Posteado por: BPP | julio 11, 2007

Use Of Habitat, Behavioral Activity And Intraspecific Relationships Of White-Faced Capuchins

Use Of Habitat, Behavioral Activity And Intraspecific

Relationships Of White-Faced Capuchins

J. CAPECE, Department of Fisheries and Wildlife Management, University of Massachusetts, USA.
A. RODRIGUEZ, Programa Regional en Manejo de Vida y Silvestre, Universidad Nacional, Costa Rica, Central America.
M. SELBY, Department of Fisheries and Wildlife Management, University of Massachusetts, USA.

I. INTRODUCTION

The behavior and intraspecific relationships of White-faced capuchins (Cebus capucinus) and how these activities relate to habitat use and features of the habitat are examined in this study. There have been many studies conducted on patterns of habitat use, foraging strategy and other intraspecific relationships of White-faced Capuchins, (Chapman, 1988; Merriam, 1991; Morera, 1996). Chapman (1988) and Merriam (1991) reported that the monkeys spend 21.3% and 28.9%, respectively, of total time in foraging activity. Morera (1996) found that 51.8% of total time was spent in searching for food and a total of 31.5% in feeding activities. The same study also reported that capuchins mainly use secondary forest in Santa Rosa National Park, however, the author fails to recognize any possible causes of the significantly high rate of use of this habitat type. The majority of this literature also fails to clearly report the relation of these activities to habitat type and location within the habitat. This study differs from others in that it compares the observed behavior within three different sites. It is interesting, especially in the study of primate species, to examine any possible correlation between the type of behavior exhibited and the location of the environment in which this takes place, within all three study sites. Determining how the capuchins are using their environment is very important in the management of both the species and the forest. A better understanding of exactly how and where the White-faced capuchins are using their time is necessary. With an increasing amount of land being reforested for wildlife protection, studies such as this will play an important role in ensuring that this species will be provided with adequate habitat.

II. OBJECTIVES

General objectives

The goals of this study are to determine and examine the patterns of frequency observed in focal individuals of White-faced Capuchins for various behavioral activities. The frequency of these activities will be related to the habitat types in the three distinct regions (macrohabitat), and also within the location, or level, of each habitat (microhabitat).

Specific objectives

1. To determine type of habitat for every troop observed.
2. To determine features of the habitat used by White-faced Capuchins including make-up of the ground, density and type of underbrush, and average height of large trees.
3. To determine the strata level used by capuchins and their relationship to behavioral activities.
4. To determine the frequency of different types of behavioral activity exhibited by a focal individual in a five-minute observation period.
5. To determine differences in behavior exhibited between different age classes and sex.
6. To determine if there are differences in behavior in the morning (before 12pm), and afternoon (after 12pm).

III. HYPOTHESIS

We expect to find the use of a different habitat type and a correlation between the use of the habitat and the difference in behavior exhibited by individuals. The type of behavior exhibited is expected to differ between individuals of varying age classes and within different levels of the habitat within the three study sites.

IV. METHODS

Study sites

Santa Rosa National Park, located in the Guanacaste Province, in northwestern Costa Rica, covers approximately 10, 800 ha. Established in 1970, it lies between the Pan-American Highway and the Pacific Ocean. The park consists of stepped plateaus, which begin at an elevation of approximately 300-m and gradually drop down to a coastal plain. The region is comprised of dry tropical forest, semievergreen forest and reclaimed pasture in varying stages of secondary succession. Santa Rosa National Park contains the first two study sites, Naranjo and Santa Rosa.
The Guanacaste National Park contains the third study site, Maritza. It lies adjacent to the Pan-American Highway in northwestern Costa Rica. This park represents some 80,000 ha of tropical dry forest in various stages of regeneration. The region is comprised of volcanoes and volcanic foothills with a variety of different habitat types.

Naranjo

Located in Santa Rosa National Park, Naranjo is a coastal plain that consists mainly of beachfront, mangrove swamp and floodplain. During the dry season many of the non-riparian tree species lose their leaves. The site consists of many distinct habitat types including riparian, semi-deciduous, deciduous and evergreen forest. In some areas, the forest is transitional from mangrove swamp to another forest type. The streambeds are dry during the dry season, however there are waterholes available for utilization.

Santa Rosa

Located in Santa Rosa National Park, Santa Rosa consists of dry deciduous forest, evergreen to semievergreen forest and abandoned pasture. This mosaic of habitat types results from a long history of diverse land use. Over the past 300 years, extensive clearing of land for cattle and the logging of remaining forest have taken place. The site has recently been reverted from farmland resulting in a large amount of secondary growth. As in Naranjo, the dry season causes many of the non-riparian tree species to lose their leaves. The streambeds are dry during the dry season and there are few waterholes available for utilization. The park contains at least one, small artificial waterhole.

Maritza

Located in Guanacaste National Park, this region is dominated by primary cloud forest in areas of high elevation, secondary growth forest in mid-elevation and dry grassland of volcanic origin in low elevations. The cloud forest experiences a decrease in temperature, an increase in moisture and an increase in the strength of the prevailing wind. Primarily made up of evergreen forest, the canopy and lower canopy are very dense. There are flowing streams present that contain many deep pools. In the regions of mid-elevation, the secondary forest is also evergreen. Unlike the primary growth, however, the density of the lower and upper canopy and vegetation is significantly less. In the low elevations, the grasslands are extremely dry and there are few trees scattered throughout the area. The winds are strong and few trees grow there. The grasslands are scattered with volcanic rock, varying in size.

Study Design

Observations. Capuchin troops were located within the area of study. The troops showed variable tolerance of observers depending on the study site. In some sites, the monkeys habituated rapidly to the presence of the observers and in others they maintained a distance or fled the general area of the observers. Two observers each chose a focal individual to observe for a five-minute period. A third person was responsible for the timing of the observation period. Observations were recorded on the behavior and strata level of the focal individual at the start of the five-minute period and at each one-minute interval (punctual observations) within the five minutes. Because capuchins are a highly mobile species, the observers recorded when their focal individual went out of sight rather than chasing the individual and potentially affecting the behavior of the troop. However, efforts were made to keep the focal individual in sight for the full five-minute observation period.

Data collection. The data sheets used by the observers listed four main categories.
1. Type of habitat
2. Level of habitat

a. ground
b. shrubs
c. understory
d. canopy

1. Behavior

a. foraging
b. social cooperation
c. locomotion
d. vocalization
e. resting
f. aggression
g. out of sight
h. other

4. Age/sex

a. lone adult
b. juvenile
c. female with baby

At each new observation sight, the temperature, weather and time of day was recorded.

Density Measurements. Measures of the habitat and density of vegetation were recorded at each area where a troop was observed. The observers randomly chose two areas within the location of the troop by having a blindfolded observer throw an object. The measurements were taken in the location of where the object landed. Two areas were used in each observation site in order to more accurately describe and generalize the habitat in which the capuchins were located. The two measurements were also combined to gain average measurements for the area. These measurements are important to the study because they allow us to correlate habitat use with observed behavior. The three areas of the habitat measured include:

1. description of understory density
2. density of the canopy
3. height of the nearest tree neighbor

Understory

The observers used two methods to estimate the density of the understory. The first method involved counting the amount of times that vegetation touched points on a meter stick held in the air. The observers felt that this method, although useful, did not accurately describe the true density of the understory. Therefore, a second method was incorporated with the first in order to ensure accuracy. This method simply involved rating the density of the understory on a scale, with 1 being least dense to 4 being most dense.

The criteria the observers used to rate understory density are:

1. The site is near a dry streambed or stream. Little or no vegetation present, including, but not limited to, vines, shrubs, small trees and other woody plants.
2. The site has little or no small trees or other woody plants present but has a large amount of small shrubs and vines. The observers are able to easily walk through the vegetation.
3. The site has a large amount of vines, shrubs, small trees and other woody plants. The observers are not able to walk without effort through the vegetation.
4. Vegetation fills the area between the canopy and ground. Locomotion and sight through the vegetation is difficult for the observers.
Canopy
The density of the canopy was estimated by using a densiometer with four transects. The amount of vegetation within the transects was recorded in percent with each transect representing 25%.

Height of nearest tree neighbor

The height of the nearest tree neighbor was determined using a clinometer. The observers measured the nearest tree, (not including small woody plants), to the randomly chosen point at which the other density measures were taken. The height of the tree is given in meters.
Data Analysis. (Table 2) After collecting data, the type of habitat, habitat use, behavior and age class or sex and taking measures of the habitat density in each site, an analysis of the data is needed. The data was analyzed using the Kruskall-Wallis Test (non-parametric ANOVA) to determine differences in punctual frequencies of behavior related to the following variables:
* Age/sex
* Locality
* Time
* Habitat type
* Behavior categories

A posteriori test of Kruskall-Wallis was also conducted in order to determine differences between levels of the behavior variables.
Spearman rank correlations were conducted to compare frequency of punctual behavior in respect to the other variables and to determine the grade of association between them.
To determine dependence between strata level use and locality a Contingency table (RxC) was constructed using G test statistics. The same procedure was applied to the behavior categories versus upper and lower canopy frequency of use.

V. RESULTS

Troop observations

Naranjo.
We observed the total of four troops in Naranjo. Three of the troops each contained approximately 20 individuals and the fourth troop contained approximately 10 individuals. We observed a total of 58 focal individuals. Of the 58 observed there were 37 lone adults, 3 females with newborn and 18 juveniles. There were a total of 278 punctual observations made.

Santa Rosa.
We studied two troops in Santa Rosa. One troop contained approximately 20 individuals and the second troop contained only 8 individuals. We observed a total of 24 focal individuals. Of the 24 observed there were 20 lone adults, 1 female with newborn and 3 juveniles. There were a total of 119 focal observations made.

Maritza.
There were 19 individuals observed in Maritza. Of the 19 individuals, 18 were lone adults and 1 was a juvenile. There were a total of 87 focal observations made.

A Kruskall Wallis Test showed no differences in the frequency of punctual behavior in relation to locality, (Naranjo, Santa Rosa, Maritza).

Type of habitat used

Naranjo. The troops in Naranjo utilized many types of forest: deciduous, evergreen and riparian and secondary evergreen forest. Troops were also observed using transitional mangrove and secondary forest.

Santa Rosa. The troops in Santa Rosa were observed utilizing secondary, evergreen and deciduous forest.
Maritza. The troops in Maritza were observed utilizing only primary evergreen forest.

The Kruskall Wallis Test showed no differences in the frequency of punctual behavior in relation to the habitat types in any of the three sites, (Naranjo, Santa Rosa, Maritza).

Time

The Kruskall Wallis Test concluded that there were no differences in the frequency of punctual behavior related to time. Observations that were conducted in the morning and in the afternoon showed no difference in the type of behavior exhibited or habitat used by the monkeys.

Age/sex

The Kruskall Wallis Test showed that there were no differences in the frequency of punctual behavior when related to age/sex, (lone adult, juvenile and female with a baby on her back).

Behavior

There are significant differences that exist in the categories of behavior that we observed (KW=257.2; P <0.0009). The differences are evident in the categories of foraging, locomotion and resting with respect to aggression, social cooperation and vocalization. There are no differences in the three behaviors that are most common.

Use of Canopy related to Behavior Categories

The behavior categories show dependence to strata level used by White-faced capuchins (G=11.13; gl=5; P<0.05). The major difference in the behavior observed is in the upper canopy, followed by the lower canopy. In the shrubs and ground, the frequency of behavior was scarce due to a small sample size.

Strata Level Use vs. Locality

Our data showed a dependent relationship of strata level use and locality (G=27.3; gl=6;P<0.001). This concludes that the frequency of punctual behavior is related to the strata level and the locality, or study site. We observed that the upper strata are most often utilized, followed by the lower strata. The shrubs and ground are utilized significantly less.

VI. DISCUSSION

The results of our research show that capuchins are very plastic in their use of the habitat, or are able to use many different habitat types. This is consistent with reports from other literature on White-faced Capuchins. The monkeys were observed using mainly evergreen, deciduous and semi-deciduous forest types. The use of these habitat types may be due in part to the low food resource availability during the dry season where the majority of the trees lose their leaves and lack fruit. In Maritza, there was a high use of primary forest related to the abundance of fruit utilized by the monkeys. In the neighboring secondary forest that contained no fruit, no monkeys were observed in this habitat.

In Santa Rosa, the habitat that the monkeys most frequently used was deciduous forest. This use may be due in part to the use of the canopy as a connection, or bridge, to other neighboring forest types such as semi-deciduous and riparian. The monkeys showed very rapid locomotion through the canopy that may also suggest that this bridge exists and is highly utilized by the monkeys.

There are other important variables that may suggest why the monkeys are utilizing a particular habitat. These include areas with numerous large vines and gaps in the evergreen forest. The monkeys were observed numerous times partaking in activities of play both in areas with vines and space on the ground for locomotion. This seemed especially common within younger individuals. There were many observations made in areas where a road or streambed intersected the forest. The monkeys were observed utilizing the shrubs and ground for mostly locomotion and interaction in these areas.

We expected to find a correlation between the time of day and foraging behavior exhibited by the monkeys. Our results, however, showed no differences in foraging behavior between the morning and afternoon observations. In some locations, this can be contributed to having only recorded observations from one part of the day and therefore having no comparison. In other locations, such as Maritza, the monkeys were more difficult to locate and not habituated to the presence of humans. Therefore, it is possible that they were exhibiting other acts of behavior, such as aggression, instead of foraging.

In the conduction of this study there were certain aspects that we would change to better a future study. Although we feel that our observations are accurate, they were not easily made. It is necessary to gain information at the onset of the study on the location of capuchin troops in each of the sites. This would be of great benefit in reducing the amount of search time for the troops, adding to the amount of observation time available and ultimately increasing sample size. In Santa Rosa and Maritza, our sample size is slightly less than in Naranjo. This is due to the increased difficulty in locating the troops.

Due to the large study sites and the rapid locomotion of the monkeys, it would also be beneficial to have more teams of observers using hand-held radios. This would make it possible to cover large areas and notify other teams of the monkey’s whereabouts.

The results of this study show implications for the management of both White-faced capuchins and the forest habitats in which they live. The results imply that, because capuchins use a wide variety of habitat types, it is important to manage the forest in such a way as to provide all necessary habitat types for this species. It is vital to the well being of the capuchins to consider all habitat types when proposing management plans for the forest.

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