Browsing by Subject "Reproductive strategy"

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    Male reproductive strategies in bonobos (Pan paniscus) and chimpanzees (Pan troglodytes)
    (2023-05) Mouginot, Maud
    Bonobos are often portrayed as peaceful while chimpanzees are described as aggressive. This contrast has greatly influenced efforts to explain the evolution of war and peace in human societies. However, studies reported that males have higher reproductive skew — the stage in which some males obtain a disproportionate share of paternities — in bonobos than chimpanzees. Because reproductive skew is usually associated with intense contest competition among males for mates, how male bonobos manage to achieve such high reproductive skew despite having what seemed to be less aggressive relations with other males is intriguing. Nevertheless, while researchers have conducted extensive studies in male reproductive strategies in chimpanzees, less is known about bonobos, and how they compare to chimpanzees. Because the current literature does not provide a direct comparison of rates of aggression with similar sampling methods, we still do not know the extent to which these rates differ between these two species. One study directly compared reproductive skew in bonobos and chimpanzees, however, while they included data from five chimpanzee communities, they had data from only one bonobo community. Thus, we need more data to better understand patterns of reproductive skew within bonobos and between bonobos and chimpanzees. Finally, reproductive success can also depend on non-aggressive reproductive strategies. Male-immature interactions have been observed in promiscuous species, such as female-bonded cercopithecoid monkeys (such as rhesus macaques and olive baboons) and chimpanzees. Few studies reported male-immature interactions in bonobos, and none explored how those interactions might affect male reproductive success. In my dissertation, I aimed to fill those gaps by first directly comparing bonobos from the Kokolopori Bonobo Reserve, Democratic Republic of Congo, and chimpanzees from Gombe National Park, Tanzania, conducting generalized linear mixed models (GLMM) within an information theoretic model selection approaches. I found that despite the popular image of bonobos as being more peaceful than chimpanzees, while male chimpanzees had a higher rate of male to female aggression, male bonobos received higher rates of female aggression and, surprisingly, exhibited higher rates of aggression among males than chimpanzees. Moreover, I found that the best predictor of male bonobo copulation rate was the rate of aggression towards females, even though such aggression occurred infrequently (16 interactions out of 2,047 hours of observation). I then re-examined skew patterns using paternity data from published work and new data from Kokolopori and Gombe and reviewed the different mechanisms underlying patterns of reproductive skew. Using the multinomial index (M), I found considerable overlap in skew between the species, but the highest skew occurred among bonobos. My detailed comparison of data from Pan highlights that reproductive skew models should consider male-male dynamics including the effect of between-group competition on incentives for reproductive concessions, but also female grouping patterns and factors related to male-female dynamics including the expression of female choice. Finally, comparing male-immature interactions in bonobos at Kokolopori and chimpanzees at Gombe, I found that male bonobos play more with immatures than male chimpanzees, but I did not find any consistent difference in grooming duration among males and immatures between the two species of Pan. I did not find strong evidence that male bonobos interact with immatures as a mating or paternal effort. However, I found that males were more inclined to copulate with their closer associates and to play and groom with their close associates’ offspring.