An ecological study of troop fissions of Japanese monkeys (Macaca fuscata yakui) on Yakushima Island,Japan

Wild, habituated, Japanese monkeys were observed from 1975 to 1979 on Yakushima Island, Southern Japan. The monkey troops had a continuous distribution in a warm temperate forest. Demographic data on local populations was collected. The population density was 33 animals/km². The growth rate of the studied troop was 3.0% per year. A significant correlation between home range areas (R) and troop size (P) was found (r=0.955,p<0.005), using anR-P equation,R=1.84P. One troop split into three troops through two successive fissions. Twenty-one intertroop encounters were observed. Five types of encounters were distinguished. The encounters were apparently territorial defence. Increases in birth rate and socionomic sex ratio after the fissions were prominent. The following four factors had a direct effect upon the dispersion of the troops after fission: (1) dominance relation between the fission troops; (2) social pressure of the neighbors; (3) troop's attachment to its home range; and (4) structure of the environment. The home range of Japanese monkeys is a territory, and territoriality is a population regulating mechanism which serves to reduce competition for food.     

Resource patch size and flexible foraging in white-faced capuchins (Cebus capucinus)

White-faced capuchins (Cebus capucinus)on Barro Colorado Island, Panama, have a flexible foraging strategy. Typically, foraging party size is small and individuals feed dispersed from one another. When seasonal fruiting of large volume trees occurs, the majority of the group forages simultaneously. As C. capucinusdo not display a rigorous dominance structure and there are few indications that individuals or coalitions monopolize food patches,individuals are expected to display scramble strategies instead of high frequencies of contest competition. I recorded foraging party size (simultaneous foragers), the total number of animals to feed successively, and the diameter at breast height (DBH) of fruit trees used in two habituated troops. Individuals in each group spent a substantial amount of time — 65 and 48% of foraging time for each group — foraging in party sizes of one. Monkeys predominantly foraged alone in small trees (0- to 20- cm DBH), successively in medium trees (21- to 60- cm DBH), and simultaneously in large trees (>61- cm DBH). They used small trees more frequently than all other tree classes. In medium-sized trees, although fruit was plentiful, space was limited. In these trees Cebusforaged successively. In large-volume trees, space and fruit were abundant and several individuals fed together. As the DBH of fruiting trees increased, the average foraging party size increased exponentially. Cebus capucinusat Barro Colorado Island modify their foraging party size to adapt to the seasonal patterns of fruit production.     

A new method for censusing animal populations: The number of Eciton burchelli army ant colonies on Barro Colorado Island,Panama

Summary A new technique for estimating the size of an animal population is described. This technique is used to provide an up to date estimate of the number of colonies of the army ant Eciton burchelli on Barro Colorado Island, Panama. There have been approximately 50 colonies of this species on Barro Colorado Island for more than thirty years. The relative constancy of this population is contrasted with the great temporal variability of other tropical insect populations.     

Habitat selection and seasonal patterns of activity and foraging of mantled howling monkeys(Alouatta Palliata) in Northeastern Costa Rica

I conducted a 15- month ecological study of habitat preferences and activity and foraging patterns of two troops of mantled howling monkeys, Alouatta palliata,in a lowland rain forest at La Selva Biological Reserve in northeastern Costa Rica. The two troops specialized on different habitats in spite of the fact that both of them had all habitats available and were not constrained by neighboring troops since the population density of howlers is low (7- 15 howlers/km ² ).Troop 1 spent the majority of time in primary forest (80%) followed by secondary forest (10%), while troop 2 spent the majority of time in undisturbed riparian habitat (60%) followed by primary forest (30%). Habitat sampling indicates that neither the total number of stems, species, or families nor the diversity (Shannon index) or evenness is a good indicator for howler habitat selection. Instead the density of trees from the 12 species most commonly consumed by each troop is the most important factor. Activity and foraging patterns were not dependent upon the season as has been described for howling monkeys in forests with a more pronounced dry season at Barro Colorado Island, Panama, and La Pacifica in northwestern Costa Rica. This is likely a result of the more constant food supply at La Selva, combined with less intraspecific competition due to the low howler density. The intraspecific variability of foraging patterns and troop- specific habitat specialization observed in Alouatta palliatashould be considered in the conservation biology of primates. Primate relocation programs should include not only an ecological assessment of the release site but also a comparison of the release site with the habitat that the groups currently occupy.     

Population ecology of the white-nosed coati (Nasua narica) on Barro Colorado Island, Panama

The white-nosed coati, Nasua narica , is a common Neotropical carnivore with a social structure of band-living adult females and solitary adult males. A coati population on Barro Colorado Island, Panama, was studied over a four-year period by mark-recapture, radiotelemetry. and direct observation of habituated individuals. The population density was approximately 51.5 individuals/km² and the sex ratio was 1:1. Band size varied from six to 26 individuals (mean = 15.3) with extensive fluctuation within and between years. Mean foraging group size was smaller (7.2 individuals) than population group size, and fluctuated with food availability, synchronous parturition, and the emigration of mature males. Mean home-range size of six bands was 0.33 km², and ranges of adjacent bands overlapped from 0–66%. One band fissioned during the study; however, the resulting bands did not disperse from the original home range. Seven adult males had a mean home-range size of 0.37 km², each extensively overlapping the home ranges of several other males. Observations of 10 adult males whose natal bands were known indicate that when males disperse they do not simultaneously leave the band's home range. Rather, their home ranges remain within or broadly overlapping those of their natal bands. This dispersal pattern is unusual within the order Carnivora.     

The demography of Howler Monkeys (Alouatta palliata) on Barro Colorado Island,Panamá

Chronological ages of Alouattaon Barro Colorado Island (BCI) were estimated from longitudinal dental wear. Combining these data with visual censuses, we approximated the study population’s age profile. A stable model was then constructed; from it we derived agespecific mortality rates. Mortality of immature animals is high, with 88% of the males and 65% of the females dying before 5 years. Adult mortality is low until 11 years, when it accelerates. The average adult life span is 16.6 years for males and 15.5 for females. The maximum life span is over 20 years. A pubertal male growth spurt occurs from 3 to 5 years, at which time females are primiparous. Sexual size differences develop primarily during this time. The 1976 age profile had anomalously few animals aged 7 years and males aged 8–9 and 15–16 years. With corroborating evidence, we hypothesize that these deficits resulted from excessive rainfall in 1963 and 1971, which reduced the fall fruit crop and led to a high juvenile mortality. Within half of our study troops, some adult males have nearly identical ages, suggesting an active process of agemate coalition. We hypothesize a form of kin selection, wherein peripheral male cohorts from the same natal troop have greater survival and social success than solitary animals. The stable model suggests an annual growth rate of 1.5% during the 1970s. Estimates of 16.7 and 4% for the previous two decades, following a yellow-fever epidemic, imply that the BCI population is becoming stationary. A very different age structure existed on neighboring Orchid Island in 1976, suggesting general food limitation. By contrast, the lowered, but continuing growth on BCI suggests a less drastic limiting mechanism. We hypothesize that intratroop social competition limits population growth by regulating subadult survival rates during food scarcity cycles.     

Ocelots on Barro Colorado Island are infected with feline immunodeficiency virus but not other common feline and canine viruses

Transmission of pathogens from domestic animals to wildlife populations (spill-over) has precipitated local wildlife extinctions in multiple geographic locations. Identifying such events before they cause population declines requires differentiating spillover from endemic disease, a challenge complicated by a lack of baseline data from wildlife populations that are isolated from domestic animals. We tested sera collected from 12 ocelots (Leopardus pardalis) native to Barro Colorado Island, Panama, which is free of domestic animals, for antibodies to feline herpes virus, feline calicivirus, feline corona virus, feline panleukopenia virus, canine distemper virus, and feline immunodeficiency virus (FIV), typically a species-specific infection. Samples also were tested for feline leukemia virus antigens. Positive tests results were only observed for FIV; 50% of the ocelots were positive. We hypothesize that isolation of this population has prevented introduction of pathogens typically attributed to contact with domestic animals. The high density of ocelots on Barro Colorado Island may contribute to a high prevalence of FIV infection, as would be expected with increased contact rates among conspecifics in a geographically restricted population.     

Ecological study of the saddle backed tamarin (Saguinus fuscicollis) in Northern Bolivia

The author carried out an ecological survey of the saddle backed tamarin (Saguinus fuscicollis) in the Pando, northern Bolivia, from July to December 1979. It was found thatS. fuscicollis formed a family group consisting of two to seven individuals and spent almost all the daytime in moving to forage insects, although it fed mainly on fruits of the family Moraceae. Primary forest was preferred for sleeping sites, whereas the animals spent more hours in secondary forest than in primary forest in their home range. Marking sites were concentrated in the center of the home range but encounter behaviors tended to take place near the borderlines of the home range. It was also found that infants began feeding on fruit at about 5 weeks of age, whereas they shared insects obtained by their mothers until about 10 weeks of age.     

Long-term ecology of euglossine orchid-bees (Apidae: Euglossini) in Panama

Summary Abundance patterns during 6–7 years and orchid visitation were determined for 51 species of the 57 local euglossine bees. Male bees were counted at 3 chemical attractants presented in the same manner each month. Sites were separated by 75 km but included wet Atlantic forest at 500 m elevation, moist forest at 180 m near Barro Colorado Island, and cloud forest at 900 m near the Pacific ocean. 1. From 15 to 30 euglossine species of 4 genera were active in each month and site; monthly species number and general bee abundance were positively correlated. Many species had 3 annual abundance peaks (range 1–4) and were active throughout the year, but peak annual abundances rarely occurred during late wet or early dry seasons. In contrast, Eufriesea generally were present as adults only 1–2 months in a year. 2. Euglossine populations were exceptionally stable. Species at each site were more stable than any known insect population, and stability and abundance were positively associated. However, year-to-year population stability and the degree of seasonality were not correlated. Among the three sites, the more diverse (species rich) bee assemblages displayed lower stability; these were the wetter and upland sites. 3. The most abundant bees visited more orchid species. Eg. and El. each visited and average of 4 orchid species (range 0–13); Ex. and Ef. visited 0–3. Stable populations did not visit more or fewer orchid species than did unstable populations. 4. Less than 68% of species at each site visited orchid flowers; less than a few dozen of the 100–800 bees counted in a day carried orchid pollinaria. Over 20% of the euglossine species never were seen with pollinaria at any site and probably seldom visit orchids in central Panama. 5. Most bee species visited 1 or no fragrance orchids in a given habitat. Orchids tended to utilize common pollinators that seldom included more than 1 species, and they utilized stable or unstable, seasonal or aseasonal bees. However, the most stable and abundant bee, Eg. imperialis, rarely pollinated orchids; fewer than 10 of ca. 20000 bees carried pollinaria. 6. Orchids may interact primarily with discrete seasonal bee population peaks-probably the emerging adults. Although specialized orchid preferences are implicated for species that visit few or no local orchids but pollinate other species and carry pollinaria in other areas, euglossine bees do not need orchids to survive or reproduce.     

Herbivory Rate of Leaf-Cutting Ants in a Tropical Moist Forest in Panama at the Population and Ecosystem Scales

Leaf-cutting ants are frequently characterized as the major herbivores in the Neotropics, but quantitative data to back up this assumption are scarce. In this study, the consumption and herbivory rates for the entire leaf-cutting ant ( Atta colombica , Formicidae) population in an old secondary forest on Barro Colorado Island (BCI) in Panama were determined over 15 mo (on average 49 colonies). The number of harvested leaf fragments was calculated from monthly refuse deposition rates of the colonies and the regression between refuse deposition and harvesting rates. The inclusion of fragment characteristics (proportion of leaf fragments in the harvest, average fragment weight, and area) allowed us to calculate consumption and herbivory rates at colony, population, and ecosystem levels. The A. colombica population harvested 13.2 tons of biomass/yr and 13.1 ha of leaf area/yr, and deposited 9.4 tons of refuse material/yr. Rates varied considerably among colonies. At the ecosystem level, i.e. , per forest area, herbivory rates were 132 kg biomass/ha/yr and 1310 m² foliage/ha/yr. For the area on BCI where A. colombica occurs (100 ha), this is equivalent to 2.1 percent of the foliage area in the forest or 1.7 percent of the annual leaf-area production. This value is considerably lower than previously published estimates of leaf-cutting ant herbivory rates in tropical forests.     

Copulation-interrupting behavior between females within a howler monkey troop

On Barro Colorado Island, Panama, howler monkeys (Alouatta palliata) were observed copulating on numerous occasions. In one case, however, the copulation was interrupted by a female member of the same troop. This newly reported behavior may be a social mechanism related to high population densities. Supported by the Environmental Sciences Program, Smithsonian Institution; and the National Zoological Park, Washington, D.C.     

Ranging patterns of Japanese macaques in the coniferous forest of Yakushima: Home range shift and travel rate

Ranging is one of the most important behavioral adaptations for coping with seasonally fluctuating food and thermal conditions. We studied the ranging patterns, in particular home range shift and travel rate of Japanese macaques (Macaca fuscata) in the coniferous forest of Yakushima by tracking a group for 17 months. We also supplemented our data with records collected every August over a 5-year annual census. The macaque group used the eastern part of their home range from May to September and the western part during the rest of the year. The eastern part of the home range was largely primary forest in the national park, and the altitude was higher than in the western part. When they used the western part, the macaques ate more herbs and fruits from small-sized trees, the availability of which was higher in the logged forest. This east–west home range shift occurred repeatedly over multiple years. A neighboring group occupied the western part of the focal group's home range in summer, which the focal group did not use in that season. Both temperature and diet affected seasonal changes in the monthly average travel rate. Animals need more energy for thermoregulation when the temperature is low, so the macaques decreased their ranging efforts to save energy at times of low temperature. They increased their ranging distance to eat fungi, since their encounters with this food would increase with the total distance walked. They also increased their travel rate when eating flowers, which had lower food patch (tree) density than other foods such as fruits. The data supported the hypothesis that the macaques capitalize on habitat heterogeneity in a seasonally fluctuating habitat by shifting their home range and modifying their travel rate.     

Growth of Mantled Howler Groups in a Regenerating Costa Rican Dry Forest

We examined population dynamics in mantled howlers (Alouatta palliata palliata) in a regenerating tropical dry forest in Santa Rosa National Park (SRNP), Costa Rica. The population has grown at a rate of about 7% per annum during the past decade. The growth in numbers from 342 in 1984 to 554 in 1992 reflects an increase in the number of groups (from 25 to 34) and a slight increase in their average size (from 13.6 to 16.3). Population density has increased from 4.9 to 7.9 individuals per km ². Santa Rosa's population density and group compositions are similar to those at several other mantled howler sites, but densities of mantled howlers are much higher at two other well-studied sites: La Pacifica and Barro Colorado Island (BCI). We relate the low density of howlers at Santa Rosa to local historical and ecological factors. Howler populations at high and low densities differ in average group size and sex ratio. At high population densities, groups are larger and include more adult females. The number of male howlers per group appears to be more strictly limited and less variable than the number of females is. However, there is greater variation in male group membership at Santa Rosa than at La Pacifica or BCI, and at Santa Rosa there are more generating forests available into which males and females can disperse and form new groups. We present case studies describing two ways in which new howler groups are formed, and we suggest that, compared to females and compared to males at high density sites, males are relatively advantaged in the uncrowded habitats at Santa Rosa and other low density sites.     

Microhabitats and Water Relations of Epiphytic Cacti and Ferns in a Lowland Neotropical Forest1

The pattern of canopy distribution and some water relations characteristics of the epiphytic cacti Epiphyllum phyllanthus and Rhipsalis baccifera and the epiphytic ferns Polypodium crassifolium and Polypodium phyllitidis were examined in the tropical forest of Barro Colorado Island, Panama. The epiphytic cacti were 6-fold more succulent than the epiphytic ferns, which had a 9-fold higher root: shoot ratio. The four species, especially the cacti, were more abundant on the deciduous trees Ceiba pentandra, Platypodium elegans. and Tabebuia guayacan than on the evergreen Anacardium excelsum. The water-holding capacity of the bark was 2-fold higher for A. excelsum and T. guayacan than for C. pentandra and P. elegans; the main crotches of the latter species intercepted 2-fold more rainfall than those of the former. Well-watered plants of all epiphytic species showed similar total daily transpiration. After 2 weeks of drought, daily transpiration decreased an average of 48 percent for the cacti and 73 percent for the ferns. After 4 weeks of drought, daily transpiration decreased 80 percent for the cacti and was eliminated for the ferns; succulence then decreased an average of 29 percent for the cacti and 98 percent for the ferns, but all species recovered fully within 2 d after rewetting. The epiphytic ferns had a low relative capacitance (0.16 M/Pa), causing these presumably C₃ plants often to be under water stress. A high relative capacitance (0.50 M/Pa) and crassulacean acid metabolism allowed the epiphytic cacti to occur most frequently on the driest sites of this tropical forest.     

Analysis of a Nilgiri langur (Presbytis johnii) home range change

Little published information exists detailing home range changes among nonhuman primates. Resulting from human destruction of the habitat, one of the observed Nilgiri langur troops was forced to relocate its home range, during which several interesting behavioral patterns emerged. Most important was the observation that the animals were very reluctant to desert the home range, even when the last trees in the core area were being destroyed. Adult males and adult females responded differently to the destruction and resultant shift. The males appeared less nervous than the females and deserted the home range prior to them. The reaction of surrounding troops to the shift of troop A, strongly suggests territorial behavior among Nilgiri langurs. Finally, this shift, along with other observations reported elsewhere, demonstrates that Nilgiri langurs are quite adaptable and appear to possess the ability to survive in an ecology being rapidly destroyed by the human population.This study was supported by Public Health Service grant MH 11099-01 attached to Fellowship 2 F1-MH-22, 140-02 (BEH).     

Status of Trachypithecus geei in a Rubber Plantation in Western Assam, India

Golden langurs (Trachypithecus geei) are an endangered species in a limited area of Northeast India and Bhutan. They are confined to a forest belt in western Assam between the Manas River in the east, Sankosh in the west and Brahmaputra in the south along the Indo-Bhutan border. Due to habitat destruction, their populations are restricted to fragmented forest pockets, especially in India. We compared data on an isolated population of golden langurs in the rubber plantation of Nayakgaon in the Kokrajhar district of Assam, May 2002 with an earlier census in 1997. We counted a total of 52 individuals in 3 troops in 2002. The average troop size is 17.3 (r = 7–26). The ratio of adult male to adult females is 1:3.16. Of the total population 9.6% were adult males, 21.1% were adult females, 17.3% subadult males, 7.7% subadult females, 19.2% juveniles and 25% infants. In 1997 Srivastava et. al., recorded 38 individuals in 5 troops with an average troop size of only 7.6 . Apparently troop fusion has occurred. The increased population is encouraging.     

Directed seed dispersal towards areas with low conspecific tree density by a scatter‐hoarding rodent

Scatter‐hoarding animals spread out cached seeds to reduce density‐dependent theft of their food reserves. This behaviour could lead to directed dispersal into areas with lower densities of conspecific trees, where seed and seedling survival are higher, and could profoundly affect the spatial structure of plant communities. We tested this hypothesis with Central American agoutis and Astrocaryum standleyanum palm seeds on Barro Colorado Island, Panama. We radio‐tracked seeds as they were cached and re‐cached by agoutis, calculated the density of adult Astrocaryum trees surrounding each cache, and tested whether the observed number of trees around seed caches declined more than expected under random dispersal. Seedling establishment success was negatively dependent on seed density, and agoutis carried seeds towards locations with lower conspecific tree densities, thus facilitating the escape of seeds from natural enemies. This behaviour may be a widespread mechanism leading to highly effective seed dispersal by scatter‐hoarding animals.     

Ring-Tailed Lemur Home Ranges Correlate with Food Abundance and Nutritional Content at a Time of Environmental Stress

In order to determine whether ring-tailed lemurs (Lemur catta) adapt their ranging and select an optimal diet at a time of food shortage, we observed two adjacent troops in Berenty Reserve, Madagascar for over 250 h. The troops, created by a recent fission, ranged through closed canopy gallery forest next to a river and open forest away from the river. We conducted the study in September–October, 2000, normally a time of seasonally low resource availability, which was intensified by damage from a previous windstorm and recent drought. To examine the impact of environmental stress, we mapped their ranging patterns, intertroop encounters, feeding patches, siesta trees, and sleeping trees. We then correlated their ranging and feeding behavior with nutritional analyses of leaves and fruit from tamarind trees located in different parts of their ranges. One of the troops, D1A, ranged farther into open forest than previously. However, the range for troop D1B and the closed canopy portion of D1A's range were located in traditional positions for historical troops D and E. Both troops ate significantly more mature leaves from the tamarind trees in the closed canopy forest, where the leaves had significantly higher nutritional content (water and protein) than that of open forest samples. They fed on tamarind fruit significantly more often in the open forest away from the river, where it was more abundant. The lemurs selected a diet that maximized leaf water and protein and ranged where fruit was most abundant but at high energetic costs for troop D1A.     

Seasonal home range shift of red deer in a forest-agriculture area in southern Hungary

A long-term radiotelemetry study on red deerCervus elaphus Linnaeus, 1758 was carried out in a lowland forest-agriculture area in Hungary between 1993–2000. Previous observations suggested seasonal changes in population distribution between forested and agricultural habitat. Red deer concentrated in the forest during winter, but they appeared in the agricultural field during the vegetational period. We investigated the ranging behaviour, testing two alternative hypotheses: home range expansion and home range shift. Weekly radiotelemetry localisations revealed that 9 of 28 hinds showed a clear home range shift from the forest to the agricultural area for a prolonged time during the vegetational period. The remaining portion of the animals used a home range within the forest throughout the entire year. Diet composition analysis using indicator plant species showed that neither daily passages between habitats, nor home range expansion exists. These ranging behaviours were stable hence, if an animal shifted one year it shifted again in consecutive years andvice versa. Our results could be useful for the successful management of red deer populations in such complex habitats and to decrease agricultural damage.     

Genetic evidence of frequent long-distance recruitment in a vertebrate-dispersed tree

The importance of dispersal for the maintenance of biodiversity, while long-recognized, has remained unresolved. We used molecular markers to measure effective dispersal in a natural population of the vertebrate-dispersed Neotropical tree, Simarouba amara (Simaroubaceae) by comparing the distances between maternal parents and their offspring and comparing gene movement via seed and pollen in the 50 ha plot of the Barro Colorado Island forest, Central Panama. In all cases (parent-pair, mother-offspring, father-offspring, sib-sib) distances between related pairs were significantly greater than distances to nearest possible neighbours within each category. Long-distance seedling establishment was frequent: 74% of assigned seedlings established > 100 m from the maternal parent [mean = 392 +/- 234.6 m (SD), range = 9.3-1000.5 m] and pollen-mediated gene flow was comparable to that of seed [mean = 345.0 +/- 157.7 m (SD), range 57.6-739.7 m]. For S. amara we found approximately a 10-fold difference between distances estimated by inverse modelling and mean seedling recruitment distances (39 m vs. 392 m). Our findings have important implications for future studies in forest demography and regeneration, with most seedlings establishing at distances far exceeding those demonstrated by negative density-dependent effects.