Report – ZL3205 – Exploitation of Wildlife

ZL3205, 2000-08-23

Commercial Exploitation of Wildlife Populations


Not everyone cares about the fate of the environment or wild animals. Some people would not worry if the world’s wild animals disappeared overnight, because they are city people. Although people have always made use of wild animals, the scale of use is far greater than in primitive ages (Bolton, 1997).

Everything has been visited… everything exploited. Now pleasant estates obliterate the famous wilderness area of the past. Ploughed fields have suppressed the forests; domesticated animals have dispersed wildlife. Beaches are ploughed, mountains smoothed and swamps cleaned… We weigh heavily upon the world; its resources hardly suffice to support us. As our needs grow larger, so do our protests that already nature does not sustain us.

This could be stated by any modern conservationist or environmentalist, but it was written by a Tertulian in 200AD. Even then, there were conservation and environmental problems of similar kind facing modern technological society (Webb, 1997).

The commercial exploitation of wildlife resources in a sustainable way has become a catch-phrase within wildlife conservation and has gained increased acceptance from the World Conservation Union (IUCN) (Campell, 1998).

When discussing sustainability in this paper, it refers to biological sustainability not socio-economic sustainability of the harvests.

Some widespread and common types of kangaroos are harvested commercially for their meat and skin. It is argued that this is a ecological way of dealing with the serious problem that large numbers of kangaroos can cause farmers. This way we can use the natural resource the best way (Aplin, 1999).

This paper will discuss the potential of commercial exploitation of wildlife to support conservation goals.

Can commercial exploitation be applied to any animal?

Exploitation through harvest.

One could harvest any animal exceeding their carrying capacity K which is the maximum population the environment can sustain of a particular organism, if a harvest is applied above K the population will decrease and could in extreme cases drive the population to extinction (Bolton, 1997). Such species populations can only sustain harvest of relatively small numbers of individuals. These characteristics are not likely to provide an economically sustainable yield. Also determining maximum sustainable yield for such populations may be difficult with the likelihood that over-harvesting can lead to population crash and greater risk of extinction, due to the long time before sufficient number of individuals reach reproduction maturity.

Exploitation through culling.

Some species of kangaroo are so abundant in some areas that they cause major damage to farming and grazing properties. In large numbers, the kangaroos can ruin crops and damage fences. They also feed on the same food plants as livestock and compete for water. Farmers can lose income as a result, which affects the whole rural community. Commercial harvesting decrease the risk at no cost to the farmer, in some places the farmers can even make a profit (Anon., 1996).

In the mid 1990’s there were changes in the way that kangaroos were viewed by the rural community. Rather than a possible rural problem, kangaroos were being seen as a valuable natural resource for their meat and skins. Harvesting kangaroos can change a commercial problem into an economic gain for the farmer. However, it is essential that the kangaroos be carefully managed. There are 48 species of kangaroos in Australia, only 5 are commercially harvested. The population of these fluctuates between 15 to 35 million animals depending on seasonal conditions (Anon., 1996).

Exploitation through farming.

Biologists and some conservationists have seen farming of wildlife as a practical way of saving them from extinction. This has been suggested for turtles, giant clams and crocodiles.

If farming a particular species can be made profitable it will undoubtedly have a great incentive for conservation of this particular species. However, the farming does not mean that biodiversity is saved or maintained (Tisdell, 1995).

Exploitation through tourism.

The South African national parks and protected areas are largely self sufficient due to culling of some of the larger animal species (mainly elephant and Cape buffalo). The culling is considered necessary due to the animals’ seasonal movements which may extend beyond the park boundaries and also the numbers tend to increase beyond the carrying capacity of the park unless they are culled (Tisdell, 1995). Many feel that commercial use like trophy hunting, i.e. killing animals for recreational purposes, is unethical. Critics argue that the recreational killing of wild animals is immoral and that this practice would result in even more animal species to become extinct (Baker, 1997). This practice of recreational hunting of overpopulated herds can be imperative to save biodiversity and trophy hunting in CAMPFIRE districts in Zimbabwe alone in 1995 generated US$13million. Trophy hunters, also serve as a deterrent to poachers so it is much easier for managers to keep track of the animal stock in the parks due to hunting. That kind of money is not only an incentive to make the hunting sustainable, but there is a range of other aspects like water surplus and other social benefits for the local communities (Baker, 1997).

Unsustainable Harvest.

Giant clams lives in the shallow water habitats of coral reefs. Due to this shallow distribution, they are easy to locate and collect. They have been a traditional source of food within the geographical range they live in. It appears that even in pre-historic times giant clams species were driven close to extinction in areas where large populations of humans could be found, such as southern Japan (Bolton, 1997).

However, the trade of giant clam meat in traditional societies like Fiji is a new industry and this over-exploitation of giant clams is widespread. For example Fiji Fisheries’ statistics show that they exported totally 277.5 tons between 1978 to 1988. It is estimated that Taiwan imported between 100 to 400 tons per annum, 100 tons correspond to 300.000 to 450.000 giant clams. It has been shown that harvest wild populations of giant clam is not sustainable as it has been done previously, however, maricultures (agriculture in the open ocean) at for example Orpheus Island, Great Barrier Reef, has shown that it can potentially serve as a conservation of wild stocks of giant clams and serve as restoring depleted wild stocks for sustainable use (Bolton, 1997).

Would Sustainable Harvest Work?

“many more individuals of each species are born than can possibly survive…” Darwin (1859)

Conventionally the precautionary principle indicates that one must be extremely careful when taking a certain action if there is the slightest possibility of major and/or an irreversibly bad outcomes, even if there is no scientific evidence that those outcomes will follow (Deville et al., 1997; Aplin G. 1999). However, Webb (1997) stated that if one had to wait until it can be ‘proved’ something is sustainable, it meant that nothing could proceed. There can only be a probability of sustaining anything based on current knowledge. This is accepted in most aspects of our lives but when it comes to wildlife, people are starting to experience problems.

Darwin’s ideas on the principle of natural selection were based on an annual surplus in the seasonal dynamics of a population. This same conjecture also forms the foundations for sustainable harvests of natural populations i.e. it is only the “doomed surplus” of animals produced that will never survive the seasonal bottleneck (Boyce et. al. 1999).

Sustainable harvests are justified by this doomed surplus can be removed for human harvest (or recreational hunting) without negatively affecting the population size (Boyce et. al. 1999).

This have two immediate effects; compensation due to density dependence e.g. a response to the reduction due to harvest and/or predation is a decrease in natural mortality within the population and an increased availability of food for survivors that can cause an increase in reproductive output, i.e. compensatory natality (Boyce et. al. 1999).

Can commercial exploitation of endangered species support conservation goals?

In Ostional, Cost Rica, the olive ridley marine turtle (Lepidochelys olivacea), comes up to the beach and nests more or less monthly, with more nesting during the wet-season and less during the dry-season. Estimates range from 20.000 – 60.000 eggs in the dry-season to 90.000 – 180.000 eggs in the wet season (Campbell, 1998). Thousands of turtle nesters subsequently emerge on the same strip of beach saturating it with nests during the nesting cycles lasting 3-10 days each month. Also, late nesters dig up and destroy previously laid eggs, both from earlier the same month and previous months nests, due to the 45 days it takes for turtle eggs to hatch (Campbell, 1998).

As part of the established project, members of the “Integrated Development Association of Ostional” help the newly hatched turtles by cleaning up the garbage from the beach once a month to reduce the chance that the hatchlings will crawl into empty container or be hindered by other obstacles on their way to the sea, and to reduce plastic ingestion by adult nesting turtles. Members from the Association also ‘escort’ the hatchlings to the surf to reduce the chance of predation (Campbell, 1998).

Once there are signs of emergence from the hatchlings the ‘escorts’ dig up the nests and carry the hatchlings to the water to speed up the process. The question is whether this is a moral or the right thing to do, even if the turtles are long lived and it takes a long time for them to become fertile. Local biologist have even tried to stop this activity but without success. However, very few hatchlings that emerge in daylight would survive if left alone, due to the abundance of predators like ghost crabs and vultures. Thus, according to Campbell (1998) this activity do little harm.


Commercial exploitation of wildlife can be favorable to the survival of the species but not universally so. Economic use of wildlife favors species with high economic value i.e. large animals with high reproductive output and short life spans. The ethical responsibility of humankind is to conserve ecosystems as a whole (Grigg, et. al., 1995).

However, sustainable harvest do not necessarily have anything to do with species conservation (Struhsaker, 1998). What was considered a sustainable harvest 5-10 years ago will be inadequate for present and future market demands. In response to rising economic, social and political pressures, sustainability is redefined and harvest levels are raised accordingly (Struhsaker, 1998). Struhsaker (1998) argues that the trend and the risk unless dealt with, in a more holistic and objective and less anthropocentric view, of present levels of sustainable harvest will continue to drive species and ecosystems to extinction.

To be able to use wildlife commercially as a mean to support conservation goals, the particular population has to be considered on a case to case basis. Mainly because of the differences in the biology of the animals e.g. sea turtles’ life history and other long lived, slow maturing organisms can make them especially vulnerable to overexploitation (Heppel & Crowder, 1996). While an estimated 50% egg and hatchling harvest levels on American alligators was shown to be sustainable for a 11year study period (Rice et al., 1999).


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Anon. (1996) Environment Australia URL:

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Bolton M. (1997) Conservation and the Use of Wildlife Resources University Press, Cambridge.

Boyce M.S., Sinclair A.R.E. and White G.C. (1999) Seasonal Compensation of Predation and Harvesting OIKOS 87, 419-426.

Campell, L.M. (1998) Use them or lose them? Conservation and consumptive use of marine turtle eggs at Ostional, Costa Rica Environmental Conservation 25 4:305-319.

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Heppell, S.S. and Crowder, L.B. (1996) Analysis of a Fisheries Model for Harvest of Hawksbill Sea Turtles (Eretmochelys imbricata) Conservation Biology 10 3:874-880.

Rice, K.G., Percival, H.F., Woodward, A.R. and Jennings, M.L. (1999) Effects of egg and hatchling harvest on American Alligator in Florida. Journal of Wildlife Management 63 4:1193-1200.

Struhsaker, T.T. (1998) A Biologist’s Perspective on the Role of Sustainable Harvest in Conservation. Conservation Biology 12 4 930-932.

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Wilman E.A. (1994) Pests: Sustainable Harvest versus Eradication Journal of Environmental Management 46, 139-147.

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