Squirrel
Food
Good Food
If you don't have squirrel food, you can usually buy it from the Arosa train station. If they have run out there are supermarkets on the main street towards the trail. Note that most shops are closed on Sundays. Although there is a Spar at a gas station (in the opposite direction, on the west side of the lake), I'm just not sure if it sells nuts. For the squirrels get hazelnuts, walnuts or pecans (unsalted). Anything in the shell is better for their teeth (as they never stop growing). They will also eat fruit like apples or grapes (they know not to eat the skin) and vegetables sometimes, they just prefer nuts.
Aflatoxin free peanuts are fine to give the birds, but...
Food Warnings
Peanuts should not be given to squirrels! Not even the aflatoxin free ones and certainly not raw peanuts (that's the ones in the shell) as they can contain a toxic fungus that is lethal to squirrels. Also definitely don't give them any sugary, processed or salty foods, no dried fruits (like raisins), wheat, dried maize, bitter almonds, Brazil nuts or peas. Almonds (sweet almonds) are actually OK to give squirrels in small amounts (they contain cyanide but not too much). If you're confused or concerned, just stick to hazelnuts and walnuts.
Tip
If you give them large chunks of loose nuts they will likely be triggered into running away to bury it (caching) for later. If you want them to stick around for a photo, break the nuts up into smaller pieces. This is why I prefer walnuts and pecans over hazelnuts (the latter is harder to break).