Fruit eating and seed dispersal by howling monkeys (Alouatta palliata) in the tropical rain forest of Los Tuxtlas,Mexico

The frugivory and ranging habits of howling monkeys living in the rain forest of Los Tuxtlas, Veracruz, Mexico, were studied for 5 consecutive years with the aim of investigating the role of seed dispersal agents played by the howling monkeys. The howling monkeys' consumption of fruit occupied half of their feeding time, and 80% of this time was spent feeding on mature fruit. Observations confirmed use of 19 tree species and a preference for a few species of Moraceae and Lauraceae. Fruit exploitation was very seasonal; only two species provided fruit year-round. Home range size was about 60 ha, and animals in the troop (N = 16) showed a day range of 10–893 m. Monthly collection of fecal samples during 2 years indicated that 90% of the seeds (N = 7,928) in the samples belonged to eight tree species and to one liana; the rest belonged to 15 unidentified species of vines. Germination success for the seeds in the feces was about 60% and for control seeds was 35%. Howling monkeys created diverse seed shadows in the vicinity of their leaf and fruit sources, and while they dispersed the seeds of some plant species, they also produced a great deal of fruit and seed waste for others.     

Morphological traits influence prey selection by coexisting species of New World warblers (Parulidae)

New World wood warblers (Parulidae) represent one of the most dramatic adaptive radiations in North America. However, the ecological bases for the morphological differences among these species remain poorly understood, especially considering how many foraging and habitat studies the family has inspired. We hypothesized the existence of relationships between parulid morphology and diet. We combined a principal component analysis (PCA) of 18 external morphological traits of 11 species of warblers with stomach-content data from coexisting species in one breeding community in Louisiana and three wintering communities in Jamaica. The primary morphological differences, corresponding with the first three PCA axes, were body size, morphological adaptations for aerial foraging versus gleaning, and arboreal versus ground-foraging adaptations. Our analysis revealed little morphological overlap among the 11 species. Differences in diet among the warblers showed a significant relationship to the first two PCA axes of morphological traits. For five coexisting, foliage-gleaning species wintering in Jamaican wet limestone forest, larger warblers ate larger beetles and Orthopterans but not larger ants. In analyses including all four communities, species of warblers with aerial foraging morphologies consumed a greater proportion of winged insects than other warbler species. These findings document prey selection relevant to multiple subtle morphological differences among coexisting species. Overall, our results indicate that food and foraging have likely played an integral role in the morphological diversification and coexistence of species in the family Parulidae.     

Some observations on the present distribution and conservation of Alouatta and Ateles in Southern Mexico

Some information on the past and present distribution of Alouatta and Ateles in southern Mexico and on the impact of habitat destruction on their future existence is presented. Three surveys of primate populations and forest habitats were carried out between 1981 and 1983 in southeastern Mexico. Rapid destruction of the forest is reducing the number of forested areas where Alouatta and Ateles can exist and co-occur. Illegal hunting of the two primates also contributes to their rapid decline. Alouatta and Ateles live a precarious existence in a few large and small islands of forest, and efforts are needed to set aside some of these areas as reserves so that their future survival is ensured.     

Time-of-Flight Model for the Extraordinary Transmission Through Periodic Arrays of Subwavelength Apertures at THz Frequencies

A qualitative model explaining the extraordinary optical transmission of terahertz (THz) radiation through two-dimensional periodic arrays of subwavelength apertures is presented. Systematic terahertz time-domain spectroscopy studies have been undertaken to investigate the combined effects of the lattice arrangement, aperture shape, area and aspect ratio on the transmission properties of electroformed copper arrays. The extensive results presented provide a unified example of how aperture geometry dictates SPP activity. The novel fabrication method creates exemplary peak resonances, allowing the onset of surface plasmon polariton (SPP) decoupling to be distinguished from direct transmission. Furthermore, we provide the first evidence as to how the temporal properties of SPPs are governed by the single-cycle THz pulse. The time-of-flight model presented can not only be used to explain the results observed in both the presented and previously published experiments but serves as a method to engineer specific resonances for sensor applications.     

Use of leaf resources by howling monkeys (Alouatta palliata) and leaf-cutting ants (Atta cephalotes) in the tropical rain forest of Los Tuxtlas,Mexico

Use of leaf resources by a troop of howling monkeys and two colonies of leaf cutting ants was studied for an annual cycle in the rain forest of Los Tuxtlas, Mexico. Howling monkeys spent half their annual foraging time feeding on leaves; leaf-cutting ants spent at least 80% of their recorded foraging time harvesting leaves. Both herbivores preferred young leaves over nature ones, and chemical analysis showed that the protein: fibre ratio of the leaves used was correlated with these preferences. Howling monkeys used 34 tree species as leaf sources. Leaf-cutting ants used 40 plant species of which 38 were trees. Eighteen species used by Alouatta were also used by Atta; species of Moraceae and Lauraceae were among the most important in their foraging preferences. The plant species used by monkeys and ants occurred at low densities (? 4.0 ind/ha). The seasonal production of leaves, the high density of leaf-cutting ant colonies at the study site, and the high amounts of young foliage harvested by the ants from tree species, and individual trees used by howling monkeys as sources of young leaves suggest that the foraging activities of Atta may represent a significant pressure upon leaf resources available to Alouatta.     

Comparison of frugivory by howling monkeys (Alouatta palliata) and bats (Artibeus jamaicensis) in the tropical rain forest of Los Tuxtlas,Mexico

Information on the fruit diets of howling monkeys and fruit-eating bats in the tropical rain forest of Los Tuxtlas, Mexico was collected for a year to compare the plant species used. Howling monkeys used 19 plant species whereas bats used 32 plant species as fruit sources. Eleven species were common in the diet of both mammals. A rank analysis at the plant species level showed that the fruit diets of Alouatta and Artibeus were very different. In contrast to bats, howling monkeys displayed a seasonal pattern in fruit consumption. Diet overlap between the two mammals was highest during the monkeys' fruit-eating season. Measures of fruit production in eight trees (four species) indicated marked variations in fruit biomass produced and in length of fruiting from tree to tree and species to species. Peaks in fruit production were typical both at the species and the individual tree levels, demonstrating the very patchy nature of the fruit available to the monkeys and the bats.