I like penguins. I want them to be happy. I love watching them slide around and waddle like me on skis and I literally cannot watch when they get monched by seals and killer whales, even with David Attenborough's soothing voice telling me it's the circle of life. It's VICIOUS and I would 10/10 not survive.
I want them to be happy. So I was disturbed when this (research) article came across my email: "Behavioural and heart rate responses to stressors in two populations of Little Penguins that differ in levels of human disturbance and predation risk." Heart rate responses? Stressors? Predation?? What is happening to these poor penguins?
The study is on Little Penguins or, as their mothers call them when they're in trouble, Eudyptula minor. They are (as the name suggests) some of the smallest penguins on the planet, maxing out around a whopping three pounds and about 12 inches tall. Found in parts of Australia and New Zealand, these tiny flightless birds are vulnerable to 'introduced' predators like housecats and dogs (keep your pets inside or leashed!). It's a similar situation their neighbor, the kiwi, found itself in after colonizers introduced dogs, cats, and stoats to New Zealand–before that, they didn't have any natural predators. Little Penguins whose colonies are close to humans are more likely to come into contact with cats and their ilk, and that may be part of the reason their numbers have been declining over recent years. (So at least subjecting the penguins to cat calls was for a good reason.)
Chronic stress: It's not just for humans!
As part of the question for why Little Penguin populations are declining, the biologists wondered what the effect of always being on high alert for cats had on the birds. Just like humans, other mammals can suffer from chronic stress and all the problems it can bring (disrupted behaviors, diseases, and reduced reproductive success). For the penguins coming into frequent contact with predators, like cats, that could be enough to push them to be stressed out, possibly contributing to their dwindling numbers.
To test the effect cats had on penguins' stress, the researchers focused on two different colonies. One was a stable-population colony with minimal human interaction and no introduced predators, safe and sound on a tiny sandy island off the coast of Adelaide; the other was a declining-population colony on a larger, populated island with frequent human interaction as well as the presence of cats and dogs. For two hours around sunset, the researchers broadcasted cat calls and monitored the penguins' behavior from a high-definition camera hidden in a fake egg, noting when they were vigilant or in distress. For a select few individuals, they were also able to listen to their heart rates and compare them before and after the cat calls.
Penguins at both colonies reacted to the cat calls by getting stressed out, becoming visibly distressed and extra-alert while the meows were being broadcast and needing to take some time to relax afterwards. But the penguins at the site with lots of human–and cat–activity had a stronger reaction, getting more distressed and needing more time to calm down. If the penguins in the latter group are anything to go by, no wonder their populations are declining: they can't relax. And everyone knows chronic stress is the new sitting is the new smoking.
There are, of course, more factors that go into whether a colony goes extinct: actual predation, not just anxiety about the potential of being eaten, plays a big role. But this study supports the need to consider overall disturbance levels in addition to the presence of introduced predators for the Little Penguins' survival, although the researchers note the need to avoid generalizing.
And maybe keep your pets out of any penguin nests you happen across.
Bonus Neat Fact: Not all dogs are bad news for the Little Penguins: Since 2006, some specially-trained 'guardian' dogs have been successful at protecting colonies from snacky red foxes in Australia.