My boy takes forever in the litter box

I got my first cats 7 years ago, two sisters. My son moved back with his cat in the spring so I have my first male cat. He is 11 months old now and about a month ago started spending a long, long time in his litter box, and going several times in the hour or so before bedtime.

Is this normal for male cats? He's a perfectly healthy, happy cat otherwise.