Final answer:
To determine if seasonal differences in the number of roadkill exist, the researcher should conduct an ANOVA test, which compares means of the animal death counts across spring, summer, fall, and winter.
Step-by-step explanation:
The most appropriate analysis for determining if the number of animals killed varies by season would be conducting an ANOVA (Analysis of Variance) test. This statistical method is designed to compare the means of three or more independent groups (in this case, the four seasons) to see if there is a statistically significant difference between them. Specifically, the researcher can perform an ANOVA to test the null hypothesis that there is no difference in the number of animals killed on the highway during spring, summer, fall, and winter.