How do you milk a go­rilla? Very care­fully

In­side Amer­ica’s largest stock­pile of ex­otic an­i­mal milks: It takes all kinds.

Tampa Bay Times - - Health & Science -

WASH­ING­TON — To milk an ape re­quires pa­tience and peanuts.

For­tu­nately, Na­tional Zoo pri­mate keeper Erin Stromberg has plenty of both as she ap­proaches Batang, a Bornean orang­utan, on a re­cent brisk morn­ing be­fore the gov­ern­ment shut­down.

Stromberg is there to re­trieve a breast milk sam­ple for the zoo’s ex­otic an­i­mal milk col­lec­tion, the largest U.S. re­pos­i­tory of its kind.

“Hello!” she calls, singsong, as the auburn-haired pri­mate presses her­self against the metal grate of her en­clo­sure. Batang’s mouth is open, her lower jaw pro­trud­ing; she knows what time it is. Stromberg hands her a peanut, then an­other, and 21-year-old Batang munches hap­pily as shells ac­cu­mu­late on the floor. Her son, a bounc­ing ball of fur named Redd, 2, clam­bers over his mother’s back to beg a treat for him­self.

“Hello, you go away,” the keeper says dis­mis­sively be­fore giv­ing him a nut. “Bye! See ya.”

She un­screws the cap of a small vial, then turns her at­ten­tion to her charge. But Batang ap­pears to have changed her mind, swing­ing away from the grate.

“You can do it,” Stromberg says, her voice low and sooth­ing. “You’ll be fine.”

Batang re­turns, slowly this time. She ac­cepts sev­eral more nuts from her keeper, then pushes her chest for­ward, fi­nally pre­sent­ing Stromberg with her breast.

“That’s good, that’s good.” Stromberg holds her vial below Batang’s nip­ple and tugs gen­tly un­til milk comes out. The orang­utan con­tin­ues to grab treats with one hand while grip­ping the side of the en­clo­sure with the other.

There is some­thing pow­er­fully fa­mil­iar about her wrin­kled knuck­les, op­pos­able thumbs, and the in­tent gaze of her deepset black eyes.

“Good, good girl,” Stromberg says.

After 15 min­utes, there are just a few drib­bles of milk in the vial. But Batang is look­ing antsy, and it’s im­por­tant to Stromberg that this ex­per­i­ment be en­tirely vol­un­tary. If the ape doesn’t feel like par­tic­i­pat­ing to­day, there’s al­ways next time. Batang has been do­nat­ing small amounts of her breast milk ev­ery week for the last two years.

Each vial goes up the hill to the zoo’s nu­tri­tion lab, where it is stored in a mas­sive deep freezer along­side sam­ples from hun­dreds of other species: ze­bra, go­rilla, black bear, African ele­phant, mar­moset, ar­madillo, two-toed sloth.

Milk, ex­plains Mike Power, the Smith­so­nian sci­en­tist who cu­rates this col­lec­tion, is mam­mals’ su­per­power. It’s full of nu­tri­tious fats and sug­ars that turn wob­bly, help­less new­borns into self-suf­fi­cient adults. It con­tains an­ti­bod­ies that in­crease in­fants’ chances of sur­vival and hor­mones that help them grow. This pow­er­ful bio­chem­i­cal con­coc­tion car­ries clues to an­i­mals’ evo­lu­tion­ary past and hints about how they live to­day. Un­der­stand­ing what it’s made of may be the key to se­cur­ing some species’ fu­tures.

Yet even though milk is (or was) pro­duced by all 6,495 mem­bers of the class Mam­malia, sci­en­tists rarely study the sub­stance ex­cept when it comes from cows, goats and hu­mans.

Power and his col­leagues aim to change that.

On the same morn­ing that Stromberg and Batang strug­gle with milk­ing, sci­en­tists in the zoo’s nu­tri­tion lab are pre­par­ing a vial of bot­tlenose dol­phin milk for anal­y­sis.

“It’s very high fat,” Power ex­plains, be­cause a new­born dol­phin’s first pri­or­ity is to quickly grow a blub­ber layer. “More like but­ter than milk.”

With a se­ries of in­stru­ments, the zoo sci­en­tists sep­a­rate each milk sam­ple into its com­po­nent parts. Their first ob­jec­tive is to de­ter­mine the ba­sic com­posi-

tion of milk from each species. Whereas dol­phins and other ma­rine mam­mals pro­duce milk that is as much as 60 per­cent fat, car­ni­vores like African li­ons give milk high in pro­tein. An­i­mals that sub­sist on car­bo­hy­dra­terich plants feed their young milk that’s full of sugar.

Though hu­mans eat plenty of meat, we fall into the lat­ter cat­e­gory, a sign of our mem­ber­ship in the mostly her­biv­o­rous pri­mate fam­ily. Our moth­ers’ milk is about 7 per­cent sugar, 1 per­cent pro­tein, 4 per­cent fat, and half a per­cent min­er­als. The re­main­der is wa­ter.

Even though Power has stud­ied milk from scores of species, the sub­stance still has the ca­pac­ity to sur­prise. When he col­lected his first sam­ples from nine-banded ar­madil­los, he was star­tled to dis­cover the an­i­mals’ milk was 11 per­cent pro­tein and as much as 3.6 per­cent min­er­als. These pro­por­tions seemed oddly high for a small in­sec­ti­vore — un­til he re­al­ized that in­fant ar­madil­los must build their bony cara­paces.

But milk com­po­si­tion isn’t only about a baby’s needs. Some­times, it’s a func­tion of what a mother can pro­vide.

“Peo­ple say that milk is the per­fect food,” Power says. “But re­ally, it’s a com­pro­mise.” Young an­i­mals would like the most nu­tri­ent-dense milk imag­in­able, but their moth­ers can only af­ford to de­vote so much en­ergy to nur­tur­ing a child.

Bi­ol­ogy dic­tates how long a species lac­tates. Hooded seals, who give birth on un­sta­ble pack ice, need their off­spring to grow up fast; after four days of nurs­ing, ba­bies dou­ble in size and are ready to be left on their own. Big­brained apes, on the other hand, de­velop slowly: Batang may nurse her son for seven years.

Stromberg and Power hope to track the way Batang’s milk changes through­out this pe­riod.

In the zoo’s pri­mate house, Batang and Redd are bliss­fully un­aware of their con­tri­bu­tions to mod­ern sci­ence. The in­fant orang­utan has hid­den in­side an over­turned laun­dry bas­ket and is scoot­ing around the floor — un­til his mother pulls him back.

Watch­ing from the other side of the glass, a group of chil­dren and their moth­ers laugh in recog­ni­tion. Milk is not the only thing we share.

DAVE JORGENSON | Wash­ing­ton Post

Pri­mate keeper Erin Stromberg milks 21-year-old Bornean orang­utan Batang at the Na­tional Zoo in Wash­ing­ton, D.C.

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