Insect herbivores, life history and wild animal welfare

Summary

  1. Life history classification will hide some significant differences in the lives of wild animals. Not all species within a given classification possess all of the traits associated with that group even across all years or all locations. Therefore, when making moral decisions, one also has to consider how average quality of life should be determined in the face of large variance

  2. Among insect herbivores, some lifespans are relatively long, some modes of death are very quick, and some small-bodied herbivores may lead lives characterized by ample food resources

  3. Although determining the affective states of wild animals from this data is impossible, it seems quite likely that the majority individuals in some subgroups, such as those sheltered from both the elements and predation by feeding from within plant tissues, lead very high quality lives

  4. Knowing a group of organisms produce many offspring, have high mortality rates, small body size and are short-lived is not sufficient to determine that their lives are a net negative (or positive)

The argument from life history suggests that since many species produce many more offspring than survive to adulthood, are of small size and so subject to many abiotic and biotic threats, and are short-lived relative to humans, that there is more suffering than happiness in nature and therefore we have a moral obligation to end this suffering (e.g., Tomasik 2015). Here, we do not attempt to examine such moral quandaries (for a thought experiment on these issues see Brennan 2017). Instead, we aim to improve the quality of discussions by examining available data on one group of wild animals. Because of their broad scope, some previous analyses of wild animal welfare have lumped many species together at one pole of a continuum of life history strategies. Given these large groupings, and some issues with the life history classifications themselves, it is unclear to what extent this approach actually informs us about animal suffering in general. On the other hand, examinations of the lives of particular species are also unsatisfactory, since they refer to the specific rather than the majority. By narrowing our focus to one group, we may be able to bring more data to bear on our intuitions regarding wild animal welfare. In this post, we explore the literature regarding one group of organisms that are classically grouped in the “r-strategist” life history category: terrestrial insect herbivores.

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Life history classification

Summary

Understanding the life history of animals is important for understanding wild animal welfare, but has been understudied by animal welfare advocates. In particular, life history generalizations have been used to claim that the lives of most wild animals are net negative (see discussion of this position in Brennan 2017 ). However, there are several methods of life history classification in use in ecology and evolutionary biology. The theoretical foundations for r-K selection referred by some advocates have been discredited, and in addition some large species groups cannot be placed on this continuum. However, a related form of this classification, fast-slow is still in use in the sciences. Tripartite classification schemes seem to be more appropriate for plant, insect and fish species, which do not easily fit into a single axis. More generally, large scale reviews usually come to the conclusion that a single composite axis of variation is not sufficient to explain the wide range of life history variation. One very important point is that all classification methods are considered continuums; that is, most species will lie somewhere in the middle of axes of variation rather than at the extremes.

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