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MatheMUSEments
Lizard Game
By Ivars Peterson
Muse, April
1999, p. 26-27.
The rocky Coast Range of California
is the setting
for an unusual game played by the brightly colored side-blotched
lizard
(Uta stansburiana). Each male of the species has
one of three
throat colors, and each color of lizard has a different mating
behavior.
The lizards' antics are like the
game of
rock-paper-scissors. In the playground version, each of the two
players
holds a hand behind his or her back. A fist means rock, spread
fingers
mean paper, or two fingers in a "V" mean scissors. On the
count of three, the players reveal their hands. The following rules
determine the winner: Scissors cut papter, paper wraps rock, and rock
breaks scissors. If both players make the same gesture, the game is a
tie.
The lizards play a similar game.
Each type of lizard
has its own strategy for mating with females. As in
rock-paper-scissors, sometimes one strategy wins, sometimes
another.
Strategy #1: Have a Lot of
Territory
The Orange-Throated Lizard: These
males establish
large territories, with several females. The more females the more
often they can mate.
Strategy #2: Guard Your
Mate
The Blue-Throated Lizard: These
males defend small
territories holding just a few females. Because the territories are
so
small, they can guard their mates carefully.
Strategy #3: Be Sneaky
The Yellow-Striped-Throated Lizard:
These males are
sneaky and can mimic the markings and behavior of females.
So, orange-throated males are able
to grab territory
and
females from blue-throated lizards when orange-throated lizards
are rare.
But, blue-throated males can take
over a population
of yellow-striped-throated
males when blue-throated lizards are rare.
Completing the cycle,
yellow-striped-throated lizards
can
sneak into the orange-throated territories when
yellow-striped-throated
lizards are rare.
Biologists Barry Sinervo of the
University of
California at
Santa Cruz and Curt M. Lively of Indiana University have studied
how the populations of the three different types of lizards
change from year to year. They found a six-year cycle, with each
color sometimes dominating. When a population hits a low, that
type of lizard has the most babies the next year, helping to keep
the cycle going.
Stuck in an endless cycle,
side-blotched lizards keep
on
playing their never-ending mathematical game of survival.
Learn more about the amazing lizard
game at bio.research.ucsc.edu/~barrylab/lizardland/game.html
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