Monday, October 25

The brutal murder of an albino calf shows the stark reality of chimpanzee infanticides | Science


On July 15, 2018, an unusual observation took place in the Ugandan forests of Budongo: for the first time a team of scientists saw an albino chimpanzee in the wild, among its congeners. Soon, a 19-year-old female, emerged from the undergrowth carrying her little albino baby, to everyone’s surprise; humans and chimpanzees. And the outcome was terrible. Four days after that first observation, the primatologists witnessed the brutal murder of the little boy, who was barely two or three weeks old.

‘Lucy’, the sterile chimpanzee who plays at being a mother with corpses

The chief chimpanzee who cradled the baby instead of killing her

But before drawing parallels with the racism of other great apes such as humans, explaining this death solely by the color of their fur, it is worth knowing more about the Sonso community. A group of chimpanzees of about 75 members subjected to great ecological pressure and in which there is the highest rate of infanticides ever recorded in this species. “It is the worst place where he could have been born,” sums up Adriana Lowe, a specialist in this phenomenon.

Before the interpretations, the facts, that narrate with great detail in the American Journal of Primatology by Budongo primatologists. That first meeting was already very traumatic: the other chimpanzees received Soon with screams and gestures similar to those they make when encountering potentially dangerous animals such as snakes, wild pigs or unknown humans. Certainly something was wrong. The tension was mounting, with the male Frank charging at the mother, whom he tried to bite. But after the skirmishes, everything calmed down when the male Kwenzi approached Soon and he held out his hand to calm her down. “It would not surprise me at all if they recognized that this individual was different. And they can get a little nervous about new things in general, so it seems logical that they would be surprised with a very unusual-looking baby, ”says Lowe, who does not sign this study, although he has studied Sonso’s infanticides in depth.

“Not all albino primates are killed by their species”

Frans de Waal, primatólogo

The scientists did not see the little albino again until four days later, when they unleashed their violence against the little boy. What follows is an unsettling scene, but totally common among Sonso’s chimps. On July 19, 2018, at 7.30 in the morning, the primatologists began to hear screams of a serious confrontation. “Judging by the sounds, the assault involved repeated physical contact. The cries of an infant were also heard, ”the study explains. Suddenly appeared before his eyes Eve, the alpha male, holding the albino calf, already missing a forearm, against his body. He caught him by the leg with his mouth and climbed to the top of the trees, where he began to bite him all over his body until another female, Melissa, gave him the lethal bites on the head.

Once dead, a striking ritual began in which up to ten of the chimpanzees present came to inspect the small white-haired, two-kilogram corpse. The first was Frank, the one who attacked his mother a few days earlier, a male who has already perpetrated at least four infanticides, according to Budongo’s records. He smelled it repeatedly and scrutinized his genital area, even inserting a finger into his anus, a behavior that had only been recorded once before: when an alpha female inspected the corpse of a former chieftain who was beaten to death by her group in Senegal, more than 5,000 kilometers away.

“It is impossible to say if this infanticide was due to the baby having albinism because it occurred during a period with a high murder rate.”

Adriana Lowe, University of Kent

This careful and repeated examination of the corpse by hatchlings and adults does not seem like typical behavior, explains by email Maël Leroux, witness to the events and main author of the study. A male used his lips to test the white fur of the young and several individuals stroked it, clearly interested in the texture of that fur, which they have only seen in small monkeys that sometimes hunt in the area. “In previous observations, fewer subjects inspected the corpse, for less time, often only the mother,” adds Leroux, from the University of Zurich.

Obviously, the chimps noticed that something strange was happening with the little albino, but did they kill him for it, for fear of the unknown? It is a good idea to delve into the Sonso community to better understand the context. Infanticide is the most common cause of infant death there; two-thirds of the young that die do so at the hands of other chimpanzees. Of the 103 births registered in Sonso, at least 24 were victims of infanticide, one in four, and 40 attacks against babies were recorded in just 25 years, according to a study published by Lowe two years ago. Before seeing the color of its fur, the little albino already had a 25% chance of dying violently. Another fact: his mother Soon, immigrant in Sonso, they had killed their first calf just a year before, in July 2017. Next to the corpse of that newborn they found Eve, the alpha who dismembered the albino.

Of the 103 births recorded in Sonso, at least 24 were victims of infanticide. Before seeing the color of his fur, he had a 25% chance of dying violently

Consulted by EL PAÍS, the famous primatologist Frans de Waal admits that “it is difficult to know what happened”. “On the one hand, the description suggests that many chimpanzees were alarmed or feared by this strange-looking calf. On the other hand, it is known that these chimpanzees have carried out many infanticides, what happened to this baby may not be so unusual ”, sums up the scientist, author of numerous books on the behavior of great apes. And he highlights: “Not all albino primates are killed by their species”, pointing as an example the case of the spider monkeys. In addition, there is the case of Pinky, an albino chimpanzee who was recovered from the jungle and who, although the circumstances of his case are unclear, was well accepted by the other chimpanzees of the sanctuary in which she was welcomed.

For Lowe, “it is impossible to say if this infanticide was due to the infant having albinism” because Sonso is a more infanticidal community and “this occurred during a period with a high murder rate.” “It is entirely possible that the baby had been killed anyway and albinism was not a factor in his death. It is a pity that this unique case did not occur in another community, because Sonso is the worst place where he could have been born ”, laments the primatologist from the University of Kent. Leroux warns that care must be taken when interpreting the case, but points out that “there are similarities between the infanticide of the individual with albinism and others observed.”

Violence as a reproductive strategy

John Mitani, a specialist in chimpanzee violence, considers that “it is difficult to assess whether chimpanzees thought it was the same or different from them.” “Infanticide occurs quite frequently in this group, so this is nothing out of the ordinary,” says Mitani of the University of Michigan, who was also not involved in this study. For this primatologist, it would have been good to see how the chimpanzees reacted to the baby several times, to understand if they saw him as an equal or as something different. “From my own experience observing chimpanzees for almost 30 years, it is rare for a mother to lose two successive infants to infanticide. In this sense, it is not yet another infanticide. And what makes things suspicious, of course, is that the infant was an albino, ”says Mitani.

Females disappear away for a time after giving birth to avoid having their newborn killed, but at Sonso they don’t have that option.

To understand the death of the albino calf, therefore, one must also understand why chimpanzees kill newborns and why there are so many infanticides in Sonso. Lowe, who has documented this phenomenon in detail, described in a previous study how females disappear away from the group for a long period of time after giving birth to avoid having their newborn killed: it is what experts call maternity permission. But in Sonso the territory is scarce and the females do not have the option of taking that permit. Females are able to detect which males will be most dangerous to their offspring: those who rise rapidly through the social ranks, because they are in a hurry to ensure their reproductive success. And in Sonso there is a permanent instability that causes too much movement in the hierarchy.

Males kill the offspring of others so that females are available to sire their own. This is a basic characteristic of chimpanzee sexuality, which is based on a violent patriarchy: males attack females to ensure that they only copulate with them because that violent coercion guarantees them offspring. Bonobos, our other close cousins, have a completely different approach: males don’t know when the female is ovulating, so they all try to maximize their chances. They copulate as much as they can and do not use violence against them, since they live in a matriarchy in which the females defend themselves by fighting together against aggression.

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