Degree Of Frugivory Research Articles

Can Functional Traits Predict Ecological Interactions? A Case Study Using Rain forest Frugivores and Plants in Australia

ABSTRACTIn rain forest, the large numbers of species of fleshy‐fruited plants and frugivorous animals result in a large number of potential fruit–frugivore interactions, which are challenging to survey in the field. Yet, knowledge of these relationships is needed to predict consequences of changes in the frugivore assemblage for seed dispersal. In the absence of comprehensive dietary information, it may be possible to delineate between frugivores that disperse different plants using ‘functional traits,’ or morphological and behavioral attributes of frugivores that interact with differences in salient characteristics of plant species. Here we use data on the consumption of 244 Australian rain forest plant species by 38 bird species to test for associations between patterns of frugivory and birds': (1) degree of frugivory, (2) gape width, and (3) seed treatment (seed crushing or seed dispersing). Degree of frugivory and gape width explain 74 percent of the variation in the sizes of fruits consumed by frugivorous birds. Among birds that consume a substantial dietary proportion of fruit, birds with wider gapes consume larger fruits. In contrast, this relationship was not shown by birds for which fruit is only a minor dietary component. Degree of frugivory and gape width, together with seed treatment, also strongly predict the overall taxonomic composition and diversity of plants consumed by bird species. Functional classifications of frugivore species may prove useful in developing a predictive understanding of fruit–frugivore interactions in other rain forest regions where detailed dietary information is not available for most frugivores.

Frugivory and habitat use by thrushes (Turdus spp.) in a suburban area in south Brazil

Thrushes (Turdus spp., Turdidae) are among the most common frugivorous birds in urban areas around the world, where they disperse the seeds of a variety of plant species. We studied the abundance, habitat use, foraging behavior and diet of four thrush species (Turdus rufiventris, T. amaurochalinus, T. leucomelas, and T. albicollis) in a suburban area in south Brazil. Abundance, habitat use and foraging behavior were based on birds surveyed along a 3,240 m transect crossing open (formed by lawns, streets, and buildings) and forested areas. Diet was based on fecal samples collected from mist-netted birds. Turdus rufiventris was the most abundant species, followed by T. amaurochalinus, T. leucomelas, and T. albicollis. All species used forest fragments more frequently than expected by chance. A total of 91.8% (n = 147) of the fecal samples contained fruit remains, while 42.2% contained only animal matter. Most of the foraging records were on the ground, where birds got mainly invertebrates. Fruits and invertebrates were eaten more frequently in open than in forested areas. A total of 25 seed morfospecies were found in the droppings, including five exotic plant species. Thrushes overlapped widely in the fruit composition of their diets. The high abundance and degree of frugivory, coupled with the frequent use of forest patches, indicate that thrushes are among the great bird contributors to the seed dispersal occurring in urban forest patches, potentially influencing the vegetation dynamics of such habitats so important for the maintenance of the biodiversity in urban areas.

How much is a lot? Seed dispersal by white-faced capuchins and implications for disperser-based studies of seed dispersal systems

The quantity of seeds dispersed is considered one of several means to determine the dispersal effectiveness of an animal. However, there is little consistency in the manner in which quantities are measured or presented. Here, we quantify seed dispersal by white-faced capuchin monkeys (Cebus capucinus) in Santa Rosa National Park, Costa Rica by measuring: degree of frugivory, number of plant species consumed, the number of seeds consumed per unit time, the number of seeds dispersed intact per unit time, and the number of seeds dispersed intact per unit space. Forty-nine percent of C. capucinus diet is composed of the fruit of 39 species, 4 of which constitute 82% of the frugivory. Seventy-four percent of consumed fruits contain seeds that pass intact through the capuchin digestive system. Capuchins pass a mean of 15.7 seeds of a mean of 1.3 species per defecation, and defecate 25.4 times per 12-h day. These numbers are compared with extant data for C. capucinus, and possible reasons for discrepancies among results between studies are discussed. We propose a standardization of quantitative measures of seed dispersal so that quantifications of seed dispersal can be compared within species, and eventually across species.

Effects of Vegetation Traits on Habitat Preferences of Frugivorous Birds in Atlantic Rain Forest

ABSTRACTStructural and floristic components of vegetation and fruit production were examined to evaluate the relative importance of each vegetation aspect on patterns of habitat use and to determine whether differences in degree of frugivory would affect sensitivity of birds to vegetation components. Abundances of 12 bird species were quantified in four different habitat types in the Southeastern Atlantic rain forest of Brazil using captures with mist nets. Structural and floristic traits and fruit production were sampled within plots along the mist net lines. Best explanations for the variation in species abundance were obtained by different combinations of the vegetation components (generalized linear models, Akaike information criterion; R2 mean values = 0.48, Δ AICc= 0). Although each species had a particular preference for some vegetation variables, floristic components stood out in those relationships, generating models with a stronger explanatory capacity (R2 > 0.40) and higher levels of empirical support (Δ AICc= minimum values). The variation in bird sensitivities to the floristic component was associated with bird dependence on a fruit diet: there was a correlation between the explanatory capacity of models built with only floristic composition and a species' degree of frugivory (Spearman rank correlation, r= 0.66, P= 0.04), indicating that floristics had a higher effect in more frugivorous birds. For the other vegetation components, there was no clear pattern with statistical support. These results indicate that sensitivities of bird species to vegetation aspects are associated with their dependence on a fruit diet.

DIFFERENTIAL RESOURCE USE BY PRIMATES AND HORNBILLS: IMPLICATIONS FOR SEED DISPERSAL

Arboreal frugivores, such as primates and hornbills, are important seed dis- persers for many tropical plant species, yet the degree to which they use the same resources is unknown. If primates and hornbills consume the same fruit species, they may be redundant in their roles as seed dispersers, and the loss of one of these taxa may be compensated for by the other. To examine resource use by tropical frugivores, we quantified the feeding habits of two hornbill species, Ceratogymna atrata and C. cylindricus, and five primate species, Colobus guereza, Lophocebus albigena, Cercopithecus pogonias, C. cephus, and C. nictitans, in the lowland rainforest of south-central Cameroon. Based on over 2200 feeding observations recorded between January and December 1998, we characterized the diets and estimated dietary overlap among frugivore species. Previous studies have cal- culated dietary overlap by counting the number of diet species that two animals share, often leading to inflated estimates of overlap. Our method incorporated the proportional use of diet species and fruit availability into randomization procedures, allowing a clearer as- sessment of the actual degree of overlap. This added complexity of analysis revealed that, although the diets of a hornbill and a primate species may have as many as 36 plant species in common, actual dietary overlap is low. These results suggested that there are distinct hornbill and primate feeding assemblages, with primates consuming a greater diversity of plant species and higher levels of nonfruit items like leaves and seeds. Using Correspon- dence Analysis, we also identified two primate assemblages, separated largely by degree of frugivory and folivory. In addition, we found that hornbills feed at significantly higher strata in the forest canopy and eat fruits of different colors than primates. Averaged across the year, overlap between groups (hornbill-primate) was significantly lower than combined within-group overlap (primate-primate and hornbill-hornbill), showing that primates and hornbills have dissimilar diets and are not redundant as seed dispersers. In equatorial Africa, primate populations face greater declines than hornbill populations because of hunting. It is unlikely that seed dispersal by hornbills will compensate for the loss of primates in maintaining forest structure.

Differential Resource Use by Primates and Hornbills: Implications for Seed Dispersal

Arboreal frugivores, such as primates and hornbills, are important seed dispersers for many tropical plant species, yet the degree to which they use the same resources is unknown. If primates and hornbills consume the same fruit species, they may be redundant in their roles as seed dispersers, and the loss of one of these taxa may be compensated for by the other. To examine resource use by tropical frugivores, we quantified the feeding habits of two hornbill species, Ceratogymna atrata and C. cylindricus, and five primate species, Colobus guereza, Lophocebus albigena, Cercopithecus pogonias, C. cephus, and C. nictitans, in the lowland rainforest of south-central Cameroon. Based on over 2200 feeding observations recorded between January and December 1998, we characterized the diets and estimated dietary overlap among frugivore species. Previous studies have calculated dietary overlap by counting the number of diet species that two animals share, often leading to inflated estimates of overlap. Our method incorporated the proportional use of diet species and fruit availability into randomization procedures, allowing a clearer assessment of the actual degree of overlap. This added complexity of analysis revealed that, although the diets of a hornbill and a primate species may have as many as 36 plant species in common, actual dietary overlap is low. These results suggested that there are distinct hornbill and primate feeding assemblages, with primates consuming a greater diversity of plant species and higher levels of nonfruit items like leaves and seeds. Using Correspondence Analysis, we also identified two primate assemblages, separated largely by degree of frugivory and folivory. In addition, we found that hornbills feed at significantly higher strata in the forest canopy and eat fruits of different colors than primates. Averaged across the year, overlap between groups (hornbill–primate) was significantly lower than combined within-group overlap (primate–primate and hornbill–hornbill), showing that primates and hornbills have dissimilar diets and are not redundant as seed dispersers. In equatorial Africa, primate populations face greater declines than hornbill populations because of hunting. It is unlikely that seed dispersal by hornbills will compensate for the loss of primates in maintaining forest structure.

Frugivory and seed dispersal by vertebrates in the Oriental (Indomalayan) Region.

Current knowledge of frugivory and seed dispersal by vertebrates in the Oriental Region is summarized. Some degree of frugivory has been reported for many fish and reptile species, almost half the genera of non-marine mammals and more than 40% of bird genera in the region. Highly frugivorous species, for which fruit dominates the diet for at least part of the year, occur in at least two families of reptiles, 12 families of mammals and 17 families of birds. Predation on seeds in fleshy fruits is much less widespread taxonomically: the major seed predators are colobine monkeys and rodents among the mammals, and parrots, some pigeons, and finches among the birds. Most seeds in the Oriental Region, except near its northern margins, are dispersed by vertebrate families which are endemic to the region or to the Old World. Small fruits and large, soft fruits with many small seeds are consumed by a wide range of potential seed dispersal agents, including species which thrive in small forest fragments and degraded landscapes. Larger, bigger-seeded fruits are consumed by progressively fewer dispersers, and the largest depend on a few species of mammals and birds which are highly vulnerable to hunting, fragmentation and habitat loss.

Frugivory and seed dispersal by vertebrates in the Oriental (Indomalayan) Region

ABSTRACTCurrent knowledge of frugivory and seed dispersal by vertebrates in the Oriental Region is summarized. Some degree of frugivory has been reported for many fish and reptile species, almost half the genera of non‐marine mammals and more than 40% of bird genera in the region. Highly frugivorous species, for which fruit dominates the diet for at least part of the year, occur in at least two families of reptiles, 12 families of mammals and 17 families of birds. Predation on seeds in fleshy fruits is much less widespread taxonomically: the major seed predators are colobine monkeys and rodents among the mammals, and parrots, some pigeons, and finches among the birds. Most seeds in the Oriental Region, except near its northern margins, are dispersed by vertebrate families which are endemic to the region or to the Old World. Small fruits and large, soft fruits with many small seeds are consumed by a wide range of potential seed dispersal agents, including species which thrive in small forest fragments and degraded landscapes. Larger, bigger‐seeded fruits are consumed by progressively fewer dispersers, and the largest depend on a few species of mammals and birds which are highly vulnerable to hunting, fragmentation and habitat loss.

The primate community of the Lopé Reserve, Gabon: diets, responses to fruit scarcity, and effects on biomass.

The diets of all diurnal primates (Gorilla g. gorilla, Pan t. troglodytes, Mandrillus sphinx, Colobus satanas, Cercocebus albigena, Cercopithecus nictitans, C. pogonias, C. cephus) in the Lópe Reserve, central Gabon, are described from qualitative and quantitative data collected over 10 years. A total of 397 foods were recorded, of which 91% were from plants. The diet of seven of the eight species were numerically dominated by fruit, the exception being Colobus satanas with a diet dominated by seeds. When proportion of feeding time was examined, fruit remained the dominant food class for six species, while Cercocebus albigena, like the black colobus, spent most time feeding on seeds. The number of foods recorded per species ranged from 46-220, but dietary breadth of the four species that have not been subjects of detailed study was certainly underestimated. Almost half of the foods (46%) were eaten by only one species, and only four (1%) were recorded for all eight species. At Lópe, fruit is scarce for 2-3 months during the annual dry season, and fruit crop failures can prolong this period of scarcity to as many as 8 months in some years. When fruit is scarce, the diets of all the species changed to include more nonfruit foods, but chimpanzees and the three species of guenons maintained a fruit dominated diet. The total biomass of the Lópe primate community is 374 kg/km2, which is low compared to other sites in tropical Africa. Within the Lópe community, biomass correlates negativity with degree of frugivory, suggesting that fruit availability may be critical, but this does not explain the low total biomass compared to other sites. Neither floristic diversity nor the composition of the primate community at Lópe can account for the biomass. While historical events such as climate-induced changes in forrest cover, disease, or impact of human activities cannot be ruled out, we conclude that the most likely explanation of low primate biomass is the occurrence of an ecological "catastrophe" in the fairly recent past from which populations have not yet recovered. We believe that the most likely scenario was climate-mediated disturbance of flowering of important fruit food species. Prolonged fruit scarcity would have caused mortalities and affected the most frugivorous species more severely.

Relationship of incisor size to diet and anterior tooth use in sympatric sumatran anthropoids.

Researchers often relate anthropoid incisor size to diet and ingestive behaviors. It is suggested that primates that frequently consume large, tough foods (i.e., fruits) require large incisors to process these items. This idea has been difficult to test because of a lack of data on anterior tooth use in wild primates, and a lack of understanding concerning the relationships between food properties and ingestive behaviors. The first field study of primate ingestive behaviors has recently been completed for four species of Sumatran anthropoids: Hylobates lar, Macaca fascicularis, Pongo pygmaeus, and Presbytis thomasi [Ungar, American Journal of Physical Anthropology 95:197-219, 1994; International Journal of Primatology 16:221-245, 1995]. This paper documents both relative and absolute incisor row width differences among these taxa, and evaluates the relationships between incisor size and feeding behaviors for specific taxa. Results indicate that differences in incisor size among these species cannot all be explained by degree of frugivory, food item size, or even degree of incisor use in ingestion alone. It is therefore suggested that inferences of dietary differences based on largely or solely on differences in incisor sizes of specific fossil anthropoid taxa should be approached with caution. © 1996 Wiley-Liss, Inc.

The Diets of Neotropical Trogons, Motmots, Barbets and Toucans

Although membership in broad diet categories is a standard feature of community analyses of Neotropical birds, the bases for assignments to diet categories are usually not stated, or they are derived from anecdotal information or bill shape. We used notations of stomach contents on museum specimen labels to assess membership in broad diet categories (“fruit only,” “ arthropods only,” and “fruit and arthropods”) for species of four families of birds in the Neotropics usually considered to have a mixed diet of fruit and animal matter: trogons (Trogonidae), motmots (Momotidae), New World barbets (Capitonidae), and toucans (Ramphastidae). An assessment of the accuracy of label data by direct comparison to independent microscopic analysis of actual stomach contents of the same specimens showed that label notations were remarkably accurate. The specimen label data for 246 individuals of 17 species of Trogonidae showed that quetzals (Pharomachrus) differ significantly from other trogons (Trogon) in being more fiugivorous. Significant differences in degree of frugivory were found among various Trogon species. Within the Trogonidae, degree of frugivory is strongly correlated with body size, the larger species being more frugivorous. The more frugivorous quetzals (Pharomachrus) have relatively flatter bills than other trogons, in accordance with predictions concerning morphology of frugivores; otherwise, bill morphology correlated poorly with degree of fiugivory. An analysis of label data from 124 individuals of six species of motmots showed that one species (Electron platyrhynchum) is highly insectivorous, differing significantly from two others that are more frugivorous (Baryphthengus martii and Momotus momota). An analysis of 135 individuals of 12 species of barbets showed that although “fruit only” predominated among almost all species, arthropods are more frequently recorded in the stomachs of species in the genera Eubucco and Capito than in Semnornis. The highly frugivorous diet of Semnornis species is yet another parameter in which they resemble toucans more than New World barbets. Data from 326 individuals of 32 species of toucans showed that the family is remarkably homogeneous in the predominance of fruit in the stomachs of all species. These data suggest hat the degree to which toucans prey upon bird eggs and nestlings, and animal matter in general, is overemphasized. Although our data suggest that it is safe to assign toucans to a “fruit only” category in community analyses, such assignments must be taken on a genus-by-genus or species-byspecies basis in trogons, motmots, and barbets.

Frugivory in Some Migrant Tropical Forest Wood Warblers

Frugivory in Some Migrant Tropical Forest Wood Warblers