Auto-fellatio behaviour observed in the Indian Palm Squirrel Funambulus palmarum (Linnaeus, 1766)

Masturbation is an auto-sexual behaviour, a widespread phylogenetic trait in many taxa. Masturbation in squirrels was rarely reported. We observed an Indian palm squirrel  (Funambulus palmarum) doing the auto-fellatio activity away from the scurry in Bhavanisagar, Tamil Nadu. However, the auto-fellatio behaviour in F. palmarum is novel.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print) Masturbation is an auto-sexual behaviour, a widespread phylogenetic trait in many taxa, including non-mammalian species (Roth et al. 2022). Nonreproductive sexual behaviours are observed in birds, Bonobos, sheep, goats, cats, Cape Squirrels, Spotted Hyenas, and many other animals (Bagemihl 1999;Schwartz 1999;Waterman 2010;Balcombe 2011). Waterman (2010 reported that males under intense sperm competition might manipulate sperm quantity and quality through masturbation, which could waste sperm and decrease fertility. Masturbation is found to be a reason for lacking sexual opportunity or fulfilling sexual desire. Masturbation, however, was initially thought to be non-adaptive, but later researchers pointed out to be adaptive (Thomsen et al. 2003). Sperm flushing through masturbation is adaptive to increase the chance of having fertile sperm to have reproductive success (Baker & Bellis 1993;Bellis 1995). Masturbation is a self-directed action; the vertebrates use their hands directly and sometimes mouth by the suggestive term auto-fellatio (Waterman 2010). Extending to body parts, monkeys have been known to masturbate using stones as a part of tool use based on physiological responses (Cenni et al. 2022).
The Indian Palm Squirrel Funambulus palmarum is a rodent under the family Sciuridae and is widespread in the Indian subcontinent and Sri Lanka (Nowak 1999). They are known to breed throughout the year (Prasad 1951). Rodents perhaps exhibit masturbation behaviour; one such incident has been reported in the African Ground Squirrel Xerus inauris (Waterman 2010). This study presents an observation of auto-fellatio behaviour in an adult male Indian Palm Squirrel.
On 14 December 2018, an Indian Palm Squirrel was found on a Neem Tree Azadirachta indica during the evening hours in an agriculture field at Bhavanisagar, Tamil Nadu, India (11.4783 0 N, 77.1273 0 E). The squirrel's activity was observed to express an auto-fellatio behaviour (Image 1). The observation began with the male squirrel stimulating its genital organ using both hands for approximately six seconds.
The activity continued till the penis got appropriately erected. The squirrel held its penis by its forelimbs and was sucked by its mouth forward and back continuously. Subsequently, the sperm ejaculated at the end of the 26th second, and thereby we concluded it as masturbation. The action was performed with its whole mouth for 26 seconds, confirming the activity as an auto-fellatio behaviour and not a penis-cleansing behaviour. The male squirrel was found alone without any other individuals near for about a 10-m radius from the animal.
The auto-fellatio behaviour in animals has been attributed to various hypotheses, including relaxation and aggression reduction (Thomsen & Sommer 2015), serving as a sexual outlet, potential enhancement of sperm quality, energy reallocation, sexual display, rivalry demonstration, and even reduction of the risk of sexually transmitted infections (Waterman 2010). Considering that Indian Palm Squirrels are known to breed throughout the year, any of these hypotheses could potentially explain the occurrence of auto-fellatio behaviour in this species.
This observation calls for further research to comprehensively investigate the variety of factors contributing to non-breeding behaviours in Indian Palm Squirrels. The auto-fellatio behaviour observed in F. palmarum is novel and represents the first recorded instance to the best of our knowledge. Additional studies are needed to delve deeper into the motivations and implications of this behaviour, shedding more light on its significance within the context of squirrel biology and behaviour. www.threatenedtaxa.org www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.