Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

Citation classic - optimal foraging - a selective review of theory and tests

Burrow systems of two coastal populations (El Alamo and Los Maitenes) of the social octodontid rodent Spalacopus cyanus were studied in central Chile. Tunnel systems were estimated to be up to 600 m long, ran at a depth of 15 cm and had a diameter of 6 cm. Tunnel openings were usually unplugged, and a minor preference toward southern and south-eastern direction of entrances was apparent. Nests, frequently found in the root system of Berberis actinacantha at a depth of 30 cm, consisted of grasses, roots and plastic bags. Nests serve for sleep, care of the pups and as latrines. Many staphylinid beetles of the genus Edrabius and other invertebrates were found in the breeding nests. Food chambers contained up to 13.2 kg of bulbs of the geophyte Dioscorea longipes collected by a single colony consisting of 26 animals (including 10 adults) and were frequently found at El Alamo. However, no bulbs were found at Los Maitenes, where the coruros forage above ground on leaves of Convolvulus arvensis within a radius of about 10 cm of the entrances. Apparently, the burrow design is also affected by food availability, soil quality, and colony size.

Spalacopus cyanus (Rodentia: Octodontidae): an extremist in tunnel constructing and food storing among subterranean mammals

We determined the dietary habits of two sympatric and allotopic populations of Ctenomys (C. australis and C. talarum) that inhabit a natural dune grassland on the sea coast at Necochea, Buenos Aires Province, Argentina. Both species were found to be generalist herbivores as they consumed almost all plant species available in the grassland. Contrary to what we had expected, they fed principally on the aerial fraction of the vegetation, and preferred grasses overforbs. The greater proportion of the subterranean fraction in autumn and winter in C. australis diets compared to C. tala rum might be related to differences in the vegetation around the burrows they inhabit. Ctenomys australis and C. talarum diets differed markedly only in September; however, these differences may not have been totally seasonal, there may also have been a spatial effect due to the soil structure of the sympatric area. Ctenomys australis and C. tala rum distributions seem to be related to soil characteristics with individual animals feeding and selecting mainly among the vegetal species in their own home range. The results of this study show that these species of Ctenomys present a feeding strategy which is adaptative in subterranean rodents due to their high digging cost and to the low available energy to explore in their subterranean environment.

/pdf/dietary-preferences-of-two-sympatric-subterranean-rodent-t9k5hgsth0.pdf

Dietary preferences of two sympatric subterranean rodent populations in argentina

Mixing matrices can be used to describe subgroup interactions in mathematical models which have heterogeneity in population structure. A discussion is presented of two different approaches to the formulation of such mixing matrices. The relation between the two different methods is discussed, using examples based upon models of the transmission dynamics of HIV. There follows a discussion of the application of the mixing matrix approach to other areas in population biology, and a complementary overview of recent advances in theoretical ecology that may have applications in theoretical epidemiology.

Mixing ecology and epidemiology.

A costly search for food in subterranean rodents resulted in various adaptations improving their foraging success under given ecological conditions. In Spalax ehrenbergi superspecies, adaptations to local ecological conditions can promote speciation, which was recently supposed to occur even in sympatry at sites where two soil types of contrasting characteristics abut each other. Quantitative description of ecological conditions in such a site has been, nevertheless, missing. We measured characteristics of food supply and soil within 16 home ranges of blind mole rats Spalax galili in an area subdivided into two parts formed by basaltic soil and pale rendzina. We also mapped nine complete mole rat burrow systems to compare burrowing patterns between the soil types. Basaltic soil had a higher food supply and was harder than rendzina even under higher moisture content and lower bulk density. Population density of mole rats was five-times lower in rendzina, possibly due to the lower food supply and higher cover of Sarcopoterium shrubs which seem to be avoided by mole rats. A combination of food supply and soil parameters probably influences burrowing patterns resulting in shorter and more complex burrow systems in basaltic soil.

/pdf/habitat-and-burrow-system-characteristics-of-the-blind-mole-45nhn0izeg.pdf

Habitat and Burrow System Characteristics of the Blind Mole Rat Spalax galili in an Area of Supposed Sympatric Speciation

The foraging behavior of the subterranean mole rat Spalax ehrenbergi (Rodentia, Spalacidae) was tested according to the framework of optimal foraging theory. We compared the frequencies of food species hoarded in storage chambers of mole rats with the frequencies of these species occurring in the vicinity of the mole rats' nest mounds during the winter and spring seasons. In addition, we examined the food composition of several summer nest mounds. Laboratory observations were conducted in order to test the foraging behavior of mole rats under simulated subterranean conditions. The mole rat is a generalist and collects a variety of food species. Out of 33 plant species that were hoarded by mole rats in the 21 studied nest mounds, 61% (n=20) were geophytes, 21% (n=7) perennial herbs, 15% (n=5) annual herbs and 3% (n=1) dwarf shrubs. The frequency of each collected species in the 16 winter and spring nest mounds is in general accordance with its frequency in the mole rat's territory. This implies that the mole rat randomly samples the food reserve of its territory without special preference or directed search for a particular species. The collection or avoidance of any food item is not dependent on the presence or absence of any other food item. We suggest that the foragin generalism of the mole rat is a product of the constraints of a subterranean niche - the necessity to hoard food as much as possible in a limited time period and the high energetic investment of tunneling to the food items.

https://www.jstor.org/stable/pdfplus/4218987.pdf

E. M. Golenberg

Papers

Foraging strategy in a subterranean rodent, Spalax ehrenbergi: a test case for optimal foraging theory.