Foraging for Survival: Yearling Baboons in Africa (review)

Foraging for Survival: Yearling Baboons in Africa. By Stuart A. Altmann. Chicago: Univ. of Chicago Press, 1998. Pp. 608. $70.

One of the premier primatologists, in this book Stuart Altmann summarizes his thoughts after conducting fascinating research on baboons in Amboseli National Park for many decades. Altmann sets forth three goals for the book: to provide (1) a behaviorist's and natural historian's description of an intriguing ecosystem and how young baboons cope with this environment, especially through their foraging behavior; (2) a conceptualization of a young baboon's foraging behavior, using a mathematical model that defines optimal foraging decisions and comparing model predictions with observed foraging choices; and (3) an explanation of how baboon foraging may serve as a model system for assessing the foraging decisions of the primate ancestors of humans. Natural historians, animal behaviorists, ecologists, and anthropologists should prize all three goals, and Altmann provides much information on these topics.

However, this is a somewhat difficult work to read, because the three goals are not balanced or well integrated. First, the book is exhaustive (372 pages of text, 54 pages of appendices, and 121 pages of tables), focusing on data collected over a single year (1974-1975) on 11 yearling baboons in a single social unit. Second, for those more concerned with natural history, behavior, and anthropology, the book may present less of interest (approximately 140 pages) than to those interested in optimal foraging models and their application. Third, throughout the work, Altmann provides us with many points that diverge from the work's main focus. These distract the reader from the principal story and often are little more than personal opinion. However, personal opinions may be interesting when they come from a primatologist of Altmann's renown.

The majority of the book focuses on the development of mathematical models for optimal foraging decisions, their parameterization, and comparison of predicted to observed diets for yearling baboons. The models are based on the well-established optimization technique of linear programming. The description of their application to yearling baboons is covered in the minutest detail, and 10 different models based on five potential foraging goals and different sets of foraging constraints emerge. While models with the goal of energy maximization (greatest energy intake per day, given constraints to food intake such as mineral needs, protein requirements, digestive capacity, water intake, etc.) bear resemblance to the observed diets of yearling baboons, there are marked discrepancies. For example, the best fit between the average predicted and observed diets is only 38 percent, and for individual diets the best fit was only 17 to 63 percent. Altmann argues that the predicted optimal diet is a benchmark that few if any individuals can attain, and therefore poor performance should be expected.

Given my own interest in foraging models, I was astonished by the extremely poor fit between predicted and observed diets, given the generally good fit of these types of models (averaging 85 percent in over 400 studies [1]). The explanation for this lack of fit in Altmann's study may be very simple, and he even briefly admits to this likelihood in Chapter 6, saying that the digestive capacity and feeding time constraints are not realistically calculated. The digestive capacity does not incorporate realistic turnover rates of foods through the baboon's digestive tract, and the feeding time constraint does not incorporate the search time for food and movement between feeding patches (Appendix 1). Both lead to overestimates of potential food intake. Therefore, there is very good reason to question the appropriateness of the optimal foraging models' structure and parameters. Rather than being convinced of the models' utility, I was left with more questions--such as whether maternal foraging and social rank might strongly influence yearling foraging--and I wondered why Altmann did not pay more attention to these issues.

Altmann's foraging models, the centerpiece of this book, also suffer from not taking advantage of the...