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Feeding Fiona: The science behind milking a hippo

Posted March 18

— Pressing her face up against Bibi's suitcase-leather skin from outside the safety of a barrier, Jessye Wojtusik reached up and under the animal, awkwardly trying to access her udders. Never could she have imagined that her post-doctoral research would find her milking a 3,371-pound hippo.

But with the birth of Fiona, the Cincinnati Zoo & Botanical Gardens' beloved baby hippo, convention has been in short supply. After all, there isn't a handbook for hand-rearing a hippo.

There will be, though, thanks to the efforts of people like Wojtusik, a postdoctoral researcher/scientist at the zoo's Center for Conservation and Research of Endangered Wildlife (CREW), Fiona's keepers, the zoo's nutritionist and a scientist at the "milk bank" at Smithsonian's National Zoo.

Before Fiona came into the world six weeks early and only about half as big as she should have been, zoo staff were getting ready for her care. A birth plan is standard when a zoo baby is on the way. Much of that went out the window when newborn Fiona was too small and too weak to nurse from her mother.

Staff members had to take quick action. They reached out to contacts at other zoos to see if anyone had hand-reared a hippo. No one had.

Getting Fiona's strength up was critical, and that meant making sure she had the right nutrients. Here, the zoo had an unusual advantage: They figured they just might be able to milk her mother. Keepers had already trained Bibi to go into a small enclosure and "lean in" for an ultrasound. That was a breakthrough in itself. Wojtusik captured what is believed to be the first-ever ultrasound image of a Nile hippo fetus.

Were it not for that, it would have been difficult, if not impossible, to train a mother hippo for milking in short order. But from Bibi's perspective, being milked wasn't all that different an experience from getting an ultrasound.

Picture it: One keeper stood to Bibi's side, holding a ball on a stick. When the hippo leaned far enough to touch it — in other words, the desired behavior — a keeper in front gave her treats like beet pulp, apples and romaine lettuce.

"Bibi's really food motivated," Wojtusik said. "She'll do pretty much anything for a treat."

She's also surprisingly cooperative, for a hippo. "I don't think it would have been possible with very many hippos," she said. "I think if we tried (something like this) with Henry (Fiona's father) it would be a different story."

While Bibi was busy eating, Wojtusik, and later keepers, could milk her. Growing up on a farm, Wojtusik occasionally milked pigs and cows. (Hippo udders, she found out, are shaped more like pig ones.) The gentle squeezing motion wasn't that different with Bibi, once Wojtusik had succeeded at the reaching part.

Africa keeper Wendy Rice is pretty sure no zoo hippo has voluntarily allowed herself to be milked before. Keepers milked Bibi twice a day most days until she stopped lactating. They didn't get a huge amount of milk, certainly not enough to sustain a baby hippo, but what they did get was significant for more than one reason.

First, it was, simply put, good for Fiona.

"It's really important that newborns get the 'first milk,' the colostrum," Wojtusik said. "It helps their immune system and provides them the antibodies they need."

Not all of Bibi's milk went to Fiona. Zoo staff sent just a little of it to Washington, D.C., to a scientist named Michael Power at the Smithsonian National Zoo. He runs the milk repository at the Smithsonian Conservation Biology Institute's Conservation Ecology Center.

Yes, there's a national milk bank, with no fewer than 15,000 milk samples from at least 130 different mammal species.

Power's goal is to collect multiple milk samples from multiple females of a species. He wants to find out how that milk changes over time, and if there are differences between individuals of a species. In other words, is gorilla milk gorilla milk, or is each individual animal different?

He already knows there are differences between species, in things like sugar and fat content. He can tell, for example, the difference between human and primate milk, or gorilla milk and orangutan milk, just by the microbes in it.

But until he got Bibi's milk (samples from days 1, 3, 8 and 9), he'd never seen hippo milk before. Turns out it's on the high side for protein, relatively low in fat and sugar. (Giant anteater milk is the closest thing to it that he's seen.)

Interesting to science, sure. But this particular case was about more than advancing our understanding of animal physiology. Back at the Cincinnati Zoo, curator of nutrition Barbara Henry waited for the results.

Barbara Henry is one of only a small number of zoo nutritionists in North America. In a case like Fiona's, she works with a company that makes formulas to resemble different animals' milk, based on scientific research. But Barbara Henry doesn't just take their word for it: She does her due diligence and checks their research. In this case, all they had to go on was a less-than-specific research paper from 1959. That wasn't enough evidence to gamble with Fiona's health.

There's a lot of trial and error in getting a formula right, anyway. Keepers and vets looked at everything from her weight gain (or lack thereof) to her energy level to her blood work to her poo, meeting multiple times a day to determine what she might be lacking, and how they might change her food to fix that.

"You have all these pieces to the puzzle and you have to figure out how to put the puzzle together," Barbara Henry said. "And the picture may change the next day."

Power's analysis gave them a clearer picture to start with, the knowledge of exactly what she would have been getting had she been able to nurse. (He found that the 1959 report overestimated the fat content.) That's good for Fiona, and for future Fionas. Barbara Henry said she and other zoo staffers will put together a handbook in case another zoo finds itself hand raising a hippo.

It's been a learning curve, but one that all involved were happy to help surmount. For scientists like Power and Wojtusik who spend most of their time on lab work and writing, it was rewarding to work on something with a practical application, particularly when it meant helping a much-loved baby animal.

And it's not every day that you get to milk a hippo.

"But I'm super excited that I did get the opportunity," Wojtusik said. "I've always loved hippos, so this has been kind of a dream for me."

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