31 research outputs found
Does Sex-Selective Predation Stabilize or Destabilize Predator-Prey Dynamics?
Background: Little is known about the impact of prey sexual dimorphism on predator-prey dynamics and the impact of sexselective
harvesting and trophy hunting on long-term stability of exploited populations.
Methodology and Principal Findings: We review the quantitative evidence for sex-selective predation and study its longterm
consequences using several simple predator-prey models. These models can be also interpreted in terms of feedback
between harvesting effort and population size of the harvested species under open-access exploitation. Among the 81
predator-prey pairs found in the literature, male bias in predation is 2.3 times as common as female bias. We show that
long-term effects of sex-selective predation depend on the interplay of predation bias and prey mating system. Predation
on the ‘less limiting’ prey sex can yield a stable predator-prey equilibrium, while predation on the other sex usually
destabilizes the dynamics and promotes population collapses. For prey mating systems that we consider, males are less
limiting except for polyandry and polyandrogyny, and male-biased predation alone on such prey can stabilize otherwise
unstable dynamics. On the contrary, our results suggest that female-biased predation on polygynous, polygynandrous or
monogamous prey requires other stabilizing mechanisms to persist.
Conclusions and Significance: Our modelling results suggest that the observed skew towards male-biased predation might
reflect, in addition to sexual selection, the evolutionary history of predator-prey interactions. More focus on these
phenomena can yield additional and interesting insights as to which mechanisms maintain the persistence of predator-prey
pairs over ecological and evolutionary timescales. Our results can also have implications for long-term sustainability of
harvesting and trophy hunting of sexually dimorphic species
Optimal foraging and community structure: implications for a guild of generalist grassland herbivores
A particular linear programming model is constructed to predict the diets of each of 14 species of generalist herbivores at the National Bison Range, Montana. The herbivores have body masses ranging over seven orders of magnitude and belonging to two major taxa: insects and mammals. The linear programming model has three feeding constraints: digestive capacity, feeding time and energy requirements. A foraging strategy that maximizes daily energy intake agrees very well with the observed diets. Body size appears to be an underlying determinant of the foraging parameters leading to diet selection. Species that possess digestive capacity and feeding time constraints which approach each other in magnitude have the most generalized diets. The degree that the linear programming models change their diet predictions with a given percent change in parameter values (sensitivity) may reflect the observed ability of the species to vary their diets. In particular, the species which show the most diet variability are those whose diets tend to be balanced between monocots and dicots. The community-ecological parameters of herbivore body-size ranges and species number can possibly be related to foraging behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47765/1/442_2004_Article_BF00377109.pd