark of trees so the running sap can be licked up. These large teeth have other uses too; a possessive male tamarin resenting the approach of a keeper near his mate may have no hesitation in making his displeasure felt, with a couple of searing bites which, if he has jumped onto your head or shoulder at the time, is no laughing matter!

In common with the other members of this primate ‘family’, after the 1-3 young have been born they spend most of their time clinging to their father, crawling back to the female only to be suckled. A pair, and two or three litters of offspring - in total some 10 to 15 animals - are usually the maximum size of group which would be encountered in the wild.

The Cotton-Top Tamarins in the small primates house are an example of a successful reintroduction programme. Coming from South America where their numbers were greatly reduced a successful breeding programme in captivity has enabled many to be released back into the wild in suitable reserves.