Being a ladies' man comes at a price for alpha male baboons
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An alpha male baboon keeps close tabs on a fertile female in the Amboseli basin of southern Kenya.
view moreCredit: Photo credit: Susan Alberts, Duke University
DURHAM, N.C. -- A few things come to mind when we imagine the “alpha male” type. They’re the ones calling the shots, who get all the girls. But there’s a downside to being a strong and powerful alpha stud -- at least if you’re a baboon.
Studies show that despite their high rank, the No. 1 males in baboon society are also some of the most stressed out, as measured by their high levels of glucocorticoids, the hormones involved in the ‘fight-or-flight’ response.
But the leaders’ stress burden comes from a surprising source. New research reveals it’s not the time they spend fighting with other males that raises their stress hormone levels. Instead, it’s the effort they put into their mates.
That’s according to a new study of wild baboons in Kenya led by Duke University professor Susan Alberts with Catherine Markham at Stony Brook University, as well as senior research scientist Laurence Gesquiere of Duke.
As anyone who has climbed the career ladder knows, leaders can face many sources of stress. Office politics. Tough decisions. The constant pressure to perform.
Alpha male baboons may not have deadlines to meet, but it doesn’t mean their lives are stress-free, the researchers said.
To reach the top spot and stay there, male baboons must rely on their strength and battle skills to jockey for position and earn their place.
The dominant male in a group also jealously guards his right to mate, closely monitoring females during their fertile periods and following them around for days at a time to make sure he is the one who fathers any offspring.
Since 1971, researchers have monitored individual wild baboons in southern Kenya on a near-daily basis, keeping careful track of their social interactions and other behavior over their lifetimes as part of the Amboseli Baboon Research Project.
One of the first hints that the top spot can pose distinct challenges for males came from a study Gesquiere and colleagues published in 2011, which revealed a striking pattern:
Compared with non-leaders, alpha males had significantly higher levels of glucocorticoids.
When stress kicks in, the brain releases these and other hormones that mobilize energy to help the body cope with challenging situations.
In humans, “this response is activated for every kind of challenge we face, whether it's running down the block because you're late for a meeting, running a marathon, or going into a stressful meeting with your boss,” Alberts said.
But what exactly was fueling the baboons’ stress response was unclear.
In the new study, published Jan. 22 in the journal Proceedings of the Royal Society B, the researchers combined 14 years of behavioral records for 204 male baboons with data about their stress hormones, measured from droppings the animals left behind.
The results show, once again, that life is tough at the top. Glucocorticoid levels were 6% higher for alpha males than the rest of the ranks.
But the researchers also discovered a new clue -- top-ranking males also had lower levels of a thyroid hormone called T3, indicating they are burning more calories than they’re taking in.
“Being alpha really has energy consequences,” Gesquiere said.
The new study suggests it’s not the alpha male’s aggressive behavior -- the time he spends fighting and letting everyone know he’s the boss -- that’s taxing his energy reserves.
No matter how often the alpha males threatened, bullied, or pushed around other males, neither their stress hormones nor their thyroid hormones were affected.
“That was a big surprise,” Gesquiere said.
It may be that their flare-ups with other males are too subtle or short-lived to get to them, Alberts explained.
Or that once they get to the top, alpha males no longer need to be overtly aggressive to prove themselves. The alpha can scare other males away with merely a raised eyebrow or a flash of his fangs.
Instead, the researchers found the number one energy drain and source of stress for alpha male baboons was, you guessed it, their mates.
Both their stress hormones and their thyroid hormones -- indicators of their energy demands -- directly correlated with the time they spent monopolizing fertile females.
“They’re essentially staking a claim; preventing other males from gaining access,” Alberts said.
Studies show all this attentiveness fragments their time and attention; making it harder to focus on finding their next meal.
“They're constantly interrupted,” Alberts said. They’ll start to dig up or pry open a tasty morsel, “but then the female gets up and walks away, and they have to abandon it.”
Over time, the demands of being a top-ranking male may be harmful to their health.
Previous studies of Amboseli baboons have found that top-ranking males age faster -- as measured by chemical changes to their DNA -- and live shorter lives than those with lower social standing.
Human hierarchies are more complicated, and so the implications for humans are less clear, Gesquiere said.
We belong to multiple communities throughout our lives, each with its own social dynamics. Someone who’s a peon in the office may be a top player on the pickleball court, for example.
But for dominant male baboons, “stress definitely has long-term consequences,” Gesquiere said.
This research was supported by grants from the National Science Foundation (IOS-1926060 and IOS-1926040) and the National Institutes of Health (NIA R01AG053308, R01AG071684, R01AG075914, and R61AG078470)
CITATION: "Energetic Costs of Social Dominance in Wild Male Baboons," Laurence R. Gesquiere, Christine Adjangba, Georgia Young, Clara Brandon, Sophie Parker, Emily E. Jefferson, Tim L. Wango, Vivian K. Oudu, Raphael S. Mututua, J. Kinyua Warutere, I. Long’ida Siodi, A. Catherine Markham, Elizabeth A. Archie, Susan C. Alberts. Proceedings of the Royal Society B, Jan. 22. DOI: 10.1098/rspb.2024.1790
Method of Research
Observational study
Subject of Research
Animals
Article Title
Energetic Costs of Social Dominance in Wild Male Baboons
Article Publication Date
22-Jan-2025
Stronger stress response in monkeys helps them survive
A recent El Niño drought paved the way for the new discovery
Key takeaways
- The team used the environmental circumstances and fecal samples collected from the six years prior to the El Niño drought to study the relationship between the endocrinologic stress response and survival in the white-faced capuchins.
- Monkeys who showed a steeper rise in these stress hormones during the mild droughts were more likely to survive the severe El Niño drought.
- As weather intensifies globally, longitudinal studies of how wild animals cope with changes in temperature, rainfall and food availability can help us understand which species can adapt rapidly.
White-faced capuchin monkeys in Costa Rica who experienced more intense physiological responses to mild droughts were more fit to survive extreme drought, researchers found in a new UCLA-led study.
Most research on wild animals and humans is focused on the damage that stress response causes to a system — “the wear-and-tear.” In this new study, however, published in the journal of Science Advances, a team of researchers sought to examine the adaptive nature of the stress response in wild primates and how a more robust stress response might help them when faced with catastrophic events.
“We wanted to understand how the stress response adaptively helps these individuals survive greater challenges,” Susan Perry, a UCLA evolutionary anthropologist, field primatologist and co-author of the study, said.
In the absence of an experimental design that could apply the same stressor to all individuals in a population, the researchers took advantage of a natural experiment — a particularly severe El Niño drought — to investigate the relationship between hormonal responses to this extreme stressor and survival outcomes of white-faced capuchins at the Lomas Barbudal Capuchin Monkey Project in Guanacaste, Costa Rica.
In Guanacaste, Perry and a team of researchers have been documenting the lives of monkeys and studying their social behaviors and survival strategies for 35 years. For this particular study, Perry’s research group (including current and former graduate students, and research assistants Irene Godoy, Ashley Mensing, Juliane Damm and Colleen Gault) collaborated with University of Michigan researchers Jacinta Beehner and Sofia Carrera.
How a drought led to discovery
The El Niño drought that spread across Central and South America from 2014 to 2016 was the biggest in recent history and led to the deaths of many monkeys. While devastating for the monkeys and the researchers who have studied them for so long, Perry’s team was able to make use of the environmental circumstances and samples collected from the six years prior to study the relationship between the endocrinologic stress response and survival in the white-faced capuchins.
During the drought, the monkeys started to lose weight, revealing vertebrae and rib cages, and mothers even rejected caring for and nursing their infants, abandoning them to go forage. Monkeys who would normally babysit infants in a mother’s absence also were not taking on child care responsibilities. Mortality rates soared, particularly for infants and older females. This was the only time in Perry’s long-term study that these monkeys, who are usually behaviorally flexible, failed to adapt to an environmental stressor by simply changing how they behaved (e.g., changing their diet).
For 14 female monkeys who survived and 14 who had died, the researchers analyzed glucocorticoid levels in fecal material that had been collected from them in the six years prior to the El Niño drought (2008-2013). Glucocorticoids are steroid hormones that regulate metabolism, inflammation and the immune system.
What glucocorticoids in monkey fecal matter revealed
The researchers discovered that the monkeys who showed a steeper rise in these stress hormones during the mild droughts were more likely to survive the severe El Niño drought than those monkeys who experienced less of a stress response. The findings controlled for other conditions known to affect these hormone levels, such as pregnancy and time of day.
With a clearer picture of what an adaptive stress response looks like for this species and population, Perry’s team can begin to ask questions about the origin and maintenance of individual differences in the endocrine stress response and whether these differences affect survival.
The study also puts a spotlight on the value of long-term studies in the face of climate change. As weather intensifies globally, longitudinal studies of how wild animals cope with changes in temperature, rainfall and food availability can help us understand which species can adapt rapidly through learning or physiological flexibility and which species lack the ability to cope with major environmental changes during their lifetimes. This knowledge can be useful for conservation reasons. For example, a population of highly endangered animals that cannot quickly adapt to change might need to be moved to a place that now has climatic conditions that match the environment in which that population evolved.
Journal
Science Advances
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