Hey hey hey, I’m Niba Nirmal, and I'm a Fellow here at SciShow through the AAAS Mass Media Fellows program.

I love discussing all things biology, and today, I’m here to tell you about  canaries and their immune systems. [♪ INTRO]. Unlike humans, domestic canaries don’t  have the option of social distancing when a member of their flock is ill.

But canaries may have evolved a nifty workaround for protecting their populations  when disease strikes:. Their immune systems automatically kick into  high gear at just the sight of a sick bird! And understanding exactly how  this immune response works could help researchers  understand how diseases spread through populations of canaries, and  possibly other species, including humans.

Until recently, though, it wasn’t  clear that being around illness could actually trigger a  physical response in animals. Researchers knew that various animals change their behavior in the  presence of illness, but that was it. So, to explore this question, the authors of a 2021 study conducted  an experiment on domestic canaries.

First, they infected several canaries with a  bacterium that causes respiratory infections. Then, they put a cage of healthy canaries  in the same room as the infected birds. The healthy birds could see the sick ones, which had visible symptoms  like pink eye and lethargy, but their cages were far enough apart to  protect them from infection themselves.

The team also put a second group of  canaries in the room as a control. The only difference was that this  group could not see the sick birds, thanks to a room divider  blocking their line of sight. For almost a month after that, the researchers tracked the health and  immune responses of all the canaries.

Blood samples showed that  none of the healthy birds caught the respiratory infection  from the sick birds, as expected. But, surprisingly, the immune system  of the birds in the experimental group   still kicked into high gear. The birds that could see the sick birds  had elevated numbers of white blood cells, which the body generates to  fight off invaders like bacteria.

And they also had higher levels of activated  complement proteins in their blood. These proteins are typically activated in an immune response to an  infection to burst invading cells. So the birds were responding as if they were sick, even though none of them  actually had an infection.

Meanwhile, the control group showed  no change in their immune systems. These findings suggest that just seeing  evidence of sickness in fellow canaries is enough to trigger an immune  response in these birds. Researchers hypothesize that this strategy evolved as a way to keep these birds from getting sick even though they’re in such  close contact with each other.

This early immune response acts as a way  of preemptively blocking an infection. Generating more white blood cells and mobilizing more complement  proteins can burn a lot of energy. But it allows these birds to reap the benefits of  social living while keeping diseases at bay.

And canaries may not be unique. In a 2010 study, researchers found that humans’ white  blood cell activity also ticked up when they just looked at  images of disease symptoms. Researchers think this physical response is linked to what’s called the  human behavioral immune system.

This branch of our immune system  encompasses all of the behaviors we have that serve as a first line  of defense against illness. It’s what makes us feel grossed  out by dirty places or rotten food, which could potentially make us sick. But in addition to these behavioral responses, the behavioral immune system may be triggering  a physical immune response as well.

Understanding this subconscious  response in canaries and other species could offer us new insight into how  illnesses move through populations. And while it’s still a ways off,  that may eventually help researchers develop new ways of preventing or slowing  down the spread of diseases in the future. If you enjoyed this video, catch me on  our TikTok for more about weird biology.

Thanks for watching this episode of SciShow! [♪ OUTRO].