A reader writes:
I'm no biologist, but I doubt those frogs are actually getting it on. Frog mating doesn't involve penetration and takes place in bodies of water - "froggy style" - rather than face to face. This photo is probably just tickling our anthropomorphic whimsy.
An expert enlightens us:
Those frogs aren't mating (or, at most, one of them is, and no reproduction is going to happen). Mating in frogs is called amplexus.
The male climbs atop the back of the female, grasping her with his forelimbs, either just behind her forelimbs (axillary amplexus) or around the waist (inguinal amplexus). Amplexus may begin on land, but is usually completed in water, since the eggs must be in a moist environment. Typically, the male and female shed gametes into the water, and fertilization is external.
Males of a number of species frogs and toads have been known to get overexcited, and amplex inappropriate objects (other species, empty cans, etc.), or, at times, multiple males will attempt to amplex the same female, and wind up amplexing each other in a sort of a ball.
The picture you show is something of this sort. Amplexus resulting in actual mating (i.e. shedding of gametes) doesn't occur belly to belly. If the lower animal is a female, she might be able to right herself (although it can be hard to make a male let go), and then a regular amplexus, with gamete shedding, could take place (they'll also have to move to the water; although I can't identify the exact species, the frogs in the photo are a species of the genus Rana, which lay their eggs in water). If you google-image "amplexus", you'll get lots of pictures of frogs and toads in amplexus.
I don't often say this, but trust me on this: I'm a herpetologist.
Another raises a disturbing possibility:
I'm in herpetology and actually study the effects of development (including roads) on amphibians. I'm not personally aware of a Ranid frog in that region of France (or anywhere) that mates in face-to-face amplexus. So I thought you should know that you most likely treated us all to some animal necrophila.