scholarly journals Combined measurements of prey availability explain habitat selection in foraging seabirds

2018 ◽  
Vol 14 (8) ◽  
pp. 20180348 ◽  
Author(s):  
James J. Waggitt ◽  
Pierre W. Cazenave ◽  
Leigh M. Howarth ◽  
Peter G. H. Evans ◽  
Jeroen van der Kooij ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Prey Availability ◽  
Habitat Characteristics ◽  
Foraging Efficiency ◽  
Single Measurement ◽  
Marine Renewable Energy ◽  
Top Predators ◽  
Mixed Water ◽  
Manx Shearwater ◽  
Combined Measurements

Understanding links between habitat characteristics and foraging efficiency helps predict how environmental changes influence populations of top predators. This study examines whether measurements of prey (clupeids) availability varied over stratification gradients, and determined if any of those measurements coincided with aggregations of foraging seabirds (common guillemot Uria aalge and Manx shearwater Puffinus puffinus ) in the Celtic Sea, UK. The probability of encountering foraging seabirds was highest around fronts between mixed and stratified water. Prey were denser and shallower in mixed water, whilst encounters with prey were most frequent in stratified water. Therefore, no single measurement of increased prey availability coincided with the location of fronts. However, when considered in combination, overall prey availability was highest in these areas. These results show that top predators may select foraging habitats by trading-off several measurements of prey availability. By showing that top predators select areas where prey switch between behaviours, these results also identify a mechanism that could explain the wider importance of edge habitats for these taxa. As offshore developments (e.g. marine renewable energy installations) change patterns of stratification, their construction may have consequences on the foraging efficiency of seabirds.

scholarly journals Impact of small-scale environmental perturbations on local marine food resources: a case study of a predator, the little penguin

2009 ◽  
Vol 276 (1676) ◽  
pp. 4105-4109 ◽  
Author(s):  
Yan Ropert-Coudert ◽  
Akiko Kato ◽  
André Chiaradia
Keyword(s):  
Breeding Success ◽  
Environmental Changes ◽  
Foraging Efficiency ◽  
Small Scale ◽  
Breeding Period ◽  
Environmental Perturbations ◽  
Top Predators ◽  
The Impact ◽  
Mixed Water

Although the impact of environmental changes on the demographic parameters of top predators is well established, the mechanisms by which populations are affected remain poorly understood. Here, we show that a reduction in the thermal stratification of coastal water masses between 2005 and 2006 was associated with reduced foraging and breeding success of little penguins Eudyptula minor , major bio-indicators of the Bass Strait ecosystem in southern Australia. The foraging patterns of the penguins suggest that their prey disperse widely in poorly stratified waters, leading to reduced foraging efficiency and poor breeding success. Mixed water regimes resulting from storms are currently unusual during the breeding period of these birds, but are expected to become more frequent due to climate change.

The Effects of the Hypsithermal on Prehistoric Foraging Efficiency in Missouri

2005 ◽  
Vol 70 (1) ◽  
pp. 91-106 ◽  
Author(s):  
Steve Wolverton
Keyword(s):  
Environmental Change ◽  
Environmental Changes ◽  
Choice Model ◽  
Prey Availability ◽  
Critical Factor ◽  
Analytical Techniques ◽  
Foraging Theory ◽  
Foraging Efficiency ◽  
Resource Depression ◽  
Human Predation

Archaeological studies of temporal changes in human predation strategy using foraging theory tend to focus on the role of overexploitation of important prey resources and resulting resource depression. An alternative use of the prey-choice model framed under foraging theory is to investigate the influence of environmental changes, such as increases in climate stress, on prey availability. Environmental change can be expected to produce many of the same effects on human predation strategy as resource depression. Here analytical techniques typically used to study the effects of over-predation and resource depression caused by humans are used to monitor their response to fluctuations in prey availability related to climate change during the Holocene in Missouri. Data and interpretations presented here add to the growing body of zooarchaeological foraging theory literature implicating environmental change as a critical factor in human diet.

scholarly journals Prey Size Decline as a Unifying Ecological Selecting Agent in Pleistocene Human Evolution

Quaternary ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 7
Author(s):  
Miki Ben-Dor ◽  
Ran Barkai
Keyword(s):  
Prey Size ◽  
Prey Availability ◽  
Stone Tool ◽  
Foraging Efficiency ◽  
Energetic Cost ◽  
Large Prey ◽  
Biomass Density ◽  
Cultural Changes ◽  
Progressive Decline ◽  
Brain Expansion

We hypothesize that megafauna extinctions throughout the Pleistocene, that led to a progressive decline in large prey availability, were a primary selecting agent in key evolutionary and cultural changes in human prehistory. The Pleistocene human past is characterized by a series of transformations that include the evolution of new physiological traits and the adoption, assimilation, and replacement of cultural and behavioral patterns. Some changes, such as brain expansion, use of fire, developments in stone-tool technologies, or the scale of resource intensification, were uncharacteristically progressive. We previously hypothesized that humans specialized in acquiring large prey because of their higher foraging efficiency, high biomass density, higher fat content, and the use of less complex tools for their acquisition. Here, we argue that the need to mitigate the additional energetic cost of acquiring progressively smaller prey may have been an ecological selecting agent in fundamental adaptive modes demonstrated in the Paleolithic archaeological record. We describe several potential associations between prey size decline and specific evolutionary and cultural changes that might have been driven by the need to adapt to increased energetic demands while hunting and processing smaller and smaller game.

Dietary composition of endangered seahorses determined by stable isotope analysis

2017 ◽  
Vol 68 (5) ◽  
pp. 831 ◽  
Author(s):  
S. Valladares ◽  
D. X. Soto ◽  
M. Planas
Keyword(s):  
Stable Isotope ◽  
Environmental Changes ◽  
Conservation Status ◽  
Management Strategies ◽  
Isotope Analysis ◽  
Primary Source ◽  
Habitat Characteristics ◽  
Conservation Actions ◽  
Isotope Mixing Models ◽  
North Western

The lack of integrated measures for assessing the feeding ecology of seahorses may restrict the effectiveness of conservation actions on wild populations of worldwide threatened seahorse species. Identifying dietary sources will allow researchers to determine their degree of vulnerability to environmental changes, redefine their conservation status and apply appropriate management strategies. The resource use of the seahorse Hippocampus guttulatus inhabiting coastal waters of Galicia (north-western Iberian Peninsula) was assessed for three populations and 2 years using stable isotope mixing models. The Bayesian mixing model (MixSIAR) estimated the relative contributions of the dietary sources to the seahorse diet and revealed that Caprellidea were the primary source, followed by Gammaridea and Caridea. Mysidae and Annelida represented the less dominant prey. This prey preference can be explained by the foraging behaviour of seahorses. Different contributions of Gammaridea and Caridea to the diet were found among sites, indicating different habitat characteristics and hence different habitat use by seahorses within each site. In addition, differences were encountered among sexes. Caprellidea was the dominant prey for females, whereas Gammaridea was the dominant prey for males. The findings of the present study will contribute to the knowledge of feeding patterns of H. guttulatus, providing relevant data for conservation of this endangered species.

scholarly journals Impact of climate and moonlight on a venomous mammal, the Javan slow loris (Nycticebus javanicus Geoffroy, 1812)

2014 ◽  
Vol 83 (4) ◽  
pp. 217-225 ◽  
Author(s):  
Eva Johanna Rode-Margono ◽  
K. Anne-Isola Nekaris
Keyword(s):  
Climatic Factors ◽  
Prey Availability ◽  
Interactive Effect ◽  
Weather Conditions ◽  
Climatic Conditions ◽  
Activity Level ◽  
Environmental Data ◽  
Foraging Efficiency ◽  
Slow Loris ◽  
Reduce Activity

Predation pressure, food availability, and activity may be affected by level of moonlight and climatic conditions. While many nocturnal mammals reduce activity at high lunar illumination to avoid predators (lunarphobia), most visually-oriented nocturnal primates and birds increase activity in bright nights (lunarphilia) to improve foraging efficiency. Similarly, weather conditions may influence activity level and foraging ability. We examined the response of Javan slow lorises (Nycticebus javanicus Geoffroy, 1812) to moonlight and temperature. We radio-tracked 12 animals in West Java, Indonesia, over 1.5 years, resulting in over 600 hours direct observations. We collected behavioural and environmental data including lunar illumination, number of human observers, and climatic factors, and 185 camera trap nights on potential predators. Nycticebus javanicus reduced active behaviours in bright nights. Although this might be interpreted as a predator avoidance strategy, animals remained active when more observers were present. We did not find the same effect of lunar illumination on two potential predators. We detected an interactive effect of minimum temperature and moonlight, e.g. in bright nights slow lorises only reduce activity when it is cold. Slow lorises also were more active in higher humidity and when it was cloudy, whereas potential predators were equally active across conditions. As slow lorises are well-adapted to avoid/defend predators by crypsis, mimicry and the possession of venom, we argue that lunarphobia may be due to prey availability. In bright nights that are cold, the combined effects of high luminosity and low temperature favour reduced activity and even torpor. We conclude that Javan slow lorises are lunarphobic – just as the majority of mammals.

scholarly journals Foraging segregation of two congeneric diving seabird species breeding on St. George Island, Bering Sea

2016 ◽  
Vol 13 (8) ◽  
pp. 2579-2591 ◽  
Author(s):  
Nobuo Kokubun ◽  
Takashi Yamamoto ◽  
Nobuhiko Sato ◽  
Yutaka Watanuki ◽  
Alexis Will ◽  
...  
Keyword(s):  
Bering Sea ◽  
Environmental Changes ◽  
Foraging Ecology ◽  
Stress Hormones ◽  
Food Resource ◽  
Dive Depth ◽  
Bottom Phase ◽  
Seabird Species ◽  
Top Predators ◽  
The Bering Sea

Abstract. Subarctic environmental changes are expected to affect the foraging ecology of marine top predators, but the response to such changes may vary among species if they use food resources differently. We examined the characteristics of foraging behavior of two sympatric congeneric diving seabird: common (Uria aalge: hereafter COMUs) and thick-billed (U. lomvia: hereafter TBMUs) murres breeding on St. George Island, located in the seasonal sea-ice region of the Bering Sea. We investigated their foraging trip and flight durations, diel patterns of dive depth, and underwater wing strokes, along with wing morphology and blood stable isotope signatures and stress hormones. Acceleration–temperature–depth loggers were attached to chick-guarding birds, and data were obtained from 7 COMUs and 12 TBMUs. Both species showed similar mean trip duration (13.2 h for COMUs and 10.5 h for TBMUs) and similar diurnal patterns of diving (frequent dives to various depths in the daytime and less frequent dives to shallow depths in the nighttime). During the daytime, the dive depths of COMUs had two peaks in shallow (18.1 m) and deep (74.2 m) depths, while those of TBMUs were 20.2 m and 59.7 m. COMUs showed more frequent wing strokes during the bottom phase of dives (1.90 s−1) than TBMUs (1.66 s−1). Fish occurred more frequently in the bill loads of COMUs (85 %) than those of TBMUs (56 %). The δ15N value of blood was significantly higher in COMUs (14.5 ‰) than in TBMUs (13.1 ‰). The relatively small wing area (0.053 m2) of COMUs compared to TBMUs (0.067 m2) may facilitate their increased agility while foraging and allow them to capture more mobile prey such as larger fishes that inhabit deeper depths. These differences in food resource use may lead to the differential responses of the two murre species to marine environmental changes in the Bering Sea.

A test of optimal foraging and the effects of predator experience in the lizards Sceloporus jarrovii and Sceloporus virgatus

Behaviour ◽  
2010 ◽  
Vol 147 (8) ◽  
pp. 933-951 ◽  
Author(s):  
Keyword(s):  
Success Rate ◽  
Prey Capture ◽  
Prey Availability ◽  
Search Time ◽  
Handling Time ◽  
Foraging Efficiency ◽  
Prey Choice ◽  
Foraging Experience ◽  
Time Optimality ◽  
Sceloporus Virgatus

AbstractForaging efficiency of predators can be evaluated by using optimality or profitability models which incorporate prey choice, handling time and pursuit or search time. Optimality of a diet could vary based on the age, sex, size, predation risk, or foraging experience of the predator. This study tested the effects of a predator's age and foraging experience by observing prey capture attempts and success rate, and by calculating diet profitability for adult and neonate Sceloporus jarrovii and adult Sceloporus virgatus. Prey availability was assessed in order to determine prey preference and profitability. Neonates showed an increased number of prey capture attempts, but success rate was similar for neonates and adults of both species. Total diet profitability of neonates was lower than adults of either species, which could be a result of poor prey choice or gape limitation (although body size showed no direct effect). Overall, the diets of all three groups were less profitable than would be expected based on the types of prey in the environment, although this is likely due to low availability (from the lizard's perspective) of highly profitable items. Lizards seem to be eating prey items in the same proportion as they are found in the environment.

scholarly journals Are snake populations in widespread decline?

2010 ◽  
Vol 6 (6) ◽  
pp. 777-780 ◽  
Author(s):  
C. J. Reading ◽  
L. M. Luiselli ◽  
G. C. Akani ◽  
X. Bonnet ◽  
G. Amori ◽  
...  
Keyword(s):  
Global Climate Change ◽  
Prey Availability ◽  
Global Climate ◽  
Population Declines ◽  
Common Cause ◽  
Top Predators ◽  
Short Period ◽  
The Uk ◽  
Long Term Studies

Long-term studies have revealed population declines in fishes, amphibians, reptiles, birds and mammals. In birds, and particularly amphibians, these declines are a global phenomenon whose causes are often unclear. Among reptiles, snakes are top predators and therefore a decline in their numbers may have serious consequences for the functioning of many ecosystems. Our results show that, of 17 snake populations (eight species) from the UK, France, Italy, Nigeria and Australia, 11 have declined sharply over the same relatively short period of time with five remaining stable and one showing signs of a marginal increase. Although the causes of these declines are currently unknown, we suspect that they are multi-faceted (such as habitat quality deterioration, prey availability), and with a common cause, e.g. global climate change, at their root.

scholarly journals Novel feeding and mating behaviors of a population of nautiluses, Nautilus belauensis, in Palau

2019 ◽  
Author(s):  
Gregory J. Barord ◽  
Rebecca L. Swanson ◽  
Peter D. Ward
Keyword(s):  
Behavioral Plasticity ◽  
Environmental Changes ◽  
Prey Availability ◽  
Habitat Type ◽  
Conservation Practices ◽  
Behavioral Differences ◽  
Behavioral Observations ◽  
Mating Behaviors ◽  
Large Living ◽  
Abnormal Behaviors

AbstractThe nautiloid lineage extends back nearly 500 million years but today, is represented by only two living genera, Nautilus and Allonautilus. Behavioral observations of these living nautiluses have improved our understanding of how nautiloids, and ammonoids, behaved and interacted in their environment. These behaviors may also help to inform conservation practices. Here, we describe feeding and mating behaviors in wild nautiluses not reported from any other population. In Palau, Nautilus belauensis was observed actively preying on a large, living crab (Chaceon sp.) and performing courtship-like behaviors prior to mating. These behaviors occurred across multiple nights and from different nautiluses, suggesting that the behaviors are characteristic of at least a subset of the population, if not the entire population. Perhaps the behaviors exhibited by the Palauan nautiluses are an outlier and simply a localized characteristic of a far-removed population. Or, perhaps these apparent abnormal behaviors of Palauan nautiluses are what all nautiluses across the Indo-Pacific should be exhibiting. If the latter explanation is correct, we can start to address the potential causes of the behavioral differences, such as population size, habitat type, and prey availability. In either case, this apparent behavioral plasticity may have also been a reason that the nautiloid lineage has been able to survive throughout millions of years of environmental changes. Today, these behavioral observations could prove to be a valuable conservation tool to protect species and environments, especially in the deep-sea ecosystem the nautiluses inhabit.

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