Marmot cries give insights to human personalities
June 19, 2010
SUMMIT COUNTY, Colorado – Among all of Summit County’s wildlife, the yellow-bellied marmot may be the noisiest. Anyone who has hiked through their high-alpine habitat has likely heard the marmots’ chorus of chirps and whistles as they alert each other to the presence of a potential predator.
While all that vocalization may not seem terribly complicated to the human ear, each chirp contains a wealth of information about the caller for other marmots.
Dr. Dan Blumstein, a biologist from UCLA, has devoted much of his professional life to studying the calls of Colorado’s marmots. Through his work, he has been able to decode the rodents’ alarm calls to determine the age and sex of the caller. He has even been able to uncover what an individual marmot’s alarm call says about its “personality.”
At the simplest level, a marmot’s response to an alarm call involves looking up and fleeing. But each alarm call communicates not only the presence of a potential threat, but also the level of the threat. A high-risk call from a given marmot tells others to “drop everything,” Blumstein said. A low-risk call communicates, “Maybe look around, and figure out what’s going on.”
Interestingly, Blumstein has found that marmots do not assess risk uniformly. Just as with humans, there are laid-back individuals as well as nervous worry warts. And marmots learn to identify who’s who, learn their alarm call and react accordingly.
“This species seems to not trust unreliable individuals,” Blumstein said. “Marmots spend more time looking around when they hear from those unreliable individuals.”
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These observations afford insights into behavioral diversity within species beyond the marmot. The research gets at the question of why we have personalities: Why are there bold people? Why are there shy people? What is the survival advantage of having different individuals behave differently in a given situation or environment?
“We’re using marmots to understand why personality differences can be maintained in populations,” Blumstein said.
Having a diversity of behavior among individuals can better position a species to adapt to changes in its environment. For example, a marmot population may not be well served by a high proportion of nervous nellies when a predator population is low. But when the predator rebounds, it could be good to have all those more vigilant individuals around.
“In some areas, animals will behave a certain way, and in another way in other areas. People behave differently in big cities than in the country. There are benefits and costs to behaving different ways – doing one thing in one time and another thing in another time,” Blumstein said.
Blumstein has taken this line of thinking into the movie theater, of all places. Fearful vocalizations are very similar across species. From a marmot pup to a dog to a human, horrible screams accompany fear. The acoustic structure of those screams are very chaotic, nonlinear and unpredictable.
“I elaborated a hypothesis that scary films should use nonlinearity to evoke those fear responses,” Blumstein said.
Sure enough, it turns out that horror films feature such nonlinear, chaotic sounds not only in human screams, but also in sound effects and sound tracks.
“It seems that our response is a very common mammalian trait when we get scared,” Blumstein said.