There are about 2,000 long-nosed, inquisitive-faced tree shrews that reside in Yunnan, China in the Kunming Institute of Zoology. These tree shrews are the only mammal besides humans known to consume hot chili peppers.
Tree shrews are known for being good animal models for the studying of human diseases. An email from Shilong Yang, Kunming Institute biologist, said, “We were trying to find the favorite food of the tree shrew.” Yang and his colleagues found the answer - chili peppers.
Scientists were surprised when they found out the favorite food of the tree shrews was chili peppers because most mammals dislike the taste and heat of chili peppers or spicy foods in general. The reason chilis are hot is because of the capsaicinoids they contain. While keeping a group of tree shrews in the lab for studying, the researchers increased the amount of capsaicinoids in their food over time. They found that it caused a slight increase in the amount of food the tree shrews consumed. A mutation in a particular protein, called the capsaicin receptor, lowers sensitivity to the capsaicinoids in peppers which makes it easier for tree shrews to eat them.
Wild tree shrews’ favorite pepper plant is called piper boehmeriaefolium, which they prefer over ginger and garlic. Tree shrews are more similar to birds than humans. Birds share the tolerance of capsaicinoids with shrews and act as seed dispersers. The shrews also share more similar genetics with humans than mice.
Other mammals have been tested to see if they are able to handle spicy foods, but tree shrews have been the only ones to successfully consume them.