Scientists from various disciplines have long been interested in animal behavior. Biologists trained in ethology, ecology, physiology, anatomy, and genetics have jointly approached problems of mutual interest and have provided unique, fascinating, and com- prehensive explanations concerning the ways in which Prelatory Strategies diverse animals do the things they do. This article will briefly discuss the view that behavior may be thought of as a phenotypic adaptation that can be quantitatively and Behavioral studied from comparative and evolutionary perspec- tives, and then consider in a bit more detail the ways in which predatory animals, especially mammals, Diversity satisfy their need for food. Marc Bekoff Behavior as A Phenotypic Structure Niko Tingergen, who shared the 1973 Nobel Prize Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 for Biology and Medicine with Konrad Lorenz and Karl von Frisch for contributions to the science of ethology, often stressed that a complete analysis of any behavior ultimately required consideration of at least four ma- jor areas: evolution, adaptation, causation, and development (Tinbergen 1951, 1963; Hinde 1982). Of course, this is a tall order, given the difficulty of rigorously studying different behavioral patterns. But in the final analysis, these data are necessary for generating a comprehensive perspective on what an animal is doing, how it goes about achieving a par- ticular goal, and why it is engaged in one activity and not another. Another idea of great historical significance was the recognition by Charles Otis Whitman, Oskar Heinroth, and Konrad Lorenz that behavior could actually be thought of as a structure or a phenotype, and as such, was subject to natural selection. Therefore, behavior could be studied in a comparative manner, as one might study anatomical structures (Thorpe 1979; Lorenz 1981). For example, behavioral phenotypes have been used in taxonomic endeavors both to clarify relationships that were not well-defined and to substantiate taxonomic schemes based on more tradi- tional approaches in which morphological characteristics were used to assess affinities among dif- ferent species (Dewsbury 1972; Bekoff 1977). Life-History Approaches to Social Behavior The recognition that behavioral responses could be viewed as phenotypic adaptations to various en- vironmental conditions and that many behavioral pat- Marc Bekoff is a professor in the University of Colorado's Depart- ment of Environmental, Population, and Organismic Biology, and terns can be modified to meet changing demands of holds an A.B. degree in anthropology and a Ph.D. degree in the environment has opened the door for a plethora ethology, both from Washington University. Bekoff is a former U.S. of fascinating studies concerning the ways in which Secretary to the International Ethological Congress, a 1981 John Simon Guggenheim Memorial Foundation Fellow, and serves on diverse species achieve similar goals by performing a the editorial board of Animal Behaviour and Zeitschrift filr Tier- dazzling array of behaviors. Furthermore, the com- psychologie.His previous studies have concerned the social behavior parative and evolutionary study of behavior has stress- and behavioral ecology of coyotes, and he is currently studying Even- ing Grosbeaks. Bekoff was a state-ranked tennis player and was 1982 ed that behavior is tightly linked both to morphology Colorado State Champion in bicycle cyclocross. and physiology, often in highly predictable ways 334 THE AMERICAN BIOLOGY TEACHER, VOLUME 45, NO. 6, OCTOBER 1983 LIFE-HISTORY TRAITS AND BEHAVIOR Gestation Period Birth Weight FIGURE1. Studiesin which the relationships LitterSize between life-historytraits and behavior are Sex Ratio analyzed consider a large number of Age at Weaning/ Independence variables associated with reproduction, __ __ _Age at Sexual Maturity -N- physicaldevelopment, body size, and social I Reodut I Age WhenFirst Reproducesv behavior.In some cases, animalsdo not mate Reproucton 1 Fecundity when they first reach sexual maturity. Longevity RI = reproductiveindex, RE = reproductive Type of Pair-bond effort, SRE = specific reproductive effort, Tt BW = birth weight, LS = litter size, and =Typeof MatingSystem MFW = minimum female weight. RI RI=BW(lyoung)/MFW represents the effort by a single female to RE=BWx LS bring one young to term relative to her SRE=BWxLS/MFW(RE/MFW) weight, RE represents the total resources Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 allocatedto bringinga litterto termirrespec- Physical Development Age at Eye-opening/ Tooth Eruption tive of female weight, and SRE represents the total resources allocated to reproduction Weight relative to female weight (Armitage1981). l Body Size Length "Level"of Sociality (Variability) Social Behavior HuntingMethod(s) (Western 1979; Bekoff, Diamond, and Mitton 1981; will concentratebriefly on a few aspects of predatory Eisenberg 1981). Such life-history analyses have behavior, mainly in mammals, to show how different demonstratedthat often there is a common threadlink- species go about gathering the energy needed for ing a wide varietyof closely or distantlyrelated species growth, body maintenance, and reproduction (for (Armitage 1981; Bekoff, Diamond, and Mitton 1981; reviews see Curio 1976;Whitfield 1978;J. Owen 1980; Eisenberg 1981). Eisenberg 1981). The comparative method is useful Basically, a life-historytactic or strategy refers to "a because it highlights similaritiesand differencesin the set of coadapted traits designed, by naturalselection, ways in which diverse species solve food-related to solve particularecological problems" (Stearns1976, problems. p. 4). Among many mammals, for example, important The life-history approachis also useful for organiz- associations have been detected among various traits ing our thoughts because it allows us to make predic- such as body size, patterns of reproductivebehavior, tions about the typical hunting behavior that would behavioral and physical development, and social be expected in species differingin body size, reproduc- behavior(fig. 1; table 1). The relationshipsamong these tive strategies, developmental patterns, and social charactersfrequently are discussed with respect to r- organization.For example, among canids (membersof and K-selection (MacArthurand Wilson 1967; Wit- the "dog" family, Canidae), there are associations tenberger1981). Selection under conditions of density- among (relatively)large body size, group living, and independent mortality usually is referred to as r- group coordinated hunting (Bekoff, Diamond, and selection whereas selection under conditions of Mitton 1981), undoubtedly adaptations for procuring density-dependent mortalityis frequently referredto largeprey in species such as wolves, Africanwild dogs, as K-selection.Although these terms are ratheruseless and dholes of India (Kleiman and Eisenberg 1973). in and of themselves (Horn 1978),careful comparative Social species also tend to show diurnal activity pat- consideration of the general suites of charactersthat terns whereas relatively smaller solitaryhunters such are associated with each type of selection (table 1) is as red foxes and bat-eared foxes are more nocturnal useful for developing general models and testable (Rautenbachand Nel 1978). Futhermore,in canids in hypotheses aboutthe relationshipbetween variouslife- which a group effortis requiredto capturemobile prey, history tactics and behavior. It is important to pack members usually are genetically related (the remember that we are talking about trends, and not group actually is an extended family) and food is absolute laws of association. shared among adults and between adults and young animals who are slow to develop independence and Predatory Behavior who may stay with the group for a few years. Given this highly abbreviatedbackground, I now PREDATORY STRATEGIES 335 TABLE 1. Some correlates of extreme r- (density-independent mortality) and K- (density-dependent mortality) selection. r-selection K-selection variable habitat fairly constant habitat many offspring (large prenatal reproductive effort) fewer offspring (smaller prenatal reproductive effort) low postnatal parental investment in each offspring higher postnatal parental investment in each offspring high infant mortality lower infant mortality small body size larger body size rapid development slower development early reproduction (short generation time); high fecundity delayed reproduction (longer generation time); lower fecundity short life (usually < 1 year) longer life (usually > 1 year) semelparity (single reproduction) iteroparity (repeated reproduction) mortality often catastrophic, non-selective, and mortality is more steady, more selective, and density-independent density-dependent Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 low levels of dispersal higher levels of dispersal social behavior is not well-developed more highly developed social behavior (coordinated (schools, aggregations) groups or packs in which there is cooperation among individuals) Notes:(see MacArthur& Wilson 1967; Stearns 1976;Gould 1977;Horn 1978;Wittenberger 1981). The suites of charactersshould be viewed in a comparativemanner with the understanding that they represent generalizations,and not hard-and-fastrules. The Diversity of Predatory Behavior