Hungry Hungry Hemigrapsus oregonensis

Climate change is a serious issue, affecting not only organisms in the terrestrial realm, but also those in marine environments. With increasing ocean acidification, and rising sea levels shifting marine biomes further up land, global biota will need to adapt to survive. Regular/normal food items and go-to/reg shelters may no longer be available to an organism, and they may face physical challenges when trying to find food (they go hungry) or when seeking shelter. An organism may also find themselves confronted with novel  situations such as increased competition – as habitats shift – or increased predation from perhaps novel predators; the need for an ability to adapt and innovate (problem solve) is a harsh reality facing many species.

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The weigh in.

My experiment aimed to test the effects of hunger on a type of coastal crab (Hemigrapsus oregonensis, in case you’re wondering), on preference choice, time to choose, as well as assess whether preference or time changes with differing environmental cues.

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And here we have our freaky-ass predator cue.

The crabs were collected from Tower Beach in Vancouver, BC on September 17. These little guys are easily found in the intertidal zone hiding under and between the many rocks that line the shore.

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My crabs only eat fresh, wild-caught organic cod from Whole Foods. They’re very particular.

On November 18 I collected my victims specimens from the water tank, 40 of them to be exact, with an equal number of males and females. I made sure that they had all their little legs (10!), and that they were all roughly 10.5mm in width. After doing so, I began my experiment! I started by starving half of them, and feeding the other half for 6 days. I then set up 4 treatment tanks. The control tank had shelter in one corner, and a cod meat snack in the other. The other three tanks had the same set up, but with the addition of a predator, a crab buddy, or both. I then tested the crabs by placing them in one of these tanks, and recording how long they took to make a choice (food or shelter), and which they chose.

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Everybody got a nice, cod-y treat after they graciously participated in the experiment

In the end, my results were just shy of statistical significance, but they did point towards some interesting stuff. When confronted with a predator, the hungry crabs exclusively chose food (even though that corner was less safe from the looming death in the centre of the tank). Also, when confronted with a crab buddy, the test crabs spent way less time waffling uncertainly in the middle of the tank – when food is scarce (as it will be, increasingly, if global warming has it’s way) gotta act quick to make sure Bob from next door doesn’t snatch up all the goods before you get a taste.


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