There’s a wonderful cartoon by Gary Larson where a penguin, standing amid a throng of virtually identical birds, sings, “I gotta be me! Oh, I just gotta be me…” As ever, Larson’s The Far Side captures the humorous side of a real natural dilemma. Social animals spend time in large groups, but they still have to tell the difference between individuals so they can recognise mates, young, leaders and rivals. As the groups get larger, so does the scope of this challenge, and some species meet it by evolving individuality. As groups get bigger, their members become more distinctive.
Kimberly Pollard and Daniel Blumstein from the University of California, Los Angeles studied different species of ground squirrels, each with a different social structure. They range from the black-tailed prairie dog or yellow-bellied marmot, which live in groups of around six individuals, to Belding’s ground squirrel, which lives in groups of ten or more.
Pollard and Blumstein found that the more sociable a squirrel is, the more distinctive their individual alarm calls. They recorded thousands of alarm calls from eight different species and for each one, they calculated “Beecher’s information statistic”. It’s a number that measures individuality, by looking at how much certainty a call provides about the identity of the caller. And as the squirrel groups got larger, so did this number. An animal like Belding’s ground squirrel has more “signature features” in its alarm calls than a black-tailed prairie dog.
In fact, group size was the biggest driving force behind individuality, explaining 88% of the variation in this important trait. Put another way: if you knew the size of a squirrel’s community was, you could make a fairly accurate stab at how unique its members’ calls were. As Pollard and Blumstein write, “The bigger the crowd, the more it takes to stand out.”
Michael Beecher (of Beecher’s information statistic fame) first proposed the idea that sociable species should be more individual in their messages back in 1982. Since then, several studies have supported his idea. Slender-billed gulls, whose nestlings gather in large communal crèches, have more personally distinctive calls than black-headed gulls, whose chicks stay in the nest. Carolina chickadees make more complex calls if they live in larger groups. And the calls of bat species get more complex as their colonies get larger.
Pollard and Blumstein think that the relationship is widespread but not universal. It will probably hold in other strongly sociable animals like dolphins, carnivores, or primates. It’s less likely to apply to groups that are more fluid or impersonal, such as fish schools or insect swarms. These congregations come together for sheer numbers; the ability to discern individuals isn’t very important. Likewise, for ants, bees or termites, it’s more important to recognise members of the same group rather than specific individuals.
Reference: Pollard & Blumstein. 2011. Social Group Size Predicts the Evolution of Individuality. Current Biology citation tbc.
More on squirrels
- Squirrels masturbate to avoid sexually transmitted infections
- Ground squirrels use infrared signals to fool heat-seeking rattlesnakes
- I Spy With My Little Eye… [Last Updated On: November 7th, 2009] [Originally Added On: November 7th, 2009]
- A Crack Opens in the Ethiopian Landscape, Preparing the Way for a New Sea | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Politics of Addiction | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Finally! An iPhone App That Lets You Track Your Bathroom Habits | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Don’t Pack Your Bags Yet—New Planet-Finder Hobbled by Electronic Glitch | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- In Controversial Scent Lineups, a Dog’s Nose Picks Out the Perp | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Are You a Cognitive Miser? | Cosmic Variance [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Secret Lives and Loves of Great White Sharks | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Britain’s New Protected Minority: Tree-Huggers | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Inspired by Maple Seeds, a Robotic Whirligig Takes To The Skies | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- New Statesman on Accommodationism | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Laser-Powered Robot Climbs to Victory in the Space-Elevator Contest | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Checking Back In With SEAPLEX | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Podcast: An Embarrassment of Genomes | The Loom [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- A Baby Neutron Star, Swaddled in a Carbon Atmosphere | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Butterfliiiies… iiinnnn… SPPPAAAAACCCCEEEEE! | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- My Slate Dialogue with Michael Specter Begins | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Musical, Fahrvergnügen-Inspired Staircase Makes Commuters Less Lazy | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Laser-Etched Fruit Is an Answer in Search of a Problem | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Ares and the carnivals | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Toddler Gets a Telescoping, Prosthetic Arm Bone That Grows With Him | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Neutered HIV Virus Delivers Treatment to Fatally Ill Boys | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Specter’s First Reply: Denialism Kills People | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- LRO sees a Moonslide | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Al Gore’s New Book: A Focus on Solutions | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Universe Has Us in Its Crosshairs | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Makers of Universes | Cosmic Variance [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Can Your Pet Catch & Spread Swine Flu? Yes, If Your Pet’s a Ferret | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Droid 2.0 Vs iPhone | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Tangled Bank News: An Excerpt and More | The Loom [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- LHC Shut Down By Wayward Baguette, Dropped by Bird Saboteur | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Careidolia | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Slate Reply to Specter Up–We Need a National Dialogue on Synthetic Biology | The Intersection [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Pray this doesn’t get passed | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- You Can’t Make This Stuff Up | Cosmic Variance [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Mother Tongue, Indeed: Newborn’s Cries Mimic Mama’s Accent | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Ripped From the Journals: The Biggest Discoveries of the Week | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Alternative Landscapes | The Loom [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Can an iPhone App Decipher Your Baby’s Cries? | Discoblog [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Reminder: Carl Sagan Day | Bad Astronomy [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Are There Pesticides in Your Soup? Dunk a Pollution Dipstick to Find Out. | 80beats [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Log in and Join the Conference [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Conference Ends [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Conference Archive Opens [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Galaxy Zoo [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- .Astronomy 2009 Dates [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- .Astronomy 2009: Programme and venue details [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- .Astronomy Gets Some IYA Love [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- 2009 Posters and Imagery [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- 2009 Sponsors [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- When in Holland… [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The WHAT Cloud? [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- The Jewel Box [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Happy Halloween! [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Ares 1-X Launch [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Confessions of an Alien Hunter [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- LRO Spies Apollo 17 Site [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Mercury in Color [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Hubble and M83 [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Cassini Flyby of Enceladus [Last Updated On: November 8th, 2009] [Originally Added On: November 8th, 2009]
- Preserving A Moth [Science Tattoo] | The Loom [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Another Russian rocket spiral lights up the sky | Bad Astronomy [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- A (Very Gentle) Riddle to Complete Your Saturday [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Darwin Gets Swine Flu: The YouTube Edition | The Loom [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Happy Slothy Holidays | The Loom [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Jetting to Copenhagen | The Intersection [Last Updated On: December 12th, 2009] [Originally Added On: December 12th, 2009]
- Michael Gerson Attempts Thoughtfulness on “ClimateGate,” Then Gives it Up | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Incredible VISTA of the cosmos | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Bundle up Sunday Night to Watch the Geminid Meteor Shower | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- “ClimateGate” a PR Disaster That Will Be “Taught in University Communications Courses” | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Is Google the Guardian Angel of Rainforests? | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- La ciencia es importante. Una vez mas. | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Sensenbrenner Pulls an Inhofe, Asserts Global Warming is an “International Conspiracy” | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Let Kids Eat Dirt: Over-Cleanliness Linked to Heart Disease | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- What Are The Best Science Papers Of The Past Decade? | The Intersection [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Finally! Math Shows How to Cut Evenly Sized Pizza Slices | Discoblog [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Half-baked math | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Can “Biological Passports” Save Sports From Doping? | 80beats [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Aiiiieeee! Slow down! | Bad Astronomy [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]
- Weekly News Roundup: Bad Headlines, Martian moons, and Rotating Houses | Discoblog [Last Updated On: December 13th, 2009] [Originally Added On: December 13th, 2009]