Broadly the conservation strategies are divide into two types . They are:

  • On Site Preservation
  • Off Site or Ex Situ preservation
On Situ Preservation

The best strategy to conserve species is to preserve them in wild in their natural communities. This is known as π or On site preservation. Natural communities are evolutionary adapted to the changing environment. In the wild species genetic variability is not lost by genetic drift. But on site preservation is not suitable for many rare and endangered species. They go extinct due to many reasons ass described in earlier posts. These are: genetic erosion, deteriorating habitat, changes in environment, competition from exotic species, disease and excessive hunting.

Ex Situ or Off-Site Preservation

When the remaining population is too small or when the individuals are found outside the protected area than on site preservation may not be effective. Than the species are preserved in an artificial condition under human supervision. This strategy is known as off site or ex situ preservation. A number of species that have extinct are already grown in captivity e.g. Elaphurus Davidianus and Equus caballus przewalski. 

Ex Situ Facilities for animal preservation are:
  • Zoos
  • Game Farms
  • Aquaria
  • Private Breeders
Ex Situ Facilities for plants preservation are:
  • Botanical Gardens
  • Arboreta
  • Seed Banks
The strategy that combines these two strategies is the protection of rare and endangered species in small protected areas. The species are somewhat wild but human intervention is necessary there to prevent loss of species.
Long term ex situ conservation reduce the need of research and display of wild collected individuals. In situ preservation is necessary for the conservation of those species that are difficult to raise in captivity or in zoos or botanical gardens.

Ex Situ Conservation Limitations in Comparison with In Situ Preservation

1. Population Size

To prevent genetic drift several hundreds of populations need to be maintained in ex situ preservation. No zoo can preserve such large quantity of animals and only few animal species could be kept in captivity. In botanical garden one or few individuals of species could be maintained.

2. Adaptation

Ex situ populations may have genetic adaptations when kept in captivity for several generations due to changes in their mouth parts and digestive systems by the food of zoo. When these animals are returned to wild they might not adapt to eat their natural food in wild.

3. Learning Skills

Learning skills could not be develop in to captive bred individuals. When they are returned to wild they are not able to find their food, they can not judge their predators and not know how to compete with them. The problem is worse in social animals in juveniles who learn from their parent members in their group. 

4. Genetic Variability

Ex situ conserved species have limited gene pool. The species collected from warm low land areas for captivity may not be able to adapt for cold in cold high land areas.

5. Continuity

This conservation needs continuous supply of funds and institutional policy. Frozen, chilled collection of sperms, eggs, seeds and tissues are affected by loss of electric power. 

6. Concentration

Ex situ efforts are done at smaller places. There is a danger to the entire population when any disaster come.

7. Surplus Animals

Surplus animals could not be kept in captivity. In zoo only few species can be bred. 

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