scholarly journals Notes on the predation of an assassin bug by a spider in a Neotropical cave

2020 ◽  
Vol 33 ◽  
pp. 17-22
Author(s):  
Leopoldo Ferreira de Oliveira Bernardi ◽  
Vinícius da Fontoura Sperandei ◽  
Lívia Dorneles Audino ◽  
Carlos Henrique Sena ◽  
Jessica Aline Alves
Keyword(s):  
Population Dynamics ◽  
Intraguild Predation ◽  
Scientific Literature ◽  
Food Resources ◽  
Predation Event ◽  
Assassin Bug

Intraguild predation have rarely been documented in scientific literature, even though this type of interaction can affect population dynamics and competition. In this study we present an intraguild predation event that occurred at different times, but in the same cave, where we observed spiders of the species Enoploctenus cyclotorax preying on specimens of assassin bug Zelurus diasi. Inside the studied caves, food resources are scarce and populations can be fairly small in size. It is possible, therefore, that these events are the result of ecological pressures imposed by the hypogean environment.

More Modules

2011 ◽  
Author(s):  
Kevin S. McCann
Keyword(s):  
Population Dynamics ◽  
Food Webs ◽  
Empirical Evidence ◽  
Intraguild Predation ◽  
Weak Interactions ◽  
Apparent Competition ◽  
Trade Offs ◽  
Variable Population ◽  
The Stability

This chapter considers four-species modules and the role of generalism (effectively a three-species module with a consumer feeding on two resources). It first examines how generalists affect the dynamics of food webs by focusing on a set of modules that contrast generalist consumer dynamics relative to the specialist case. It then discusses organismal trade-offs that play a role in governing the diamond food web module and the intraguild predation module, arguing that such tradeoffs influence the flux of matter, the organization of interaction strengths, and ultimately the stability of communities. The chapter also reviews empirical evidence showing that apparent competition and the diamond module with and without intraguild predation are ubiquitous, and that weak interactions in simple modules seem to promote less variable population dynamics.

Population dynamics of Newfoundland beaver

1977 ◽  
Vol 55 (9) ◽  
pp. 1480-1492 ◽  
Author(s):  
Arthur T. Bergerud ◽  
Donald R. Miller
Keyword(s):  
Population Dynamics ◽  
Mortality Rate ◽  
Litter Size ◽  
Food Resources ◽  
Territorial Behaviour ◽  
Population Densities ◽  
Adult Females ◽  
Annual Mortality

The demography of beaver was studied in Newfoundland from 1956 to 1965. Population densities were low and seldom exceeded one colony per 2.6 km2 (1 mi2). About 80% of the adult females were fertile and the number of young per litter averaged 2.7. The annual mortality rate of beavers was about 30% in southeastern Newfoundland. A more detailed study was made of a population living in a 39-km2 (15-mi2) study area. This population had 20, 23, and 24 active colonies, 1958–1960. In 1961 it declined to 18 colonies. We removed the beavers in 1962. The replacement colonies, resulting initially from ingress, were 7 in 1962, 12 in 1963, 17 in 1964, and 15 in 1965. When the population was high in 1958–1960, the fertility of females was high (78%) but the litter size in 1960 appeared to be less than elsewhere. When the population declined in 1960–1961, productivity declined and some animals may have starved over winter. It was concluded that territorial behaviour spaces colonies, dispersing the population within the limits dictated by the availability of water and food resources. However, such a system did not prevent overutilization of food resources and decline of the population from reduced reproduction and increased mortality.

Thanatosis

2018 ◽  
Author(s):  
Graeme D. Ruxton ◽  
William L. Allen ◽  
Thomas N. Sherratt ◽  
Michael P. Speed
Keyword(s):  
Tonic Immobility ◽  
Scientific Literature ◽  
Animal Hypnosis ◽  
Perceived Need ◽  
Death Feigning ◽  
Predation Event ◽  
Long Time

When physically restrained, many animals adopt a relatively immobile state that can last after the constraint has been released. The lack of movement is suggested to inhibit further attack by the predator and reduce the perceived need of the predator to continue to attack or constrain the prey. This phenomenon has been variously called death feigning, animal hypnosis, tonic immobility, and playing dead. However, we will use the term that the scientific literature seems to be coalescing around: thanatosis. Thanatosis is distinct from immobility used to reduce the risk of detection or tracking by a predator, since it acts later in the sequence of a predation event (generally after the prey has been detected and contacted by the predator). Although some instances of thanatosis are strongly suggestive of mimicry of death, some are less so, and there is potential for thanatosis to offer protection from predators through other mechanisms than feigning death. However, except for some very specialist situations considered briefly here, the function of thanatosis does appear to be employed as a means of protection from predators. Thanatosis is widespread taxonomically, and has been well known for a long time, but only recently has it received purpose-designed study.

scholarly journals Parasites that change predator or prey behaviour can have keystone effects on community composition

2014 ◽  
Vol 10 (1) ◽  
pp. 20130879 ◽  
Author(s):  
Melanie J. Hatcher ◽  
Jaimie T. A. Dick ◽  
Alison M. Dunn
Keyword(s):  
Population Dynamics ◽  
Community Structure ◽  
Mathematical Models ◽  
Biological Invasions ◽  
Intraguild Predation ◽  
Host Species ◽  
Indirect Interactions ◽  
Ecological Impacts ◽  
Mediated Effects ◽  
Population Interactions

Parasites play pivotal roles in structuring communities, often via indirect interactions with non-host species. These effects can be density-mediated (through mortality) or trait-mediated (behavioural, physiological and developmental), and may be crucial to population interactions, including biological invasions. For instance, parasitism can alter intraguild predation (IGP) between native and invasive crustaceans, reversing invasion outcomes. Here, we use mathematical models to examine how parasite-induced trait changes influence the population dynamics of hosts that interact via IGP. We show that trait-mediated indirect interactions impart keystone effects, promoting or inhibiting host coexistence. Parasites can thus have strong ecological impacts, even if they have negligible virulence, underscoring the need to consider trait-mediated effects when predicting effects of parasites on community structure in general and biological invasions in particular.

Models of the effects of marine-derived nutrients on salmon (Oncorhynchus spp.) population dynamics

2010 ◽  
Vol 67 (1) ◽  
pp. 5-15 ◽  
Author(s):  
Milo D. Adkison
Keyword(s):  
Population Dynamics ◽  
Mathematical Models ◽  
Fresh Water ◽  
Growth Rates ◽  
Pacific Salmon ◽  
Food Resources ◽  
Juvenile Salmon ◽  
Management Implications ◽  
Freshwater Habitats ◽  
Stock Recruitment

Pacific salmon ( Oncorhynchus spp.) populations transfer large quantities of nutrients from their marine to their freshwater habitats. These nutrients have been shown to affect salmon populations in fresh water, including increasing basal food resources and elevating juvenile salmon growth rates and condition. The broader effects on recruitment and commercial harvests, however, are not clear. I developed and explored mathematical models of the effects of these nutrients on stock–recruitment relationships and used these models to investigate management implications. Populations strongly dependent on nutrients had lower sustained yields than those not dependent on nutrients. When nutrients strongly affected the stock–recruitment relationship, relatively low harvest rates and high escapement levels were necessary to maintain the population’s productivity. However, in some scenarios, the highest yields were obtained from small, nutrient-depleted populations. In other scenarios, the nutrient dependence had few management implications.

The influence of food resources on population dynamics in Columbian ground squirrels

1985 ◽  
Vol 63 (9) ◽  
pp. 2095-2104 ◽  
Author(s):  
F. Stephen Dobson ◽  
Julia D. Kjelgaard
Keyword(s):  
Population Dynamics ◽  
Environmental Factors ◽  
Population Size ◽  
Ground Squirrel ◽  
Food Resources ◽  
Ground Squirrels ◽  
Limiting Factors ◽  
Supplemental Food ◽  
Survival And Reproduction ◽  
Population Processes

Determining the environmental factors that limit the size of populations and examining the influence of environmental factors on population processes (immigration, emigration, survival, and reproduction) are fundamental problems for population ecologists. We conducted an experimental study of population dynamics in the Columbian ground squirrel, Spermophilus columbianus, from 1981 to 1983, in southwestern Alberta, Canada. We supplemented the food resources of two local populations of ground squirrels at different elevations and also monitored two reference (unsupplemented) populations. Population size increased by about 85% annually and population biomass increased by about 94% annually where supplemental food was provided. Reference populations varied in numbers and biomass by less than 40% annually. Because the increase in size of supplemented populations was dramatic, we concluded that food resources probably limited the size of the ground squirrel populations before we began the experiments and that other possible limiting factors were insufficient to check the increases stimulated by supplemental food. Several population processes were influenced by the increased food resources. Immigration of all age-classes was higher to supplemented than to reference populations and favored females. Survival of resident young was higher in supplemented than in reference populations. Reproduction was greatly increased in supplemented populations compared with reference populations, with surviving young residents of 1982 making the greatest contribution to increases in population size. The results were generally similar in the two replicates of the experiment. Competition for food resources appeared to be strongest among yearling and adult females and among young of both sexes.

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