When it comes to naturally occurring spicy foods, some animals are more fit than others to enjoy them. Humans and other mammals aren’t so well equipped to handle those foods. Take the chili pepper, for example. While it’s a food rich in anti-inflammatory and antioxidant properties and serves as an excellent source of vitamin C, it contains capsaicin — a chemical that makes peppers taste spicy and interacts with the nerve receptor known as TRPV1.Â
While some humans may classify the tingling and burning associated with capsaicin as pleasant, it is a fierce deterrent for animals. The Environmental Protection Agency actually classifies capsaicin as a biochemical pesticide and animal repellant. However, not every animal shies away from spicy foods. Some can handle the heat without breaking a sweat.
Natural Aversions to Spice
Mammals, including humans and rodents, have pain receptors that can be activated by injury, acid, heat, and the phytochemical capsaicin. Capsaicin can be lethal to rats and mice, and symptoms of acute oral toxicity can include a staggering gait, skin redness, and cyanosis — blue lips, nail beds, and skin due to low oxygen levels.Â
“Squirrels and mice show a natural aversion to spicy foods,†says Joanna Herberger, a veterinarian at PetSprint. “We can attribute this behavior to an evolutionary response to avoid potentially harmful plants.â€
But evolution is also the culprit for the tree shrew’s remarkable insensitivity to capsaicin. Tree shrews have a gene mutation that bolsters their tolerance towards spicy foods, an adaptation that gives them a distinct advantage to consuming plants in their habitat, according to Luqman Javed, an in-house veterinarian for PangoVet.Â
Read More: How Do We Tolerate Spicy Food?
Birds Help Spicy Plants Grow
Other animals that can withstand the heat include birds. African gray parrots, chickens, songbirds, and other avian species have capsaicin-immune pain receptors that negate the heat-inducing unpleasantness associated with peppers. Incidentally, this resistance to the pain-producing qualities of capsaicin is key to the fertilization of spicy plants, according to Javed.
“Many birds serve important roles as seed dispersers,†Javed says. “Being able to withstand the undesirable flavor of the peppers [produced by the capsaicin in spicy plants] would allow birds to consume these seeds, fly far away, and then disperse them in their droppings.â€
Chili peppers may have evolved this way because birds are better at dispersing their seeds than mammals. Interestingly enough, because of the adaptive way TRPV1 receptors work in birds, capsaicin may register as a pleasant vanilla flavor that incentivizes seed dispersion, according to the European Journal of Pharmacology.Â
Read More: Eating spicy food might help you live longer
Animals That Should Avoid Spice
Most pets, including dogs, cats, and rabbits, should not eat spicy foods, but this rule of thumb also applies to farm animals like cows. If an animal has taste receptors for capsaicin, it will likely experience discomfort after ingesting heat-inducing foods like chili peppers and jalapeños.Â
Dogs can experience short-term gastrointestinal distress from spicy foods, like flatulence, and more distressing symptoms, like vomiting and diarrhea. Spicy foods like jalapeño peppers also pose a threat to cats because they can irritate their nose and mouth, and the oils can sting the eyes.Â
While some pet owners feed their rabbits chilis, it is generally inadvisable due to the potential for gastric upset. However, under the category of non-leafy greens — which compose 25 percent of a rabbit’s diet — banana peppers and green bell peppers are considered safe foods.
“While most pets should not be fed spicy foods at all, there are some mild spices that can be tolerated in very small amounts and under careful supervision,†says Bethany Hsia, mobile veterinarian and a co-founder of CodaPet. “Those mild spices include cinnamon, ginger, and turmeric.â€
Read More: What Foods Are Healthy For Dogs and What Should They Avoid?
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