August 14, 2023

Tradeoffs involve compromises between competing priorities. Many aspects of wild animals’ lives are defined by tradeoffs between multiple traits or behaviors, each of which is important to the animal’s evolutionary fitness, but which cannot all be expressed to the fullest simultaneously. Another way to think of tradeoffs is in terms of interventions. 

When exploring potential interventions, scientists need to consider how improving welfare for individuals of one species might negatively impact the welfare of non-target individuals. A core goal of wild animal welfare research is to understand these tradeoffs well enough to ensure management efforts are net-positive.

Helping some animals can hurt others

Though we typically measure welfare of same-species individuals within a population, it’s important to look at net effects within an ecosystem as well. An intervention that helps one kind of animal but consequently harms many other animals may not actually improve overall welfare. For example, a 2019 study of the TransCanada highway found that development of wildlife crossings and fencing reduced mortality across species on roadways, but this benefit was offset by increased mortality on a nearby railroad for individuals of other species. This tradeoff highlights the need for coordinated approaches to helping animals safely navigate their landscape.

Studying interventions can reveal tradeoffs

A 2021 persepctive in Biological Conservation provides another example of “killing with kindness.” It examines how well-intentioned UK gardeners may have actually decreased the population (and possibly the welfare) of willow tits (Poecile montanus) by stocking their bird feeders through the winter — when the willow tits have flown south but Eurasian blue tits (Cyanistes caeruleus) are still around to benefit.

The researchers proposed two drivers of this effect. First, the blue tits’ population may have increased because they had access to extra food at a time it was otherwise scarce, allowing them to outcompete willow tits for food in the non-winter months. Second, the growing blue tit population may have made it hard for willow tits to secure and maintain nest sites — leaving them vulnerable to predation. If these hypotheses are true, then deciding whether or not to encourage winter bird feeding requires evaluating the tradeoffs between willow tits, blue tits, and other affected species.

Tradeoffs and estimating net effects

Predicting the welfare effects of wildlife management decisions often requires digging deeper than population-level metrics. In the case of winter bird food provisioning in the UK, measuring the decline of the willow tit population may be sufficient to inform conservation decisions. But understanding what that means for animals’ well-being requires information on their individual experiences, including looking at their behavior, physiology, and specific causes of death. As a result of this intervention, how many more birds than usual are dying from starvation versus predation, and at what age? Which of those fates causes more suffering?

Wild animal welfare research has an important role to play in making welfare improvements a reality. Without solid science to back welfare interventions and taking a holistic approach to consider the potential tradeoffs for all species involved, we can’t be confident our well-intentioned actions will be net-positive.