Trainers Trading Horses In Claimers

[makingit]

Yonkers Race 1 Laterza and Stratton traded horses (Claims).  Does that happen a lot in the same race? I know in the course of a night it happens a lot but I don't see it much in the same race.  Second question, did they know before the race that their horses were claimed? Or did one see the other claim his horse and get angry so put in a claim on the other one's horse as revenge?

[Dingus]

Some tracks require all claims to be made before the 1st race.  Others need the claim submitted at least 30 minutes before the race you want to put the claim in for.
A  lot of the horsemen let the other trainer know they are putting in a claim as a matter of courtesy.