Initial Distance Research Articles

Birds’ Flight Initiation Distance in Residential Areas of Beijing Are Lower than in Pristine Environments: Implications for the Conservation of Urban Bird Diversity

(1) Background: With rapid urbanization, birds are facing a variety of challenges. Evaluating bird behaviour changes in response to urbanization can help us understand how to make them coexist sustainably with humans. We aimed to investigate whether birds inhabiting residential areas differed in their escape behaviour and their influencing factors. (2) Methods: We used the flight initiation distance (FID), the horizontal distance between the observer and the target bird when it escapes, to measure the escape behaviour of birds. We chose 40 urban residential areas within the 5th ring road in Beijing and conducted surveys each month for one year. We applied Generalized Linear Mixed Models (GLMMs) separately to evaluate the response variable of FID for the total species, the most common species, and the other species. (3) Results: Birds that appear more frequently in residential areas or as ground foragers, insectivores, and omnivores are better adapted to human interference and have shorter FIDs. Individual initial conditions affect bird FID, and environmental characteristics can be used as predictors for the most common birds. Tree canopy coverage was found to positively affect FID, while floor area ratio (FAR) is negatively correlated with FID. (4) Conclusions: Our results demonstrated that birds in residential areas have been adapting to the human environment, and urban tree canopies can provide refuge for birds to avoid human interference. Our study focused on the response of bird FIDs to human interference and urban trees under high urbanization, which has substantial practical implications for urban managers to improve habitat quality to ensure that birds coexist with human beings.

Ice-releasing strategy to improve the dispersion of CNTs in cement paste with enhanced reinforcing efficiency

Due to the over-concentrated CNTs at the moment of adding an aqueous solution of CNTs (as-CNTs) into fresh cement mixture, bulk aggregation of CNTs immediately happens and limits its reinforcing efficiency to cement-based materials. This study proposed a novel ice-releasing strategy by solid mixing of cement particles with micro-scaled ice particles containing well-dispersed CNTs (ice-CNTs) at first and then slowly releasing of CNTs during the ice-melting process, which significantly enlarged the initial distance among neighbored CNTs, reduced the aggregation size of CNTs and relieved the over-concentrated problem of CNTs, and a better dispersion and stability of ice-CNTs in simulated cement pore solution was thus achieved and verified by visual observation, UV–Vis absorbance and particle size distribution. In this way, compared with as-CNTs, 0.08 wt% addition of ice-CNTs was more effective to reduce cement hydration heat, fine the pore structure and reduce the total porosity of cement matrix, and enhance the 3, 7 and 14-day compressive strength of cement paste by 12.0%, 7.1% and 12.1%, respectively. In addition, water adsorption of cement paste with ice-CNTs became the lowest one in all mixes up to 14 days. In conclusion, the research outcomes open the door to improve the dispersion and stability of CNTs in cement mixture by a novel ice-releasing strategy, and effectively enhance the reinforcement of CNTs to cement paste in terms of porosity, mechanical strength and durability.

Two-dimensional anisotropic vortex–bright soliton and its dynamics in dipolar Bose–Einstein condensates in optical lattice

We study construction and dynamics of two-dimensional (2D) anisotropic vortex–bright (VB) soliton in spinor dipolar Bose–Einstein condensates confined in a 2D optical lattice (OL), with two localized components linearly mixed by the spin–orbit coupling and long-range dipole–dipole interaction (DDI). It is found that the OL and DDI can support stable anisotropic VB soliton in the present setting for arbitrarily small value of norm N. We then present a new method via examining the mean square error of norm share of bright component to implement stability analysis. It is revealed that one can control the stability of anisotropic VB soliton only by adjusting OL depth for a fixed DDI. In addition, the dynamics of the anisotropic VB soliton was studied by applying the kick to them. The mobility of the single kicked VB soliton is Rabbi-like oscillation. However, for the collision dynamics of two kicked anisotropic VB solitons, their properties mainly depend on their initial distance and OL, and they can realize the transition from the bright component to the vortex component. Our work may provide a convenient way to prepare and manipulate anisotropic VB soliton in high-dimensional space.

Functional Results of Small Incision Cataract Surgery at the Nianankoro FOMBA Hospital in Segou, a Second Reference Centre in Mali

Introduction: Cataract is the leading cause of curable blindness in the world. Its treatment is surgical. The aim was to evaluate the functional results of cataract surgery in a second referral centre in Mali (Nianankoro FOMBA Hospital in Ségou) with reference to the quality standards of the World Health Organisation. Patients and methods: Prospective descriptive study conducted between October 2018 and September 2019 in the ophthalmology department of the Nianankoro FOMBA hospital in Ségou, in patients aged 40 years and over with cataract. Results: During the study, 954 eyes were operated on, of which 522 (54.7%) were female. The average age was 64.28 years. The occupation of housewife was 52.7%. The main reason for consultation was the decrease in visual acuity with 96.1%. Hypertension and diabetes were 20.1% and 5.7% respectively. The initial uncorrected distance visual acuity was less than 1/10 in 94.2% of cases. At 30 days postoperatively, the good, average and poor results were respectively 82.92%, 12.01% and 5.06% without optical correction, decreasing to 92.56%, 4.51% and 2.93% respectively after optical correction. Discussion: These results met the World Health Organization standards which recommend a value greater than or equal to 80% without correction and greater than 90% with correction for good results and a value of less than 5% for poor results with correction. Conclusion: Cataract surgery with Phaco A is a simple solution that gives good results and is well adapted to our socio-economic context.

Simulation of melt spreading over dry substrates with the moving particle Semi-implicit method

In a severe accident scenario of a light water reactor, the spreading of molten core materials (corium) on the floor of the reactor cavity may occur after the failure of the reactor pressure vessel (RPV), resulting in the so-called melt spreading process which is important to assess the melt progression towards containment structures (e.g., the liner) and the potential for ex-vessel coolability of corium. The present study is concerned with the numerical simulation of melt spreading on a dry floor using the Moving Particle Semi-implicit (MPS) method which is mesh free and suitable for such a free-surface flow. Multi-physics models are implemented in the MPS method to enable modeling of physical phenomena occurring in melt spreading process. The emphasis is to develop a crust formation model which is not only appropriate for capturing crust formation at the upper surface but also capable of reproducing the shape of the spread. A genetic algorithm (GA) is also employed to optimize the initial distance between particles. The multi-physics models and GA are coded into a computer program using C programming language. The MPS code is then used to simulate the small-scale pre-test and S3E 3MDS-Ox-2 melt spreading experiment conducted at KTH. The simulation results show the capability of the MPS code predicting melt leading-edge progression.

The influence of the site of rupture and gap distance in acute Achilles tendon rupture treated with functional rehabilitation

AimTo determine the influence of gap distance and its location on clinical and radiological outcomes in patients with acute rupture of Tendo-Achilles (TA) treated non-operatively with functional rehabilitation. MethodsTwenty-six patients with acute complete TA rupture underwent ultrasound (US) scanning within a week of their injury. The measurements taken included the distance of the rupture from the enthesis and the gap distance between the tendon edges in varying degrees of ankle and knee positions. All patients were managed non-operatively in functional weight-bearing orthoses. Nineteen patients were then followed up at a mean of 6.1 years (range 5.8–6.5) to assess their clinical and radiological outcomes. The outcomes included ultrasound assessment of tendon healing, Achilles Tendon Rupture Score (ATRS) and modified Leppilahti Score (mLS). ResultsIn the initial ultrasound, the mean distance of the rupture from the enthesis was 52 mm (range: 40–76). The mean gap distance with the foot plantigrade was 11.4 mm, which reduced to 4.8 mm with the foot in equinus. At final follow up, no re-ruptures had occurred. The mean ATRS and mLS were 86 and 71 respectively. There was a significant correlation between the distance of the rupture from the enthesis with the MLS total score (p = 0.02), mLS Fatigue domain score (p = 0.03), and the ATRS domains of strength (p = 0.04) and fatigue (p = 0.02). There was no significant correlation between the measured gap distance with respect to the mLS, ATRS or individual ATRS domain scores. Also, there was no significant difference in ATRS and mLS outcomes when comparing tendons with respect to healed tissue appearance and fibre orientation on ultrasound. ConclusionThe initial gap distance had no relationship with any of the measured clinical outcomes at the final follow up. The distance of the gap from the enthesis, however, may carry a greater prognostic value following non-operative treatment of Achilles tendon injuries.

Production Facility Layout Redesign Using Systematic Layout Planning And Blocplan Methods

Layout of production facilities in CV. Jaya Rubber Industry was identified as less than optimal. The placement of production facilities that are less than optimal causes the distance between several departments to be far apart, for example in the cutting section to the molding section, the molding section to the trimming section and also the QC and packing sections to the finished goods warehouse. It was also found that intersecting material flows can cause backtracking, for example between molding to trimming and packing to the finished goods warehouse. These problems can result in the production process being less effective and efficient. This research combines two methods, namely systematic layout planning and blocplan methods. The systematic layout planning and Blocplan methods have several stages in planning the layout. This method is believed to be able to solve various problems that exist within the company such as production flow, transportation, warehousing, assembly and others. This method was chosen because the current industrial conditions require adjustments in the preparation of a good layout. The results of this study obtained a layout from the blocplan method which was chosen as the proposed layout with a total displacement distance of 44.25 with a decrease in distance of 23.75 m from the initial distance, with an efficiency level of 34% which was able to improve the flow of the production process for the better.

Lockdown effects on fear revealed direct and indirect effects of human presence on perceived predation risk

The Covid-19 lockdown reduced drastically human presence outdoors, providing an uncontrolled experiment for disentangling direct and indirect effects of human presence on animal fearfulness. We measured 18,494 flight initiation distances (FIDs, the distance at which individual animals fly away when approached by a human) from 1333 populations of 202 bird species taken in four European cities both before, during and after the lockdown. FIDs decreased during lockdown in rural habitats but increased in urban habitats, especially for singing birds. Height above ground increases during lockdown in non-singing birds only, and birds adjusted horizontal tolerance to approach according to height outside lockdown, in rural habitats and while not singing. Responses showed lagged effects after lockdown in urban but not in rural habitats. Differential responses to lockdown among habitats and between signing and non-singing birds were consistent with relaxation of direct disturbance effects on birds in rural habitats during lockdown, as well as with increased indirect fear effects mediated by predator release in cities. FIDs seemed to measure the balance of direct and indirect effects of humans on predations risk and food needs rather than direct effects of humans on fear.

House Sparrow (Passer domesticus) escape behavior is triggered faster in smaller settlements

A recurrent behavioral trait model to study adaptation to urban environments is the flight initiation distance (FID), measured as the distance at which animals flee from an approaching threat. It has previously been shown that urban birds display shorter FID than their non-urban (rural) counterparts. However, discerning whether this is the result of habituation to human presence and frequentation, or of ecological factors related to the size of the city (considered as “systemic habituation”), has not yet been addressed. In this study, we analyzed House Sparrow (Passer domesticus) FIDs in a network of 26 small towns and villages within the same region in northeastern Spain. Our aim was to relate FID to human population density and settlement size. If the habituation to human presence hypothesis was supported, we should expect FIDs to decrease with the density of the human population across the human settlements, since this type of habituation is related to the rate of human exposure and this is proportional to human density. However, if the systemic habituation hypothesis was supported, FIDs should instead relate to the size of the human settlements, as the abundance of predators, similarly to other ecological variables, is often proportional to the size of towns. Results showed House Sparrows to be bolder in larger human settlements, but not necessarily the ones with a higher density of human population. This supports the idea that the fact that urban birds display shorter FIDs than their rural counterparts is the result of systemic ecological factors rather than the results of a simple habituation to humans.

Maximization of Energy Efficiency by Synchronizing the Speed of Trains on a Moving Block System

The publication deals with the problem of the effect of interference with the movement of the “preceding” train on the movement of the “following” train in the case of efforts to reduce the distance between trains on a moving block interval. The paper presents results of the simulations for train of the ED250 type for a set of 135 traffic situations: for three contexts of reducing the speed of the “preceding” train, for five variants of the method of controlling the “following” train and for nine initial distances between these trains. The results confirmed the possibility of gaining time and energy benefits by implementing an appropriate method of controlling the “following” train, as well as providing insights into the area of shortening the gaps between trains, including the pursuit of synchronizing the speed of trains and possibly coupling them into a so-called virtual couples.

Heat stress increases risk taking in foraging shorebirds

Abstract Animals often face a trade‐off between food acquisition and predation/disturbance avoidance. Yet, the extent to which this trade‐off is affected by modulating factors such as thermal risk and foraging opportunities has been largely overlooked. Here, we examined the influence of temporal and environmental gradients on the flight initiation distance (FID, the distance at which animals flee from an approaching human‐simulated predator) and escape mode (flying/low risk versus running/low cost) in 16 species of shorebirds foraging on tidal flats of the Bijagós Archipelago, Guinea‐Bissau. We measured escape responses throughout the low tide period during wet and dry seasons and simultaneously recorded microclimate variables and occurrence of heat‐reduction behaviour (ptiloerection). Furthermore, we measured corticosterone metabolites (CORTm) from droppings in red knots Calidris canutus to assess whether ptiloerection is associated to a physiological stress response to hot conditions. Overall, birds tolerated a closer approach at higher environmental temperatures and when showing ptiloerection. They also had shorter FIDs during the dry season and towards the start/end of the low tide period. FIDs also increased with body mass and decreased in areas with more human presence. In red knots, individuals showing ptiloerection had higher levels of CORTm, demonstrating a link between physiological and behavioural stress coping responses to heat events. Our results suggest that heat‐stressed shorebirds take greater risks, supporting the idea of a thermoregulation–predation risk trade‐off. They also indicate that shorebirds adjust risk taking to tidal and seasonal cycles, generally reducing FIDs when the energetic costs of escape are expected to be large. Finally, they suggest that shorebirds habituate to non‐lethal human presence and respond to perceived predation risk in accordance with the predictions of optimal escape theory. These results are relevant to many animals that face a tight window for foraging activity while being exposed to predation/disturbance and heat during the day. We discuss management implications of our results in the context of global change. Read the free Plain Language Summary for this article on the Journal blog.

Environmental Modulation of Mechanical and Thermodynamic Forcing from Cold Pool Collisions

Abstract Cold pools can initiate new convection by increasing vertical velocity (mechanical forcing) and locally enhancing moisture content (thermodynamic forcing). This study investigates the impact of the environment on mechanical and thermodynamic forcing from cold pool collisions. An ensemble of high-resolution numerical simulations was conducted that tested the sensitivity of cold pool collisions to three parameters: 1) the initial temperature deficit of cold pools, 2) the initial distance between cold pools, and 3) the static stability and moisture content of the environment. These parameters are tested in the absence of condensation, surface fluxes, radiation, and wind shear. Colder initial cold pools increase mechanical and thermodynamic forcing owing to greater horizontal winds during collisions. For all environments tested, mechanical forcing peaked robustly at an optimal initial distance between the cold pools due to a balance between the creation and dissipation of kinetic energy, and the different phases of density current evolution. Thermodynamic forcing peaked for greater initial cold pool distances than those associated with mechanical forcing. Decreased low-level static stability and an increased vertical gradient in low-level moisture enhanced mechanical and thermodynamic forcing, respectively. It is also shown that the initial temperature deficit had the greatest impact on mechanical and thermodynamic forcing, followed by the environment, and finally the initial separation distance. Finally, cold pool collisions are classified as “mechanically strong” or “mechanically weak,” where mechanically strong collisions increased mechanical forcing beyond that driven by the initial outward spreading of the cold pools. An analogous classification of “thermodynamically strong/weak” is also presented.

Interaction of a single bubble and an elastic plate: Influence of the standoff distance

The objective of this study was to investigate the coupled dynamics of a collapsing bubble and the motion of a nearby elastic plate at different initial distances. This was achieved using a combination of experimental and computational models. In the experiments, high-speed photography was used to record the temporal and spatial evolution of the collapse of a single bubble near an elastic boundary under normalized standoff distances γ ranging from 1.0 to 3.3. Digital image correlation was used to synchronously record the motion of the elastic plate. For the numerical simulations, taking the fluid compressibility and boundary motion into account, the immersed-boundary method was introduced to simulate the interaction between the elastic plate and bubble collapse. The results show that, with different initial distances, the dynamic behaviors of the bubble, including oscillation time, impact mode, and energy conversion, are different, and this is caused by the elastic rebound of the plate. In addition, the direction and amplitude of the deformation of the elastic plate are also influenced by the impact effects during bubble oscillation and rebound. The combined form of these impact behaviors changes with initial distance, and there are three typical impact patterns: the shock-wave effect, jet-effect, and hybrid shock-wave and jet-effect modes. In particular, when γ < 1.5, the jet effect and hybrid impact forms, which are dominated by the high-speed jet, can result in asymmetric deformation and cause greater local damage to the elastic plate. Finally, we summarize the combined mechanisms that govern the impact of a collapsing bubble on an elastic plate.

Temporal evolution of flow field structure for vehicles accelerating in evacuated tube transportation system

As a supersonic transportation system, the flow around a vehicle in an Evacuated Tube Transportation (ETT) system will evolve through series of flow structures during acceleration. The occurrence of choked flow and shock wave will especially lead to the drastic change in flow field structures. In this study, based on the one-dimensional inviscid flow assumption, a theoretical model is established to quantitatively describe the formation time, formation location of choked flow, and Frontal Normal Shock Wave (FNSW), as well as the distance of the disturbed flow field region ahead of the vehicle in the ETT system. It is found out that the formation time of FNSW as well as the initial distance between the vehicle head and FNSW is linearly proportional to the blockage ratio while linearly inverse proportional to the acceleration rate of the vehicle. An experimentally verified numerical model is also established with an overset mesh technique to investigate the flow field evolution for vehicles accelerating in the ETT system. The results from numerical analysis agree well with the theoretical model. Meanwhile, five typical flow field structures are summarized for a vehicle accelerating from a stationary state to supersonic state in the ETT system. The applicability of the wind tunnel method and overset mesh technique in numerical simulation of the ETT system is systematically discussed. The influence of occurrence and dissipation of choked flow and shock wave on the vehicle's aerodynamic drag profile are then analyzed quantitatively.

DRD4 allele frequencies in greylag geese vary between urban and rural sites.

With the increasing urbanization of the last decades, more and more bird species occur in urban habitats. Birds which thrive in urban habitats often have a higher tolerance toward human disturbance and show behaviors which differ from their rural counterparts. There is increasing evidence that many behaviors have a genetic basis. One candidate gene is the dopamine receptor D4 (DRD4), which has been associated with fear and thus, flight initiation distance (FID). In this study, we analyzed a segment of DRD4 in greylag geese Anser anser, describing the variability of this gene across several geographically distant populations, and comparing its variability between an urban and a rural site in south-west Germany. We additionally measured FIDs of urban and rural geese to test for a possible correlation with DRD4 genotypes. We found a high variation within DRD4, with 10 variable sites leading to 11 alleles and 35 genotypes. Two genotypes occurred in 60% of all geese and were thus defined as common genotypes versus 33 rare genotypes. Population differentiation was very low between the urban and rural sites in Germany but common genotypes occurred more often in the urban area and rare genotypes more often in the rural area. FID was significantly higher at the rural site, but no significant correlation between FID and DRD4 genotypes could be detected. Nevertheless, our results suggest that local site selection may be related to DRD4 genotypes.

Experimental and Theoretical Investigation on the Dynamic Response of Ferrofluid Liquid Marbles to Steady and Pulsating Magnetic Fields.

Liquid marbles are droplets enwrapped by a layer of hydrophobic micro/nanoparticles. Due to the isolation of fluid from its environment, reduction in evaporation rate, low friction with the surfaces, and capability of manipulation even on hydrophilic surfaces, liquid marbles have attracted the attention of researchers in digital microfluidics. This study investigates the manipulation of ferrofluid liquid marbles (FLMs) under DC and pulse width-modulated (PWM) magnetic fields generated by an electromagnet for the first time. At first, the threshold of the magnetic field for manipulating these FLMs is studied. Afterward, the dynamic response of the FLMs to the DC magnetic field for different FLM volumes, coil currents, and initial distances of FLM from the coil is studied, and a theoretical model is proposed. By applying the PWM magnetic field, it is possible to gain more control over the manipulation of the FLMs on the surface and adjust their position more accurately. Results indicate that with a decrease in FLM volume, coil current, and duty cycle, the FLM step length decreases; hence, FLM manipulation is more precise. Under the PWM magnetic field, it is observed that FLM movement is not synchronous with the generated pulse, and even after the coil is turned off, FLMs keep their motion. In the end, with proper adjustment of the electromagnet pulse width, launching of FLMs at a distance farther than the coil is observed.

A test of the species confidence hypothesis in dusky damselfish.

Visual cues are important in both interspecific and intraspecific communication. The species confidence hypothesis proposes that animals are more attracted to conspecific colors and repelled by colors, not on their bodies. Studies on terrestrial lizards and birds have tested the species confidence hypothesis and shown that conspecific colors elicit reduced antipredator behavior. To date, the species confidence hypothesis has not been tested in the marine environment, specifically on coral reefs where color communication is of vital importance. We addressed this knowledge gap by measuring flight initiation distance (the distance an individual moves away from an approaching threat) in dusky damselfish (Stegastes nigricans) in response to an approaching disc of 1 of 4 different color treatments: conspecific, blue, yellow, and black. If the species confidence hypothesis explained variation in damselfish flight initiation distance, then we expected individuals to tolerate closer approaches when approached by a conspecific color. In addition, we calculated the color difference between each stimulus and its corresponding background as a potential alternative explanation for flight responses. Damselfish tolerated the closest approach from the conspecific color stimulus; there were no significant differences between other colors and there was no support for the alternative color difference hypothesis. As with similar terrestrial studies, these results are relevant to ecotourists' choice of swimsuit and wetsuit colors because color choice may modify natural antipredator behavior.

Artificial lighting affects the landscape of fear in a widely distributed shorebird

Fear influences almost all aspects of a prey species’ behaviour, such as its foraging and movement, and has the potential to cause trophic cascades. The superior low-light vision of many predators means that perceived predation risk in prey is likely to be affected by light levels. The widespread and increasing intensity of artificial light at night is therefore likely to interfere with this nocturnal visual arms race with unknown behavioural and ecological consequences. Here we test how the fear of predation perceived by wintering Eurasian curlew foraging on tidal flats is influenced by lighting. We quantified flight initiation distance (FID) of individuals under varying levels of natural and artificial illumination. Our results demonstrate that FID is significantly and substantially reduced at low light levels and increases under higher intensity illumination, with artificial light sources having a greater influence than natural sources. Contrary to the sensory-limitation hypothesis, the curlews’ unwillingness to take flight in low-light appears to reflect the risks posed by low-light flight, and a desire to remain on valuable foraging grounds. These findings demonstrate how artificial light can shape the landscape of fear, and how this interacts with optimal foraging decisions, and the costs of taking flight.

Effect of fluidic obstacles on flame acceleration and DDT process in a hydrogen-air mixture

Using solid obstacles to accelerate the deflagration to detonation transition (DDT) process induces additional thrust loss, and fluidic obstacles can alleviate this problem to a certain extent. A detailed simulation is conducted to investigate the effects of multiple groups of fluidic obstacles on the flame acceleration and DDT process under different initial velocities and gas types. The results show that, initially, the propagation of reflected shock wave formed by jet impingement is opposite to the flame acceleration direction, thus increasing the initial jet velocity will hinder the flame acceleration. Later, the vortex structure and enhanced turbulence can promote flame acceleration. As the flame accelerates, the virtual blockage ratio of the fluidic obstacles decreases, and increasing initial jet velocity or using reactive jet gases both affect the virtual blockage ratio. Further, increasing initial jet velocity or using reactive jet gases can shorten the detonation initiation time and distance. Compared with solid obstacles, it is concluded that fluidic obstacles can achieve faster detonation initiation with a smaller blockage ratio. Overall, the detonation phenomena in this study are all triggered by hot spots formed by the interaction between reflected waves and distorted flame, but the formation of reflected waves varies.

How does damselfish risk assessment vary with increased predator and shoal size?

Predation is an important factor that influences the behavior of prey species. When approached by a predator, individuals must make escape decisions that may be sensitive to the level of perceived risk. Both predator size and prey group size influence vulnerability and may influence this assessment. If fish perceive larger predators as a greater threat, differences in predator size should reflect differences in their antipredator response. Group size may also influence antipredator response in congregated fish. We investigated the flight initiation distance (FID) of differently sized groups of dusky damselfish (Stegastes nigricans) to measure their antipredator response to varying sizes of artificial stimuli. We found no effect of shoal size on FID, indicating that damselfish risk assessment is not influenced by group size. However, we did find that stimulus size interacted with starting distance (SD) to affect FID, with damselfish distinguishing between stimulus sizes at shorter SD but not at longer SD. Adjustment of FID in response to varying stimuli indicates that damselfish risk assessment is plastic, and consequently, antipredator responses may be adaptable in changing ocean ecosystems. Because damselfish are herbivores that feed on algae in coral reefs, understanding factors affecting their assessment of risk is important to understanding the overall ecosystem structure. These behavioral responses could be significant in the context of anthropogenic activities, mainly overfishing, which shifts community composition by disproportionately removing larger top predators.