Orangutan Sexual Behavior

Kunz, Julia; Noordwijk, Maria A. van; Schaik, Carel P. van

doi:10.1017/9781108943581.020

Cited by 5 publications

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“…Our results indicate that Sumatran orangutan females may view at least some males as a potential threat and increase locomotory support as a counter-infanticide strategy. Mothers might also change their behavior in the presence of males depending on their reproductive status, which is closely linked to the age of their current dependent offspring (Fairbanks & McGuire, 1987; Kunz et al, 2022; Scott et al, 2019). Furthermore, it is likely that not all males are a threat, and maternal behavior may vary based on whether a male is a resident or not (Fairbanks & McGuire, 1987; Kunz et al, 2022; van Noordwijk et al, 2023).…”

Section: Discussionmentioning

confidence: 99%

“…Mothers might also change their behavior in the presence of males depending on their reproductive status, which is closely linked to the age of their current dependent offspring (Fairbanks & McGuire, 1987; Kunz et al, 2022; Scott et al, 2019). Furthermore, it is likely that not all males are a threat, and maternal behavior may vary based on whether a male is a resident or not (Fairbanks & McGuire, 1987; Kunz et al, 2022; van Noordwijk et al, 2023). With a larger sample size, future studies should test the interaction effect of offspring age and male presence/absence and the effect of associating male’s familiarity on maternal investment.…”

Section: Discussionmentioning

confidence: 99%

“…Our results indicate that Sumatran orangutan females may view at least some males as a potential threat and increase locomotory support as a counterinfanticide strategy. Mothers might also change their behavior in the presence of males depending on their reproductive status, which is closely linked to the age of their current dependent offspring(Fairbanks & McGuire, 1987;Kunz et al, 2022;Scott et al, 2019).…”

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confidence: 99%

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Maternal behavior in Sumatran orangutans (Pongo abelii) is modulated by mother-offspring characteristics and socioecological factors

Revathe,

Mundry,

Utami-Atmoko

et al. 2024

Preprint

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Mammalian mothers flexibly invest in their offspring to maximize their lifetime fitness. Flexible maternal investment may be particularly important in large-brained species with prolonged maternal care, e.g., in great apes. We investigated the effects of socioecological factors and mother-offspring characteristics on nine maternal behaviors in wild Sumatran orangutans (Pongo abelii; N=22 mother-offspring pairs; over 11,200 hours of focal data; collected from 2007-2022) using generalized linear mixed models. The behaviors fall under four maternal functions: locomotory support (carrying), skill acquisition support (feeding in proximity, food transfer), protective proximity maintenance (body contact and proximity initiation, following), and independence promotion (body contact and proximity termination, avoiding). Mother parity was not significantly associated with any maternal behavior. Mothers were more likely to show locomotory support, skill acquisition support, and protective proximity maintenance toward younger than older offspring; whereas they were more likely to promote independence in older than younger offspring. Mothers with male offspring were more likely to show skill acquisition support to their offspring than those with female offspring. With increasing food availability, skill acquisition support reduced. With increasing association size, mothers were more likely to show protective proximity maintenance and less likely to promote independence. When males were present, mothers were more likely to show locomotory support to their offspring. Sumatran orangutan mothers thus flexibly adjust offspring directed behavior in response to prevailing socioecological factors and mother-offspring characteristics. Our findings add support to the evolutionary theory that mammalian mothers flexibly invest in their offspring.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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Maternal behavior in Sumatran orangutans (Pongo abelii) is modulated by mother-offspring characteristics and socioecological factors

Revathe,

Mundry,

Utami-Atmoko

et al. 2024

Preprint

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“…Orang-utans are a suitable species to study cognitive biases associated with sexual selection. Unique among mammals, orang-utans are characterised by male bimaturism: while some adult males quickly develop secondary sexual characteristics, such as a throat sac, large body size, and conspicuous flanges on the sides of the face, other males experience developmental arrest of these characteristics 26 . These so-called unflanged males are sexually mature and can successfully reproduce, although females prefer to mate with fully developed flanged males when they are fertile 27 .…”

Section: Introductionmentioning

confidence: 99%

No immediate attentional bias towards or choice bias for male secondary sexual characteristics in Bornean orang-utans (Pongo pygmaeus)

Roth,

Samara,

Perea-Garcia

et al. 2024

Sci Rep

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Primate faces provide information about a range of variant and invariant traits, including some that are relevant for mate choice. For example, faces of males may convey information about their health or genetic quality through symmetry or facial masculinity. Because perceiving and processing such information may have bearing on the reproductive success of an individual, cognitive systems are expected to be sensitive to facial cues of mate quality. However, few studies have investigated this topic in non-human primate species. Orang-utans are an interesting species to test mate-relevant cognitive biases, because they are characterised by male bimaturism: some adult males are fully developed and bear conspicuous flanges on the side of their face, while other males look relatively similar to females. Here, we describe two non-invasive computerised experiments with Bornean orang-utans (Pongo pygmaeus), testing (i) immediate attention towards large flanges and symmetrical faces using a dot-probe task (N = 3 individuals; 2F) and (ii) choice bias for pictures of flanged males over unflanged males using a preference test (N = 6 individuals; 4F). In contrast with our expectations, we found no immediate attentional bias towards either large flanges or symmetrical faces. In addition, individuals did not show a choice bias for stimuli of flanged males. We did find exploratory evidence for a colour bias and energy efficiency trade-offs in the preference task. We discuss our null results and exploratory results in the context of the evolutionary history of Bornean orang-utans, and provide suggestions for a more biocentric approach to the study of orang-utan cognition.

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“…Our knowledge of reproductive success of the two morphs is limited, as siring opportunities are not only rare because of long female inter‐birth intervals of 6–9 years (van Noordwijk et al, 2018), but also scattered in space because of orangutans’ semi‐solitary lifestyle (van Schaik, 1999). Moreover, female orangutans do not advertise the probability of ovulation with any behavioral or morphological signals (Durgavich et al, 2023; Galdikas, 1981; Schultz, 1938) and ovulation is likely concealed from males, as males initiate copulations even when females are highly unlikely to be fertile (Knott et al, 2010; Kunz et al, 2022; Nadler, 1981).…”

Section: Introductionmentioning

confidence: 99%

Alternative reproductive tactics of unflanged and flanged male orangutans revisited

Kunz

Duvot

Ashbury

et al. 2023

American J Primatol

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In many slowly developing mammal species, males reach sexual maturity well before they develop secondary sexual characteristics. Sexually mature male orangutans have exceptionally long periods of developmental arrest. The two male morphs have been associated with behavioral alternative reproductive tactics, but this interpretation is based on cross‐sectional analyses predominantly of Northwest Sumatran populations. Here we present the first longitudinal analyses of behavioral changes of 10 adult males that have been observed in both unflanged and flanged morph. We also analyzed long‐term behavioral data on an additional 143 individually identified males from two study sites, Suaq (Sumatra, Pongo abelii) and Tuanan (Borneo, Pongo pygmaeus wurmbii), to assess male mating tactics cross‐sectionally in relation to population, male morph (unflanged and flanged), and other socio‐ecological factors. Both our longitudinal and cross‐sectional results confirm and refine previous cross‐sectional accounts of the differences in mating tactics between the unflanged and the flanged male morphs. In the unflanged morph, males exhibit higher sociability, particularly with females, and higher rates of both copulation and sexual coercion than in the flanged morph. Based on our results and those of previous studies showing that females prefer flanged males, and that flanged males have higher reproductive success, we conclude that unflanged males face a trade‐off between avoiding male‐male contest competition and gaining mating access to females, and thus follow a “best‐of‐a‐bad‐job” mating strategy.

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Orangutan Sexual Behavior

Cited by 5 publications

References 0 publications

Maternal behavior in Sumatran orangutans (Pongo abelii) is modulated by mother-offspring characteristics and socioecological factors

Maternal behavior in Sumatran orangutans (Pongo abelii) is modulated by mother-offspring characteristics and socioecological factors

No immediate attentional bias towards or choice bias for male secondary sexual characteristics in Bornean orang-utans (Pongo pygmaeus)

Alternative reproductive tactics of unflanged and flanged male orangutans revisited

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