Musth and sexual selection in elephants: a review of signalling properties and potential fitness consequences

Abstract

Sexual selection mediated by multimodal signals is common among polygynous species, including seasonally breeding mammals. Indirect benefit models provide plausible explanations for how and why mate selection can occur in the absence of direct benefits. Musth — an asynchronous reproductive state in male elephants — facilitates both inter- and intrasexual selection via indirect benefits, and it is further communicated through a multimodal signal. In this review, we synthesise existing evidence that supports the hypothesis that musth is a multimodal signal subject to sexual selection and that male elephants increase their direct fitness by propagating this signal while females accrue indirect benefits. Musth is characterised by a suite of physiological and behavioural changes, serving to facilitate copulation between the sexes, and via multisensory modalities musth conveys honest information about the condition of a male. Female elephants mate preferentially with musth males, increasing their own fitness in the absence of direct benefits. In addition, musth resolves dynamic dominance hierarchies among male elephants and often eliminates the need for costly physical combat. Future work in this field should investigate potential postcopulatory selection mechanisms in elephants, including sperm competition and cryptic female choice. These topics join other fundamental questions related to sexual selection, signalling, and indirect benefits that are still unanswered in elephants.

Understanding the spatial distribution and hot spots of collared Bornean elephants in a multi-use landscape

“…3 ). Differential choices may result from differences in individual knowledge and experience with people during past encounters, for example 70 , 71 .…”

The Chemical Ecology of Elephants: 21st Century Additions to Our Understanding and Future Outlooks

“…One of the critical findings up to this time was the determination that African elephants exhibited musth similar to what had been known for centuries by Asian elephants [14,15,29]. Males of both species dribble urine, secrete an odorous, viscous fluid from the temporal gland (i.e., temporal gland secretions, TGS), can act aggressively, and focus their energies on locating receptive females (reviewed in [23,[30][31][32]). Common aspects of musth in behavior and apparent function supported investigating other similarities in the chemical ecology of Asian and African elephants.…”

“…These senses are covered elsewhere in this issue, so they will not be reviewed here. Nevertheless, we realize the need for research on the interactions across the senses in both perception and signaling [23].…”

Non‐visual cues and indirect strategies that enable discrimination of asymmetric mates

“…Claw raking felids (cats) alternate their fore paws to scratch surfaces wherein scent glands in each foot could leave bilaterally distinguishable chemosensory cues (Figure 1b ; reviewed in Harmsen et al ( 2010 )). Analogues function for other sexual secretions in mammals can be speculated: Temporal gland secretions in bull elephants during ‘Musth’ (Chelliah & Sukumar, 2013 ; LaDue et al, 2021 ); apocrine gland fields on wrists of lemurs, used in shoulder‐rubbing and wrist‐marking behaviors (Charpentier et al, 2008 ); anal gland and sac secretions in bears (Sergiel et al, 2017 ); and facial gland secretions of chiropteran species (Rehorek et al, 2010 ). These cases hint toward the innumerable examples that one could consider in other taxa (reptiles, amphibians, fishes, and insects) that have evolved higher orders of chemosensory communication (Houck, 2009 ; Johansson & Jones, 2007 ).…”