I share custody for my son, his mother claimed him last year. Can i claim him this year

Me and my ex(never married) have a 2 year old son. We share 50/50 time with him, and i pay for day care for him while hes with her. We live in different states and i do all the traveling to pick him up and drop off. Last year she claimed him on her taxes. Am i allowed with her permission to claim him this year on my taxes?