The Importance of Good Field Skills in Understanding Animal Mortality

By Bogdan Cristescu, Ph.D. and Mark Elbroch, Ph.D.
Conservation Scientist; Panthera Puma Program Director

Puma with buck

Field naturalist skills — such as identifying plants and insects — are so fundamental to collecting data during field research that they are often assumed or overlooked. Over time, the amassed knowledge collected through the application of field skills has formed our understanding of nature, which in turn drives efforts in conservation and wildlife management. However, field skills, including that of reading and interpreting animal tracks and other signs, are difficult to standardize.  

Poor field skills lead to poor data collection, which leads to poor inference and conservation. Take, for example, research on elk. When researchers discover the remains of a dead animal, they are charged with determining the cause of death. What that researcher sees among the leaves, dirt and blood splatters paints a picture of what might have happened. The shape of the carcass as it lies, the color of the eyes and tongue and whether the animal is tucked up under vegetation or found out in the open, all contribute to the narrative forming in the researcher’s mind. Ultimately, what that researcher records becomes the data — death by disease, starvation or mountain lion — only a few of the countless possibilities. And if a researcher misclassifies the cause of death — for example, claiming carnivores are responsible when in fact they were scavenging an already dead animal — the results will overemphasize the impacts of carnivores on prey species. Such results drive carnivore control programs funded by public money, and yet such carnivore killing will have little impact on aiding the elk population of concern, especially if research based on poor fieldwork had inflated the impacts of carnivores in the first place. 

Infographic chart
Conceptual figure showing the type of data that can provide clues on herbivore cause of mortality in predation studies. The carcass is surrounded by additional sign (e.g., tracks, scat, beds, drag marks) that can help identify the predator.

This is a very real concern for work currently conducted around the world, with often terminal ramifications for large carnivores. In collaboration with researchers at the University of California Santa Cruz (Dr. Chris Wilmers) and Victoria University in New Zealand (Dr. Heiko Wittmer), and several others, we wrote a new paper just published in Ecology and Evolution to call attention to this important issue, suggest standards for conducting this type of research in the field, and suggest standards for the transparent reporting of field methods in science papers, so that the audience of any research can assess whether the initial data collected in the field was valid to begin with.  

We also shared our own research from a 5-year study on mule deer survival in Siskiyou County, California to illustrate our approach. During the study, we investigated over 100 mortality sites of mule deer. Using a simple hierarchy of confidence level (Poor, Medium, High) we showed that it is possible to be transparent about outcomes of mortality site visits and that it is important to acknowledge shortcomings and logistical challenges of interpreting animal sign in the field. For example, we found that the interpretation of neonate (new fawns) mortality sites was strongly influenced by the time it took for researchers to visit the site — the longer it took for someone to visit the site, the less certain the data became that they collected.

Fawn killed by bobcat
A radiocollared fawn killed and partially cached by a bobcat in northern California, that was tracked as part of the Siskiyou Deer and Puma Project.
©Bogdan Cristescu/Chris Wilmers/Heiko Wittmer 

Scientific journals increasingly ask researchers to make public the data used in analyses, along with programming code. Here, we suggest it is time to add transparency to the field process as well, as the data that drives analyses and the inferences so often driving management decisions for ungulate populations, which often include carnivore control, are all built upon what happens in the field. With the deterioration of field skills across the biological sciences, this is more important than ever.  

In truth, we also hope to inspire people to get outside and practice their field skills.