To develop a predictive understanding of both foraging and population dynamics within the Sevilleta small mammal community, the physiological and environmental conditions driving alternative foraging behaviors among both caching and non-caching rodent species are incorporated into a mechanistic state-dependent model. Our stochastic dynamic program (SDP) determines how species-specific body condition and caching behaviors, as well as environmental uncertainty (e.g., plant productivity), impacts foraging. The goals of our SDP are threefold, and involve determining: 1) which resource type (C3 vegetation, C3 seeds, C4 vegetation, C4 seeds, or insects) maximizes an individual’s fitness with respect to its age and its current endogenous and exogenous (cache) energetic state, 2) whether a given resource should be consumed or cached, and 3) the population-level consequences of the predicted strategies.


When combined with the novel data collected during our monthly small mammal trapping program, the stochastic dynamic program will generate predictions of foraging behavior based on the resource landscape as well as endogenous and exogenous (cached) energy stores. This model will be used to project the dynamics of populations based on fitness-maximizing foraging strategies that directly affect individual reproduction and survival. This process will enable us to forecast extinction risk under environmental conditions anticipated by future climate scenarios.


In our framework, an individual must balance maintaining its body condition while establishing a buffer of endogenous and/or exogenous reserves to survive a stochastically varying environment. Foraging decisions maximize the individual’s future fitness integrated over the course of its lifetime, thus predicting behaviors representative of the evolutionary endpoint of natural selection. As such, the SDP framework will be used to assess the impact of fitness-maximizing foraging behaviors on population dynamics, ultimately linking the effects of different resource distributions to extinction risk.


We will inform the SDP with empirical data describing the relationship between body condition and reproductive output, such that the fitness values associated with decision arrays will permit simulations of individual birth/mortality through time, allowing us to calculate population size, survival, extinction risk, and the presence or absence of cycles. To what extent these model outputs conform to empirical observations will be assessed both qualitatively and quantitatively.

Supporting Documents:

Yeakel, J.D., Bhat, U., Newsome, S.D. (2020) Caching in or falling back at the Sevilleta: the effects of body size and seasonal uncertainty on desert rodent foraging. American Naturalist.