This study presents the first detailed analysis of the sexual behaviour and mating tactics of Peale’s
dolphins (Lagenorhynchus australis) along the southern coast of Punta Arenas, Chile. Using
Unmanned Aerial Vehicles (UAVs), we conducted 45 field trips, recording 171 groups of dolphins.
These follows encompassed 40 hours of effective UAV recording, of which 5 hours 29 minutes
captured mating behaviours. These UAV observations documented 2844 behavioural events,
revealing diverse and complex sexual behaviours. Observations showed polygynandry in Peale’s
dolphins, where multiple males mate with multiple females. Mating behaviours were typically seen
in groups without juveniles and formed of 3 adults (2 males and 1 female), although males per
group ranged from 1 to 5, while females were limited to 2. Females exhibited significant evasive
behaviours in response to high male-to-female ratios, suggesting tactics to assess male fitness and
avoid unwanted mates through signal discrimination, evasive behaviours, and multiple matings. The
copulation rate per male remained consistent regardless of group size, suggesting non-competitive
scramble competition for males’ mating strategy. These findings highlight UAVs' effectiveness as a
non-invasive tool to study behaviour in free-swimming cetaceans and provide insights into the
behaviour of coastal species, gathering essential knowledge to develop adapted conservation
measures.
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