Early-life experiences are a priority in wild animal welfare research
August 3, 2021
Wild Animal Initiative recently announced our first public call for proposals, which focuses on the welfare and ecology of juvenile wild animals. Holding calls for proposals on specific themes allows us to showcase the pillars and breadth of wild animal welfare research. Here, I will explain why we think it is right to prioritize the interests of juvenile animals in most cases, drawing on my recent paper in Biological Reviews.
In many species, a majority of individuals die before reaching adulthood. For the typical wild animal, the welfare they could expect as an adult is irrelevant — but all animals experience at least some of what life is like as a juvenile. If our moral priority is making sure that as many animals as possible experience good welfare, then our practical priority should be ensuring the well-being of juvenile wild animals.
In my paper (and earlier blog post) on the importance of considering age when quantifying wild animals’ welfare, this thinking is formalized with the concept of “welfare expectancy.” Welfare expectancy represents the expected sum of welfare that a typical newborn individual will experience over their lifetime, accounting in theory for the distribution of possible welfare and lifespan outcomes. Depending on how welfare and survival rates vary with age in a given species, welfare expectancy may be especially responsive to changes in welfare and/or survival rate during particular periods of life (“welfare elasticity”, a form of proportional sensitivity analysis; Manlik et al. 2017).
If we assume there is no age-specific variation in survival rates or welfare, then lifetime welfare expectancy will always be most responsive to interventions benefiting the youngest individuals, since they will be the most numerous age group. In reality, survival rate and welfare likely do vary with age in nearly all species. It is often juveniles and senescent (very old) adults who are most vulnerable to disease, starvation and predation. Therefore, it is plausible that individuals in these demographics experience lower welfare on average than prime-age adults.
When might early-life experiences be less important to an animal’s expected lifetime welfare? In species with low juvenile survivorship and long adult life expectancies, the amount of time lived as an adult by the minority of individuals who survive their early years could exceed the amount of time lived by all the many individuals who died as juveniles. In this scenario, our priorities would likely be split between efforts to improve juvenile survival (so that a greater proportion of individuals reach adulthood) and efforts to improve adult welfare.
Species that meet these conditions tend to be less numerous, however, and are therefore unlikely to be among our priorities in the near future. For example, even North American black bears — potentially long-lived animals — appear to collectively live a majority (~55%) of their years as juveniles (based on baseline vital rates from Lewis et al. 2014). For each study or intervention, it will ultimately be important to define their target demographics and estimate how many animal life-years could potentially be improved in quality.
The everyday experiences of juvenile wild animals are little understood, yet could be highly impactful for wild animal welfare. We are excited to review your proposals for research on this important and neglected topic.
See here for more details.
