I have got this extra credit question and I have no idea how to solve it. I will get five points of extra credit if I can answer it which will boost my grade to an A. So someone please help solve this problem. The question is written below:
1. You have been studying an herbivorous lizard species, desert iguana, and an herbivorous
turtle species, desert tortoise, at 10 sites in the Mojave Desert of Southern Nevada. An
older publication reported data on 50 study sites in Southeastern California showing the
following: at all 50 of their study sites, desert iguanas and desert tortoises predominantly
ate herbaceous species of grasses and forbs; in 48 sites, desert iguanas and desert
tortoises appeared to coexist; and finally, at the two sites where the lizards and tortoises
did not coexist, the lizards typically came to population sizes of 65 desert iguanas per
square kilometer. From data from your study, you found two results: the competition
coefficient for the effect of iguanas on tortoises appears to be 0.32, and when either
species (tortoises or iguanas) reaches a density of 300 (or more) individuals per square
mile, the other species always appears to be prevented from increasing regardless of its
population density.
At another study site in Southern California, a predator from the family Corvidae (the
common raven) is found in syntopy with desert tortoises only. Others have determined
that ravens require prey densities of desert tortoises in excess of 38 tortoises per square
kilometer before the raven population can increase. Your data on this system has allowed
you to determine that ravens can kill baby tortoises at a rate of 0.5 tortoises per raven
per year. The normal death rate of ravens is 0.1 raven per raven per year. Finally, you have
determined that the carrying capacity of desert tortoises in California is the same as that
in Nevada. Assume for the sake of analysis that the populations exactly obey Lotka-
Volterra equations. Show all of your work, but also summarize your answers in one sentence
for each question.
A. What population densities for desert iguanas and desert tortoises would you expect
in Nevada, if the other competitor were driven to extinction?
B. What are the predicted population densities of the two coexisting species when they
reach equilibrium population numbers?
C. What would happen if tortoises had a carrying capacity of 500?
D. Can tortoises coexist with ravens?
E. What is the carrying capacity of ravens when tortoises are not present?
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