TIGER MANAGEMENT OF CAPTIVE POPULATIONS - A SCIENTIFIC APPROACH
Of all the big cats, or perhaps of all endangered species, the tiger may be both the most charismatic and the most feared.
-Stephen J. O’Brien
Chief of the Laboratory of Genomic Diversity
Problems with AZA Breeding Strategies
- Based on subspecies and ‘standard’ tiger characteristics
- Reduced population size causes increased genetic drift and inbreeding
- Increased extinction risk due to smaller isolated populations
There are several important aspects of the AZA breeding strategy that is not consistent with the goal of maintaining healthy tigers in the long term. The AZA has a viewpoint on tiger management that is dictated by the current subspecies designations and seeks to eliminate variants that do not have the “classic” tiger appearance. This plan is good for achieving a narrow-minded image of what a tiger should look like, but will not result in large healthy tiger populations that capture all of the standing genetic diversity that is present in tigers that are alive today. It is somewhat like establishing dog breeds; it is fine if you want to get a certain type of animal, but is not a good strategy for maximizing diversity and fitness. As described in the previous section, the original variation of subspecies has not been sufficiently studied and therefore the subspecies classification by Luo is based on limited sampling and may not be valid. There is much variation in the appearance of tigers that should be preserved and there are also rare variants that one day may become adaptive. Even if there is a typical “classic” appearance that zoos and other organizations want to promote, there are rare variants that are also a very important part of the tiger’s legacy and future adaptive potential, such as white tigers. These also need to be maintained and protected. Further, the AZA calls for eliminating, or sterilizing, “generic” tigers. These are tigers of either unidentified or mixed ancestry. Yet, most tigers in the captive population are generic. This would be a huge loss to the tiger population, not only in the loss of individual tigers, but also in terms of losing genetic diversity. This AZA ant-generic tiger policy greatly increases extinction risk of captive tigers and negatively affects the future of the species.
The Species Survival Trust’s Breeding Strategy Maintains Healthy Tiger Populations
- Preserve genetic diversity including rare variants
- Maintain high breeding population size
- Prevent inbreeding
- Prevent genetic drift (loss of variation)
The number one goal of tiger management and breeding should be to maintain healthy tigers. We have developed a science-based tiger management program implemented by the Species Survival Trust (SST). The first goal of the SST’s breeding plan is to maintain healthy tiger populations. The breeding strategy is based on minimizing inbreeding and genetic drift in order to reduce loss of variation and preserve genetic diversity, including rare variants. This is done by maintaining the maximum breeding population size and selecting breeding pairs using genetic and health information to maximize diversity. In addition, in cases where a particular trait is desired, this plan uses the genetics to determine what mating pair would provide the greatest genetic diversity ensuring healthy cubs. The SST plan will preserve genetic diversity of tigers, including both common and rare variants. The SST strongly opposes rules that call for only breeding tigers for specific traits or taxonomic classification, and eliminating healthy tigers from the breeding program. Tiger breeding and management should be done in a way that maintains genetic diversity and health of this species and ensures its future survival. There are several very successful conservation breeding programs that bred animals of different subspecies. These include the recovery programs for black-footed ferrets, Florida panthers, Attwater’s prairie chicken, and Mexican wolves. These programs were successful in producing individuals with higher fitness and this was a result of increasing diversity. Similarly, the SST breeding program seeks to maximize diversity and fitness of tiger populations.
The solution to managing many of our wildlife dilemmas is to repeal misguided laws.
Founder, Small Cat Conservation Alliance