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PRIMATE POPULATIONS IN CHIRIQUI, PANAMA John D. Baldwin and Janice I. Baldwin INTRODUCTION The purpose of this chapter is to describe the changes in primate habitats and populations in the province of Chiriqui, Panama, over the past two decades (Figure 1). The conditions in Chiriqui are similar to other parts of Latin America that are more economically and agriculturally advanced. Although the ecological con- ditions and primate resources in Chiriqui may not be representative of the current conditions in poorer, undeveloped, or remote areas, they do represent one facet of the current plight of primate populations in the New World where the government has endorsed ag- ricultural expansion rather than the protection of natural resources. The early parts of the chapter present data from primate surveys in several areas of Chiriqui. The latter sections deal with a single forest where we conducted an intensive study on primate ecology and behavior between December 19, 1970. and February 25, 1971. CHIRIQUI In August 1968 and December 1970, we surveyed 71 forested areas in Chiriqui, looking for primate groups (Figure 2). We obtained valuable overview information on primate locations from several hacienda owners and from Mr. Sigfrido Esquivel, who had once ex- ported animals from Chiriqui. When working in the field, location of animals was simplified with the help of the local people, who would indicate areas where animals could be found. In general, their reports were accurate. When groups were not located as reported, it was probably due to the animals having moved into forests or fields adjoining the area that was surveyed. Observations on the forests, troop size, and behavior were made with the naked eye and binoculars, then recorded on tape recorders or file cards, and later transcribed into field notebooks. The field procedures used are described in greater detail elsewhere (Baldwin and Baldwin, 1971, 1972. 1973). The main purpose of these observations was to locate a good site for conducting an intensive 10-week study on New World primates in a natural forest in Central America. The 10-week study was to be fo- cused on Saimiri sciureus oerstedii in order to com- pare their ecology and behavior with Saimiri that had previously been studied in the llanos of Colombia (Thorington, 1967, 1968) and in a seminatural envi- ronment in Florida (DuMond, 1968; Baldwin, 1968, 1969, 1971). While searching for forests containing Saimiri, we also encountered troops of Alouatta palliata (howler monkeys) and Cebus capucinus (capuchin monkeys). We found no evidence in the field that Saimiri lived in the mountainous northern part or in the eastern half of the province. Local people reported that Saimiri were to be found only in the southwest,* as confirmed by us, and reported that Alouatta and Cebus were more broadly distributed than our5a/w/r/-oriented investigations indicated. We never located or heard reference to other primate species in the areas studied, although W. C. O. Hill *Mr. Esquivel, the man who exported animals from Chiriqui in the I '<sn v said that once Saimiri had ranged as far east as Remedios in eastern Chiriqui. In 1968 we found no indication that Saimiri still ranged that far. 20
PRIMATE POPULATIONS IN CHIRIQUI, PANAMA 21 60 100 150 200 km PACIFIC OCEAN N FIGURE 1 The location of Chiriqui in southwestern Panama. (1960, 1962) indicated that Aotus trivigatus (night monkeys) and Ateles geoffroyi (spider monkeys) were once found in the province. Areas in which each species of primate was observed are indicated in Figures 3, 4, and 5. In southwestern Chiriqui it was possible to locate primates only in limited areas. Judging by the reports of many local people, the primate populations had diminished significantly during the two decades before 1968 through (1) clearing and fumigating the land for agriculture, (2) trapping for export, and (3) hunting by people. The Federal Register has placed Saimiri sci- ureus oerstedii on the endangered species list (Russell, 1970), but in the areas of Chiriqui we sampled Cebus were more endangered. EFFECTS OF AGRICULTURE The clearing and fumigating of land for agricultural use and pest control has been the major cause of the destruction of primates in Chiriqui. Chiriqui is one of the largest cattle producing and finishing provinces in Panama. It also is a major producer of rice, corn, cacao, coconuts, sugarcane, and bananas. Chiriqui contains large expanses of gently rolling and flat land with relatively high soil quality compared with other parts of Panama. In the 1920's a short railroad system was opened that made it possible to transport agricul- tural products to Puerto Armuelles for export by ship. In the 1950's Chiriqui became connected to the re- mainder of western Panama and the Canal Zone by an all-weather road. A system of sand, dirt, and some asphalt roads links various parts of Chiriqui and makes its back country more accessible to vehicles than is the case in most other agricultural provinces of Panama. Specific government policies have been inaugurated to facilitate and accelerate the economic development of the area and to encourage people to develop the land rather than to move to the cities. Between 1950 and I960 the population of Chiriqui increased from 138,136 to 188,350, and in the following 10 years it increased to 236,256 (Censos nacionales, I960, 1970). This is a population growth rate of 36 and 25 percent increase per decade. As a consequence of these and other factors, there has been a rapid economic development and a strong impetus to cut
22 BALDWIN and BALDWIN 10 20 30 40 50 km COSTA RICA CV. FIGURE 2 The province of Chlriqul in southwestern Panama. The forests that were investigated are indicated by dots. The four habitat zones designated by cross-hatching, from the least line density to the most, are areas over 200-m elevation, inland forests under 200 m, Burica Peninsula, and marshy coastal regions. The 10-week study conducted at Hacienda Barqueta is marked H.B. down the forests that once covered most of the prov- ince in order to create more land for farms and ranches (Legters et al., 1962). In 1950, Chiriqui was 6Q.7 percent forested. By 1960, the forests were re- duced to 50.4 percent (Censos nacionales, 1960). Doubtlessly many thousands of primates died as their habitat was destroyed. Several people reported that pesticides and other poisons were responsible for killing large numbers of primates and other small vertebrates. Because pesticides were used on both cleared land and many forested areas, primate popula- tions in otherwise unmolested forests were often af- fected . EXPORTATION Mr. Sigfrido Esquivel of David, Chiriqui, who is very familiar with primate resources in the province, pro- vided us with the following overviews. Between 1952 and 1960 he operated a small business collecting and exporting primates and other exotic animals. In the early 1950's Saimiri, Cebus, and Alouatta had been common in various areas of Chiriqui. By 1960, how- ever, many forests had been cleared for agricultural use and many of the remaining forests had been fumigated or trapped until only refugee primate popu- lations remained. The primates had become so scarce in the accessible parts of the province that they were no longer profitable to export. According to Mr. Esquivel, bands of monkeys still existed in numerous scattered areas; but larger, more natural troops existed only in relatively remote, inaccessible areas. Our observations in 1968 and 1970 confirmed that monkeys still exist only in scattered and/or remote areas. Mr. Esquivel reports that he was the only exporter in Chiriqui and that between 1952 and 1960 he ex- ported 500 Saimiri, 200 Alouatta, and 600 Cebus to the Canal Zone. A larger number of each species may have been trapped, however, since there are usually appre- ciable attrition rates before the trapped animals reach the exporters. From the Canal Zone the animals could have been exported to much farther destinations. Judging by personal observations in Panama in com- parison with observations in Leticia, Colombia, and
PRIMATE POPULATIONS IN CHIRIOUI, PANAMA 23 Iquitos, Peru, it seems likely that the collecting, cag- ing, holding, and transportation procedures used in Chiriqui and the Canal Zone between 1952 and 1960 were probably inadequate to guarantee the health of the animals. Given these conditions, it is probable that significant proportions of the animals could have died during the first months of captivity and transportation. The primates of Chiriqui were probably not utilized in scientific research. Cebus and Alouatta have never been used extensively in laboratory research. During the 1950's, when the major exportations were made from Chiriqui. Saimiri was not yet the popular labora- tory animal it became during the 1960's. Thus, the 1,300 monkeys that Mr. Esquivel exported from Chiriqui during the 1950's probably went to zoos and the pet trade rather than to laboratories. As Southwick et al. (1970) noted, it is important for the scientific commun- ity to be aware of the various causes behind the nearly global destruction of primate resources: We believe there is a danger of undue emotionalism about primate conservation before adequate field data are available. It is likely that biomedical research will receive the brunt of blame for many problems. When shortages of primates occur, the most convenient and visible scape goat is the research laboratory, (p. 1053) For the research community, the practical problem right now is to attach the blame for attrition of primate populations where it belongs; ... (p. 1054) HUNTING Hunting by the people is the third factor that might contribute to the destruction of primate populations in FIGURE 3 The locations where troops of Saimiri were found are shown with solid dots. The locations where no Saimiri were found are indicated by open circles. Lines represent the roads used.
24 BALDWIN and BALDWIN FIGURE 4 The locations where troops of AIouatta were found are shown with solid dots. The locations where no AIouatta were found are indicated by open circles. Chiriqui. There were no indications that primates in Chiriqui were commonly hunted for food in the recent past.* There were reports that some city dwellers occasionally killed a few monkeys for "sport." The local people were generally aware of nearby bands of monkeys and had a mild positive or joking affection for them. Some people claimed that the monkeys were nuisances, and a few offered to assist us if we wanted any killed. Of the three species, Cebus were generally con- sidered to be the worst pests and were most frequently spoken of as "bad." Cebus stole food and crops, as has also been reported by Oppenheimer (1969). Saimiri occasionally stole food; but this was less common, and *Although primates are not taken for food in Chiriqui, in parts of Amazonia and the llanos of Colombia Cebus and Alouatta are among the primates hunted for food by various indigenous peoples. the Saimiri were not considered to be as destructive as the Cebus. It is doubtful that local hunting was responsible for much of the recent decline in the primate populations in southwestern Chiriqui, but hunting has probably affected Cebus the most. The destruction of large expanses of forest habitat for agricultural expansion and the use of pesticides have been the main factors in the reduction of primate populations in Chiriqui. Exportation of primates for nonscientific use has been a minor factor. Hunting by local people is an additional minor factor that is difficult to evaluate. THE FORESTS Most of the three types of areas surveyed in this study were in the southwestern part of the province: the
PRIMATE POPULATIONS IN CHIRIQUI, PANAMA 25 inland lowlands, the Burica Peninsula, and the marshy coastline (Figure 2). The inland lowland areas (below 200 m or 650 ft) were the best suited for agriculture and were the most heavily exploited. The forests that remained in 1968 ranged between 0.2-40 ha (0.5-100 acres) and aver- aged 2-8 ha (5-20 acres) in size. Many forests were isolated by pastures and cultivated fields with few forests found near cities, towns, and the larger roads. The largest and most continuous tracts of forest were located along streams, rivers, and in less-accessible areas. Large haciendas tended to cut down sizeable sections of forest but leave untouched their more remote or less-valuable areas. Small landholders had smaller, scattered fields and often 0.2-4-ha (0.5-10 acres) forests remained between their cultivated areas. The larger forests in undeveloped areas of large haciendas were the least-molested lowland forests observed. The small forests scattered through other areas tended to consist of much second growth, scrub, and thickets that were penetrated by numerous trails or kept clear by the foraging of domestic cattle, swine, and other animals. Riverine forests or lines of trees that extended along streams, roads, and fences often served as connecting routes between small forests, and monkeys were observed to use these as routes to move from forest to forest. Numerous forests, however, were completely isolated from other forest areas. Only a small proportion of these 0.2-4-ha (0.5-10 acres) forest "islands" contained troops of monkeys. Many wire fences used posts made of freshly cut Spondias saplings that took root and made living fence lines, 3* Â°V â¢2U, FIGURE 5 The locations where troops of Cebus were found are shown with solid dots. The locations where no Cebus were found are indicated by open circles.
26 BALDWIN and BALDWIN which monkeys used for crossing between forests. Monkeys were also observed to cross the ground when forests were 5-20 m (16-65 ft) apart. The Burica Peninsula is not as flat as the remainder of southern Chiriqui. A 150-200-m (500-650 ft) high mountain ridge separates the Costa Rican side from the Panamanian side, and much of the terrain is steep and cut by gullies and streams. There are flat areas near the coastline and the southern tip of the penin- sula. There were no roads on the southern 24 km (15 miles) of the peninsula; but small boats could land along much of the coast, and foot and horse travel into Puerto Armuelles was common along the beach. Al- though there were a few large haciendas on the penin- sula, there were many small farms. Considering the ruggedness of the terrain, a surprising number of forests on the peninsula had been cut down. Flat areas had been opened for crops and pastures, and steep slopes had been cleared for cattle. The Costa Rican side of the Burica Peninsula was reported to be less developed than the Panamanian side. Nevertheless, on the Panamanian side there were numerous forest areas 0.4-16 ha (1-40 acres) that contained one, two, or all three species of primates. A distinct type of ecology exists on the islands and part of the coastline (Figure I). Extending parallel to the coastline and up to 3.2 km (2 miles) inland were expanses of hundreds or thousands of acres broken only occasionally by streams or clearings, and pene- trated by few trails. In these areas, marshes, thickets, scrub palms, trees, and mangrove swamps were com- mon in the lower, inundated areas. Medium tall forests (12-28-m trees) (40-90 ft) could be found in higher areas, such as along old dune lines located 0.2-1.5 km (0.1-1 mile) inland from the present shoreline dunes. The poor quality of the sandy soil, marshiness, and difficulty of landing boats made much of the marshy coastline relatively inaccessible and undesirable to humans. Therefore, we found these marshy coastal areas had the largest continuous undisturbed forests. We did not study on the islands, which are mostly mangrove and marshy, since they were described as places difficult to live in or work. However, all three species of primates were reported to inhabit the islands. The marshy coastline on the mainland was more easily studied and also contained relatively high concentrations of all three species of primates. This re- sulted in our selection of a coastal forest for the 10-week field study on primate ecology and behavior. THE PRIMATES In inland lowland forests, Cebus traveled in small bands of two-five animals that were very wary of man and fled in silence when approached. The wary be- havior could be a consequence of their being harassed, trapped, or hunted more frequently than in larger forests. Only on the Burica Peninsula and in the coastal forests were there areas where Cebus traveled in groups of 20 or more; in these troops a few animals made bold displays at humans while their troops meandered nearby or drifted away. Likewise, troops of Alouatta were small and scat- tered in the inland lowland forests compared with the Burica Peninsula and the coastal forests. On the penin- sula and especially in the marshy coastal areas. Alouatta could be found in troops of 10-30 animals. One could often see or hear several troops at once from an observation point near the edge of a forest. In disrupted areas Saimiri lived in larger troops than the other two species. In the inland lowlands, troops of 10-20 Saimiri could be found in forests as small as 0.8-2 ha (2-5 acres). The Saimiri ventured out into cornfields, banana plantations, and other crop and fallow lands in search of food or to make crossings between forests. On the Burica Peninsula and along the marshy coastlines, the Saimiri troops were more common and traveled in larger groups of 15-30 animals with the largest troop sizes occurring in the larger forests. If the present rate of agricultural expansion on the Burica Peninsula and in the marshy coastal forests continues, the primate populations and troop sizes will undoubtedly be diminished; and this situation will resemble the conditions in the inland lowlands. THE 1970-1971 STUDY FOREST The forest at Hacienda Barqueta was selected to be the locus of an intensive 10-week study (December 19, 1970, to February 25, 1971) on primate ecology and behavior, because it contained Alouatta, Saimiri, and Cebus and because it was remote from and relatively unmolested by people. The location of the study site is shown with an arrow marked H.B. in Figure 2. The study site consisted of a 20-ha (50 acres) subset of a continuous undisturbed forest of over 400 ha (1,000 acres) that extended 11 km (7 miles) parallel to the Pacific coast and varied from 0.4-1.6 km (0.25-1 mile) in width. The forest was bordered on the north by an estuary to the Escarrea River and on the south by dunes and grasslands that were flooded in wet season (Figure 6). In wet season, part of the forest floor was covered with water, but approximately 85 percent was elevated above the wet season high-water level. Sur- rounded by water most of the year, the study site was effectively isolated from human molestation, and species of animals rare elsewhere in southern Chiriqui were present in the forest. During the early weeks of
PRIMATE POPULATIONS IN CHIRIQUI, PANAMA 27 G.. GrassIand, fIooded in wet season FIGURE 6 The study site at Hacienda Barqueta. showing the trail system. the study. 8 km (5 miles) of trails were opened through the dense forest in order to follow the primates throughout the whole study area: 1 troop of Cebus capucinus, 2 troops of Saimiri sciureus oerstedii, and 11 troops ofAlouatta palliata. The number of animals of each species totaled 27 or 30 Cebus, 50 Saimiri, and approximately 210 Alouatta (Table 1). This represents a very high population density of primates compared with most primate populations reported in the litera- ture.* The compositions of Saimiri undAlouatta troops are presented in Table 2. The remainder of the 400-ha forest could not be easily surveyed, since we could not afford the time or effort to open a trail system like the one in the study forest. However, we found similar densities of pri- mates along the forest edge throughout the area and therefore believe that the population density found in the 20-ha study area was similar to that throughout hundreds, if not thousands, of acres of the marshy coastal forest. *The methodology used in studying Saimiri is presented in Baldwin and Baldwin. 1972; the methodology for Alouatta is in Baldwin and Baldwin. 1973. TABLE 1 The Population Size and Home Range Data for the Better-Studied Troops That Used the Study Site at Hacienda Barqueta Species and Troop No. of Animals Range Size Exclusive Range Cebus Hectares Acres Hectares Percent One troop 27-30 32-40 80-100 â â Saimiri Troop A 23 17.5 43.5 1.8 10.3 Troop B 27 24-40 60-100 â â Ahuatta" Planta 20 6.3 15.7 0.0 0.0 Boca IK 6.6 16.5 0.0 0.0 27-4-2 27 6.9 17.2 0.0 0.0 Pata 16 3.2 8.0 0.3 9.4 Saco 16 3.2 8.0 0.28 8.8 7-2-0 7 â â â â Cola 28 3.5 8.7 1.2 34.3 L.D. 19 4.2 10.5 â â Solitaries 6 " Three additional troops of Ahuatta used the 20-ha study site, but we were unable to collect sufficient data on them to obtain accurate troop counts.
28 BALDWIN and BALDWIN TABLE 2 The Troop Compositions of the Saimiri and Alouatta Troops That Were Well Studied Species and Troop Troop Size Adult Males Subadult Adult Males" Females" Juve- niles" In- fants Percentage Ratios Adult Females with Infants (%) Saimiri Troop A 23 3 2 6 7 5 13:09:26:30:22 83.3 Troop B 27 2 3* 7* 9* 6 07:11:26:33:22 85.7 Average 10:10:26:32:22 84.7 Alouatta Planta 20 6 â 7* 4* 3 30:35:20:15 42.9 Boca 18 2 8* 5* 3 11:44:28:17 37.5 27-4-2 27 4 12** 6** 5 15:44:22:19 41.6 Pata 16 3 7 2 4 19:44:12:25 57.2 Saco 16 4 7* 3* 2 25:44:19:12 28.6 7-2-0 7 2 3* 2* 0 29:43:29:00 00.0 Cola 28 6 13** 3** 6 21:46:11:21 46.1 L.D. 19 4 â 7* 5* 3 21:37:26:16 42.9 Solitaries 1 1 4 Average Troop 21:42:20:17 40.6 * Since we had difficulty in discriminating reliably between older juveniles and young adult females without infants, the data presented are best estimates. One asterisk indicates an estimate of Â±1 accuracy. Two asterisks indicates an estimate with Â±2 accuracy. At the study site, the Saimiri and Alouatta habituated to our presence in the first 2 weeks of work; thereafter, continuous observations could be made from 7-15 m (23-50 ft) without disturbing the animals. The rapidity of this habituation process supports the impression that these two species had not been molested by man in the recent past. The Cebus, however, did not habituate well; even at the end of the study they became wary whenever humans ap- proached within ranges of 15-30 m (50-100 ft). Adult Cebus occasionally threatened us, shook and dropped branches, and gave the gyrrah vocalization described by Oppenheimer (1968). Some local people said that two Cebus had been trapped nearby some years ago. REFUGEE POPULATIONS From the divergent stories of numerous local people it was difficult to piece together a consistent picture of the history of the area around the study forest at Barqueta. Apparently, slash and burn techniques had been used to open croplands north of the marshes for many decades. More recently, tractors and bulldozers speeded the process. However, as late as I960 con- tinuous or adjoining forests of up to 40 ha (100 acres) were still common throughout the area. As these forests were further destroyed in the 1960's, probably many primates became trapped in isolated small forests and others migrated into the uncut forests. Even during the study, one to four men worked several days a week with machetes and fires clearing sections of forests near the study site. In some cases, the monkeys were trapped in isolated stands of trees where they might have starved to death. During the study, however, all three species were observed to cross between forests on the ground. Among the Alouatta, injured and isolated animals made terrestrial crossings up to 75 m (250 ft) through tall and short grass between forests. Healthy Alouatta belonging to integrated troops rarely made ground crossings longer than 5 m (16 ft). Cebus and Saimiri were not observed to make ground crossings longer than 20 m (65 ft) and 12 m (39 ft) respectively. The high degree of separation of most of the forests in southern Chiriqui in 1970 would suggest that primate populations living more than 1.5-2.5 km (1-1.5 miles) inland from the marshy coastal forests probably could not have reached the Barqueta study forest unless they lived along the Escarrea River, which parallels a forest for several miles from the coast. There were, however, many areas adjacent to the Barqueta study forest that had once been forested, suggesting the animals re- treated into the remaining forests. Every 1 km2 of remaining forest in 1970 could have received monkeys from 1-3 km2 of adjacent land where forests were destroyed over the past decades. We suspect that over the years there has been a slow and gradual tendency for refugee monkeys to drift into the protected coastline forests and to create a slow rise in the population density there. The Alouatta, whose diet was leaves, fruits, and flowers, had adequate food supplies in the coastal forests. They apparently
PRIMATE POPULATIONS IN CHIRIQUI, PANAMA 29 adapted to living in small home ranges averaging 4.8 ha (12.1 acres) with an overlap of between 65.7 and 100 percent, averaging 94 percent overlap. The population density at Barqueta was 21 times as high as the population density on Barro Colorado Island in 1932 and 12 times that of 1967 (Carpenter, 1934; Chivers, 1969). Yet, the Alouatta at Barqueta showed no signs of increased aggression or pathological behavior in comparison with the Alouatta on Barro Colorado Island. Fertility was normal: 41 percent of the adult females at Barqueta had infants compared with 37 percent on Barro Colorado Island in 1932, 49.5 percent in 1933, 26.7 percent in 1951, and 41.7 percent in 1967 (Carpenter, 1934: Collias and Southwick, 1952; Chiv- ers, 1969). The Alouatta had sufficient food sources, even in dry season, when several of their food trees lost their leaves. There were few signs of botfly infestations, and all the animals (except two injured solitary juveniles) appeared to be healthy and strong. Two troops ofSaimiri shared the study forests. The diet of Saimiri consisted of insects and certain fruits. In contrast with Alouatta, the Saimiri had a very limited food supply at Barqueta, at least during the 3 months of the study. Animals of all age-sex classes in both troops spent 95 percent of each hour of the 14-hour waking day engaged in foraging and traveling between foraging locations. The Saimiri took no mid- day rest periods in the heat of the day, as they do in other environments (Baldwin, 1967; Thorington, 1968); they seldom rested more than 60 seconds at a time; and they were never observed to engage in a single bout of social play. Insect foods were rarely found, and the monkeys ate larger quantities of plant food than has been reported for the species in other environments (Fooden, 1964; Thorington, 1967, 1968). The principal food sources were the fruits of the cactuslike plant Aechmea and the palm Scheelea cf. zonensis, which grew in dense clusters and took 15-120 seconds to locate and/or pick. Because ripe fruits were concentrated on single plants, the whole troop often came together within a 180-m2 (215 yd2) area. This contrasts markedly with the troop observed by Thorington (1967, 1968) on the llanos of Colombia, where Saimiri fed on small, dispersed canopy insects, and the troop tended to split up into subgroups that foraged in different directions at different rates. As refugee groups of Saimiri have moved into the remaining Barqueta forests, probably starvation and disease have kept their numbers in balance. If the population changes have been gradual rather than erratic, the population density of 13 Saimiri per 10 ha (25 acres) may represent the maximum population density for the Barqueta ecology. The hacienda own- ers at Barqueta said that before the insecticide spray- ing, Saimiri were much more abundant throughout the forests. The owners reported in 1971 that it had been approximately 10 years since their forests were last sprayed. It was difficult to assess the population density of the Cebus. Only one troop was observed at the study site, and its home range was larger than the study area. Whether it had territorial conflicts with adjacent troops could not be determined. Oppenheimer (1968) found that Cebus on Barro Colorado Island traveled in groups of 15 and defended territories of approximately 85.2 ha (213 acres). At Barqueta the home range of the one troop of 27 or 30 Cebus was probably around 32-40 ha (80-100 acres). The larger troop size and smaller home range size may reflect crowding due to an influx of refugee populations. The Cebus did not appear to be as hungry as the Saimiri, though they did spend 50-70 percent of their day foraging and travel- ing. No abnormal or unusual behaviors were noted. However, a Cebus was observed to attack a 1.7-m (5.6 ft) iguana, wrestle with it for 30 seconds, and break off 3O40 cm (12-16 in.) of its tail. The iguana fell 12-15 m (40-50 ft) to the ground and scurried away, while the Cebus ate the meat off the tail fragment. This is the largest animal known to be attacked by Cebus. Table 3 shows the arboreal mammalian biomass in the study forest. At Barqueta, where the population density was relatively high compared with most pri- mate ecologies. Alouatta comprised 84 percent of the arboreal mammalian biomass. Eisenberg et al. (1972, p. 869) point out: "Not surprisingly the ar- boreal folivores are the most numerous of larger forest mammals, sometimes accounting for 30-40 percent of the arboreal mammalian biomass." The higher percent- age at Barqueta probably reflects the high population density. LAND CLEARING In early 1972 a portion of the 400-ha forest surrounding and including the study site was bulldozed to the ground. The owners of the hacienda, Mr. and Mrs. Julio Arauz, wrote that they were under pressure from the local government to make "profitable" use of their forested lands or have the lands taken over under the government land reform laws. Mr. C. Neal McKinney, Administrative Officer of the Smithsonian Tropical Research Institute in the Canal Zone, has confirmed that "implementation of an old land reform law has been speeded up by the present military government" (1972, personal communication). As a consequence, the hacienda owners cut most of the tall forests on the higher ground and turned the land to cattle-grazing pasture. The Arauzes reported that some monkeys
30 BALDWIN and BALDWIN TABLE 3 The Biomass of the Known Arboreal Mammals at the Study Site Species Kg/Ha Total (%) Alouatta (howlers) 44.60 84.0 Cebus (capuchins) 1.83 3.4 Saimiri (squirrel monkeys) 0.69 1.3 Bradypus (sloths) 0.53 1.0 Microsciurus (squirrels) 0.17 0.3 Nasua" (coatis) 5.25 10.0 TOTAL 53.07 100.0 â¢ Nasua traveled, foraged, and rested arboreally around 25 percent of the daylight hours. The percent of Iheir food intake that came from arboreal sources is unknown. were killed during the bulldozing. Others, however, retreated into adjacent low marshy areas containing mangrove and scrub forests, where many were dying of starvation. During our field observations, it was clear that the Alouatta and Saimiri spent very little time in the mangrove and marshy scrub forests. The Cebus, however, spent at least 50 percent of their time in and around the mangrove areas. Although the Cebus may be able to adapt to the new circumstances, it can be assumed that the other two species will be more heavily affected by the destruction of their preferred habitat. SUMMARY In August 1968 and December 1970, the authors sur- veyed primate populations in 71 forested areas in the province of Chiriqui in southwestern Panama. Troops of squirrel monkeys (Saimiri sciureus oerstedii) were found in 20 areas, troops of howling monkeys (Alouatta palliata) were found in 27 areas, and troops of capuchin monkeys (Cebus capucinus) were found in 10 areas. The inland lowlands below 200-m altitude have been developed extensively for agricultural use, and the few primate troops that remained in these areas were small, scattered, and often afraid of man. On the Burica Peninsula there has been less agricultural devel- opment, and larger troops were more abundant. The marshy coastal areas that extend along part of Chiriqui's coast have been least affected by the rapid agricultural development in the province. These areas contained the largest primate populations. Between December 19, 1970, and February 25, 1971, the authors conducted a 10-week study on the ecology and behavior of the three species of primates in an extensive coastal forest. The population density of Alouatta was 104 animals per 10 ha (25 acres), which was 21 times greater than Carpenter observed on Barro Colorado Island in 1932 and 12 times greater than Chivers observed there in 1967 (Carpenter, 1934; Oiivers, 1969). The troops' home ranges overlapped extensively, leaving an average of only 6 percent of one troop's home range for its exclusive use. There were no signs that the Alouatta were (1) exhausting their food supply of leaves, fruits, and flowers; (2) experiencing decreased fertility; or (3) suffering pathological effects from the high population density. The Saimiri, on the other hand, were living in starva- tion conditions at the population density of 13 ani- mals per 10 ha (25 acres). The insects and fruits that normally comprise the Saimiri''s diet were very scarce at Barqueta, and the Saimiri spent 95 percent of every waking hour engaged in foraging and traveling between foraging areas. This restricted the frequency of social interactions among them compared with other natural and seminatural environments. The Cebus did not habituate well to humans and could not be studied as closely as the other two species. One troop of 27 or 30 Cebus used about 32-40 ha (80-100 acres), creating a population density four times greater than that reported for the Cebus on Barro Colorado Island (Oppenheimer, 1968). Data presented suggest that the high population densities at the coastal study site may have been a consequence of the influx of refugee populations from once-forested areas to the north, as those areas opened for agriculture over the past 20 years. In 1972 the study forest was bulldozed to the ground in order to open more land for cattle pasture. Panama- nian land reform laws are encouraging the destruction rather than the conservation of many forested areas in order to encourage agricultural development and economic growth. Primate populations have been re- duced significantly as their habitats have been de- stroyed and as pesticides have been introduced into agricultural usage. If the present rate of economic development continues and no attempt is made to protect the wildlife, the primate populations in south- western Chiriqui will be endangered in the near future. A national park or wildlife refuge is needed to preserve some portion of the flora and fauna in these areas. ACKNOWLEDGMENTS We would like to thank the following persons who aided our work: Mr. and Mrs. Julio Arauz, the owners of Hacienda Barqueta. who generously permitted us to use their forests, open trails, and conduct the 10-week study without interference; Mr. Sigfrido Esquivel, who provided information on primate conditions in Chiriqui; Dr. Richard Thorington, Jr., who provided the original information on the location of Saimiri in Costa Rica and Panama; and Dr. Martin Moynihan, who arranged for our trip to the Burica Peninsula.
PRIMATE POPULATIONS IN CHIRIQUI, PANAMA 31 REFERENCES Baldwin, J. D. 1967. A study of the social behavior of a semifree- ranging colony of squirrel monkeys (Saimiri sciureus). Unpub- lished doctoral thesis. Johns Hopkins University. Baldwin, J. D. 1968. The social behavior of adult male squirrel monkeys (Saimiri sciureus) in a seminatural environment. Folia Primatol. 9:281-314. Baldwin, J. D. 1969. The ontogeny of social behavior of squirrel monkeys (Saimiri sciureus) in a seminatural environment. Folia Primatol. 11:35-79. Baldwin. J. D. 1971. The social organization of a semifree-ranging troop of squirrel monkeys (Saimiri sciureus). Folia Primatol. 14:23-50. Baldwin, J. D., and J. I. Baldwin. 1971. Squirrel monkeys (Saimiri) in natural habitats in Panama, Colombia, Brazil and Peru. Pri- mates 12:45-61. Baldwin, J. D., and J. I. Baldwin. 1972. The ecology and behavior of squirrel monkeys (Saimiri oerstedi) in a natural forest in western Panama. Folia Primatol. 18:161-184. Baldwin, J. D.. and J. I. Baldwin. 1973. Interactions between adult female and infant howling monkeys (Alouatta palliata). Folia Primatol. 20:27-71. Carpenter, C. R. 1934. A field study of the behavior and social relations of the howling monkeys (Alouatta palliata). Comp. Psychol. Monogr. 10:1-168; reprinted in C. R. Carpenter. 1964. Naturalistic behavior of nonhuman primates, pp. 3-92. Pennsyl- vania State Univ. Press, University Park. Censos nacionales de 1960 de Panama. Panama: Direccion de Estadistica y Censo. Censos nacionales de 1970 de Panama. Panama: Direccion de Estadistica y Censo. Oiivers, D. J. 1969. On the daily behaviour and spacing of howling monkey groups. Folia Primatol. 10:48-102. Collias, N. E.. and C. H. Southwick. 1952. A field study of population density and social organization in howling monkeys. Proc. Am. Philos. Soc. 96:143-156. DuMond, F. V. 1968. The squirrel monkey in a seminatural envi- ronment. Pages 87-145 in L. A. Rosenblum and R. W. Cooper. eds. The squirrel monkey. Academic Press, New York. Eisenberg. J. F.. N. Muckenhirn. and R. Rudran. 1972. The relation between ecology and social structure in primates. Science 176:863-874. Fooden, J. 1964. Stomach contents and gastrointestinal proportions in wild-shot Guianan monkeys. Am. J. Phys. Anthropol. 22:227- 231. Hill, W. C. O. 1960. Primates, vol. IV, part A. Edinburgh Univ. Press, Edinburgh. Hill, W. C. O. 1962. Primates, vol. V, part B. Edinburgh Univ. Press, Edinburgh. Legters, L. H., W. Blanchard, E. E. Erickson, B. C. Maday, N. S. Popkin, and S. Teleki. 1962. Special warfare area handbook for Panama. U.S. Government Printing Office, Washington, D.C. Oppenheimer, J. R. 1968. Behavior and ecology of the white-faced monkey, Cebus capucinus, on Barro Colorado Island, C.Z. Uni- versity Microfilms, Ann Arbor, Michigan. Russell, F. J. 1970. Conservation of endangered species and other fish and wildlife. Federal Register 35:8491-8498. Southwick, C. H., M. R. Siddiqi, and M. F. Siddiqi. 1970. Primate populations and biomedical research. Science 170:1051-1054. Thorington, R. W., Jr. 1967. Feeding and activity of Cebus and Saimiri in a Colombian forest. Pages 180-184 in D. Starck, R. Schneider, and H.J. Kuhn.eds. Neueergebnissederprimatologie. Gustav Fisher Verlag, Stuttgart. 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.