The penguins are serial monogamists only, mating for the year and then breaking up to form new couples the next year

This immediately put me in mind of a part from a book I'm reading, Rice's Captain Sir Richard Francis Burton about the 19th century English scholar, adventurer, soldier and spy. Apparently this was on its way out when he was in India in the 1840s, but there was there something called "temporary marriage" which was just like the regular thing but per a written contract and limited in time (even as short as a week, the author mentions).