Why do female African elephants no longer grow tusks?
In everyone’s impression, evolution is a very long process, especially for some key traits for organisms, but with the continuous increase of human hunting and poaching of wild animals, this situation may have changed. Evolution, under the effect of artificial selection, started to run wild.
A 15-year civil war ravaged Mozambique from 1977 to 1992. In order to obtain war funds, rampant poaching has caused a sharp decline in the number of elephants in Gorongosa National Park, and more than 90% of African elephants have lost their tusks. Object-wise, ivory = life.
After the war, although poaching has disappeared in Gorongosa National Park, what people don’t know is that the war has left indelible marks on these African elephants.
According to a recent study published in Science, the number of tuskless female elephants in Gorongosa National Park nearly tripled after the civil war in Mozambique: Before the civil war, about 18.5% of female elephants were born without tusks; in 2000 , accompanied by a sharp decline in the number of African elephants in Gorongosa, this proportion increased to 50.9% among war survivors.
This is not difficult for everyone to understand. After all, poachers will only hunt African elephants with tusks, and those female elephants without tusks will naturally be spared. The proportion of tuskless female elephants will naturally increase. come higher.
In fact, the impact of poaching on African elephants is not so simple. Of the 91 female elephants born after the civil war, the proportion of tuskless rose to 33 per cent, the study showed.
What does this mean?
Next, let us use a set of data to see how poaching has affected the evolution of African elephants. According to statistics, in the absence of human interference, only 2% to 4% of female African elephants are born without tusks. This tuskless feature has allowed these female elephants to survive the hands of poachers, so much so that in poached Gorongosa National Park in Mozambique and Ruaha National Park in Tanzania, newborn female elephants (under 25 years old) The proportion of no ivory has increased to varying degrees.
In addition to the two aforementioned national parks, the impact is even more severe in South Africa. In the early 2000s, 98 percent of the 174 female elephants in Addo National Park were reported to have no tusks. Apparently, rampant poaching appears to be doing more than removing tusk-bearing individuals from the herd—the tendency for new females in elephant herds to no longer have tusks seems to correlate with the selection brought about by poaching. related.
In fact, poaching also has a considerable impact on male African elephants, which is reflected in the reduction in the size of the tusks of African elephants due to poaching. According to a study published in 2015, in some areas where poaching is rampant, such as southern Kenya, the tusks of male elephants born after 1995 were 21 percent shorter than those of males born in the 1960s, and the figure was 27 percent shorter for females .
There is no doubt that this study of African elephants will help us understand how human selection of wild animals changes the evolutionary process of nature. At the same time, this sounded the alarm for us—human activities are an important evolutionary force on the earth.
For humans, we have glimpsed the mystery of the evolution process from this phenomenon, but for African elephants, the cost of tuskless evolution needs to be borne by the entire African elephant population, its living community, and even the entire ecosystem.
A chain reaction of not growing ivory
As a key species in the community, changes in the living habits of elephants have a huge impact on the ecology of the entire community.
Ivory, essentially overgrown teeth, serves a variety of purposes for elephants: digging for groundwater or vital minerals, stripping tree bark for fibrous food, and helping males compete for females.
Not only that, but in the past, ivory has helped elephants knock down trees, which is also important for other animals that depend on them (some lizards prefer to make their homes in trees that elephants have eaten or knocked over).
Today, elephants have lost their tusks, and their lives have naturally changed.
After the researchers analyzed the DNA in elephant feces, they found that elephants with tusks and elephants without tusks would eat different plants. This change may cause a series of chain reactions-in order to obtain enough food, elephants may have It will change their habitat and migration routes, which will affect the health of surrounding ecosystems.
For African elephants, a gene affects whether there are tusks or no tusks, and whether there are tusks or no tusks affects the survival of individuals under poaching, and the survival of tuskless individuals affects the health of the ecosystem.