In southern Africa, jackals are major predators of livestock on farms. As a control measure, farmers often kill jackals they find on their farms. Scientists Liaan Minnie and colleagues predicted that increased mortality of jackals would result in altered life history traits of this carnivore species. To test their predictions, they compared the number of pregnant female jackals in different age classes in populations that were hunted (on farms) to those that were not hunted (in conservation reserves). The resulting pattern shown in the first graph is the proportion of females that are pregnant in each age class. The scientists also collected demographic data to construct age structure diagrams (second graph) of jackals in (a) hunted populations (farms) and (b) populations that were not hunted (reserves). In the age structure diagram, males are plotted on the left, females are plotted on the right, and the median age class is denoted with hatched bars.
Source: Minnie, L., Gaylard, A., & Kerley, G. I. (2016). Compensatory life‐history responses of a mesopredator may undermine carnivore management efforts. Journal of Applied Ecology, 53(2), 379-387.
-Interpret the age structure diagram for jackals on farms compared to reserves.

Question

In southern Africa, jackals are major predators of livestock on farms. As a control measure, farmers often kill jackals they find on their farms. Scientists Liaan Minnie and colleagues predicted that increased mortality of jackals would result in altered life history traits of this carnivore species. To test their predictions, they compared the number of pregnant female jackals in different age classes in populations that were hunted (on farms) to those that were not hunted (in conservation reserves). The resulting pattern shown in the first graph is the proportion of females that are pregnant in each age class. The scientists also collected demographic data to construct age structure diagrams (second graph) of jackals in (a) hunted populations (farms) and (b) populations that were not hunted (reserves). In the age structure diagram, males are plotted on the left, females are plotted on the right, and the median age class is denoted with hatched bars.
  Source: Minnie, L., Gaylard, A., & Kerley, G. I. (2016). Compensatory life‐history responses of a mesopredator may undermine carnivore management efforts. Journal of Applied Ecology, 53(2), 379-387.
-Interpret the age structure diagram for jackals on farms compared to reserves.

Quizplus · Accepted Answer

Age structure diagrams showing a broader base indicate a higher proportion of younger individuals, suggesting potential population growth. If the diagram for jackals on farms shows a broader base compared to reserves, it implies that the jackal population on farms is likely to expand due to higher birth rates or survival rates of younger jackals, whereas the population in reserves may decline if it shows a narrower base, indicating fewer young individuals entering the population.

In Southern Africa, Jackals Are Major Predators of Livestock on Farms