Why do most mammals produce black or brown dung while most birds produce white dung? Are there exceptions to this?

robboy

I've seen what buzzards and crows leave behind, and believe me, it isn't white. Must be the meat in the diet. Jun 12 04, 3:37 PM

Baloo55th

Some mice in one of my outbuildings ate a quantity of putty. The colour of their droppings changed from black to nearly white as it went through. Odd, but true... Jun 12 04, 4:17 PM

yeaux

The brown in mammals feces is caused by a breakdown of Red Cell hemoglobin called bilirubin. Bilirubin is inttroduced into the bowel lumen for excretion via the biliary tract. When the biliary tract is totally occlude by stone or tumor, the feces turn white-a condition know as acholic stools. I think the stuff in birds' doo-doo is called guano. Jun 12 04, 5:18 PM

gmackematix

Interesting, especially that observaion about mice, Baloo. That process you described, yeaux, does explain why meat-eaters produce the brown stuff when eating meat, but not why it is brown when eating something without bilirubin such as fish. In addition, it still doesn't explain why rabbit and goat droppings, for example, are black, while those of pigeons are white (see Nelson's Column). There must be more to this than hopefully doesn't meet the eye! By the way, guano, a Spanish word from the Quechua for dung, is just a name given to seagull dung when sold as a fertiliser (especially on the Pacific island of Nauru where it is the basis of their economy). Jun 12 04, 8:44 PM

satguru

I can add a few details from school here. Birds differ from mammals in that they share a single excretory exit, called the cloaca. This produces both urine and faeces in one drop, normally the white is urine and the black or dark islands are the faeces. But geese and ducks produce green or almost black droppings, and all the pigeons in London regularly make purple ones from eating berries. Because the main constituent of most bird droppings is the white part, and it's a bright shade, it gives the impression from a distance of a white covering eg on Nelson's column, but close up you'll see a marbled effect with the number two part. Jun 15 04, 4:47 PM

TheAlphaWolf

yep, and hawks and owls don't poop black because they don't "poop" at all, they just pee! instead the solid material goes up through the mouth. I've seen both owl and hawk pellets. both had little rodent bones and skulls in there... very interesting indeed.... no, I didn't touch the pellet, I used a stick. Jun 15 04, 5:41 PM