The social life of animals, by W.C. Allee ...

Abstract

The aquarium-maze used in training part of the fish to come forward and part to go to the rear to be fed 164 35. Cyprinodon learn to move in a body more readily than to split into two separate groups 165 36. Goldfish learn more readily if accompanied by a trained leader 37. An aquarium-maze arranged to test the power of observation of fish 38. Goldfish react more rapidly if allowed to watch others perform^1 39. Flocks of hens are organized into a definite social hierarchy 40. Cockerels also have a social organization 209; principle of,

A statistical-reaction–diffusion approach for analyzing expansion processes

“…By "in the absence of demographic constraints" we mean that the frequency of nest creation f (x) and the local fitness F (x) do not take the environmental carrying capacity into account. The carrying capacity is incorporated in the computation of the nest density u n (x) through the terms min (·, K χ(x)) and min (·, χ(x)) in equations (3.4) and (3.6) (Allee, 1938;Dennis, 1989;Veit and Lewis, 1996). Experiments show that PPM clutches which are on the same tree tend to regroup in a bigger nest (ANR project "URTICLIM", unpublished data) and that mortality inside the nest is negatively correlated with nest size (Pérez-Contreras et al, 2003).…”

Diffusive and nondiffusive population models

“…Some population ecologists argue that the growth rate f may not be decreasing in u for all u ≥ 0, but it may achieve a maximum at an intermediate density. This so-called Allee effect [3] may be caused by, for instance, shortage of mates at low density, lack of effective pollination, or predator saturation [131]. Whereas in the logistic growth case (with a(x) > 0) there exists a unique nonnegative steady state (positive for slow diffusion and zero for fast diffusion; see [19]), there may be two steady states when an Allee effect is present [131].…”

Ecologia, infecção e doença

“…O papel e a importância das relações de competição e de cooperação na Bios fera foram logo reconhecidas, mas devido ao impacto social das obras de Malthus, Darwin, Spencer e Wallace, a "luta pela vida" e a competição seletiva receberam mais atenção que as relações de coopera ção entre organismos (3,22).…”

“…A cooperação resulta em que podem advir de associações de tipos vários, que vão desde o frouxo grupamento acidental ou agregado ocasional ou temporário de indivíduos independentes ou pertencentes a espécies distintas, à organização fami liar, com a transmissão de 'elementos cul turais adquiridos, e à coexistência neces sária e indispensável dos simbiontes es tritos (3,22,53).…”