scholarly journals Effect of prey availability on growth-rate trajectories of an aquatic predator, the viperine snake Natrix maura

2014 ◽  
Author(s):  
Aikaterini Filippakopoulou ◽  
Xavier Santos ◽  
Mónica Feriche ◽  
Juan M. Pleguezuelos ◽  
Gustavo A. Llorente
Keyword(s):  
Growth Rate ◽  
Prey Availability ◽  
Natrix Maura

scholarly journals Body downsizing caused by non-consumptive social stress severely depresses population growth rate

2009 ◽  
Vol 277 (1683) ◽  
pp. 843-851 ◽  
Author(s):  
Eric Edeline ◽  
Thrond O. Haugen ◽  
Finn-Arne Weltzien ◽  
David Claessen ◽  
Ian J. Winfield ◽  
...  
Keyword(s):  
Growth Rate ◽  
Density Dependence ◽  
Social Stress ◽  
Prey Availability ◽  
Survival Rates ◽  
Population Modelling ◽  
Size Dependent ◽  
Rate Of Increase ◽  
Primary Driver ◽  
Leslie Matrices

Chronic social stress diverts energy away from growth, reproduction and immunity, and is thus a potential driver of population dynamics. However, the effects of social stress on demographic density dependence remain largely overlooked in ecological theory. Here we combine behavioural experiments, physiology and population modelling to show in a top predator (pike Esox lucius ) that social stress alone may be a primary driver of demographic density dependence. Doubling pike density in experimental ponds under controlled prey availability did not significantly change prey intake by pike (i.e. did not significantly change interference or exploitative competition), but induced a neuroendocrine stress response reflecting a size-dependent dominance hierarchy, depressed pike energetic status and lowered pike body growth rate by 23 per cent. Assuming fixed size-dependent survival and fecundity functions parameterized for the Windermere (UK) pike population, stress-induced smaller body size shifts age-specific survival rates and lowers age-specific fecundity, which in Leslie matrices projects into reduced population rate of increase ( λ ) by 37–56%. Our models also predict that social stress flattens elasticity profiles of λ to age-specific survival and fecundity, thus making population persistence more dependent on old individuals. Our results suggest that accounting for non-consumptive social stress from competitors and predators is necessary to accurately understand, predict and manage food-web dynamics.

Food availability induces geographic variation in reproductive timing of an aquatic oviparous snake (Natrix maura)

2005 ◽  
Vol 26 (2) ◽  
pp. 183-191 ◽  
Author(s):  
◽  
A. de Sostoa ◽  
◽  
◽  
◽  
...  
Keyword(s):  
Clutch Size ◽  
Food Availability ◽  
Prey Availability ◽  
Good Condition ◽  
Early Spring ◽  
Ebro Delta ◽  
Reproductive Timing ◽  
Mediterranean Populations ◽  
Water Snake ◽  
Natrix Maura

AbstractThe viperine snake Natrix maura is a common water snake, which forages on aquatic prey such as fish and frogs in Western Mediterranean water bodies. Female viperine snakes collected from three populations at the Iberian Peninsula during the vitellogenesis period were compared. Mean clutch size and range, as well as the slope of the regression between body size and clutch size, did not show differences between populations. In contrast, mean size of enlarged follicles of females collected in May from the Ebro Delta proved significantly smaller than those of females from the Matarranya River (50 km far) and the Granada Depression (500 km far). There were no differences in climatic conditions between areas. However, seasonal variation in food availability was significantly different in the Ebro Delta. In this area, the rice fields are dry in early spring as men control the water flow, and prey are not available. This energetic constraint induced female viperine snakes to adjust reproductive timing according to seasonal availability and to delay vitellogenesis for at least one month. By contrast, other Mediterranean populations exhibited a rather high prey availability from early spring (e.g. Matarranya River), females being in good condition in this season and consequently vitellogenesis starting earlier than in the Ebro Delta. This study illustrates a new case of reproductive plasticity in snakes.

Emergent Allee Effects through Biomass Overcompensation

2013 ◽  
Author(s):  
André M. de Roos ◽  
Lennart Persson
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Positive Feedback ◽  
Population Growth Rate ◽  
Allee Effect ◽  
Prey Availability ◽  
Population Level ◽  
Life History Stage ◽  
Predator Population ◽  
Allee Effects

This chapter discusses the emergence of a positive feedback between the density of predators and the availability of its food, mediated through biomass overcompensation in the prey life history stage that it forages on. This positive feedback between predation, prey availability, and thus predator population growth rate manifests itself at the population-level as an Allee effect for the predator: a predator population at low density will decline to extinction, whereas at high densities predators will manage to establish themselves in a community with prey. However, this positive relation between predator density and its population growth rate does not result from any positively density-dependent interactions among the predators themselves, which generally form the basis of an Allee effect. Instead, predators only interact with each other through exploitative competition for prey. The Allee effect emerges solely as a consequence of the demographic changes in the prey population, which are induced by the mortality that the predator imposes. For this reason this phenomenon is referred to as an “emergent Allee effect.”

Variation in the diet of the viperine snake Natrix maura in relation to prey availability

Ecography ◽  
2000 ◽  
Vol 23 (2) ◽  
pp. 185-192 ◽  
Author(s):  
Xavier Santos ◽  
Jacob Gonzalez-Solis ◽  
Gustavo A. Llorente
Keyword(s):  
Prey Availability ◽  
Natrix Maura

The threshold energy for atom displacement in fcc metals

1990 ◽  
Vol 48 (4) ◽  
pp. 530-531
Author(s):  
Wilfried Sigle ◽  
Matthias Hohenstein ◽  
Alfred Seeger
Keyword(s):  
Growth Rate ◽  
Elevated Temperatures ◽  
Threshold Energy ◽  
Dislocation Loops ◽  
Absolute Minimum ◽  
Voltage Electron ◽  
Atom Displacement ◽  
Electron Microscopes ◽  
Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

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