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Whitehead SC, Sahai SY, Stonemetz J, Yapici N. Exploration-exploitation trade-off is regulated by metabolic state and taste value in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.13.594045. [PMID: 38798663 PMCID: PMC11118379 DOI: 10.1101/2024.05.13.594045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Similar to other animals, the fly, Drosophila melanogaster, changes its foraging strategy from exploration to exploitation upon encountering a nutrient-rich food source. However, the impact of metabolic state or taste/nutrient value on exploration vs. exploitation decisions in flies is poorly understood. Here, we developed a one-source foraging assay that uses automated video tracking coupled with high-resolution measurements of food ingestion to investigate the behavioral variables flies use when foraging for food with different taste/caloric values and when in different metabolic states. We found that flies alter their foraging and ingestive behaviors based on their hunger state and the concentration of the sucrose solution. Interestingly, sugar-blind flies did not transition from exploration to exploitation upon finding a high-concentration sucrose solution, suggesting that taste sensory input, as opposed to post-ingestive nutrient feedback, plays a crucial role in determining the foraging decisions of flies. Using a Generalized Linear Model (GLM), we showed that hunger state and sugar volume ingested, but not the nutrient or taste value of the food, influence flies' radial distance to the food source, a strong indicator of exploitation. Our behavioral paradigm and theoretical framework offer a promising avenue for investigating the neural mechanisms underlying state and value-based foraging decisions in flies, setting the stage for systematically identifying the neuronal circuits that drive these behaviors.
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Affiliation(s)
- Samuel C. Whitehead
- Department of Physics, Cornell University, Ithaca, NY,14853, USA
- Current address: California Institute of Technology, Pasadena, CA, USA
| | - Saumya Y. Sahai
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, 14853, USA
- Current address: Amazon.com LLC, USA
| | - Jamie Stonemetz
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, 14853, USA
- Current address: Department of Biology, Brandeis University, Waltham, MA, USA
| | - Nilay Yapici
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, 14853, USA
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2
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Fandel AD, Silva K, Bailey H. Vocal signatures affected by population identity and environmental sound levels. PLoS One 2024; 19:e0299250. [PMID: 38635752 PMCID: PMC11025965 DOI: 10.1371/journal.pone.0299250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 02/06/2024] [Indexed: 04/20/2024] Open
Abstract
Passive acoustic monitoring has improved our understanding of vocalizing organisms in remote habitats and during all weather conditions. Many vocally active species are highly mobile, and their populations overlap. However, distinct vocalizations allow the tracking and discrimination of individuals or populations. Using signature whistles, the individually distinct calls of bottlenose dolphins, we calculated a minimum abundance of individuals, characterized and compared signature whistles from five locations, and determined reoccurrences of individuals throughout the Mid-Atlantic Bight and Chesapeake Bay, USA. We identified 1,888 signature whistles in which the duration, number of extrema, start, end, and minimum frequencies of signature whistles varied significantly by site. All characteristics of signature whistles were deemed important for determining from which site the whistle originated and due to the distinct signature whistle characteristics and lack of spatial mixing of the dolphins detected at the Offshore site, we suspect that these dolphins are of a different population than those at the Coastal and Bay sites. Signature whistles were also found to be shorter when sound levels were higher. Using only the passively recorded vocalizations of this marine top predator, we obtained information about its population and how it is affected by ambient sound levels, which will increase as offshore wind energy is developed. In this rapidly developing area, these calls offer critical management insights for this protected species.
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Affiliation(s)
- Amber D. Fandel
- Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, United States of America
| | - Kirsten Silva
- Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, United States of America
| | - Helen Bailey
- Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, MD, United States of America
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3
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Istiban MN, De Fruyt N, Kenis S, Beets I. Evolutionary conserved peptide and glycoprotein hormone-like neuroendocrine systems in C. elegans. Mol Cell Endocrinol 2024; 584:112162. [PMID: 38290646 PMCID: PMC11004728 DOI: 10.1016/j.mce.2024.112162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/11/2024] [Accepted: 01/15/2024] [Indexed: 02/01/2024]
Abstract
Peptides and protein hormones form the largest group of secreted signals that mediate intercellular communication and are central regulators of physiology and behavior in all animals. Phylogenetic analyses and biochemical identifications of peptide-receptor systems reveal a broad evolutionary conservation of these signaling systems at the molecular level. Substantial progress has been made in recent years on characterizing the physiological and putative ancestral roles of many peptide systems through comparative studies in invertebrate models. Several peptides and protein hormones are not only molecularly conserved but also have conserved roles across animal phyla. Here, we focus on functional insights gained in the nematode Caenorhabditis elegans that, with its compact and well-described nervous system, provides a powerful model to dissect neuroendocrine signaling networks involved in the control of physiology and behavior. We summarize recent discoveries on the evolutionary conservation and knowledge on the functions of peptide and protein hormone systems in C. elegans.
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Affiliation(s)
- Majdulin Nabil Istiban
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium
| | - Nathan De Fruyt
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium
| | - Signe Kenis
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium
| | - Isabel Beets
- Neural Signaling and Circuit Plasticity, Department of Biology, KU Leuven, 3000, Leuven, Belgium.
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4
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Fernandez-Betelu O, Iorio-Merlo V, Graham IM, Cheney BJ, Prentice SM, Cheng RX, Thompson PM. Variation in foraging activity influences area-restricted search behaviour by bottlenose dolphins. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221613. [PMID: 37325592 PMCID: PMC10265022 DOI: 10.1098/rsos.221613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 05/26/2023] [Indexed: 06/17/2023]
Abstract
Area-restricted search (ARS) behaviour is commonly used to characterize spatio-temporal variation in foraging activity of predators, but evidence of the drivers underlying this behaviour in marine systems is sparse. Advances in underwater sound recording techniques and automated processing of acoustic data now provide opportunities to investigate these questions where species use different vocalizations when encountering prey. Here, we used passive acoustics to investigate drivers of ARS behaviour in a population of dolphins and determined if residency in key foraging areas increased following encounters with prey. Analyses were based on two independent proxies of foraging: echolocation buzzes (widely used as foraging proxies) and bray calls (vocalizations linked to salmon predation attempts). Echolocation buzzes were extracted from echolocation data loggers and bray calls from broadband recordings by a convolutional neural network. We found a strong positive relationship between the duration of encounters and the frequency of both foraging proxies, supporting the theory that bottlenose dolphins engage in ARS behaviour in response to higher prey encounter rates. This study provides empirical evidence for one driver of ARS behaviour and demonstrates the potential for applying passive acoustic monitoring in combination with deep learning-based techniques to investigate the behaviour of vocal animals.
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Affiliation(s)
- Oihane Fernandez-Betelu
- Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, Lighthouse Field Station, Cromarty IV11 8YL, UK
| | - Virginia Iorio-Merlo
- Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, Lighthouse Field Station, Cromarty IV11 8YL, UK
| | - Isla M. Graham
- Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, Lighthouse Field Station, Cromarty IV11 8YL, UK
| | - Barbara J. Cheney
- Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, Lighthouse Field Station, Cromarty IV11 8YL, UK
| | - Simone M. Prentice
- Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, Lighthouse Field Station, Cromarty IV11 8YL, UK
| | - Rachael Xi Cheng
- Leibniz Institute for Zoo and Wildlife Research (IZW), Berlin 10315, Germany
| | - Paul M. Thompson
- Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, Lighthouse Field Station, Cromarty IV11 8YL, UK
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5
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Florko KRN, Shuert CR, Cheung WWL, Ferguson SH, Jonsen ID, Rosen DAS, Sumaila UR, Tai TC, Yurkowski DJ, Auger-Méthé M. Linking movement and dive data to prey distribution models: new insights in foraging behaviour and potential pitfalls of movement analyses. MOVEMENT ECOLOGY 2023; 11:17. [PMID: 36959671 PMCID: PMC10037791 DOI: 10.1186/s40462-023-00377-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 03/04/2023] [Indexed: 06/08/2023]
Abstract
BACKGROUND Animal movement data are regularly used to infer foraging behaviour and relationships to environmental characteristics, often to help identify critical habitat. To characterize foraging, movement models make a set of assumptions rooted in theory, for example, time spent foraging in an area increases with higher prey density. METHODS We assessed the validity of these assumptions by associating horizontal movement and diving of satellite-telemetered ringed seals (Pusa hispida)-an opportunistic predator-in Hudson Bay, Canada, to modelled prey data and environmental proxies. RESULTS Modelled prey biomass data performed better than their environmental proxies (e.g., sea surface temperature) for explaining seal movement; however movement was not related to foraging effort. Counter to theory, seals appeared to forage more in areas with relatively lower prey diversity and biomass, potentially due to reduced foraging efficiency in those areas. CONCLUSIONS Our study highlights the need to validate movement analyses with prey data to effectively estimate the relationship between prey availability and foraging behaviour.
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Affiliation(s)
- Katie R N Florko
- Aquatic Ecosystem Research Laboratory, Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
| | - Courtney R Shuert
- Department of Integrative Biology, University of Windsor, Windsor, ON, Canada
- Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB, Canada
| | - William W L Cheung
- Aquatic Ecosystem Research Laboratory, Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Steven H Ferguson
- Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB, Canada
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Ian D Jonsen
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia
| | - David A S Rosen
- Aquatic Ecosystem Research Laboratory, Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - U Rashid Sumaila
- Aquatic Ecosystem Research Laboratory, Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Travis C Tai
- Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC, Canada
| | - David J Yurkowski
- Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB, Canada
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Marie Auger-Méthé
- Aquatic Ecosystem Research Laboratory, Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC, V6T 1Z4, Canada
- Department of Statistics, University of British Columbia, Vancouver, BC, Canada
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6
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Dorfman A, Hills TT, Scharf I. A guide to area-restricted search: a foundational foraging behaviour. Biol Rev Camb Philos Soc 2022; 97:2076-2089. [PMID: 35821610 PMCID: PMC9796321 DOI: 10.1111/brv.12883] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 06/14/2022] [Accepted: 06/16/2022] [Indexed: 01/01/2023]
Abstract
Area-restricted search is the capacity to change search effort adaptively in response to resource encounters or expectations, from directional exploration (global, extensive search) to focused exploitation (local, intensive search). This search pattern is used by numerous organisms, from worms and insects to humans, to find various targets, such as food, mates, nests, and other resources. Area-restricted search has been studied for at least 80 years by ecologists, and more recently in the neurological and psychological literature. In general, the conditions promoting this search pattern are: (1) clustered resources; (2) active search (e.g. not a sit-and-wait predator); (3) searcher memory for recent target encounters or expectations; and (4) searcher ignorance about the exact location of targets. Because area-restricted search adapts to resource encounters, the search can be performed at multiple spatial scales. Models and experiments have demonstrated that area-restricted search is superior to alternative search patterns that do not involve a memory of the exact location of the target, such as correlated random walks or Lévy walks/flights. Area-restricted search is triggered by sensory cues whereas concentrated search in the absence of sensory cues is associated with other forms of foraging. Some neural underpinnings of area-restricted search are probably shared across metazoans, suggesting a shared ancestry and a shared solution to a common ecological problem of finding clustered resources. Area-restricted search is also apparent in other domains, such as memory and visual search in humans, which may indicate an exaptation from spatial search to other forms of search. Here, we review these various aspects of area-restricted search, as well as how to identify it, and point to open questions.
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Affiliation(s)
- Arik Dorfman
- School of Zoology, George S. Wise Faculty of Life SciencesTel Aviv University6997801Tel AvivIsrael
| | - Thomas T. Hills
- Department of PsychologyUniversity of WarwickCoventryCV4 7ALUK
| | - Inon Scharf
- School of Zoology, George S. Wise Faculty of Life SciencesTel Aviv University6997801Tel AvivIsrael
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7
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Iorio-Merlo V, Graham IM, Hewitt RC, Aarts G, Pirotta E, Hastie GD, Thompson PM. Prey encounters and spatial memory influence use of foraging patches in a marine central place forager. Proc Biol Sci 2022; 289:20212261. [PMID: 35232237 PMCID: PMC8889173 DOI: 10.1098/rspb.2021.2261] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Given the patchiness and long-term predictability of marine resources, memory of high-quality foraging grounds is expected to provide fitness advantages for central place foragers. However, it remains challenging to characterize how marine predators integrate memory with recent prey encounters to adjust fine-scale movement and use of foraging patches. Here, we used two months of movement data from harbour seals (Phoca vitulina) to quantify the repeatability in foraging patches as a proxy for memory. We then integrated these data into analyses of fine-scale movement and underwater behaviour to test how both spatial memory and prey encounter rates influenced the seals' area-restricted search (ARS) behaviour. Specifically, we used one month's GPS data from 29 individuals to build spatial memory maps of searched areas and archived accelerometery data from a subset of five individuals to detect prey catch attempts, a proxy for prey encounters. Individuals were highly consistent in the areas they visited over two consecutive months. Hidden Markov models showed that both spatial memory and prey encounters increased the probability of seals initiating ARS. These results provide evidence that predators use memory to adjust their fine-scale movement, and this ability should be accounted for in movement models.
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Affiliation(s)
- Virginia Iorio-Merlo
- School of Biological Sciences, Lighthouse Field Station, University of Aberdeen, Cromarty, Ross-shire IV11 8YJ, UK
| | - Isla M Graham
- School of Biological Sciences, Lighthouse Field Station, University of Aberdeen, Cromarty, Ross-shire IV11 8YJ, UK
| | - Rebecca C Hewitt
- School of Biological Sciences, Lighthouse Field Station, University of Aberdeen, Cromarty, Ross-shire IV11 8YJ, UK
| | - Geert Aarts
- Wildlife Ecology and Conservation Group and Wageningen Marine Research, Wageningen University and Research, Ankerpark 27, 1781 AG Den Helder, The Netherlands.,Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, Texel, The Netherlands
| | - Enrico Pirotta
- Centre for Research into Ecological and Environmental Modelling, University of St Andrews, St Andrews, Fife KY16 9LZ, UK.,School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland
| | - Gordon D Hastie
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, UK
| | - Paul M Thompson
- School of Biological Sciences, Lighthouse Field Station, University of Aberdeen, Cromarty, Ross-shire IV11 8YJ, UK
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8
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Parsons MJG, Lin TH, Mooney TA, Erbe C, Juanes F, Lammers M, Li S, Linke S, Looby A, Nedelec SL, Van Opzeeland I, Radford C, Rice AN, Sayigh L, Stanley J, Urban E, Di Iorio L. Sounding the Call for a Global Library of Underwater Biological Sounds. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.810156] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Aquatic environments encompass the world’s most extensive habitats, rich with sounds produced by a diversity of animals. Passive acoustic monitoring (PAM) is an increasingly accessible remote sensing technology that uses hydrophones to listen to the underwater world and represents an unprecedented, non-invasive method to monitor underwater environments. This information can assist in the delineation of biologically important areas via detection of sound-producing species or characterization of ecosystem type and condition, inferred from the acoustic properties of the local soundscape. At a time when worldwide biodiversity is in significant decline and underwater soundscapes are being altered as a result of anthropogenic impacts, there is a need to document, quantify, and understand biotic sound sources–potentially before they disappear. A significant step toward these goals is the development of a web-based, open-access platform that provides: (1) a reference library of known and unknown biological sound sources (by integrating and expanding existing libraries around the world); (2) a data repository portal for annotated and unannotated audio recordings of single sources and of soundscapes; (3) a training platform for artificial intelligence algorithms for signal detection and classification; and (4) a citizen science-based application for public users. Although individually, these resources are often met on regional and taxa-specific scales, many are not sustained and, collectively, an enduring global database with an integrated platform has not been realized. We discuss the benefits such a program can provide, previous calls for global data-sharing and reference libraries, and the challenges that need to be overcome to bring together bio- and ecoacousticians, bioinformaticians, propagation experts, web engineers, and signal processing specialists (e.g., artificial intelligence) with the necessary support and funding to build a sustainable and scalable platform that could address the needs of all contributors and stakeholders into the future.
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9
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Ramachandran S, Banerjee N, Bhattacharya R, Lemons ML, Florman J, Lambert CM, Touroutine D, Alexander K, Schoofs L, Alkema MJ, Beets I, Francis MM. A conserved neuropeptide system links head and body motor circuits to enable adaptive behavior. eLife 2021; 10:71747. [PMID: 34766905 PMCID: PMC8626090 DOI: 10.7554/elife.71747] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 11/11/2021] [Indexed: 01/11/2023] Open
Abstract
Neuromodulators promote adaptive behaviors that are often complex and involve concerted activity changes across circuits that are often not physically connected. It is not well understood how neuromodulatory systems accomplish these tasks. Here, we show that the Caenorhabditis elegans NLP-12 neuropeptide system shapes responses to food availability by modulating the activity of head and body wall motor neurons through alternate G-protein coupled receptor (GPCR) targets, CKR-1 and CKR-2. We show ckr-2 deletion reduces body bend depth during movement under basal conditions. We demonstrate CKR-1 is a functional NLP-12 receptor and define its expression in the nervous system. In contrast to basal locomotion, biased CKR-1 GPCR stimulation of head motor neurons promotes turning during local searching. Deletion of ckr-1 reduces head neuron activity and diminishes turning while specific ckr-1 overexpression or head neuron activation promote turning. Thus, our studies suggest locomotor responses to changing food availability are regulated through conditional NLP-12 stimulation of head or body wall motor circuits.
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Affiliation(s)
- Shankar Ramachandran
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Navonil Banerjee
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Raja Bhattacharya
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Michele L Lemons
- Department of Biological and Physical Sciences, Assumption University, Worcester, United States
| | - Jeremy Florman
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Christopher M Lambert
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Denis Touroutine
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Kellianne Alexander
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Liliane Schoofs
- Department of Biology, University of Leuven (KU Leuven), Leuven, Belgium
| | - Mark J Alkema
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Isabel Beets
- Department of Biology, University of Leuven (KU Leuven), Leuven, Belgium
| | - Michael M Francis
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
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10
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Chow CFY, Wassénius E, Dornelas M, Hoey AS. Species differences drive spatial scaling of foraging patterns in herbivorous reef fishes. OIKOS 2021. [DOI: 10.1111/oik.08713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Cher F. Y. Chow
- Centre for Biological Diversity and Scottish Oceans Inst., School of Biology, Univ. of St Andrews St Andrews UK
| | - Emmy Wassénius
- Centre for Biological Diversity and Scottish Oceans Inst., School of Biology, Univ. of St Andrews St Andrews UK
- Global Economic Dynamics and the Biosphere, Royal Swedish Academy of Science Stockholm Sweden
- Stockholm Resilience Center, Stockholm Univ. Stockholm Sweden
| | - Maria Dornelas
- Centre for Biological Diversity and Scottish Oceans Inst., School of Biology, Univ. of St Andrews St Andrews UK
| | - Andrew S. Hoey
- ARC Centre of Excellence for Coral Reef Studies, James Cook Univ. Townsville Queensland Australia
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11
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Armstrong AO, Stevens GMW, Townsend KA, Murray A, Bennett MB, Armstrong AJ, Uribe-Palomino J, Hosegood P, Dudgeon CL, Richardson AJ. Reef manta rays forage on tidally driven, high density zooplankton patches in Hanifaru Bay, Maldives. PeerJ 2021; 9:e11992. [PMID: 34513330 PMCID: PMC8388554 DOI: 10.7717/peerj.11992] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/27/2021] [Indexed: 12/12/2022] Open
Abstract
Manta rays forage for zooplankton in tropical and subtropical marine environments, which are generally nutrient-poor. Feeding often occurs at predictable locations where these large, mobile cartilaginous fishes congregate to exploit ephemeral productivity hotspots. Investigating the zooplankton dynamics that lead to such feeding aggregations remains a key question for understanding their movement ecology. The aim of this study is to investigate the feeding environment at the largest known aggregation for reef manta rays Mobula alfredi in the world. We sampled zooplankton throughout the tidal cycle, and recorded M. alfredi activity and behaviour, alongside environmental variables at Hanifaru Bay, Maldives. We constructed generalised linear models to investigate possible relationships between zooplankton dynamics, environmental parameters, and how they influenced M. alfredi abundance, behaviour, and foraging strategies. Zooplankton biomass changed rapidly throughout the tidal cycle, and M. alfredi feeding events were significantly related to high zooplankton biomass. Mobula alfredi switched from non-feeding to feeding behaviour at a prey density threshold of 53.7 mg dry mass m−3; more than double the calculated density estimates needed to theoretically meet their metabolic requirements. The highest numbers of M. alfredi observed in Hanifaru Bay corresponded to when they were engaged in feeding behaviour. The community composition of zooplankton was different when M. alfredi was feeding (dominated by copepods and crustaceans) compared to when present but not feeding (more gelatinous species present than in feeding samples). The dominant zooplankton species recorded was Undinula vulgaris. This is a large-bodied calanoid copepod species that blooms in oceanic waters, suggesting offshore influences at the site. Here, we have characterised aspects of the feeding environment for M. alfredi in Hanifaru Bay and identified some of the conditions that may result in large aggregations of this threatened planktivore, and this information can help inform management of this economically important marine protected area.
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Affiliation(s)
- Asia O Armstrong
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Guy M W Stevens
- The Manta Trust, Catemwood House, Norwood Lane, Corscombe, Dorset, United Kingdom
| | - Kathy A Townsend
- School of Science, Technology, and Engineering, University of Sunshine Coast, Hervey Bay, Queensland, Australia
| | - Annie Murray
- The Manta Trust, Catemwood House, Norwood Lane, Corscombe, Dorset, United Kingdom
| | - Michael B Bennett
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Amelia J Armstrong
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Julian Uribe-Palomino
- Queensland Biosciences Precinct, CSIRO Oceans and Atmosphere, St Lucia, Queensland, Australia
| | - Phil Hosegood
- School of Biological and Marine Sciences, University of Plymouth, Plymouth, Devon, United Kingdom
| | - Christine L Dudgeon
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia.,School of Science, Technology, and Engineering, University of Sunshine Coast, Hervey Bay, Queensland, Australia
| | - Anthony J Richardson
- Queensland Biosciences Precinct, CSIRO Oceans and Atmosphere, St Lucia, Queensland, Australia.,School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland, Australia
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12
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Foraging behavior in visual search: A review of theoretical and mathematical models in humans and animals. PSYCHOLOGICAL RESEARCH 2021; 86:331-349. [PMID: 33745028 DOI: 10.1007/s00426-021-01499-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 03/02/2021] [Indexed: 10/21/2022]
Abstract
Visual search (VS) is a fundamental task in daily life widely studied for over half a century. A variant of the classic paradigm-searching one target among distractors-requires the observer to look for several (undetermined) instances of a target (so-called foraging) or several targets that may appear an undefined number of times (recently named as hybrid foraging). In these searches, besides looking for targets, the observer must decide how much time is needed to exploit the area, and when to quit the search to eventually explore new search options. In fact, visual foraging is a very common search task in the real world, probably involving additional cognitive functions than typical VS. It has been widely studied in natural animal environments, for which several mathematical models have been proposed, and just recently applied to humans: Lévy processes, composite and area-restricted search models, marginal value theorem, and Bayesian learning (among others). We conducted a systematic search in the literature to understand those mathematical models and study its applicability in human visual foraging. The review suggests that these models might be the first step, but they seem to be limited to fully comprehend foraging in visual search. There are essential variables involving human visual foraging still to be established and understood. Indeed, a jointly theoretical interpretation based on the different models reviewed could better account for its understanding. In addition, some other relevant variables, such as certain individual differences or time perception might be crucial to understanding visual foraging in humans.
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13
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Effects of intense storm events on dolphin occurrence and foraging behavior. Sci Rep 2020; 10:19247. [PMID: 33159135 PMCID: PMC7648104 DOI: 10.1038/s41598-020-76077-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 10/22/2020] [Indexed: 11/08/2022] Open
Abstract
As storms become increasingly intense and frequent due to climate change, we must better understand how they alter environmental conditions and impact species. However, storms are ephemeral and provide logistical challenges that prevent visual surveys commonly used to understand marine mammal ecology. Thus, relatively little is known about top predators’ responses to such environmental disturbances. In this study, we utilized passive acoustic monitoring to characterize the response of bottlenose dolphins to intense storms offshore Maryland, USA between 2015 and 2017. During and following four autumnal storms, dolphins were detected less frequently and for shorter periods of time. However, dolphins spent a significantly higher percentage of their encounters feeding after the storm than they did before or during. This change in foraging may have resulted from altered distributions and behavior of their prey species, which are prone to responding to environmental changes, such as varied sea surface temperatures caused by storms. It is increasingly vital to determine how these intense storms alter oceanography, prey movements, and the behavior of top predators.
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