Want to gross out a chimpanzee? Study reveals they recoil from food placed near soft, moist objects
- Study tested how exposure to contaminants influences chimps’ feeding choices
- They observed their responses based on visual, smell, and tactile cues
- When chimps couldn't see food, but felt it atop a piece of dough, they recoiled
It’s a scenario sure to make anyone cringe – you’re feeling around for something in the darkness, when your hand suddenly encounters something soft and moist.
Most people would immediately recoil, and now, scientists have discovered that chimpanzees react this way, too.
While chimps are known to do all sorts of things that would gross out a human, including eating seeds they picked out of feces, a new study found they often draw the line at squishy materials.
The behaviour may serve a purpose similar to the origins of disgust in humans, helping chimps avoid substances that are more likely to host biological contaminants.
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The chimpanzees were presented with an opaque box that would allow them to reach in and grab the food without seeing it. But, the food was placed either atop a piece of rope, or soft and moist piece of dough. The researchers found they instantly recoiled from the dough
Not only do chimpanzees pick seeds from feces and re-ingest them, but they’re also known to deliberately eat their own fecal matter and that of their close family members.
But, they avoid the bodily products of anyone else.
In effort to determine what grosses out a chimpanzee, researchers from Kyoto University’s Primate Research Institute observed chimps at the Primate Center at CIRMF in Gabon.
‘If chimpanzees and other primates can discern contamination risk via different cues, individuals with higher sensitivities to feces and other bodily fluids may be less infected, which could have important health benefits,’ explains Cecile Sarabian, the lead author of the study.
‘Moreover, such results may have implications for animal welfare and management.
'We can better inform staff and keepers about the adaptive value of such sensitivity and its flexibility, as well as identify which individuals may be more at risk of infection and therefore require more attention.’
The team set up a number of experiments to test how potential exposure to biological contaminants influences chimps’ feeding choices based on visual, olfactory, and tactile cues.
In one trial, they created replica feces, and compared the chimps’ responses to food placed atop the pile, and that placed on a piece of brown foam.
While the sight of feces did make the chimps hesitate before eating the food, the researchers found it wasn’t enough to stop them in the end.
And, neither was the smell.
In the tactile experiments, however, the researchers found much stronger reactions.
The chimpanzees were presented with an opaque box that would allow them to reach in and grab the food without seeing it.
In one trial, they created replica feces, and compared the chimps’ responses to food placed atop the pile, and that placed on a piece of brown foam
While the sight of feces did make the chimps hesitate before eating the food, the researchers found it wasn’t enough to stop them in the end
But, the food was placed either atop a piece of rope, or a soft, moist piece of dough.
The chimpanzees had little issue taking the food when the rope was present – but, they immediately recoiled at the touch of the dough.
This reaction may not be disgust as we know it, the researchers say, but it could provide important insight on the evolutionary origins of contaminant avoidance.
Soft, moist substrates are far more likely to be rich in biological contaminants than substances that are hard and dry.
The behaviour may serve a purpose similar to the origins of disgust in humans, helping chimps avoid substances that are more likely to host biological contaminants. A stock image is pictured
‘While anyone watching the reactions of these chimpanzees in the tactile experiments can empathize with them, it’s premature to say that they feel the same as we might in that situation,’ said Andrew MacIntosh, senior author on the study.
‘What’s great about these experiments, though, is that the observed responses are functionally similar to what ours would be, providing evidence that the mechanism underlying their behaviour could be similar to ours.’
‘These experiments hint at the origins of disgust in humans, and help us better understand the protective function of this emotion,’ added Cecile Sarabian.
‘We are currently in the process of expanding our “disgusting” work to include other primate and non-primate species.’
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