The project started in January 2016 with monthly field data collection on elephant biosamples and demographic parameters in Myanmar, with the goal of compiling a unique combination of monthly biodata and demographic data on this rare model of ageing patterns in extremely long-lived mammals. Although both covid19 and the critically changed political situation in Myanmar during the project duration posed major challenges to some of the project aims, over the entire project duration, the team completed the extraction and lab analysis of almost all samples, health parameters and ageing-rate measures collected.
The team in Turku then conducted extensive statistical analysis of these data to address the project main scientific aims. These analyses have led, for example, to the following major discoveries:
1. By using the multigenerational demographic dataset of our semi-captive Asian elephants combined with measures of body size, we have quantified how maternal age affects offspring condition, age-specific reproductive success and long-term survival. We show that offspring born to older mothers display reduced overall survival, and higher age-specific reproductive success, but reduced survival of their own progeny. Our results suggest a persistent effect of maternal age on fitness across generations for the first time in a naturally occurring mammalian population.
2. We have also found that grandcalves from young mothers (<20 years) had 8 times lower mortality risk if the grandmother resided with her grandcalf compared to grandmothers residing elsewhere. Resident grandmothers also decreased their daughters’ inter-birth intervals by one year. Our findings that grandmother’s presence was highly beneficial for grandcalf survival particularly among young mothers and the daughters were also able to reproduce more rapidly in the presence of their mothers in elephants have implications for our understanding of the evolution and selection pressures on post-reproductive lifespan in general, as well as on dispersal and social system in elephants specifically.
3. Our extensive data on health, molecular and physiological measures of senescence have allowed determining the underlying mechanistic causes of senescence alongside its consequences. Although documenting how different age-related changes in health accelerate ageing at a mechanistic level is key if we are to better understand the ageing process, few studies, particularly on natural populations of long-lived animals, have investigated age-related variation in biological markers of health and sex differences therein. We showed that pronounced differences in haematology, blood chemistry, immune, and liver functions among age classes are also evident under natural conditions in this extremely long-lived mammal. We provide strong support that overall health declined with age, with progressive declines in immune and liver functions similarly in both males and females. These changes parallel those mainly observed to-date in humans and laboratory mammals, and suggest a certain ubiquity in the ageing patterns.
4. We have also shown that wild-captured elephants, suffering from adverse early events, had markedly lower survival and reproduction compared to captive-born elephants in timber camps, and that the harmful effects of capture on survival lasted for several years or even decades. In parallel, we have shown the mechanistic basis for such effects, documenting in detail how adverse early-life stress in the form of taming affects health, physiological measures of ageing and stress longitudinally.
These and other results have been published thus far in 30 peer-reviewed articles, including high-impact publications e.g. in Nature Communications, and with several further articles currently in press, under review, and in preparation. They have also been widely disseminated in press releases, social media, and presentations ranging from The World Economic Forum, SLUSH and scientific conferences to primary schools and other broad public events.
