The rainbow-splashed tails of lizards fade with age, a costume change that is a consequence of different feeding behaviors in juveniles versus adults, new research suggests.
Juvenile lizards actively search for food, exposing themselves frequently to danger from lurking predators. By flashing an eye-catching tail, the lizards can deflect attacks to this appendage, which can re-grow if severed. Later in life when the lizard switches to less active food finding, the dazzling decoy becomes unnecessary.
The scientists, led by Dror Hawlena of Ben-Gurion University of the Negev in Beer-Sheva, Israel, monitored blue-tailed lizards during their typical one-year life spans. At hatching, the baby lizards all wore bright-blue tails, and by three weeks of age, 85 percent had lost the tail coloration and also their striped body patterns.
The lizard's main predator at the study site was a carnivorous bird, the great grey shrike, which hunts from perches and has excellent color vision.
To survive an ambush the juvenile lizards in the study used two tail displays—a fast, delicate vibration and a slower undulation—more frequently than when they matured. Since juveniles are so active there is a greater probability of encountering predators, and they are less likely to spot the unexpected enemy. So the tail displays can be lifesavers.
At about three weeks old, the lizards became less active and relied on the safer sit-and-wait method of finding food. While stationary, the adults are more likely to spot a predator in time to escape.
"The ultimate experiment to explore our hypothesis further would be to manipulate tail color and to examine survival consequences when lizards use either of the two foraging modes," the authors stated in their research paper, published in the November/December issue of the journal Behavioral Ecology.
Researchers said that while they can't directly apply the results to other species, it could hold true for other lizards that experience the color change.
Three Lizards, Three Behaviors
Male side-blotched lizards come in three throat colors--blue, orange, and yellow--and scientists have noticed that each variety displays strikingly different behavior.
The blues form partnerships, the oranges are aggressive, and the yellows are sneaky.
For example, if a pair of blue-throated males are protecting their territory from orange-throated bullies. One blue throat will selflessly step forward to battle the intruder, thereby sacrificing his own chances to successfully mate. As the blues and oranges battle it out, the yellow throats sneak into unprotected territories to find females.
Scientists have long wondered why this altruistic behavior exists since it runs contradictory to an animal's goals of surviving to pass its genes to future generations.
Now Barry Sinervo, of the University of California, Santa Cruz, and colleagues have shown that while altruism may hurt a fighting blue throat's own reproductive chances, it secures the persistence of their genes in future generations by enabling other blue males to mate.
After studying the genomes of males of each throat color, Sinervo determined that at least three other genetic factors other than throat color are at play during the self-sacrificing behavior.
"On the surface, cooperation in the absence of close-relatedness can seem to be evolutionarily counterproductive--but Sinervo explored the genes that underlie cooperative behavior and discovered how they can affect the genetic composition of future generations," said Mark Courtney of the National Science Foundation.
Juvenile lizards actively search for food, exposing themselves frequently to danger from lurking predators. By flashing an eye-catching tail, the lizards can deflect attacks to this appendage, which can re-grow if severed. Later in life when the lizard switches to less active food finding, the dazzling decoy becomes unnecessary.
The scientists, led by Dror Hawlena of Ben-Gurion University of the Negev in Beer-Sheva, Israel, monitored blue-tailed lizards during their typical one-year life spans. At hatching, the baby lizards all wore bright-blue tails, and by three weeks of age, 85 percent had lost the tail coloration and also their striped body patterns.
The lizard's main predator at the study site was a carnivorous bird, the great grey shrike, which hunts from perches and has excellent color vision.
To survive an ambush the juvenile lizards in the study used two tail displays—a fast, delicate vibration and a slower undulation—more frequently than when they matured. Since juveniles are so active there is a greater probability of encountering predators, and they are less likely to spot the unexpected enemy. So the tail displays can be lifesavers.
At about three weeks old, the lizards became less active and relied on the safer sit-and-wait method of finding food. While stationary, the adults are more likely to spot a predator in time to escape.
"The ultimate experiment to explore our hypothesis further would be to manipulate tail color and to examine survival consequences when lizards use either of the two foraging modes," the authors stated in their research paper, published in the November/December issue of the journal Behavioral Ecology.
Researchers said that while they can't directly apply the results to other species, it could hold true for other lizards that experience the color change.
Three Lizards, Three Behaviors
Male side-blotched lizards come in three throat colors--blue, orange, and yellow--and scientists have noticed that each variety displays strikingly different behavior.
The blues form partnerships, the oranges are aggressive, and the yellows are sneaky.
For example, if a pair of blue-throated males are protecting their territory from orange-throated bullies. One blue throat will selflessly step forward to battle the intruder, thereby sacrificing his own chances to successfully mate. As the blues and oranges battle it out, the yellow throats sneak into unprotected territories to find females.
Scientists have long wondered why this altruistic behavior exists since it runs contradictory to an animal's goals of surviving to pass its genes to future generations.
Now Barry Sinervo, of the University of California, Santa Cruz, and colleagues have shown that while altruism may hurt a fighting blue throat's own reproductive chances, it secures the persistence of their genes in future generations by enabling other blue males to mate.
After studying the genomes of males of each throat color, Sinervo determined that at least three other genetic factors other than throat color are at play during the self-sacrificing behavior.
"On the surface, cooperation in the absence of close-relatedness can seem to be evolutionarily counterproductive--but Sinervo explored the genes that underlie cooperative behavior and discovered how they can affect the genetic composition of future generations," said Mark Courtney of the National Science Foundation.