By Kate Jirik, Birch Aquarium naturalist and educator
Thursday, August 22nd
It’s 9:30 AM, and I am joining a very special Birch Aquarium animal for breakfast. On August 14th, a chambered nautilus (Nautilus belauensis) hatched for the first time in the aquarium’s history. Few aquariums, worldwide, have been able to hatch one of these sensitive nautilus eggs.
Today is an important milestone for the newborn: it has been eating for one week.
Behind-the-scenes in Birch Aquarium’s food preparation kitchen, I am welcomed by smells of frozen fish and squid. The nautilus’ primary caretaker, Birch Aquarium intern Alex Frolova, is busy preparing the nautilus’ morning meal. “We’re feeding the nautilus twice a day. It is not known what baby nautiluses eat in the wild, so we’re feeding a variety of foods to meet his dietary needs.”
No larger than a quarter, the baby nautilus is too small to know whether it is male or female–but Alex finds that calling the nautilus “he” comes more natually than “it”. She pulls a large knife out of a drawer and–as if mincing a clove of garlic–chops bits of krill, shrimp, clam, and squid tentacles into tiny pieces. Cut a grain of rice in half, that’s how small we’re talking.
We walk down a long, narrow corridor carrying the seafood delicacies. The low humming of water pumps ushers us to the tropical tanks, where chambered nautilus and other Indo-Pacific animals are housed.
Alex begins removing plastic panels that cover the top and sides of the hatchling’s tank. These opaque panels keep the tank dark to mimic light conditions that nautiluses experience in the ocean, where they live on reefs between 300 and 1,000 feet. Panels also prevent the hatchling from being startled when people walk by. In this moment, though, removing the panels seems like an unveiling.
“He is usually sitting on the bottom,” Alex says, setting the front panel aside. Sure enough, the nautilus is resting on the bottom. Perhaps dazed by the light, the hatchling whirls around a few times like a coin spinning on its side.
Next, Alex pours krill juices into the tank. She explains that juices help to prime the nautilus’ sense of smell and alert him that food is coming. A plume of greasy krill oil sinks to the bottom. To my surprise, the nautilus jerks sideways and within three seconds, rockets from the bottom of the tank to the surface! Alex has the nautilus’ attention.
Time to load the feeding pole. Basically, it’s a stick with a rigid piece of fishing line on the end. Spearing a tiny piece of food on the fishing line allows Alex to hold it in front of the nautilus’ mouth. Reaching into the tank, Alex cradles the nautilus between three fingers of her left hand while positioning the feeding pole with her right. “It’s a lot like feeding a baby bird. I place the food directly in front of his mouth, and he just opens wide and bites at it.”
Understanding the nautilus’ behavior requires attentiveness and patience. For example, the first time Alex fed the hatchling, it took 1 ½ hours! Seven days later, Alex is pleased that the nautilus is feeding well.
She gently releases the nautilus’ shell. The delicate animal wobbles slightly, but hovers and clings to the food on its own. If all goes well, the nautilus will continue to eat regularly. The aquarists hope that in the weeks ahead the hatchling will also begin searching for food. Right now, they’re not taking any chances.
After a couple of minutes, the nautilus loses its grip and sinks to the bottom. Alex re-evaluates her strategy. “I think it’s getting easier for me just to hand feed him.” She goes on to explain how she has been trying different methods: holding vs. not holding the shell, feeding with the pole vs. her hand. She picks up a piece of clam and places it in front of the nautilus’ mouth. “You’ve got to hold onto it, buddy,” Alex says, encouragingly. I find that I’m right there with her, rooting the nautilus on.
This nautilus will need cheering if experiences of other aquariums provide insight into what to expect. For reasons not understood, nautilus that hatch in captivity do not typically live longer than a year. (More on this in a forthcoming post.) Right now, the focus is on little successes–a week, a day, or even a meal at a time.
This has been a successful breakfast. The nautilus ate three pieces of clam. “So far, he seems to prefer clam to the squid tentacles, perhaps because it’s less rubbery, less tough.”
There you go…the chambered nautilus equivalent of mashed banana.