The photograph above is a beautiful illustration of the coloration that gives the Northern red-legged frog (Rana aurora), its common name, though the red’s shade is a bit harsh due to drying skin. The photo also shows the frogs in amplexus, which is the posture these animals assume in breeding, with the male on the female’s back, the elongated nuptial pads on his thumbs planted in her armpits for grip. The male aurora is unusually aggressive, as frogs go, perhaps because their breeding season is relatively short, the females only staying in the still water for a couple weeks. The males are so eager they may mount other males (one mounted an apple), the accosted fellow making release calls to his overanxious competitor.

These animals aren’t generally active in water with temperatures below 50 degrees F, but during breeding season they’ll mate in water above 43, perhaps because of their elevated hormonal levels during breeding. (These temperatures are unusually cold for frogs, but aurora is acclimated to the cool Northwest.) The males arrive at the breeding wetland before the females, and stake out a territory in the deeper water. They begin vocalizing a week after arriving, the mating call a low, soft uh, uh, uh, uh, uh. Some females reach the breeding ground before they’re ovulating, and stay in the shallow water until they’re gravid. When a female is attracted to a male’s call, she welcomes amplexus, and he fertilizes her eggs, perhaps even helping her squeeze them out as well. If a female has an unwanted amplexus forced upon her by an aggressive male, she will use release calls, abdominal vibrations, and rolling over to get the male to release her, which can take as long as 15 minutes. If these entreaties fail she’ll extend her back legs, stretch out her arms, and stiffen her body, while rolling onto her side. (This maneuver is more effective in the water than on land.)

After Maggie Rudy found the pictured pair in amplexus, two other pair were found in identical circumstances minutes later: day light, on the warm side (50 F), and though it had been raining for several days, that day (January 25) had been fair to partly cloudy. Dry to the touch, at first we thought the frogs had simply been stranded; morning arriving to find them at highway’s edge, the female exhausted from carrying the male, then doing her best to dislodge him, with no luck, and they spent the day in that posture, drying out, in trouble. This supposition had all perhaps been accurate, except their pose wasn’t from drying out, it was her last ditch effort to get him off her back. (As soon as they were in the bucket, dripped with water and wet leaves, they came to life.) -- Thanks to Shashank Sharma, and his fine article.