In the spring months, when many wild animals set and breed, some cantons provide strict regulations for walking dogs in the forest to protect the wildlife.
Each canton sets the leash requirement for the breeding and setting season itself, the respective regulations can be found - depending on the canton - both in cantonal hunting and dog laws, as well as in the associated ordinances.
There you can also read exactly which wild animals you are allowed to feed and in which form.
More expertise for animal lovers:
https://www.susyutzinger.ch/en/Activities/SUSTInformationtothepublic