Abstract1. The physical and behavioral characteristics and the temporal patterning of musth were studied over a ten-year period in a free-ranging population of African elephants. 2. Males spent more time in association with females during musth than during non-musth periods. 3. Males were more aggressive during their musth periods than during non-musth. 4. The occurrence and duration of musth were age-related: no male under 24 years was seen in musth; bouts of must among younger individuals were short and sporadic, while older males experienced longer more predictable periods of musth on an annual basis. 5. Although males in musth were observed year-round, the frequency of musth males was highest during and following the two rainy seasons and, in general, good rainfall years had higher frequencies of males in musth than did poor rainfall years. 6. The number of males in musth per month correlated closely with the number of females observed in estrus. However, since the period of estrus lasts only four to six days (Moss, 1983), while musth may last several months, the onset of musth was not necessarily triggered by the onset of estrus in a particular female. 7. The musth periods of different males were asynchronous and each male came into musth at a specific time of year. This period was relatively consistent from one year to the next, particularly among the older males. 8. Males in musth advertised their heightened sexual and aggressive state through visual and olfactory signals and by vocalizing. It is suggested that these signals function to announce identity, condition and location to both rival males and to potentially receptive females. 9. The physical and behavioral characteristics and temporal patterning of musth in African and Asian elephants are compared and found to be remarkably similar. 10. The physical and behavioral manifestations of musth in elephants are similar to those described for other male mammals during rut. Since estrus in female elephants is less clumped relative to most ungulates, male elephants have a different temporal pattern of rutting. Although the musth periods of male elephants are asynchronous the phenomenon can functionally be considered a rutting period.

The value of age is well recognized in human societies, where older individuals often emerge as leaders in tasks requiring specialized knowledge, but what part do such individuals play in other social species? Despite growing interest in how effective leadership might be achieved in animal social systems, the specific role that older leaders may play in decision-making has rarely been experimentally investigated. Here, we use a novel playback paradigm to demonstrate that in African elephants ( Loxodonta africana ), age affects the ability of matriarchs to make ecologically relevant decisions in a domain critical to survival—the assessment of predatory threat. While groups consistently adjust their defensive behaviour to the greater threat of three roaring lions versus one, families with younger matriarchs typically under-react to roars from male lions despite the severe danger they represent. Sensitivity to this key threat increases with matriarch age and is greatest for the oldest matriarchs, who are likely to have accumulated the most experience. Our study provides the first empirical evidence that individuals within a social group may derive significant benefits from the influence of an older leader because of their enhanced ability to make crucial decisions about predatory threat, generating important insights into selection for longevity in cognitively advanced social mammals.

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