This activity is great fun and a good way for toddlers to learn about searching for mini beasts when the real thing feels a bit small and hard to spot, or if they are still learning to be gentle. It is also a handy activity to do in areas where you don’t have a lot of natural features, but plenty of surfaces to draw on.
Chalk is a great tool for playing outdoors because it washes off in the rain - or washing it off with a bucket of water and a sponge or paint brush becomes a great follow up activity! And it doesn’t do the wildlife any harm. Just make sure you have permission if you’re not in your own garden.