Andrea Turkalo/Provided

African forest elephants at the Dzanga bai in the Central African Republic.

Because forest elephants are one of the slowest reproducing mammals in the world, it will take almost a century for them to recover from the intense poaching they have suffered since 2002. Not only does it take more than two decades for female forest elephants to begin reproducing, they give birth only once every five to six years.

These are the findings from the first-ever study of forest elephant demography, published Aug. 30 in the Journal of Applied Ecology.

There are two species of elephants in Africa: Savannah elephants make up the majority across the continent, with smaller numbers of the more diminutive forest elephants restricted to the tropical forests. Forest elephants have experienced serious poaching, driving an estimated population decline of 65 percent between 2002 and 2013. Their low birth rates mean it will take forest elephants at least 90 years to recover from these losses, according to researchers from the Cornell Lab of Ornithology’s Elephant Listening Project, the Wildlife Conservation Society, Colorado State University and Save the Elephants.

The team used decades of intensive monitoring data that recorded births and deaths of the elephants that live in the Dzanga Bai in Central African Republic, part of the UNESCO World Heritage Sangha Trinational area.

For the study, Andrea Turkalo, a Wildlife Conservation Society scientist, collected the detailed data on the Dzanga elephants despite tough logistical challenges and political instability.

Turkalo recorded observations from 1990 to 2013 during nearly daily visits to a mineral-rich forest clearing, or bai, that attracts elephants and other wildlife. The authors used these data to uncover the age at which the forest elephants had their first calves, the length of time between calves and other behavioral observations. The results revealed forest elephants begin breeding later and have much longer calving intervals compared with savannah elephants, meaning their population takes much longer to increase.

According to Turkalo: “Female forest elephants in the Dzanga population typically breed for the first time after 23 years of age, a markedly late age of maturity relative to other mammals. In contrast, savannah elephants typically begin breeding at age 12. In addition, breeding female forest elephants only produced a calf once every five to six years, relative to the three- to four-year interval found for savannah elephants.”

The authors speculate the low birth rate is due to the challenges of living in a tropical forest, where new plant growth is mostly limited to the canopy.

“While we think of tropical forests as incredibly productive areas, most production occurs in the high canopy inaccessible to ground-dwelling species. In addition, vegetation in tropical systems is laden with compounds to defend their leaves from herbivores. This means accessing resources is challenging for terrestrial fauna,” said Peter Wrege, director of the Elephant Listening Project.

“This information is essential to assessing the species status and projecting population decline in the face of illegal killing,” said George Wittemyer, chair of the scientific board of Save the Elephants and a professor of wildlife conservation at Colorado State University. “Legislation regarding ivory trade must consider the collateral effects on forest elephants and the difficulties of protecting them. Trade in ivory in one nation can influence the pressures on elephants in other nations.”

The paper’s findings show the forest elephant is particularly susceptible to poaching, vital information for debates and upcoming policy legislation regarding the legality of ivory trade to be decided at the International Union for Conservation of Nature and Natural Resources’ World Conservation Congress and the Convention on International Trade in Endangered Species conference in September.

Failing to protect forest elephants would also damage Central African forests, which are vitally important for absorbing climate change gases.

Forest elephants have critical ecological roles in these forests, and many tree species rely on the elephants to disperse their seeds. Continued decline in forest elephant numbers and range is likely to drive severe changes to these ecosystems, making their conservation status a significant global issue.