Seagulls pecked at the juvenile whales | Science 60 seconds

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BabyWhalesPeckedtoDeathbyGulls

Seagulls peck to death juvenile whales

Written/Broadcaster Jason M. Jason G. Goldman

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Reviewer Chen Louying

Gulls.Youmayhavenoticedthatgullscanbeprettyaggressivewhenitcomestograbbingfood.Butthatbehaviorismoreintensethanyoumayknow.Somekelpgullssnackonbabywhales.Livebabywhales.

You may have noticed that seagulls can act quite ferociously when they prey on them, however, the actual aggression may be beyond your imagination. Some black-backed gulls even go hunting juvenile whales, live juvenile whales.

Intheearly1970s,onlyahandfulofsouthernrightwhaleswerefeduponbykelpgullsoffthecoastofArgentina’sPeninsulaValdez. Backthenjusttwopercentofcalveseveryyearhadtosufferatthebeaksofthegulls,alongwithsomeoftheirmothers.

In the early 1970s, only a small group of southern right whales were infested by black-backed gulls in the waters off the Argentine island of Valdés. At the time, only 2% of young whales and their mothers had to be baptized by black-backed gulls pecking each year.

Butnow,99%ofthecalveshavetocontendwithhungrygullsdrivingtheirhookedbeaksdeepintotheirbacks,rippingoutchunksofskinandfleshandblubber,andgobblingitup. ThefindingisinthejournalPLOSONE. [CarinaF.Marónetal,IncreasedWoundingofSouthernRightWhale(Eubalaenaaustralis)CalvesbyKelpGulls(Larusdominicanus)atPenínsulaValdés,Argentina]

Now, 99 percent of baby whales face the dive attacks of hungry gulls, allowing their barbed beaks to penetrate deep into their dorsal spines, tearing off and devouring large areas of skin, flesh and fat. The findings were published in the Journal of the Public Science Library.

“Eachgullhasitsownwhaleanditprotectsit.” UniversityofUtahBiologistVictoriaRowntree.“ Ormaybetwogullswillhaveitsownwhale,andthey’llchaseoffanygullsthatcomein. Andtheyjustsitinthewaterwaitingforthewhaletosurfaceagain… They’rerelentless.”

"Every seagull keeps an eye on a whale and maintains sovereignty over it." Victoria Langtree, a biologist at the University of Utah, said, "Or two seagulls jointly 'possessing' a whale, they will expel other seagulls that violate their sovereignty." At the same time, they will stay on the surface of the sea, waiting for the whales to float. They are unforgiving, relentless. ”

Adultwhaleshavelearnedtoarchtheirbackswhentheysurfacetobreathe,keepingmostoftheirbodyawayfromthehungrygulls. Butthenewbornscan’tdothat.

Adult whales know how to bend down while breathing to keep their bodies as far away from hungry seagulls as possible. But young individuals don't understand how to do this.

“Youcanseethemothersgettingsoannoyed… whenfinallyshe’sbeenabletosleep,andshehasn’tarchedherback,andsheisisn’thorizontaltothesurface,andhercalfissleepingnexttoherandthenagullcomesalongandBAMMO… IthinkthestudyIdidin1998showedittook30minutesforthemtoreturntonormalbehaviorandnotdothisavoidancebehavior.”

"You can see how the mother whale becomes irritable: when it is almost asleep, its body is neither bent nor parallel to the sea, its children sleep next to it, and then a black-backed gull appears, breaking their sleep. In my 1998 study, I found that it took 30 minutes for them to circumvent themselves before they could return to their normal state. ”

Morethan600calvesdiedbetween2003and2014.Someyearsatleastafifthofallnewbornsperished.Researcherswonderifthegullsmightbe,ifnotresponsible,thenatleastcontributingtothepattern. Rowntreelookedatwhetherthedeadcalveshadmoregull-inflictedlesionsthanthosethatsurvived,butshefoundthatalloftheyoungstersgetharassed.

More than 600 juvenile whales died between 2003 and 2014. In some of these years, almost one in five newborn whales dies. The researchers believe that even if the black-backed gulls were not directly responsible for the deaths of the young whales, they contributed to the phenomenon. Langtry wanted to find out if the dead baby whales had been hit by more seagulls than the survivors, but she found that all the young whales had been infested by black-backed gulls.

It’snotthatthegullsareevil,ofcourse. Theyeattosurvive.Thechallengefortheseresearchersistocomeupwithwaysofprotectingthewhales,withoutsimplywipingoutthegulls.

Seagulls are not evil either, they just need the food they need to survive. The challenge for researchers is to find a way to protect whales rather than simply eliminate seagulls.

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