Captive Breeding and Release

Why Captive Breeding?

In the ideal world there would be ample habitat for animals to spread naturally into it - and even if it were not continuous, thus preventing that natural expansion, populations would be healthy and secure enough to allow animals to be taken from them and translocated to new habitat. Sadly, this is not the case. All existing populations are under threat. Most translocations which take place arise out of rescuing animals whose habitat is in the way of some new development of over-riding economic or social importance.

So, we have to consider alternative means of ensuring that we have animals available to populate habitat as it is restored to suitable condition. This helps to increase populations and locations and thus secure the future of the animals. The best of these alternative means is captive breeding. Adequate numbers of animals can be produced to start new populations without imposing significant pressures on existing populations.

Successful breeding programmes have been carried out with the Natterjack Toad and recently London Zoo have experimented with the Smooth Snake. However, the most outstanding of the captive breeding programmes for the British reptiles and amphibians is that for the Sand Lizard. It is that programme which we will give some more detail of to illustrate its effectiveness.

The Sand Lizard

The Sand Lizard serves admirably to illustrate the advantages of captive breeding. In the wild, the eggs are exposed to many dangers. Unseasonable weather changes can dry them out or cause them to hatch too late for the young to survive or, indeed not to hatch out at all. Even just one mountain biker or horse rider riding along a sandy track can destroy several clutches of eggs. Possibly because many populations are small and isolated, resulting in inbreeding, viability of eggs can sometimes be lowered. As little as half the eggs laid might hatch even in a reasonably good year after these factors are taken into account.

Once the young do hatch they are small and extremely vulnerable to many sorts of predator and are faced with the task of getting as much food as possible in the few short weeks before hibernation. The consequence of these and other pressures are that only about 5% of these youngsters survive to maturity.

Conversely, with captive breeding in well managed vivaria hatch rates are much higher. The young hatch earlier and are well fed before release, with a longer period in which to eat further and establish themselves in a hibernaculum ready for the rigors of winter. As a consequence, survival rates are much higher and frequently maturity is reached a full season earlier.

The Chester Zoo Vivarium - A public display vivarium hosting a breeding colony of the extremely rare Merseyside race of Sand Lizard. (c) Chris Davis

As part of the Sand Lizard Species Programme, HCT co-ordinates the breeding and release programme which involves a number of vivaria run by skilled herpetologists in both private gardens and zoos. All three of the British races of Sand Lizard are maintained. As a direct consequence of this programme, several new populations of the Dorset race have been introduced, helping to not only secure its status but to expand. The Wealden race has also benefited greatly and is now restored to much of its former range. In 1995 a drive towards improving the situation with the rarest of the races - the Merseyside race started. Since then there have been some releases within newly secured habitat in Merseyside but there has been an extremely successful re-introduction into North Wales after an absence of some 50 years. The animals are now well established with a vibrant growing population at this first site. Further new sites for all three races have been identified and the releases continue.

The releases also offer a superb education opportunity enabling local volunteers and enthusiasts who might never have seen a Sand Lizard the opportunity of doing so as well as frequent media coverage to raise public awareness of these beautiful animals and their plight.

The Sand Lizard Captive Breeding and Reintroduction Programme stands out as an example of the best in this particular form of wildlife restoration.