The role of food, weather and climate in limiting the abundance of animals

Abstract

More and more studies are demonstrating that populations of animals - from herbivores to top predators, vertebrates and invertebrates - are limited by their food, and that the availability of this food is dictated by the weather. Satellite monitoring is revealing how cyclic and quasi-cyclic climatic patterns, like the El Niño Southern Oscillation and the North Atlantic Oscillation, are driving and synchronising these weather-driven changes in the supplies of food. Changes in the amount of food available operate to limit the abundance of populations largely through their influence on the survival of the very young: the Achilles heel of all populations. Any individual organism struggles to use whatever resources it can get from a mostly inhospitable environment to maximise the proliferation of its genes. Each level of a food chain is thus dependent upon, and pressing hard against the limits set by the one below. The resulting intra- and inter-specific interactions produce a multitude of complex outcomes, that significantly influence the dynamics of populations, but do not determine their ultimate size. There is no density-dependent regulation of abundance. Intra-specific competition does not determine the size of populations, it only decides which few individuals gain access to the limited food. Nor do predators regulate their prey. They, too, are limited by their food, and the abundance and quality of food is dictated by the weather.

Habitat selection of the Ortolan bunting Emberiza hortulana in Poland: predictions from large‐scale habitat elements

“…However, its role is generally less clear when compared to habitat preferences. We suspect that ambient temperature indirectly influences food availability and nest sites (White 2008).…”

Nitrogen and Carbon Concentrations in the Stomach Content of Bank Voles (Myodes glareolus). Does Food Quality Determine Abundance?

“…Our results suggest therefore that high diet quality may have stronger positive effects on survival or on reproduction rather than on factors determining body growth. Thus a mechanism operating trough the reproductive system may delay timing of reproduction for both males and females, possibly affect lactation or the oestrus of females (White 2008). These physiological effects by nutritional status need further studies.…”

Anticipation and tracking of pulsed resources drive population dynamics in eastern chipmunks

“…For example, the reproductive events of many species have frequently been shown to track pulsed resources (Ostfeld et al 1996, Clotfelter et al 2007, Yang et al 2010. Furthermore, the prolonged absence of resources between pulse events can constrain key fitness components (e.g., survival and reproductive rates) and contribute to population collapse (reviewed in White 2008). A resulting key feature of the consumerresource interaction is a strong lagged demographic response of consumer communities to food abundance (Jones et al 1998, Ostfeld and Keesing 2000, Yang et al 2010.…”

“…A resulting key feature of the consumerresource interaction is a strong lagged demographic response of consumer communities to food abundance (Jones et al 1998, Ostfeld and Keesing 2000, Yang et al 2010. Such a lag may cause juveniles to enter the population when food abundance is low, potentially reducing their survival compared to juveniles born prior to or during resource pulse events (White 2008). For short-lived consumers, the main determinant of population persistence over time is usually early adult fertility and juvenile recruitment rather than prolonged adult survival (Heppell et al 2000; but see McAdam et al 2007).…”