"Long before it's in the papers"
January 27, 2015

RETURN TO THE WORLD SCIENCE HOME PAGE


Crickets risk lives for their mates, study finds

Oct. 7, 2011
Courtesy of Cell Press
and World Science staff

Chiv­al­ry is­n’t dead among in­sects, it seems. New re­search sug­gests that when a mat­ed pair of crick­ets is out to­geth­er, a male will give a female pri­or­ity ac­cess to a safe bur­row, though it greatly in­creases his own risk of be­ing de­voured.

The stu­dy, based on in­fra­red videos of wild field crick­ets, was pub­lished Oct. 6 in the ad­vance on­line edi­tion of the re­search jour­nal Cur­rent Bi­ol­o­gy.

A vi­deo show­ing "chivalrous crickets" cre­at­ed by the au­thors of new re­search on the in­sects. (Cred­it: Cur­rent Bi­ol­o­gy, Cell Press, Rodríguez-Muñoz et al. )


“Many peo­ple probably think that ‘chival­rous’ be­hav­ior is ex­clu­sive of hu­mans or closely re­lat­ed mam­mals, link­ing it in some way to edu­ca­t­ion, in­tel­li­gence, or af­fec­tion,” said Ro­lando Ro­drí­guez-Mu­ñoz of the Uni­vers­ity of Ex­e­ter. “We show that even males of small in­sects, which we would not de­fine as in­tel­li­gent or af­fec­tive, can be ‘chival­rous’ or pro­tec­tive with their part­ners. Per­haps it shines a light on the fact that ap­par­ently chiv­al­rous acts may have ul­te­ri­or mo­tives. Did Sir Wal­ter Ra­leigh throw his cape on­to a mud­dy pool in front of Queen Eliz­a­beth just be­cause he was a nice guy? I think not.”

The crick­et phe­nom­e­non is one form of a be­hav­ior al­ready doc­u­mented by oth­er sci­en­tists among some an­i­mals, in which males ap­pear to “guard” fema­les, Ro­drí­guez-Mu­ñoz and col­leagues said. But the usu­al in­ter­preta­t­ion is that males are try­ing to ma­ni­pu­late females and keep them from mat­ing with ri­vals, an ex­plana­t­ion that does­n’t seem to apply very clearly in this case. This is­n’t to say their be­hav­ior is truly al­tru­is­tic, they note: the male crick­ets are probably re­warded for their risky be­hav­ior, as their ex­tend­ed stays with females win them more off­spring.

Most pre­vi­ous stud­ies of crick­et mat­ing be­hav­ior had been con­ducted in the lab. Those find­ings had led re­search­ers to con­clude that male crick­ets force females to stay with them to keep them from mat­ing with ri­vals or from eject­ing the ma­le’s al­ready in­sert­ed sper­m—some­thing female crick­ets can do.

Ro­drí­guez-Mu­ñoz and colleagues studied wild field crick­ets, the spe­cies Gryl­lus cam­pes­tris, by mark­ing in­di­vi­du­als and track­ing them by their DNA. They found that lone female and male crick­ets suf­fer si­m­i­lar rates of preda­t­ion, but when a pair is at­tacked, the fema­le’s chances of sur­viv­al in­crease as the ma­le’s chances drop. In com­pensa­t­ion for their in­creased preda­t­ion risk, paired males mate more fre­quently and fa­ther more of their part­ner’s off­spring, the re­search­ers said.

Tre­genza said males do tend to stay far­ther away from bur­rows when females are around, but that did­n’t seem to be enough to ex­plain the find­ings. “It looks like males really wait un­til a female is un­der cov­er be­fore get­ting them­selves to safe­ty,” he said. “Guard­ing seems to be their top pri­or­ity.”

In ef­fect, the male crick­ets trade a long­er life span for great­er suc­cess in fa­thering off­spring with each of their part­ners, the sci­en­tists main­tain. They sus­pect that the de­gree of chiv­al­rous be­hav­ior among males should vary de­pend­ing on fac­tors such as the size of the crick­et and pred­a­tor popula­t­ions.

“We are look­ing for­ward to see­ing wheth­er chiv­al­ry pre­vails in fu­ture genera­t­ions,” Ro­drí­guez-Mu­ñoz said, not­ing that the cur­rent study is based on three con­sec­u­tive mat­ing sea­sons. “There may be some years when both sexes be­have in a more ob­vi­ously self­ish fash­ion and at­tempt to es­cape down the bur­row first.”


* * *

Send us a comment on this story, or send it to a friend









 

Sign up for
e-newsletter
   
 
subscribe
 
cancel

On Home Page         

LATEST

  • St­ar found to have lit­tle plan­ets over twice as old as our own

  • “Kind­ness curricu­lum” may bo­ost suc­cess in pre­schoolers

EXCLUSIVES

  • Smart­er mice with a “hum­anized” gene?

  • Was black­mail essen­tial for marr­iage to evolve?

  • Plu­to has even cold­er “twin” of sim­ilar size, studies find

  • Could simple an­ger have taught people to coop­erate?

MORE NEWS

  • F­rog said to de­scribe its home through song

  • Even r­ats will lend a help­ing paw: study

  • D­rug may undo aging-assoc­iated brain changes in ani­mals

Chivalry isn’t dead among insects, it seems. New research suggests that when a mated pair of crickets is out together, a male will give a female priority access to a safe burrow, though it greatly increases his own risk of being devoured. The study, based on infrared videos of wild field crickets, was published Oct. 6 in the advance online edition of the research journal Current Biology. “Many people probably think that ‘chivalrous’ behavior is exclusive of humans or closely related mammals, linking it in some way to education, intelligence, or affection,” said Rolando Rodríguez-Muñoz of the University of Exeter. “We show that even males of small insects, which we would not define as intelligent or affective, can be ‘chivalrous’ or protective with their partners. Perhaps it shines a light on the fact that apparently chivalrous acts may have ulterior motives. Did Sir Walter Raleigh throw his cape onto a muddy pool in front of Queen Elizabeth just because he was a nice guy? I think not.” The cricket phenomenon is one form of a behavior already documented by other scientists among some animals, in which males appear to “guard” females, Muñoz and colleagues said. But the usual interpretation is that males are trying to manipulate females and keep them from mating with rivals, an explanation that doesn’t seem to apply very clearly in this case. This isn’t to say their behavior is truly altruistic, they note: the male crickets are probably rewarded for their risky behavior, as their extended stays with females win them more offspring. Most previous studies of cricket mating behavior had been conducted in the lab. Those findings had led researchers to conclude that male crickets force females to stay with them to keep them from mating with rivals or from ejecting the male’s already inserted sperm—something female crickets can do. In the new study, Rodríguez-Muñoz and others tracked what happens in the wild as field crickets, the species Gryllus campestris, live their lives by marking and tracking insects by their DNA. They found that lone female and male crickets suffer similar rates of predation, but when a pair is attacked, the female’s chances of survival increase as the male’s chances drop. In compensation for their increased predation risk, paired males mate more frequently and father more of their partner’s offspring, the researchers said. Tregenza said males do tend to stay farther away from burrows when females are around, but that didn’t seem to be enough to explain the findings. “It looks like males really wait until a female is under cover before getting themselves to safety,” he said. “Guarding seems to be their top priority.” In effect, the male crickets trade a longer life span for greater success in fathering offspring with each of their partners, the scientists maintain. They suspect that the degree of chivalrous behavior among males should vary depending on factors such as the size of the cricket and predator populations. “We are looking forward to seeing whether chivalry prevails in future generations,” Rodríguez-Muñoz said, noting that the current study is based on three consecutive mating seasons. “There may be some years when both sexes behave in a more obviously selfish fashion and attempt to escape down the burrow first.”