May 2, 2006 — Humans and elephants have disturbed dung beetle environments to such a degree that the beetles' food and shelter both literally and figuratively stink, according to a new study at a South African elephant reserve.
The study, which has been accepted for publication in the journal Biological Conservation, indicates nature reserves meant to preserve certain species can have a detrimental effect on other native creatures. It also adds to the large body of evidence that human activities can disturb ecosystems.
Scientists studied dung beetle populations at The Maputaland Center of Endemism in southern Mozambique and South Africa. In areas settled by humans, dung beetle species diversity dropped, since the only dung available was from people, their cattle and a handful of other animals.
"Different dung beetle species have preferences for different types or dung qualities," explained Melodie McGeoch, who worked on the study. "For example, some prefer dry over wet dung, course textured versus fine dung, different fiber contents or different sizes of the dropping/dung pad. To maintain a diverse dung beetle community, a diverse array of dung types is necessary."
McGeoch, an associate professor in the Department of Conservation Ecology and Entomology at South Africa's University of Stellenbosch, said food for dung beetles in the center's Tembe Elephant Park also lacks diversity. According to the researchers, the elephants are turning what was once a more shaded, species-rich sand forest habitat into a mixed woodland community.
"This means that the shade-loving dung beetles found in the sand forest (a rare type of tropical, dry forest) will disappear if elephants continue to open up and disturb sand forest habitat," McGeoch told Discovery News.
She added that dung beetles play a very important role in ecosystems by breaking down and removing dung, contributing to nutrient recycling, aerating soil and burying seeds embedded in the dung that are then able to germinate.
Robert Knell, a researcher in the School of Biological Sciences at the University of London's Queen Mary College, agreed.
"Obviously dung beetles are extremely important in many ecosystems: transporting dung down into the soil does all sorts of good things," he told Discovery News.
Knell and colleague Joanne Pomfret also studied dung beetles, but they focused on a horn that grows on a particular species, Euoniticellus intermedius.
Males use the appendage for fighting and for grabbing female mates. Incredible wrestling matches between males take place in underground dung beetle tunnels, which are dug by females. During the fights, the males hook their horns and try to push each other out of the desired female's tunnel.
Knell and Pomfret determined that horn size is more important for large than small males, but that the biggest-horned beetle usually wins. The findings recently were published in the journal Animal Behavior.
"It may be that the males with the biggest horns win because the horns act as a signal of fighting prowess and the rival males know that they will lose, or it may be that the large horns actually act as more efficient weapons during the fights, or it may be a combination of these two factors that leads to males with big horns winning fights," said Knell.
Both he and McGeoch hope humans will better manage habitats where dung beetles live.
McGeoch said, "As humans, we have brought this difficult situation on ourselves by confining wildlife to comparatively small, fenced-off areas. As a consequence, active and often tough management decisions have to be made in an attempt to conserve as much biodiversity as possible in the few small protected areas left."
