How can you tell when raw yams or raw sweet potatoes have gone bad?

If it's sprouting, it's probably gone bad. Other signs are squishy-ness, black marks, the skin 'rippling'/wrinkling, bruises, and of course bad smell.

If you're still unsure, try slicing it open and if it's discoloured or smells bad inside.

If you're still not sure, taste a little bit of it.

I'd assume they're bad -they don't last more than a month, less if stored improperly. They should be stored in a dark, cool, dry place (but NOT the fridge, fridge will cause the core to go funky) and not washed until right before you're ready to cook.

Sweet Potato Gone Bad

Flooring should be flat, not wire bottom as their feet are soft and can hurt them (swollen feet). Buy a corroplast or corrugated plastic board and cut it into half a box (the bottom part so there is 2-3 inches on the sides to catch the poo). Inside the box, place a towel and then on top place a cloth made of polar fleece. The fleece will let the urine go down into the towel and keep them dry. The fleece also makes cleaning their poo easy (they poo like crazy) as the poo never sticks to the fleece. Another name of polar fleece is polyester fleece. These are really cheap (i got mine for USD 2.50 ) GP are never to be leashed. They are not dogs and it will damage their spine. Make sure place is clean, dry, free from moisture and predators (dogs, cats, large birds). They get stressed easily. You will also need to make a litter box and train them to use it to minimize peeings all over the cage. To train them, always put some poo in the litter box after you clean the pen and put the food bowls in the litter box (they poo and pee where they eat). Don't feed them leaves. They like cucumbers. Occasional fruit is ok but not the seeds which can be poisonous like apple seeds. Don't forget some toys. They get bored easily. Cage should be at least 10 square feet. Good luck.