(Photo from list25, http://list25.com/the-25-grossest-jobs-you-could-have/)
By using formal comparative analysis of published road kill data, researchers have been able to see the effects diet and other factors have on the vehicle collision mortality of mammals.
While previous studies have focused on life history variables, the focal point for researchers at the University of California was a plethora of other variables.
The factors the researchers decided to study were diet, body mass, scavenging, flight initiation distance, maximum sprint speed, time of activity, brain mass, longevity, length of maternal care, length of paternal care, sociality, and sexual dimorphisms.
To test their hypotheses, the team of biologists gathered data from ISI Web of Science and Google Scholar. They searched for road kill and road mortality that involved mammals and birds on 18 August 2011. The final analyses came from 10 studies that included 80 mammal species and 99 bird species.
The researchers first created a sequence of linear models in SPSS v. 20. After that, used the final models from the forwards stepwise procedure, and created a least squares model. These models were used to eliminate outliers and normalize the data. The researchers themselves did gather their own evidence, but rather used statistics and data from previous studies.
(Figure from Taylor C. Cook and Daniel T. Blumstein, http://www.sciencedirect.com/science/article/pii/S0006320713002905#)
The results showed that omnivores seem to have the highest mortality rate compared to carnivores. This is interesting because herbivores had a smaller mortality rate than omnivores. Thus, it is this “in-between” that puts omnivores in a disastrous position.
The results also showed that body mass, diet, and sociality did explain significant differences in the rate of mortality although not as substantial as diet. The other ten tested variables had negligible effects on the rate of mortality. Thus, we can conclude that diet seems to be the largest factor.
Now that we have a better understanding of the factors that play a role in vehicle collision mortality, we can now look at the solutions that could potentially reduce this rate.
Many have suggested in the past that lower speed limits should be imposed and more educational outreach programs should be implemented. But with this new knowledge, we can now shift the attention from the drivers to the animals.
Previous studies have shown that certain animals, especially herbivores, are attracted to green vegetation. The animals move toward their food source (green plants, trees, etc.). If we remove the food source around the roadways, then the animals will most likely not go toward the road. This is difficult and not feasible due to the large amount of road we have. According to the National Atlas Transportation Center, just the United States alone has over 3.9 million miles of public road. Thus, it would too costly and time-consuming to further proceed in this approach.
Surrounding the roads with fences has also been a popular option, but once again this is costly and time-consuming.
Finding the exact solution is strenuous but with further future research, we can surely come up with the answer.
References
Blumstein, D. T., & Cook, T. C. (2013). The omnivore’s dilemma: Diet explains variation in vulnerability to vehicle collision mortality. Biological Conservation,167, 310-315. Retrieved from http://www.sciencedirect.com/science/article/pii/S0006320713002905
Conservation Biology News 