Male Masturbation in Free-Ranging Japanese Macaques

Thomsen, Ruth; Soltis, Joseph

doi:10.1023/b:ijop.0000043350.75897.89

Cited by 27 publications

(28 citation statements)

References 23 publications

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“…During the 4-month breeding season, free-ranging macaque males ejaculate once daily by masturbation if they are restricted from mating, indicating that they continuously invest an energy of about 8.1 kJ day À1 into spermatogenesis independently of possible mating success (Thomsen and Soltis 2004). Males of higher social status were observed to ejaculate by mating with a female up to six times a day (unpublished data).…”

Section: Discussionmentioning

confidence: 96%

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How costly are ejaculates for Japanese macaques?

et al. 2006

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Much sexual selection theory is based on the idea that ejaculate is cheap. Since further details are unknown our aim was to determine the energy that primate males require for ejaculate production. We addressed this problem by measuring the energy content (in kJ) of ejaculates from Japanese macaques (Macaca fuscata) using standard bomb calorimetry. Then, we estimated the relative amount of energy that individuals require for ejaculate production by relating the net energy content of ejaculates to males' daily basal metabolic rate (BMR). Fresh macaque ejaculate contains 3.0 kJ ml(-1). Assuming a mean volume of 2.7 ml an average macaque ejaculate contains 8.1 kJ. Depending on the individuals' body mass (6-13 kg) and the number and volume of the ejaculates, macaque males are assumed to use between at least 0.8% and at most 6.0% of their BMR for ejaculate production per day during the breeding season. Even when regarding only the minimal energy investment of 0.8% of daily BMR for ejaculate production, clearly ejaculates come with some cost for primate males.

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Section: Discussionmentioning

confidence: 96%

“…Japanese macaques belong to those primate species in which captive as well as wild living males regularly masturbate, thus allowing the non-invasive collection of ejaculates (Enomoto 1974;Thomsen et al 2003;Thomsen and Soltis 2004).…”

Section: Methodsmentioning

confidence: 99%

How costly are ejaculates for Japanese macaques?

et al. 2006

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“…Male masturbation was much more frequent in two macaques species, in which hundreds of instances were observed over less than 1000 hours of observation collected over 1–2 yr (Nieuwenhuijsen et al. ; Thomsen & Soltis ). In free‐ranging Japanese macaques ( Macaca fuscata ), masturbation is more frequent in males of lower mating success and those of lower dominance rank (Thomsen & Soltis ; see also Inoue ).…”

Section: Introductionmentioning

confidence: 99%

Effect of Mating Activity and Dominance Rank on Male Masturbation Among Free‐Ranging Male Rhesus Macaques

2013

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The adaptive function of male masturbation is still poorly understood, despite its high prevalence in humans and other animals. In non-human primates, male masturbation is most frequent among anthropoid monkeys and apes living in multimale-multifemale groups with a promiscuous mating system. In these species, male masturbation may be a non-functional by-product of high sexual arousal or be adaptive by providing advantages in terms of sperm competition or by decreasing the risk of sexually transmitted infections. We investigated the possible functional significance of male masturbation using behavioral data collected on 21 free-ranging male rhesus macaques (Macaca mulatta) at the peak of the mating season. We found some evidence that masturbation is linked to low mating opportunities: regardless of rank, males were most likely to be observed masturbating on days in which they were not observed mating, and lower-ranking males mated less and tended to masturbate more frequently than higher-ranking males. These results echo the findings obtained for two other species of macaques, but contrast those obtained in red colobus monkeys (Procolobus badius) and Cape ground squirrels (Xerus inauris). Interestingly, however, male masturbation events ended with ejaculation in only 15% of the observed masturbation time, suggesting that new hypotheses are needed to explain masturbation in this species. More studies are needed to establish whether male masturbation is adaptive and whether it serves similar or different functions in different sexually promiscuous species.

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“…Researchers have also recently conducted other field studies with diverse themes, studied from different viewpoints and by different methodologies, that have included feeding ecology (Agetsuma 1995a, b, c;Hanya 2004a, b;Maruhashi and Takasaki 1996), feeding ecology in relation to seed dispersal (Agetsuma and Noma 1995;Noma and Yumoto 1997;Shibata 2000 Yumoto et al 1998), vocal and behavioral communication (Mitani 1986;Sugiura 1993Sugiura , 1998Sugiura and Masataka 1995;Tsukahara 1990), female reproduction and mating strategies (Matsubara and Sprague 2004;Soltis et al 2001;Takahata et al 1994bTakahata et al , 1995Takahata et al , 1998Thomsen 1997;Thomsen and Soltis 2004;Thomsen et al 2006), and intertroop male movements and life history (Sprague 1998;Sprague et al 1996Sprague et al , 1998Suzuki et al 1998b), but the present scope of field studies would focus more attention on individual survival strategy than before. Domingo-Roura et al (2004), Hayakawa and Takenaka (1999), Soltis (1999Soltis ( , 2002, Soltis et al (2000Soltis et al ( , 2001, Thomsen and Soltis (2004), and Thomsen et al (2006) studied female and male mating tactics via DNA analysis by collecting sperm and feces.…”

Section: Recent Scope Of Field Studies At Yakushimamentioning

confidence: 99%

“…Domingo-Roura et al (2004), Hayakawa and Takenaka (1999), Soltis (1999Soltis ( , 2002, Soltis et al (2000Soltis et al ( , 2001, Thomsen and Soltis (2004), and Thomsen et al (2006) studied female and male mating tactics via DNA analysis by collecting sperm and feces. Undoubtedly, the studies will contribute to our understanding of Yakushima macaques as a whole and give new insights on their social ecology and evolutionary biology.…”

Section: Recent Scope Of Field Studies At Yakushimamentioning

confidence: 99%

History and Present Scope of Field Studies on Macaca fuscata yakui at Yakushima Island, Japan

Yamagiwa

2008

Int J Primatol

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Field studies on Japanese macaques on Yakushima Island started in the mid-1970s, >25 yr after the emergence of Japanese primatology, in response to criticism of methods using provisioning and the desire to find the socioecological factors influencing the social life of macaques in natural habitats. We habituated macaques without provisioning mainly in the coastal warm-temperate forest and found that they lived in small troops with a high socionomic sex ratio. Observations of several troop fissions and troop takeovers by nontroop males suggest that Yakushima macaques have a different social organization from that of Japanese macaques in other habitats. For example, youngest ascendancy as the dominance relationhip among sisters, which usually occurs in provisioned troops, was absent in Yakushima macaques. We compared their ecological and social features with those of Japanese macaques at Kinkazan (cool-temperate forests) and found that abundance of high-quality foods may cause stronger intra-and intertroop competition at Yakushima. Female Yakushima macaques may more positively solicit nontroop males to associate with them during the mating season. Such a tendency may promote frequent male movement between troops and frequent troop fissions. Though ecological factors form social features of Japanese macaques, some features such as male association and movements between troops are not accounted for via socioecology. Recent field studies have focused on macaques living at higher altitudes in Yakushima and on individual survival strategies by taking diverse viewpoints and using new technologies. DNA analysis of fecal samples shows low genetic diversity and suggests the macaques' recent expansion from lowland to highland forests in Yakushima. The population censuses conducted annually indicate that the higher-altitude macaques have a larger home range but a similar group size versus their counterparts at low elevations. The unsolved issues in socioecology will pose a challenge to the younger generation of primatologists. Conservation of macaques and their habitat is one of our major activities at Yakushima. The level of Int J Primatol (Heritage Site by UNESCO in 1993. However, large-scale logging in the 1960s and 1970s caused the loss of macaque habitats and led to increased crop damage by them in the 1980s. We have proposed effective methods to protect cultivated fields from macaques as well as several plans for sustainable use of forests, such as ecotourism and a fieldwork course for university students. Local residents and researchers have created several nongovernment organizations (NGOs) to promote conservation and nature study at Yakushima. The role of local NGOs is particularly important to mitigate conflicts between people and wildlife. Though hundreds of macaques are still captured as pests annually in Yakushima, we continue the conservation measures and spread awareness of conservation in cooperation with the local NGOs.

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Male Masturbation in Free-Ranging Japanese Macaques

Cited by 27 publications

References 23 publications

How costly are ejaculates for Japanese macaques?

How costly are ejaculates for Japanese macaques?

Effect of Mating Activity and Dominance Rank on Male Masturbation Among Free‐Ranging Male Rhesus Macaques

History and Present Scope of Field Studies on Macaca fuscata yakui at Yakushima Island, Japan

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