Introduction

[Guinea10]

Why do guinea pigs jump and squeak (short squeaks) when first meeting?

 

[Guinea10]

How can you tell a guinea pig introduction has been a success?

 

[Wiebke]

Why do guinea pigs jump and squeak (short squeaks) when first meeting?

Hi! Please take the time to read this guide here; it explains many of the social interactive and bonding behaviours. Your two piggies have like been everjoyed at having company, eapecially when they are still very young. Guinea pigs are group animals.
Illustrated Bonding / Dominance Behaviours And Dynamics

 

[Wiebke]

How can you tell a guinea pig introduction has been a success?

You may find this guide here helpful. It explains the whole bonding process from preparation until the end of the dominance phase about two weeks after the interaction, including a discussion of key behaviours for every phase. Without knowing any specific details, I can't help you any further.
Illustrated Bonding / Dominance Behaviours And Dynamics