© Billy Dodson
Large animals like elephants, lions, sharks and whales, are at a higher risk for extinction, in part due to hunting and poaching fueled by demand for luxury items, according to researchers from Colby College and Simon Fraser University. Their study on the topic was published today in the journal Current Biology.
The researchers studied a group of more than 100 marine and land animals that are targeted for international luxury markets. They first estimated the value of each animal, and then looked at the relationship between the animals’ value and body size, and tried to quantify the impact of poaching fines and how large a territory animals occupied.
The researchers found that risk of extinction increased in proportion to the animals’ size with larger animals being at greater risk than smaller ones, but only to a certain point. Once the value of an animal exceeded a certain threshold — $12,557 per kilogram, or $5,707 per pound — the animal’s size was no longer the major risk factor, its high value was.
In addition, the researchers found that current poaching fines are doing little to reduce the risk of hunting animals to extinction and would need to be increased 10 to 100 times current levels to have an impact.
“The extreme values of these species mean that without significant conservation intervention, they will be hunted to extinction,” Loren McClenachan, lead author of the study and an assistant professor of environmental studies at Colby College, said in a statement.
Biologists have long understood that larger animals tend to be at a greater extinction risk than smaller. Larger animals typically reproduce less frequently and have fewer offspring than smaller ones and as such, their populations grow more slowly. Thus, large animals’ extinction risk is intensified due to naturally being more sensitive to biological and environmental changes.
Last year, researchers reported that climate change poses a greater threat to large herbivores than smaller ones. Other researchers have found that since 1900, 477 vertebrate species have gone extinct. While some of those species may have died off because of natural causes, the study concluded that humans greatly accelerated the rate of extinction. Without human intervention, it would have taken between 800 and 10,000 years to lose that many species.
Conservation groups have found that elephant poaching has increased due to the increasing price of ivory, which hit $2,100 per kilogram in 2014, up from $750 per kilogram in 2010. As a result, about 33,000 elephants were killed every year between 2010 and 2012, according to Save the Elephants.
Today’s new study adds to these previous findings by quantifying the risk in terms of price per pound for 100 different animals. It also identifies a threshold beyond which economic factors that drive people to poach and hunt play a larger role than biological factors.
The authors also identified some key differences between marine and land animals, and suggest that conservation efforts take into account such differences. For instance, they dispute the common wisdom that marine animals’ larger range, compared to land animals, helps protect them from extinction.
Land animals with large ranges have a greater likelihood of protection in some countries, the authors found, but “this protection is almost non-existent in the oceans due to widespread deliberate, illegal, and indirect killing, such as bycatch, which affects species irrespective of trade protections that may be in place,” they wrote in the study.
Marine animals also exhibit specific behavior that puts them at an increased risk for being hunted. For instance, even when marine animals have large geographical ranges, they tend to show specific behavioral patterns — such as congregating in the same location to spawn.
The researchers said that the next step will be to design better conservation strategies. An international agreement, the Convention on International Trade in Endangered Species, is helping in some cases to stem poaching, they said, but much more work will need to be done.