Question

Hunting is a major source of mortality for large frugivorous birds. These birds disperse the seeds of forest trees and are the primary contributors to forest regeneration. The graphs show the distribution of different age-classes of a frugivore-dispersed tree species at two isolated sites. 

• A. Hunting is higher at site (i) than at site (ii).
• B. Hunting is higher at site (ii) than at site (i).
• C. Hunting is similar at both sites.
• D. Frugivores are not hunted at either site.

Hint:

When interpreting ecological data, a high density of seedlings relative to adults often indicates predation or disturbance at earlier stages.

Answer 1

The Correct Option is B

The graphs show the distribution of different age-classes of frugivore-dispersed tree species at two isolated sites (i) and (ii). We can draw conclusions based on the data about tree seedling, sapling, and adult densities and their relationship to hunting.

Step 1: Analyze the graphs.
- At site (i), the density of seedlings is much higher than the density of saplings and adults, which suggests that seedling survival is low and possibly affected by a high level of predation or hunting pressure. - At site (ii), there is a more balanced distribution between the different age-classes, with relatively high densities of saplings and adults, suggesting a more stable or less disturbed environment, possibly due to lower hunting pressure.

Step 2: Evaluate the options.
- (A) Hunting is higher at site (i) than at site (ii): This seems unlikely, as site (i) has a much lower density of saplings and adults compared to site (ii). Higher hunting pressure would likely reduce the density of all age classes, not just the adults.
- (B) Hunting is higher at site (ii) than at site (i): This option is consistent with the data, as site (ii) shows a more balanced distribution of age-classes, suggesting that hunting may be less intense and that more adult individuals survive to disperse seeds. This would support a hypothesis of higher hunting pressure at site (i), where seedlings are less successful.
- (C) Hunting is similar at both sites: This is not consistent with the data because the densities of different age classes are more similar at site (ii), while site (i) shows a clear dominance of seedlings and very few adults. This suggests that the impact of hunting is not the same at both sites.
- (D) Frugivores are not hunted at either site: This is inconsistent with the patterns of seedling and sapling survival shown in the graphs. Hunting likely affects survival rates, especially in seedlings and saplings, making this option unlikely.

Step 3: Conclusion.
The most likely conclusion is that hunting is higher at site (ii) than at site (i), as site (ii) shows a more balanced distribution of age-classes, whereas site (i) shows low survival rates for saplings and adults.