The allometry of cannibalism in piscivorous fishes

2003 ◽  
Vol 60 (5) ◽  
pp. 594-602 ◽  
Author(s):  
Francis Juanes
Keyword(s):  
Upper Bound ◽  
Prey Size ◽  
Trophic Niche ◽  
Large Prey ◽  
Predator Species ◽  
Size Dependent ◽  
Predator Size ◽  
Large Databases ◽  
Widespread Phenomenon ◽  
Large Predators

Cannibalism is a widespread phenomenon that can have strong population and community effects. In this study, I compare the prey size – predator size relationships of diets with and without cannibalized prey for four piscivorous species and five populations that are commonly cannibalistic and where large databases exist. I then examine the resultant trophic niche breadths (range of relative prey size consumed) to quantify whether inclusion of cannibalized prey in the diet slows down the decline in trophic niche breadth that many large predators exhibit as they grow. When comparing diets including cannibalized prey with those without, consistent differences were found among all predator species. In all cases, the slope of the upper bound of the predator size – prey size scatters was larger for cannibal predators compared with noncannibals, suggesting selectivity for larger cannibal prey, which may be driven by higher rates of size-dependent capture success with familiar prey. The slopes of the upper bounds of the cannibal relative prey size vs. predator size scatter also tended to be larger than the upper-bound slopes for diets without conspecific prey. Finally, for all species, mean trophic breadth of diets including cannibalized prey were larger than those not including cannibal prey, suggesting that relatively large prey sizes may always be available for cannibals.

Do snakes exhibit shifts in feeding ecology associated with the presence or absence of potential competitors? A case study from tropical Africa

2003 ◽  
Vol 81 (2) ◽  
pp. 228-236 ◽  
Author(s):  
Luca Luiselli
Keyword(s):  
Feeding Ecology ◽  
Prey Size ◽  
Prey Type ◽  
Swamp Forest ◽  
Southeastern Nigeria ◽  
Predator Species ◽  
Predatory Behaviour ◽  
Ecological Requirements ◽  
Predator Size ◽  
Potential Competitor

Two species of rain-forest snakes, the colubrids Natriciteres fuliginoides and Natriciteres variegata, are potential competitors, because they attain, on average, the same body size (20–30 cm long), have similar habits and ecological requirements (they are both diurnal and nocturnal, often semi-aquatic), and have similar dietary spectra ( including both small vertebrates and invertebrates). I studied prey type and predator size – prey size relationships of these snakes in four swamp-forest areas of southeastern Nigeria (West Africa): only N. fuliginoides was found in two of these areas, whereas both species were common in the other two areas. The feeding ecology of N. fuliginoides shifted greatly in the presence of its potential competitor, N. variegata, in terms of prey-type preferences and predatory behaviour as well as in terms of predator size – prey size relationships. In particular, the effects of the potential competitor on the feeding ecology of N. fuliginoides were (i) a shift toward eating many invertebrates from a diet based on many small vertebrates, (ii) a shift toward eating many terrestrial organisms from a diet based on many aquatic organisms, and (iii) a shift in mean prey size for females toward relatively larger prey from a diet based on smaller prey. The resulting effect was a clear partitioning of food resources between the two predator species in both the areas where they are sympatric, whereas N. fuliginoides had a wider dietary spectrum (covering that of the two species together) in the areas where its competitor is not found. The role of intraspecific competition seems less strong, as no apparent resource partitioning in prey type or prey size was observed between males and females of either species or in any study area. However, mean prey size was significantly greater for females than for males of both species and in all study areas, but depended on the significant reverse sexual size dimorphism observed in both species.

scholarly journals Protection of large predators in a marine reserve alters size-dependent prey mortality

2017 ◽  
Vol 284 (1847) ◽  
pp. 20161936 ◽  
Author(s):  
Rebecca L. Selden ◽  
Steven D. Gaines ◽  
Scott L. Hamilton ◽  
Robert R. Warner
Keyword(s):  
Size Structure ◽  
Sea Urchins ◽  
Marine Reserves ◽  
Marine Reserve ◽  
Mortality Rates ◽  
Kelp Forests ◽  
Size Dependent ◽  
Predator Size ◽  
Top Predators ◽  
Large Predators

Where predator–prey interactions are size-dependent, reductions in predator size owing to fishing has the potential to disrupt the ecological role of top predators in marine ecosystems. In southern California kelp forests, we investigated the size-dependence of the interaction between herbivorous sea urchins and one of their predators, California sheephead ( Semicossyphus pulcher ). Empirical tests examined how differences in predator size structure between reserve and fished areas affected size-specific urchin mortality. Sites inside marine reserves had greater sheephead size and biomass, while empirical feeding trials indicated that larger sheephead were required to successfully consume urchins of increasing test diameter. Evaluations of the selectivity of sheephead for two urchin species indicated that shorter-spined purple urchins were attacked more frequently and successfully than longer-spined red urchins of the same size class, particularly at the largest test diameters. As a result of these size-specific interactions and the higher biomass of large sheephead inside reserves, urchin mortality rates were three times higher inside the reserve for both species. In addition, urchin mortality rates decreased with urchin size, and very few large urchins were successfully consumed in fished areas. The truncation of sheephead size structure that commonly occurs owing to fishing will probably result in reductions in urchin mortality, which may reduce the resilience of kelp beds to urchin barren formation. By contrast, the recovery of predator size structure in marine reserves may restore this resilience, but may be delayed until fish grow to sizes capable of consuming larger urchins.

scholarly journals Size-dependent locomotory performance creates a behaviorally mediated prey size refuge in the marine snail Olivella semistriata: a study in the natural habitat

2019 ◽  
Vol 66 (1) ◽  
pp. 57-62
Author(s):  
Callie A Veelenturf ◽  
Winfried S Peters
Keyword(s):  
Size Dependence ◽  
Prey Size ◽  
Natural Habitat ◽  
Individual Performance ◽  
Large Prey ◽  
Natural Habitats ◽  
Size Dependent ◽  
Locomotory Performance ◽  
Causal Sequence ◽  
Size Refuge

Abstract The effects of the variability of individual prey locomotory performance on the vulnerability to predation are poorly understood, partly because individual performance is difficult to determine in natural habitats. To gain insights into the role(s) of individual variation in predatory relationships, we study a convenient model system, the neotropical sandy beach gastropod Olivella semistriata and its main predator, the carnivorous snail Agaronia propatula. The largest size class of O. semistriata is known to be missing from A. propatula’s spectrum of subdued prey, although the predator regularly captures much larger individuals of other taxa. To resolve this conundrum, we analyzed predation attempts in the wild. While A. propatula attacked O. semistriata of all sizes, large prey specimens usually escaped by ‘sculling’, an accelerated, stepping mode of locomotion. Olivella semistriata performed sculling locomotion regardless of size, but sculling velocities determined in the natural environment increased strongly with size. Thus, growth in size as such does not establish a prey size refuge in which O. semistriata is safe from predation. Rather, a behaviorally mediated size refuge is created through the size-dependence of sculling performance. Taken together, this work presents a rare quantitative characterization in the natural habitat of the causal sequence from the size-dependence of individual performance, to the prey size-dependent outcome of predation attempts, to the size bias in the predator’s prey spectrum.

scholarly journals Intraspecific variation in body size does not alter the effects of mesopredators on prey

2016 ◽  
Vol 3 (12) ◽  
pp. 160414 ◽  
Author(s):  
Austin J. Gallagher ◽  
Simon J. Brandl ◽  
Adrian C. Stier
Keyword(s):  
Body Size ◽  
Size Structure ◽  
Independent Effect ◽  
Marine Food Webs ◽  
Size Dependent ◽  
Predator Attack ◽  
Predator Size ◽  
Experimental Trials ◽  
Large Predators

As humans continue to alter the species composition and size structure of marine food webs, it is critical to understand size-dependent effects of predators on prey. Yet, how shifts in predator body size mediate the effect of predators is understudied in tropical marine ecosystems, where anthropogenic harvest has indirectly increased the density and size of small-bodied predators. Here, we combine field surveys and a laboratory feeding experiment in coral reef fish communities to show that small and large predators of the same species can have similar effects. Specifically, surveys show that the presence of a small predator ( Paracirrhites arcatus ) was correlated with lower chances of prey fish presence, but these correlations were independent of predator size. Experimental trials corroborated the size-independent effect of the predator; attack rates were indistinguishable between small and large predators, suggesting relatively even effects of hawkfish in various size classes on the same type of prey. Our results indicate that the effects of small predators on coral reefs can be size-independent, suggesting that variation in predator size-structure alone may not always affect the functional role of these predators.

Trophic position scales positively with body size within but not among four species of rocky reef predators

2020 ◽  
Vol 640 ◽  
pp. 189-200 ◽  
Author(s):  
AM Olson ◽  
A Frid ◽  
JBQ dos Santos ◽  
F Juanes
Keyword(s):  
Body Size ◽  
Trophic Position ◽  
Stomach Contents ◽  
Rocky Reef ◽  
Morphometric Traits ◽  
Predator Species ◽  
Predatory Fishes ◽  
Average Size ◽  
Interspecific Comparisons ◽  
Large Predators

Intra- and interspecifically, larger-bodied predators generally occupy higher trophic positions (TPs). With widespread declines in large predators, there is a need to understand their size-based trophic roles to predict ecosystem-level responses. In British Columbia, Canada, we examined size-based trophic interactions between predatory fishes—3 rockfish species (genus Sebastes) and lingcod Ophiodon elongatus—and their prey, converting predator δ15N signatures to TP and analyzing stomach contents. Intraspecifically, TP scaled positively with predator length and gape width, but the rates of change varied by species. Interspecifically, TP did not scale positively with the observed mean sizes or known maximum sizes of species. Lingcod TP was lower than that of yelloweye and quillback rockfishes, which were 51 and 37%, respectively, smaller than lingcod. Yellowtail rockfish had the smallest average size, yet their mean TP did not differ significantly from that of lingcod. Neither species differences in some morphometric traits known to influence body size-TP relationships nor phylogenetic history explained these results. Most prey consumed were <20% of the predator’s size, which might partially explain the lack of a size-based trophic hierarchy among species. Currently, large size classes of rockfishes are being lost due to fisheries and perhaps climate-driven changes. Our findings on intraspecific size-TP relationships indicate that fishery removals of large individuals may diminish trophic structures. Interspecific comparisons of TP suggest that, along with size, species remain an important factor in understanding trophic dynamics. In addition, smaller-bodied predator species may have significant ecological roles to be considered in ecosystem-based fisheries management.

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.

scholarly journals The food web in a subterranean ecosystem is driven by intraguild predation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrea Parimuchová ◽  
Lenka Petráková Dušátková ◽  
Ľubomír Kováč ◽  
Táňa Macháčková ◽  
Ondřej Slabý ◽  
...  
Keyword(s):  
Food Web ◽  
Trophic Interactions ◽  
Intraguild Predation ◽  
Linear Models ◽  
Niche Overlap ◽  
Trophic Niche ◽  
High Availability ◽  
Large Prey ◽  
Arthropod Predators ◽  
Body Sizes

AbstractTrophic interactions of cave arthropods have been understudied. We used molecular methods (NGS) to decipher the food web in the subterranean ecosystem of the Ardovská Cave (Western Carpathians, Slovakia). We collected five arthropod predators of the species Parasitus loricatus (gamasid mites), Eukoenenia spelaea (palpigrades), Quedius mesomelinus (beetles), and Porrhomma profundum and Centromerus cavernarum (both spiders) and prey belonging to several orders. Various arthropod orders were exploited as prey, and trophic interactions differed among the predators. Linear models were used to compare absolute and relative prey body sizes among the predators. Quedius exploited relatively small prey, while Eukoenenia and Parasitus fed on relatively large prey. Exploitation of eggs or cadavers is discussed. In contrast to previous studies, Eukoenenia was found to be carnivorous. A high proportion of intraguild predation was found in all predators. Intraspecific consumption (most likely cannibalism) was detected only in mites and beetles. Using Pianka’s index, the highest trophic niche overlaps were found between Porrhomma and Parasitus and between Centromerus and Eukoenenia, while the lowest niche overlap was found between Parasitus and Quedius. Contrary to what we expected, the high availability of Diptera and Isopoda as a potential prey in the studied system was not corroborated. Our work demonstrates that intraguild diet plays an important role in predators occupying subterranean ecosystems.

scholarly journals Prey-predator size-dependent functional response: derivation and rescaling to the real world

2004 ◽  
Vol 73 (2) ◽  
pp. 239-252 ◽  
Author(s):  
Albashir A. Aljetlawi ◽  
Erik Sparrevik ◽  
Kjell Leonardsson
Keyword(s):  
Functional Response ◽  
Real World ◽  
The Real ◽  
Size Dependent ◽  
Predator Size

CHANGES IN PREY SIZE PREFERENCES DURING SUCCESSIVE STAGES OF FORAGING IN THE MEDITERRANEAN WATER SHREW NEOMYS ANOMALUS

Behaviour ◽  
1999 ◽  
Vol 136 (3) ◽  
pp. 345-365 ◽  
Author(s):  
Leszek Rychlik
Keyword(s):  
Predation Risk ◽  
Prey Size ◽  
Large Prey ◽  
Habitat Conditions ◽  
Food Hoarding ◽  
Food Quantity ◽  
Competition For Food ◽  
Mediterranean Water ◽  
Selection Of ◽  
Food Portions

AbstractPrey size preferences in successive stages of foraging of Mediterranean water shrews Neomys anomalus Cabrera, 1907 were investigated in a terrarium. Seven shrews were tested individually in five experimental variants (simulating different habitat conditions) totally for 504 hours. Water shrews displayed partial preferences for prey size but they were selective from the very beginning of the foraging period. When searching for food, N. anomalus preferred big food portions, abandoning significantly more small than big portions. This tendency was especially strong when few food portions were available on land and there were no natural structures in the terrarium. Selection of big portions was intensified probably by their easier detection. Shrews hoarded proportionally more big than small portions in the scattered hiding-places. This tendency was intensified by the presence of natural structures, dispersion of food and reduction of food quantity placed on land. Later, however, more small than big food portions were eaten, apparently because small portions were easier to manipulate. Scattered food hoarding and preference of large prey are proposed to be the strategy of N. anomalus to maximise the energy net gain and minimise the predation risk and competition for food.

Sign in / Sign up

Export Citation Format

Share Document