In August, a mountain lion was seen prowling the suburb of New Canaan, Connecticut several times, and not for the first time. Ten years ago, a young mountain lion traveled to Connecticut, prowling more than 1,500 miles from South Dakota’s Black Hills, before being killed while crossing a highway.
What stands out from these incidents for Malcolm L. Hunter, Jr., professor emeritus of wildlife ecology at the University of Maine, are the exploratory personalities of the big cats.
“You can be sure that the young mountain lion who left South Dakota and ended up being run over by a car in Connecticut, was not a homebody and shy,” he said.
Wildlife biologists have traditionally studied factors such as prey abundance, habitat quality, and behavior to assess the roles animals play in particular ecosystems. But a growing number of scientists say there’s one critical element missing: the range of personality traits in individual animals, whether grizzly bears, squirrels or earthworms. Some scientists claim that even bacteria are unique.
“Personality is found in all taxa,” said Alessio Mortelliti, a rodent personality expert at the University of Maine and recipient of a National Science Foundation Career Fellowship.
The five common animal personality traits are boldness, aggression, activity, exploratory tendency and sociability. To qualify, these traits must be present “over time and in all contexts.”
Wild animals “are not just little duplicating automatons doing what they do; they do them in different ways,” said Dr Hunter, co-author of a paper that urged scientists to bring such studies into the field of ecology. “It is important to know and appreciate that personality can be taken into account in the management of these systems. »
It’s not unlike a litter of puppies or a box of kittens, where each animal is different. In nature, however, these personalities affect natural processes.
Dr. Hunter noted in his article that Charles Darwin, in his last book, “The Formation of Vegetable Mold by the Action of Worms”, published in 1881, referred to earthworms, in various ways, astimid, clean and tidy, and neglected. A 2018 study found earthworms to be very different in their problem-solving abilities.
A personality trait “that runs through many species is the extent to which some individuals are more curious, more exploratory, more willing to go out of their way,” Dr Hunter said. “Well, I guess an earthworm doesn’t really have a neck,” he laughed.
Understanding animal personalities paints a more complete picture of the natural world, some experts say, and digs into individual differences far deeper than behavioral ecology. It plays a role in all aspects of their lives, from mating to forest regeneration.
Dr. Michael Goldstein, a psychology professor at Cornell University who studies the social significance of babbling in birds and human babies, placed 48 zebra finches in a cage to see how different personality types find a mate and how that affects parenthood. “It turns out that they pair by exploration,” he said. “Low-crawling males and low-crawling females came together, and high-crawling males and high-crawling females came together.”
Although the idea that earthworms or bacteria have personalities might seem like a stretch, it is clear that more complex animals, including wolves, bears, dolphins, whales, and many birds, have very different personalities. developed that reflect human traits.
Take the case of the famous grizzly Giefer, with a predilection for breaking and entering. For several years in the 1980s, the big bear, weighing more than 500 pounds, smashed windows or doors of unoccupied summer cabins along the North Fork of the Flathead River near Glacier National Park in Montana , and helped herself to flour, sugar or whatever food was left behind. The bear ransacked about twenty cabins.
“This bear was incredibly delicate,” said Chris Servheen, a retired American biologist who attempted to capture the bear. “He didn’t want to fall into traps and we never saw him. He was like a ghost. We tried everything we could to catch this bear, and it was impossible to catch.
The grizzly Giefer was eventually killed by a hunter in British Columbia.
In wolves, pack cohesion is highly dependent on the alpha female. A strong leader in these matriarchal societies will nab and discipline roaming wolves, but less aggressive leaders will not. And when an alpha female dies, the pack can often disintegrate.
Personalities play a key role in ecosystem dynamics, and eliminating one type of individual can affect evolution, scientists say. A bold grizzly or cougar could help a population adapt to new terrain and circumstances – a trait that could be particularly important as climate change forces some species to light up for more suitable living conditions.
Animal personalities can also have profound effects on ecology.
Rodents play a key role in forest regeneration, for example, a subject Dr. Mortelliti is studying in voles, mice and squirrels in the Penobscot Experimental Forest in Maine. If a mouse crawling on the floor of a forest comes across a seed, its personality can cause it to engulf the seed immediately, meaning it will not germinate into a plant. If the mouse buries the seed, it could create a new plant. Bolder animals scatter seeds farther than timid individuals, for example. But a bold animal is also more likely to end up in the clutches of a hawk or owl.
Rodent personalities are determined by various tests, which are animal versions of the Rorschach. In one test, a mouse is placed in a large box. Shyness can be indicated by a mouse’s tendency to spend time near corners or walls, while boldness can be shown by those moving towards the center. The mouse is placed in a small bag to measure the stress response or studied in the open field for its response to novelty.
Captured animals are marked with a microchip and an ear tag and released. They are offered seeds, and when they pass an antenna, it reads the chip “so we know exactly who got the seeds and what they did with them,” he said. More than 3,200 rodents had their personality assessed for these studies.
The way a forest is managed can alter the balance ratio of personality types.
“With unmanaged forests or as natural a forest as possible, you have a really nice split of the bold and the timid,” Dr. Mortelliti said.
As plants shift their range to keep pace with a changed climate, mice and squirrels will come into contact with strange-looking new seeds, and they will be needed to disperse them, a key ecosystem service.
“How bold an individual is will have effects on whether or not they interact with that seed,” Dr. Mortelliti said. “This could affect the likelihood that a plant can adapt to climate change.”
Altering landscapes in certain ways favors certain personality types, altering the course of evolution. And it could affect the ability of forests and other ecosystems to adapt to a changing world. What is essential, he said, is a diversity of personalities in a landscape.
“Natural selection has favored this variation in personalities because in some cases, in some years, and in some contexts, it’s more beneficial to have different personality types,” he said. “The higher the diversity, the better the populations are able to adapt to change.”
Aggression plays a role in ecosystems by determining territory among species. To measure levels of aggression, an animal is placed in front of a mirror to see how it reacts to what it thinks is a rival. The winner of the most aggressive rodent contest?
“The American red squirrel,” said Dr Mortelliti, who has administered personality tests to rodents around the world. “They’re amazing. They’re the only species where you can measure them, you release them and then they climb up a tree and come back to you and yell at you. They really are fiery, territorial individuals.
Research on the ecological role of animal personalities still has some way to go, Dr. Mortelliti said, before specific forest management recommendations can be made.
Iain Couzin is a researcher at the Max Planck Institute for Animal Behavior at the University of Konstanz in Germany who studies swarm intelligence – how fish come together to form a school or birds soar and dive in unison in the whispers. He thinks the notion of animal personalities is exaggerated.
Biologists “are all aware of individual differences” in animals, he said. “Darwin was well aware of individual differences. But I don’t like the term personality. The whole process is quite prone to anthropomorphization.
Dr. Mortelliti sees it as a useful prism for visualizing animal behavior. “At the end of the day, we all understand that we measure individual differences in behavior,” he said. “I have no problem using the term personality because it’s intuitive and makes people relate to it.”