Southern California resident here. I have strawberry seedlings and would like to transplant them outside. How old should they be to avoid being eaten by squirrels? I've had days-old seedlings get their crowns crunched off by these little devils.
A reliable & practical thing to do is place curved pieces of medium mesh hardware screen which extend lengthwise over several of your seedlings for each section of screen, pressing the edges of the screen 6-8cm into the soil along both sides of your seedlings! Maybe could start by putting a few seedlings and a couple sections of screen to see if your Garden Guests are also tremendous little diggers! If they aren't great diggers, good, but if they are, then may have to press the hardware screen a little deeper into the soil! Be very careful of the edges of the hardware screen when handling it, but the edges are also a deterrent to little Guest diggers! And be sure to close off row ending sections, by on the end bending enough screen down to also press into the soil to keep them from coming in each end!
Such hardware screen 'canopies' are fairly durable, stack ok, & are reuseable, and if a bit wider and taller, can also offer protection to larger strawberry plants from other types of guests. And can be easily weighted down if necessary!
There are other methods, but covering strawberry seedlings in this way is effective & reliable, and fairly straightforward! If your Guests, or other visitors, decide in future to try enjoy dining on your larger strawberry plants, it can also be effective. And it allows good airflow and sunlight for your Strawberries!