Behavioral flexibility vs. rules of thumb: how do grey squirrels deal with conflicting risks?

In order to test how flexibly animals are able to behave when making trade-offs that involve assessing constantly changing risks, we examined whether wild Eastern grey squirrels showed flexibility of behavioral responses in the face of variation in two conflicting risks, cache pilferage and predation. We established that cache pilferage risk decreased with distance from cover, and was thus negatively correlated with long-term predation risk. We then measured changes in foraging and food caching behavior in the face of changes in the risk of predation and food theft over a short time-scale. We found that, overall, squirrels move further away from the safety of cover when they cache, compared to when they forage, as predicted by pilferage risk. However, there was no effect of immediate pilferage or predation risk (i.e. the presence of potential predators or pilferers) on the distance from cover at which they cached, and only a slight increase in forage distance when predation risk increased. These results suggest that ‘rules of thumb’ based on static cues may be more cost-effective for assessing risk than closely tracking changes over time in the way suggested by a number of models of risk assessment

Behavioural responses of Eastern grey squirrels, Sciurus carolinensis, to cues of risk while foraging

Lisa Leaver University of Exeter Psychology Washington Singer Exeter Devon EX4 4QG UKArticleCopyright © 2015 Elsevier B.V. All rights reserved.Previous studies have shown that Eastern grey squirrels modify their behaviour while foraging to offset risks of social and predatory costs, but none have simultaneously compared whether such modifications are performed at a cost to foraging. The present study directly compares how grey squirrels respond to cues of these risks while foraging. We simulated social risk and predatory risk using acoustic playbacks of stimuli that grey squirrels might be exposed to at a foraging patch: calls of conspecifics, heterospecifics (competitor and non-competitor) and predators. We found that grey squirrels responded to predator, heterospecific competitor and conspecific playbacks by altering their foraging and vigilance behaviours. Foraging was most disrupted by increased vigilance when we played calls of predators. Squirrels' response to calls of heterospecific competitors did not differ from their response to conspecific calls, and they resumed foraging more quickly after both compared to predator calls: whereas they showed little response to calls of non-competitor heterospecifics and a white noise control. We conclude that squirrels respond differentially to calls made by conspecifics, heterospecific competitors and predators, with the most pronounced response being to calls of predators. We suggest that squirrels may view conspecific and corvid vocalisations as cues of potential conflict while foraging, necessitating increased vigilance.Exeter Graduate Fellow scholarshi

Touch screen assays of behavioural flexibility and error characteristics in Eastern grey squirrels (Sciurus carolinensis)

This is the final version of the article. Available from the publisher via the DOI in this record.Behavioural flexibility allows animals to adjust their behaviours according to changing environmental demands. Such flexibility is frequently assessed by the discrimination–reversal learning task. We examined grey squirrels’ behavioural flexibility, using a simultaneous colour discrimination–reversal learning task on a touch screen. Squirrels were trained to select their non-preferred colour in the discrimination phase, and their preferred colour was rewarded in a subsequent reversal phase. We used error rates to divide learning in each phase into three stages (perseveration, chance level and ‘learned’) and examined response inhibition and head-switching during each stage. We found consistent behavioural patterns were associated with each learning stage: in the perseveration stage, at the beginning of each training phase, squirrels showed comparable response latencies to correct and incorrect stimuli, along with a low level of head-switching. They quickly overcame perseveration, typically in one to three training blocks. In the chance-level stage, response latencies to both stimuli were low, but during initial discrimination squirrels showed more head-switches than in the previous stage. This suggests that squirrels were learning the current reward contingency by responding rapidly to a stimulus, but with increased attention to both stimuli. In the learned stage, response latencies to the correct stimulus and the number of head-switches were at their highest, whereas incorrect response latencies were at their lowest, and differed significantly from correct response latencies. These results suggest increased response inhibition and attention allowed the squirrels to minimise errors. They also suggest that errors in the ‘learned’ stage were related to impulsive emission of the pre-potent or previously learned responses

Serial reversal learning in Gray Squirrels: learning efficiency as a function of learning and change of tactics

This is the author accepted manuscript. The final version is available from American Psychological Association via the DOI in this record.Learning allows individuals to adapt their behaviors flexibly to a changing environment. When the same change recurs repeatedly, acquiring relevant tactics may increase learning efficiency. We examined this relationship, along with the effects of proactive interference and other interference information, in a serial spatial reversal task with 5 gray squirrels (Sciurus carolinensis). Squirrels completed an acquisition and 11 reversal phases with a poke box in which 2 of 4 possible reward locations were baited diagonally in a square array. In this situation, an efficient tactic is to locate the diagonally related locations consecutively (integrative search tactic) instead of searching rewards in a clockwise or counterclockwise direction (sequential search tactic). All squirrels formed a learning set, acquiring successive reversals in fewer trials. Although 4 squirrels gradually employed more integrative tactics in locating the rewards both within and between phases, sequential tactics were used in the first trial of each phase. This suggests the integrative tactic did not depend on an association between the rewarded locations but was learned as a spatial pattern and/or by use of extra-apparatus cues to locate individual rewards. Generalized estimating equation models showed that learning efficiency increased with experience and tactic change. Although tactic change partially mediated the effect of learning on learning efficiency, learning was an independent contribution to improved efficiency. Squirrels that used more integrative tactics made fewer total errors than squirrels that used less integrative tactics, suggesting that learning a task-relevant tactic using spatial cues can provide direct benefits in maximizing rewards and minimizing time costs

How practice makes perfect: the role of persistence, flexibility and learning in problem solving efficiency

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.To fully understand how problem solving ability provides adaptive advantages for animals, we should understand the mechanisms that support this ability. Recent studies have highlighted several behavioural traits including persistence, behavioural variety and behavioural/cognitive flexibility that contribute to problem solving success. However, any increment in these traits will increase time and energy costs in natural conditions, so they are not necessarily advantageous. To examine how behavioural traits vary during learning to solve a problem efficiently, we gave grey squirrels (Sciurus carolinensis) a problem solving task that required squirrels to obtain out-of-reach but visible hazelnuts by making a lever drop in the laboratory. We recorded persistence, measured as attempt rate, flexibility, measured as the rate of switching between tactics, and behavioural selectivity, measured as the proportion of effective behaviours, in relation to problem solving efficiency on a trial-by-trial basis. Persistence and behavioural selectivity were found to be directly associated with problem solving efficiency. These two factors also mediated the effects of flexibility and increased experience. We also found two routes that led to more efficient problem solving across learning trials: increasing persistence or increasing behavioural selectivity. Flexibility was independent from learning. Flexibility could increase problem solving efficiency, but it also has a time cost; furthermore it seemed to involve a trade-off with behavioural selectivity, with high flexibility being associated with a higher frequency of some disadvantageous ineffective behaviours. These results suggest that flexibility is an independent cognitive process or behavioural trait that may not always bring advantages to animals

Quasinormal resonances of near-extremal Kerr-Newman black holes

We study analytically the fundamental resonances of near-extremal, slowly rotating Kerr-Newman black holes. We find a simple analytic expression for these black-hole quasinormal frequencies in terms of the black-hole physical parameters: omega=m Omega-2i pi T(l+1+n), where T and Omega are the temperature and angular velocity of the black hole. The mode parameters l and m are the spheroidal harmonic index and the azimuthal harmonic index of a co-rotating mode, respectively. This analytical formula is valid in the regime Im omega << Re omega <<1/M, where M is the black-hole mass.Comment: 4 page

Behavioral flexibility: A review, a model, and some exploratory tests

This is the final version. Available on open access from Springer via the DOI in this recordThis paper aimed to explore and clarify the concept of behavioral flexibility. A selective literature review explored how the concept of behavioral flexibility has been used in ways that range from acknowledging the fact that animals’ behavior is not always bounded by instinctual constraints, to describing the variation between species in their capacity for innovative foraging, a capacity that has repeatedly been linked to having a brain larger than would be predicted from body size. This wide range of usages of a single term has led to some conceptual confusion. We sought to find a more precise meaning for behavioral flexibility by representing it within a simple formal model of problem solving. The key to our model is to distinguish between an animal’s state of knowledge about the world and its observable behavior, using a construct of response strength to represent that underlying knowledge. We modelled behavioral flexibility as a parameter in the function that transforms response strengths into observable response probabilities. We tested this model in simulations based on some recent experimental work on animal problem solving. Initial results showed that parametric manipulation can mimic some of the behavioral effects that have been attributed to flexibility

Kerr black hole quasinormal frequencies

Black-hole quasinormal modes (QNM) have been the subject of much recent attention, with the hope that these oscillation frequencies may shed some light on the elusive theory of quantum gravity. We compare numerical results for the QNM spectrum of the (rotating) Kerr black hole with an {\it exact} formula Re$\omega \to T_{BH}\ln 3+\Omega m$, which is based on Bohr's correspondence principle. We find a close agreement between the two. Possible implications of this result to the area spectrum of quantum black holes are discussed.Comment: 3 pages, 2 figure

Bohr's Correspondence Principle and The Area Spectrum of Quantum Black Holes

During the last twenty-five years evidence has been mounting that a black-hole surface area has a {\it discrete} spectrum. Moreover, it is widely believed that area eigenvalues are {\it uniformally} spaced. There is, however, no general agreement on the {\it spacing} of the levels. In this letter we use Bohr's correspondence principle to provide this missing link. We conclude that the area spacing of a black-hole is $4\hbar \ln 3$. This is the unique spacing consistent both with the area-entropy {\it thermodynamic} relation for black holes, with Boltzmann-Einstein formula in {\it statistical physics} and with {\it Bohr's correspondence principle}.Comment: 10 page

Radiative falloff in Einstein-Straus spacetime

The Einstein-Straus spacetime describes a nonrotating black hole immersed in a matter-dominated cosmology. It is constructed by scooping out a spherical ball of the dust and replacing it with a vacuum region containing a black hole of the same mass. The metric is smooth at the boundary, which is comoving with the rest of the universe. We study the evolution of a massless scalar field in the Einstein-Straus spacetime, with a special emphasis on its late-time behavior. This is done by numerically integrating the scalar wave equation in a double-null coordinate system that covers both portions (vacuum and dust) of the spacetime. We show that the field's evolution is governed mostly by the strong concentration of curvature near the black hole, and the discontinuity in the dust's mass density at the boundary; these give rise to a rather complex behavior at late times. Contrary to what it would do in an asymptotically-flat spacetime, the field does not decay in time according to an inverse power-law.Comment: ReVTeX, 12 pages, 14 figure