The reproductive advantages of a long life: longevity and senescence in wild female African elephants.

Phyllis C Lee,C Elizabeth Webber,Cynthia J Moss,Victoria Fishlock

doi:10.1007/s00265-015-2051-5

Phyllis C Lee, C Elizabeth Webber + Show 2 more

Open Access

https://doi.org/10.1007/s00265-015-2051-5

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Abstract

Long-lived species such as elephants, whales and primates exhibit extended post-fertile survival compared to species with shorter lifespans but data on age-related fecundity and survival are limited to few species or populations. We assess relationships between longevity, reproductive onset, reproductive rate and age for 834 longitudinally monitored wild female African elephants in Amboseli, Kenya. The mean known age at first reproduction was 13.8 years; only 5 % commenced reproduction by 10 years. Early reproducers (<12.5 years) had higher age-specific fertility rates than did females who commenced reproduction late (15+ years) with no differences in survival between these groups. Age-specific reproductive rates of females dying before 40 years were reduced by comparison to same-aged survivors, illustrating a mortality filter and reproductive advantages of a long life. Overall, 95 % of fertility was completed before 50, and 95 % of mortality experienced by age 65, with a mean life expectancy of 41 years for females who survived to the minimum age at first birth (9 years). Elephant females have a relatively long period (c. 16 years) of viability after 95 % completed fertility, although reproduction does not entirely cease until they are over 65. We found no evidence of increased investment among females aged over 40 in terms of delay to next birth or calf mortality. The presence of a mother reproducing simultaneously with her daughter was associated with higher rates of daughter reproduction suggesting advantages from maternal (and grandmaternal) co-residence during reproduction.

Highlights

Long-lived species tend to show trends in ageing and fertility that are distinct from those of rapidly reproducing, short-lived species (Reed et al 2008; Hayward et al 2014), but species at both ends of the life history continuum can exhibit prolonged post-reproductive lifespans with potential advantages for both the survivors and their offspring (Croft et al 2015)
Maximum lifespan has been estimated at 74 years from tooth wear (Lee et al 2012) in wild female African elephants (Loxodonta africana) and ~80 years for Asian elephants (Lahdenperä et al 2014)
Females who died before the median longevity of 40 years had reduced reproductive rates for their age while females who survived the mortality filter sustained higher rates of reproduction throughout their lives

Summary

Introduction

Long-lived species tend to show trends in ageing and fertility that are distinct from those of rapidly reproducing, short-lived species (Reed et al 2008; Hayward et al 2014), but species at both ends of the life history continuum can exhibit prolonged post-reproductive lifespans with potential advantages for both the survivors and their offspring (Croft et al 2015). Maximum lifespan has been estimated at 74 years from tooth wear (Lee et al 2012) in wild female African elephants (Loxodonta africana) and ~80 years for Asian elephants (Lahdenperä et al 2014). Age-specific mortality and life expectancy have been presented for wild African elephants (Moss 2001; Gough and Kerley 2006; Foley and Faust 2010) and for working Asian elephants (Robinson et al 2012; Hayward et al 2014; Lahdenperä et al 2014). We explore whether similar trade-offs between reproductive rate and survival exist among wild female African elephants

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