Mixed-species Assemblages Research Articles

Foraging Decisions During Nectar Feeding by Tamarin Monkeys (Saguinus mystax and Saguinus fuscicollis, Callitrichidae, Primates) in Amazonian Peru

A 12-month field investigation was conducted on the diet and foraging activities of moustached (Saguinus mystax) and saddleback (Saguinusfuscicollis) tamarin monkeys in the Amazon Basin of northeastern Peru. Throughout most of the year insects, fruits, and plant exudates are the primary components of the tamarin diet. However, during the dry season months of July and August, from Symphonia globulifera (Guttiferae) accounted for 22-31 percent of tamarin feeding time. These primates are highly destructive in their nectar-feeding activities: a single adult tamarin may destroy 6-14 Symphonia flowers per feeding minute. Foraging activities associated with feeding are reminiscent of traplining behavior and characterized by goal-directed travel to particular feeding trees. S. mystax and S. fuscicollis appear to be aware of the distribution and location of flowering Symphonia trees in their home range and select sites largely on the basis of proximity. In 86 percent of all cases, the tree nearest the previous feeding tree was also visited. The mean distance between these feeding sites was 107 m. Expectations regarding the amount and variance of the food reward were also important factors in tamarin foraging decisions. It is argued that by minimizing random foraging movements and bypassing trees with limited food rewards, these small-bodied primates are able to exploit widely scattered but predictable resources. FIELD DATA COLLECTED over the past 20 years indicate that is an important seasonal component in the diet of a number of strepsirhine primates (Petter 1962, Coe & Isaac 1965, Sussman & Tattersall 1976, Hladik 1979, Hladik et atl. 1980). Despite the fact that these primates often destroy flowers in the process of procuring nectar, Sussman and Raven (1978) have suggested that, in areas of Africa and Madagascar depauperate in plant-visiting bats, small-bodied nocturnal prosimians may play a significant role in the pollination of certain plant species . . . , and that such ecological relationships may have existed since the Eocene. The evidence for nectar-feeding by diurnal primates is less clear. This may result from the fact that the quantity of produced by flowering plants that attract diurnal feeders (e.g., hummingbirds) is generally far below that available in bator hawkmoth-adapted species (Cruden et al. 1983, Opler 1983). For example, Opler (1983) reports that in a dry tropical Costa Rican forest the mean maximum amount of available in bat-pollinated flowers (1310 Al) is approximately 75 times greater than the quantity present in hummingbird-pollinated flowers (17 ,ul). Although in certain species may be produced continuously or after the activity period of the primary pollinator (Cruden et al. 1983), Rourke and Wiens (1977) suggest that, in general, nectar secretion is synchronized temporally for visitation by the established pollinators coadapted to that particular flower. Thus, for many species of larger-bodied primates, the availability and production of diurnal is limited and probably below some minimum value needed to stimulate habitual nectar-feeding behavior. Following are described extensive observations of feeding by two species of small-bodied diurnal primates, S. mystax (moustached tamarin, mean adult body weight 594 gm) and S. fuscicollis (saddle-back tamarin, mean adult body weight 412 gm; Garber and Teaford, 1986). This research was part of a 12-month field investigation of the feeding ecology of mixed-species troops of tamarins at the Rio Blanco Research Station in the Amazon Basin of northeastern Peru (72?10'W, 4?05'S). In this region of the Amazon, moustached and saddleback tamarins form stable, mixed-species assemblages in which individuals of each species travel, forage, and cooperatively defend a common home range and set of resources. Eleven S. mystax and eight S. fuscicol/is constituted the main study troop. Throughout most of the year, insects, ripe fruits, and plant exudates were the major components of the tamarin diet. However, during the dry season months of July and August, from S. globulifera (Guttiferae) accounted for 22-31 percent of tamarin feeding time. The intensity of these feeding bouts and the manner in which Saguinus ranged to encounter flowering Symphonia trees suggest that is an important seasonal part of the diet of moustached and saddle-back tamarins.

Diet, Foraging Patterns, and Resource Defense in a Mixed Species Troop of Saguinus Mystax and Saguinus Fuscicollis in Amazonian Peru

AbstractIn the Amazon Basin of northeastern Peru, moustached (Saguinus mystax) and saddle-back (S. fuscicollis) tamarins form stable mixed species assemblages in which groups of each species feed, forage, rest, travel and cooperatively defend a territory throughout the entire year. Data presented indicate that despite extreme overlap in feeding and ranging behavior, a change in troop size did not have a significant affect on dietary preferences, activity budgets, day range, foraging effort, and the number and length of daily feeding bouts of either resident species. The larger troop, however, was more successful at defending major feeding trees than the smaller troop. Unsuccessful resource defense resulted in a decrease in time spent feeding and foraging, and an increase in the distance traveled to the next major feeding site. It is proposed that within-troop feeding competition is generally not a critical factor in the feeding ecology of this mixed species tamarin troop. Rather, the formation of such a troop enables each resident species to more effectively exploit and defend a set of productive feeding trees.

Rare earth elements in foraminifera tests

The concentrations of nine rare earth elements (REE) La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb, have been determined in mixed species assemblages of foraminifera tests taken from Atlantic Ocean sediment core tops. Reductive cleaning techniques have revealed that REE are present in three phases in foraminifera tests collected from sea floor sediments; REE included in the foraminiferal calcite matrix (termed lattice REE), REE associated with an authigenic FeMn-rich phase adsorbed onto the surface of the test following the death of the organism (termed coating REE) and REE associated with alumino-silicate detritus (termed detrital REE) which commonly infills the test chambers after burial in the sediment. The concentrations of REE in the nondetrital (lattice plus coating) and lattice phases have been measured in this study. Approximately 90% of the REE measured in the non-detrital phase reside in the coating phase, the remainder being present in the lattice phase. These data have been used to investigate the relationship between the distribution of dissolved REE in the ocean and in the coating and lattice phases. In addition to the REE the concentrations of Mn, Fe, Cu, Al and PO 4 have been measured as an aid to characterisation of the various phases.

Uptake of polychlorinated biphenyls by natural phytoplankton assemblages: Field and laboratory determination of 14C-PCB particle-water index of sorption

Uptake of 14 C-PCB (approximately 54% chlorine by weight) by mixed species assemblages of estuarine phytoplankton and naturally occurring particulate matter was investigated in glass containers in the laboratory and in dialysis culture in Long Island Sound, USA. At a particle concentration of 25 × 10su6 μmsu3 mlit su−1 (it25 ppm), 1555 1160 it19–22% of the 14 C-PCB was sorbed to particles, with it70–72% in the water and it2–3% on container surfaces. At particulate concentrations fourfold higher, 66–69% of the 14 C-PCB activity was sorbed to particles, while water retained 22–23%. In these natural particulate assemblages, which were numerically dominated by the centric diatom Skeletonema costatum, the calculated index of sorption (the ratio of 14 C-PCB sorbed to particles to that in an equal volume of water) averaged 2 ± 1 × 10 4. Sorption of 14 C-PCB to particles was reversible and most 14 C-PCB leached from them within five days when dialysed against 14 C-PCB-free water.

Competition and Predation: Herring Gulls versus Laughing Gulls

Gulls of the genus Larus generally nest colonially, often in mixed-species assemblages. For example, Herring Gulls (L. argentatus) in Europe nest with Lesser Blackbacked Gulls (L. fuscus; Brown 1967, MacRoberts and MacRoberts 1972) and Black-headed Gulls (L. ridibundus; Greenhalgh 1974); and in North America Ringbilled Gulls (L. delawarensis) nest with California Gulls (L. californicus; Vermeer 1970) and Herring Gulls (Southern 1970). It is often difficult to determine whether such assemblages are actually mixed, or if monospecific colonies simply exist side by side. When assemblages are mixed it is often impossible to ascertain whether they are so by choice or because of a lack of suitable nest sites. The rate of competition and predation by one or both species has not been investigated. In this paper I examine competitive interactions and predation between Laughing Gulls (L. atricilla) and Herring Gulls on Clam Island, New Jersey, from 1976 through 1978. Laughing Gulls on the east coast of the United States traditionally nest in Spartina salt marshes (Bent 1921), although at the limits of their range they frequently nest on dry land (Nisbet 1971, Dinsmore and Schreiber 1974). Thus, when Herring Gulls expanded southward in the early 1900's into Maine and Massachusetts, they came into direct conflict with Laughing Gulls (Nisbet 1971, Drury and Kadlec 1974). As early as 1943, Herring Gulls nested with Laughing Gulls in a sand dune colony at Muskeget Island, Massachusetts (Noble and Wurm 1943). Despite initial differences in habitat, the Laughing Gulls disappeared (Nisbet, pers. comm.). Increases in Herring Gulls in the northeast also have been associated with decreases in Common Terns (Sterna hirundo; Nisbet 1973). In the 1950's and 1960's Herring Gulls again expanded their breeding range, nesting as far south as North Carolina with Laughing Gulls (Hailman 1963, Parnell and Soots 1975). They nested on the upper parts of domes on man-made islands while Laughing Gulls occupied low swales between the domes. Where Herring Gulls were absent, Laughing Gulls nested farther up the domes (Parnell and Soots 1975). When Herring Gulls began breeding in more southern areas, they chose to nest in salt marshes, the customary nesting areas of the large and stable Laughing Gull colonies (Burger 1977). Although differences in nest site selection were noted initially, these differences decreased as Herring Gull colonies expanded. Overlap in colony and nest site characteristics is obvious in several New Jersey colonies (Burger and Shisler 1978). Since the first report of Herring Gulls on Clam Island (Rogers 1965), the colony has increased from 50 to 1,200 pairs whereas the Laughing Gull colony of 4,000 to 6,000 pairs remained about the same size through 1976. My primary objectives in this paper are to examine how these species interact temporally and behaviorally, and to determine the result of these interactions in terms of nesting space allocation and reproductive suc-

Aggressive interactions in mixed-species flocks of migrating shorebirds

We studied aggressive interactions in mixed-species assemblages of shorebirds in three tidal habitats in New Jersey. Aggression was higher on the inner beach than on the mudflat or outer beach. For all species on the inner beach, and for black-bellied plovers, Pluvialis squatarola, on the mudflat, aggression increased as density increased; whereas for sanderlings, Calidris alba, on the outer beach, aggression decreased as numbers increased. Interspecific aggression occurred only on the inner beach. Although the total amount of aggression did not correlate with body size, several parameters of aggression did: interspecific aggression index, percentage of encounters that were interspecific, and percentage of interspecific encounters won. These factors are discussed in terms of competition.

The applicability of grain density autoradiography to the quantitative determination of algal species production: A critique

Grain density autoradiography can be utilized to quantitatively determine the productivity of individual species in mixed phytoplankton assemblages but only after grain counts have been corrected for the effects of source geometry on efficiency as well as for the effects of spurious grain formation and erasure. The common simplifying assumption made by all workers to date, that the grain count over a cell is directly proportional to the cell’s radioactivity, is never realized with mixed species assemblages and such attempts at quantification are invalid. The procedure of apportioning total filterable radioactivity to the cells counted in autoradiographic preparations is also suspect. A method of data correction is presented which makes quantification feasible.

Foraminiferal evidence of a modern warming of the North Atlantic Ocean

A comprehensive numerical comparison of living and fossil assemblages of planktonic Foraminifera on an ocean-wide scale suggests that the present ocean is 1·5-2·0°C warmer than a mixed late Recent average. More than 300 core top samples distributed beneath the major North Atlantic water masses as far north as 60°N were compared with the mean annual species compositions at five open-ocean plankton stations in the Western North Atlantic located in an arc from Bermuda to the Labrador Sea. A total of 437 plankton samples collected during 1959–1963 were combined to compute these mean annual assemblages. The core-top assemblages that most closely resemble each of the composite modern plankton averages are consistently displaced to the south and east towards regions of warmer surface waters. The simplest explanation of this geographic shift is that of a recent warming of the ocean. Since most of the surface sediment samples contain mixed species assemblages spanning the last 1000–4000 years, the modern ocean appears to be 1·5-2·0°C warmer than this broad post-hypsithermal average. This is a large deviation for an interval that is generally considered part of the stable climatic regime of a postglacial phase.