Chaos and Cohesion: Consequences of social disruption and leadership loss for African elephant families (#30)
Female elephants live in family units, where cooperative calf-rearing and ecological decision-making contribute to individual survival and reproductive success. The well-protected elephant population in Amboseli, southern Kenya, has provided baseline data on demography and behaviour since 1972. While family units typically have stable membership, fission-fusion sociality allows females to minimise the costs of grouping while maintaining valuable relationships with family members and close associates (friends). Association choices when grouping depend partly on the personality of the matriarch: older, experienced (and dominant) females act as an attractive social focus and their knowledge buffers risks for younger family members and close associates. An extreme drought in 2009 caused the death of 95% of females over 50 years of age, some of which had led their families as matriarchs for more than three decades. We demonstrate that matriarch loss can cause temporary family fragmentation, reduces time spent in groups with former close associates, and in some cases results in permanent fission of a family into new units. We present the demographic consequences of the 2009 extreme mortality pulse with data on age-specific within-family reproductive rates, interbirth intervals and calf survival pre- and post-matriarch loss. Our results improve understanding of the consequences of extreme mortality for elephant populations and highlight their potential for recovery.