Gibbons aren\u2019t singing in the rain: presence and amount of rainfall influences ape calling behavior in Sabah, Malaysia

Dena J Clink,Holger Klinck,Abdul Hamid Ahmad

doi:10.1038/s41598-020-57976-x

Dena J Clink, Holger Klinck + Show 1 more

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https://doi.org/10.1038/s41598-020-57976-x

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Abstract

Early morning calling occurs across diverse taxa, which may be related to optimal conditions for sound transmission. There exists substantial inter- and intra-specific variation in calling time which is influenced by intrinsic, social and/or environmental factors. Here, we investigate environmental predictors of calling in gibbons. We hypothesized that male solos— which occur earlier and tend to be longer than duets—would be more influenced by environmental variables, if earlier, longer calling bouts are energetically costly, and therefore limited by overnight energy expenditure. Our top model for male solo events included amount of rain in the previous 24 hours, and explained 30% of the variance, whereas the top model for duet events (which included presence and amount of rainfall) explained only 5% of the variance. Rain the previous night led to a later start time of male solos (~30 minutes), but our top model for duet start time did not include any reliable predictors. Male solo events appear to be more influenced by environmental factors, and duets may be influenced more by social factors. Our results are in line with previous studies that show that changes in overnight conditions —which may alter energy expenditure —can influence early morning calling behavior.

Highlights

Morning calling occurs across diverse taxa, which may be related to optimal conditions for sound transmission
We found that amount of rainfall in the previous 24 hours was a reliably negative predictor of male solo events, and that presence of rain the previous night led to an approximately 30 minute later start time of male solos
We did not find that minimum overnight temperature or lunar cycle had a reliable effect on gibbon calling events or male solo start time

Summary

Introduction

Morning calling occurs across diverse taxa, which may be related to optimal conditions for sound transmission. There exists substantial inter- and intra-specific variation in calling time which is influenced by intrinsic, social and/or environmental factors. Our results are in line with previous studies that show that changes in overnight conditions —which may alter energy expenditure —can influence early morning calling behavior. It has been proposed that animals call in the early morning because the conditions for sound transmission are best[2], but within the early morning calling activity there is a substantial amount of inter- and intra-specific variation in call timing. The energetic costs of calling in gibbons have not been quantified, available evidence suggests that performance of calling bouts may be related to energy balance and expenditure, in males[30]. A meta-analysis of 21 gibbon populations (across nine different species) found that when fruit availability was reduced, frequency or duration of calling bouts was reduced, and this effect was greater in males, and males at higher latitudes, where costs of thermoregulation are assumed to be higher[30]

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