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PROBLEMS AND POTENTIALS FOR PRIMATE BIOLOGY AND CONSERVATION IN THE NEW WORLD Paul G. Heltne and Richard W. Thorington, Jr. The major objectives of the conference were to clarify the methodology and evaluate the data necessary for sound conservation and management of wild primate populations. Nearly all the relevant studies of New World monkeys were scrutinized at some point during the proceedings. By detailing the available knowledge of neotropical primates, participants also delineated major gaps in essential information. Thus the papers of the conference address the following important con- cerns of population biology of New World primates: distributions and absolute and relative abundances; relationship of group density, group size, and group structure of primate species to the total faunal com- munity and the type and quality of forest; and human customs and governmental regulations relevant to per- sistent threats against primate populations, to primate exports, and to primate conservation. It is quite obvi- ous that both the problems and suggested solutions are broadly applicable to primate conservation on other continents as well. In what follows, we attempt to draw into a cohesive picture the highlights of the formal and informal exchanges and present our syn- thesis of the information presented at the conference. We will focus the summary around three themes: 1. Crises: The endangered status of the Central American squirrel monkey (Saimiri sciureus oerstedii) and the cotton-top tamarin (Saguinus oedipus). 2. The limitations of the current data basic to the establishment of sound conservation and management programs: macro-, meso-, and microdistributions; den- sity estimates; and basic parameters of life history and quality of local habitats. 3. The export trade and other, more severe, pres- sures on primate populations. CRISES The rapid establishment of protected reserves is essen- tial if two species of primates, the cotton-top tamarin and the Central American squirrel monkey, are not to become extinct. The nearly complete destruction of the forests in the ranges of these two species accen- tuates the "no forests-no primates" principle, which appeared again and again in the conference. This is a dictum that holds rigorously true for all New World primates. Hernandez-Camacho and Cooper map a large spe- cies range for 5. oedipus (see also Hershkovitz, 1949, 1966). This range is documented by museum specimens taken over the last century. However, Hernandez-Camacho and Cooper are convinced that this picture is obsolete. Their recent examination of the region shows that primary and second growth forests suitable for cotton-tops have been extirpated from large portions of the historical range. To create grazing land for cattle, forest destruction has pro- ceeded rapidly within the last two decades. During this same period, 30,000-40,000 cotton-tops were ex- ported. The cotton-top has been protected by law in Colombia since 1969, but appropriate habitat reserves are essential to allow the continued natural existence 110
PROBLEMS AND POTENTIALS FOR PRIMATE CONSERVATION IN THE NEW WORLD 111 of the tamarin. Patricia Warner is studying one popula- tion (deme) of 5. oedipus in a small remnant forest in northern Colombia. Hopefully, her study will form the basis for the required conservation effort. Baldwin and Baldwin indicate a similarly extreme habitat depletion forSaimiri sciureus oerstedii, Histor- ically, the Central American squirrel monkey was common (Handley, 1966) throughout the forests and woodlands of Chiriqui Province of western Panama. The Baldwins' surveys reveal that most of the Chiriqui forests have already been totally eliminated for pas- tureland. The continuation of this process is assured by the current Panamanian agrarian reform laws. Re- turning after a year to recensus a deme of squirrel monkeys, the Baldwins found that their own fairly sizable study plot had been bulldozed. This left stands of trees only in inland and mangrove swamps in that immediate region. It is clear that the governments of Panama and Colombia must act rapidly to designate protected reserves adequate to stave off the extinction of these two species. The situation appears to be equally critical for several species such as Leontopithecus rosalia (see Bridgewater, 1972) and Saguinus leucopus (Hernandez-Camacho and Cooper, 1976), and only slightly less critical for others. In some species re- gional populations may be endangered. According to Hernandez-Camacho and Cooper this is true for popu- lations of Aotus trivirgatus, Saimiri sciureus, Cal- licebus molloch, Cacajao melanocephalus, Alouatta seniculus, Cebus albifrons, and Lagothrix lagotricha. The Baldwins found Cebus capucinus populations more endangered than Saimiri sciureus oerstedii in the areas of Chiriqui that they sampled. There was no evidence at all of Ateles geoffroyi in the locales the Baldwins visited, though Handley (1966) indicates that it occurred in Chiriqui forests. Freese notes that Ateles geoffroyi is extremely rare beyond the boundaries of Santa Rosa Park in the remaining tropical dry forests of Costa Rica. Hunting of Ateles and Lagothrix for meat and the clearing of the highest and most heterogeneous forests for farm sites were probably straining the reproductive potential of the spider mon- key and woolly monkey at La Macarena according to Klein and Klein. In Trinidad the cebus and howler monkeys have been eradicated from all but the most rugged parts of the island and a few small wildlife sanctuaries, themselves unprotected or under mining lease. The case of Aotus is particularly significant, because the night monkey is currently one of the New World primates most in demand for biomedical research. Scientists studying malaria have noted that Aotus from northern Colombia are most susceptible to experimen- tal infection with Plasmodium falciparum. It is not known whether this susceptibility results from genetic or environmental factors, or both. Because of this susceptibility, Aotus are the animals of choice for this research, and approximately 4,000 night monkeys are used in malaria studies each year in the United States. A large portion of these animals come from a relatively small area in the vicinity of Magangue, Colombia, as documented by Green. Conservation of this important population of Aotus is a complex problem. Capture of the animals probably occurs as forests are being cleared for other purposes. Thus, destruction of the forests is again a most important aspect of the pressure on night monkeys. However, in order to assess the effect of habitat change on an Aotus population, we need much more information on Aotus biology, particularly on the density of animals normally found in different forest types. Unfortunately, most of the field data on the biology of Aotus is fragmentary and essentially anec- dotal. Hernandez-Camacho and Cooper, summarizing what little is known of the habitat requirements of Aotus, point out the very hopeful fact that with the exception of mangrove swamps, Aotus typically in- habit every major forest zone of Colombia, including second growth and even well-shaded coffee planta- tions. If complete clearing were avoided, the biomedi- cal supply could be assured with appropriate manage- ment applied to small forests on steep or rocky ground, fence rows, streamside tracts of trees, and domestic plantations. Thorington, Muckenhirn, and Montgomery pre- sented a pilot study of home range and activity pat- terns of the night monkey. Theirs was a pioneering use of radio-tracking on primates. With this technical advance, they were able to determine that their "study" animal moved short distances during feeding sessions in the vicinity of the home tree. Longer exploratory excursions took it up to 250 m from the home tree, roughly retracing its original pathway on its return journey. Daylight hours were spent at 10-15 m above ground. In the night its travels brought it quite close (3 m) to the forest floor, but most of its activity occurred in the canopy. On large or small branches, it moved quietly and carefully, making few long jumps and using its tail extensively for balance. The animal showed postdusk and predawn activity periods with 1 or 2 hours of low activity in between. Seventy-two percent of its time was spent in an 800 m2 area and 85 percent in an area of 0.5 ha. Other night monkeys may have been present in this area as well. It is not difficult to perceive serious threats to many other populations and species. The assaults on popula- tions of Lagothrix are discussed below. For several
112 HELTNE and THORINGTON genera only a dearth of information is available. For example, the notes of Hernandez-Camacho and Cooper and the paper by Moynihan constitute almost the total available information on the ecology and natural behavior of the pygmy marmoset (Cebuella pygmaea). These authors document the unusual sap-licking habit of the pygmy marmoset. This component of the Cebuella diet is in addition to fruit, buds, and insects. The species will come to the ground for insects, its sap holes are low on the trees, and it prefers to make crossings from tree to tree at a low level rather than be exposed to the dangers of predation in the canopy. Much less is known about the habitats of Chiro- potes, Pithecia, orCacajao. Indeed, Cebuella, Chiro- potes, or Callimico may provide the crucial experi- mental interface for cancer or schistosomiasis, just as Aotus is so unexpectedly doing for malaria research. In most cases we lack the detailed information re- quired for intelligent evaluation of the condition of a primate species. We must know where the species lives, both in general and very specific terms, and we must be able to assess the status of populations and the quality of habitats. DATA BASIC TO PRIMATE CONSERVATION Distributions Distributional data are of primary importance in pri- mate conservation. Three sorts of distributions were presented at the symposium: (a) macrodistributions (the presence or absence of a species in a large region of a country or between two major tributaries of the Amazon), (b) mesodistributions (presence or absence of a species in a locale), and (c) microdistributions (distribution of animals within forest types of a particu- lar locale including the study of habitat preferences and resource utilization of the primates). Several pap- ers added abundance, density, biomass, and ethologi- cal details to accounts of microdistributions. Ulti- mately much more distributional data at all three levels will be needed for informed decisions on resource management. Macrodistribution Taxonomic and zoogeographic studies of the ceboids are essential to a clear understanding of the prob- lems of primate conservation in the New World. Hernandez-Camacho and Cooper draw together for the first time a zoogeography of the primates of Colombia. A summary appears in Table I. Previously, macrodistributions for Colombian primates were widely scattered through many, often obscure, sources or, at best, were arranged by genus and again difficult to collate. As they point out, many of the bibliographic sources are old, and Hernandez-Camacho and Cooper updated this information with many observations made recently in the field. An inadequately known distribution can make conservation problems seem much less grim than they are and cause us to misdirect our limited remedial efforts. The most critical prob- lems are found among species with limited distribu- tions, usually in northern and central Colombia. In these areas, forest tracts once rich in primates remain only as scattered plots or hedgerows, as has been discussed above. On the other hand Hernandez- Camacho and Cooper indicate an enormous range extension for Callimico goeldii, This primate, appar- ently never existing in high densities anywhere in its range, was previously documented only from small pockets in Peru and Brazil. For several important genera, large regions remain unknown, e.g., the whole area between the Yari River and Apaporis River for Saguinus (two species meet in this area), Pithecia and Cacajao (which apparently replace each other in this region), and Cebus albifrons. In the range of C. albifrons, large areas are indicated as uncertain; this is also true in the distributions of Saimiri, Aotus, Lagothrix, andAteles. Given the pres- ent importance of primates, question marks on dis- tribution maps cry for the necessary field studies to fill out the range or indicate that indeed a species defi- nitely does not exist (or no longer exists) in a region. It may be noted here that vast regions of Brazil, Paraguay, Bolivia, Ecuador, the Guianas, Nicaragua, El Salvador, the Honduras, Guatemala and the Yuca- tan are unknown so far as the present distribution of primates is concerned. For purposes of conservation and biomedical research supply, it is increasingly important that these gaps be filled. Important problems of competition, ecological re- placement, and speciation are raised by the distribu- tion maps of Hernandez-Camacho and Cooper. For example, they indicate a rather narrow zone of contact between Aotus trivirgatus lemurinus and A. /. trivir- gatus. The recent indications (Brumback et al., 1971) of chromosome polymorphism within A. t. griseimembra and cytogenetic differences between A. t. griseimembra and A. t. trivirgatus make the geo- graphically intermediate and ecologically different A. t. lemurinus very interesting biologically. Hernandez-Camacho and Cooper also show that the macrodistributions of numerous primate species are coextensive. This may be illustrated by the following example, though similar situations occur elsewhere. In the Amazonas and Putumayo comesarias of Colombia, between the Caqueta River and the Putumayo River, 13 species are found sympatrically: Cebuella pyg-
PROBLEMS AND POTENTIALS FOR PRIMATE CONSERVATION IN THE NEW WORLD 113 maea, Saguinus nigricollis or Saguinus graellsi, Saguinus fuscicollis, Callimico goeldii, Saimiri sci- ureus, Aotus t. trivirgatus, Callicebus torquatus medemi, Pithecia monachus, Alouatta seniculus, Cebus albifrons unicolor, Cebus apella, Lagothrix l. lagotricha, and Ateles belzebuth, How these species divide space and resources among themselves and the arboreal marsupials, rodents, carnivores, birds, and reptiles is one of the truly exciting questions of con- temporary primatology. Mesodistributions Utilizing a limited number of records, zoogeographers infer presence of a species in the intervening or surrounding territory in the absence of major ecologi- cal barriers or changes, e.g., high mountain ranges, large rivers, or the change from forest to open grass- land. Field research cannot sample such large areas uniformly, nor are these regions in any sense ecologi- cally uniform. The next step toward sound conserva- tion is to determine the presence or absence of a species in a given district or locale, such as the area of a proposed national park or within the drainage basin of a small river system. Freese offers such a mesodistribution for the pri- mates of Santa Rosa National Park, an area of north- western Costa Rica. Previously, few records docu- mented the existence of Ateles geoffroyi and Cebus capucinus in this region. Klein and Klein give similar data for La Macarena National Park and several other sites in the area south of Villavincencio in Colombia. They find more species exist on the south bank of the Guayabero River than on the north bank. Callicebus moloch is the only "titi" on the northern bank. South of the Guayabero C. moloch has a very limited habitat, and C. torquatus is dominant. Also present on the south bank, but not found north of the river, were Cacajao melanocephalus, Cebus albifrons, and Lagothrix lagotricha. Neville indicates the probable distribution of howlers in the national park system in Venezuela. Mesodistributions of heavily disturbed regions are given by Neville for Trinidad and by the Baldwins for the Chiriqui Province of western Panama. In Trinidad cebus and howlers are restricted to very few areas and may be inadequately protected or actively hunted even there. In Chiriqui the rugged Burica Peninsula nevertheless shows fairly extensive cutting, though many moderately large forest tracts remain containing one or more of the species presentâcebus, howlers, and squirrel monkeys. In the remainder of the prov- ince, forests exist only as small pockets in swampy lowlands or in larger marshland tracts along the seacoast. Ateles and Aotus were found in none of the sites visited in western Chiriqui. Microdistributions (Habitat evaluation) Information gathering at the microdistributional level is arduous, time-consuming, and confronted with prob- lems of standardization. Uniformity has not been attained in defining forest types or levels of degrada- tion. Strict comparability may not be possible over any great area. Freese shows that Alouatta are largely restricted to limited stands of evergreen trees in the tropical dry forest of Santa Rosa National Park, in Guanacaste Province, Costa Rica. Ateles and Cebus have a broader distribution within the park. Ateles ranges freely in the semideciduous areas, as well as in ever- green patches, throughout the year. Cebus are found in evergreen, semideciduous, deciduous, and mangrove stands during all seasons and are not reluctant to make crossings on the ground. Klein and Klein differentiated eight tree communities within the tropical wet forest in La Macarena Park, in Colombia. These communities varied in usefulness, sometimes seasonally, to the monkeys in the Kleins' study area. Forested islands in heavily farmed Chiriqui often do not contain any primates according to Baldwin and Baldwin. Saimiri were more numerous than Cebus or Alouatta in the most disrupted inland swampy areas. Cebus are able to utilize mangrove stands, though Alouatta and Saimiri spend very little time in mangrove areas and are apparently unable to survive in mangrove and marshy scrub communities. Since such plots will soon be the only available primate habitats in many areas, this report takes on tremendous importance. Obviously, it is impossible to evaluate every area of forest in Central and South America. Thus, methods of extrapolation and estimation become important. Pri- mate distribution and abundance per habitat type must be complemented with detailed information about dis- tribution and abundance of habitat types. Habitat diversity and condition may be assessed at a qualitative level locally. Over broader areas, newer quantitative methods are becoming available. Locally one need not actually see hunters or woodcutters in the forest to determine their presence. Tree species of economic importance or game species such as peccaries, tapirs, and guans will indicate that incursions by man are not yet severe. Trees such as Cecropia are typical of the early stages of forest regeneration and are thus a good indication of disturbed habitats. As suggested by the Kleins, key tree species such as Brosimum and Ficus, which are important in the diets of many primates, may provide evidence of a favorable habitat.
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116 HELTNE and THORINGTON On a broader scale, agricultural and forestry reports from primate-producing nations are often valuable, but seldom contain the detail necessary for exacting esti- mation. Technology is now available for quantitative habitat evaluations over large areas. The basic forest data is supplied by ERTS satellite photos that provide extremely detailed knowledge of the distribution of forest and some differentiation of forest quality. The satellite photos also have the tremendous advantages of frequent update and the possibility of automated analysis. However, no scientific group is organized or funded to extrapolate primate abundance from forest distribution, even if more of the necessary baseline correlations were available. Density and Biomass The density and biomass data presented at this confer- ence (summarized in Table 2) can be duplicated for other species of New World primates in only a very few instances: Callicebus molloch ornatus (Mason, 1968) and Saimiri sciureus (Thorington, 1968) in small forest plots on Hacienda Barbiscal in the llanos of Colombia; Isla Santa Sofia in the Amazon River near Leticia, Colombia, for Saimiri sciureus (Bailey et al., 1974); and Warner's study of Saguinus oedipus in northern Colombia. Only for Barro Colorado Island (BCI) is there anything approaching time-trend data over a prolonged period. Biomass estimates, calculated from information in the various papers in this symposium, are amazingly similar within genera. Despite smaller group size, Alouatta seniculus troops show the same general biomass relationships as do BCI and Costa Rican howlers. This makes the intense population at Hacienda Barqueta even more phenomenal and sup- ports the Baldwins' interpretation of their study site as a refuge for troops originally dispersed over a much TABLE 2 Population Density and Biomass.a Species. Locale, and Source Troop Size Density of Range of Troops Troops No. Individuals per Unit Area Biomass6 (kg/ha) Remarks Alouatta palliata BCI 1932 4-35 23/3,840 acres 44-76 har 398/3,840 acres 1.4 (Carpenter, 1964) (1.5/km2) (26/km2) BCI 1933 4-29 28/3,840 acres 490/3,840 acres 1.7 (Carpenter, 1964) (1.8/km2) (32/km2) BCI 1951 2-17 30/3.840 acres 12.3-16.2 har 240/3,840 acres 0.8 (Collias and Southwick, (1.9/km2) (15/km2) 1951) BCI 1959 3-45 44/3,840 acres 814/3,840 acres 2.9 (Carpenter, 1964) (2.8/km2) (52/km2) BCI 1967 11-18 63-87/3. 840 acres 7.9-11.6 har 0.60-0.80/ha 3.3-4.4 (Chivers, 1969) (4.0-5.6/km2) (60-80/km2) Santa Rosa 3-24 8-10/4 km2 70- 100/4 km2 1.0-1.4 Howlers are found chiefly (Freese) (2.0-2.5/km2) (18-25/km2) in evergreen forest at Santa Rosa Hacienda Barqueta 7-28 11/20 ha 3.2-6.9 ha at least 157/20 ha 45 Density 12-29 times as (Baldwin and Baldwin) (55/km2) (785-1.050/km2) high as BCI with normal fertility and no indication Burica Peninsula 10-30 several seen or of food shortage (Baldwin and Baldwin) heard at once Inland lowland forests small scattered of Chiriqui, Panama (Baldwin and Baldwin) Alouatta seniculus La Macarena. Colombia (Klein and Klein) Hato Masagural Venezuela (Neville, 1972 census) Ateles belzebuth La Macarena 3-6 4-15 6-15/780 ha (0.8-2.0/km2) 19/190.6 ha (10.0/km2) 17-22 independently locomoting animals 3/780 ha (0.4/km2) 0.66-7.08 ha (aver. 3.21 ha. 1969 census) 259-388 ha 30-75/260 ha (12-29/km2) 16.3/190.6 ha (86/km*) 30-40/260 ha (12-15/km2) 0.6-1.6 4.7 0.6-0.8
PROBLEMS AND POTENTIALS FOR PRIMATE CONSERVATION IN THE NEW WORLD 117 TABLE 2 (Continued) Species, Locale, and Source Troop Size Density of Troops Range of Troops No. Individuals per Unit Area Biomass" (kg/ha) Remarks Ateles geoffroyi Santa Rosa I -20 110- 160/17 km2 0.3-0.5 Cebus capucinus (6-9/km2) Santa Rosa 15-20 15-20/49 km2 0.5 km2 250-350/49 km2 0.1-0.2 (0.3-0.4/km2) (50 ha) (5-7/km2) Hacienda Barqueta 27-30 1/32-40 ha 32-40 ha 0.7-0.9/ha 1.8 Forage and travel 50%- (2.5-3. I/km2) (70-90/km2) 70% of time Mm ica Peninsula 20 or more Males threaten observers Inland lowland 2-5 Animals flee sileni tly forest of Chiriqui BCI (Oppenheimer. 1968) C. apella La Macarena 15 or less 0.9 km2 (90 ha) Males threaten observers 6-12 independently locomoting animals Saimiri sciureus oerstedii Hacienda Barqueta 23-27 4-6/780 ha (0.5-0.8/km2) 2 at 20 ha site 17.5-40 ha (5/km2) 15-25/260 ha (6-10/km2) 0.2 14.7/10 ha, 50/20 ha 0.7 (147-250/km2) Forage and travel 95% of time. Biomass: 1.37- 2.32 using 147-250 animals/km2 Burica Peninsula Inland lowland forest of Chiriqui S. sciureus La Macarena 15-30 10-20 I/forest pocket 0.8-2 ha 10-13/ha 9.3-12.1 Forest sizes range from (1,000-1,300/km2) 0.8-2.0 ha 25-35 3-6/780 ha independently (0.4-0.8/km2) locomoting animals 50-80/260 ha (19-31/km2) 0.2-0.3 â¢ Nature of sample in each case can be obtained from Table 4. 8 Biomass calculations, except for Baldwin and Baldwin, are based on the following figures from Eisenberg and Thorington (1973): Alouatta, 5.5 kg; Ateles, 5.0 kg; Cebus, 2.6 kg; Saimiri. 0.93 kg. r From Neville. 1972. greater area. Ateles and Cebus from Colombia and Costa Rica show quite similar density, but Cebus from Hacienda Barqueta have a 10-times-higher density. Saimiri at Hacienda Barqueta and La Macarena are certainly of the same magnitude of biomass, but Saimiri stranded in relict inland forest plots have a density 10-20 times as great. Indeed, squirrel monkey biomass in these small forest pockets exceed the biomass of all other species and locales except for the Hacienda Barqueta howlers. When density estimates can be combined with habitat distinctions, the area over which a forest type remains constant (i.e., similar in species composition, in hunting or logging pressure, or the presence of other arboreal animals) can be used to estimate the total population of a species in a region. Without such a dual data foundation, management has a very unstable basis for decisions regarding permissible levels of harvesting. The comparative figures, produced here for the first time, are tremendously valuable. The consistency within genera suggests the possibility of fairly effective extrapolation. Neville correctly em- phasizes the necessity of a large sample size for estimating primate population parameters for a par- ticular habitat type. Even with extensive data on one site, as Neville points out, extrapolation has decreased certainty the farther it goes from the site of census. There probably exists some optimal distance for each species at which a spot survey should be made to check whether extrapolated density estimates are ac- ceptably accurate. Once baseline densities for habitats of various types and degrees of disturbance are obtained, technically advanced methods such as the ERTS satellite photos may speed estimates for broader areas. With these photos experimental attempts at correlations of forest type with primate density are now under way in Co- lombia under the joint auspices of INDERENA, PAHO,
118 HELTNE and THORINGTON and ILAR. The primate density estimates produced by this technically advanced system must also be locally verified with spot surveys or "ground truth stations." To summarize, our ability to estimate whether there are 10 monkeys per hectare or one monkey per 10 hectares for any species or area in the New World tropics remains limited and often uncertain, though the comparative data published in this symposium are certainly a major advance. This lack of sound scientific information explains why no nation has yet established a husbandry-management program for primates akin to that for game animals and birds. It is indeed possible that some areas would sustain a thinning of the primate population and even benefit by limited harvest with appropriate techniques (though we are unaware of such locales). Other areas most assuredly cannot. Life Tables As Heltne, Turner, and Scott indicate, careful exami- nation of the age structure of a troop or population is necessary to estimate reproductive success and overall status. Density estimates alone are not a sufficient base for an effective program of conservation. Life tables of wild primates need to be constructed to insure that a healthy population structure can be recognized and maintained. This requires considerable basic knowledge concerning the biology of a particular species, i.e., length of the preadult period, number of years a female can be expected to live after attaining reproductive maturity, and how many infants per year she will produce under normal circumstances. At the moment, data for constructing a life table are being collected for the howler monkeys of BCI by Thorington and co-workers. In order to do so, they must capture, handle, and mark animals. Techniques for doing this have become well developed and almost completely safe. Attempts to gather such data have not even been initiated for other species in other areas. Age criteria for field evaluation of population struc- ture are extremely important. It was felt by most at the conference that more effort should be made to refine our techniques for estimating the age of wild primates. It would be very valuable to compile a photographic handbook of animals of known age so that fieldwork- ers could refer to a visual gauge of the changes in physiognomy of animals as they mature. More data are desirable on the eruption and wear of teeth, on the rates of skeletal maturation, and on the weights of animals of known age. Much of this information can be obtained in the field only when the investigator cap- tures and handles his animals. Valuable collaboration in building these references and obtaining the life table values listed above could come from zoo and institu- tional breeding programs. While short-term field studies cannot produce data adequate to establish life tables, such research can produce age-sex class censuses. Repeated censuses can give some indication of the population structure found in normal or stressed situations. Even this approach is technically difficult. Neville correctly em- phasized the problems of obtaining accurate data on such basic parameters as total numbers, ages, and sexes of animals in a troop and the necessity of a large sample size for estimating these parameters for a particular habitat type. Certain problems of censusing appear to be greatly diminished if two or three indi- viduals are engaged in the counting process at once (Thorington, Heltne, and Schon, personal observa- tion). In the absence of clear-cut demographic data, field censuses have not had a theoretical baseline for com- parison. Heltne, Turner, and Scott derive an estimate of the status of a troop or population of Alouatta palliata by assigning values to a set of demographic parameters (values can easily be adjusted for other species). These authors suggest that one gauge of success in a population is the number of adult females relative to the number of juveniles plus infants (F:J + I ratio). While a dense population can arise from several causes in a disturbed environment, this ratio reflects the degree of reproductive success achieved over a period at least as long as the age to maturity. A minimal and tentative criterion for judging the status of a population or troop of howler monkeys is that there should be at least as many juveniles and infants as adult females. However, for many troops of rural rhesus monkeys, population stability is achieved only when the number of infants and juveniles equals or slightly exceeds the total number of adults of both sexes (Southwick and Siddiqi, 1968). In addition, female rhesus monkeys are thought to have a much longer life span than females of most or all of the New World species of primates, though age to sexual matur- ity is about the same for rhesus and cebids. Thus, among the howlers, and by extension other cebids, an F:J + I ratio of 1:1 may be an extremely conservative estimate for indicating that a population or a particular troop is adequately replacing itself. Only age-specific birth and death rates for a particular species in a particular habitat can securely supply the value of the replacement level of the F:J + I ratio. This symposium contributes significant new census data for several species. These figures are gathered and developed further in Tables 3 and 4 and compared with information from BCI. Neville's data (Table 3)
PROBLEMS AND POTENTIALS FOR PRIMATE CONSERVATION IN THE NEW WORLD 119 TABLE 3 Comparison of Three Censuses alAlouatta seniculus in a Comparable Area of Hato Masaguaral, Guarico, Venezuela8 One- Group Size Composition (%) Male Sub- Year and M:F F:I F:J + I F:S + J + I Troops adult Forest Area Range Mean Â± so M SM JM IM F SF JF IF I? (1:â ) (l:_) (i:_) (l:_) (%) (%) 1969-1970 4-14 8.5 Â± 2.5 19 10 9 8 30 3 12 9 1.57 0.56 1.25 1.69 54 51 1970 Western 5-10 6.9 Â± 2.4 21 5 14 0 34 5 13 7 .62 0.19 1.00 .31 55 45 Middle 4-12 8.5 Â± 2.4 18 11 15 7 29 2 9 8 .60 0.53 1.38 .81 62 53 Eastern 6-12 8.8 Â± 1.9 19 11 6 8 28 4 9 15 .50 0.80 1.33 .87 50 53 TOTAL 4-12 7.9 Â±2.3 19 10 12 5 30 3 10 10 .57 0.52 1.25 .68 55 51 1972 Western 4-11 7.9 Â±2.3 16 7 13 9 29 5 11 7 2 .78 0.63 1.44 .88 71 55 Middle 5-12 9.0 Â± 2.4 24 7 15 9 26 2 9 6 2 .08 0.64 1.57 .93 17 50 Eastern 7-15 9.0 Â±3.2 15 9 15 6 31 4 13 6 2 2.12 0.41 1.29 .71 67 54 TOTAL 4-15 8.6 Â±2.6 18 8 14 8 29 4 11 62 1.57 0.55 1.43 .83 53 53 LEGEND: M = male; F = female; S = subadult; J = juvenile; I = infant. â¢ Data from Neville. 1972. and 1976. from undisturbed troops of Alouatta seniculus show strong consistency from year to year in total numbers per forest and in the proportionality of the various age-sex classes. Especially notable are the very high F:J + I and F:S + J + I ratios. These figures are almost twice as high as comparable values from A. seniculus in La Macarena and from A. palliata from BCI and Costa Rica. Of interest also is the high proportion of one-male troops in the marginal dry forest environment of Santa Rosa, Costa Rica. Santa Rosa Ateles and Cebus seem in a depressed state compared to La Macarena Ateles and BCI Cebus population structures. It is clear that both field re- search and theoretical developments in the study of population structure deserve to be carried forward to provide a strong foundation for conservation and for investigations into primate ethology. PRESSURES ON PRIMATE POPULATIONS Although little is known about the population biology of New World primates, humans inflict three extraor- dinary pressures on these species: We capture them for pets or experimentation. We hunt them for food. We destroy their habitats over broad areas. Export Trade Happily, the wasteful and often inhumane pet trade in monkeys has largely ended. But this relaxation is balanced by the growing research endeavors in the USA, USSR, Japan, Western Europe, and elsewhere, which create an accelerating demand for primates as experimental animals. The testing of plastics, cos- metics, and Pharmaceuticals for toxicity and the stand- ardization of vaccines requires many more monkeys than basic biomedical research. Intensive efforts to find preventatives and cures for cancer, malaria, on- chocerciasis, and so forth can only increase scientific demands for primate exports. For the first time, Green elucidates in detail one export chain from first sale by the captor to the flight from Barranquilla, Colombia, to the USA. The stresses to the animals en route suggest that even if export for experimentation were the only pressure on the populations, some alteration in the export system will be required if resource management is to be effective. The capture of primates for use in research may be accomplished by several means, with differing effects on wild populations. The least-harmful techniques, often haphazard, are those that result in the removal of only a small portion of juvenile mon- keys without endangering future survival of the popu- lation. In other cases, the trapping is more efficient and more animals are removed, including some of the breeding adults. Or worst of all, adult females may be shot and their young captured, a practice obviously deleterious to a population. Hunting practices should be better documented and hunting regulations of differ- ent countries should be compiled and their varying effects on primate populations assessed. Primates as Protein It is now becoming apparent that far more severe pressures are placed on many primate species through hunting for food and through destruction of habitats
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122 HELTNE and THORINGTON than through the export trade. It is at this point that human politics, economics, and nutrition are ex- tremely relevant. Work on these topics, beyond the scope of this symposium, may be more crucial to the status of New World primate populations than studies of primates themselves. In some parts of Latin America, there is an immense and growing human consumption of monkeys as a major source of dietary protein. Pierret and Dourojeanni (1966) and Mel Neville and co-workers (reports to ILAR Committee on Conservation of Nonhuman Primates) show that each year large numbers of monkeys of several species appear on the Iquitos food market. For example, a minimum of 2,500 dried woolly monkey carcasses are sold annually for food in Iquitos (Neville, personal communication). Woolly monkey meat is also prized in many areas of Colombia according to Hernandez- Camacho and Cooper. Many of the monkeys taken for human consumption are eaten along the route to the major market centers. Therefore, we cannot account for the total number of monkeys consumed for meat. It is clear even from the minimal estimates available that this predation pressure is significant, and regionally it may be devastating to some species. In 1973, Peru effectively banned the sale of monkey meat in Iquitos and other major urban markets. Hunting monkey meat for one's family is still permitted and occurs widely. Agriculture The most serious threat to primates is the spread of both swidden and mechanized agriculture through the tropical forest in response to the food demands of the exploding local populations or the demands for beef for export to the developed countries. As farms are established, the forest is destroyed and with it the habitat for primates. Monkeys such as Lagothrix, which are restricted to primary forests, are eliminated immediately. Like some Old World species such as rhesus and talapoins, a few neotropical primates can make use of human crops. If fruit trees or small plots of banana replace the original forest, Cebus, Ateles, Saimiri, and possibly other species may fare quite well. Cebus will also consume maize. Cebus is con- sidered a crop pest in Colombia (Hernandez-Camacho and Cooper) and Saimiri and Cebus are hunted as pests in Panama (Baldwin and Baldwin). Moynihan believes that Cebuella may live, almost as a commen- sal of man, in small plots or hedgerows and fence lines, provided these contain sufficient sap-producing spe- cies. This raises the possibility that monkeys could be trapped for export from these pest or semidomestic populations. This is a possibility to be pursued along with the reservation of sizeable areas of natural habitat. Even though some New World species may make crossings from tree to tree on the ground, in the last analysis complete destruction of the forest is devastating for New World monkeys. Clearing of forests is frequently the direct result of a national development or reform policy. Even small tracts of forestland are by definition "unproductive" under the agrarian reform laws of many Latin Ameri- can countries. "Unproductive" land is taxed so heav- ily that most owners are forced to cut or bulldoze it, or yield the property in lieu of taxes to the government, which distributes it as part of the agrarian reform program. Land-hungry people promptly slash and burn the forest and plant. OLD WORLD PRIMATES We recognize that none of these problems are unique to the conservation of New World monkeys. In Asia and Africa, deforestation proceeds at a rapid pace, even in the absence of warfare. South wick (personal communication) indicates that in Malaysia the meat of the leaf monkeys (Presbytis obscurus, P. melalophus, and P. cristatus) is a great delicacy among the aborigines and Chinese. Monkey carcasses are com- monly sold in the meat markets in West Africa. In many areas primates may be exterminated because they are pests on human food crops. Nor is the knowledge of population parameters much more ad- vanced for the Old World primate species. Density estimates are available for small areas of Malaysia (Chivers, 1973; South wick and Cadigan, 1972), In- donesia (Rodman, 1973, Wilson and Wilson, in prep.), Gaboon (Gautier-Hion, 1973), Cameroon (Gartlan and Struhsaker, 1972), and for various locales for baboons (DeVore and Hall, 1965). Except for surveys near Delhi (Southwick and Siddiqi, 1968; Mukherjee and Mukherjee, 1972), such information is not available for the major supply areas of rhesus monkey export. Density estimates for Presbytis entellus from two areas in India appear in Sugiyana (1964). A summary of available population density estimates, not neces- sarily related to microdistributional parameters, is supplied by Jolly (1972). CONCLUSION The reduction of primate populations and their biolog- ical support systems has fortunately found recognition in the emerging conservation movements in many Latin American countries. While striving to set up adequate reserves for their uniquely rich flora and fauna, these nations are stringently limiting exports to prevent, if possible, the total loss of their splendid
PROBLEMS AND POTENTIALS FOR PRIMATE CONSERVATION IN THE NEW WORLD 123 national heritage. However, the cost of establishing, policing, and managing reserves is high. The cost of research outlined above is certainly significant. Money is also required to educate legislators to value stands of trees and to teach rural people to harvest monkeys in such a way as to secure a sustained crop. One possible source of funds would be a very high export tax on each primate leaving its country of origin. Attempts to breed rhesus monkeys in this country are producing animals costing between $500 and $1,000 each. This is several times the cost of a wild-caught animal delivered to the laboratory. Much of the cost of a wild-caught animal stems not from the value of the monkey as it leaves India but rather from expenses due to shipping, short-term quarantine, and minimal veterinary medical care in this country. Clearly, the Indian government could charge $300 or $400 per monkey and still export less-costly animals than those bred outside of India. No doubt an analo- gous situation pertains to the costs of breeding New World primates. (It is clear that the tax must be assessed at the point of departure, or the possibility of irresistible wealth for the rural woodsman would quickly lead to the total extinction of all wild primates.) In theory, the export tax could then help pay for the education of legislators and rural people, the purchase of reserves, and the general management of primate resources. It is hoped that countries possessing wild primates will recognize the extreme value of these assets, control them appropriately, and charge accord- ingly. Certain analogies between the crises in primate supply and oil supply will be apparent to most by this point. However, the microdistribution and abundance of primates has not been assessed with nearly the attention given to those parameters for oil. Oil is, of course, a nonrenewable commodity, while primates are a renewable resource. However, this ability of primates to reproduce themselves is highly dependent on some very important habitat requirements. Pri- mates are not only being harvested, but also the very ecological foundations for their capabilities of renew- ing themselves for further harvest are being destroyed. Institutional users of primates must act now to press for the soundest possible basis for management and control of natural monkey populations. This will often require what some like to call alpha-level biological research. The technical and scientific dividends that such studies can now pay are absolutely essential to continued investigation in other areas that utilize pri- mates as experimental animals. Both contractual and grant arrangements should be facilitated to bring the knowledge of the distribution, abundance, and status of primate resources up to the level of our knowledge of oil reserves. Possibly a United Nations conference is necessary to set up an international agenda for primate conservation and management. In terms of potential benefits to humans, the national and interna- tional value of primates as a biomedical resource deserves appropriate accounting. Even were it not so, the species and the places where they live are beautiful and precious in their own right. REFERENCES Bailey, R. C., R. S. Baker, D. S. Brown, P. von Hildebrand, R. A. Mittermeier, L. E. Sponsel, and K. E. Wolf. 1974. Progress of breeding project for nonhuman primates in Colombia. Nature 248:453-455. Bridgewater. D. D.. ed. 1972. Saving the lion marmoset. The Wild Animal Propagation Trust, Wheeling. W. Va. Brumback, R. A., R. D. Stanton, S. A. Benjamin and C. M. Lang. 1971. The chromosomes of Aotus trivirgatus Humboldt 1812. Folia Primatol. 15:264-273. Carpenter, C. R. 1964. Behavior in red spider monkeys in Panama. Pages 93-105 in C. R. Carpenter, ed. Naturalistic behavior of nonhuman primates. The Pennsylvania State University Press, University Park. Chivers. D. J. 1969. On the daily behavior and spacing of the howling monkey groups. Folia Primatol. 10:48-102. Chivers, D. J. 1973. An introduction to the socio-ecology of Malayan forest primates. Pages I0l-I46m R. P. Michael and J. H. Crook, eds. Comparative ecology and behavior of primates. Academic Press, New York. Collias, N. E., and C. H. Southwick. 1951. A field study of population density and social organization in howling monkeys. Proc. Am. Philos. Soc. 96:143-156. DeVore, I., and K. R. L. Hall. 1965. Baboon ecology. Pages 20-52 in I. DeVore, ed. Primate behavior. Holt, Rinehart and Winston. New York. Eisenberg, J. F., and R. W. Thorington, Jr. 1973. A preliminary analysis of a neotropical mammalian fauna. Biotropica 5:150-161. Gartlan, J. S., and T. T. Struhsaker. 1972. Polyspecific associations and niche separation of rain-forest anthropoids in Cameroon, West Africa. J. Zool. 168:221-266. Gautier-Hion, A. 1973. Social and ecological features of talapoin monkey-comparisons with sympatric cercopithecines. Pages 147-170 in R. P. Michael and J. H. Crook, eds. Comparative ecology and behavior of primates. Academic Press. New York. Handley, C. O., Jr. 1966. Checklist of the mammals of Panama. Pages 753- 795 in R. L. Wenzel and V. J. Tipton, eds. Ectopara- sites of Panama. Field Museum of Natural History, Chicago. Hernandez-Camacho, J.. and R. W. Cooper. 1976. The nonhuman primates of Colombia. This volume. Hershkovitz, P. 1949. Mammals of northern Colombia. Preliminary report number 4: Monkeys (Primates), with taxonomic revisions of some forms. Proc. U.S. Nat. Mus. 98:323-427. Hershkovitz, P. 1966. Taxonomic notes on tamarins, genus Saguinus (Callithricidae, Primates), with descriptions of four new forms. Folia Primatol. 4:381-395. Jolly, A. 1972. The evolution of primate behavior. The MacMillan Company, New York. Mason, W. A. 1968. Use of space by Callicebus groups. Pages 200-216 in P. C. Jay, ed. Primates. Holt, Rinehart and Winston, New York. Mukherjee, R. P., and G. D. Mukherjee. 1972. Group composition
124 HELTNE and THORINGTON and population density of rhesus monkey [Macaca mulatta (Zim- merman)] in northern India. Primates 13:65-70. Oppenheimer, J. R. 1968. Behavior and ecology of the white-faced monkey, Cebus capucinus, on Barro Colorado Island, Canal Zone. Ph.D. Thesis. University of Illinois. Urbana. Pierret, P. V., and M. J. Dourojeanni. 1966. La caza y la alimenta- tion humana en las riberas del rio Pachitea, Peru. Turrialba 16:271-277. Rodman, P. S. 1973. Population composition and adaptive organiza- tion among orangutans of the Kutai Preserve. Pages 171-209 in R. P. Michael and J. H. Crook, eds. Comparative ecology and behavior of primates. Academic Press, New York. Southwick, C. H., and F. C. Cadigan, Jr. 1972. Population studies of Malaysian primates. Primates 13:1-18. Southwick, C. H., and M. R. Siddiqi. 1968. Population trends of rhesus monkeys in villages and towns of northern India. 1959- 1965. J. Anim. Ecol. 37:199-204. Sugiyama, Y. 1964. Group composition, population density and some sociological observations of Hanuman langurs (Presbytis entellus). Primates 5:7-37. Thorington, R. W., Jr. 1968. Observations of squirrel monkeys in a Colombian forest. Pages 69-85 in L. A. Rosenblum and R. W. Cooper, eds. The squirrel monkey. Academic Press, New York.