[nverno]

Foraging enough mushrooms to provide any real sustenance sounds like a real challenge (except for fall in the northwest).

[bagels]

That is an understatement. Mushrooms are one of the least calorie dense foods. It'd take something like 20 lbs. of mushrooms to hit 2000 calories.

[swiftcoder]

On the flip side, they are absolute flavour bombs, and often on a budget you are short on flavour-enhancing ingredients.

Forage them (safely!) in the fall, dry them out (I stick them on a wire rack over a radiator for a few days), then into an airtight jar. Toss a few into soups/sauces the rest of the year.

[BigGreenJorts]

I'm assuming the mushrooms are for micronutrients not calories. A couple of cremini (just the mushroom I buy most and speak to) have all your copper needs for the day

[29athrowaway]

I have heard a dog can be used to find them more effectively, but they cannot tell if a mushroom is toxic.

[nverno]

It's not something I've ever seen, but I certainly believe it given their incredible noses. And of course pigs are often used for truffle hunting. If you are gathering mushrooms to eat, it's not too hard to learn which are toxic anyway.

Once you know where patches are (at least for mycorrhizal fungi which are some of the best) it is easy to go back and get them each year. But, it still takes time to find all the locations and there is competition from other foragers, humans as well as other animals.