Researchers from Norway and Namibia in collaboration with the Ministry of Environment and Tourism, have investigated the stress levels of elephants inside Ethosa National Park and of elephants living in the areas surrounding the park. The scientists have found out that elephants outside the national park are more stressed.
The research team from the Norwegian Institute for Nature Research (NINA) and the Norwegian University of Science and Technology (NTNU) found out that the hormones in dung as a stress indicator for elephants. Stress leads to increased levels of the stress hormone glucocorticoid in the bloodstream. The products of the metabolized stress hormone, so-called metabolites, are excreted into the intestines. Thus, stress levels can be measured by collecting dung samples.
However, this method is problematic when studying larger animals, and endangered species in particular, as they need to be immobilized before sampling. Both the administration of tranquillizers and the subsequent handling can be stressful to the animal and may influence the test results.
“The method we have used is noninvasive and better with regard to the well-being of the elephants,”
says Roel May, senior researcher at NINA. He added that method gives the researchers a more accurate measure of the long-term stress levels, which means that is a much better indicator of elephants’ chronic stress.
As it turns out the concentration of metabolites were one and a half times higher in elephants living in the Kunene region than in elephants living inside Etosha National Park. In other words, elephants living outside the park are clearly more stressed than elephants living in the park itself.
“This is connected to the extent of human-induced disturbances outside Etosha National Park,”
says Craig Jackson, the researcher at NINA. His team saw both smaller herd sizes and fewer calves per female in the Kunene region than inside the park. However, further studies are needed to determine if it is the stress level that is having a negative impact on fertility and herd size, say the Norwegian researchers.