Masturbation in a male Phayre's langur, &amp;lt;i&amp;gt;Trachypithecus phayrei&amp;lt;/i&amp;gt;

Md Shalauddin,Md Jayedul Islam,Tanvir Ahmed

doi:10.5194/pb-8-43-2021

Abstract

Abstract. Masturbation is a common auto-sexual behaviour in humans but is not explicitly known in a major portion of non-human primates. We report the first masturbatory behaviour in a male Phayre's langur, Trachypithecus phayrei, observed in a semi-evergreen forest in northeastern Bangladesh. Like other Asian colobines, the multi-male–multi-female groups of the Phayre's langur suggest a multilevel social organization and a complex hierarchy among males. The lack of sexual opportunity could result in masturbation and sperm competition among males. However, sperm competition is reported to be low in such non-seasonal breeders. Hence, we suggest an adequate characterization of the socio-sexual behaviour and reproductive strategies of this globally endangered primate in order to demonstrate the causes, cost and consequences of masturbation. We also urge further scientific exploration into masturbation among primates due to its evolutionary and conservational significance.

Highlights

From February to April 2017, we followed a Phayre’s langur group named “PL1” in Lawachara National Park as part of our habituation process for a year-long study on their behavioural and feeding ecology
Masturbation has been observed in a number of Asian colobines in the past, including 22 species of the Trachypithecus genus; masturbation has been reported in T. cristatus (Bernstein, 1968), T. poliocephalus (Hendershott et al, 2018) and T. francoisi (Hu, 2007) in the wild
Masturbation might be beneficial with respect to severe sperm competition (Baker and Bellis, 1993) by increasing the chances of fertilizing the egg when mating with a newly fertile female: masturbation in males allows for the production of new sperm with enhanced fitness by flushing out old and low-quality sperm from the genital tract (Thomsen and Sommer, 2015)

Summary

Introduction

From February to April 2017, we followed a Phayre’s langur group named “PL1” in Lawachara National Park as part of our habituation process for a year-long study on their behavioural and feeding ecology. Feet or mouth to stimulate their genitals until ejaculation occurs, whereas females exhibit extensive sophisticated behaviours including stimulation of the anogenital and breast regions using various “tool-like” substrates (Thomsen and Sommer, 2015). We report an observed masturbation event involving a male Phayre’s langur in Lawachara National Park, a 1260 ha semi-evergreen forest in northeastern Bangladesh.

Results

Conclusion