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River Science: Wildlife

Although none of our students are specifically studying the river ecology on this Voyage of Discovery, the Half Moon still provides us with an excellent vantage point to examine the flora and fauna of the Hudson River Valley.

This rare October voyage places us on the river right in the middle of many species' migration patterns; the skies above us often reverberate with the honking of Canadian geese flying south for the winter.

While the birds in the above photo are also heading south, they're actually a flock of cormorants, flying mere inches above Haverstraw Bay. These birds use these flight patterns to corral schools of fish just below the surface before diving in to catch their meal.

The stowaway on Bennett's knee is another traveler, one likely feeling sluggish due to the cool autumn temperatures. While it clearly appears to be a monarch butterfly, we didn't have the opportunity to definitively identify its species -- a species of moth closely mimics these butterflies. Shortly after we took these photos, our winged passenger took off again, and was last seen flitting downriver.

During research layovers, we take groups of students out on Zodiac expeditions to explore the nearby wetlands and search for specimens of native plant and animal life to study.

In the fresh water upriver, we mainly encountered large clumps of eel grass, which dies off at this point in the season and actually poses a minor navigational hazard -- unless we closely monitor our systems the floating grass can clog the water intakes for our engine.

As we moved into a brackish environment, we also encountered zebra mussels -- a highly invasive species -- living on the Newburgh docks.

By the time we launched our Zodiac expeditions to the Brooklyn waterline around Grave's End Bay, we were exploring an entirely marine ecology.

Our first expedition returned with this dead, though largely intact, horseshoe crab.

Our last expedition of the day scouted out a little-used creek that led almost all the way to Coney Island. Here, in shallow waters, we discovered sheets of sulfur-producing bacteria (which we chose not to take back with us to the ship).

It was our mid-day expeditions to a nearby beach that produced a bonanza of specimens, including these shells. A few deserve special attention...

Bennett found this intact crab shell. This shell was abandoned during a molt, so the crab that original owned it may well still be scuttling around in the harbor.

Bennett and Evi also showed off the razor clam (so called because its shell resembles an old-fashioned folding razor) they discovered.

Mouse over to see the flip side.
A brightly-colored shell fragment.

We only found a fragment of this shell, but Dr. Jacobs was taken with its colors. Because it's broken, it also gives us an opportunity to get an idea of its interior structure.

Many of the shells we discovered were completely covered in small mussels -- and quite often those mussels had piggybackers of their own, sometimes to the extent that the original shape of the host shell had become obscured.

Several of these shells were still occupied by living creatures -- not their original owners, but by hermit crabs. This crab's claws form an almost perfectly shaped "door" to close the entrance to its adopted home.

Mouse over for a closer look at the stowaway.
A tiny hermit crab.

As we examined this hermit crab, we noticed the tiny spiral shell inside it. Assuming the tiny shell to be that of a snail, we picked it up to take a look -- at which point the upset "snail" started waving its legs! The snail turned out to be yet another hermit crab taking shelter inside the protective shell of its larger kin.

As for real snails, we returned with at least a dozen of them, discovered crawling all over our sea lettuce collections.

We also found more than half a dozen of these crabs, which normally live under the sand at the water's edge.

(The tiny fellow is the stowaway hermit crab above, which spent most of the morning running laps around its bucket.)

We placed many of our specimens in the ship's aquarium for the students to observe, particularly the snails, who do their part to keep the tank clean. The crabs mostly stayed in their buckets during their time on board. (Crabs are voracious eaters, so if we place too many in the tank with other specimens, we may soon find the tank's population dropping rapidly.)

At the end of the voyage, our live marine specimens will be returned to the water as we found them.

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