Sex can be an acrobatic venture for any species, but when your mate weighs around 40 tons ... well, things get even trickier. For gray whales, doing the deed means performing impressive underwater gymnastics – just watch this rare clip from California's Palos Verdes.  

The rolling behaviour you see here is a courtship ritual, a way for the male to tell the female he is fit, healthy and hot to trot. Even for whale biologist Dr Carrie Newell, seeing this romantic rendezvous in action is remarkable.

"It's just beautiful," she says. "She rolls to let him know his efforts are noticed. Gray whales are quite amorous and like to practice; they do not fight for affections like other whales. I've seen mating triads – two males on a female taking turns."

Whether or not this pair actually mated is unclear, but the intention was there. 

"These grays are very fit," explains Newell. "They are well filled out, and definitely move to each other ... it definitely looks a likely possibility that mating occurred."

Gestation lasts 12-13 months for the large whales, so we won't see evidence of the pair's potential success for some time. A calf can weigh up to 1,500 pounds (680 kg) at birth and is typically about 15 feet (4.5 m) long – and the supersized baby will bulk up on milk that’s 53% fat and the consistency of runny cheese. Yum.

We'll leave you with this fun fact: a gray whale's penis (or "Pink Floyd", as Newell likes to call it) can reach six feet (2m) in length – that's 15% of its total body length!