Figure 8. A barplot showing the median change in body weight for each management treatment (kg)
We plotted the median change in body weight for adult caribou of each herd. All herds had an overall increase in body weight, but herds that received both management methods showed a much higher increase in body weight compared to the other herds. The predator control herds showed slightly less of an increase than the supplemental feeding herds. However, the predator control herds did have a fairly large increase in body weight which may indicate that predator control does allow caribou more food availability due to decreased predation pressure.
Figure 9. A barplot showing the median change in body weight for males and females
This shows the median change in body weight for males and females of all herds. Females gained more weight than males throughout the duration of the project. This is likely due to pregnancy and the fact that females had much lower body weight to begin with.
Figure 10. A barplot showing the average number of births for each management type.
Figure 11. A barplot showing the average number of calf deaths for each management type
These graphs show the number of births by management method and number of calf deaths by management method respectively. The herds that received both management tactics showed both the highest number of births and the highest calf survival. The herds that received predator control followed with the second highest number of births and calf survival. This is followed by the other two management methods. This indicates that both predator control and supplemental feeding showed an increased number of births and increased calf survival compared to the unmanaged herds. However, predator control was more effective than supplemental feeding since it had a lower number of calf deaths and higher number of births.
Figure 12. A barplot showing the average increase in population size for each management method
This graph shows the overall population increase for each herd. Both predator control and supplemental feeding resulted in population increase. However, predator control was more effective than supplemental feeding in this case, due to lower numbers of calf deaths and higher number of births. The herds that received both supplemental feeding and predator control had the highest increase in population.
Statistical Analysis
Table 3. An ANOVA table showing the output from the two-factor analysis of variance of supplemental feeding and predator control
After conducting the two-factor ANOVA, it was determined that predator control had a significant effect on population growth (p=0.0002). (Table 3). This indicates that there is a 0.02% probability of achieving our results due to random chance. Additionally, supplemental feeding also had a significant effect (p=0.0065) (Table 3). This means that there is a probability of 0.65% that we would achieve our results due to random chance. This means that both predator control and supplemental feeding have a significant impact on population growth. The interaction effect was not significant (p=0.5946) (Table 3). This indicates that the effect of either supplemental feeding or predator control does not depend on the presence of the other. The presence of predator control does not significantly impact the effects of supplemental feeding, and vice versa.
Table 4. The result of effect size statistics. Shows the population gains of supplemental feeding and predator control compared to the control for predetermined confidence levels
Effect size statistics were also conducted to determine the populations gains we could expect for predetermined levels of certainty. We compared supplemental feeding, predator control, and the combination of the two to the unmanaged control. This was determined for 95%, 75%, 50% and 25% confidence. Overall, a combination of management techniques will result in the largest gain of population compared to the control. By implementing both supplemental feeding and predator control, population is improved by at least 9.09% with 95% certainty. Predator control on its own improves population by at least 4.92% with 95% certainty. This is followed by supplemental feeding which will show smaller population gains for the same levels of certainty.
Conclusions
The results of this study could have important implications for how caribou are managed in order to grow the population and prevent extinction. Supplemental feeding resulted in the largest increase in body weight, but predator control ultimately resulted in higher population growth due to increased birth rate and calf survival. Overall we found the best results for all factors by implementing a combination of management methods. Combining management methods can provide a multifaceted approach to addressing threats to caribou.