"Cute always comes first," said Chris Eastland, an artist and photographer from Brooklyn, N.Y., who joined forces with Andrew Bleiman of Chicago to create ZooBorns.com two years ago.
Their website delivers birth announcements from zoos and aquariums around the world, and gets about a million hits a month.
The men are publishing a pair of hardcover books through Simon & Schuster - "ZooBorns!" a 32-page children's book released last month, and a longer book for all ages also called "ZooBorns," out next week. The Association of Zoos and Aquariums gets 10 percent from sales.
"It's win, win, win for us," said Jill Nicoll, AZA's senior vice president of marketing.
The AZA benefits not just because of the royalties, but because promoting zoo babies is good for the conservation cause. "And, it's cute," she added.
Bleiman hasn't counted since summer, but as of then, they had featured around 600 births from 165 different species.
The great thing about animals, he said, is there are so many species. "There are tens of thousands, maybe hundreds of thousands of inspect species alone," he said. "There are plenty of species left to share."
So are some animal births too ugly to make the cute cut?
"We don't do a lot of insect larvae or spiders. Some organisms are too unpleasant to put on the site. There is nothing cute at all. A tiny fraction of the population would pine after a baby spider," Bleiman said.
They did post the July birth of a Caecilian, a legless amphibian, at the Tennessee Aquarium. "Some people found it creepy-crawly and others were fascinated," Bleiman said. "We show ugly birds all the time. Some think they are cute and others recoil."
They also hold off on some announcements, waiting for cuteness to settle in. Baby pandas are a good example, Eastland said. They are born pink, furless and no bigger than a stick of butter. By around 4 months, they are melting hearts.
"The all-time most popular post was the fennec fox," Eastland said. Radar Ears, from Seoul, is on the cover of one book and inside the other. A Bengal tiger made the cover of the children's book and its twin is inside.
Lions and tigers are always a big hit and Eastland likes polar bear and panda cubs because of the obvious message. But at ZooBorns, the success of any photo depends on how many w's people put at the end of the word aw, Eastman said.
"It's hard to engage people in the conservation side of this," Eastland said, "but it is our biggest message and we try to deliver it through adorableness."