Make us your home page

Today’s top headlines delivered to you daily.

(View our Privacy Policy)

USF researchers: Stressed birds more likely to be bit by mosquitoes

USF researchers found that birds with higher concentrations of a stress hormone are twice as likely to be bitten by mosquitoes.

University of South Florida

USF researchers found that birds with higher concentrations of a stress hormone are twice as likely to be bitten by mosquitoes.

TAMPA — A hungry mosquito is more likely to bite the bird with ruffled feathers, according to new research from the University of South Florida, another step in understanding the spread of mosquito-borne viruses.

The new study, published this month, found that birds with higher levels of stress hormones are twice as likely to get bitten by mosquitoes. During the year-and-a-half-long study, disease-carrying mosquitoes proved to be attracted to the hormone corticosterone, which is nearly identical to the stress hormone cortisol produced by humans.

That attraction can spark a big ripple effect, particularly in urban areas, the researchers said. If more birds are exposed to stresses such as light pollution or road noise from urbanization, they'll attract more mosquitoes. If those birds happen to be carrying diseases like West Nile Virus or Eastern Equine Encephalitis, there is a greater chance the disease could be spread and humans infected. (Scientists do not believe birds carry the Zika virus.)

"We were asking whether mosquitoes could, in a sense, smell stress and, lo and behold, not only do they do it, they seem incredibly adept at doing it," said the study's principal investigator Dr. Lynn Martin, associate professor in the USF Department of Integrative Biology.

It's still unclear if elevated stress hormones in humans also attract mosquitoes, but the birds' hormones are similar enough that it's worth studying, he said.

The team began by putting three zebra finches in a cage with mosquitoes. One bird was injected with high levels of corticosterone, one with medium levels of the hormone and one with normal levels. The mosquitoes were left to feed on the birds overnight and, in the morning, underwent DNA testing that showed which blood in their bodies came from which bird.

Mosquitoes key in on their hosts using a multitude of signals, from physical movement to body temperature to detecting carbon dioxide. Yet the birds with the higher hormone levels were bitten twice as much as the others, said co-investigator Aaron Schrey, an assistant professor at Armstrong State University in Georgia.

"When I did the analysis I intentionally didn't know which insects were which, but the results I saw were really clear. They would definitely bite on the ones with the higher hormones," Schrey said.

In a second study, each zebra finch was kept in a cage by itself to see how the different levels of stress hormones helped them defend against the mosquitoes. The stress hormones made the birds more defensive, increasing actions like shaking their head, hopping or preening their feathers, but surprisingly the mosquitoes were still able and willing to bite the birds with elevated hormone levels, Martin said. The researchers also found that those birds didn't necessarily make the most nourishing meal, or result in the mosquitoes laying more eggs after feeding.

"I think that the signals coming from the birds are so incredibly compelling that the mosquitoes out in the wild, if they get any signal at all that some tasty host is around, they're going to go for that, even if it's not the best meal," Martin said. "They bite the first one they find and, often times, that's going to be the stressed one."

The next step for the researchers is to see if the same results are found out of the lab and in the wild. The researchers will also continue to "scale up" their thinking, and raise more questions about how the hormonal changes of one animal can affect a population, said Stephanie Gervasi, postdoctoral fellow on the project who is now at the Monell Chemical Senses Center in Philadelphia.

"The cool thing is it really led to a lot of questions about the birds, the mosquitoes and what it is they liked so much about those birds, something they smell that changes what the mosquitoes use to find them and bite them," Gervasi said.

An earlier version of this story suggested that birds carry Zika, which has not been proven.

Contact Anastasia Dawson at or (813) 226-3377. Follow @adawsonwrites.

USF researchers: Stressed birds more likely to be bit by mosquitoes 08/20/16 [Last modified: Sunday, August 21, 2016 3:59pm]
Photo reprints | Article reprints

© 2017 Tampa Bay Times


Join the discussion: Click to view comments, add yours

  1. Gradebook podcast: On hate speech at UF, and education reform in the Florida Legislature


    National events hit Florida hard this week, as the white nationalist group at the center of violent protests in Virginia worked to cement plans for a rally in Tally. Uni …

  2. Mother of woman killed in Charlottesville say she will not speak to Trump


    The mother of the woman who was run down by a car during violent clashes in Charlottesville, Va., said Friday that after seeing President Donald Trump's comments equivocating between white supremacist protesters and those demonstrating against them, she does not wish to speak with him.

    Susan Bro, mother to Heather Heyer, speaks during a memorial for her daughter on Wednesday, Aug. 16, 2017, at the Paramount Theater in Charlottesville, Va.  Heyer was killed Saturday, when a car rammed into a crowd of people protesting a white nationalist rally.  [Andrew Shurtleff | Daily Progress via AP]
  3. Florida's unemployment rate remains the same


    After four consecutive months of decline, Florida's unemployment rate is leveling out. The state's unemployment rate was 4.1 percent in July, the same as June according to state figures released Friday.

    Florida's unemployment rate was 4.1 percent in July, unchanged from June, state figures released Friday said. Pictured is a job fair. | [Times file photo]
  4. Tina Fey urges Americans: Stay home from neo-Nazi rallies. Eat a sheet cake instead. (w/ video)

    The Feed

    Tina Fey is fuming about last weekend's violence in Charlottesville, home to her alma mater, the University of Virginia.

    In a surprise appearance on SNL's Weekend Update: Summer Edition Thursday night, Fey urged Americans not to get into screaming matches with neo-Nazis. Instead, she said, "order a cake with the American flag on it ... and just eat it." [Photo from video]
  5. Trump bashing aside, Democrats struggle for united message

    State Roundup

    It should be a golden opportunity for Democrats: The nonstop controversy surrounding President Donald Trump and the failure of Republicans on Capitol Hill to get much done.

    Democratic Leader Rep. Nancy Pelosi, D-Calif., speaks at the U.S. Capitol in Washington, DC, on July 26, condemning president Trump's tweets stating that he plans to limit the ability of transgender people to serve in the military. (Alex Edelman/Zuma Press/TNS)