Abstract
Free-ranging African elephants live in a fission-fusion society, at the centre of which is the matriarch. Matriarchs are generally older females that guide their families to resources and co-ordinate group defense. While much is known about elephant society, knowledge is generally lacking about how age affects the physiology of wild elephants. Investigation of the ovarian activity of free-ranging elephants could provide insight into the reproductive ageing process, with implications for population management. Faecal samples were collected from 46 individuals ranging in age from 14 to 60 years for a 2-year period, and progestagen metabolite analyses were used to examine relationships between social status, age, season, and ovarian activity in female elephants in Addo Elephant National Park, South Africa. Social status was the strongest predictor of faecal progestagen metabolite concentrations in non-pregnant elephants, with grand matriarchs (n = 6) having the lowest values compared with matriarchs (n = 21) and non-matriarch females (n = 19). Likewise, social status and age were the strongest predictors of faecal progestagen metabolite concentrations in pregnant elephants (n = 27). The number of years since a non-pregnant female gave birth to her last calf (post-partum duration) was longer for older females with a higher social status, as well as during the dry season. Our results indicate that social standing and age of elephants are related to reproductive function, and that older females exhibit reductions in ovarian capacity. These results expand our understanding of reproduction and fertility throughout an elephant's lifespan, and the factors that impact gonadal function in free-ranging females. Given that possible over-abundance of elephants in areas such as Addo Elephant National Park is fuelling the debate over how best to manage these populations, knowledge about the reproductive potential of high-ranking females can provide managers with biological data to identify the best candidates for controlling growth through translocation or contraception.
Highlights
In the wild, African elephants (Loxodonta africana) live in a fission–fusion society (Archie et al, 2006), and adult females and their offspring form the basis of the family unit (DouglasHamilton, 1972; Dublin, 1983; Archie et al, 2006)
Social status was the strongest predictor of faecal progestagen metabolite concentrations in non-pregnant elephants, with grand matriarchs (n = 6) having the lowest values compared with matriarchs (n = 21) and non-matriarch females (n = 19)
The average faecal progestagen metabolite (FPM) concentration for samples collected from female African elephants in Addo Elephant National Park (AENP) was 107.45 ± 5.15 ng/g faeces, with FPM concentrations from pregnant animals being higher (130.88 ± 5.69 ng/g faeces) than those from non-pregnant females (95.93 ± 2.56 ng/g faeces; Table 2)
Summary
African elephants (Loxodonta africana) live in a fission–fusion society (Archie et al, 2006), and adult females and their offspring form the basis of the family unit (DouglasHamilton, 1972; Dublin, 1983; Archie et al, 2006). Females remain with the family group throughout their lives, whereas males leave their natal group at between 12 and 15 years of. The largest, eldest female in the family is usually the matriarch (Douglas-Hamilton, 1972; Poole et al, 1989; Archie et al, 2006). When multiple, related family groups fuse into a kinship group, the eldest matriarch (which we term the ‘grand matriarch’) generally adopts the leadership role (Wittemyer et al, 2007c)
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