A term paper on PREDATION (original) (raw)
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Predation and Predator management
Predation and can be seen as a simple phenomenon of one animal killing and eating the other. But it is not the case since predation is very comprehensive due to processes involved, animal behavior, survival for the fittest, ecological balance and so on. Much will be explained in this thesis.
Predator Functional Responses: Discriminating between Handling and Digesting Prey
Ecological Monographs, 2002
We present a handy mechanistic functional response model that realistically incorporates handling (i.e., attacking and eating) and digesting prey. We briefly review current functional response theory and thereby demonstrate that such a model has been lacking so far. In our model, we treat digestion as a background process that does not prevent further foraging activities (i.e., searching and handling). Instead, we let the hunger level determine the probability that the predator searches for new prey. Additionally, our model takes into account time wasted through unsuccessful attacks. Since a main assumption of our model is that the predator's hunger is in a steady state, we term it the steady-state satiation (SSS) equation.
A predator’s functional response: Influence of prey species and size
Biological Control, 2011
The relationship of predator and prey size on the functional response of Nephus includens feeding on either Planococcus citri or Planococcus ficus mealybugs was empirically investigated. We used small and large predators to examine the role of predator size; respectively second or fourth instar larva of N. includens. The prey were second instar nymphs or adult females of P. citri or P. ficus. All eight predator-prey combinations produced a type II functional response. For the larger predator, predator handling time increased as prey size increased while for the small predator it remained constant. It was hypothesized that this was due to a habit of the smaller predators to consume prey only partially. Maximum predation rate was always greater in combinations of large predator-small prey. Larval developmental stages of N. includens did not show a high density-dependence with different prey size, which might impede their potential as biological control agents. The study highlights the importance of sizestructured populations of both predator and prey in functional response studies.
Scientific Reports
Understanding the factors governing predation remains a top priority in ecology. Using a dragonfly nymph-tadpole system, we experimentally varied predator density, prey density, and prey species ratio to investigate: (i) whether predator interference varies between prey types that differ in palatability, (ii) whether adding alternate prey influences the magnitude of predator interference, and (iii) whether patterns of prey selection vary according to the predictions of optimal diet theory. In single-prey foraging trials, predation of palatable leopard frog tadpoles was limited by prey availability and predator interference, whereas predation of unpalatable toad tadpoles was limited by handling time. Adding unpalatable prey did not affect the predator’s kill rate of palatable prey, but the presence of palatable prey increased the influence of predator density on the kill rate of unpalatable prey and reduced unpalatable prey handling time. Prey selection did not change with shifts in ...
Marine Ecology Progress Series, 1992
We investigated the influence of variations in the size of prey (Mallotus villosus) and a vertebrate predator (Gasterosteus aculeatus) on larval fish mortality rates during the period of yolk absorption using mid-size mesocosms (2.7 m". Increasing predator size increased mortality rates of capelin larvae. Variations in larval capelin size resulted in 2 distinct patterns. Between experimental trials, greater mean size of larval capelin in the mesocosm reduced mortality due to predation. Within an experimental mesocosm, larger larvae suffered higher mortality than smaller individuals. Contrasting patterns of size-dependent vulnerability to predation reflect the hierarchy of processes that determine the probability that a larval fish will be preyed upon. The broad scale response of the predator was determined by the mean relative sizes of prey and predator which govern the average probabilities of encounter, attack and capture. Within the search ambit of a predator (e.g area or volume searched within a complete diurnal foraging cycle) active prey selection for larger prey due to either greater visibility or higher energy reward was an important factor. A comparison of our results with estimated predation rates by the jellyfish Aurelia aurita indicates that at a similar size a gelatinous zooplankter consumes fewer larvae than a stickleback and is a less efficient predator as measured by the energy ingested relative to energy demands. For both vertebrate and invertebrate predators, the ratio of prey to predator lengths was a strong predictor of the daily mortality rate due to predation. Relative prey-predator sizes may provide a useful perspective to assess changes in larval fish vulnerability as they grow through a predator field.
An experimental test of the nature of predation: neither prey- nor ratio-dependent
Journal of Animal Ecology, 2004
There is a current debate about the appropriateness of prey-dependent vs. ratiodependent functional responses in predator-prey models. This is an important issue as systems governed by these models exhibit quite different dynamical behaviour. However, the issue is not yet resolved on a theoretical basis, and there is a lack of experimental evidence in natural systems. We used a paper wasp-shield beetle system in a natural setting to assess the validity of either approach. 2. We manipulated the abundance of herbivorous insect prey on thistle plants and of predatory paper wasps in the immediate environment of the prey by opening or closing cages containing wasp nests. 3. The number of wasps foraging at the site increased when cages were opened, but rapidly reached an asymptote, indicating predator interference. The predation rate per predator decreased with the number of wasps in the environment. Thus, the functional response depended on both prey and predator density. 4. Neither a pure prey-nor a pure ratio-dependent model fitted perfectly our observations. However, the functional response of the paper wasps towards shield beetle larvae was closer to ratio-dependence. To our knowledge, this is the first experimental evidence discriminating between ratio-and prey-dependence in a natural setting with unconfined predators and prey. 5. Predator interference was most probably responsible for the specific form of the functional response found. We found indications that both direct (e.g. aggression) and indirect interference mechanisms (e.g. depletion of easy-to-find prey) were at work in our system. We conclude that predator density cannot be ignored in models of predatorprey interactions.