Potential of prey size and type to affect foraging asymmetries in tiger salamander (Ambystoma tigrinum nebulosum) larvae

2003 ◽  
Vol 81 (10) ◽  
pp. 1726-1735 ◽  
Author(s):  
Eric B Johnson ◽  
Paulette Bierzychudek ◽  
Howard H Whiteman
Keyword(s):  
Size Structure ◽  
Prey Size ◽  
Interference Competition ◽  
Prey Type ◽  
Foraging Efficiency ◽  
Ambystoma Tigrinum ◽  
Tiger Salamander ◽  
Predator Population ◽  
Large Prey ◽  
Ambystoma Tigrinum Nebulosum

Although competitive interactions within predator populations are known to depend on their size structure, we understand less about how these interactions are influenced by prey characteristics. Most studies of such interactions for tiger salamander (Ambystoma tigrinum nebulosum) larvae have used small zooplankton prey. We investigate the potential of exploitation and interference competition to influence the success of tiger salamander larvae feeding on relatively large prey, mayfly and damselfly larvae. We measured salamander foraging efficiency for a range of salamander and prey sizes and observed aggression levels of salamanders of varying size housed together. Exploitative foraging efficiency (captures per attempts) increased with salamander size but was better predicted by relative prey size (prey size as a percentage of salamander snout–vent length) than by salamander size alone; it also depended significantly on prey type. Aggression (interference) levels were higher when prey were present, and larger salamanders were more aggressive than smaller ones but did not consume more mayfly prey. Our results suggest that investigating the environmental conditions, particularly the prey characteristics, that influence size-based competitive advantages will lead to a better understanding of predator population dynamics.

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 Predator-Prey in Tumor-Immune Interactions: A Wrong Model or Just an Incomplete One?

2021 ◽  
Vol 12 ◽  
Author(s):  
Irina Kareva ◽  
Kimberly A. Luddy ◽  
Cliona O’Farrelly ◽  
Robert A. Gatenby ◽  
Joel S. Brown
Keyword(s):  
Immune System ◽  
Immune Cell ◽  
Interference Competition ◽  
Prey Type ◽  
Cell Types ◽  
Cell Populations ◽  
Natural Food ◽  
Predator Population ◽  
Predator Prey ◽  
Predator Prey Models

Tumor-immune interactions are often framed as predator-prey. This imperfect analogy describes how immune cells (the predators) hunt and kill immunogenic tumor cells (the prey). It allows for evaluation of tumor cell populations that change over time during immunoediting and it also considers how the immune system changes in response to these alterations. However, two aspects of predator-prey type models are not typically observed in immuno-oncology. The first concerns the conversion of prey killed into predator biomass. In standard predator-prey models, the predator relies on the prey for nutrients, while in the tumor microenvironment the predator and prey compete for resources (e.g. glucose). The second concerns oscillatory dynamics. Standard predator-prey models can show a perpetual cycling in both prey and predator population sizes, while in oncology we see increases in tumor volume and decreases in infiltrating immune cell populations. Here we discuss the applicability of predator-prey models in the context of cancer immunology and evaluate possible causes for discrepancies. Key processes include “safety in numbers”, resource availability, time delays, interference competition, and immunoediting. Finally, we propose a way forward to reconcile differences between model predictions and empirical observations. The immune system is not just predator-prey. Like natural food webs, the immune-tumor community of cell types forms an immune-web of different and identifiable interactions.

Ontogenetic and seasonal variation in the diets of a Costa Rican leaf-litter herpetofauna

2006 ◽  
Vol 22 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Steven M. Whitfield ◽  
Maureen A. Donnelly
Keyword(s):  
Seasonal Variation ◽  
Size Structure ◽  
Prey Size ◽  
Prey Selection ◽  
Large Prey ◽  
Wet Season ◽  
Ontogenetic Shifts ◽  
Prey Preferences ◽  
Lowland Wet Forest ◽  
Stomach Volume

Ontogenetic and seasonal variation in diet was examined for 11 species of insectivorous forest-floor frogs and lizards from a lowland wet forest in north-eastern Costa Rica. Specimens were collected systematically over an entire seasonal cycle and represented individuals of all sizes. Individual prey items were removed from stomachs of preserved specimens, measured and identified. Ontogenetic shifts in prey size were pervasive. Ontogenetic shifts in prey composition were limited to four species; these were not the species with greatest range in body size, nor the species with the broadest diets. Small prey types (ants, mites, collembolans) decreased in representation and large prey types (roaches, orthopterans, millipedes) increased in importance over ontogeny; this could be because prey selection is based primarily on prey size or because of different prey preferences among age classes. There is little evidence for size-structure in this assemblage. There is no evidence that total availability of arthropod prey varies among seasons, but some evidence that preferred prey are less common in the wet season. Diet was similar between lizards and frogs. Lizards were more likely to have empty stomachs, but also greater stomach volume, than frogs; this indicates a difference in food-gathering strategies. Our study indicates strong similarity between frogs and lizards in diet despite enormous differences in physiology and behaviour.

Accuracy Assessment of Skeletochronology in the Arizona Tiger Salamander (Ambystoma Tigrinum Nebulosum)

Copeia ◽  
2007 ◽  
Vol 2007 (2) ◽  
pp. 471-477 ◽  
Author(s):  
Christopher J. Eden ◽  
Howard H. Whiteman ◽  
Leon Duobinis-Gray ◽  
Scott A. Wissinger
Keyword(s):  
Accuracy Assessment ◽  
Ambystoma Tigrinum ◽  
Tiger Salamander ◽  
Ambystoma Tigrinum Nebulosum
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