In long-lived social species, older individuals can provide fitness benefits to their groupmates through the imparting of ecological knowledge. Research in this area has largely focused on females in matrilineal societies where, for example, older female African savannah elephants (Loxodonta africana) are most effective at making decisions crucial to herd survival, and old post-reproductive female resident killer whales (Orcinus orca) lead collective movements in hunting grounds. in contrast, little is known about the role of older males as leaders in long-lived social species. By analysing leadership patterns of all-male African savannah elephant traveling groups along elephant pathways in Makgadikgadi pans national park, Botswana, we found that the oldest males were more likely to lead collective movements. our results challenge the assumption that older male elephants are redundant in the population and raise concerns over the biased removal of old bulls that currently occurs in both legal trophy hunting and illegal poaching. Selective harvesting of older males could have detrimental effects on the wider elephant society through loss of leaders crucial to younger male navigation in unknown, risky environments. During coordinated group movements certain individuals can consistently arise as "leaders" with a regular influence over group decisions, with high dominance rank 1 , bold temperament 2 and greater age (often associated with enhanced knowledge or experience 3) noted as common traits characterising leaders (for review, see 4). Whilst in some cases leadership can be a passive process, a consequence of simple consensus decisions to maintain group cohesion 5 , in other cases leaders actively communicate their intent to recruit followers 6. In long-lived species, older individuals often respond more appropriately to complex, changing environments 7,8 , providing substantial fitness benefits to younger group mates. For example, older matriarchs are more effective at mobilising groups in response to predation threats and conspecifics in female African savannah elephants (Loxodonta africana) 8,9 , Similarly, in resident killer whale (Orcinus orca) groups there is a greater reliance on older, post-menopausal females as leaders of hunting groups in years of low salmon abundance 10. Non-human research in this area has tended to focus on females and less attention has been given to the potential for old males to act as repositories of ecological knowledge and leaders in long-lived social species. In many social mammals, males are often assumed to be replaceable because they are typically the dispersing sex 11 , and old males may be reproductively redundant, which is commonly used as an argument to support the legal trophy hunting of old males in many species 12,13. This combined with desirable features such as larger body size and ornaments, leads to selective harvesting of older males in many species, including the African savannah elephant 14. However, there is no reason to believe there would be sex-based differe...

Males in many large mammal species spend a considerable portion of their lives in all-male groups segregated from females. In long-lived species, these all-male groups may contain individuals of vastly different ages, providing the possibility that behaviours such as aggression vary with the age demographic of the social environment, as well as an individual's own age. Here, we explore social factors affecting aggression and fear behaviours in non-musth male African elephants ( Loxodonta africana ) aggregating in an all-male area. Adolescent males had greater probabilities of directing aggressive and fearful behaviours to non-elephant targets when alone compared to when with other males. All males, regardless of age, were less aggressive towards non-elephant targets (e.g. vehicles and non-elephant animals) when larger numbers of males from the oldest age cohort were present. The presence of older males did not influence the probability that other males were aggressive to conspecifics or expressed fearful behaviours towards non-elephant targets. Older bulls may police aggression directed towards non-elephant targets or may lower elephants’ perception of their current threat level. Our results suggest male elephants may pose an enhanced threat to humans and livestock when adolescents are socially isolated, and when fewer older bulls are nearby.

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A common behavioural interaction between male African elephants is for an actor to direct his trunk to contact a same sex conspecific’s mouth, temporal gland, or genital region. Such behaviours are often referred to as “greetings”. Along with its inherent tactile element, these behaviours also likely provide olfactory information to actors concerning aspects of the target’s phenotype, including sexual status, feeding history, individual identity, and emotional state. Here, we explore whether the age and novelty of potential interactors affect the choice of individuals targeted by male African elephants for these trunks to scent emitting organ (SEO) behaviours at social hotspots in a male-dominated area. Male elephants of all ages, except older adolescents aged 16–20 years, preferentially targeted elephants of the same age class for trunk-to-SEO behaviours. Elephants younger than 26 years did not direct trunk-to-SEO behaviours to mature bulls (26+ years) more than expected by chance, suggesting these behaviours are not primarily used for younger males to establish contact with, or obtain information from or about older, more experienced individuals. We also found no evidence that males directed these behaviours preferentially to new individuals they encountered at male aggregations (compared to those they arrived in groups with), suggesting these behaviours are not primarily employed by males as a reunion display to establish relationships between new individuals or update relationships between familiar individuals separated over time. Age-mates may be preferentially targeted with these behaviours as a means to facilitate further interaction with partners (e.g., for sparring activity), or as a safe way to assess relative dominance rank in similarly aged and hence, size and strength, matched dyads. Our results suggest male African elephants use close contact trunk-to-SEO behaviours continuously over time, to facilitate positive relationships, test willingness to interact, and assess aspects of phenotype, between males occupying the same ecological space.