Your non-supervisory, peer co-workers cannot generally require any kind of communication from you other than that ultimately required by a supervisor, such as sharing lesson plans or cooperating in department meetings. Your relationship with your peers is, by definition, one of equals. However, there are laws that even regulate communication among equals. You may not harass a co-worker based on race, nationality, age, gender, religion, or disability. “It was a joke” is not considered a defense. You also should be very careful in comments that could be taken as sexually suggestive as they might be considered sexual harassment. Finally, you should be cautious in talking about a co-worker’s health, personal life, and business.
Of course, your peers have the same responsibilities to communicate to you professionally. If they fail to, the matter can be addressed to a supervisor. As a general rule, it is best to try talking to the peer who has created a concern first. This is not always possible of course, and in some situations, such as illegal harassment, cannot be required.