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Tusk, Tusk...

July 10, 2013

Walrus, Odobenus rosmarus. One memorable song from the late 1970s was Fleetwood Mac's Tusk. This song was part of a double-album of the same name, which was priced at about $16.00. In today's money, that would be $50.00. Nonetheless, four million copies of this album were sold. Yes, that multiplies out to $200 million. The current value of the Nobel Prize, often divided among three people, is a little more than a million dollars.[1]

The sparse
lyrics of Tusk don't mention a walrus (aptly done by The Beatles in I Am the Walrus), or an elephant. Some Internet commentators suggest that tusk is a phallic allusion. As Sigmund Freud so famously did not say,[2] "Sometimes, a cigar is just a cigar." I side with the school of music that believes that lyrics are intended to make sense only in ballads. Animal tusks are present on the walrus, elephant, warthog and narwhal, among others. They serve as digging and gripping tools, defensive weapons, and a show of sexual fitness.

Tusk ivory was found to be a useful material for jewelry and ornaments. Historically, such uses did not consume too much ivory, but all that changed towards the end of the nineteenth century when mass quantities of elephant tusk ivory were used for piano keys and billiard balls. Modern plastic composites have replaced ivory in these applications because elephants were becoming an endangered species and the ivory trade is highly regulated. However, illegal trade in ivory is a persistent problem.[3]

Ivory trade, circa 1900

The ivory trade in better times.

Men with ivory tusks in Dar es Salaam, sometime between 1880 and 1923

The Convention on International Trade in Endangered Species (CITES) prevents ivory trade between member countries, although old ivory articles are exempt.

(Library of Congress photograph, cph.3c02973, via Wikimedia Commons.)

The Convention on International Trade in Endangered Species (CITES) bans the sale of recent ivory between signatory nations, but it allows the sale of some old ivory and ivory artifacts created before the ban. This leaves a loophole exploited by poachers who claim that their ivory is old ivory and legal under the convention. Poaching is responsible for about 30,000 elephant deaths per year, and only about 423,000 African elephants are left, so elephants are still threatened with extinction.[4-6]

An international team of scientists has just published their research into an age test for ivory in the Proceedings of the National Academy of Sciences. Team members were from the University of Utah (Salt Lake City, Utah), the University of Arizona (Tucson, Arizona), the University of Michigan (Ann Arbor, Michigan), Colorado State University (Fort Collins, Colorado), Save the Elephants (Nairobi, Kenya), Oxford University (Oxford, United Kingdom), and the Kenya Wildlife Service (Nairobi, Kenya).

Raw ivory from Asian elephants has been banned since 1975, and ivory from African elephants since 1989. African ivory items are legal in the US only if imported before 1989. The problem, of course, is dating ivory for enforcement.[5] 86,000 pounds of illegal ivory were seized globally in 2011, which is the production of almost 6,000 elephants. A kilogram of ivory is worth about a thousand dollars.[6]

Figure caption

This elephant in Kenya's Samburu National Reserve is believed to have the largest tusks at that reserve.

(University of Utah photograph by Thure Cerling.)

The dating method detects carbon-14 (14C) deposited in tusks. Above-ground nuclear weapon testing from 1952-1962 nearly doubled carbon-14 in the atmosphere, where it worked itself into the food chain.[4-5] The level declined after 1962, but the isotope is still present in the environment.[4] The isotope level in tusks and teeth reveal the year that an animal died.[5]

Accelerator mass spectrometry was used in the published method, since this analytical technique requires a very small specimen for analysis.[5] Cesium atoms impact the specimen to dislodge carbon atoms which are isotopically analyzed.[5] Calibration was done with specimens from 29 animals from 1905-2008. Pre-1955 ivory is easily identified by its low levels of carbon-14.[5] Interestingly, the ban on ivory trade made it difficult to obtain the most recent specimens. One Utah zoo elephant, and another elephant that died of natural causes in Kenya, provided that material.[6]

Aside from verifying pre-nuclear testing ivory, the method is highly accurate in determining the year of death for animals killed after 1955.[5] Vegetation is clearing the atmosphere of carbon-14, so the method won't be applicable in fifteen years time when the atmosphere returns to pre-nuclear testing levels.[5]

Says the study's principal author, geochemist Kevin Uno, who did the research for his Ph.D. thesis at the University of Utah,
"The dating method [which costs about $500 per specimen] is affordable and accessible to government and law enforcement agencies... It has immediate applications to fighting the illegal sale and trade of ivory that has led to the highest rate of poaching seen in decades."[5]


  1. Catherine Rampell, "For Nobel Winners, a Smaller Cash Prize," New York Times Blogs, June 11, 2012.
  2. Sometimes a Cigar Is Just a Cigar Quote Investigator August 12, 2011.
  3. Iain Douglas-Hamilton, "Time Running out to Save Elephants from Ivory Trade," National Geographic, January 31, 2013.
  4. Kevin T. Uno, Jay Quade, Daniel C. Fisher, George Wittemyer. Iain Douglas-Hamilton, Samuel Andanje, Patrick Omondih, Moses Litoroh and Thure E. Cerling, "Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensics and stable isotope (paleo)ecology," Proc. Natl. Acad. Sci., Online before Print (July 1, 2013), doi: 10.1073/pnas.1302226110.
  5. Nuke Test Radiation Can Fight Poachers, University of Utah Press Release, July 1, 2013.
  6. New Forensic Technique May Help Track Illegal Ivory, Columbia University Press Release, July 1, 2013.

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