Ecologists discuss how a common emotion changes the landscape and by showing the evidence for the ubiquity of fear, the conditions under which it is disabling for the prey species, and the brain chemistry that hinders learning under the influence of fear, the ecologists help us be better animal trainers.
Zanette, L. Y., & Clinchy, M. (2020). Ecology and neurobiology of fear in free-living wildlife. Annual Review of Ecology, Evolution, and Systematics, 51, 297-318.
Zanette, L. Y., & Clinchy, M. (2019). Ecology of fear. Current biology, 29(9), R309-R313.
Zanette and Clinchy reviewed the literature for the ecology of fear, putting their own experimental evidence into context. They defined the ecology of fear as the ecological effect of prey species which can set up a trophic cascade benefitting the plant community and the prey’s ecological competitors. They then reviewed the ecological literature, smashing the old assumption that predators eat only excess animals, and finding support for the idea that a single traumatizing event could end up having large-scale, long-term effects on the landscape. They described ecologists’ endeavors to simulate predation by culling and nest robbery and to fool prey with predator odors, sounds, and scat. According to the statistics provided, most vertebrate animals end up being consumed by some type of predator, so, at best, fear merely motivates a delay in death by predation.
Chillingly, they identified humans themselves as the superpredator in the system, an animal that could inspire fear in both herbivores and carnivores. In fact, with the human penchant for exterminating carnivorous species, predators have even more reason to fear us. Our fearsomeness plays a critical role in the current global distribution of many predatory species.
The authors defined PTSD as fear persisting for at least a week and altering the function of the fear system (amygdala, hippocampus, etc.). Animals with PTSD remain in vigilance and generally show suppressed foraging. They mate less and do not provide well for their offspring. Their brain chemistry is disrupted in a few specific ways: they may show protein-coding genes (FosB) associated with chronic stress, or decreased neurogenesis and maintenance with a loss of doublecortin, a protein associated with cell growth. This protein plays a critical role in learning and forgetting. Doublecortin is proving to be a very sensitive marker to trauma, however, it, unfortunately, cannot be measured in living animals.
Trauma is not an absolute threshold but will depend on the individual animal and the type of traumatic event experienced. The animal’s age, history, genetics, reproductive status, context, and personality are all factors that influence the outcome.
Ecologists finding evidence that the landscape itself is influenced by long-lasting levels of fear in herbivorous animals shows the fallacy of assuming wild horses are not traumatized by predation or human activity. This paper suggests that through traumatic contact with “the superpredator, equines could be cast into a long-term traumatized state, in which it is hard for them to learn.
Injuries, family separation, and relocation to unfamiliar areas are all likely to be trauma-causing events. Some animals will recover quickly, some will not. As the custodians of these animals, we have an obligation to do as little harm to them as possible. An analysis of fear needs to be done to identify protocols that could be modified to produce less trauma.
Why would fear in animals ever be a good thing? If you’ve watched the video about the effects of wolf introduction in Yellowstone, you have an idea. Everything changes.
In this review article, Zanette and Clinchy summarize what is known about the ecology of fear in wild animals. They discuss how fear can affect the behavior, physiology, and ultimately the survival of animals in the wild. They also discuss how fear can be influenced by factors such as predation pressure, habitat fragmentation, and human activity. The article concludes with a discussion of the implications of fear for the conservation and management of wild animals.
The authors of the article argue that fear is an important factor to consider in the conservation and management of wild animals. They suggest that we need to understand how fear affects animals in order to develop effective conservation strategies.
“Natural populations of free-living wildlife may commonly contain a large proportion of individuals that have suffered a physical trauma. … Most predator attacks are unsuccessful, meaning most prey escape, but there is growing evidence that they do not necessarily escape unharmed, resulting in considerable numbers of walking wounded.”
Orion’s face is deeply scarred below his eyes; it was a fresh wound when he arrived at Mustang Camp. There were two foals with his band, one a recent orphan, the other with a fresh wound matching her father’s. No one will tell me what happened to the orphan’s mother, but I have to assume she died in the roundup. This band of five horses are the poster-children for the effects of traumatic handling.
After a full year in captivity, I still cannot hand-feed Orion. He can calmly be in the same space with me, but after a moment or two, he will need to retreat. In that moment, does he remember his mare breaking her neck, or is it the memory of his own painful encounter with a solid fence that makes him leave? He is one of the number of walking wounded.
Zanette and Clinchy did not offer much hope for Orion’s recovery. They say that there is evidence that permanent fear in animals is a fact-of-life with beneficial consequences to the environment.
Removing horses and burros from rangeland is not going to stop, so we, as ethical superpredators, have an obligation to conduct these removals in the most humane way possible. Because these animals must be “disposed of” and placement into adoptive homes is the preferred disposal alternative, agencies should tailor their handling practices to avoid creating permanently fearful animals. This kind of traumatic handling diminishes the useability and value of the animals gathered. They become damaged goods.
I was intrigued when I first read about doublecortin being a way to measure PTSD until I realized that it had to be measured from the brains of dead animals. Still, we could use this to measure the PTSD in animals that die in roundups and in holding. A good hypothesis is that the animals that die in the roundup would have less evidence of PTSD (which is a long term effect, not a sudden fear) than the animals in holding.
In a perfect world, we would use this knowledge to improve our handling, reduce death rates, and avoid permanently damaging our animals.
Keywords: PTSD in wildlife, fear, doublecortin