Scale invariant patterns have been found in different biological systems, in many cases resembling what physicists have found in other, nonbiological systems. Here we describe the foraging patterns of free-ranging spider monkeys (Ateles geoffroyi) in the forest of the Yucatan Peninsula, Mexico and find that these patterns closely resemble what physicists know as Lévy walks. First, the length of a trajectorys constituent steps, or continuous moves in the same direction, is best described by a power-law distribution in which the frequency of ever larger steps decreases as a negative power function of their length. The rate of this decrease is very close to that predicted by a previous analytical Lévy walk model to be an optimal strategy to search for scarce resources distributed at random. Second, the frequency distribution of the duration of stops or waiting times also approximates to a power-law function. Finally, the mean square displacement during the monkeys first foraging trip increases more rapidly than would be expected from a random walk with constant step length, but within the range predicted for Lévy walks. In view of these results, we analyze the different exponents characterizing the trajectories described by females and males, and by monkeys on their own and when part of a subgroup. We discuss the origin of these patterns and their implications for the foraging ecology of spider monkeys.Communicated by D. Watts 相似文献
A swarm of honeybees provides a striking example of an animal group performing a synchronized departure for a new location;
in this case, thousands of bees taking off at once to fly to a new home. However, the means by which this is achieved remain
unclear. Shortly before takeoff, one hears a crescendo of a high-pitched mechanical signal—worker piping—so we explored the
role of this signal in coordinating a swarm’s mass takeoff. Specifically, we examined whether exclusively nest site scouts
produce the worker piping signal or whether it is produced in a relay or chain reaction fashion. We found no evidence that
bees other than the scouts that have visited the swarm’s chosen nest site produce piping signals. This absence of relay communication
in piping suggests that it is a signal that only primes swarms for takeoff and that the release of takeoff is triggered by
some other signal or cue; perhaps the takeoff of bees on the swarm periphery as they reach flight temperature in response
to piping. 相似文献
Abstract: Forest-associated species in fragmented landscapes must traverse potentially inhospitable gaps to move between habitat patches. Although conservation biologists advocate connecting patches with corridors or improving the matrix to make it suitable for movement, little is known about the factors influencing gap-crossing decisions for most species. We investigated gap crossing by the red squirrel ( Tamiasciurus hudsonicus ) in logged landscapes in southeastern Alaska, where the species avoids microhabitats associated with gaps created by clearcutting. We released individuals across clearcuts and determined the routes they took home with tracking spools and radio telemetry. Of 36 adult red squirrels translocated across six clearcuts, 14 crossed clearcuts to reach home. Squirrels were more likely to cross clearcuts if the detour efficiency (distance to home crossing gap divided by distance of forested detour) was low, indicating an ability to compare distances along alternate routes and travel costs or risks in different habitats. No other landscape metrics, such as gap size or crossing distance, predicted crossing behavior. Red squirrels of low body mass were more likely to cross clearcuts, where the probability of encountering conspecifics is low. Distance predicted route choice for squirrels detouring around clearcuts. Indirect evidence suggests that perceived predation risk, energetic costs, or both are higher in clearcuts. Detour efficiency reportedly influences the gap-crossing decisions of some forest-associated birds, but this is the first demonstration of its role in gap-crossing decisions by a mammal. 相似文献
Objective: The effect of traffic signs on the behavior of drivers is not completely understood. Knowing about how humans process the meaning of signs (not just by learning but instinctively) will improve reaction time and decision making when traveling. The economic, social, and psychological consequences of car accidents are well known.
Methods: This study sounds out which traffic signs are more ergonomic for participants, from a cognitive point of view, and determines, at the same time, their effect in participants' movement trajectories in a driving simulation task.
Results: Results point out that the signs least representative of their meaning produce a greater deviation from the center of the road than the most representative ones.
Conclusions: This study encourages both an in-depth analysis of the effect on movement of roadside signs and the study of how this effect can be modified by the context in which these signs are presented (with the aim to move the research closer to and analyze the data in real contexts). The goal is to achieve clarity of meaning and lack of counterproductive effects on the trajectory of representative signs (those that provoke fewer mistakes in the decision task). 相似文献
Batch equilibrium and soil thin layer chromatography (TLC) techniques were used to investigate the influence of different volume fractions of organic cosolvents (acetone and methanol) on the adsorption and movement of carbaryl in four different types of Indian soils. L-shaped isotherms were obtained for both the cosolvent–water mixtures at all fs values and were in close agreement with the Freundlich equation. Higher adsorption was observed on F.R.I. soil (FSL) followed by Alampur soil (ASL), Kalai soil (KL), and Bhoran soil (BSL) at all fs values for both the cosolvent systems as was anticipated from the K and KD values. The K and KD values also confirmed that carbaryl adsorption was higher in methanol–water mixture than acetone–water mixture and decreased with increasing fs values. The frontal Rf values obtained from soil TLC studies were inversely proportional to the K and KD values for both the cosolvent systems. The higher K and KD values and lower Rf values in methanol–water mixtures relative to acetone–water mixtures for all the soils indicated that acetone had a greater potential for ground water contamination compared to methanol. The adsorption data were used to evaluate the cosolvent theory for describing adsorption of carbaryl in acetone–water and methanol–water mixtures. The aqueous phase partition coefficients, KDW (mol g?1), normalized with respect to foc for carbaryl was evaluated by extrapolating fs → 0. 相似文献