Newly hatched magellanic penguin chicks in breeding groundswith a large number of human visitors show a significant spike inlevels of a stress-related hormone compared to chicks hatched in areasnot visited by humans, a University of Washington research team hasfound.
It wasn't until chicks with limited human exposure reached40 to 50 days old that they showed a stress response like the newlyhatched chicks in areas frequented by humans, said researcher BrianWalker, who led the work as part of his doctoral thesis at the UW. Heis now an assistant professor of biology at Gonzaga University inSpokane.
Magellanic penguin chicks are hatched in a very immatureand helpless condition. Walker's group found that by the time theyreached 70 days old, nearly the time of fledging, chicks inhuman-visited areas had become far more accustomed to the presence ofpeople than those in non-visited areas.
"In the tourist areas,you can walk among them and they put up with you. But when you walkover the hill to the places where tourists don't go, they're much moreskittish. They run away or dive into their nests," he said.
Theresearch was conducted at a penguin reserve at Punta Tombo, Argentina,with three separate sampling periods in November and December 2001 andJanuary 2002. Chicks aged 6 to 7 days were captured and blood was drawnto measure the level of a hormone called corticosterone. The firstsample was obtained within three minutes of capture to establish abaseline because, unlike a hormone such as adrenaline, it takes severalminutes for corticosterone to build up in the bloodstream after astressful event, such as being captured. Additional blood samples weredrawn after 30 and 60 minutes. The same procedures were followed whenthe chicks were 40 to 50 days old and again two weeks before fledging,which occurs when the chick is about 75 days old.
None of thechicks demonstrated an elevated baseline corticosterone level. But 30minutes and 60 minutes after capture, newly hatched chicks regularlyvisited by humans had levels more than three times higher thanundisturbed chicks. At 40 to 50 days old, the levels were nearly thesame for chicks at 30 and 60 minutes after capture, and for those nearfledging the levels were almost identical between visited andundisturbed chicks.
But even when the hormone levels evened outbetween the two groups as the chicks got older, their behavior wasdifferent. Nearly fledged chicks in tourist areas did not flee untilpeople were within two feet, while those in the areas not visited bytourists sought safety when people were still 30 feet away.
Theresearch will be published in the October issue of ConservationBiology, a journal of the Society of Conservation Biology. Co-authorsare Dee Boersma and John Wingfield, UW biology professors and Walker'sdoctoral advisers. The work was funded by the Wildlife ConservationSociety, the American Ornithologists' Union and the American Museum ofNatural History.
There is no evidence of short-term negativeeffects, such as different growth rates or weight differences atfledging, caused by distinct differences in corticosterone levelsbetween newly hatched chicks in tourist and non-tourist areas of thereserve, Walker said. But it is unclear what later effects the elevatedstress hormones might have.
"We don't know yet what it means --it might mean nothing, but it will take more research to be sure," hesaid. "We are seeing evidence in other species, including humans, thatsome detrimental physiological changes that happen to adults can onlybe traced back to stressful situations or elevated corticosteronelevels when they were young."
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