"that's mine!"

[J0eypie]

Our 2.5 year old DS has entered that lovely phase of declaring "that's mine!" if another child so much as looks at one of his toys (or in fact anything he happens to be playing with e.g. at play group etc.)
Any tips on how to nip this in the bud, or at least deal with it properly while it lasts?
I know it's a normal developmental thing but I really don't like it!

We're right in the middle of this too. It's not just toys though, it's pretty much anything, including the poor cat and the sofa. I don't imagine there's anything to be done other than waiting it out - that's my strategy for everything! If it is her thing, but someone else has it, I say yes it's yours but xx is borrowing it. If it's not hers, I just point out who's it is and move on.
It is annoying, saw a friend recently with a DS of the same age, and it was like that scene with the seagulls in Finding Nemo. Mine! Mine! Mine!

It's very typical development which will stop naturally. However you can model behaviour by playing turn taking games. When he's play with a car take it off him saying mummy's turn. Play with it for a few seconds then give it back saying DS turn. Do it repeatedly in different situations and with different toys. But not all the time. Then extend the game to 3 of you. If you have a friend to play initiate turn taking games eg pouring sand rolling ball etc. say DS turn then give his friend the spade and say Fred's turn. It models sharing and that you get the object back.

My son was still doing this at 3+

He is still particularly possessive about special toys. Woe betide anyone who wants to use his scooter. I always give him a choice and ask him if he wants to share rather than forcing it. I think he should be allowed to choose who he shares with.

Thanks for the replies all. Some useful advice here. As with most toddler stuff it's about being consistent until they get the message I guess. And hoping that is sooner rather than later!

Ha ha bless her, they remember everything!