How an Elephant Loses Its Tusks: A Lesson in (Un)Natural Selection

SCIENCE

Tuskless elephants may be a response to the selective pressure of poaching. (Nautilus)

Learn more about the natural and unnatural history of the African elephant with our video study guide.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

Discussion Ideas

  • Most African elephants have tusks. In Gorongosa National Park, Mozambique, however, about 33% of young females are tuskless. What are tusks?

 

  • Do tusks serve a purpose, or are they a genetic oddity?
    • Elephants use their tusks all the time. “Prying bark from trees; digging for water, roots, or minerals; [or] fighting other bull elephants—tusks perform a variety of functions.”
    • Although life without tusks can be difficult—especially for males—it is possible. Between 2% and 6% of female elephants are tuskless. (The number is much lower for males.)

 

 

  • How might a tuskless elephant be better-adapted to its environment?
    • Tuskless elephants are less likely to be poached. So, they are more likely to breed and pass on the trait for tusklessness.

 

  • Are tuskless elephants a result of poaching?
    • No, not directly. Tuskless elephants are largely a result of having tuskless mothers.

 

  • Why do you think more female than male elephants are tuskless?
    • Tusks are a more valuable trait in males. “Because males require tusks for fighting, tusklessness has been selected against in males and very few males are tuskless. For African elephants, tuskless males have a much harder time breeding and do not pass on their genes as often as tusked males.”

 

  • How has poaching impacted the breeding population of “tuskers” in Gorongosa National Park?
    • Elephants are more likely to have smaller tusks than elephants in less-trafficked areas. “Assuming that poachers select according to tusk size, they will tend to kill older males with very large tusks, [removing] breeding-aged males who also happen to have very big tusks. Those males then no longer pass on their genes for large tusks … [Then, when the surviving] young males grow older, they are killed for their tusks before they reach breeding age. In this manner, heavy poaching will select out genes for large tusks.”
    • Elephants are more likely to be tuskless. “Whereas baseline tusklessness in a population might be 4%, over time as more and more tusked elephants are killed, the percentage may increase to 60% in the older animals. When this group breeds with tuskless females, 50% of whose daughters are tuskless, you begin to see the gene for tusklessness spreading in the population.”

 

 

  • Poaching may be influencing the physical characteristics (tusklessness) of Gorongosa’s elephants. Is poaching also impacting behavioral characteristics? Consult our video study guide for some help.
    • Yes. The video documents disturbing changes in elephant behavior, including dramatic displays of fear and increased agitation, stress, and aggression in the presence of humans. The altered behavior can disrupt elephants’ complex social structure, reduce their success in breeding, and increase their antagonism toward humans.

 

This South African elephant is naturally tuskless. And angry—look at those flared ears. Photograph by Chris Eason, courtesy Wikimedia. CC-BY-2.0

This South African elephant is naturally tuskless. And angry—look at those flared ears.
Photograph by Chris Eason, courtesy Wikimedia. CC-BY-2.0

TEACHERS TOOLKIT

Nautilus: How an Elephant Loses Its Tusks

African Wildlife Foundation: Going Tuskless

Nat Geo: A Natural History of the African Elephant video study guide

Nat Geo: Altered Elephant Behavior video study guide

One response to “How an Elephant Loses Its Tusks: A Lesson in (Un)Natural Selection

  1. What’s to be done? Just stop poaching? Are zoos an answer? I am not a teacher or student by the way.

    Like

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