Forest Elephant growth rate portends disaster
A recently published study¹ indicates that forest elephant population growth is severely limited by their slow reproductive rates. Furthermore, the nine years between 2002–2011 were particularly cruel; due to poaching, land use pressure, and other human-elephant conflicts, forest elephants suffered a 62% population decline and 30% habitat reduction². The authors argue that these calamitous threats are magnified by low birth rates and leave forest elephants facing extinction.
Based on 23 years of data from the Dzanga Bai in the Central African Republic, founding member of ELP, Andrea Turkalo, and her colleagues, Peter Wrege and George Wittemyer, determined growth and reproductive rates for this forest elephant population. During the study’s duration, the researchers observed that most forest elephant females had their first baby between the ages of 22 and 25. This is considerably older compared to when a savannah elephant first gives birth, at around 12–13 years old. In addition, forest elephants generally give birth only once every five years — as opposed to every three years for savannah elephants. Age and inter-birth intervals contribute to a worryingly low birth rate among forest elephants.
The study also elucidates the devastating impact of poaching on forest elephant populations. Almost half of annual deaths were attributed to human — not natural — causes. Low birth rates in combination with high mortality, due at least in part to poaching, slash average population growth to a mere 1.19% per year. At this rate, it could take nearly a century for forest elephants to recover just from the losses incurred since 2002, and there is a risk that will never happen.
While we are unable to expedite birth rates, we are in control of human-caused elephant killings. Without the pressure of poaching³, forest elephants have a far stronger chance of recovering. That would mean regaining a healthy, sustainable forest elephant population in our lifetimes, and that feels like something worth fighting for.
¹Turkalo, Andrea K., Peter H. Wrege, and George Wittemyer. “Slow intrinsic growth rate in forest elephants indicates recovery from poaching will require decades.” Journal of Applied Ecology (2016).
²Maisels, F., et al. (2013). “Devastating decline of forest elephants in Central Africa”. PLoS ONE 8(3): e59469.
³Rebecca Morelle. “Slow birth rate found in African forest elephants,” BBC News, August 31, 2016. http://www.bbc.com/news/science-environment-37224947.