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139 results for “predator size”

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dryad36/100

Data from: Nest predation risk explains variation in avian clutch size

Questions about the ecological drivers of, and mechanistic constraints on, productivity have driven research on life history evolution for decades. Resource availability and offspring mortality are considered among the two most important influences on the number of offspring per reproductive attempt. We used a factorial experimental design to manipulate food abundance and perceived offspring predation risk in a wild avian population (red-faced warblers; Cardellina rubrifrons) to identify the mechanistic cause of variation in avian clutch size. Additionally, we tested whether female quality helped explain the extant variation in clutch size. We found no support for the Food Limitation or Female Quality Hypotheses, but we did find support for both predictions of the Nest Predation Risk Hypothesis. Females that experienced an experimentally heightened perception of offspring predation risk responded by laying a smaller clutch than females in the control group. Additionally, predation rates at artificial nests were highest where red-faced warbler clutch size was smallest (at high elevations). Life history theory predicts that an individual should invest less in reproduction when high nest predation risk reduces the likely benefit from that nesting attempt, and indeed we found that birds exhibit phenotypic plasticity in clutch size by laying fewer eggs in response to increasing nest predation risk.

opencc-zeroDec 2016View details →

dryad36/100

No impact of biocontrol agent's predation cues on development time or size of surviving Aedes albopictus under optimal nutritional availability

Cyclopoid copepods have been applied successfully to limit populations of highly invasive Aedes albopictus mosquitoes that can transmit diseases of public health importance. However, there is concern that changes in certain mosquito traits, induced by exposure to copepod predation, might increase the risk of disease transmission. In this study, third instar Ae. albopictus larvae, hereafter referred to as "focal individuals", were exposed to Megacyclops viridis predator cues associated with both consumption of newly-hatched mosquito larvae and attacks on focal individuals. The number of newly-hatched larvae surrounding each focal larva was held constant to control for density effects on size, and the focal individual's day of pupation and wing length were recorded for each replicate. Exposing late instar Ae. albopictus to predation decreased their chances of surviving to adulthood, and three focal larvae that died in the predator treatment showed signs of melanization, indicative of wounding. Among surviving focal Ae. albopictus, no significant difference in either pupation day or wing length was observed due to copepod predation. The absence of a significant sublethal impact from M. viridis copepod predation on surviving later-stage larvae in this analysis supports the use of M. viridis as a biocontrol agent against Ae. albopictus.

opencc-zeroFeb 2022View details →

zenodo36/100

Data for 'Warming and predation risk only weakly shape size-mediated priority effects in a cannibalistic damselfly'

In a laboratory experiment, we studied effects of warming (low and high temperature) and predation risk (presence and absence of predator cues of perch) on SMPE in life history and physiological traits in the cannibalistic damselfly Ischnura elegans. We induced SMPE by manipulating hatching dates, thereby creating four groups: non-mixed phenology early (E) and late (L) hatchlings, and mixed phenology early (E+L) and late (L+E) hatchlings. This data set includes: <ul> <li>hatch date</li> <li>emergence date</li> <li>survival until emergence and emergence success data</li> <li>mass of adult insects</li> <li>development time (from hatching to emergence, in days)</li> <li>growth rate (mass of adult insect/development time in days)</li> <li>protein content (μg of protein/μl of prepared homogenate)</li> <li>fat content (μg of fat/μl of prepared homogenate)</li> <li>phenoloxidase activity (PO, value of activity curve slope)</li> <li>PO activity/protein (value of activity curve slope/(μg of protein/μl of prepared homogenate)</li> </ul>

opencc-by-4.0Jul 2022View details →

dryad36/100

Data for the article entitled: Linking sexual size dimorphism to trophic niche partitioning in a generalist predator

Sexual size dimorphism is a common phenomenon in mammals, and researchers have been trying to demonstrate the evolutionary causes leading to sexual dimorphism. Two main hypotheses emerged: (i) the sexual selection hypothesis and (ii) the sexual competition hypothesis (also called resource partitioning hypothesis). Here, we attempted to link sexual dimorphism in fishers (Pekania pennanti (Erxleben, 1777)) with their fall diet using stable isotope profiling and body and skull measurements. We used the carcasses of 39 fishers which were caught in eastern Québec during fall 2014 by volunteer trappers as well as several potential prey items ranging from small rodents to cervids. We expected minimal niche overlap between sexes, as males should be able to exploit different prey species than females. We also expected to observe an effect of age class (adults vs. juveniles) on trophic niche. As expected, we found great evidence of sexual dimorphism in both body mass and skull measurements: males were heavier and longer than females and had a larger zygomatic and intracanine width and a longer skull. While proportions of prey in diet according to sex and age did not vary greatly, we found some evidence of niche partitioning using Layman's metrics. Indeed, females tended to have a less diversified and more similar diet compared to one another, whereas males showed more diversified and contrasted diets. Despite our limited sample size, our findings provide partial support to the sexual competition hypothesis, as the difference in body and skull size based on sex could have evolved to lessen intraspecific competition in fishers.

opencc-zeroAug 2022View details →

dryad36/100

Finotypic plasticity: Predator-induced plasticity in fin size, darkness, and display behaviour in a teleost fish

Fish fins are remarkable devices of propulsion. Fin morphology is intimately linked to locomotor performance, and hence to behaviours that influence fitness, such as foraging and predator avoidance. This foreshadows a connection between fin morphology and variation in predation risk. Yet, whether prey can adjust fin morphology according to changes in perceived risk within their lifetime (a.k.a. predator-induced plasticity) remains elusive. Here, we quantify the structural size of five focal fins in crucian carp (Carassius carassius) following controlled manipulations to perceived predation risk (presence/absence of pike Esox lucius). We also assess if crucian carp respond to increased predation risk by shifts in dorsal fin colouration, and test for differences in how fish actively use their dorsal fins by quantifying the area of the fin displayed in behavioural trials. We find that crucian carp show phenotypic plasticity with regard to fin size as predator-exposed fish consistently have larger fins. Individuals exposed to perceived predation risk also increased dorsal fin darkness and actively displayed a larger area of the fin to potential predators. Our result thus provides compelling evidence for predator-induced fin enlargement, which should result in enhanced escape swimming performance. Moreover, fin-size plasticity may evolve synergistically with fin colouration and display behaviour, and we suggest that the adaptive value of this synergy is to enhance the silhouette of deep-bodied and hard-to-capture prey to deter gape-limited predators prior to an attack. Together, our results provide new perspectives on the role of predation risk for the development and evolution of fins.

opencc-zeroMay 2024View details →

zenodo36/100

Figure 4 in Predator exposure and size-related variation in web-building and web-decorating behavior in Argiope appensa

Figure 4. Relationship between web diameter and web decoration length on Rota and Guam.

opencc-by-4.0Dec 2013View details →

zenodo36/100

Figure 2 in Predator exposure and size-related variation in web-building and web-decorating behavior in Argiope appensa

Figure 2. Frequency distribution of spider body size categories in Rota and Guam.

opencc-by-4.0Dec 2013View details →

dryad36/100

Data from: Environmental correlates of molluscan predator-prey body size in the northern Gulf of Mexico

The Mississippi River watershed drains 40% of the continental United States, and the tremendous primary productivity in the adjacent north-central Gulf of Mexico has created one of the most extensive dead zones on Earth. In contrast, smaller watersheds deliver less nutrients to the northeastern Gulf, and consequently productivity is limited and hypoxia is uncommon. How has variation in primary productivity, oxygen availability, and sea surface temperature, affected coastal food webs? Here, we investigate environmental controls on the size of molluscan predators and prey in the northern Gulf of Mexico using Holocene death assemblages. Linear mixed models indicate that bivalve size and the frequency of drilling predation are affected by dissolved oxygen concentrations; drilling frequency declines with declining oxygen, whereas bivalve size increases. In contrast, sea surface temperature is positively associated with the size of molluscan predators and prey. Net primary productivity contributes relatively little to predator or prey size, and predator-to-prey size ratios do not vary consistently with environmental conditions across the northern Gulf. Larger bivalves in areas of oxygen limitation may be due to decreased predation pressure and consequently greater prey longevity. The larger size of bivalves and predatory gastropods in warmer waters may reflect enhanced growth under these conditions, provided dissolved oxygen concentrations exceed a minimum threshold. Holocene death assemblages can be used to test long-standing hypotheses regarding environmental controls on predator-prey body size distributions through geologic time and provide baselines for assessing the ongoing effects of anthropogenic eutrophication and warming on coastal food webs.

opencc-zeroJun 2023View details →

dryad36/100

Associated model data for: Size-selective predation effects on juvenile Chinook salmon cohort survival off Central California evaluated with an individual-based model

This dataset corresponds to the paper "Size-selective predation effects on juvenile Chinook salmon cohort survival off Central California evaluated with an individual-based model" which is in press at Fisheries Oceanography. The abstract for this paper is as follows: Variation in the recruitment of salmon is often found to be correlated with marine climate indices, but mechanisms behind environment-recruitment relationships remain unclear and correlations often break down over time. We used an ecosystem modeling approach to explore bottom-up and top-down mechanisms linking a variable environment to salmon recruitment variations. Our ecosystem model incorporates a regional ocean circulation sub-model for hydrodynamics, a nutrient-phytoplankton-zooplankton sub-model for producing planktonic prey fields, and an individual-based model (IBM) representing juvenile Chinook salmon (Oncorhynchus tshawytscha), combined with observations of foraging distributions and diet of a seabird predator. The salmon IBM consists of modules, including a juvenile salmon growth module based on temperature and salmon-prey availability, a behavior-based movement module, and a juvenile salmon predation mortality module based on juvenile salmon size distribution and predator-prey interaction probability. Seabird-salmon interactions depend on spatial overlap and juvenile salmon size, whereby salmon that grow past the size range of the prey distribution of the predator will escape predation. We used a 21-year historical simulation to explore interannual variability in juvenile Chinook salmon growth and predation-mediated survival under a range of ocean conditions for sized-based mortality scenarios. We based a series of increasingly complex predation scenarios on seabird observational data to explore variability in predation mortality on juvenile Chinook salmon. We initially included information about the predator spatial distribution, then added population size, and finally, the predator's diet percentage made up of juvenile salmon. Model agreement improves with added predator complexity, especially during periods when predator abundance is high. Overall, our model found that when the fraction of juvenile salmon in seabird diet increased relative to alternate prey (e.g., Northern anchovy Engraulis mordax, and juvenile rockfish Sebastes spp.), there was a concomitant decrease in salmon cohort survival during their first year at sea.

opencc-zeroSep 2023View details →

dryad36/100