The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. In 1978, the elephant is listed as threatened under the United States’ Endangered Species Act. Nearly all male elephants and most females have tusks. As in Gorongosa, the numbers are highest among older females. Elephants use tusks as tools for foraging, digging, breaking branches, stripping bark, and moving things around. Fewer African elephant males are tuskless because successful competition for females is strongly dependent on tusks. The tusks of elephants are lateral incisors, located on either side of their two front teeth. Tuskless females tend to have _____ (tusked/tuskless) offspring. Use the theory of evolution to explain the observation that there are no tuskless males in the park. And among elephants ages five to 25, 13 percent of females are tuskless. The variation comes from random mutations and the recombination during sexual reproduction. Again, elephants with tusks were killed, and by the end of the war, half the females were tuskless. Selection for Tuskless Elephants | hhmi BioInteractive, How an Elephant Loses Its Tusks: A Lesson in (Un)Natural Selection | National Geographic, Going Tuskless | African Wildlife Federation, Natural & Cultural History | Addo Elephant National Park, Contributors: Dr. Joyce Poole and Petter Granli (ElephantVoices), Juli Hennings, Harry Lynch. Still, ivory trade continued across the world. Historically, 2–4 percent of unstressed African elephant females are tuskless; tusks are an inherited genetic trait. But the reason why males, so far at least, have not evolved to be tuskless is not clear. Females (cows) tend to live in family groups, which can consist of one female with her calves or several related females with offspring. Today, the Gorongosa population includes about 800 individual elephants in 24 families. EarthDate is a production of the Bureau of Economic Geology at the University of Texas at Austin. In South Africa’s Eastern Cape, northeast of the city of Port Elizabeth, the Addo Elephant National Park is home to a unique population of elephants with a sad past but an amazing conservation story. A ban on the international trade of ivory goes into effect in 1990, though the population of elephants is now fewer than a million. While almost all male African elephants have tusks, around 2 to 6 percent of females live life with none whatsoever. Most African elephants have tusks. The tusks of males weigh up to seven times those of similarly aged females. Tusklessness is being genetically favored — … Illegal hunting of elephants, or poaching, occurs at alarming levels. But with the hunting pressure off, experts think natural selection may again favor animals with tusks—and both groups may eventually become tusked again. In Asian elephants, females do not have tusks and males can be either tusked or tuskless (called “makhnas”). Fortunately, public opinion forced a change of heart and a preserve was established to protect the elephants. Use the theory of evolution to explain the observation that there are no tuskless males in the park. The tuskless matriarchs had tuskless offspring, and today nearly all female elephants in the park lack tusks. Furthermore, among elephants over 25 years old the population is very skewed toward females, due to the fact that male elephants have much larger tusks and are, therefore, preferentially killed by poachers. Of the surviving elephants that were adults during the war, most are female, and over half of these are tuskless, evidence of the preferential poaching of males and older tusked females. This limited the trade of some ivory. When compared to the elephant populations across Africa, the frequencyof tuskless elephants is only 6%. g. Tusklessness is an (inherited/acquired) trait. In the late 1800’s, farmers started settling in the area. In Gorongosa National Park, Mozambique, however, about 33% of young females are tuskless.What are tusks? Mr. (Our favorite tusks? 10. Currently, there are more than 600 elephants in the park, a real success story for conservation efforts. Of those 8 founding females, 4 (50%) were tuskless & 3 had at least one tusk, Whitehouse could find no details of the 8th. It was used to make combs, pool balls, knick-knacks, and even piano keys. So a population “ends up with a higher proportion of tuskless animals who then reproduce and tend to produce tuskless offspring,” she says. But a small percentage of elephants are born without these teeth and never develop tusks. An increase in females without tusks has also been seen in Zambia, Tanzania and Uganda in recent years. These are just elongated lateral incisors that grow outward once the elephant loses its baby teeth. Individuals in a population differ in some trait. The “unnatural selection” pressure of hunting and war creates circumstances in which tuskless elephants are more likely to survive, breed, and pass on the genes for missing lateral incisors in regions where intense hunting or poaching has occurred. Developing an Explanation for Tuskless Elephants INTRODUCTION Most African elephants have tusks, but typically about 6% of females in a population will never … By 1913, the African elephant population had dropped to an estimated 10 million. Elephants with more ivory were more valuable targets. Adopted a LibreTexts for your class? 10. Most obvious, though, is the high proportion of tuskless elephants. With the passing of time and generations, the proportion of tusked individuals in the population will probably increase, slowly reverting back toward baseline levels. Tusks continue to grow longer and thicker throughout their lives. Humans appear to have caused this shift in elephant evolution. Older female elephants — spared because they had no tusks — then passed the tuskless gene down to their daughters. Complete the following table. About 2 to 6% of the female elephants are typically tuskless. The Gorongosa elephants still exhibit dramatic behaviors that indicate they remember the horrors of the war—they have a heightened fear of people. ©Bureau of Economic Geology 2017. Selection for tuskless elephants By 1931, only 11 elephants remained in the region, and half of the 8 female survivors were tuskless. It's long been thought that tusks must confer an advantage in competitions between males for dominance and mating rights. Synopsis: Evolutionary change generally involves long time frames of Earth history. 1. Click here to let us know! What would probably happen to a male elephant that doesn’t have tusks? Tuskless females tend to have _____ (tusked/tuskless) offspring. What is unusual about the elephant populations found in Gorongosa now? Figure 1 shows the percent of tuskless female elephants expected in wild populations throughout the species' range, as well as the percent of tuskless females that survived the hunting between 1977 and 1992 (those over 25 years old) and the percent of female elephants born after 1992 without tusks in … What percentage of females are typically tuskless in an elephant population less affected by poaching? An increase in baby elephants born without tusks has conservationists asking if the trend is an evolutionary response to ivory poaching. Of the less than 200 survivors, over 50 percent of the females – 25 years or older – had no tusks. Take the case of the tuskless elephant. Hunters have historically targeted elephants with the largest tusks because of the value of their ivory; males and older females have always been at higher risk. Tuskless females tend to have _____ (tusked/tuskless) offspring. Some individuals with a trait are more likely to survive and reproduce than those without the trait. About 35 percent of females older than 25 are tuskless, she says. Have questions or comments? Tusklessness is an (inherited/acquired) trait. Nearly all male elephants and most females have tusks. In other words, the Addo elephants have been through a substantial population bottleneck. Smaller tusks are not the only genetic consequence faced by elephant populations in Africa (and Asia) due to heavy poaching. A report from Nautilus report suggests a growing number of female elephants are tuskless, with links to the ivory trade. By 1931, only eight females survived, and half were tuskless—perhaps because they made the least attractive trophies. No tuskless males have been found. Can a rhino kill an elephant? With the extra use, the master tusk develops a groove over time. Tusks are used as weapons against potential predators. What percentage of females are typically tuskless in an elephant population less affected by poaching? The heaviest tusk recorded weighed almost 265 lbs (120 kg)! Over several decades, researchers have documented an increase in the percentage of complete tuskless males and females in a number of elephant populations. [NARRATOR:] Surveys conducted by Poole and colleagues indicated that 33% of females 10 to 20 years old are tuskless. Selection depends on the environment. Early estimates of elephants on the continent of Africa suggest that there were as many as 26 million elephants living there in the 1500s. 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