Species translocation

Species translocation is an effective management strategy and important topic in conservation biology. Translocation is the movement of a species, by people, from one area to another. This management tool decreases the risk of extinction by increasing the range of a species, augmenting the numbers in a critical population, or establishing new populations thus reducing the risk of extinction. [Rout, T. M., C. E. Hauser and H. P. Possingham. Optimal translocation strategies for threatened species. http://www.mssanz.org.au/modsim05/papers/rout.pdf. 2007. Accessed on 11 May 2007. ] This improves the level of biodiversity in the ecosystem.

Three types of translocations

The first of three types of translocation is introduction. Introduction is the deliberate or accidental translocation of a species into the wild in areas where it does not occur naturally. Introduction of non-native species occurs for a variety of reasons. Examples are economic gain (Sitka Spruce), improvement of hunting and fishing (fallow deer), ornamentation of roads (rhododendron) or maintenance (sweet chestnut). In the past, translocation introductions of non-native species to ecosystems far outweighed the benefits of them. [Holdgate, M. (1999) Lancaster: British Association of Nature Conservationists/National Trust Conference - Nature in Transition.] For example, eucalyptus trees were introduced in California during the Gold Rush as a fast growing timber source. By the early 1900s, however, this did not happen because of early harvesting and the splitting and twisting of cut wood. Now the introduction of non-native eucalyptus, particularly in the Oakland Hills is causing competition among native plants and encroaching on habitat for natural wildlife.

The second of the three types of translocation is re-introduction. Re-introduction is the deliberate or accidental translocation of a species into the wild in areas where it was indigenous at some point, but no longer at the present. Re-introduction is used as a wildlife management tool for the restoration of an original habitat when it has become altered or species have become extinct due to over-collecting, over-harvesting, human persecution, or habitat deterioration.

Lastly, the third type of translocation is re-stocking. Re-stocking is the translocation of an organism into the wild into an area where it is already present. Re-stocking is considered as a conservation strategy where populations have dropped below critical levels and species recovery is questionable due to slow reproductive rates or inbreeding. The World Conservation Union recommends that re-stocking only occur when the causes of population decline have been removed, the area has the capacity to sustain the desired population, and individuals are of the same race as the population into which they are released but not from genetically impoverished or cloned stock.

Trends of translocations

Between 1973 and 1989 an estimated 515 translocations occurred per year in the United States, Canada, New Zealand and Australia. [Griffith, B., J.M. Scott, J.W. Carpenter, and C. Reed. 1989. Translocation as a species conservation tool: status and strategy. Science 245:477-480.] The majority were conducted in the United States. Birds were the most frequently translocated, followed by threatened and endangered species, then non-game species. [Griffith, B., J.M. Scott, J.W. Carpenter, and C. Reed. 1993. Animal translocations and potential disease transmission. Journal of Zoo and Wildlife Medicine 24:231-236.] Of the 261 translocations in the United States reported wild species were most frequently translocated, and the greatest number occurred in the Southeast.

Programs in action today: Western Shield

Western Shield, of Australia, is a nature conservation program which plays an important role in protecting Australia’s native animal population. More importantly, Western Shield also has programs specializing in translocation of endangered and threatened animals. Founded in 1996, it's the most successful wildlife conservation program in Australia and in 2006, it still remains among the largest in the world. The program has already had significant success: three native mammals in Australia – the woylie, quenda and tammar wallaby – have been removed from the threatened species list, many populations of native animals have recovered or been re-established in their former ranges, and the restoration of ecological processes has begun. From 1996 to 2000, Western Shield has taken part of 60 translocations, mostly introductions, comprised of 17 species all over the country on private and interstate lands. [McNamara, Keiran. 2004. Western Shield. Conservation Science W. Australia. 5(2): 1]

Reasons for failures

Often, when conducting translocation programs, differences in specific habitat types between the source and release sites are not evaluated as long as the release site contains suitable habitat for the species. Translocations could be especially damaging to endangered species citing the failed attempt of "Bufo hemiophys baxteri" in Wyoming and "B. boreas" in the Southern Rocky Mountains. [Muths, E., T. L. Johnson, and P. S. Corn. 2001. Experimental repatriation of boreal toad (Bufo boreas) eggs, metamorphs, and adults in Rocky Mountain National Park. Southwestern Naturalist 46: 106–113.] For species that have declined over large areas and long periods of time translocations are of little use. Maintaining a large and widely dispersed population of amphibians and other species is the most important aspect of maintaining regional diversity and translocation should only be attempted when a suitable unoccupied habitat exists. [Trenham, Peter C. and David M. Marsh. 2002. Amphibian Translocation Programs: Reply to Seigel and Dodd. Conservation Biology. 16(2): 555-556.]

Notes

External links

* [http://www.iucn.org/ World Conservation Union]
* [http://www.naturebase.net/projects/west_shield.html Western Shield]

Further reading

* Griffith, Brad, Michael Scott, James Carpenter, Christine Reed. “Translocation as a species conservation tool: status and strategy.” 1989. "Science". 245 (4917): 477-480.