Large family entering Ikémine Bai, Gabon © Marie-Amélie Forin-Wiart

Ecology

(Above) A typical extended social grouping of forest elephants: A mature female with three dependent offspring accompanied by her oldest daughter (last on the right) and the daughter’s calf. Once they reach their 20s, female forest elephants give birth about every five years. Based on the length of the tusks, the matriarch’s youngest (in the middle of the huddle) is about 18 months old.

Forest elephants are now accepted as a unique species of elephant (Loxodonta cyclotis), distinct from their better-known cousin, the African savannah (or bush) elephant (L. africana). This designation reinforces what scientists have always recognized: that forest and savannah elephants have  very different ecologies.

Elephants are the largest of all terrestrial mammals and the three extant species (the two African species plus the Asian elephant, Elephas maximus) share many life-history characteristics. They have a natural life span of 60-70 years and mature slowly, reaching puberty in their early teens. A recently published study revealed that forest elephants have a considerably slower reproductive rate than the other species of elephant. Although females are fertile at about age 13 (as are savannah elephants), the average forest elephant female does not have her first baby until 23 years of age—ten years older than for savannah elephants (1). Forest elephants also separate sequential births by more than five years, while for savannah elephants this is closer to four years. Together with the poaching pressure these populations are experiencing, this very low reproductive rate makes the future of forest elephants more precarious than previously thought.

The rainforests of Central Africa (second only to the Amazon in extent) have profoundly shaped both the diet and the social system of forest elephants. Elephants eat large quantities of fruit, leaves and the bark of trees as they wander in small family units, usually comprised of a mother and one or two of her dependent offspring. Although suitable browse is probably found in most parts of the forest (elephants are generalists, so many species of plant are eaten), fruit trees and mineral deposits are both spatially clumped. This has probably selected for the smaller group sizes that we see in forest elephants compared to their savannah cousins. Forest elephant movements are also influenced by forest clearings (called “bais” by the local Bayaka) which provide mineral supplements to their diet and facilitate social interactions. Individuals have been known to travel over a hundred kilometers to reach these bais, the only known places where large numbers of forest elephants gather to meet, greet friends and family, play, and mate.

More than half of a forest elephant’s diet consists of various tree parts, such as leaves and bark, and they are notorious fruit-lovers. In one study, fruit remains were found in about 83% of dung piles examined by the researchers! Elephants have even developed well-used paths that connect forest clearings and favored fruiting trees. By dispersing fruit seeds after digestion, forest elephants have created corridors abundant with their favorite fruits. Their role as rain forest engineers further underscores the critical importance of forest elephants to their habitat.

Forest Elephants

 

References:

1. Turkalo et al.(2017). Slow intrinsic growth rate in forest elephants indicates recovery from poaching will require decades. J.Appl.Ecol. 54(1):153-159.

2. Blake, Stephen and Clement Inkamba-Nkulu (2004). Fruit, minerals, and forest elephant trails: do all trails lead to Rome? Biotropica 36:392-401.

3. Klaus, G., C. Klaus-Hugi, and B. Schmid (1998). Geophagy by large mammals at natural licks in the rain forest of the Dzanga National Park, Central African Republic. Journal of Tropical Ecology 14:829-839.

4. Turkalo, A. and J. M. Fay (2001). Forest elephant behavior and ecology: Observations from the Dzanga saline. In W. Weber, L. J. T. White, A. Vedder, and L. Naughton-Treves (Eds.). African rain forest ecology and conservation, pp. 207–213. Yale University Press, New Haven, Connecticut.

5. White, L.J.T., C.E.G. Tutin, and M. Fernandez (1993). Group composition and diet of forest elephants, Loxodonta africana cyclotis Matschie 1900, in the Lope Reserve, Gabon. African Journal of Ecology 31:181-199.