Averted predator gaze reduces latency to flee by zebra-tailed lizards (Callisaurus draconoides)

2015 ◽  
Vol 65 (3-4) ◽  
pp. 299-310
Author(s):  
William E. Cooper ◽  
Wade C. Sherbrooke
Keyword(s):  
Short Interval ◽  
Fixed Interval ◽  
Short Latency ◽  
Flight Initiation Distance ◽  
Predator Prey ◽  
Direct Gaze ◽  
The Cost ◽  
Averted Gaze ◽  
Over Time ◽  
Flight Initiation

Directness of a predator’s gaze affects several aspects of antipredatory behavior, including flight initiation distance (FID = predator-prey distance when fleeing begins), which is longer under direct than averted gaze. However, the effect of gaze directness on probability of fleeing or latency to flee (LF) in a short interval when a prey is immobile near an immobile predator is unknown. We predicted that probability of fleeing is greater and LF is shorter if the predator’s gaze is averted than direct. If the predator has not detected the prey, it will detect it immediately and attack when the prey moves while under direct gaze. Therefore, the prey is less likely to flee than if the predator is looking elsewhere. Under direct gaze the cost of fleeing decreases over time because the predator is increasingly likely to detect the prey. Under averted gaze, risk of being detected is constant for immobile prey and increases if the prey flees. Cost of fleeing under averted gaze is therefore constant and lower if the prey flees than under direct gaze at short latency, predicting shorter LF and greater likelihood of fleeing within a short fixed interval. We test this novel prediction of a model of the effect of gaze directness using the zebra-tailed lizard, Callisaurus draconoides. The proportion of lizards that fled was three times greater for averted than direct gaze, suggesting that prey under scrutiny reduce movement to avoid being detected. We discuss effects of gaze on FID, LF and probability of fleeing.

Crypsis influences escape decisions in the Round-tailed Horned Lizard (Phrynosoma modestum)

2010 ◽  
Vol 88 (10) ◽  
pp. 1003-1010 ◽  
Author(s):  
William E. Cooper, ◽  
Wade C. Sherbrooke
Keyword(s):  
Body Temperature ◽  
Predation Risk ◽  
Upright Posture ◽  
Flight Initiation Distance ◽  
Lower Body ◽  
Running Speed ◽  
Predator Prey ◽  
Sandy Area ◽  
Lower Body Temperature ◽  
Flight Initiation

Flight initiation distance (predator–prey distance when escape begins) increases as predation risk increases. Prey should have longer flight initiation distance when their background, movement, or current posture reduces crypsis. Flight initiation distance of ectotherms may increase at lower body temperature to compensate for slower running speed. However, for cryptic prey, fleeing might increase the probability of being detected. The Round-tailed Horned Lizard ( Phrynosoma modestum Girard, 1852) is eucryptic and resembles small stones. We predicted that flight initiation distance by P. modestum is shorter among stones than on uniform sand. Because movement and upright posture disrupt crypsis, we predicted that flight initiation distance is greater after movement and when standing than when still and lying on the ground. As predicted, flight initiation distances were shorter on a rocky than sandy area, when lying flat than standing, and while immobile than after moving. We measured running speed and flight initiation distance to determine relationships among body temperature, speed, and escape decisions. Running speed and flight initiation distance were reduced at lower body temperature, suggesting that crypsis reinforced by immobility is more advantageous than longer flight initiation distance for cool, slow lizards. The lizards adjusted escape decisions to current effectiveness of crypsis and escape ability.

Compensatory changes in escape and refuge use following autotomy in the lizard Sceloporus virgatus

2007 ◽  
Vol 85 (1) ◽  
pp. 99-107 ◽  
Author(s):  
W.E. Cooper, Jr.
Keyword(s):  
Body Part ◽  
Control Group ◽  
Flight Initiation Distance ◽  
Refuge Use ◽  
Predator Prey ◽  
Escape Theory ◽  
Antipredatory Strategies ◽  
Sceloporus Virgatus ◽  
Flight Initiation ◽  
Predator Effects

Following autotomy of a body part to escape from a predator, prey may alter antipredatory strategies to compensate for the inability to use autotomy and impaired escape ability. Because prey that have been captured may increase their assessment of risk posed by a predator, effects of capture may have been attributed to autotomy. I conducted an experiment using three groups of striped plateau lizards ( Sceloporus virgatus Smith, 1938): control, captured, and autotomized. Captured and autotomized lizards were less active on the day after autotomy than controls. Flight initiation distance and distance fled were greater in both experimental groups than in the control group, but did not differ between experimental groups. Flight initiation distance was greater in autotomized than in captured lizards only in males. No sex difference occurred for distance fled. Autotomized lizards entered refuges more than other groups. Escape strategy changed after autotomy to increased reliance on refuge and, in males, to increased flight initiation distance; behaviours that are appropriate to compensate for impaired escape ability. Decreased activity and increased distance fled might erroneously have been considered effects of autotomy, had effects of capture not been assessed. Predictions of escape theory that flight initiation distance and distance fled increase with predation risk were supported.

Flight initiation distance is differentially sensitive to the costs of staying and leaving food patches in a small-mammal prey

2009 ◽  
Vol 87 (11) ◽  
pp. 1016-1023 ◽  
Author(s):  
Patricio A. Lagos ◽  
Andrea Meier ◽  
Liliana Ortiz Tolhuysen ◽  
Rodrigo A. Castro ◽  
Francisco Bozinovic ◽  
...  
Keyword(s):  
Small Mammal ◽  
Antipredator Behavior ◽  
Interactive Effect ◽  
Flight Initiation Distance ◽  
Food Patch ◽  
Supplementary Food ◽  
Escape Theory ◽  
Risk Of Predation ◽  
The Cost ◽  
Flight Initiation

Escape theory predicts that a prey should flee from an approaching predator at a point in which the cost of staying equals the cost of escape. We manipulated the cost of fleeing upon approaching human predators by providing the small mammal Octodon degus (Molina, 1782) with varying amounts of supplementary food likely to disappear while the animals are not in the food patch (e.g., hidden in their burrows). Simultaneously, we manipulated the risk of remaining in the patch by providing supplementary food at varying distances from the nearest burrow. Degus fled at a shorter distance to approaching predators when foraging in patches closer to the nearest burrow and supplied with relatively high abundance of food, but only when these rodents were foraging socially. Also, degus fled at a greater distance to approaching predators when foraging in patches far from the nearest burrow. Thus, functions linked to the loss of feeding opportunities and the risk of predation interact to influence flight initiation distance after a simulated attack. This study represented one of the few demonstrations of an interactive effect between cost and risks on antipredator behavior in a small, social prey mammal.

FEAR and DREAD: starting distance, escape decisions and time hiding in refuge

Behaviour ◽  
2015 ◽  
Vol 152 (10) ◽  
pp. 1371-1389 ◽  
Author(s):  
William E. Cooper ◽  
Wade C. Sherbrooke
Keyword(s):  
Flight Initiation Distance ◽  
Predator Prey ◽  
Sceloporus Virgatus ◽  
Flight Initiation

Flight initiation distance (FID = predator–prey distance when escape begins) increases as starting distance (predator–prey distance when approach begins) increases. The flush early and avoid the rush (FEAR) hypothesis proposes that this relationship exists because monitoring an approach is costly. Hypothesized causes are increase in assessed risk and decrease in obtainable benefits while monitoring as starting distance increases. We propose the delay risking emergence and avoid dying (DREAD) hypothesis: hiding time in refuge increases as starting distance increases because prey use risk assessed during approach to estimate risk upon emerging. In the lizard Callisaurus draconoides, FID increased as standardized starting distance increased at faster approach speeds, supporting the FEAR hypothesis. In its first test, the DREAD hypothesis was supported: hiding time in the lizard Sceloporus virgatus increased as standardized starting distance increased. No large benefits were attainable, suggesting that dynamic increase in assessed risk accounts for these findings.

Conspicuousness and vestigial escape behaviour by two dendrobatid frogs, Dendrobates auratus and Oophaga pumilio

Behaviour ◽  
2009 ◽  
Vol 146 (3) ◽  
pp. 325-349 ◽  
Author(s):  
Janalee Caldwell ◽  
Laurie Vitt ◽  
William Cooper
Keyword(s):  
Defensive Behavior ◽  
Close Approach ◽  
Flight Initiation Distance ◽  
Escape Behaviour ◽  
Predator Prey ◽  
Poison Frogs ◽  
Oophaga Pumilio ◽  
Approach Speed ◽  
Dendrobates Auratus ◽  
Flight Initiation

AbstractAposematic prey are thought to move slowly and openly near predators, but exhibit reduced escape behaviour. We studied conspicuousness and escape by aposematic poison frogs (Dendrobates auratus and Oophaga pumilio). In circles of leaf litter, observers detected poison frogs quickly. Flight initiation distance (FID, predator-prey distance when escape begins) increases with approach speed in non-cryptic palatable prey, but not for frogs in clearings, which permitted close approach. On trails frogs moved slowly into forest and FID in D. auratus increased with approach speed. Distance from cover and handling exposing predators to distastefulness may account for greater reliance on aposematism in clearings. We observed responses to a simulated predator (stick with painted face) in three conditions: not approached, approached, and touched. Latency to hop and time to exit circles decreased and exit from circles was directed further away from the approach path in the order not approached, approached, touched. Oophaga pumilio changed directions less when approached than not; many exhibited no escape behaviour. Aposematic dendrobatids move slowly near predators, but retain risk-assessment mechanisms due to occasional predation. Differences in escape between dendrobatids and palatable Craugastor frogs suggest that dendrobatid defensive behavior may have been molded to maximize the effectiveness of aposematism.

Effects of sex and microhabitat structure on escape behaviour in the diurnal gecko Gonatodes albogularis

2016 ◽  
Vol 66 (1) ◽  
pp. 31-47 ◽  
Author(s):  
Moisés E. Domínguez-López ◽  
Francisco J. Diego-Rasilla ◽  
Ángela M. Ortega-León
Keyword(s):  
Tropical Dry Forest ◽  
Structural Complexity ◽  
Dry Forest ◽  
Microhabitat Use ◽  
Flight Initiation Distance ◽  
Escape Behaviour ◽  
Escape Theory ◽  
Microhabitat Structure ◽  
The Cost ◽  
Flight Initiation

Flight initiation distance is defined as the distance between a prey and an approaching predator when the prey starts to flee. Escape theory predicts that the optimal flight initiation distance is the distance where predation risk rises to the point at which it equals the cost of fleeing. Therefore, staying close to refuge and occupying microhabitats with more abundant shelters (i.e., crevices or shrubs) may allow lizards to have shorter flight initiation distance. By simulating an approaching predator, we studied the effect of microhabitat structural complexity on escape behaviour, in particular, the distance fled before stopping and final distance (predator-prey distance when the prey stops fleeing), of a small diurnal tropical gecko, the yellow-headed geckoGonatodes albogularisinhabiting a tropical dry forest. The findings indicate that refuge abundance and distance to the nearest potential refuge influence escape behaviour ofG. albogularis. In addition, we found sex differences in escape behaviour which are not explained by microhabitat use. Females had longer flight initiation distance but shorter distance fled, and longer final distances than males.

The cost of homelessness: Assessing change over time

2003 ◽  
Author(s):  
M. Spano ◽  
P. Toro ◽  
M. Goldstein
Keyword(s):  
Change Over Time ◽  
The Cost ◽  
Over Time

The Internet Trap

2018 ◽  
Author(s):  
Matthew Hindman
Keyword(s):  
The Internet ◽  
Net Neutrality ◽  
The Public ◽  
Attention Economy ◽  
Digital News ◽  
The Cost ◽  
Over Time

The Internet was supposed to fragment audiences and make media monopolies impossible. Instead, behemoths like Google and Facebook now dominate the time we spend online—and grab all the profits from the attention economy. This book explains how this happened. It sheds light on the stunning rise of the digital giants and the online struggles of nearly everyone else—and reveals what small players can do to survive in a game that is rigged against them. The book shows how seemingly tiny advantages in attracting users can snowball over time. The Internet has not reduced the cost of reaching audiences—it has merely shifted who pays and how. Challenging some of the most enduring myths of digital life, the book explains why the Internet is not the postindustrial technology that has been sold to the public, how it has become mathematically impossible for grad students in a garage to beat Google, and why net neutrality alone is no guarantee of an open Internet. It also explains why the challenges for local digital news outlets and other small players are worse than they appear and demonstrates what it really takes to grow a digital audience and stay alive in today's online economy. The book shows why, even on the Internet, there is still no such thing as a free audience.

Value-based dentistry: Putting the patient first

2016 ◽  
Vol 7 (3) ◽  
pp. 126-129 ◽  
Author(s):  
Sreenivas Koka ◽  
Galya Raz
Keyword(s):  
Risk Management ◽  
Quality Improvement ◽  
Quality Of Care ◽  
Dental Care ◽  
Time Cost ◽  
Safety Risk ◽  
The Cost ◽  
Over Time

What does ‘value’ mean? In the context of dental care, it can be defined as the quality of care received by a patient divided by the cost to the patient of receiving that care. In other words: V =Q/C, where Q equals the quality improvement over time, which most patients view in the context of the outcome, the service provided and safety/risk management, and C equals the financial, biological and time cost to the patient. Here, the need for, and implications of, value-based density for clinicians and patients alike are explored.

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