If you're just tossing a few peanuts at squirrels now and again, by all means, carry on.
If, however, you are one of those people who likes to dump entire bags of peanuts on the ground in the park... well, first of all, stop doing that, but also, stop giving them peanuts (or sunflower seeds).
Peanuts and sunflower seeds do not have enough calcium or methionine for squirrels, and if those foods compose too much of their diet they will suffer from severe nutritional deficiencies.
I know that peanuts and sunflower seeds are cheaper than treenuts, but you shouldn't be dumping out so much food for the squirrels anyway, so spend the same amount and give them a little less of food that's better for them.
(Squirrels can actually eat quite a lot of food that's not nuts and acorns and seeds, like fruit, vegetables, insects, and even eggs, and they need to eat these other things for a nutritionally complete diet... but honestly, I'd rather tell people to stick to the most expensive option so they put out less of it. If you're not putting out so much food that huge populations of squirrels can gorge themselves sick and still leave more for the rats, then you'll find that even in an urban environment they can usually find their own supplies of all that other stuff.)
On a semi-related note, stop giving bread to ducks and other waterfowl. If you feel you must feed the ducks, give them a small amount of lettuce and vegetable trimmings (if you want to feed them scraps) or mealworms (if you don't mind making a stop by the pet store first). Ducks can also eat treenuts. And I suppose they can eat birdseed as well, but for the love of god, please do not dump 20 pounds of birdseed on the ground. Everybody needs to stop doing that.
If, however, you are one of those people who likes to dump entire bags of peanuts on the ground in the park... well, first of all, stop doing that, but also, stop giving them peanuts (or sunflower seeds).
Peanuts and sunflower seeds do not have enough calcium or methionine for squirrels, and if those foods compose too much of their diet they will suffer from severe nutritional deficiencies.
I know that peanuts and sunflower seeds are cheaper than treenuts, but you shouldn't be dumping out so much food for the squirrels anyway, so spend the same amount and give them a little less of food that's better for them.
(Squirrels can actually eat quite a lot of food that's not nuts and acorns and seeds, like fruit, vegetables, insects, and even eggs, and they need to eat these other things for a nutritionally complete diet... but honestly, I'd rather tell people to stick to the most expensive option so they put out less of it. If you're not putting out so much food that huge populations of squirrels can gorge themselves sick and still leave more for the rats, then you'll find that even in an urban environment they can usually find their own supplies of all that other stuff.)
On a semi-related note, stop giving bread to ducks and other waterfowl. If you feel you must feed the ducks, give them a small amount of lettuce and vegetable trimmings (if you want to feed them scraps) or mealworms (if you don't mind making a stop by the pet store first). Ducks can also eat treenuts. And I suppose they can eat birdseed as well, but for the love of god, please do not dump 20 pounds of birdseed on the ground. Everybody needs to stop doing that.