Sustainable Use and "Surplus" Animals: Sabotaging Natural Selection

For many government officials and scientists responsible for the management of the planet’s wildlife species, “sustainable use” is synonymous with “perpetual exploitation.” It is a dogma that insists wildlife cannot be protected unless people can profit.

Sustainable use is broadly applied to wildlife management around the world. Deer and duck populations are commonly managed via models based upon a sustainable use concept. So too is muskrat trapping, seal hunting, trophy hunting, and many other means of large-scale wildlife killing. Sustainable use treats wildlife as if it were a crop to be raised—where the primary considerations are whether enough of the crop will grow back every year to meet demand, and whether there is money to be made in the harvest.

Two fundamental notions underlie the concept of sustainable use: that most wild animals tend to reproduce more offspring than are needed to replace the parent generation and that populations are more important than individuals. If such growth is not suppressed by natural or anthropogenic factors, there eventually are more animals than a habitat can comfortably support, resulting in impacts perceived to be adverse by many wildlife managers.

Sustainable use assumes that “surplus” animals can be killed without harming the population. The individual is inconsequential, regardless of that animal’s potentially valuable genetic profile, role in the herd or pack, or personality. Often, wildlife managers intentionally manage wildlife populations to maximize productivity—such as allowing the killing of a higher percentage of males (since a single male can breed with many females) or reducing predator populations so as to leave more prey species for human hunters.

Consider the Muskrat
The muskrat is an ideal species to illustrate the deficiencies with the twin concepts of surplus animals and sustainable use. Wildlife managers might look at 20 muskrats and think they could “harvest” half of them to keep the habitat “in balance.” They could even sell trapping permits to kill the muskrats. And the fur of the harvested muskrats could provide some modest income for trappers. This practice could continue in perpetuity (or, in their terminology, “sustainably”) by periodically culling the muskrat population in a particular area to 10 individuals, while generating agency revenue and a steady stream of income for the local community.

Of course, the number of muskrats killed annually in North America is well in excess of 10 animals. Indeed, in 2014 alone, over 820,000 muskrats were killed in 34 US states according to data compiled by the Association of Fish and Wildlife Agencies. At a single fur auction held in Ontario, Canada, in March 2017—a total of 361,084 skins of trapped animals were heaped onto the auction tables. Of these, 150,808 belonged to muskrats. Pitifully, the auction’s official record notes that the furs of those 150,808 muskrats went “mainly unsold” (raising the question as to what exactly was “sustained” by their deaths).

The suffering inherent to the exploitation of any wildlife species is important, and should not be ignored. Nearly all muskrats are caught in steel-jaw leghold traps or Conibear traps set near or in water, causing the animals to drown if they are not killed by the clamping force of the trap itself. But muskrats have evolved important adaptations to aquatic life and can hold their breath for several minutes, ensuring an extended period of pain and terror before death.

Beyond the vital questions concerning how much we are making animals suffer (and why), there is the question as to whether the very concepts of surplus population and sustainable use should be the basis for wildlife management.

Charles Darwin was aware that nature tends to be prolific, and produces more offspring of nearly every species than their habitats can possibly support. Understanding this phenomenon allowed him to develop his concept of “natural selection” which, in turn, became a core element of his theory of evolution.

Darwin observed that with such abundance, competition naturally arose among conspecifics (animals of the same species) for limited amounts of food, shelter, and other resources. In this competition, the fitter individuals survived and passed their genes to future generations, and the less fit did not.

But what confers fitness to any particular animal? Today, we understand this to be the sum of advantageous morphological and behavioral characteristics that are genetically determined and ultimately lead to production of surviving offspring. These characteristics are the result of evolution.

Some 5 million years ago, during the Lower Pliocene, the ancestor of today’s muskrat was quite a different animal. But gradually, there were advantageous genetic mutations that benefitted certain individuals. For example, one mutation provided for thicker enamel in the animal’s teeth, and that mutation helped the proto-muskrat chew on tough cattails. This improved the animal’s fitness, and the gene for thicker enamel was passed to following generations. Another gene governed an increase in adult body weight. Five million years ago, the muskrat’s ancestor weighed less than four ounces, but today’s adult muskrat generally weighs between two and four pounds. Heavier muskrats with more enamel on their teeth were more successful, survived longer, and reproduced more than their lighter kin with thinner enamel.

Other advantageous genetic mutations also occurred. For example, the ability to hold their breath for a quarter-hour, the development of partially webbed hind feet, the development of relatively short, thick fur (which can trap air and contribute to buoyancy) are just some of the beneficial genetic changes found in today’s muskrats.

All living organisms impact the habitats in which they live. In wildlife management, impacts attributed to “overabundant” wildlife are often perceived as adverse when, in fact, they may be consistent with natural ecosystem processes and there may be positive effects that outweigh the adverse. Life itself is a dynamic process, and everything alive—whether a microscopic amoeba or the assemblage of species within an Amazonian ecosystem—is in constant change. There is no stasis in life. Absolute equilibrium does not exist in living things.

Muskrats are largely vegetarian, dining on (among other things) cattails, sedges, rushes, water lilies, and pond weeds. This dietary preference contributes to the ecological dynamics of the ecosystems where they live. For example, targeted grazing of cattails, including invasive cattail species, helps to maintain open areas in marshes. These open areas, in turn, are very important for the survival of many aquatic birds. An abundance of muskrats is also beneficial for foxes, hawks, wolves, owls, and many other carnivores who prey on them. These dynamics work best when all parts of an ecosystem that co-evolved together are present.

Unnatural Selection
Notably, however, human-created, or “anthropogenic” devices, such as leghold or Conibear traps, are not substitutes for natural predators who have co-evolved with muskrats. This predator-prey relationship has been influenced by natural selection, while trapping of muskrats results in a type of “unnatural selection” that poses enormous problems, especially in the context of sustainable use.

With few exceptions, allegiance to sustainable use contributes to unnatural selection by permitting the use of anthropogenic management tools like traps, firearms, and snares that are not in the target animal’s evolutionary history. Such tools diminish the efficacy of the target animal’s natural defenses—including acute sense perception, speed, or even the ability to hold one’s breath. Animals' natural defenses may even hinder their survival when confronted with the human tools of exploitation. For example, other influences being equal, the animal with the most acute olfactory senses will detect bait in a trap first, likely being caught as a consequence. In such a case, the acute olfactory senses that evolved over time contributed to the animal’s death. When such human interference is excessive, natural fitness-enhancing processes are compromised, to the detriment of the species.

Sustainable use management of wildlife often harms the very animals that natural selection would otherwise protect. Among elephants, for example, herds normally are matriarchies, usually led by the oldest, most experienced female. Because ivory grows throughout the life of the elephant, the matriarch usually has the largest tusks. If elephant hunting is permitted, a hunter generally prefers to kill the largest elephant and, in so doing, destroys the herd’s experienced leadership. Studies on the impact of hunting on elephant herds have documented that killing the matriarch almost inevitably leads to serious demographic stress that threatens the herd’s viability and adversely impacts the surviving herd members. Close family bonds and social structures encompassing generations are suddenly ripped apart.

It isn’t just elephants. Trophy hunters commonly target the most robust animal of any species—the lion with the most impressive mane, the stag with the largest antlers, the buffalo with the most massive horns. Indeed, hunting organizations keep detailed records of who killed the largest, longest, broadest, and heaviest victims of sustainable use. Usually, these are animals with inherited traits that would have favored a longer life, allowing these traits to be passed on to future generations. Hunters are not known to seek out the weak, the crippled, or the sickly—the individual natural predators usually target.

The persistent removal of the most robust animals from any population, coupled with artificial suppression of those populations to support maximum sustainable use, ultimately has consequences to the fitness of survivors, their herds, populations, and entire species. But as evolution is a long-term process, it is very difficult to anticipate significant effects, and it takes many, many generations for related morphological changes to be documented. Similar to concerns over global warming, the indicators of unnatural selection can appear almost trivial, but the long-term ramifications can be catastrophic.

Depending upon its intensity, the application of sustainable use in wildlife management diminishes, and even eliminates, competition among conspecifics. If there are fewer animals of a particular species in a given habitat, there is hardly any competition among them. The elimination of this competition removes the principal mechanism for identifying and testing the value of any genetic mutation. Consequently, when it comes to wildlife, abundance is not prodigal or extravagant, it is a necessity: an indispensable ingredient for the process of evolution itself.

Invariably, sustainable use involves someone planning to obtain a benefit or make a profit from the misfortune of animals. This profit incentive is dressed up as legitimate conservation. It is not. At a fundamental level, sustainable use diminishes the direct, indirect, and cumulative benefits that wildlife provide to people and nature.

For some species, like bobcat, python, and many others listed on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), trade is ostensibly permitted only if it is “non-detrimental” to the species in the wild. In other words, such trade must be “sustainable.” Nevertheless, with approximately 70,000 bobcat pelts, 500,000 python skins, and 7.7 million pounds of reptile skins overall (much of it from Appendix II-listed reptile species) traded annually, it is very difficult to imagine that such pervasive unnatural selection against the wild populations of so many animals could lack evolutionary implications.

We humans have assumed the stewardship of nature. With this stewardship comes an implicit responsibility to avoid doing harm. Anthropogenic impacts fall not only on individual animals, but also on the overall integrity of ecosystems, and on nature itself.