Final answer:
The most likely factor that would allow for an increase in the monkey population, given the options, would be increasing their food supply or reducing predation risk, neither of which are provided as options. Instead, real-world examples indicate that changes in habitat quality or predator populations can have significant impacts on species like monkeys.
Step-by-step explanation:
The question asks which limiting factor would allow for an increase in the monkey population in the ecosystem depicted. Limiting factors are environmental factors that limit the population growth rate, including low food supply and lack of space. The given options are: Decrease in vegetation, hiding behaviors of monkeys, increased birth rate of leopards, and decreased death rate of zebras. An increased birth rate of leopards would likely result in a higher predation pressure on monkeys, leading to a decrease, not an increase, in the monkey population. Similarly, a decreased death rate of zebras would not directly affect monkey populations. Therefore, the most plausible answer is not explicitly stated among the options but would be an increase in food availability or a reduction in predation risk specific to monkeys.