scholarly journals How Gradient Affects the Foraging Decisions of Leaf Cutting Ants at the Food Source

2019 ◽  
Author(s):  
◽  
Sam Butler
Keyword(s):  
Foraging Behaviour ◽  
Feeding Site ◽  
Individual Level ◽  
Eusocial Insects ◽  
Methodological Errors ◽  
Foraging Decisions ◽  
Key Factor ◽  
Leaf Cutting ◽  
Load Size ◽  
Insight Into

The eusocial insects have long held the fascination of scientists for their co-operative behaviour, which can range from a small group of workers, to millions strong colonies, such as those found in the leaf cutting ant, Atta cephalotes. Though decades of research have allowed us some insight into their organisation and methods, there are many things that have gone unexplained. One of these is the mystery of why Atta consistently takes leaf loads back to the nest that are significantly smaller than would be optimal, when they should in theory optimise leaf transport rate. While compelling evidence has been presented to suggest that it is at least in part to do with how the leaves are processed inside the nest, here I present evidence to suggest that gradient is another key factor. This is a factor which has been explored only very cursorily up until now in leaf cutting ants, with experiments investigating it being extremely limited in scope, suffer from potential methodological errors or deal with grass cutting ants, which share many traits with leaf cutting ants, but have adapted to face different challenges. Upon a thorough examination of the effects of gradient, it was discovered that A. cephalotes favour a cautious, but more reliable method of transport. At almost every point, their behaviour shows the importance of maintaining grip on steep and vertical gradients to the point where it is prioritised over everything else, including speed and load size. While it may seem paradoxical to suggest that smaller loads, carried slower might result in a higher overall rate of leaf collection, a fast, but reckless approach might result in a high proportion of unsuccessful foraging trips, each of which costs energy and time. As a result, by increasing their success, rather than speed, they minimise wasted effort, loss of workers and potentially, have a higher rate of leaf collection over time. This aspect of leaf cutting ant behaviour shows that leaf cutting ants can change their priorities at the feeding site to best maximise transport success at an individual level, which demonstrates previously unappreciated plasticity and a new lens through which to view future investigations into ant foraging behaviour.

scholarly journals Risso's dolphins perform spin dives to target deep-dwelling prey

2021 ◽  
Vol 8 (12) ◽  
Author(s):  
Fleur Visser ◽  
Onno A. Keller ◽  
Machiel G. Oudejans ◽  
Douglas P. Nowacek ◽  
Annebelle C. M. Kok ◽  
...  
Keyword(s):  
Foraging Behaviour ◽  
Foraging Strategy ◽  
Near Surface ◽  
Grampus Griseus ◽  
Deep Diving ◽  
Foraging Decisions ◽  
Deep Scattering Layer ◽  
Fundamental Insight ◽  
Dense Aggregation ◽  
Insight Into

Foraging decisions of deep-diving cetaceans can provide fundamental insight into food web dynamics of the deep pelagic ocean. Cetacean optimal foraging entails a tight balance between oxygen-conserving dive strategies and access to deep-dwelling prey of sufficient energetic reward. Risso's dolphins ( Grampus griseus ) displayed a thus far unknown dive strategy, which we termed the spin dive. Dives started with intense stroking and right-sided lateral rotation. This remarkable behaviour resulted in a rapid descent. By tracking the fine-scale foraging behaviour of seven tagged individuals, matched with prey layer recordings, we tested the hypothesis that spin dives are foraging dives targeting deep-dwelling prey. Hunting depth traced the diel movement of the deep scattering layer, a dense aggregation of prey, that resides deep during the day and near-surface at night. Individuals shifted their foraging strategy from deep spin dives to shallow non-spin dives around dusk. Spin dives were significantly faster, steeper and deeper than non-spin dives, effectively minimizing transit time to bountiful mesopelagic prey, and were focused on periods when the migratory prey might be easier to catch. Hence, whereas Risso's dolphins were mostly shallow, nocturnal foragers, their spin dives enabled extended and rewarding diurnal foraging on deep-dwelling prey.

scholarly journals No neighbour-induced increase in root growth of soybean and sunflower in mesh divider experiments after controlling for nutrient concentration and soil volume

AoB Plants ◽  
2021 ◽  
Author(s):  
Bin J W Chen ◽  
Li Huang ◽  
Heinjo J During ◽  
Xinyu Wang ◽  
Jiahe Wei ◽  
...  
Keyword(s):  
Root Growth ◽  
Nutrient Concentration ◽  
Ideal Free Distribution ◽  
Plant Performance ◽  
Root Competition ◽  
Individual Level ◽  
Key Factor ◽  
Promising Solution ◽  
Soil Volume ◽  
Ideal Free

Abstract Root competition is a key factor determining plant performance, community structure and ecosystem productivity. To adequately estimate the extent of root proliferation of plants in response to neighbours independently of nutrient availability, one should use a setup that can simultaneously control for both nutrient concentration and soil volume at plant individual level. With a mesh-divider design, which was suggested as a promising solution for this problem, we conducted two intraspecific root competition experiments one with soybean (Glycine max) and the other with sunflower (Helianthus annuus). We found no response of root growth or biomass allocation to intraspecific neighbours, i.e. an ‘ideal free distribution’ (IDF) norm, in soybean; and even a reduced growth as a negative response in sunflower. These responses are all inconsistent with the hypothesis that plants should produce more roots even at the expense of reduced fitness in response to neighbours, i.e. root over-proliferation. Our results suggest that neighbour-induced root over-proliferation is not a ubiquitous feature in plants. By integrating the findings with results from other soybean studies, we conclude that for some species this response could be a genotype-dependent response as a result of natural or artificial selection, or a context-dependent response so that plants can switch from root over-proliferation to IDF depending on the environment of competition. We also critically discuss whether the mesh-driver design is the ideal solution for root competition experiments.

What determines a boundary for navigating a complex street network: evidence from London taxi drivers

2021 ◽  
pp. 1-20
Author(s):  
Eva-Maria Griesbauer ◽  
Ed Manley ◽  
Daniel McNamee ◽  
Jeremy Morley ◽  
Hugo Spiers
Keyword(s):  
Urban Space ◽  
Large Scale ◽  
Route Planning ◽  
Taxi Drivers ◽  
Street Networks ◽  
Planning Models ◽  
Key Factor ◽  
Efficient Planning ◽  
Regent's Park ◽  
Insight Into

Abstract Spatial boundaries play an important role in defining spaces, structuring memory and supporting planning during navigation. Recent models of hierarchical route planning use boundaries to plan efficiently first across regions and then within regions. However, it remains unclear which structures (e.g. parks, rivers, major streets, etc.) will form salient boundaries in real-world cities. This study tested licensed London taxi drivers, who are unique in their ability to navigate London flexibly without physical navigation aids. They were asked to indicate streets they considered as boundaries for London districts or dividing areas. It was found that agreement on boundary streets varied considerably, from some boundaries providing almost no consensus to some boundaries consistently noted as boundaries. Examining the properties of the streets revealed that a key factor in the consistent boundaries was the near rectilinear nature of the designated region (e.g. Mayfair and Soho) and the distinctiveness of parks (e.g. Regent's Park). Surprisingly, the River Thames was not consistently considered as a boundary. These findings provide insight into types of environmental features that lead to the perception of explicit boundaries in large-scale urban space. Because route planning models assume that boundaries are used to segregate the space for efficient planning, these results help make predictions of the likely planning demands of different routes in such complex large-scale street networks. Such predictions could be used to highlight information used for navigation guidance applications to enable more efficient hierarchical planning and learning of large-scale environments.

State- and Individual-Level Predictors of Mexican Death Penalty Support

2017 ◽  
Vol 64 (12) ◽  
pp. 1590-1611 ◽  
Author(s):  
Alexander H. Updegrove ◽  
Erin A. Orrick
Keyword(s):  
Death Penalty ◽  
Capital Punishment ◽  
Mexican Immigrants ◽  
State Level ◽  
The United States ◽  
Individual Level ◽  
Specific Factors ◽  
Nationally Representative ◽  
Future Practice ◽  
Insight Into

Mexico exerts a unique influence on Texas through immigration. As immigrants bring perspectives from their country of origin when they immigrate, studying attitudes toward capital punishment in Mexico may provide insight into ways Mexican immigrants could affect its future practice in Texas. Multilevel modeling is used to examine individual- and state-level predictors of death penalty support among a nationally representative sample of Mexicans. Results indicate age and Catholic affiliation are associated with death penalty support, although not in the expected directions, whereas states bordering the United States are less likely to support capital punishment, despite experiencing less overall peace and a higher average homicide rate. Findings suggest the need for researchers to use culture-specific factors to predict death penalty support.

scholarly journals Telomere length in house sparrows increases in early-life and can be paternally inherited

2021 ◽  
Author(s):  
Sophie Bennett ◽  
Antje Girndt ◽  
Alfredo Sánchez-Tójar ◽  
Terry Burke ◽  
Mirre J. P. Simons ◽  
...  
Keyword(s):  
Telomere Length ◽  
Early Life ◽  
Passer Domesticus ◽  
Age Effects ◽  
Parental Age ◽  
House Sparrows ◽  
Older Parents ◽  
Individual Level ◽  
Ageing Rate ◽  
Insight Into

Offspring of older parents in many species display decreased longevity, a faster ageing rate and lower fecundity than offspring born to younger parents. Biomarkers, such as telomeres, that tend to shorten as individual age, may provide insight into the mechanisms of parental age effects. Parental age could determine telomere length either through inheritance of shortened telomeres or through indirect effects, such as variation in parental care with parent ages, which in turn might lead to variation in offspring telomere length. There is no current consensus as to the heritability of telomere length, and the direction and extent of parental age effects however. To address this, here we experimentally investigate how parental age is associated with telomere length at two time points in early life in a captive population of house sparrows (Passer domesticus). We experimentally separated parental age from sex effects by allowing the parent birds to only mate with young, or old partners. We found that telomere length of the offspring increased between the age of 0.5 and 3 months at the group and individual level, which has been reported previously predominantly in non-avian taxa. We further show that older fathers produced daughters with a greater early-life increase in telomere length, supporting sex-specific inheritance, and or sex-specific non-genetic effects. Overall, our results highlight the need for more studies testing early-life telomere dynamics and sex-specific heritability of telomere length.

scholarly journals Individual-level specialisation and interspecific resource partitioning in bees revealed by pollen DNA metabarcoding

2021 ◽  
Author(s):  
Jan Klečka ◽  
Michael Mikát ◽  
Pavla Koloušková ◽  
Jiří Hadrava ◽  
Jakub Straka
Keyword(s):  
Resource Partitioning ◽  
Foraging Behaviour ◽  
Plant Reproduction ◽  
Short Term ◽  
Temporal Scales ◽  
Individual Level ◽  
Multi Scale ◽  
Foraging Preferences ◽  
Dna Metabarcoding ◽  
Flower Visiting

It is increasingly recognised that intraspecific variation in traits, such as morphology, behaviour, or diet is both ubiquitous and ecologically important. While many species of predators and herbivores are known to display high levels of between-individual diet variation, there is a lack of studies on pollinators. It is important to fill in this gap because individual-level specialisation of flower-visiting insects is expected to affect their efficiency as pollinators with consequences for plant reproduction. Accordingly, the aim of our study was to quantify the level of individual-level specialisation and foraging preferences, as well as interspecific resource partitioning, across different temporal scales in three co-occurring species of bees of the genus Ceratina (Hymenoptera: Apidae: Xylocopinae), C. chalybea, C. nigrolabiata, and C. cucurbitina. We conducted a field experiment where we provided artificial nesting opportunities for the bees and combined a short-term mark-recapture study with the dissection of the bees' nests to obtain repeated samples from individual foraging females and complete pollen provisions from their nests. Hence, we could study variation of the composition of pollen collected by the bees at different temporal scales. We used DNA metabarcoding based on the ITS2 locus to identify the composition of the pollen samples. We found that the composition of pollen carried on the bodies of female bees and stored in the brood provisions in their nests significantly differed among the three co-occurring species. At the intraspecific level, individual females consistently differed in their level of specialisation and in the composition of pollen carried on their bodies and stored in their nests. Our study thus provides evidence of consistent individual-level specialisation in pollinators across multiple temporal scales. We also demonstrate that higher generalisation at the species level stemmed from larger among-individual variation in diets as observed in other types of consumers, such as predators. Our study thus reveals how specialisation and foraging preferences of bees change from the scale of individual foraging bouts to complete pollen provisions accumulated in their nests over their lifetime. Such multi-scale view of foraging behaviour is necessary to improve our understanding of the functioning of plant-flower visitor communities.

Getting Ahead

Teen Spirit ◽  
2020 ◽  
pp. 132-143
Author(s):  
Paul Howe
Keyword(s):  
Free Market ◽  
Economic Behavior ◽  
Social Fabric ◽  
Individual Level ◽  
Economic Decision Making ◽  
Economic Trends ◽  
Individual Decisions ◽  
The Individual ◽  
Adolescent Society ◽  
Insight Into

This chapter assesses how the pervasive influence of the adolescent character provides insight into the workings of another sector of modern life relevant to us all: the economy. Less of a collective undertaking than politics, economic activity is guided primarily by individual decisions and actions in the free market system; so many of the relevant effects are seen first and foremost at the individual level. But these individual effects can multiply and cascade to generate patterns that do have important consequences for the general economic and social fabric. Emotions, misperceptions, intangible costs and benefits, influenced in many instances by underlying character traits, lead people to act in ways that the traditional models do not anticipate. As in other fields, it is only recently that some researchers have started to link personality to economic behavior in interesting and enlightening ways to dig deeper into what makes people tick when it comes to economic decision making and activity. When we combine some of these findings with ideas about the changing contours of character in the adolescent society, we can develop new understandings of some of the more salient economic trends of the past number of years.

scholarly journals Recent Insight into SARS-CoV2 Immunopathology and Rationale for Potential Treatment and Preventive Strategies in COVID-19

Vaccines ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 224 ◽  
Author(s):  
Sara Lega ◽  
Samuele Naviglio ◽  
Stefano Volpi ◽  
Alberto Tommasini
Keyword(s):  
Severe Disease ◽  
Host Immune System ◽  
Great Effort ◽  
Clinical Observations ◽  
Current State ◽  
Key Factor ◽  
Pharmacologic Treatments ◽  
Immunomodulating Drugs ◽  
Insight Into

As the outbreak of the new coronavirus (SARS-CoV-2) infection is spreading globally, great effort is being made to understand the disease pathogenesis and host factors that predispose to disease progression in an attempt to find a window of opportunity for intervention. In addition to the direct cytopathic effect of the virus, the host hyper-inflammatory response has emerged as a key factor in determining disease severity and mortality. Accumulating clinical observations raised hypotheses to explain why some patients develop more severe disease while others only manifest mild or no symptoms. So far, Covid-19 management remains mainly supportive. However, many researches are underway to clarify the role of antiviral and immunomodulating drugs in changing morbidity and mortality in patients who become severely ill. This review summarizes the current state of knowledge on the interaction between SARS-CoV-2 and the host immune system and discusses recent findings on proposed pharmacologic treatments.

Size-related foraging behaviour of the leaf-cutting ant Atta colombica

1991 ◽  
Vol 69 (6) ◽  
pp. 1530-1533 ◽  
Author(s):  
Dave Shutler ◽  
Adele Mullie
Keyword(s):  
Body Size ◽  
Leaf Litter ◽  
Tree Species ◽  
Foraging Behaviour ◽  
Foraging Theory ◽  
Costa Rican ◽  
Leaf Cutting ◽  
Foraging Trail ◽  
Atta Colombica ◽  
Load Mass

In a Costa Rican forest adjacent to cattle pasture, larger individuals of the leaf-cutting ant Atta colombica carried heavier loads and foraged farther from the colony, as predicted by foraging theory. Counter to foraging theory, individual ants did not increase their load mass if they foraged farther from the colony. However, the colony avoided this apparent inefficiency by sending larger ants to more distant trees. The colony harvested simultaneously from several individuals of the same tree species, even though distant trees were twice as far from the colony as nearby trees. The reasons for this behaviour require further investigation. In a wide foraging trail, larger ants travelled faster than their smaller counterparts. In addition, ant velocity was reduced when loads were experimentally supplemented, and increased when loads were experimentally reduced. Ants using narrow trails in the leaf litter may all be constrained to travel at the same speed, irrespective of load or body size, simply because they get in each other's way.

Consideration: Review of Research and Prospects for Future Insights

1997 ◽  
Vol 34 (3) ◽  
pp. 406-410 ◽  
Author(s):  
John H. Roberts ◽  
James M. Lattin
Keyword(s):  
Decision Process ◽  
Marketing Research ◽  
Additional Insight ◽  
Consideration Set ◽  
Individual Level ◽  
Consumer Decision Process ◽  
New Ideas ◽  
Level Model ◽  
Consideration Set Formation ◽  
Insight Into

The authors review the behavioral underpinnings of consideration set formation and revisit the theoretical and empirical evidence that led them to develop an individual level model of consideration. They synthesize the research that has appeared since their 1991 article in the Journal of Marketing Research, examining new ideas, reviewing evolving measurement methodologies, and suggesting several areas for further research that they believe will provide additional insight into the consideration phase of the consumer decision process.

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