Some bighorn sheep males no longer grow large horns — possibly as a result of human hunters’ natural selection. ©Henry H. Holdsworth
Despite antipoaching patrols, increased arrests, relocation, and unmanned security drones, it seems we’re losing the battle against wildlife poachers. Already in the first six months of 2013, for example, in South Africa alone, 428 rhinos have died at the hands of poachers. Rhino horns are in demand because the desire for traditional “medicines” in Asia is growing. Products that contain rhino horn are touted as successful cancer treatments, and rhino horn is being marketed even in hospitals to the families of critically ill patients
Other species, too, are suffering from specific human activities. A study published in the peer-reviewed journal PLoS One in March revealed that 62 percent of African forest elephants vanished between 2002 and 2011. The population is now less than 10 percent of its potential size. They are being poached out of existence for their ivory. The Wildlife Conservation Society estimates that some twenty-five thousand African elephants are killed every year — this despite a ban on ivory poaching that was instituted in Africa in 1989.
Our efforts to counteract the devastating harm we’re causing to other species’ are failing. It looks like we humans needs some help. And now, we just may be getting it from an unexpected source: evolution.
Eventually, all elephants may be born without tusks. ©Dave Luck
Luckily, we aren’t the only forces now trying to hold back the tide of poachers. The natural process of evolution is stepping in. According to an astounding research study recently published in the African Journal of Ecology,elephants all over the world have begun selecting against having tusks. For example, the frequency of female elephants without tusks has increased from 10.5 percent to 38.2 percent in South Luangwa National Park, Zambia. The tuskless trait appears to run in families and may have been a result of tuskless females being spared by poachers — tuskless mothers survive in greater numbers and hence have more tuskless daughters.
In Asia, there’s a similar trend. It used to be that only 2 to 5 percent of Asian male elephants were born without tusks. But by 2005, it was estimated that the tuskless population had risen to between 5 and 10 percent.
It’s clear that around the world, tusklessness is getting passed on. However, elephants use their tusks as weapons to battle during mating season and as tools to dig for water and roots. Nevertheless, it seems nature is recognizing that poachers are a greater threat to an elephant’s existence than its diminished ability to forage or to mate.
Nature fighting back
A similar phenomenon is being seen with bighorn sheep. Trophy hunters aim for the animals that have the most impressive headgear. In recent years, however, according to a 1995 study published in Conservation Biology, males in some populations of bighorn sheep are no longer growing large horns. This may be a result of human hunters’ unnatural selection. But having no horns for sparring could cause problems, since males butt heads for dominance and to gain access to females. Apparently, trophy hunters are seen by nature as the bigger peril.
Rhino horns are prized in Asia for their purported “medicinal properties,” yet they contain nothing more than the same keratin found in fingernails. ©Toby Sinclair
Evolution due to the influence of human hunting is also being seen in the fish world. Big cod are becoming more rare. Unlike most animal predators that go after the small and the sick, human fishermen try to catch the largest fish, those that are usually in their reproductive prime. This results in selective pressures that have driven cod and some other fish species to reach sexual maturity earlier and at smaller sizes.
And although we currently aren’t intentionally trying to overharvest cliff swallows, they, too, have been changing due to our actions. U.S. Department of Agriculture scientists estimate that 80 million birds die in collisions with motor vehicles in the United States every year. The swallows are now evolving to dodge vehicles.
Research results published in the publication Current Biology indicate that over the last thirty years, fewer cliff swallows have been killed along roads in southwestern Nebraska. At the same time, the birds’ wing lengths have been decreasing, allowing them to be more nimble and better able to dodge cars. The study’s authors suggest that automobiles may be killing higher numbers of long-winged birds, leaving more of the agile, nubbier-winged swallows to pass on their genes, circumventing the damage we do to this species with our cars.
Source: Written By Candice Gaukel Andrews.