Reduced older male presence linked to increased rates of aggression to non-conspecific targets in male elephants.

Connie R B Allen,Darren P Croft,Lauren J N Brent

doi:10.1098/rspb.2021.1374

Connie R B Allen, Darren P Croft + Show 1 more

Open Access

https://doi.org/10.1098/rspb.2021.1374

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Abstract

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.

Highlights

Since male fitness is mainly driven by the number of successful fertilizations [1], aggression in males is typically viewed through the lens of sexual competition, with a focus on direct mate guarding [2], defence of territory and resources to gain access to females [3], or establishment of dominance hierarchies in order to monopolize mating [4]
In long-lived species with distinct life-history stages, the possibility arises that differences in the ages of males in all-male groups may influence the aggressive behaviours that are performed by members [7,8,9,10]
Social isolation significantly predicted the likelihood of adolescents, but not adults, performing both aggressive and fear-based behaviours to non-elephant targets, with adolescent males more likely to perform both these behaviours when alone compared to when observed with other elephants

Summary

Introduction

Since male fitness is mainly driven by the number of successful fertilizations [1], aggression in males is typically viewed through the lens of sexual competition, with a focus on direct mate guarding [2], defence of territory and resources to gain access to females [3], or establishment of dominance hierarchies in order to monopolize mating [4]. We know comparatively little about the factors that influence aggressive behaviours in all-male groups. This represents an important gap in knowledge as many males spend the majority of their lives in such all-male groups. In long-lived species with distinct life-history stages (e.g. prolonged adolescent periods with higher investment in learning and development, and lower investment in reproductive activities), the possibility arises that differences in the ages of males in all-male groups may influence the aggressive behaviours that are performed by members [7,8,9,10]. Understanding the patterns of aggression in male elephants, including the nature and targets of this aggression, and how factors such as age and social context within all-male groups can influence these behaviours, is of paramount importance owing to its relevance to human safety and well-being

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