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A Wilder View: How do animals know when it's time to stop eating?

Wild animals have evolved mechanisms similar to our own to regulate their food intake and determine when they're full.
Wolf Eating
Posted at 8:20 AM, Oct 16, 2023

MISSOULA — You and I know when we've had enough to eat, but my dog seems to be a bottomless pit. How do animals in the wild know when to stop so they don't get sick?

Whether it’s a big meal with friends or a Thanksgiving dinner, we all anticipate that moment when we lean back in our chairs and exclaim, "Well, I'm stuffed!" It's a shared experience among people — knowing when we've had enough to eat.

For wildlife, much like our extravagant Thanksgiving dinners, there are times when indulgence becomes a survival necessity. Overeating can be a boon in certain situations. Consider the annual spectacle known as "Fat Bear Week," where bears bulk up before the winter.

Birds embark on long migrations after gorging themselves, and male African lions can devour up to 90 pounds of prey in one go. Their overindulgence is a response to the unpredictable intervals between meals, which could stretch for days or even a week. Herbivores, too, stick to a consistent eating pattern to meet their nutritional needs.

Wild animals, it turns out, have evolved mechanisms similar to our own to regulate their food intake and determine when they're full.

One of these mechanisms is the Vagus Nerve, often dubbed the "brain in your stomach." This nerve houses sensory neurons that constantly monitor signals from the stomach and intestines, transmitting this vital information to the brain. It's all involuntary, beyond conscious control, and it's what gives us that feeling of fullness when our stomachs stretch.

But it doesn't end there. Animals possess nutrient-sensing mechanisms that help them figure out what nutrients they require from their diet —-whether it's carbohydrates, amino acids, fatty acids, minerals, or water. These mechanisms enable them to maintain a balanced diet.

Interestingly, animals have bitter receptors on their tongues and inside their mouths. These receptors detect and react to bitter compounds in their food, serving as a defense against potentially harmful or toxic substances in their diet. Hormones also play a pivotal role in regulating appetite. Ghrelin — known as the "hunger hormone" — signals to their brains that it's time to eat, while Leptin signals fullness.

In some cases, external factors come into play. Hot temperatures or stressful city environments can cause animals to adjust their eating habits. Social factors can also influence when they stop eating. For instance, wolves may stop to ensure every pack member gets a share of the prey.

So, the next time you're savoring your Thanksgiving feast, remember that our wild counterparts share in the age-old dance of dining and discerning when to push away from the table.