Cessna 208 pilot reported engine cowling began to rise after takeoff. Pilot returned to departure airport and found the cowling had not been properly latched.

Narrative

Recently I was conducting a flight in a Caravan. The preflight was done; and I was loading passengers through the entry door while a ramp member pulled the heater hose from the right side cowling. He did this; and I visually checked the cowling and openings of the aircraft. Seeing no issues; I proceeded with the flight. I taxied out; did my runup; and was cleared for takeoff. After rotation and takeoff while positively airborne without the opportunity to abort the takeoff on the runway; the copilot side engine cowling began to rise. There was no adverse effect to the controllability of the aircraft. I realized I didn't touch and pull on the cowling latches before takeoff. They had appeared closed. I requested and received a clearance to land back at ZZZ. I landed with no problems and taxied back. I conducted a check of the cowling and secured the latches positively. No adverse effects or damage were noted with the cowling working perfectly as required. I then consulted with my Chief Pilot; who had watched my takeoff; about the situation. He advised nothing further was required from me.