Final answer:
Opossums on Sapelo Island produce smaller litters because they are more likely to live to an old age and they can allocate more resources and parental care to each individual offspring.
Step-by-step explanation:
Opossums on Sapelo Island produce smaller litters for several reasons. First, they are more likely to live to an old age, which means they have a longer lifespan to produce litters. Second, producing smaller litters allows them to allocate more resources and parental care to each individual offspring, increasing their chances of survival. Both of these statements have explanatory power in understanding why opossums on Sapelo Island have smaller litters.