Hey diddle diddle, the cat and the fiddle, the monkey jumped over the moon. Now wait a minute. That's not how the nursery rhyme goes. Monkeys and cows are completely different. Or are they?
Actually, proboscis monkeys from Borneo and cows do have something in common: they both chew their cuds.
Proboscis monkeys are reddish-brown, long tailed primates known for their large noses. Babies are born with normal size noses, but by time they are adults, males can sport noses up to seven inches long. Proboscis monkeys are both arboreal and amphibious, which makes them good climbers and swimmers. But it's their leafy diets that have led to the evolution of a digestive tract very similar to cows.
Cows and other ruminants have multi-chambered stomachs adapted for breaking down foods that are high in cellulose, a plant fiber that resists digestion. Cows use colonies of bacteria in one chamber of their stomach to cut apart the cellulose. They also chew their cud, which means they regurgitate their food from their stomach to their mouth and re-chew it to make the pieces smaller. This behavior helps break the food into smaller and smaller pieces so that bacteria can digest as much as possible.
Like cows, proboscis monkeys eat a vegetable diet that's high in cellulose. They have a large belly which accounts for a quarter of their body weight. Their digestive system is divided into compartments similar to the cow. They also have colonies of bacteria in their gut to help digest plant material and neutralize leaf toxins. So, it's not surprising that proboscis monkeys chew their cud just like cows.
But don't expect to see them jumping over the moon any time soon.
