Study: Male crickets risk lives to keep mates safer

— -- Sir Walter Raleigh, or Jiminy Cricket, would be proud of England's male field crickets, who have startled evolutionary biologists by displaying chivalry.

Despite the added risk of becoming bird food, the gallant bugs give their mates priority in crawling into safe burrows when predators come hunting for them, researchers report. The finding, a first among insects, has intrigued biologists looking into the evolution of cooperation between the sexes in creatures large and small.

"The consequences of this chivalrous behavior are the same for men and crickets: Both can get more matings and increase their paternity," says lead study author Rolando Rodríguez-Muñoz of the United Kingdom's University of Exeter.

Though evolution seems a selfish process, the finding points to cooperation even among a species as competitive as the field cricket where males fight over mates.

"The success of this behavior seems to rely on the fact that it is also beneficial for the females," Rodríguez-Muñoz says.

He and his colleagues report on more than a thousand hours of infrared camera observations of tagged crickets in Thursday's Current Biology journal. They documented the male bug's self-sacrificing behavior, never seen in lab studies, during some 2,548 predator attacks by frogs or birds. Although coercive mate "guarding" is seen in everything from birds to antelope, the study shows how cooperation can lead to reproductive success.

"It might be surprising to see evidence of the cooperation among cricket pairs that we see in honeybees," says biologist Scott Carroll of the University of California-Davis, who was not part of the study. "Nonetheless, apparently under some circumstances, fundamentally cooperative behaviors evolve that remind us of the 'better insects' of our own nature."

Essentially, the male bugs appear to trade the risk of being eaten against the benefits of mating more with the females, in exchange for being second into the burrow. Overall, mated males were 3.9 times more likely to be eaten than unpaired ones, while mated females faced 5.6 times smaller odds of ending up in a bird's beak. The males still scrap with intruding male crickets, but make no efforts to control their mate's movements. The females paired with a male survive longer as a result, on average, than a single female.

"On a fundamental level, we can draw parallels between behaviors in people and other species," Carroll says. Recalling the famed 16th-century chivalry of Sir Walter Raleigh draping his cloak on a muddy field before England's Queen Elizabeth, Carroll adds, "Sir Walter Raleigh was being a bit of a sexy guy with his chivalry, too. He probably had more in mind for Queen Elizabeth than keeping mud off her shoes."

Further, the study reinforces the importance of field studies over lab cages to study evolution, Carroll says. "We sometimes are tempted to think there have been so many studies that we know everything," he says. "The real truth is that we know essentially nothing about the daily lives of most species."