Most African elephants have tusks, but some—about 2 to 6% of females and even fewer males—never grow them. Elephant tusks are important for obtaining food and water, and essential to male elephants for competing for mates, so there is strong natural selection for having tusks. But the proportion of tuskless elephants has increased in some populations. In this video Dr. Joyce Poole explains a possible reason. Elephants with large tusks are targeted by poachers, who sell the tusks on the ivory market. Poaching is selecting for tuskless elephants who are more likely to survive, mate, and pass on their genes . In Gorongosa National Park, Poole found that among the older female elephants, who survived a period of heavy poaching in the park, over 50% are tuskless. Among the younger females, who were born after this period of heavy poaching, 33% are tuskless.
The video could be used when studying microevolution and natural selection. It provides students with the opportunity to learn about
adaptations, or traits that increases an organism’s chance of surviving and reproducing in a particular environment;
how the frequency of certain traits in a population can change depending on the selective pressure; and
an observable example of natural selection driven by human activity.
The video provides an opportunity for graph interpretation at 4:56 minutes. Students could use the information in the video to practice writing a scientific explanation for the high frequency of tusklessness in elephant populations, such as those found in Gorongosa National Park.