Father’s Day, which falls this year on Sunday, June 21, annually honors committed human dads. But seahorse fathers (above, a newborn hitches a ride on dad’s tail) might just blow those proud papas out of the water.

Seahorses are a type of fish in which the males actually get “pregnant.” The female seahorse deposits her eggs in the male’s specialized pouch, and the male carries up to 2,000 babies during its 10- to 25-day pregnancy.

“They’re fascinatingmales have more or less become females, [almost] transgendered,” said Mark Pagel, an evolutionary biologist at the University of Reading in the U.K. “They’re devoted fathers.”

In general throughout the animal kingdom, males leave parenting to the females, because males have more chances to reproduce and so can create many more offspring, Pagel said.

Pagel calls this

a “cruel bind [that] often favors men”–as soon as the female gets pregnant, the male just runs off.

U.S. comedian Chris Rock has said that “a man is only as faithful as his options,” he noted, and “that’s exactly what happens with animals.”

But there are exceptions, and “what’s wonderful,” he said, “is that the range goes all the way from males that simply provide sperm that are never seen or heard from again through to seahorses, where females just provide eggs and are never seen or heard from again.”

–Christine Dell’Amore
—Photograph by Paul Zahl, NGS Image Collection