The Magnificent Seven See the Dentist

©Photo: Jacqueline Codron

Ivory is being removed from the Letaba Elephant Museum - but not by thieves. A team of scientists, headed by JacquelineCodron and including Daryl Codron, Professor Julia Lee-Thorp and Professor Matt Sponheimer, have drilled holes in six tusks from six of the Magnificent Seven.

Using a special hand-held drill, they have extracted three ivory cores from each tusk. Each core is about 10mm in diameter, and will be used to determine the diet of the elephants during their life span.

"We hope to reconstruct the diets of these six elephants for most of their lifetimes, to see what they ate and how their diets were affected by various factors during the last century."

The cores taken from elephant tusks resemble a core taken from a tree, with visible growth rings. As an elephant's tusks grow, layers of dentine are laid down, forming light and dark bands that are protected on the external surface by enamel or cementum in elephants. 

The composition of the dentine is affected by what the elephants ate, and so by studying the various layers of dentine the dietary history of the elephant can be seen. There are also seasonal differences in dentine, with dark bands being produced when the tusk grows in winter and light bands from summer growth.

Three samples have been taken from each tusk, from the tip, middle and base of the tusks. This is because the oldest dentine is found at the tip, and the most recent at the base of the tusk. The holes do not go all the way through the tusk, as the core is broken off within the tusk. Professional artist Rob Wishart, who was involved in the original museum display, will refill the holes so that the tusks retain their aesthetic beauty. 

The team, including Sanparks staff and in particular, Fritz Rohr, have drilled one tusk each from Shingwedzi, Dzombo, Ndlulamithi, Kambaku, Phelwana and Nhlangulene. This gives them cores from three elephants that lived in the north of the park, and three from the south.Using a diamond tipped mini-drill the researchers will sample various growth lines in each core. Each core is expected to yield about 30 powder samples. These will then be analysed using a Stable Light Isotope Ratio Mass Mpectrometer, which will focus on carbon and oxygen atoms. The ratio of the different molecular weight carbon atoms, carbon-13 and carbon-12, will provide information on what kinds of plants the elephants ate. The ratio of oxygen-18 to oxygen-16 atoms will give an idea of rainfall and temperature.
Once the results are obtained, they can be compared to rainfall data for the Kruger Park, and Jacquelinecan then see if droughts and other environmental factors have influenced the elephant's diets.Carbon atoms can be used to see what the elephants ate because grasses have a different method of photosynthesis to woody plants like trees and shrubs. The different photosynthetic methods produce different amounts of carbon-13 in the plant matter, which then shows up in the dentine of elephants when they eat grass-rich or shrub-rich diets.
"It is therefore possible to analyse sections of the ivory, band for band, and record how the elephant's diet has changed during his lifetime. It is also possible to link these changes to other factors like rainfall, drought, climate and management policies," says Jacqueline.
Jacqueline says that if they can determine what influences what elephants choose to eat, they may be able to predict future trends in dietary behaviour if the environment changes, and incorporate this in effective management plans.
They are expecting to find differences between the northern and southern elephants, because there are mainly mopane trees in the north, while the south has a much greater variety of tree species. Jacqueline is also expecting to find out how the amount of grass in the elephants' diets changes in periods of low rainfall.

Once the data from the ivory rings has been matched with rainfall records, Jacqueline also hopes to be able to see what influences things like the construction of fences, artificial waterpoint provision, culling and fire regimes have had.

The results of the research will be displayed at the Letaba Elephant Museum.

By Melissa Wray

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