News

Jenny Tung wins the MacArthur 'Genius' Grant

Author: David Jansen

Jenny Tung wins the MacArthur 'Genius' Grant

Tung, an associate professor in evolutionary anthropology, studies primates and has demonstrated links between social stress and immune system function in macaques. She is one of 26 winners of the prestigious Genius Grant in 2019, and the $625,000 will be paid over quarterly installments for the next five years. Read More

Conditional fetal and infant killing by male baboons

Author: Matthew Zipple

In a recent article published in the Proceedings of the Royal Society B, we showed that both feticide and infanticide occur in Amboseli following the immigration of especially aggressive malesa behavior that is more common during periods of limited reproductive opportunities and low resources. This represents the first population-wide analysis of feticide in a wild population. Read More

Lifespan equality in humans and other primates

Author: Susan Alberts

Public interest in social and economic equality is burgeoning. In a recent paper in PNAS that examines both nonhuman primates and humans, we measured a related phenomenon, lifespan equality – a measure of whether lifespans in a population tend to vary a lot or be similar to each other. We used data from six well-studied primate populations – our own Amboseli baboon population, and also mountain gorillas in Rwanda, chimpanzees in Gombe Stream National Park in Tanzania, sifaka in Beza Mahafaly in Madagascar, muriqui monkeys in the RPPN Feliciano Miguel Abdala in Brazil, and capuchin monkeys in Santa Rosa National Park, Costa Rica. Read More

The Challenge of Survival for Wild Infant Baboons

Author: Susan Alberts

Surviving infancy is challenging for wild primates, as decades of research on species ranging from lemurs to gorillas have revealed. For an infant baboon, surviving the first year of life requires learning to identify and successfully consume more than 250 types of food, avoiding fatal disease and predation, and perhaps most importantly identifying and avoiding dangers from other baboons both inside and outside their social group. In Amboseli, first-year mortality has averaged about 30 percent over the four decades of our study, but has climbed as high as 50 percent during difficult times. Just getting through infancy represents a huge piece of the Darwinian gauntlet that every animal must run.

We have published a popular article in American Scientist magazine, in which we relate stories about Amboseli infants who did and did not make it through that Darwinian gauntlet. Read More

Early adversity predicts life span

Author: Susan Alberts

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In humans and other animals, harsh circumstances in early life are linked to poor health and high mortality rates in adulthood. It is thought that these effects are greatest when multiple adverse conditions occur at the same, but this hypothesis has rarely been tested. We used prospective data on 196 wild female baboons in Amboseli to show that the number of adverse circumstances that a female experiences during her juvenile years predicts how long she lives as an adult. Specifically, we examined the effects of six different adverse circumstances: (i) being born in a drought, (ii) having a low ranking mother, (iii) having a socially isolated mother, (iv) having your mother die before you reach 4 years of age (the approximate age at sexual maturity for females), (v) having a younger sibling born when you yourself are still quite young (1.5 years of age or less), and (vi) living a very large social group. Females who experience 3 or more of these adverse circumstances tend to die 10 years earlier than females who experience no adverse circumstances. For comparison, the average female, once she reaches adulthood, lives to about 18.5 years of age, so 10 years is a very large difference in the life of a female baboon.
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Group Living: For Baboons Intermediate Size is Optimal

Author: Catherine Markham

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What are the costs and benefits for animals living in groups of different sizes? Balancing the trade-offs between within-group competition (which favors smaller groups) and between-group competition (which favors larger groups) suggests that intermediate sized groups may be best, yet empirical support for this prediction has largely been lacking.  Using long-term data on wild baboons, we provide novel evidence that individuals living in intermediate-sized groups have energetically optimal space-use strategies and lower glucocorticoid (stress hormone) concentrations than individuals in either large or small groups.  Our results offer new insight into the costs and benefits of group living. Read More

Self-organizing dominance hierarchies in a wild primate population

Author: Susan Alberts

Many social animals form linear dominance hierarchies, with a clear rank order among group members. Such hierarchies can profoundly influence health and access to resources, but the mechanisms underlying hierarchy formation and maintenance remain unclear. Do individual dominance ranks simply emerge from individual attributes – such as fighting ability? Or are linear hierarchies the product of social self-organization processes such as winner and loser effects – i.e. the phenomenon in which winners become more likely to win in subsequent encounters, and losers become more likely to lose? Here, we present the first evidence for social self-organization processes in a wild animal population.  Read More