Lévy walk patterns in the foraging movements of spider monkeys (<Emphasis Type="Italic">Ateles geoffroyi</Emphasis>)

Scale invariant patterns have been found in different biological systems, in many cases resembling what physicists have found in other, nonbiological systems. Here we describe the foraging patterns of free-ranging spider monkeys (Ateles geoffroyi) in the forest of the Yucatan Peninsula, Mexico and find that these patterns closely resemble what physicists know as Lévy walks. First, the length of a trajectorys constituent steps, or continuous moves in the same direction, is best described by a power-law distribution in which the frequency of ever larger steps decreases as a negative power function of their length. The rate of this decrease is very close to that predicted by a previous analytical Lévy walk model to be an optimal strategy to search for scarce resources distributed at random. Second, the frequency distribution of the duration of stops or waiting times also approximates to a power-law function. Finally, the mean square displacement during the monkeys first foraging trip increases more rapidly than would be expected from a random walk with constant step length, but within the range predicted for Lévy walks. In view of these results, we analyze the different exponents characterizing the trajectories described by females and males, and by monkeys on their own and when part of a subgroup. We discuss the origin of these patterns and their implications for the foraging ecology of spider monkeys.Communicated by D. Watts     

Tidal and diurnal influence on food consumption of a salt marsh killifish Fundulus heteroclitus

Feeding patterns during four 24-h periods, sampled at 3-h intervals, were investigated for the mummichog Fundulus heteroclitus, in a Delaware, USA tidal marsh. Two factors potentially influencing feeding patterns, time of day and tide height, were examined. On 2 of the sampling periods a low tide occurred in the morning, while on the other 2 sampling periods a high tide occurred in the morning. Results are reported as g-dry wt. of food per g-dry wt. of fish. F. heteroclitus is primarily a daytime feeder that most actively feeds at high tide, regardless of whether or not the high tide inundates marsh surface areas. When tide height was sufficient to inundate the marsh surface, fish invaded these areas and consumed prey characteristic of the marsh surface. F. heteroclitus is an important link in energy transfers between the marsh surface and subtidal systems, enhancing its own energy supplies by consuming marsh surface prey whenever available.     

The transport of oyster larvae in an estuary

Vertical and horizontal distributions of 3 larval stages of the oyster Crassostrea virginica were measured concurrently with phytoplankton species compositions, phytoplankton size distributions and physical hydrographic parameters in tributaries of the Chesapeake Bay (USA) during the oyster spawning seasons of 1980 and 1981. The superposition of the biological distributions upon the physical hydrographic data provide instantaneous distributions of the entire system which are consistent with the upstream transport of oyster larvae. Oyster larvae distributions in the Choptank River and its Broad Creek and Tred Avon River tributaries can be described in terms of three contiguous regions: (1) a common spawning region, (2) an intermediate, upstream transport region and (3) a seed bed region where major spat set occurs. The phytoplankton species compositions and abundances in the size fraction less than 10 m in the tributary system during the transport were sufficient to supply optimum growth requirements of developing larvae. The transport proposed can explain the 30 yr record of consistently higher spat set success in one tributary, Broad Creek, relative to an adjoining tributary, the Tred Avon River. This may be a general mechanism whereby oysters maintain reproductive success and emigrate to seed bed regions in the Chesapeake Bay.Contribution No. 1144 of the McCollum-Pratt Institute and Department of Biology     

Nitrogen uptake and growth of the germlings and mature thalli of Fucus distichus

Fucus distichus L. was collected near Vancouver, Canada, in late fall and early winter, 1981. The effects of the forms of nitrogen (nitrate, ammonium or urea) and periodic exposure to air on growth, rhizoid development and nitrogen uptake in germlings was investigated. Gamete release, fertilization, germination and germling growth had no requirement for a specific form of nitrogen. Periodic exposure to air increased secondary rhizoid development twofold. Nitrate and ammonium uptake rates of the germlings were higher than for the mature thalli (20 to 40 times for nitrate and 8 times for ammonium), while the halfsaturation constant (K _s) values for nitrate were similar (1 to 5 M). The germlings showed saturable uptake kinetics but the mature thalli did not. When germlings were exposed to air it caused a 70% decrease in nitrate uptake, but not change in ammonium uptake. Ammonium uptake in the mature thalli was proportional to the ambient ammonium concentration. Nitrate uptake in the mature thalli appeared to follow saturation kinetics at low nitrate concentrations, but showed a non-saturable component at concentrations greater than 10 M. Presence of ammonium inhibited nitrate uptake by the mature plants but not by the germlings.     

Influence des conditions hivernales sur les productions phyto- et zooplanctoniques en Méditerranée nord-occidentale. I. Structures hydrologiques et distribution des sels nutritifs

During two periods (1 to 15 March and 3 to 17 April, 1969), the R.V. “Jean Charcot” accomplished hydrological, chemical, and biological observations in the northern portion of the Western Mediterranean Sea. The main aim was to study the influence of the intensive vertical mixing of water masses on primary and secondary productions during winter. Earlier work in this area had revealed, in the offshore region, relatively large biomasses and high production rates during spring; considering the low potential fertility of Mediterranean waters, this finding may be explained by the effective vertical transport of nutrients upwards to the photic zone. The present paper discusses the hydrological features and the distribution of nutrients (phosphates and nitrates), in these areas, where, in winter, formation of deep water occurs. Observations were made down to 1,000 m on a grid of stations centred at 42°N; 5° E (“région provençale”) and another series of stations in the region “Corse-Côte d'Azur”. These two areas are characterized by cyclonic gyres, in which each centre shows a sector of high surface density (σ _t > 29.00). The surface mixed layer encountered is not deeper than 100 m; however, the Medoc Group (1970) has described formation of a homogeneous layer down to more than 1000 m. Many well-mixed water columns (maximum temperature and salinity at any depth do not exceed 13°C and 38.45‰, respectively) remain and occupy the western portion of the high surface density area; everywhere, the Mediterranean 3-layer system (superficial, intermediate and deep waters), more or less affected by mixing, remains well developed in the coastal region, and especially in the region of Côte d'Azur and Corsica. At some places, relatively high surface temperature (>13°C) associated with high salinity shows that the intermediate water fraction reaches the surface not only by direct vertical mixing, but also by any other dynamic lifting process, which constitutes another way of nutrient transport to the photic layer. The highest surface nutrient (0.3μ atg/l P?PO₄; 5 μ atg/l N?NO₃) and the lowest surface oxygen content (saturation <90%) are encountered in the mixed area; they are the best indicators of recently upwelled water. The surface layer around the cyclonic area is characterized by the low nutrient content of water of Atlantic origin. The lower salinity (<38%) of this water does not allow deep vertical mixing. During 3 to 17 April, 1969, the survey carried out on the same grid and sections reveals heating effects on all surface waters; the resulting stability in the most superficial layer accomodates the general spring bloom of phytoplankton. Nutrient consumption by photosynthesis in the upper 100 m layer of the surveyed area south of Marseilles was calculated to be: 129.1×10⁶ g-at P?PO₄ per 16,000 km² per month, converted on the atomic basis of P:C=1:106 represents almost 75% of the carbon production obtained by ¹⁴C-uptake measurements.     

Robust population management under uncertainty for structured population models.

Structured population models are increasingly used in decision making, but typically have many entries that are unknown or highly uncertain. We present an approach for the systematic analysis of the effect of uncertainties on long-term population growth or decay. Many decisions for threatened and endangered species are made with poor or no information. We can still make decisions under these circumstances in a manner that is highly defensible, even without making assumptions about the distribution of uncertainty, or limiting ourselves to discussions of single, infinitesimally small changes in the parameters. Suppose that the model (determined by the data) for the population in question predicts long-term growth. Our goal is to determine how uncertain the data can be before the model loses this property. Some uncertainties will maintain long-term growth, and some will lead to long-term decay. The uncertainties are typically structured, and can be described by several parameters. We show how to determine which parameters maintain long-term growth. We illustrate the advantages of the method by applying it to a Peregrine Falcon population. The U.S. Fish and Wildlife Service recently decided to allow minimal harvesting of Peregrine Falcons after their recent removal from the Endangered Species List. Based on published demographic rates, we find that an asymptotic growth rate lambda > 1 is guaranteed with 5% harvest rate up to 3% error in adult survival if no two-year-olds breed, and up to 11% error if all two-year-olds breed. If a population growth rate of 3% or greater is desired, the acceptable error in adult survival decreases to between 1% and 6% depending of the proportion of two-year-olds that breed. These results clearly show the interactions between uncertainties in different parameters, and suggest that a harvest decision at this stage may be premature without solid data on adult survival and the frequency of breeding by young adults.     

The regional framing of climate change: towards a place-based perspective on regional climate change perception in north Frisia

Numerous studies have begun to tackle the social and cultural dimensions of perceiving and framing climate change. Scholars from geography and environmental psychology in particular have started to highlight the importance of so-called place-based approaches to studying regional and local framings of climate change. This paper stands in this tradition. It reports on findings derived from a nationwide survey of perceptions of and reactions to extreme weather events and interviews conducted with inhabitants of three islands in the coastal region of North Frisia (Germany). Coastal dwellers understand climate change through the lens of local and regional experiences of meteorological phenomena, seasonal changes, knowledge of the sea, and changes in local flora and fauna. Our detailed ecolinguistic analysis revealed six prevailing conceptual metaphors: Climate change is an enemy, preventing climate change is fight/war, climate change is punishment for human sins, climate change is overheating/heat, climate change is hot air/hoax and climate change is eco-dictatorship. These metaphors were used to make sense of climate change at the regional level and provide insights into place-based social and cultural conceptualisations of climate change. An understanding of these meanings should feed into developing more grounded climate change adaptation and mitigation strategies in coastal regions.     

Temporal persistence of biological patch structure in an abyssal benthic community

An analysis of living and dead components of a population of deep-sea agglutinated Foraminifera reveals that both segments of the fauna are dispersed nonrandomly on a scale of centimeters. Significant positive correlations between the distribution of living and dead individuals in several species imply that small-scale patch structure in this environment may persist for more than one generation. Mechanisms maintaining such structure may include habitat selection and reproductive patterns and suggest that dispersion pattern is the result of an active interaction between amimals and a heterogeneous physical and biotic environment.     

Inhibition of Amazon Deforestation and Fire by Parks and Indigenous Lands

Abstract:  Conservation scientists generally agree that many types of protected areas will be needed to protect tropical forests. But little is known of the comparative performance of inhabited and uninhabited reserves in slowing the most extreme form of forest disturbance: conversion to agriculture. We used satellite-based maps of land cover and fire occurrence in the Brazilian Amazon to compare the performance of large (>10,000 ha) uninhabited (parks) and inhabited (indigenous lands, extractive reserves, and national forests) reserves. Reserves significantly reduced both deforestation and fire. Deforestation was 1.7 (extractive reserves) to 20 (parks) times higher along the outside versus the inside of the reserve perimeters and fire occurrence was 4 (indigenous lands) to 9 (national forests) times higher. No strong difference in the inhibition of deforestation ( p = 0.11) or fire ( p = 0.34) was found between parks and indigenous lands. However, uninhabited reserves tended to be located away from areas of high deforestation and burning rates. In contrast, indigenous lands were often created in response to frontier expansion, and many prevented deforestation completely despite high rates of deforestation along their boundaries. The inhibitory effect of indigenous lands on deforestation was strong after centuries of contact with the national society and was not correlated with indigenous population density. Indigenous lands occupy one-fifth of the Brazilian Amazon—five times the area under protection in parks—and are currently the most important barrier to Amazon deforestation. As the protected-area network expands from 36% to 41% of the Brazilian Amazon over the coming years, the greatest challenge will be successful reserve implementation in high-risk areas of frontier expansion as indigenous lands are strengthened. This success will depend on a broad base of political support.     

Early holocene openlands in southern New England

The pre-historical vegetation structure in temperate forest regions is much debated among European and North American ecologists and conservationists. Frans Vera's recent hypothesis that large mammals created mosaics of forest and openland vegetation in both regions throughout the Holocene has been particularly controversial and has provoked new approaches to conservation management. Thirty years earlier, American paleoecologists Herb Wright and Margaret Davis debated whether abundant ragweed pollen at Rogers Lake, Connecticut at 9500 yr BP signified local forest openings or long-distance transport of pollen from Midwestern prairies. Using new pollen records from Harvard Forest and the North American Pollen Database, we address this question and offer insights to the openland discussion. Ragweed and other forbs exceed 3.5% at five sites in a restricted area of southern New England between 10,100 and 7700 yr BP. Strong evidence suggests this pollen originated from the landscapes surrounding these sites (supporting Davis), as ragweed pollen percentages do not increase with longitude from New England to the Midwest. Ragweed pollen percentages are also unrelated to basin size and therefore unrelated to the proportion of extraregional pollen in New England. High forbs values were associated with increases in oak, decreases in white pine, and relatively high charcoal values. Modern pollen records with similar forb and tree percentages occur along the Prairie Peninsula region of the Upper Midwest. However, the closest analogue to the southern New England early Holocene assemblages comes from Massachusetts' Walden Pond in the early 18th century. These results and the affiliation of ragweed for open, disturbed habitats suggest that oak-pine forests with large openings persisted for over 2000 years due to dry conditions and perhaps increased fire frequency. This conclusion is corroborated by independent lake level and climate reconstructions. Because these early Holocene openlands have no detectable analogue in New England for the past 7000 years before European settlement, we suggest that all important openlands today are almost exclusively a legacy of Colonial agriculture and should be managed accordingly. Nonetheless, our results may have implications for forest dynamics accompanying projected climate change to more arid conditions in New England over the next century.