scholarly journals Direct evidence of a prey depletion “halo” surrounding a pelagic predator colony

2021 ◽  
Vol 118 (28) ◽  
pp. e2101325118
Author(s):  
Sam B. Weber ◽  
Andrew J. Richardson ◽  
Judith Brown ◽  
Mark Bolton ◽  
Bethany L. Clark ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Environmental Variability ◽  
Dispersion Model ◽  
Central Place ◽  
Natural World ◽  
Model Systems ◽  
Apex Predators ◽  
Top Predators ◽  
Global Positioning System Tracking ◽  
Prey Depletion

Colonially breeding birds and mammals form some of the largest gatherings of apex predators in the natural world and have provided model systems for studying mechanisms of population regulation in animals. According to one influential hypothesis, intense competition for food among large numbers of spatially constrained foragers should result in a zone of prey depletion surrounding such colonies, ultimately limiting their size. However, while indirect and theoretical support for this phenomenon, known as “Ashmole’s halo,” has steadily accumulated, direct evidence remains exceptionally scarce. Using a combination of vessel-based surveys and Global Positioning System tracking, we show that pelagic seabirds breeding at the tropical island that first inspired Ashmole’s hypothesis do indeed deplete their primary prey species (flying fish; Exocoetidae spp.) over a considerable area, with reduced prey density detectable >150 km from the colony. The observed prey gradient was mirrored by an opposing trend in seabird foraging effort, could not be explained by confounding environmental variability, and can be approximated using a mechanistic consumption–dispersion model, incorporating realistic rates of seabird predation and random prey dispersal. Our results provide a rare view of the resource footprint of a pelagic seabird colony and reveal how aggregations of these central-place foraging, marine top predators profoundly influence the oceans that surround them.

Elucidating dingo’s ecological roles: contributions from the Pelorus Island feral goat biocontrol project

2020 ◽  
Author(s):  
Benjamin L. Allen ◽  
Lee R. Allen ◽  
Michael Graham ◽  
Matt Buckman
Keyword(s):  
Native Vegetation ◽  
Apex Predators ◽  
Top Predators ◽  
Goat Population ◽  
Manipulative Experiments ◽  
Ecological Roles ◽  
Important Field ◽  
Small Livestock ◽  
Introduction Experiment ◽  
Feral Goat

ABSTRACT Understanding the ecological roles of apex predators remains an important field of study. The influence of apex predators on ecosystems can be either profound or negligible in different situations, and uncertainty still exists about the ecological roles of most top-predators, including Australian dingoes. This uncertainly is maintained by a dearth of experimental evidence investigating their roles. Such evidence is indispensable if dingo management is to be evidence-based. In this report, we discuss a recent experiment where dingoes were released on to an island as vertebrate biocontrol tools intended to eradicate feral goats and restore native vegetation being threatened by the goats. The experiment was successful, and the dingoes reduced the goat population to one or perhaps two male goats within ~2 years. This predator introduction experiment elucidated dingo’s effects on small livestock, their per capita predation rates, and their invasiveness or their ability to adapt and change their environment. The experiment confirmed that dingoes have the capacity to decimate populations of small livestock species and trigger a trophic cascade by reducing herbivory on vegetation. We encourage further manipulative experiments to explore the ubiquity of these results in different contexts.

scholarly journals Mesopredators change temporal activity in response to a recolonizing apex predator

2019 ◽  
Vol 30 (5) ◽  
pp. 1324-1335 ◽  
Author(s):  
Carolyn R Shores ◽  
Justin A Dellinger ◽  
Eric S Newkirk ◽  
Shannon M Kachel ◽  
Aaron J Wirsing
Keyword(s):  
Activity Patterns ◽  
Niche Overlap ◽  
Lynx Rufus ◽  
Gray Wolf ◽  
Apex Predator ◽  
Apex Predators ◽  
Anthropogenic Landscapes ◽  
Mediated Effects ◽  
Top Predators ◽  
Temporal Overlap

Abstract Apex predators can influence ecosystems through density and behaviorally mediated effects on herbivores and mesopredators. In many parts of the world, apex predators live in, or are returning to, landscapes that have been modified by people; so, it is important to understand their ecological role in anthropogenic landscapes. We used motion-activated game cameras to compare the activity patterns of humans and 2 mesopredators, coyotes (Canis latrans) and bobcats (Lynx rufus), in areas with and without an apex predator, the gray wolf (Canis lupus), in a multiuse landscape of the northwestern United States. In areas with wolves, there was a significant increase in temporal niche overlap between the mesopredators owing to higher levels of coyote activity at all time periods of the day. Temporal overlap between mesopredators and humans also increased significantly in the presence of wolves. Coyotes exposed to wolves increased their activity during dawn, day, and dusk hours. The increase in coyote activity was greatest during the day, when wolves were least active. The direction of change in bobcat activity in areas with wolves was opposite to coyotes, suggesting a behaviorally mediated cascade between wolves, coyotes, and bobcats, although these findings would need to be confirmed with further research. Our findings suggest that mesopredators in human-dominated systems may perceive humans as less dangerous than apex predators, that humans may be more likely to encounter mesopredators in areas occupied by top predators, and that behaviorally mediated effects of apex predators on mesopredators persist in human-dominated landscapes.

The effects of prey depletion on dietary niches of sympatric apex predators in Southeast Asia

2020 ◽  
Author(s):  
Robert STEINMETZ ◽  
Naret SEUATURIEN ◽  
Pairoj INTANAJITJUY ◽  
Pichet INRUEANG ◽  
Kittipat PREMPREE
Keyword(s):  
Southeast Asia ◽  
Apex Predators ◽  
Prey Depletion

Evolution, Microbes, and Changing Ocean Conditions

2020 ◽  
Vol 12 (1) ◽  
pp. 181-208 ◽  
Author(s):  
Sinéad Collins ◽  
Philip W. Boyd ◽  
Martina A. Doblin
Keyword(s):  
Experimental Evolution ◽  
Environmental Variability ◽  
Cumulative Effect ◽  
Model Systems ◽  
Environmental Drivers ◽  
Marine Microbes ◽  
Evolutionary Potential ◽  
Tolerance Limits ◽  
Different Types

Experimental evolution and the associated theory are underutilized in marine microbial studies; the two fields have developed largely in isolation. Here, we review evolutionary tools for addressing four key areas of ocean global change biology: linking plastic and evolutionary trait changes, the contribution of environmental variability to determining trait values, the role of multiple environmental drivers in trait change, and the fate of populations near their tolerance limits. Wherever possible, we highlight which data from marine studies could use evolutionary approaches and where marine model systems can advance our understanding of evolution. Finally, we discuss the emerging field of marine microbial experimental evolution. We propose a framework linking changes in environmental quality (defined as the cumulative effect on population growth rate) with population traits affecting evolutionary potential, in order to understand which evolutionary processes are likely to be most important across a range of locations for different types of marine microbes.

scholarly journals Movement patterns and activity levels are shaped by the neonatal environment in Antarctic fur seal pups

2021 ◽  
Author(s):  
Rebecca Nagel ◽  
Sina Mews ◽  
Timo Adam ◽  
Claire Stainfield ◽  
Cameron Fox-Clarke ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Life Stage ◽  
Explanatory Power ◽  
Central Place ◽  
Activity Levels ◽  
Extrinsic Factors ◽  
Directed Movement ◽  
Antarctic Fur Seal ◽  
Fur Seal ◽  
Tussock Grass

AbstractTracking studies of juveniles are rare compared to those of adults and consequently, little is known about the influence of intrinsic and extrinsic factors on activity during this critical life stage. We therefore collected GPS data from birth until moult from 66 Antarctic fur seal pups in two nearby but contrasting breeding colonies. The Special Study Beach (SSB) is a high-density colony separated from the inland tussock grass habitat by a steep gully, whereas Freshwater Beach (FWB) is a low-density colony that is topographically more open. We investigated the explanatory power of multiple individual-based and environmental variables using a hidden Markov model. We found that activity was typified by central place exploration, with directed movement away from and subsequent return to a location of low activity. The probability of such directed exploration was unaffected by several factors known to influence marine mammal movement including sex, body condition and temperature. Conversely, FWB pups were more active, increased their activity with age and transitioned earlier into the tussock grass, which offers protection from predators and extreme weather. Our study illustrates the profound importance of extrinsic factors to early movement and highlights the adaptive potential of movement in the face of environmental variability.

scholarly journals Observation of superfluidity in a strongly correlated two-dimensional Fermi gas

Science ◽  
2021 ◽  
Vol 372 (6544) ◽  
pp. 844-846
Author(s):  
Lennart Sobirey ◽  
Niclas Luick ◽  
Markus Bohlen ◽  
Hauke Biss ◽  
Henning Moritz ◽  
...  
Keyword(s):  
Periodic Potential ◽  
Direct Evidence ◽  
Interaction Strength ◽  
Fermi Gas ◽  
Model Systems ◽  
Strongly Correlated ◽  
Two Dimensional ◽  
Strong Correlations ◽  
Critical Temperatures ◽  
Reduced Dimensionality

Understanding how strongly correlated two-dimensional (2D) systems can give rise to unconventional superconductivity with high critical temperatures is one of the major unsolved problems in condensed matter physics. Ultracold 2D Fermi gases have emerged as clean and controllable model systems to study the interplay of strong correlations and reduced dimensionality, but direct evidence of superfluidity in these systems has been missing. We demonstrate superfluidity in an ultracold 2D Fermi gas by moving a periodic potential through the system and observing no dissipation below a critical velocity vc. We measure vc as a function of interaction strength and find a maximum in the crossover regime between bosonic and fermionic superfluidity. Our measurements enable systematic studies of the influence of reduced dimensionality on fermionic superfluidity.

scholarly journals Ashmole's halo: direct evidence for prey depletion by a seabird

1987 ◽  
Vol 40 ◽  
pp. 205-208 ◽  
Author(s):  
VL Birt ◽  
TP Birt ◽  
D Goulet ◽  
DK Cairns ◽  
WA Montevecchi
Keyword(s):  
Direct Evidence ◽  
Prey Depletion

scholarly journals Switching from mesopredator to apex predator: how do responses vary in amphibians adapted to cave living?

2020 ◽  
Vol 74 (10) ◽  
Author(s):  
Raoul Manenti ◽  
Andrea Melotto ◽  
Olivier Guillaume ◽  
Gentile Francesco Ficetola ◽  
Enrico Lunghi
Keyword(s):  
Predator Recognition ◽  
Predatory Fish ◽  
Apex Predators ◽  
Fish Prey ◽  
Predator Cues ◽  
Top Predators ◽  
Novel Approach ◽  
Proteus Anguinus ◽  
History Of ◽  
Behavioural Experiments

Abstract The effective detection of both prey and predators is pivotal for the survival of mesopredators. However, the condition of being a mesopredator is strongly context dependent. Here we focus on two aquatic caudate species that have colonised caves: the Pyrenean newt (Calotriton asper) and the olm (Proteus anguinus). The former maintains both surface and subterranean populations, while only cave-adapted populations of the latter exist. Both species are apex predators in underground waterbodies, while the Pyrenean newt is a mesopredator in surface waterbodies. Shifting to a higher level of the trophic web through colonising caves may promote the loss of anti-predator response against surface apex predators, and an increase in the ability to detect prey. To test these two non-exclusive hypotheses, we integrated classical behavioural characterisations with a novel approach: the assessment of lateralisation (i.e. preference for one body side exposure). Behavioural experiments were performed using laboratory-reared individuals. We performed 684 trials on 39 Pyrenean newts and eight olms. Under darkness and light conditions, we tested how exposure to different chemical cues (predatory fish, prey and unknown scent) affected individuals’ activity and lateralisation. Both cave and surface Pyrenean newts responded to predator cues, while olms did not. In Pyrenean newts, predator cues reduced the time spent in movement and time spent in lateralisation associated with hunting. Our results show that predator recognition is maintained in a species where recently separated populations inhabit environments lacking of higher predators, while such behaviour tends to be lost in populations with longer history of adaptation. Significance statement Predator recognition can be maintained in animals adapted to predator free habitats, but varies with their history of adaptation. Species that are not at the apex of the food web can become top predators if they colonise subterranean environments. We compared the behavioural responses of the olm, a strictly cave species with a long underground evolutionary history, and of the Pyrenean newt, a facultative cave species that also has stream-dwelling populations. Moreover, we integrated a classical behavioural characterisation, such as movement detection, with a novel approach: the assessment of lateralisation. While olms do not respond to external predators scent, cave-dwelling newts still recognise it. This clearly indicates that predator recognition is still maintained in species that have colonised predator-free environments more recently.

scholarly journals Conservation of dynamic characteristics of transcriptional regulatory elements in periodic biological processes

2020 ◽  
Author(s):  
Francis C. Motta ◽  
Robert C. Moseley ◽  
Bree Cummins ◽  
Anastasia Deckard ◽  
Steven B. Haase
Keyword(s):  
Gene Regulatory Networks ◽  
Regulatory Networks ◽  
Large Fraction ◽  
Regulatory Elements ◽  
Natural World ◽  
Model Systems ◽  
Model Organisms ◽  
Core Network ◽  
The Core ◽  
Gene Regulatory

AbstractCell and circadian cycles control a large fraction of cell and organismal physiology by regulating large periodic transcriptional programs that encompass anywhere from 15-80% of the genome. The gene-regulatory networks (GRNs) controlling these programs were largely identified by genetics and chromosome mapping approaches in model systems, yet it is unlikely that we have identified all of the core GRN components. Moreover, large periodic transcriptional programs controlling a variety of processes certainly exist in important non-model organisms where genetic approaches to identifying networks are expensive, time-consuming or intractable. Ideally, the core network components could be identified using data-driven approaches on the transcriptome dynamics data already available. Previous work used dynamic gene expression features to identify sets of genes with periodic behavior; our work goes further to distinguish genes by role: core versus their non-regulatory outputs. Here we present a quantitative approach that can identify nodes of GRNs controlling cell or circadian cycles across taxa. There are practical applications of the approach for network biologists, but our findings reveal something unexpected—that there are quantifiable and fundamental shared features of these unrelated GRNs controlling disparate periodic phenotypes.Author summaryCircadian rhythms, cellular division, and the developmental cycles of a multitude of living creatures, including those responsible for infectious diseases, are among the many dynamic phenomena in the natural world that are known to be the eventual output of gene regulatory networks. Identifying the small number of specialized genes that control these dynamic behaviors is of fundamental importance to our understanding of life, and our treatment of disease, but is difficult because of the sheer size of the genomes. We show that the core genes in organisms separated by millions of years of evolution have remarkable similarities that can be used to identify them.

Archaeological Science and the Neolithic

Early Farmers ◽  
2014 ◽  
Author(s):  
Paul Halstead
Keyword(s):  
Land Use ◽  
Direct Evidence ◽  
Analytical Techniques ◽  
Natural World ◽  
Archaeological Science ◽  
Direct Measures

Increasingly diverse applications of ‘archaeological science’ are providing more or less direct evidence for aspects of Neolithic life that, until recently, archaeologists explored using very remote proxy measures (for example, settlement locations as evidence for land use). Nonetheless, many applications of new (and old) analytical techniques continue to conflate the variables of which they are direct measures with others for which they are more or less remote and unreliable proxies. This chapter explores examples of such proxy measures and their unstated underpinning assumptions about human cultural behaviour and, sometimes, the natural world. Closer attention to such assumptions will improve not only the reliability of applications of archaeological science to the Neolithic, but also their reach and resolution.

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