This video turns to how different reproductive strategies affect the welfare of animals. Unfortunately, the reproductive strategy that is most prevalent, r-selection, is also the one that results in the most suffering. Animals who are r-selected have large numbers of offspring and invest very little resources in each one. This unfortunately means that almost all of these animals will die painfully before reaching adulthood.
Also available as a chapter of our companion ebook to the video course Introduction to wild animal suffering: A guide to the issues
Until now, we have been seeing specific ways animals can be harmed. In this chapter, we will examine the extent of the suffering of wild animals more broadly, by looking at general indicators of how many animals die on average relative to how many survive at different life stages. This is a useful indicator because the factors that cause animals to die, such as disease, lack of food or water, injuries, and cold, often cause suffering to the dying animals. It sounds obvious, but it’s an important point. If an animal is born and starves to death without ever being able to eat, the main experience in her short life is what it feels like to starve to death. For this reason, knowing the proportion of animals who typically die at different ages in a certainspecies—known as age-specific mortality—can give us a general indication of the extent to which suffering is present in populations of that species. It can also enable us to roughly estimate the proportion of animals with very bad lives in comparison to those who have relatively good lives. This estimation may be very rough, but it’s the best one we can make at this point.
We can begin by considering some of the reasons why in most species, most animals die shortly after birth, while only a few survive to adulthood. Ecology and natural history are not shaped by the interests of sentient individuals. Instead, they optimize an individual’s biological fitness, that is, the ability of individuals to leave descendants, especially their direct descendants but also other close or distant relatives (who have similar genetic makeups). Because of this, different animals have different traits due to natural selection, because particular traits tend to increase their fitness.
Among these traits, some shape the life history of animals. A life history is the sum of the patterns and events that occur at certain ages, especially those related to reproduction and survival. These include, among other factors, the age at which the animals first reproduce, the number and size of offspring each time they reproduce, how much they invest in parental care, how many times they reproduce during their lifetime, and when they die.
Organisms and populations face trade-offs in reproductive strategies. If an animal has many offspring, it won’t be possible for her to invest significantly in their survival. And vice versa: if an animal invests a great deal of energy in the survival of her children (so, for example, they are more developed at birth or receive more parental care), she will not be able to have many of them. Animals with these reproductive traits may give birth to just one child or lay just one egg each time they reproduce. Because of their low reproduction rate and the greater energy they invest in their offspring, populations of these animals will have relatively low rates of mortality.1
But for a large number of species, what maximizes the number of offspring that survive is not the maximization of each one’s ability to survive, but the maximizationof the number of offspring they have. In these cases, a trait that provides some survival advantage, such as parental care, may not be selected for if it requires an energy investment that makes it impossible to have a larger number of offspring. As a result, species that follow this reproductive strategy tend to have high infant mortality rates, and the individuals tend to have very short lives.
Through evolution, animals end up having some of these traits instead of others, and the traits they end up with shape their life histories. Some mammals such as great apes, cetaceans (whales, dolphins, seals, and porpoises), bears, elephants and other herbivores, and some birds such as albatrosses follow a reproductive strategy of having a few offspring and giving them a lot of care. However, there are very few species of animals who do this. The overwhelming majority of animals follow a different strategy, reproducing in large, in most cases very large, numbers and with high infant mortality rates.
In a stable population, assuming that the number of members of different generations remains similar, only one offspring per parent will survive to maturity and reproduce. Most other animals will die, often shortly after coming into existence. This means that most of the animals in a population at any one time are very young, mostly newborns who will die before reaching maturity. As we have seen, most animals exhibit this reproductive strategy, including most species of invertebrates, fishes, amphibians, and reptiles. For example, common cane toads can have clutches exceeding 25,000.2 Many marine-and land-based invertebrates can lay hundreds, thousands, and in some cases millions of eggs at a time. Other animals have mixed reproductive strategies that result in having large numbers of offspring.3
The predominance of reproductive strategies that result in large numbers of offspring dying when they are very young has important consequences for the suffering of animals. Although some animals might experience little pain due to a quick death or lack of sentience, others suffer greatly from a prolonged death. The fact that many animals begin their lives very small and underdeveloped does not mean they aren’t sentient. For example, it has been shown that adult zebrafish respond to harmful stimuli in a way that indicates sentience, and that larval zebrafish respond in similar ways to adults. In addition, animals who die when they are very young may not have had any significant positive experiences in their lives prior to the terrible experience of dying. This gives us strong reason to think that their short lives likely contain much more suffering than pleasure.4
What about the animals who belong to species with high survival rates in infancy? Many of these animals still die before reaching maturity. Even if a mother gives birth to only one offspring per reproductive season, the frequency of her reproduction means she can have several offspring over the course of her lifetime. We can see this in humans, who biologically have the potential to have more than 10 children during their lives. Recall that, for a population to remain stable, only one offspring per parent tends to survive. This means that even for animals with relatively high survivalrates, it is common for most children to die in their youth.
As for the few animals who live to adulthood, we can’t automatically assume they are happy. They constitute the minority whose lives are long enough to include relatively large amounts of positive experiences. However, these animals may have lives that consist of prolonged suffering due to factors like disease, malnutrition and thirst, weather conditions, parasitism and conflicts with other animals, injuries, and psychological stress. Thus, even when animals survive past their infancy, their lives might still consist of more suffering than enjoyment.
Even when adults have good lives, the total amount of suffering experienced by the young can still outweigh the positive experiences of adults, for reasons we have already seen: the disproportionate number of offspring who don’t survive and who have lives with more pain than pleasure.
To conclude, what we have seen so far doesn’t imply that suffering necessarily prevails for all animals, all populations, or all species, but it suggests that this is the case for the majority of animals. It also shows that by looking at the population dynamics of different species—in particular, at how many animals on average die in comparison to how many survive at certain ages, known as their age-specific mortality—we can get a very rough idea of the proportion of suffering compared to wellbeing in that species. It can also help us to compare their suffering to the suffering endured by other animals with different age-specific mortality rates. The prevalence of suffering inan animal population doesn’t depend on contingent circumstances, but is the result of how natural selection works. In a nutshell, the underlying explanation can be summarized as follows:
In natural history, sentience is selected for because in many situations, it increases an animal’s fitness. Sentience implies that when an animal’s needs are satisfied, she will probably feel pleasure, but when she is affected by circumstances threatening to kill her, such as lack of food, physical harm, or inadequate temperature, the animal will suffer. In addition, certain life history traits are selected for that favor certain reproductive strategies. The most prevalent traits make it impossible for more than a fraction of sentient beings to survive past infancy and to have their needs satisfied. The rest will die due to circumstances such as those mentioned above, which can cause great suffering. Because of this, suffering is likely to prevail for the majority of animals.
This shows why our efforts to help them when it is feasible are so important. We can’t help all the animals who need it. However, there are many cases when it is possible to help some or many of them.
1 Roff, D. A. (1992) Evolution of life histories: Theory and analysis, Dordrecht: Springer; Stearns, S. C. (1992) The evolution of life histories, Oxford: Oxford University Press; Flatt, T. & Heyland, A. (eds.) (2011) Mechanisms of life history evolution: Thegenetics and physiology of life history traits and trade-offs, Oxford: Oxford University Press; Sæther, B. E.; Coulson, T.; Grøtan, V.; Engen, S.; Altwegg, R.; Armitage, K. B.; Barbraud, C.; Becker, P. H.; Blumstein, D. T.; Dobson, F. S. & Festa-Bianchet,M. (2013) “How life history influences population dynamics in fluctuating environments”, The American Naturalist, 182, pp. 743-759.
2 Rastogi, R. K.; Izzo-Vitiello, I.; Meglio, M.; Matteo, L.; Franzese, R.; Costanzo, M. G.; Minucci, S.; Iela, L. & Chieffi, G. (1983) “Ovarian activity and reproduction in the frog, Rana esculenta”, Journal of Zoology, 200, pp. 233-247.
3 Vandermeer, J. H. & Goldberg, D. E. (2013 ) Population ecology: First principles, 2nd ed., Princeton: Princeton University Press; Rockwood, L. L. (2015 ) Introduction to population ecology, Hoboken: Wiley-Blackwell; Leopold, B. D. (2018) Theory of wildlife population ecology, Long Grove: Waveland
4 Ng, Y.-K. (1995) “Towards welfare biology: Evolutionary economics of animal consciousness and suffering”, Biology and Philosophy, 10, pp. 255-285; Tomasik, B. (2015a) “The importance of wild-animal suffering”, Relations: Beyond Anthropocentrism, 3, pp. 133-152 [accessed on 11 December 2019]; (2015b) “Estimating aggregate wild-animal suffering from reproductive age and births per female”, Essays on Reducing Suffering, Nov 28 [accessed on 12 October 2019]; Faria, C. & Paez, E. (2015) “Animals in need: The problem of wild animal suffering and intervention in nature”, Relations: Beyond Anthropocentrism, 3, pp. 7-13 [accessed on 30 December 2019]; Horta, O. (2017) “Animal suffering in nature: The case for intervention”, Environmental Ethics, 39, pp. 261-279; Vinding, M. (2016) “The speciesism of leaving nature alone, and the theoretical case for wildlife anti-natalism”, Apeiron, 8, pp. 169-183; Fischer, Bob (2018) “Individuals in the wild”, Animal Sentience: An Interdisciplinary Journal on Animal Feeling, 23 (8) [accessed on 27 December 2019]. On the relation between age-specific mortality and wild animal suffering see also Alonso, W. J. & Schuck-Paim, C. (2017) “Life-fates: Meaningful categories to estimate animal suffering in the wild”, Animal Ethics [accessed on 29 December 2019]; Hecht, L. B. B. (2019) “Accounting for demography in the assessment of wild animal welfare”, bioRxiv, October 28 [accessed on 2 January 2020].