Question

Every year, Christmas Island in the Pacific is overrun with over 120 million red crabs (Gecarcoidea natalis) moving across land between their breeding ground and habitat and towards the water to spawn. Watch the following video: Red Crab Migration on Christmas Island (Links to an external site.)Links to an external site.

Write and explain at least two alternate hypotheses for each of the following questions, and propose research to test your hypothesis. For your proposed research for each section, explain whether your work will be experimental, correlational, or conceptual and be sure to note what the strengths and weaknesses of your approach might be. Make sure that you explain you logic well.

a. What might be the adaptive benefits of everyone migrating at the same time? (think about what happens to individuals that miss the event, or travel separately)

b. In this species males leave their burrows and arrive at the beach a couple of days before the females. Why might they do this?

c. How do they coordinate such that they migrate at the same time? (what type of cues might say it is time to leave, what physiological mechanisms might be at play?)

d. How do the crabs know where to go? (think about navigation and whether components might be learned or inherited).

Answer 1

A. Anti Predator is main benefit of everyone migrating at the same time, traveling separately would increase their relative predation risk

B. Males reach coast faster to dig burrows for females to mate and males fight each other for burrow possession. After mating males move to forest to help females in hatching thier eggs.

C. Red crabs must keep their bodies moist, so they all wait for the rainy season to migrate and breed, the timing of the migration breeding sequence is also linked to the phases of the moon.