Captive Breeding and Release Programmes

Captive Breeding and Release Programmes

1. Factors that influence the decisions around CB+R programmes

   • Is there a genetically diverse captive population?
   • Is release into the wild likely to be successful, now or in the future?
   • Is the wild population threatened?
   • Is keeping a captive population realistic?
   • Is in-situ conservation being successful?

2. Habitat requirements for keeping species in captivity:

   • Financial constraints: keeping animals in zoos/plants in botanic gardens is expensive. There isn't enough money available to keep all endangered animals in captivity.
   • Food requirements: some species have feeding requirements that cannot be easily provided.
     • E.g. insectivorous bats/fish that eat plankton
   • Habitat size: some species require such large habitats that they cannot be kept in captivity.
     • E.g. Whales
   • Species interrelationships: some species have complicated interrelationships.
     • E.g. plants with specific pollinators/ the large blue butterfly that overwinters in ants nests

3. Factors that may inhibit the success of captive breeding programmes:

   • Conditions for breeding – for many species, the precise timing for breeding is vital to increase their young’s survival chances. Conditions for breeding often require day length, light level, temperature, or food stored in the body.
   • Population interactions and breeding success – In captivity, the mixing of breeding and non-breeding individuals may cause conflict and reduce the survival of offspring (common in bird species). Some species also breed most successfully if there is a choice of possible partners, but some species mate for life.
   • Breeding habitat – Some species can only breed if they have a suitable habitat, e.g. one that has a suitable site for courtship display, social grouping, a nest site, or a hunting area.
     • Flamingos only breed in large groups. Mirrors around a captive population give the illusion of a larger population.
   • Gene pool size – Most captive breeding programmes have small gene pools, increasing the risk of inbreeding. A ‘stud book’ can be used to keep a record of family trees.
     • The Hawaiian Goose became rare due to hunting, habitat loss and introduced predators. The captive breeding program, while it has been successful in increasing the wild population, only started with 7 individuals. Inbreeding meant that some goslings had low survival in cold weather.
   • Hybridisation – In captivity, species may interbreed with closely related species they may not have met in the wild. This is a particular problem with plants (pollen carried by insects/wind. If hybridisation occurs, then the offspring will have a combination of characteristics and would have no conservation value. It is likely that the offspring would also not be adapted for survival.
     • The African Lion and the Asiatic Lion

4. Methods of increaseing breeding success:

   • Micro-propagation of plants – a form of tissue culture where many clusters of cells can be produced from a single plant/tissue sample. Each cell cluster can be cultivated to produce an individual plant. This way, many plants can be produced from a single parent plant. All plants produced are genetically identical.
   • Cryopreservation – storage of eggs, semen, and embryos by freezing for future use. They can be transported more easily than parent animals, and means the parents never have to meet.
   • Artificial insemination (AI) – a collection of semen from a male is inserted into a female. Avoids problems such as the parent animals living in different zoos, risk of injury through natural mating (often dangerous for large animals), and the potential partners not accepting each other.
   • Embryo transfer – some mammal captive breeding populations have very few breeding females. The female of the endangered species receives hormone treatment. The eggs are then washed out and fertilised with sperm from a male. Each embryo is implanted into a female of a closely related species (a surrogate mother), and they give birth to the other species offspring. This way, more offspring can be produced.
   • Cloning – only had limited success with livestock breeding, but not yet with wild animal species. It involves the production of embryos by transferring the nucleus from a stem cell of the endangered species into an empty egg cell of a closely related species. This egg is placed into a surrogate mother of a closely related species, and a baby of the endangered species is born. One day it may be possible to produce young from species who do not currently breed. Cloning can also be used for plants by cultivating cuttings (can avoid hybridisation).

5. How can we ensure the release site is suitable?

   • Having a large, suitable habitat
   • Reliable food supplies
   • Low predation risk
   • Suitable breeding sites
   • Water
   • Support of the local human population

6. Post-release Support and Monitoring

   • Hard release: releasing animals with no post-release support. It usually involves species where behaviour is controlled by instinct so that the individuals do not need to learn survival skills.
     • E.g. insects, fish, reptiles and amphibians.
   • Soft release: post-release support such as a gradual release into larger areas and the provision of food as they learn how to find it for themselves.
     • Often necessary for the release of mammals and birds.

7. What problems may animals face once they are released?

   • Finding and recognising food
   • Being accepted into the social groups of the wild population
   • Developing hunting skills (captive-bred predators are often born to parents who were also bred in captivity, so they lack the hunting skills for live prey they need to pass on to their offspring)
   • Recognising and avoiding predators
   • Recognising poisonous foods