There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

A DNA test to sex most birds.

We redescribe the only previously known species of Myrsidea from bulbuls, M. pycnonoti Eichler. Sixteen new species are described; they and their type hosts are: M. phillipsi ex Pycnonotus goiavier goiavier (Scopoli), M. gieferi ex P. goiavier suluensis Mearns, M. kulpai ex P. flavescens Blyth, M. finlaysoni ex P. finlaysoni Strickland, M. kathleenae ex P. cafer (L.), M. warwicki ex Ixos philippinus (J. R. Forster), M. mcclurei ex Microscelis amaurotis (Temminck), M. zeylanici ex P. zeylanicus (Gmelin), M. plumosi ex P. plumosus Blyth, M. eutiloti ex P. eutilotus (Jardine and Selby), M. adamsae ex P. urostictus (Salvadori), M. ochracei ex Criniger ochraceus F. Moore, M. borbonici ex Hypsipetes borbonicus (J. R. Forster), M. johnsoni ex P. atriceps (Temminck), M. palmai ex C. ochraceus, and M. claytoni ex P. eutilotus. A key is provided for the identification of these 17 species.

A new species

Body mass in comparative primatology

ogy, A.B. Rylands (ed.), pp. 263–271. Oxford University Press, Oxford. Sick, H. 1997. Famílias e espécies: ordem Columbiformes. In: Ornitologia Brasileira, J. F. Pacheco (ed.), pp. 341– 350. Nova Fronteira, Rio de Janeiro. Stevenson, M. F. and Rylands, A.B. 1988. The marmosets, genus Callithrix. In: Ecology and behavior of Neotropical primates, Mittermeier, R.A., Rylands, A.B., Coimbra-Filho, A. and Fonseca, G.A.B. (eds.), pp.131–222. WWF, Washington. Vilela, S. L. and Faria, D. S. 2004. Seasonality of the activity pattern of Callithrix penicillata (Primates, Callitrichidae) in the cerrado (scrub savanna vegetation). Braz. J. Biol. 64: 363–370.

Observation of Black-Capped Capuchins (Cebus apella) Feeding on an Owl Monkey (Aotus brumbacki) in the Colombian Llanos

The distribution ofpn"mates between the lower Tocantins and Xingu Rivers in central Para was surveyed. In addition to the seven species known to exist in this area, the occurrence ofCallithrix argentata was confirmed. Sympatry between C. argentata and Saguinus roidas niger was also recorded, although mixed-species associations were not observed. The results of the study indicate that the distn"bution of C. argentata may be restn"cted to the relatively fiat lowland forest in the north of the region.

A survey of primates in central pará

Squirrel monkeys (Saimiri spp.) are widely distributed in the Amazon basin. This study describes the ecological and behavioral patterns of two social groups of S. sciureus in forests adjacent to the Tucurui hydroelectric reservoir in eastern Amazonia, including range size, activity budgets, and composition of the diet. The groups were monitored at Base 4 (group B4) and Germoplasma Island (group GI). Quantitative behavioral data were collected using instantaneous scan sampling to record behavior, substrate use, and height. Home ranges were delimited using a GPS to determine group position after each 50 m of movement. Home ranges were 75.0 ha for group B4 (39 members) and 77.5 ha for group GI (32 members). The use of vertical strata was well defined, with a marked preference for the middle and lower levels of the canopy. The activity budgets of both groups were typical of those of other squirrel monkeys and were dominated by foraging (B4 = 48.7 %; GI = 49.6 %), moving (both groups 28.9 %), and feeding (B4 = 14.6 %; GI = 12.4 %). Resting was rare (B4 = 3.5 %; GI = 2.6 %) and less common than social behavior (B4 = 4.3 %; GI = 6.4 %). The diet of both groups was dominated by plant material (B4 = 70.7 % of feeding records; GI = 71.4 %), which is in contrast with the more insectivorous diets recorded for Saimiri at other sites. Group GI spent more time foraging during the dry season, whereas group B4 spent more time in the rainy season when the consumption of fruit increased (significantly, in the case of group GI). The less insectivorous diet of these groups may be due to a number of factors, including the unique habitat configuration at the site and reduced hydrological stress due to the proximity of the reservoir.

Activity budget, diet, and use of space by two groups of squirrel monkeys ( Saimiri sciureus ) in eastern Amazonia

Habitat fragmentation has evaluated effects on parameters such as species diversity, population density, and behavioral patterns, as shown in other chapters in this volume, but there are as yet few data available on its influence on genetic variation in free-ranging primate populations (but see Pope, 1996, 1998). Loss of genetic variability and inbreeding depression are generally presumed to be the primary results of the fragmentation of continuous populations, although outbreeding depression may also be relevant in many cases (Templeton, 1986; Dudash and Fenster, 2000).

Effects of Habitat Fragmentation on the Genetic Variability of Silvery Marmosets, Mico argentatus

The white-fronted spider monkey, Ateles marginatus, is endemic to Brazilian Amazon between the Tapajos and Xingu Rivers, and is classified as endangered due primarily to habitat loss. This study presents data on the distribution and relative abundance of the species in the northwestern corner of its distribution, on the lower Tapajos River, centered on the 545,000 ha Tapajos National Forest (Flona Tapajos). Quantitative data were collected in line transect surveys at 14 sites, and confirmatory interviews were conducted at these, and a further four sites. The results indicate that A. marginatus is extinct or extremely rare at sites in the northern extreme of the study area, but is relatively widespread further south, except in very small fragments (<100 ha). While the present-day occurrence of A. marginatus is clearly affected by habitat fragmentation, the species’ original distribution appears to have been characterized by local lacunas, determined by factors relating to habitat quality. While hunting pressure does not seem to be a major threat at the present time, competition with a second atelid, Alouatta discolor, may have reinforced the effects of habitat disturbance in some areas, especially smaller fragments. Grouping patterns were typical of the genus, including an apparent female bias in the sex ratio of adults. Overall, the results indicate an ongoing decline in the occurrence of A. marginatus within the study area, local extinction, especially in smaller fragments, and an urgent need for the establishment of effective conservation measures.

Geographic distribution and population characteristics of the endangered white-fronted spider monkey (Ateles marginatus) on the lower Tapajós River in central Brazilian Amazonia.

Stephen F. Ferrari

Papers

Observation of Black-Capped Capuchins (Cebus apella) Feeding on an Owl Monkey (Aotus brumbacki) in the Colombian Llanos

A survey of primates in central pará

Activity budget, diet, and use of space by two groups of squirrel monkeys ( Saimiri sciureus ) in eastern Amazonia

Effects of Habitat Fragmentation on the Genetic Variability of Silvery Marmosets, Mico argentatus

Geographic distribution and population characteristics of the endangered white-fronted spider monkey (Ateles marginatus) on the lower Tapajós River in central Brazilian Amazonia.