AMSTERDAM, NETHERLANDS — Tanja, an overprotective hippo mother, smothers her babies with so much love they die.

Zookeepers at the Artis Zoo have put the 3-ton hippopotamus on birth control so she and her mate, Joop, can't produce more offspring.

Only 5 of Tanja's 15 babies have survived her care.

So far, only five of Tanja's 15 babies have survived her care.

Tanja accidentally killed the others by hugging them so hard they suffocated or by refusing to let them be fed by zookeepers for so long they starved, zoologist Dick Dekker said.

Last week, Tanja was given an injectable contraceptive administered with a blow dart.

Zookeepers will let Tanja reunite with Joop this week.

"They'll be happy to see each other," Dekker said. "We just hope there won't be another little one on the way."