Happy October 16, foodies! This day is World Food Day to celebrate the founding of the Food and Agriculture Organization of the United Nations in 1945. But the history of food is way longer than that. No living thing can survive without food. But lifeforms define "food" in different ways. 

Bamboo is not the one and only food that giant pandas can eat. /VCG Photo

The giant panda: rats

Everyone knows that the giant panda feeds on bamboo. Do you know it's a carnivore? In fact, though bamboo is its main food source, the giant panda will not refuse some meat from time to time. It still has the digestive system and teeth for meat and eggs. Some have even been spotted hunting bamboo rats in the wild. 

It is a wolf, and it eats fruit! /VCG Photo

The wolf: fruit

The maned wolf is a very special: It is omnivorous, and more than 50 percent of its diet consists of vegetables, including tubers, sugarcane and fruits. Though it preys on small animals, it apparently has sweet teeth! 

Herbivores are not always the ones that get eaten. /VCG Photo

The deer: carcasses

A study published in 2017 frightened many netizens: Scientists observed a white-tailed deer eating a corpse. In fact, many herbivores are seen eating meat, fish or shells. The common herbivores, such as deer, buffalo, horse and hippo, do not refuse meat as food. They mainly feed on plants only because their body structures do not allow them to hunt. 

The koala has the "superpower" of detoxicating eucalypt leaves. /VCG Photo

Some: toxic things

The koala feeds on toxic eucalypt leaves. The golden snub-nosed monkey feeds on toxic lichen. Pikas, marmots, possums, deer, moose and elk all have this "superpower" to digest poisonous plants. Some caterpillars, ants and certain species of bees also feed on toxic plants, even feed poisonous pollen to their larvae on purpose. 

The orangutan sometimes eats soil. Scientists are still not sure why. /VCG Photo

Others: dirt and soil

The soil is a popular snack among many species of birds! It is believed that birds can get extra nutrients from dirt and soil, which would be particularly useful when producing eggs and rearing young. Interestingly, our primate cousin – the orangutans – have the similar hobby of eating soil. 

The baby penguin's infant formula: half-digested seafood. /VCG Photo

Those: vomit...

Have you ever seen a chick getting fed from the parent's throat? Many birds throw up food to feed their chicks. Penguins travel miles to feed themselves, and vomit the ingested food to feed the baby penguins. The pigeons have a similar method, but they do not "vomit" food. Instead, they secrete milk-like fluids for their chicks. 

In Chinese, the skua is called "thief gull." /VCG Photo

A real vomit-eater is much worse than that – the skua often plays dirty and chases other birds until the victim throws up. Then the skua gets a free meal, though it is disgusting, and not legitimately acquired. 

Guinea pigs may die if they do not get to eat poop...... /VCG Photo

And those: poop...

Many animals are poop eaters, including rabbits and hares, guinea pigs, chinchillas, kangroos, koalas, and even gorillas. Plant-eaters burn more energy than large herbivores do, so they need to reap more energy from their food. Every bit cannot be wasted. Also, the young cubs obtain vital microorganisms from parents' droppings. 

And of course there is this guy...

The hardworking dung beetle. /VCG Photo

So, what have you eaten today? 

 (All images via VCG)

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