A. H. Harcourt's research while affiliated with University of California, Davis and other places

Publications (105)

Article
Homo sapiens phylogeography begins with the species' origin nearly 200 kya in Africa. First signs of the species outside Africa (in Arabia) are from 125 kya. Earliest dates elsewhere are now 100 kya in China, 45 kya in Australia and southern Europe (maybe even 60 kya in Australia), 32 kya in northeast Siberia, and maybe 20 kya in the Americas. Huma...
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Non-flying mammals are assumed to have reached oceanic islands by raft from islands of water-edge vegetation. From this hypothesis we can infer that oceanic islands should contain a greater proportion of water-edge species than do continental islands. Without a good sample of mammalian fauna on oceanic islands, we test an altered version of this pr...
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In this innovative, wide-ranging synthesis of anthropology and biogeography, Alexander Harcourt tells how and why our species came to be distributed around the world. He explains our current understanding of human origins, tells how climate determined our spread, and describes the barriers that delayed and directed migrating peoples. He explores th...
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Rivers border the geographic distributions of primate taxa, but the extent to which the rivers are effective barriers is debated. We here provide the first statistically substantiated analysis of the role of rivers as barriers to the distribution of primates in west and central Africa, as judged by the coincidence of the edge of distributions of fo...
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Habitat loss and fragmentation are two of the main threats facing wildlife. The species at risk in small fragments are not a random subset of the original community. Understanding the biology behind the distinction between species at risk and more persistent species should help inform conservation efforts. We attempted to identify risky traits in a...
Book
Cambridge Core - Animal Behaviour - Gorilla Biology - edited by Andrea B. Taylor
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It has long been suggested that species might exhibit their highest densities at the centre of their geographic range and decline in density towards their range limits. If true, this pattern would have important implications for ecological theory and for conservation management. However, empirical support for this pattern remains equivocal. Further...
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T. M. Anderson et al. report that wolves of the northwestern forest in North America are dark in comparison to the wolves of the tundra (“Molecular and evolutionary history of melanism in North American gray wolves,” Reports, 6 March, p. [1339][1]). Anderson et al. suggest in passing that the
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We examined latitudinal gradients in central value and diversity of body mass of primates to increase understanding of the Forster effect (decrease in taxonomic diversity with increasing latitude) and the Bergmann effect (increase of body mass with latitude). Data are from the literature. We used species’ median body mass of females and mid-latitud...
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Under some circumstances dominant females in social groups of primates start to breed significantly earlier in life than do subordinate ones, produce significantly more offspring per year, and mate significantly earlier in the breeding season, if there is one. Thus, competition appears to influence fertility. Observations that dominant individuals...
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Primates are an extraordinarily well-known tropical forest, mammalian taxon. We investigated potential modes of niche separation in primates by identifying sympatric species with putatively similar niche characteristics and assessing potential competition using data gleaned from an extensive literature review. We defined competing species-pairs as...
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It has been argued for nearly two decades that lemurs' low basal metabolic rate (BMR) by comparison to other primates is an adaptation to Madagascar's unpredictable climate. However, data from two recently published studies show that it is not just lemurs, but all strepsirrhines (the Suborder to which lemurs belong), that have low metabolic rates b...
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Emerging infectious diseases threaten a wide diversity of animals, and important questions remain concerning disease emergence in socially structured populations. We developed a spatially explicit simulation model to investigate whether—and under what conditions—disease-related mortality can impact rates of pathogen spread in populations of polygyn...
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Over the last 20 years the population of gorillas in the Virunga Volcanoes has halved from about 450 to around 225 animals. Its density and biomass have also dropped, as has the size of breeding units and the number of females per male within those units. The reproductive rates of the females appear to have remained fairly constant, however, althou...
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Societies develop as a result of the interactions of individuals as they compete and cooperate with one another in the evolutionary struggle to survive and reproduce successfully. Gorilla society is arranged according to these different and sometimes conflicting evolutionary goals of the sexes. In seeking to understand why gorilla society exists as...
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Science is fairly certain that the gorilla lineage separated from the remainder of the hominoid clade about eight million years ago,2, 4 and that the chimpanzee lineage and hominin clade did so about a million years after that.1, 2 However, just this year, 2007, it was discovered that although the human head louse separated from the congeneric chim...
Article
Aim  To describe rarity and elucidate its biology in a tropical mammalian order, the Primates.Location  Africa, Central and South America, Asia, Madagascar.Methods  A review of the literature, with some additional analyses using data from the literature. A variety of definitions of rarity are used in order to describe it and to investigate its biol...
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The amount of time taken to copulate varies enormously among mammals. Because copulation likely exposes animals to an increased risk of predation, and uses time and energy that could be spent on foraging, smaller mammals (which are vulnerable to more predators and have a shorter time-to-starvation than larger mammals) should spend less time copulat...
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Baker & Bellis (1988) suggest that the high numbers of deformed sperm in ejaculates of many mammalian species are produced to facilitate the formation in the female’s reproductive tract of copulatory plugs, objects whose function is to inhibit the passage of the sperm of males who mate subsequently with the same female. I submit that currently avai...
Article
Most forest fragments in which research is currently conducted are an order of magnitude too small to save most primate species in the long term, or indeed to save any other large-bodied mammal of equally poor dispersal ability (Brooks & Balmford 1996; Laurance & Bierregaard 1997; Soulé & Sanjayan 1998; Cowlishaw 1999; Chiarello 2000; Peres 2001; H...
Article
One hundred twenty-five years ago, in The Descent of Man and Selection in Relation to Sex,1 Charles Darwin proposed the theory of sexual selection, as distinct from natural selection, to explain why, in some species, males have such magnificent ornaments and, in other species, such impressive weapons. He suggested two processes, which we now term f...
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Aim Across a wide variety of organisms, taxa with high local densities (abundance) have large geographical ranges (distributions). We use primatology's detailed knowledge of its taxon to investigate the form and causes of the relationship in, unusually for macroecological analysis, a tropical taxon. Location Africa, Central and South America, Asia,...
Article
If we lack data on the biology of rare species, then understanding of the biology of rarity will be incomplete at best, biased at worst. However, the extent of potential under-study is mostly unknown. We therefore ask for primates, one of the better known orders of mammals, whether data are lacking on rare species. The measure used is published dat...
Article
Aim Rare species are reported to be specialized. However, rare taxa are usually less studied than are common taxa. If so, the reported specialization might be just a result of paucity of records. We here test for this sampling artefact in primates, a taxon in which rarity has been explained by specialization. Location Tropical Africa, Madagascar, A...
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IUCN Red List conservation status is apparently judged mainly by assessment of species' susceptibility to threat. However, risk must often depend also on the threat itself. Therefore, we investigate the value of adding to IUCN's current criteria a separate index of threat, human density. Human density in the geographic range of Threatened primate s...
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Theoretical estimates of long-term minimum viable population (MVP) sizes for mammals indicate MVPs of tens of thousands, even a million. However, data to test the theoretical estimates are effectively non-existent. I here use information on distributions of primates on islands of southeast Asia to provide empirical estimates of the size of multi-mi...
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We examined quantitatively the interaction of reserve size and surrounding local human density in the United States and their relative effect on extinction of large mammals in 13 national parks of the western United States. Data on reserve size and human density were obtained from publicly available sources. Local human density was calculated as th...
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To determine and explain biological traits that distinguish rare from common primate taxa. Africa, Americas, Asia, Madagascar. We compare the biology of rare primate taxa with the biology of common taxa. Rarity is defined by (1) small size of geographic range; (2) small geographic range plus low local population density; and (3) small geographic ra...
Article
The logic of demographic modeling, the apparent simplicity of its quantifiably, substantiated answers and the ready availability of software correlate with increasing use of demographic modeling as the means of applying biology to the conservation of potentially endangered populations. I investigated that use by considering a small population (abou...
Article
The number of primate species and genera on thirty-one south-east Asian islands west of the Wallace Line, including Sulawesi, is highly significantly related to surface area of the islands, as expected, but the z value (slope) of each relationship is low (0.21 for species). No association exists between number of taxa and distance to nearest mainla...
Article
AimAnalyses of the Rapoport effect (species at high latitudes have broader latitudinal ranges) usually indicate only a weak effect in the tropics. However, studies of tropical taxa are rare. This study used a global analysis of a tropical order, primates, to ask two questions. Is there a Rapoport effect in this tropical, terrestrial mammal, globall...
Article
Gorilla, Gorilla gorilla, females associate permanently with males. What benefit do the females obtain from the association? Where males are larger than females, as in the gorilla, protection from predation is the long-standing answer. However, protection from infanticidal nonfather males is increasingly suggested as a better hypothesis. Given that...
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Small reserves are especially likely to lose species. Is that because the reserves are small, or because small reserves are located in especially adverse landscapes? It seems that the question has rarely, if ever, been asked. Data on reserve size and location in Africa, and calculations of local (within 50 km) mean human densities from available ce...
Article
What biological traits distinguish taxa susceptible to extinction from less susceptible taxa? Substantiated island biogeographic theory suggests that after insularization, small islands lose more species than do large islands. Thus, susceptible taxa are those now found on only large islands. The traits of susceptible taxa can thus be found by compa...
Article
A global survey of a well-studied order of tropical mammals, primates, is used to explore the use of diversity hotspots in conservation. The results at this shallow taxonomic level match those for most cross-phylum analyses. Overlap of hotspots for species, genera, trait-complexes, families, and threatened species varies with the continent, and the...
Article
A global survey of a well-studied order of tropical mammals, primates, is used to explore the use of diversity hotspots in conservation. The results at this shallow taxonomic level match those for most cross-phylum analyses. Overlap of hotspots for species, genera, trait-complexes, families, and threatened species varies with the continent, and the...
Article
Caro1xCaro, T. Trends Ecol. Evol. 1999; 14: 366–369Abstract | Full Text | Full Text PDF | PubMed | Scopus (65)See all References1 summarizes the many areas of conservation management that could benefit from explicit, quantitative application of behavioral research. However, contrary to his statement ‘… use of behavioral knowledge has never been exp...
Chapter
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The chapter focuses on the fact that as compared to other mammals, including primates, humans are behaviorally, anatomically, and physiologically monandrous. However, sometimes multimale matings within the window of life-span of sperm and ovum also occur. Moreover, humans show adaptations to the possibility of sperm competition. The issue of sperm...
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Primate Sexuality. Comparative Studies of the Prosimians, Monkeys, Apes and Human Beings by Alan F. Dixson, Oxford University Press, 1998. £75.00 hbk, £32.50 pbk (656 pages) ISBN 0 19 850183 8/0 19 850182 X.
Article
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Article
The question of whether the gorilla is a threatened species is part of the larger issue of how we judge the damage that we are doing to the world. Many criteria are being used. Here I apply to the gorilla Gorilla gorilla the newly suggested IUCN criteria for categorising the conservation status of all species, both to reassess the gorilla's conserv...
Article
We investigate the social significance of the within group ('close') calls of gorillas by examining correlates of calling with dominance rank and with relatedness of adults, and by examining whether the outcomes of interactions between adults differ depending on the calls given during the interactions. In two wild gorilla groups, the majority of ad...
Article
Guidelines for submitting commentsPolicy: Comments that contribute to the discussion of the article will be posted within approximately three business days. We do not accept anonymous comments. Please include your email address; the address will not be displayed in the posted comment. Cell Press Editors will screen the comments to ensure that they...
Article
Correlations between mating system and various aspects of genital anatomy suggest a strong influence of sexual selection on genital morphology. We test the generality of the influence by examining whether primate taxa in which there might be enhanced sexual selection (those with multi-male mating systems) possess, as expected, relatively more spino...
Article
Mountain gorillas (Gorilla gorilla beringei) give double-grunts to one another in a variety of situations, when feeding, resting, moving, or engaged in other kinds of social behavior. Some double-grunts elicit double-grunts in reply whereas others do not. Double-grunts are individually distinctive, and high-ranking animals give double-grunts at hig...
Article
Animal signals have been interpreted as indicating something about the signaller's internal state and hence its subsequent behaviour, while at the same time eliciting a response from the receiver. Such signals are often given when the costs and benefits of an action depend on what others do. This interpretation of meaning and function of signals ha...
Article
Guidelines for submitting commentsPolicy: Comments that contribute to the discussion of the article will be posted within approximately three business days. We do not accept anonymous comments. Please include your email address; the address will not be displayed in the posted comment. Cell Press Editors will screen the comments to ensure that they...
Article
Individuals in social groups of a number of species produce and exchange among themselves frequent, quiet vocalisations, here termed "close' calls. The authors describe the call repertoire, the age-sex distribution of frequencies of call-types and the contexts in which the calls are given, and compare these measures with descriptions for the other...
Article
“The Parties to This Treaty…are resolved to unite their efforts for collective defense,” and to a fairly large extent, the nations of the North Atlantic Treaty Organization (NATO) have done just that for nearly 50 years. “During fights, individuals compare the strength of their own group with that of the opponent. When they perceive that group memb...
Article
Nonfertilizing sperm with special morphologies have long been known to exist in invertebrates. Until recently, abnormal sperm in mammals were considered errors in production. Now, however, Baker and Bellis (1988, 1989) have proposed that mammalian sperm, like some invertebrate sperm, are polymorphic and adapted to a variety of nonfertilizing roles...
Article
Nonfertilizing sperm with special morphologies have long been known to exist in invertebrates. Until recently, abnormal sperm in mammals were considered errors in production. Now, however, Baker and Bellis (1988, 1989) have proposed that mammalian sperm, like some invertebrate sperm, are polymorphic and adapted to a variety of nonfertilizing roles...
Article
Gorilla gorilla ally to protect relatives from harm, to provide them with access to otherwise unobtainable resources and, perhaps, to emphasise their dominance over rivals; individuals might also ally to obtain resources for themselves, and to establish supportive relationships with other group members. The major contrast with female-resident prima...
Article
In most wild and captive monkey groups, some females are clearly dominant over others. Dominant animals have priority of access to resources, and well fed animals generally outreproduce poorly fed ones. So why is it that only in some social groups are dominant female monkeys more fecund than subordinate ones? The distribution of food influences the...
Article
There had been no news of Nigeria's gorillas for 30 years when in 1987 rumours began to circulate that they survived in the south-east part of the country. At the end of the year the authors conducted a survey in the area and confirmed that gorillas were indeed present. They found evidence of five sub-populations, more or less isolated from each ot...
Chapter
We see three main ways in which knowledge about the determinants of fertility in nonhuman primates is useful to an understanding of human fertility. First, we believe that it makes a difference to the perspective with which the human data are viewed if it is known that similar effects are, or are not, found in other primate species. Secondly, if pr...
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The existence of an influence of support in contests on dominance rank has been known for nearly 30 years, yet experimental analysis of the phenomenon is extremely rare. Similarities in the findings of two experiments conducted 18 years apart are therefore highlighted in the hope that their emphasis might stimulate further experimentation on the fa...
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In a number of primate species, daughters have a dominance rank adjacent to their mother's, and younger sisters dominate older ones. The acquisition of a dominance rank largely independent of body size has been related to the reception of help in contests. This paper concentrates on a three-stage process. (1) Vulnerable individuals are helped in co...
Chapter
Different species, habitats, and countries have different requirements and priorities for conservation. The conservation program for the gorilla population in Rwanda has been described as a model project, hence its inclusion in this section of the symposium. It is certainly an unusual project in several respects, including the structure of its fund...
Article
Suspicions that previous results for time spent feeding by individual gorillas were too low are confirmed with more refined methods and a greater quantity of data. We found that adults (> 8 years) spent about 45% of the day feeding, compared to the former value of about 30%. Immatures increased their time feeding on solid food up to about 5 years b...
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Mountain gorillas exist in the wild today only in the Virunga volcanoes, which span the borders of Zaire, Rwanda and Uganda, and in the Bwindi Forest Reserve of Uganda, and number probably fewer than 400. The authors describe the 1981 survey of the entire Virunga gorilla population, the first to be done since 1973. The results clearly show how the...
Article
Data on population size, density and composition, biomass, group size and composition and reproductive rates are compared between populations in the two regions of gorilla distribution, equatorial west and east central Africa. The Virunga Volcano population of the latter region is shown to be a good model for all populations. Information on age at...
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Full-text available
It has long been known that primate species differ greatly in the weight of their testes relative to body weight1. Recently it has been suggested that among the three species of Pongidae (the great apes), the disparity in testes weights is associated with their different breeding systems2-4. Male gorillas and orangutans copulate infrequently, and w...
Article
The most detailed survey yet made of the numbers, distribution and conservation status of gorilla in the Bwindi Forest Reserve indicates a total population of 95–135 animals and a breeding population of only about 75. Within the Reserve the local people use an area more than twice as large as that used by the gorillas, and it is clear that gorillas...
Article
Young gorilla males can be divided into those that leave their natal group to find mates else-where and those that remain to inherit leadership and mating rights within it. This study of the relationships between four adolescent males and their group leaders in two gorilla groups indicates that a close relationship with the leading male in infancy...
Article
Information was collected over a period of almost 12 years on the gorillas of the Virunga Volcanoes region of Rwanda and Zaire, most of it collected since September 1972. Comparisons were made with the Gombe Stream chimpanzee population (values in parentheses). Gorilla females matured at about 8 years (compared with 9-10 years for the chimpanzee) a...
Article
Over the last twenty years, the population of Mountain Gorilla (Gorilla gorilla beringei) in the Virunga Volcanoes region of Rwanda, Uganda, and Zaire, has halved from an estimated 400-500 to fewer than 250. The major cause of this decline is loss of habitat through large-scale appropriation of National Park land in Rwanda for agriculture, and thro...
Article
Social relationships between adult males and females in two groups of wild mountain gorilla are described. Each group contained about five, largely unrelated sub-adult and adult females, a peripheral near-adult male, and one fully mature male. Females were clearly attracted to the dominant male, and those with young offspring spent the most time ne...
Article
This paper examines proximate and ontogenetic causes of differences between the relationships of wild gorilla males. Two pairs belonging to different reproductive groups were observed. In both, the mature male was dominant over the younger one. However, in one, the males interacted extremely rarely, while in the other, affinitive behaviour, largely...
Article
Because gorilla females transfer between breeding units, those in the study groups were probably distantly related and not familiar in immaturity. Apparently as a consequence, affinitive behaviour between most females was rare. However, one mother-daughter pair and one pair of females familiar from immaturity had obviously friendly relationships in...
Article
In many primate species, more males than females leave their natal group and transfer to another. In man, chimpanzee and the gorilla, however, the reverse is the case. This paper presents detailed data for the gorilla on individuals' movements into and out of breeding units. Comparisons are made with other primates, and with data on two non-primate...

Citations

... Twenty years later, Coolidge (1929), a Harvard zoologist and a founder of both the International Union for Conservation of Nature (IUCN) and the World Wildlife Fund (WWF), lumped all gorillas together as a single species: Gorilla gorilla (Sarmiento and Oates 2000). Before Coolidge, the world had eleven species of gorilla (with many European names, e.g., Gorilla jacobi, Gorilla schwarzi, Gorilla hansmeyeri, Gorilla zenkeri, and Gorilla graueri) (Groves 2002). Though Coolidge made some mistakes, e.g. ...
... Interestingly, in middle age, the same prevalent vowels "a" and "ɛ/e" in newborns' cry were reported by the Florentine poet Antonio Pucci (1310/1388), though we might not agree with his interpretation: "infant males cry emission include the "a" in memory of Father Adam, while infant females include "ɛ/e" in memory of Mother Eve, thus carrying on those cry all world's troubles" (Giallongo 1997). Nervous motor controls for cry emission are the same as the ones reported in monkey models (Jurgens 1990(Jurgens , 1992Jurgens and Ploog 1988;Lester and Boukydis 1992), and the infant cry must be considered thoroughly an "animal" signal. ...
... Indeed, some have suggested that sperm dimorphism allows specialization in the nonfertilizing sperm for a competitor-inhibiting function, sometimes called "kamikaze sperm" (Baker & Bellis, 1989). Although this hypothesis has fallen out of favour, it was proposed and mainly evaluated in the context of mammalian sperm (Harcourt, 1991(Harcourt, , 1989Moore, Martin, & Birkhead, 1999), where nonfertilizing sperm are not usually differentiated from fertilizing sperm in a sophisticated way. ...
... Males often engage in temporary coalitions, in which 2 or more males cooperate to compete against others in contests over resources or rank (Smith 2014), thereby increasing individual access to females. Recurring coalitions among the same males, also known as male alliances (Harcourt 1992), are an unusual phenomenon (Díaz-Muñoz et al. 2014). Alliances occur in, though are not limited to, humans (Chagnon 1988), nonhuman primates (e.g., chimpanzees, Mitani et al. 2002a;savannah baboons, Noë 1992), lions (Panthera leo, Packer et al. 1991), cheetahs (Acinonyx jubatus, Caro 1994), lekking birds (e.g., manakins Chiroxiphia linearis, McDonald and Potts 1994), fish (reviewed in Taborsky 1994), and bottlenose dolphins (Tursiops aduncus, Connor et al. 1992). ...
... But when did it begin? Did it begin with the first expansion of modern humans out of Africa, 200-45 thousand years ago (kya) (Henn, Cavalli-Sforza & Feldman, 2012;L opez, van Dorp & Hellenthal, 2015;Harcourt, 2016;Bae, Douka & Petraglia, 2017;Hershkovitz et al., 2018), or 12-10 kya during the Neolithic Revolution when human populations began to increase rapidly as a result of the development of agriculture (Bocquet-Appel, 2011;Lenton, 2019), or did it begin much more recently, even as late as during the 19th century industrial revolution? Avise et al., (2008) characterised these as the three phases of the Sixth Mass Extinction, implicitly including all human-caused extinctions, and considering the status of biodiversity now to have reached a crisis point. ...
... Data on aging orangutans and gorillas are even fewer. There are reported cases of orangutan females giving birth at an advanced age (Wich et al., 2004), while the opposite is true for mountain gorillas (Stewart et al., 1986). Given the paucity and variability of available information, there was a need for more data on reproductive senescence in aging female apes; thus we report results of hormonal and associated sexual cycling patterns from a nationwide study on aging female western gorillas (Gorilla gorilla gorilla) housed in zoos across North America. ...
... The Virunga gorillas, however, live in groups consisting of one (~60%) or several adult male silverbacks (~40%) that coexist for many years and are often related (Robbins, 1995(Robbins, , 2001. The formation of groups seems to be in part due to two factors; (a) females selecting males who can provide protection against infanticide, and (b) a strategy of long-term mate guarding by males (Harcourt, 1981;Watts, 1996). The social system is age graded, "nonfemale-bonded" (Harcourt, 1979a;Wrangham, 1980), with the strongest long-term relationships being formed between adult males and females; relationships between females are weak (Harcourt, 1979b;1979c). ...
... More broadly, birding ecotourism (involving several wildlife festivals) in the lower rio Grande Valley of Texas contributed US$59 million in annual direct expenditures to the local economy, compared to US$105.9 million from farm earnings (Mathis & Matisoff, 2004). Similar studies have shown that ecotourism generates more economic benefits to landowners than harvesting for a variety of wildlife species including macaws (Munn, 1992), gorillas (Harcourt, 1986), lions (Thresher, 1981a(Thresher, , 1981b, and elephants (Western & Henry, 1979). ...
... In addition, the velocity of climate change over longer periods of time played an important role in the human colonization of the globe, opening pathways and territories for settlement where climatic conditions were suitable for humans (e.g. warming of northern regions) [38]. ...
... Callimico goeldii: Heltne, Wojcik, & Pook, 1981;Callithrix jacchus: Kendrick & Dixson, 1984;Leontopithecus rosalia: Kleiman, Hoage, & Green, 1988;Brachyteles arachnoides: Milton, 1985), Old World monkeys (e.g. Macaca spp: Hinde & Rowell, 1962;Zumpe & Michael, 1968;Dixson, 1977;Wolfe, 1984;Slob & Nieuwenhuijsen, 1980;Slob et al., 1986;Chevalier-Skolnikoff, 1975;in Lophocebus albigena: Wallis, 1983;Papio ursinus: Saayman, 1970;Miopithecus talapoin: Dixson, Scruton, & Herbert, 1975) and apes (Pan paniscus: Tutin & McGinnis, 1981;Pan troglodytes: Goodall, 1986; Gorilla beringei beringei: Harcourt, 1981), EEC between partners possibly also occurred during dorsoventral sexual interactions. As reported for other primate species, gelada females may seek the males' eye contact to assess males' intent and communicate their engagement. ...