Biologist discusses 100 years of research into animal control hierarchy

University of California Associate Professor Elizabeth Hobson studies animal behavior, including the control hierarchy. She worked with highly social birds such as monk parrots. Credit: Michael Miller

Dominance hierarchies were first described in chickens a century ago by a Norwegian zoologist who coined the term “click order”.

Since then, researchers such as University of Cincinnati biologist Elizabeth Hobson have examined the intricacies of conflict and competition among species as diverse as primates, whales, birds and insects.

Hobson, assistant professor of biology in the University of California College of Arts and Sciences, has contributed to this discussion in several published studies, particularly of birds such as monk parrots. This month, I co-edited a special issue of the magazine Philosophical Transactions of the Royal Society B Dedicated to a century of research into the hierarchy of control.

Hobson also authored a new study in the journal using data mining at Google Scholar to examine trends in the hierarchy of control. There are increasingly more publications on this topic each decade, totaling 26,000 papers published in the past 100 years. The growth in the work published each decade along with the diverse societies studying the subject indicates that the hierarchy of control still captivates researchers for all they know about animal behaviour.

This topic continues to interest both the public and researchers, Hobson said, because as a society we are often preoccupied with conflict and competition.

“Think of our interest in sports and competition,” Hobson said. “Discovering who is the best underlies so much of what we love to watch.”

The Norwegian Thorleif Schjelderup-Ebbe first described the hierarchy of control in his 1921 thesis while studying how domestic chickens create peck orders and understand their place in them. Chickens peck on those of lower standing and in turn peck birds of higher order.

“He is like Charles Darwin in the hierarchy of domination,” Hobson said. “Many cores of insight he had 100 years ago have survived today.”

An introductory essay by Hobson and her fellow editors draws liberally from Schildrup-Epp’s colorful writings to show how his ideas a century ago still resonate today.

He wrote, “Anyone who thinks that chicken yard residents are reckless, happy creatures who live an everyday life full of undisturbed pleasure… is completely wrong.” “Great danger lies in the chicken arena. Entry and excessive attacking can allow you to rise to the top of the hierarchy. But if your only way to retain rank is aggression, the moment you let your guard down, someone else can take on.”

Schildrup-Ebbe would later study and teach sociology and psychology. In 1939, when fascism spread throughout Europe, he said: “Authoritarianism is the basic idea of ​​the world, inextricably linked with all forms of life and existence.”

It can be easy to see a reflection of our lives in the daily struggle of animals. But Hobson said that would be an oversimplification given the broad spectrum of human emotions, our complex motivations, and even our most complex relationships.

“You want to be careful with individual comparisons,” Hobson said. “It’s more of an analogy. What do we see in animals and what can it tell us about how people react?”

However, people are fascinated by the struggle.

Co-editor of the journal issue is Elie Strauss, a postdoctoral researcher at the Max Planck Institute for Animal Behavior. James Curley, assistant professor of psychology at the University of Texas at Austin; and Daisaburo Shizuoka, associate professor of biology at the University of Nebraska at Lincoln.

“Of all the topics in behavioral biology, dominance has to be one of the most familiar to non-scientists, perhaps because power structures are intuitively familiar to us,” said co-editor Strauss.

But contrary to conventional wisdom, dominance often has more to do with circumstances and opportunities than with good genes or size and superior status.

“The idea that the most dominant animals get the most mating opportunities and resources is not entirely wrong, but it’s also oversimplified,” he said.

In some cases, Strauss said, dominant animals face a greater risk of injury from frequent fights to defend their position or territory. As a result, some animals do not maintain their position for long.

Perhaps surprisingly, he said, over time, many individuals are likely to hold a high position at some point in their lives.

Strauss works in Kenya’s Masai Mara, where he studies spotted hyenas, highly social carnivores that are offended by their unfunny portrayal as villains in Disney’s The Lion King. When it comes to the hierarchy of control, the movie misses the mark for how it portrays the titular character as noble and honest.

“The view that dominant animals act as benevolent leaders of their groups is wishful thinking which I believe says more about our view of our societies than our view of the nature of animals’ social lives,” Strauss said. “Individuals of high status use their status to advance their personal interests.”

In the decades since Schgelderup-Ip’s first observations, researchers have learned a great deal about hierarchies of control, including the ways animals signal their superiority over others, the clever ways in which they avoid conflict and how factors such as group size and social alliances affect the system.

“A hierarchy of control in groups is incredibly common,” Hobson said. “But species shape these systems in ways that may look similar but are managed very differently.”

In some animals, sheer size dictates one’s dominance. But more often than not, it’s not that simple, Hobson said.

Some animals indicate their dominance over potential mates, possibly to pre-empt conflict with competitors. Fish such as the African tilapia adopt bright colors when ascending in the mattress, Hobson said. Male monkeys called mandrills also have skin colors that are related to their hormones.

The key to understanding how to manage these different types of control is comparative analysis. Strauss and colleagues created a new database of 135 different species in which dominance data have been published.

“This new package will radically simplify comparative analyzes of dominance,” Hobson said.

Hobson studied how monk parrots battle closer competitors to consolidate their positions rather than waste effort fighting lower-ranking members of the colony. This strategy may reflect a high level of awareness.

“In the parrots I work with, we don’t find a strong association between size and dominance. Instead, individuals may need to learn about their competitors and remember past fights and outcomes to come up with a mental model of rank,” she said. “This is a completely different cognitive task than choosing to fight an opponent just because he’s a little younger than you.”

Then there is the politics. Some animals such as baboons and hyenas form alliances to maintain status.

“Going in and being aggressive can allow you to rise to the top of the hierarchy,” Hobson said. “But if your only way to retain rank is to be aggressive, the moment you let your guard down, someone else can take over.”

This year, Hobson’s group will begin studying a new species in her lab: the northern partridge quail. Led by University of California graduate student Sanjay Brasher, these new experiments will focus on how hierarchies of dominance and the role of memory are formed.

Hobson said she and her group are excited to pursue new questions in the field of hierarchy of control.

“The more you know, the more you realize everything you don’t know,” Hobson said. “Will there be fertile ground for another hundred years of research on this topic? Certainly.”

Animal aggression depends on their rank within the social hierarchy

more information:
Elizabeth A. Hobson, Defining the Dynamics of Nearly 100 Years of Dominance Hierarchy Research, Philosophical Transactions of the Royal Society B: Biological Sciences (2022). DOI: 10.1098 / rstb.2020.0433

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