Final answer:
The student's question is about statistical analysis of sheep population dynamics in Tasmania and is answered by explaining how mortality rate data can be used to understand population trends and life expectancy, with an example using Dall Mountain Sheep.
Step-by-step explanation:
The question refers to the analysis of the sheep population size over time in Tasmania, which can be inferred using statistical methods such as a life table and the mark and recapture technique. Figure 45.4 suggests that mark and recapture is a method used to measure the population size of mobile animals like bighorn sheep, applied to similar cases in Tasmania. The life table for Dall Mountain Sheep provides an example of how mortality rates are calculated, with a specific instance demonstrating that between ages three and four, 12 individuals die out of the 776 remaining, yielding a mortality rate per thousand by the formula mortality rate = (12 × 1000) / 776 = 15.5.
Furthermore, the life table data can reveal important trends such as higher mortality rates at certain life stages, providing insights into the average life expectancy within the population. For instance, the data points to a significant death rate in sheep aged six months to a year and again from 8 to 12 years old. Once a sheep reaches one year of age, it is expected to live on average an additional 7.7 years. Such data are crucial for understanding population dynamics and for conservation efforts.
The mortality rate data and the relationship with life expectancy offer vital information for biologists and ecologists to understand the population trends of species such as sheep in Tasmania. The data also support broader ecological concepts, such as the inverse relationship between population density and body size shown in Figure 1 for Australian mammals, which is typically observed in ecological populations and is related to resource availability and species survival strategies.