Scientists from various disciplines have long been interested in animal behavior. Biologists trained in , 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 and 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 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 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 had previously killed, a spider begins weaving a web in which it hopes to trapa meal, and a tiny single-celled The innumerableways in which differentspecies ob- aquaticamoeba engulfs algae and bacteriaby tucking tain food truly reflect the phenomenal variation that in its cell membrane and surrounding the tiny prey. exists in animals' adaptive behavioral responses to Predators frequently invest time and energy in their environment. Consider the following scenario. locating,capturing, and consuming food items, or they On a clear day in the northwestern United States, a may take advantage of another individual's success sparrow hawk suddenly breaks out of its meandering and scavenge on already captured prey. And, on oc- flight, dives toward the ground, captures a small field casion, a predator may kill more than it needs at one mouse, and takes off in flight once again. Nearby, a time and either store uneaten food for later use in a coyote, a member of the "dog family" and close cache or simply leave it (Curio 1976). Red foxes will relativeto wolves and jackals,stands still, its tail slight- sometimes cache food in various locations to minimize ly elevated, its ears erect, its nose waving in the air, the risk of losing all of their food to other animals. and its piercing eyes fixed on something that has at- It is importantto stress that predators are not simp- tracted its attention. Suddenly, the coyote begins to ly being bloodthirsty,mean, or aggressive. True, there walk very slowly and quietly, attempting to conceal are "winners" and "losers" in the interactions be- its presence from potential food; it then stops, moves tween predatorsand prey, but even prey species need its head slightly, sniffs, and then rushes at the object fuel for survival that is acquiredby eating other living in which it had been keenly interested.The coyote then organisms.Basically, all living animalsfeed themselves bites its prey near the junction of its head and neck, because they need energy to keep theirbodies in work- shakes its head back and forth vigorously, and trots ing order. Even when an organism is asleep it needs off with a young ground squirrel dangling from its fuel for body growth and maintenance. The need for mouth. It settles down about 25 meters away and con- energy increases greatly during activity, and energy sumes its meal. that is required for finding, capturing, consuming, While all of this is happening, a pack of wolves con- eating, and digesting food must be replaced;energetic fronts a lone moose in the wilds of Canadaand, around expenses (costs) and deposits (benefits) must balance. a garbage dump in Florida, a Herring Gull steals food Those scientistswho study behaviorof predatorsare from a Laughing Gull as the latter bird takes flight. confronted with a set of problems that are enormous And, a few hours later acorss the world in South in scope. And, when the behavior of prey species is Africa, a cheetah explodes in a short and rapid sprint, considered, which must be done because a complete achieving speeds of up to 90 kilometers per hour in analysis requires considerationof all actors, the situa- pursuit of a Thomson's gazelle, a lion displaces a tions become extremely complex (Edmunds 1974; leopard from the carcassof a gazelle which the leopard Curio 1976; Eisenberg 1981).

336 THE AMERICAN BIOLOGY TEACHER, VOLUME-45, NO. 6, OCTOBER 1983 What are some of the possible aspects of predatory types. While some predatorsrely on speed, endurance, behavior that can be pursued scientifically?We can power, or brute strengthto captureprey, others satisfy study the evolution of predatory behavior and even their hunger by performing sequences of unique and comparewild and domesticatedrelatives (for example, specialized behaviors that are adapted for prey detec- wolves and dogs), compare different wild species and tion and capture (Curio 1976;Whitfield 1978;J. Owen determinehow, in their own way, they solve the same 1980). For example, many bats use echolocation or basic problem of getting food efficiently, analyze how radar to find prey, electric rays eat other fishes after environmentaldifferences influence hunting behavior they envelop and stun them with an electrical for the same and different species, and study the discharge, shrikesimpale prey on sharpbranches, and development of predatory behavior in young in- aardvarks are able to trap termites on their sticky dividuals. We can also ask questions about how tongues. Even Harbor seals may use echolocation predators find prey and what senses are used, why when foraging in murky water (Renouf and Davis predators select particular types of prey, how suc- 1982).Fishers, small carnivorousmammals that live in cessful differenttypes of predatorsare on various prey Canada and along the United States-Canadaborder, types, and how predatory behavior influences the are able to prey successfullyon heavily armored,prick- social organization and lifestyle of predatory animals. ly porcupines. They primarily attack the facial area Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 From a practical point of view, we can study food where there are no quills, and they are large enough habits and hunting behavior as they relate to conser- to inflict wounds but small and agile enough to jump vation and management of wild animal populations away, avoiding the slap of the porcupine's tail (Powell and with respect to how we can better meet the nutri- 1982). tional requirements of zoo animals. If prey is sighted and close by, a predatormay simply Because a comprehensive understanding of any rush the prey and hope to outrun it quickly. Cheetahs behavioralpattern requires analyses at many different hunt Thomson's gazelles in this manner, as do other levels of study, ranging from biochemical and carnivoreswhen chasing small rodents who are unable physiological experimentalresearch conducted under to seek refuge in a hole in the ground. If prey is de- carefully controlled laboratoryconditions to observa- tected by a faint odor, barely audible sound, or long- tional studies performed under field conditions, we range visual image, the predator must somehow get also must pay attention to such things as what parts closer to the prey before it begins its actual pursuit. of the brain are involved in predatorybehavior, what For many predators, very slight movements by prey, makes animals hungry in the first place, why in- which are barely sensed by humans, are sufficient to dividuals show cycles of eating and rest, and what elicit orientation and approach. Prey detection also is kinds of physiological and anatomical adaptations aided by the formationof a "searchimage." The pred- predators show that are related to food habits (Ewer ator is "tuned in" to certain stimuli that previously 1973;Curio 1976;Brown 1977;Whitfield 1978). For ex- were associated with prey (Curio 1976). Typically, a ample, many predators possess structures that are predator will stalk its potential, but distant, meal by specialized for feeding behavior such as teeth that are slowly and quietly moving until it is within range used in biting, tearing, and crushing, strong jaw where a chase and attack are more likely to succeed muscles, hooked beaks, or sharp claws or talons. than if it simply ran toward the prey when it was first Cheetahs, the fastest of land mammals, have flexible detected. And, of course, the predator itself gives off backbones that allow them to spring off the ground cues that can be used by the prey to its own advantage. during high-speed chases, during which they attempt The precapture phases involved in a predatory se- to overtake slower running prey. However, cheetahs quence often take a lot of time and energy. Indeed, can run only short distances, usually under about 350 some species hunt by "speculation," while others meters, because their back muscles become rapidlyex- merely sit and wait to ambush prey, or build webs in hausted. Various snakes such as coachwhips, rat- which to trap prey. Some octopi will regularly close tlesnakes, and rosy boas also show morphological their webs over rocks or algae hoping to find prey. adaptations in spinal musculature that are associated They then feel under the web to see if prey has been with different modes of hunting (Ruben 1977a,b). taken. If not, the octopus simply continues moving about (Curio 1976). The predatorylarvae of the water Modes of Hunting: Adaptations for scavenger beetle, a poor swimmer, will sit on vegeta- Detection, Capture, and Killing tion and wait for tadpoles to swim by, and then am- bush them (Formanowicz, Bobka, and Brodie 1982). A major set of questions deals with the incredibly Other species such as coyotes, hyenas, African wild diverse ways in which predatorssearch for food, detect dogs, lions, vultures, and magpies may reduce the it, and then capture and kill prey after it has been costs of hunting by feeding on prey killed by other located. A successful predator must be able to adapt animals, by eating rotten meat, or by finding prey that rapidly to changing and different conditons and prey have died due to causes other than predation (figs. 2

PREDATORY STRATEGIES 337 and 3). It is possible that predators are mnoreattracted instances, young, old, weak, and sick prey are singled to animals that died violent deaths, such as by preda- out and pursued rather than healthy individuals who tion, rather than to prey that died due to illness or star- would pose more of a threat to the predator, and con- vation (Bullard 1982). sequently decrease the chances for success (see Curio Still other predators mimic, or look like, another 1976 for review). Conspicuous individuals within a species that is harmless to potential prey. This is called population may also be subjected to heavier predation aggressive or Peckhammian mimicry, named after E.G. than those that are less conspicuous. For instance, Peckham, who introduced the concept (for review see predatory birds hunting around industrial centers of Wickler 1968 and D. Owen 1980). For example, the England are more likely to prey upon dark moths that predatory zone-tailed hawk often glides along with alight on light trees and light moths that land on dark vultures. The hawk takes advantage of its concealment backgrounds, than on moths that blend in with the among the vultures and will dive suddenly from the substrate. group to take prey by surprise. Female fireflies (actually Local wind conditions, the amount of available light, beetles) of the genus Photuris will mimic the flash pat- the presence of trees and ground cover, snow depth, tern of females of the genus Photinus and attract their temperature, and moisture can also affect prey detec- victims. When a Photinus male alights alongside a tion, selection, and hunting success (Curio 1976; Wells Photuris and Bekoff 1982). These variables can differ from one female, he is eaten! What was taken to be a Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 potential mate actually was a predator! location to another, and it is for this reason, among Assuming that a predator does capture its own meal, others, that it is difficult to make general statements still more time and energy are needed to handle, kill, about how successful a specific predator is in acquir- eat, and digest the prey. Small mammals frequently ing food. Other factors that need to be considered in- are pinned to the ground by coyotes, foxes, and jack- clude the ages of the predator and the prey, how ex- als, and then a killing bite, aimed at the head and neck, perienced they are with each other's modes of hunt- is administered (Ewer 1973.) Violent side-to-side shak- ing and avoidance patterns, how hungry the predator ing of the head often accompanies the bite, during is, how healthy and physically fit each of the actors which time the predator's teeth may sink in deeper, is, and how many hunters and prey are involved. the neck of the prey may be broken, nerves and blood The comparative success rates listed here are mere- vessels destroyed, and the prey disoriented. The prey ly representative guidelines, and as mentioned above, is then consumed. Larger prey are typically more dif- variation is the rule rather than the exception. In one ficult to catch, and a group effort may be required (see study of coyotes (Wells and Bekoff 1982), ground squir- below). rels were captured 41% of the times they were hunted, whereas coyotes were successful in capturing voles on Prey Selection and Hunting Success 19% of the hunts during which they were sought. Because predatory behavior often takes a lot of time Among predatory mammals living on the Serengeti and energy, one would expect that a wise predator Desert, where ungulates such as Thomson's gazelles, would make every effort to reduce the costs of hunt- impalas, zebras, and wildebeest are the major prey ing by selecting prey that are less likely to get away. species, estimated success rates are as follows (Bertram That is, the predator should try to maximize energy 1979): cheetahs 37-70%; leopards 5%, lions 15-30%; In one intake and minimize costs of hunting. Indeed, in many spotted hyenas 35%; and wild dogs 50-70%.

FIGURE 2. Different species often feed together on carrion. Here, a coyote and a magpie are scavenging on elk carrion in nor- thern Yellowstone National Park, Lamar Valley, near Gardner, Montana. Coyotes on- ly very rarely kill the ungulates (deer, prong- horn elk, moose) on which they feed (photograph by William E. Ervin). study of a pack of 15-16 wolves hunting moose on Isle poises, wolves, and other social carnivores may at- Royale National Park (Michigan), on only six of 120 at- tempt to herd potential prey. The group spreads out tempts (5%) were moose killed (Mech 1970). Other data over a wide area and the individuals in the middle of indicate that largemouth bass are successful on about the hunting group approach the prey more slowly than 94% of their hunts, American kestrels successfully kill individuals at either end. The prey is eventually sur- rodents or insects on approximately 33% of their at- rounded, and escape is difficult. Predatory groups of tempts, and osprey preying on fish succeed on about wolves, lions, or wild dogs may also drive prey toward 80-96% of their efforts (Curio 1976). It is important to other group members who then ambush it. Group stress that it is to the predator's advantage not to kill hunting is not always cooperative. Two or more in- all prey or breeding adults in a population. Indeed, dividuals may each be trying to feed themselves they never do. In fact, it has been suggested that un- without paying any attention to the behavior of other successful predation is a necessary condition for the group members. evolution and elaboration of antipredatory strategies While some species such as lions, wild dogs, and (Vermeij 1982). wolves tend to hunt mainly in groups, others hunt singly or with other group members, often switching Social Organization and Hunting between the two modes rapidly, depending on the Many different species live in groups. Among the prey that is being confronted. For example, when spot- Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 different reasons given for the existence of animal ted hyenas hunt Thomson's gazelles or wildebeest, groups, many involve food. For example, grouping one to three individuals usually are involved. When may be an adaptation for getting food, defending it, hyenas hunt zebras, up to 27 animals can partake in or for protection against predators (Crook 1970; the hunt. An average of about 11 hyenas usually hunt Kruuk 1972; Curio 1976; Eisenberg 1981). zebras (Kruuk 1972). Many predators, especially mammals, feed on live, Success rates and group hunting are clearly mobile prey that is larger and/or faster than associated. When lions hunt Thomson's gazelles, a themselves. When these predators hunt in pairs or in single lion is successful about 15% of the time. When larger groups, success rates tend to increase, and all two to four lions are involved, the success rate more individuals benefit from the joint effort. Often, hunt- than doubles to about 32%. A similar trend is observ- ing groups consisting of more than two individuals are ed during lion-wildebeest encounters (Schaller 1972). no more efficient than pairs of animals (Schaller 1972; Likewise, pairs of golden jackals hunting Thomson's Curio 1976). In many species, groups are made up of gazelle fawns are more than four times (67%) as suc- related individuals (an extended family; fig. 4). cessful as single jackals (16%) (Wyman 1967). Therefore, kin are helping one another either in the Spotted hyenas also benefit from group hunting acquisition or defense of food. (Kruuk 1972). When a single hyena chases and over- When two or more predators, usually belonging to takes a wildebeest calf and then is attacked by the calf's the same species, attempt to find and hunt prey, the mother, the hyena never kills the calf. But, when two process is known as communal or group hunting (see or more hyenas are attacked by a single wildebeest Curio 1976 for review). When each individual pays at- mother, they always are successful in getting the calf. tention to the behavior of other group members, The female wildebeest can only deal with one hyena cooperative hunting occurs. For example, sharks, por- at a time, leaving her calf vulnerable to the other

fa~~~~~~~~~~~~~~~~~~~~~~~o

FIGURE 3. One nubian and two hooded vultures scavenging on a water buffalo car- cass in Samburu Game Reserve, northern _ Kenya (photograph by William E. Ervin). _ PACK PEDIGREE:1977-1983

MOTHERI left pack| MOTHER2 x x 7 x _ _ _ _ FATHERI | disappeared FATHER2

? { d" Helper(H77)---Dispersed ? -' Pups 9 Roamer -Ma.ted with locold"and dispersed 3 99, 4 d j caHelper (died) (All tagged) 9 Roamer -Dispersed 3 99 3cc craHelper (B21) FATHER Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 (All tagged)L 9 Helper ( BB) Dispersed

(1Alltagged ) -.C Helper (ci"80)--oDispersed -d Helper(d'81) 3 9?1 Id 9 Helper(B36) (All tagged) L9 Roamer (B31)- -Dispersed cra(B43) - 4 99, 2 d"! J (B48) -> (All tagged) 9 (B46) o L9 XX V

1977 1978 1979 1980 1981 1982 1983 winter

FIGURE4. Social groups often are made up of geneticallyrelated individuals. This figure presents a pedigree for a pack of coyotes observed from 1977-1983in the Grand Teton National Park, outside of Jackson,Wyoming (Bekoffand Wells 1982). Young of each year that are not accountedfor either dispersed or died before they were about nine months of age. After the originalpack mother left the group in late 1980, a new, and unrelated female joined the pack and mated with the original pack father in 1981. Then, after he left the pack in spring 1981, his son, male helper B21, mated with the new female in 1982 and 1983. The new pack mother was the only unrelated coyote to join the pack in six years. hyena's attacks. Likewise, one hyena is successful Desert, spotted hyenas are rarely observed in packs. about 18%of the time when it hunts wildebeest calves Packsthat do occur are small, usually consisting of one whose mothers do not attackit, but in the same situa- female and several males. However, for spotted tion, two hyenas have a success rate of about 32%. hyenas living in the NgorongoroCrater, packs typically Groupliving may also be importantfor food defense. are larger, consisting of several males and females. For example, in one study conducted in northern These variationsin organizationalpatterns seem to be Wyoming in the Grand Teton National Park (Bekoff related to differences in food supply in the two areas. and Wells 1982), it was found that when coyote pack On the Serengeti, food often is absent for long periods members (fig. 4) were successful in defending elk car- of time and the hyenas have to keep up with moving rion from intrudingnonpack coyotes, an averageof 2.6 herds of their herbivorousprey. Futhermorethere are pack members was involved in the interactions.When few zebras, for which large groups of hyenas are need- pack members lost and intruders were able to remain ed for successful predation, and an abundance of on the pack's territory and gain access to their food Thomson's gazelles, which can be hunted successful- resources, only 1.3 pack members partook in the ly by only one to three individuals. encounters. In coyotes, differenttypes of social groups have been observed, ranging from single individuals, to mated Food Resources and Social Organization pairs, to packs. As noted above, pack formation ap- pears to be an adaptationfor the Food resourcesalso can influencethe social organiza- defense of food. Packs typically consist of a mated pair and their tional patterns of predators (Kruuk1975; Packard and nondispers- ing and nonbreeding offspring, although Mech 1980; Bekoff and Wells 1982). On the Serengeti on occasion,

340 THE AMERICAN BIOLOGY TEACHER, VOLUME 45, NO. 6, OCTOBER 1983 TABLE2. Ways in which food resources and wolf population densities can influence social behavior, organization, and reproductive success.

High density/Highresources High density/Lowresources Dense, stable population Declining population Intermediate pack conflict High pack conflict Dispersers unlikely to acquire territory Dispersers unlikely to acquire territory Low proportion of breeding females High proportion of breeding females due to low produc- tivity and high mortality of subordinates and solitary wolves

Lowdensity/High resources Lowdensity/Low resources Increasing population Sparse, stable populations Low probabilityof pack conflict Low probabilityof pack conflict Dispersers most successful at establishing territories Dispersers may establish territoriesbut not raise pups due Breeders highly successful to malnutrition High proportion of breeding females because dispersers Intermediate to low proportion of breeding females Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 establish new packs because dispersers unlikely to breed (Adaptedfrom Packard and Mech1980)

a strangermay be incorporatedinto an alreadyexisting learn about ourselves, and comparative studies un- pack (Bekoffand Wells 1982).The observed differences doubtedly will help to shed some light on behavioral in coyote social organizationseem to be related to food adaptations of human animals as well. availability, winter especially during (Camenzind1978; Acknowledgment-Someof my researchhas been supported Bowen 1981;Bekoff and Wells 1982).On our study area by The National Institutes of Mental Health, The National outside of Jackson, Wyoming there is a highly signifi- Science Foundation, The Harry Frank Guggenheim Foun- cant positive relationship between group size and the dation, The John Simon GuggenheimMemorial Foundation, abundance of elk carrion (the elk were not killed by and The University of Colorado.I am gratefulto all of these coyotes); where elk carrionis sources and to all students who have worked on my research abundant, coyote group projects, especially Dr. Michael C. Wells. Thomas Daniels size is larger. Available data indicate that winter food and JenniferFewell provided comments on an earlier draft supply is the major ecological variable influencing of this paper and Jeanie Cavanagh kindly typed the coyote social organization. manuscript. The social behavior and organization of wolves also are influenced by the interactionbetween the density References of the wolf population and its food resources (Packard ARMITAGE,K.B. 1981. Sociality as a life-history tactic of and Mech 1980). Reproductive success may also vary. ground squirrels. Oecologia48:36-49. These relationships are outlines in table 2. BEKOFF,M. 1977. Quantitative studies of three areas of classicalethology: Socialdominance, behavioral taxonomy, and behavioralvariability. In Hazlett,B.A. (ed.) Quantitative Summary methodsin thestudy of animalbehavior. New York:Academic Press. The study of predators makes for fascinating BEKOFF,M., DIAMOND,J., and MITTON,J.B. 1981. Life- analyses of animal behavior. We learn not only about history patterns and sociality in canids: Body size, how different and very diverse animals satisfy their reproduction, and behavior. Oecologia50:386-390. hunger, but also how anatomy, physiology, ecology, BEKOFF,M., and WELLS,M.C. 1982. Behavioralecology and behaviorare all tied together. Perhapswe can learn of coyotes: Socialorganization, rearing patterns, space use, and resource defense. Zeitschrift fiur Tierpsychologie a lot about ourselves as well. Humans also have to eat, 60:281-305. and it is interestingto note that many aspects of human BERTRAM,B.C.R. 1979. Serengetipredators and their social social organization and ecology resemble those of car- systems. In Sinclair, A.R.E., and Norton-Griffiths, M. nivores rather than those of other primates (Kruuk (eds.) Serengeti:Dynamics of an ecosystem.Chicago: Univer- 1975). For example, human group size and organiza- sity of Chicago Press. BOWEN,W.D. 1981.Variation in coyote socialorganization: tion in primitive hunters may be related to prey type The influence of prey size. CanadianJournal of Zoology and hunting mode. 59:639-652. Of course, more data are needed, but it should be BROWN,L. 1977. Birdsof prey: Their biology and ecology. New stressed that comparativeanalyses of behavior are not York: A & W Publishers, Inc. only useful for extending our knowledge of behavioral BULLARD,R.W. 1982.Wild canid associationswith fermen- tation products. I&EC ProductResearch & Development diversity in nonhuman animals; we also have a lot to 21:646-655.

PREDATORY STRATEGIES 341 CAMENZIND,F.J. 1978. Behavioralecology of coyotes on OWEN, D. 1980. Camouflageand mimicry.Chicago: Univer- the NationalElk Refuge, Jackson,Wyoming. In Bekoff,M. sity of Chicago Press. (ed.) Coyotes:Biology, behavior, and management. New York: OWEN, J. 1980. Feedingstrategy. Chicago: University of Academic Press. Chicago Press. CROOK,J.H. 1970. The socio-ecologyof primates.In Crook, PACKARD,J.M., and MECH,L.D. 1980.Population regula- J.H. (ed.) Socialbehavior in birdsand mammals:Essay on the tion in wolves. In Cohen, M.N., Malpass,R.S., and Klein, social ethologyof animalsand man. New York: Academic H.G. (eds.) Biosocialmechanisms of populationregulation. New Press. Haven, Conn.: Yale University Press. CURIO, E. 1976. The ethologyof predation.Berlin and New POWELL,R.A. 1982. The fisher: Life history, ecology,and York: Springer-Verlag. behavior.Minneapolis, Minn.: University of Minnesota DEWSBURY,D.A. 1972. Patternsof copulatorybehavior in Press. male mammals. QuarterlyReview and Biology47:1-33. RAUTENBACH,I., and NEL, J.A.J. 1978. Coexistence in EDMUNDS, M. 1974. Defence in animals. New York: Transvaal carnivora. Bulletin of the CarnegieMuseum of Longman, Inc. NaturalHistory 6:138-145. EISENBERG,J.F. 1981. Themammalian radiations: An analysis RENOUF,D., and DAVIS, M.B. 1982. Evidence that seals of trends in evolution,adaptation, and behavior.Chicago: may use echolocation. Nature300:635-637. University of Chicago Press. RUBEN.J.A. 1977a. Morphologicalcorrelates of predatory EWER,R.F. 1973.The carnivores. Ithaca, N.Y.: CornellUniver- modes in coachwhip (Masticophisflageullum) and rosy boa sity Press. (Lichanuraroseofusca). Herpetologica 33:1-6. FORMANOWICZ,D.R. Jr., BOBKA,M.S., and BRODIE, . 1977b. Some correlates of cranial and cervical Downloaded from http://online.ucpress.edu/abt/article-pdf/45/6/334/41013/4447716.pdf by guest on 27 September 2021 E.D. 1982. The effect of prey density on ambush-site morphology with predatory modes in snakes. Journalof changes in an extreme ambush-type predator. American Morphology152:89-100. MidlandNaturalist 108:250-255. SCHALLER,G.B. 1972. TheSerengeti Lion Chicago: Univer- GOULD, S.J. 1977. Ontogenyand phylogeny.Cambridge, sity of Chicago Press. Mass.: Harvard University Press. STEARNS,S.C. 1976. Life history tactics: A review of the HINDE, R.A. 1982. Ethology:Its natureand relations with other ideas. QuarterlyReview of Biology51:3-47. sciences.New York: Oxford University Press. THORPE,W.H. 1979. The originsand rise of ethology.New HORN, H.S. 1978. Optimal tacticsof reproductionand life- York: Preager. history. In Krebs,J.R., and Davies, N.B. (eds.) Behavioural TINBERGEN,N. 1951.The study of . New York:Ox- ecology: An evolutionaryapproach. Sunderland, Mass.: ford University Press. Sinauer Associates. TINBERGEN,N. 1963. On aims and methods of ethology, KLEIMAN,D. G., and EISENBERG,J.F. 1973. Comparisons Zeitschriftfur Tierpsychologie20:410-433. of canid and felid social systems from an evolutionary VERMEIJ,G.J. 1982. Unsuccessful predationand evolution. perspective. AnimalBehaviour 21:637-659. AmericanNaturalist 120:701-720. KRUUK,H. 1972. Thespotted hyena. Chicago: University of WELLS,M.C., and BEKOFF,M. 1982. Predation by wild Chicago Press. coyotes:Behavioral and ecologicalanalyses. Journal of Mam- . 1975. Functional aspects of social hunting by car- malogy63:118-127. nivores. In Baerends,G., Beer, C., and Manning, A. (eds.) WESTERN,D. 1979. Size, life history and ecology in mam- Functionand evolution in behaviour:Essays in Honourof Pro- mals. AfricanJournal of Ecology17:185-204. fessorNiko Tinbergen. New York:Oxford University Press. WHITFIELD,P. 1978. The hunters.New York: Simon and LORENZ,K.Z. 1981. Thefoundations of ethology.New York: Schuster. Springer-Verlag. WICKLER,W. 1968. Mimicry.New York: McGraw-Hill. MacARTHUR,R.H., and WILSON,E.O. 1967. Thetheory of WITTENBERGER,J.F.1981. Animal social behavior. Boston: islandbiogeography. Princeton, N.J.: Princeton University Duxbury Press. Press. WYMAN,J. 1967.The jackalsof the Serengeti.Animals (Lon- MECH,L.D. 1970. Thewolf: The ecology and behavior of an en- don) 10:79-83. dangeredspecies. New York: Doubleday.

Communication Signals .. . from p. 309 DARWIN, C. 1871. Thedescent of man. New York:Thomas ___ . 1967. Aggression and social structure in iguanid Y. Crowell and Co. lizards. In (Milstead, W.W. (ed.) Lizardecology: A syposium. ECHELLE,A.A., ECHELLE,A.F., and FITCH,H.S. 1971. Columbia: University of Missouri Press. A comparativeanalysis of aggressivedisplay in nine species . 1977. The aggressive displays of three species of Costa Rican Anolis. Herpetologica27:271-288. of South American iguanid lizards of the genus Tropidur- FERGUSON, G.W. 1971. Variation and evolution of the us. Herpetologica33:385-389. pushup display of the side-blotchedlizard genus Uta (Ig- . 1978a. Ritualistic social behaviors in lizards. In uanidae). SystematicZoology 20:79-101. Greenberg, N., and MacLean, P.D. (eds.) Behavior and GIBBONS,J.R.H. 1979. The hind leg pushup display of the neurology of lizards. Rockville, Md.: National Institutes of Amphibolurusdecresii complex (Lacertilia: Agamidae). Copeia Mental Health. 1979:28-40. I_ . 1978b. Comparative display behavior in the ge- JENSSEN,T.A. 1978.Display diversity in anolinelizards and nus Sceloporus(Iguanidae). Contributions in Biologyand Ge- problemsof interpretation.In Greenberg,N. and MacLean, ology. Milwaukee Public Museum. P.D. (eds.) Behaviorand neurology of lizards.Rockville, Md.: -. 1982. The aggressive displays of iguanine liz- National Institutes of Mental Health. ards. In Burghardt, G.M., and Rand, A.S. (eds.) Iguanas JENSSEN,T.A., and HOVER,E. 1976. Display analysis of of the world:Their behavior, ecology, and conservation.Park the signaturedisplay of Anolislimifrons (Sauria: Iguanidae). Ridge, N.J.: Noyes Publications. Behaviour57:227-240.

342 THE AMERICAN BIOLOGY TEACHER, VOLUME 45, NO. 6, OCTOBER 1983