ATR-72 Captain reported receiving a master caution alert for right engine low oil pressure on departure. The flight was able to land safely at the departure airport.

Narrative

During the climb; at 400 feet; the flight crew received a Master Caution Alert for a Right Engine Low Oil pressure. The right engine oil pressure was displayed with the actual pressure in the Amber Caution Range. There were several noticeable fluctuations from the bottom of the oil pressure Green band to the lower side of the Amber Caution Range. Dispatch was notified and an Amendment was given for an air return. An [request for priority handling was made] with ATC. The Flight Attendant (FA) was given the brief and the passengers were notified. ZZZ operations were notified as well. A normal landing was made at the aircraft was parked at the gate. A logbook entry was made. The mechanic who arrived at the aircraft; found the actual oil level was low and needed an additional 3.5 quarts of oil. The oil filter bypass; Red pin was popped as well. Cause - The lack of the proper oil quantity caused a Right Engine Low Oil pressure Alert. There was also a lack of monitoring and oil servicing by Maintenance prior to the event. Suggestions - There must be more over sight on Maintenance to ensure that the oil is serviced and checked more frequently. The Captain on this flight has experienced and documented at least four Low Oil Level Events in less than 1 year. There have been more documented low oil occurrences by other flight crews. It can not be stated any more clearly that this is a very dangerous and alarming trend that continues to the present day.