What is an SSP?
The Species Survival Plan, or SSP, began in 1981 as a cooperative population management and conservation program for selected species at North American zoos and aquariums. Each SSP manages the breeding of a species to maintain a genetically and demographically healthy, self-sustaining captive population. SSPs include other conservation activities such as research, education, reintroduction, and field projects. Currently, 113 SSPs covering 181 individual species are administered by the Association of Zoos and Aquariums (AZA).

Minnesota Zoo and the Tiger SSP
The Tiger SSP began as a captive management program for Amur tigers—the subspecies of tiger we have at the Minnesota Zoo. Dr. Seal coordinated this plan until 1987 when he became Tiger SSP coordinator for all tiger subspecies managed in North America including the Amur tiger, the Sumatran tiger, and the Malayan tiger. Dr. Ron Tilson, current Conservation Director at the Minnesota Zoo and one of the world's leading tiger experts, took over as Amur tiger coordinator in 1987. Since 1992, he has served as both the Tiger SSP coordinator, overseeing all three subspecies, and the Amur tiger SSP Coordinator.

What does an SSP Coordinator do?
An SSP coordinator is responsible for managing a population of an endangered species to ensure that it remains genetically healthy and stable as an insurance policy in case something happens to the wild population. This is accomplished with the help of a studbook keeper for each species or subspecies in the SSP who maintains information about each animal's family history, breeding history, age and location. The studbook keeper for the Amur, Sumatran, and Malayan tiger subspecies is Kathy Traylor-Holzer of the Conservation Breeding Specialist Group (located at the Minnesota Zoo). With the studbook information, an SSP coordinator can make recommendations with the help of other advisors about which animals should breed with which other animals. Often these recommendations require tigers to be moved to zoos in other parts of the country and sometimes other parts of the world.

Since its opening, the Minnesota Zoo has produced 37 tiger cubs. Through his work in captivity with the Tiger SSP and his fieldwork helping to save wild tigers in Sumatra and China, Dr. Tilson and the Minnesota Zoo are making a difference in the conservation of this highly endangered species.

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Report on Tiger SSP Status (2009)
Three of six Panthera tigris subspecies - Amur (P.t. altaica), Malayan (P.t. jacksoni), and Sumatran (P.t. sumatrae) - are currently managed by the AZA Tiger SSP. The Amur (Siberian) tiger population will be managed at the current level of 150 tigers, and each of the other two subspecies, Sumatran and Malayan, will be expanded up to a maximum of 150 tigers each. All subspecies will be managed to maximize the retention of gene diversity, but it is recognized that it may not be feasible to maintain 90% gene diversity over a 100-year program without substantial founder importation, particularly for the Sumatran and Malayan subspecies. For future years the Tiger SSP may need to consider the option of managing only two subspecies, one temperate (Amur) and one tropical (Sumatran or Malayan), depending on our ability to acquire additional founders.

There are currently 133 Amur tigers (54 males; 79 females) at 48 institutions in the AZA Tiger SSP. The target population size designated by the AZA Felid Taxon Advisory Group is 150. The current population has a relatively stable age distribution (although recruitment has been lower than expected over the past few years), with high survival and good reproductive success into the mid-teen years. Gene diversity increased from 1982 through 2001 due in part to periodic opportunistic importations from the European zoo tiger program (EEP) and Russia, and is now at 96.6% as compared to that of the wild tiger population. The long-term SSP goal is to retain at least 90% gene diversity for at least 100 years.

The Sumatran tiger SSP population consists of 73 individuals at 25 institutions.  The population is derived from 16 founders and retains 89.7% gene diversity. A breeding moratorium was under effect from 1994-1997 pending the results of DNA testing to verify subspecies purity, resulting in a gap in the population's age structure. Importations of captive Sumatran tigers from Indonesia are being pursued to promote the genetic basis of this population.

The Malayan tiger SSP population is now at 50 tigers, maintained in 21 institutions. This population is based upon 10 founders and currently retains 89.7% gene diversity. Discussions with the Malaysian Department of Wildlife and National Parks to export new founders from their zoos that are surplus to their management plan have been initiated but currently no decisions have been made.

Status of wild tiger populations
It has been estimated that as few as 3,500 tigers remain in the wild.  This represents a 33% decline in the last decade.  Maximum population size estimates for the different tiger subspecies are: Amur – 390, Bengal – 2300, Indochinese – 1230, Malayan – 500, and Sumatran – 230.  South China tigers are thought to be extinct in the wild and may only survive in Chinese zoos. Probable causes of decline include poaching for tiger parts and skins, as well as habitat destruction and fragmentation. 

References:
Dinerstein E, et al. 2007. The fate of wild tigers. Bioscience 57: 508-514.

Seidensticker J, Gratwicke B, & Shrestha M. In press. How many wild tigers are there? An estimate for 2008. In: Tilson R, Nyhus PJ, editors. Tigers of the World: The Science, Politics, and Conservation of Panthera tigris, 2nd Edition. Norwich (NY): Elsevier.

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