Effects of predation risk factors on escape behavior by Balearic lizards (Podarcis lilfordi) in relation to optimal escape theory

2009 ◽  
Vol 30 (1) ◽  
pp. 99-110 ◽  
Author(s):  
Dror Hawlena ◽  
Valentín Pérez-Mellado ◽  
William Cooper
Keyword(s):  
Risk Factors ◽  
Predation Risk ◽  
Escape Behavior ◽  
Weather Conditions ◽  
Predator Prey ◽  
Escape Theory ◽  
Approach Speed ◽  
Podarcis Lilfordi ◽  
Effects Of Temperature ◽  
Flight Initiation

AbstractEscape theory predicts that flight initiation distance (FID = predator-prey distance when escape begins) increases as predation risk increases. We tested effects of variation of approach speed and directness, predator persistence, concealment, and weather conditions on FID in the Balearic lizard (Podarcis lilfordi) by ourselves simulating predators. We examined effects of directness of approach on probability of fleeing and of repeated approach on entering refuge and distance fled. As predicted, FID was greater for faster approach speed, more direct approach, during second than first approaches, and when lizards were exposed than partially concealed. Other effects of directness of approach and repeated approach also were as predicted by greater assessed risk by the lizards. The proportion of individuals that fled was greater for direct than indirect approaches. The proportion of lizards that entered refuges and distance fled were greater during the second of two successive approaches. Effects of weather on FID were complex. FID was shortest in the warmest conditions with no noticeable wind, when lizards were active. Lizards were inactive and basked in the other conditions. FID was longest at 20°C without wind, and intermediate FID occurred at 18°C in windy conditions. We present hypotheses for weather effects. Tests are needed to unravel effects of temperature and wind speed. All predictions of escape theory for simple risk factors, i.e., all except than weather conditions, were confirmed. Escape theory successfully predicts FID for these risks in P. lilfordi, other lacertids, and more broadly, in ecologically and taxonomically diverse lizards.

Stop-and-go approach by a predator: a novel predation risk factor for the phrynosomatid lizards Sceloporus virgatus and Callisaurus draconoides

2015 ◽  
Vol 36 (4) ◽  
pp. 401-409
Author(s):  
William E. Cooper ◽  
Wade C. Sherbrooke
Keyword(s):  
Field Experiments ◽  
Empirical Studies ◽  
Pause Duration ◽  
Predator Prey ◽  
Escape Theory ◽  
Stop And Go ◽  
Approach Speed ◽  
Sceloporus Virgatus ◽  
Escape Behaviors ◽  
Flight Initiation

As an immobile prey monitors an approaching predator, the predator may move at a constant speed directly toward the prey or on a path that bypasses the prey. These scenarios have been studied extensively. Economic escape theory successfully predicts flight initiation distance (FID = predator-prey distance when escape begins). However, predators often alter their speed and may exhibit stops and starts during approaches. Empirical studies have shown that prey rapidly adjust assessed risk to a predator’s changes in approach speed and direction, but effects of interrupted (stop-start) approach are unknown. Because a prey is likely to assess that a nearby predator that resumes approaching has detected it and is attacking, escape theory predicts that assessed risk is greater at a given predator-prey distance when approach resumes than is continuous. Therefore, we predicted that FID is longer when a predator approaches, stops nearby, and renews its approach than when it approaches continuously. Second, although assessed risk increases as duration of the predator’s stop nearby increases, as indicated by latency to flee, we predicted that pause duration does not affect FID because prey interpret resumed approach as attack. Field experiments with two lizards, Sceloporus virgatus and Callisaurus draconoides, verified the predictions: FID was longer for discontinuous than continuous approaches and pause duration did not affect FID. We also observed distance fled and probability of entering refuge, escape behaviors for which theory is undeveloped. Distance fled was unrelated to continuity of approach in both species, as was refuge entry in S. virgatus.

Beyond optimal escape theory: microhabitats as well as predation risk affect escape and refuge use by the phrynosomatid lizard Sceloporus virgatus

Behaviour ◽  
2007 ◽  
Vol 144 (10) ◽  
pp. 1235-1254 ◽  
Author(s):  
Dawn Wilson ◽  
William Cooper
Keyword(s):  
Risk Factors ◽  
Individual Differences ◽  
Predation Risk ◽  
Flight Initiation Distance ◽  
Refuge Use ◽  
Escape Theory ◽  
Sceloporus Virgatus ◽  
Flight Initiation

AbstractEscape studies often focus on one variable, but tactics and refuge use vary with microhabitats, exposure, distance to refuge, and temperature. We studied these effects and effects of microhabitats and risk factors (distance from refuge, temperature) on flight initiation distance (FID, distance between predator and prey when escape begins) and distance fled (DF) in the lizard Sceloporus virgatus. FID increased as distance to refuge increased and temperature decreased. DF increased as FID increased, supporting the hypothesis that individual differences in boldness are consistent among encounter phases. Refuges were rock crevices, trees, logs, and grass clumps. Interhabitat differences in FID and DF matched those in distance to refuge. FID was longer for lizards on rocks and ground than trees due to proximity to and use of refuge. Lizards on trees rarely changed microhabitats, moving to the far side and unpredictably up or down. Lizards on slopes fled long distances up slopes. Most lizards on rocks entered crevices or switched microhabitats. Lizards on ground usually changed microhabitats. Optimal escape theory accurately predicted effects of risk on FID, but initial microhabitats and final microhabitats and refuges affected tactics, FID and DF. DF was affected by risk, being longer when lizards remained visible.

Risk factors and escape strategy in the grasshopper Dissosteira carolina

Behaviour ◽  
2006 ◽  
Vol 143 (10) ◽  
pp. 1201-1218 ◽  
Author(s):  
William E. Cooper
Keyword(s):  
Risk Factors ◽  
Field Experiments ◽  
Escape Behavior ◽  
Sudden Change ◽  
Flight Initiation Distance ◽  
Initial Direction ◽  
Escape Strategy ◽  
Approach Speed ◽  
Lateral Escape ◽  
Flight Initiation

AbstractTo determine aspects of escape strategy by the Carolina grasshopper, Dissosteira carolina, and applicability of models of escape behavior applied primarily to vertebrates, I conducted three field experiments by simulating an approaching predator. Escape theory predicts that flight initiation distance (distance from predator when escape begins) and distance fled increase as predation risk increases. Some aspects of escape are not predicted, and theory does not identify escape strategies including several components. I examined effects of risk factors (predator approach speed, directness of approach, and repeated approach) on flight initiation distance, distance fled, and the initial direction of escape. Flight initiation distance and distance fled were predicted to increase with approach speed. Because predators approaching directly may bypass prey without detecting it, probability of fleeing and flight initiation distance were predicted to increase with directness of approach. Because a persistent predator poses greater threat, flight initiation distance and distance fled were predicted to be greater for the second of two successive approaches. All findings were consistent with predictions of the Ydenberg & Dill (1986) model, suggesting that risk assessment and escape decisions by visually oriented insects may be similar to those of vertebrates. Although escape directly away from the predator might be expected to minimize risk, most grasshoppers escaped by flying at nearly right angles to the approach path. Lateral escape may be part of an escape strategy in which dark wing colour during flight rapidly disappears upon landing. With sudden change in colour and movement, the grasshopper becomes cryptic and difficult to relocate. Lateral escape may increase difficulty of maintaining visual contact with the grasshopper until it lands. It also avoids need for further escape from a predator that continues in its initial direction.

Predation risk, escape and refuge use by mountain spiny lizards (Sceloporus jarrovii)

2010 ◽  
Vol 31 (3) ◽  
pp. 363-373 ◽  
Author(s):  
Arián Avalos ◽  
William Cooper, Jr.
Keyword(s):  
Risk Factors ◽  
Predation Risk ◽  
Additive Effects ◽  
Flight Initiation Distance ◽  
Refuge Use ◽  
Economic Theories ◽  
Approach Speed ◽  
Theoretical Predictions ◽  
Expected Fitness ◽  
Flight Initiation

AbstractEconomic theories of antipredatory behavior take into account expected fitness losses and gains to predict escape decisions. Prey at greater risk are predicted to have longer flight initiation distance (= distance from predator when escape begins), flee farther, be more likely to enter refuge, and have longer hiding time (= time between entering and exiting refuge). We simulated predators to study effects of risk factors in the lizard Sceloporus jarrovii. Flight initiation distance, distance fled and probability of entering refuge increased with approach speed. Flight initiation distance increased additively with increases in speed and directness of approach. Lizards habituated to human presence had shorter flight initiation distances than unhabituated lizards. As predicted from greater threat posed by a persistent predator, flight initiation distance and hiding time were longer after the second of two approaches. Fleeing was more likely when an investigator stood nearby and turned toward them than when farther way or turned away. These findings verify theoretical predictions of escape and refuge use for several risk factors and most are consistent with those for other lizards. However, speed and directness of approach had additive effects in S. jarrovii, but interacted in other species. Another novel finding was a small interaction between individual investigator and directness of approach. Although outcomes of tests of escape and refuge use theories consistently confirm qualitative predictions, quantitative comparisons between studies by different investigators may have limited value unless information is available about relative responses by prey to each investigator.

scholarly journals Optimal escape theory predicts escape behaviors beyond flight initiation distance: risk assessment and escape by striped plateau lizards Sceloporus virgatus

2009 ◽  
Vol 55 (2) ◽  
pp. 123-131 ◽  
Author(s):  
William E. Cooper
Keyword(s):  
Risk Factors ◽  
Risk Assessment ◽  
Predation Risk ◽  
Flight Initiation Distance ◽  
Risk Levels ◽  
Escape Theory ◽  
Growing Body ◽  
Sceloporus Virgatus ◽  
Escape Behaviors ◽  
Flight Initiation

Abstract Escape theory predicts that flight initiation distance (FID = distance between predator and prey when escape begins) is longer when risk is greater and shorter when escape is more costly. A few tests suggest that escape theory applies to distance fled. Escape models have not addressed stochastic variables, such as probability of fleeing and of entering refuge, but their economic logic might be applicable. Experiments on several risk factors in the lizard Sceloporus virgatus confirmed all predictions for the above escape variables. FID was greater when approach was faster and more direct, for lizards on ground than on trees, for lizards rarely exposed to humans, for the second of two approaches, and when the predator turned toward lizards rather than away. Lizards fled further during rapid and second consecutive approaches. They were more likely to flee when approached directly, when a predator turned toward them, and during second approaches. They were more likely to enter refuge when approached rapidly. A novel finding is that perch height in trees was unrelated to FID because lizards escaped by moving out of sight, then moving up or down unpredictably. These findings add to a growing body of evidence supporting predictions of escape theory for FID and distance fled. They show that two probabilistic aspects of escape are predictable based on relative predation risk levels. Because individuals differ in boldness, the assessed optimal FID and threshold risks for fleeing and entering refuge are exceeded for an increasing proportion of individuals as risk increases.

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.

Risk factors affecting escape behavior by the desert iguana, Dipsosaurus dorsalis: speed and directness of predator approach, degree of cover, direction of turning by a predator, and temperature

2003 ◽  
Vol 81 (6) ◽  
pp. 979-984 ◽  
Author(s):  
W E Cooper Jr.
Keyword(s):  
Risk Factors ◽  
Body Temperature ◽  
Escape Behavior ◽  
Primary Response ◽  
Single Individual ◽  
Factors Affecting ◽  
Escape Theory ◽  
Approach Distance ◽  
Dipsosaurus Dorsalis ◽  
Air Temperatures

Escape from predators by desert iguanas (Dipsosaurus dorsalis) conforms to predictions of optimal escape theory based on risk. I simulated an approaching predator to study risk factors. The primary response variable was approach distance (= flight-initiation distance), i.e., the distance between predator and prey when the prey initiates escape. In additional studies, I recorded whether lizards permitted me to approach close enough to noose them (an indicator of wariness) and the method of escape. Approach distance was greater when the predator approached rapidly than slowly and directly than indirectly, and when the predator turned toward the lizard rather than away. It was greater in open than in more densely covered habitats, which may reflect greater risk due to conspicuousness and (or) a greater distance to refuge. Early in the day at lower air temperatures, desert iguanas permitted a closer approach before initiating escape. While basking after emergence from burrows, lizards escaped into burrows; later in the day they fled. Lizards that fled had high body temperatures; a single individual captured immediately after entering a burrow had a lower body temperature. Lizards presumably enter burrows when low body temperature limits the running speed, but burrow use is costly because attainment of the activity temperature is delayed because of time elapsed and the temperature decrease in burrows.

Effects of recent movement, starting distance and other risk factors on escape behaviour by two phrynosomatid lizards

Behaviour ◽  
2013 ◽  
Vol 150 (5) ◽  
pp. 447-469 ◽  
Author(s):  
William E. Cooper ◽  
Wade C. Sherbrooke
Keyword(s):  
Risk Factors ◽  
Cost Benefit ◽  
Escape Behaviour ◽  
Predator Prey ◽  
Recent Movement ◽  
Approach Speed ◽  
Variable Distance ◽  
The Cost ◽  
Risk Assessment Mechanism ◽  
Similar Risk

Cost–benefit models of escape behaviour predict that flight initiation distance (FID, predator-prey distance when the prey starts to flee from an approaching predator) increases as the cost of not fleeing (risk) increases. This prediction has been verified for many risk factors and prey species. The same predictions may apply to other aspects of escape, but testing has been much less extensive. For the lizards Callisaurus draconoides and Sceloporus magister, we tested several such predictions and examined the effect of a previously unstudied risk factor, recent movement by prey. Starting distance (predator-prey distance when approach begins) was unrelated to FID in C. draconoides, as in previously studied ambush foragers. Because movement increases probability of being detected, we predicted that FID would be greater for prey that had moved immediately before being approached than those that had been immobile. FID and distance fled (DF) were longer for lizards that had moved recently. In C. draconoides DF and probability of entering refuge were greater for the second of two approaches, as predicted from greater threat posed by a persistent predator. Callisaurus draconoides had shorter FID and shorter DF, and fewer entered refuge where lizards were habituated than unhabituated to human presence. In S. magister FID increased as distance to refuge increased, FID and DF were longer for fast than slow approaches; probability of fleeing and FID were larger for direct than indirect approach. Effects of these risk factors on FID are consistent across studies, but approach speed has affected DF in only half of studies, perhaps due to constraints by refuge entry and variable distance to refuge. Similarities in effects of risk factors across escape variables, types of predator-prey encounters, and latency to emerge from refuge suggest that similar risk assessment mechanism are used for all variables and settings.

scholarly journals Empirical studies of escape behavior find mixed support for the race for life model

2021 ◽  
Author(s):  
Kwasi Wrensford ◽  
Jahaziel Gutierrez ◽  
William E Cooper ◽  
Daniel T Blumstein
Keyword(s):  
Escape Behavior ◽  
Empirical Studies ◽  
Relative Orientation ◽  
Similar Amount ◽  
Predator Prey ◽  
Future Studies ◽  
Escape Theory ◽  
Mixed Support ◽  
Life Model ◽  
The Relationship

Abstract Escape theory has been exceptionally successful in conceptualizing and accurately predicting effects of numerous factors that affect predation risk and explaining variation in flight initiation distance (FID, predator-prey distance when escape begins). Less explored is the relative orientation of an approaching predator, prey, and its eventual refuge. The relationship between an approaching threat and its refuge can be expressed as an angle we call the “interpath angle” or “Φ”, which describes the angle between the paths of predator and prey to the prey’s refuge and thus expresses the degree to which prey must run towards an approaching predator. In general, we might expect that prey would escape at greater distances if they must flee toward a predator to reach its burrow. The ‘race for life’ model makes formal predictions about how interpath angle should affect FID. We evaluated the model by studying escape decisions in yellow-bellied marmots Marmota flaviventer, a species which flees to burrows. We found support for some of the model’s predictions, yet the relationship between interpath angle and FID was less clear. Marmots may not assess interpath angle in a continuous fashion; but we found that binning angle into four 45° bins explained a similar amount of variation as models that analyzed angle continuously. Future studies of interpath angle, especially those that focus on how different species perceive relative orientation, will likely enhance our understanding of its importance in flight decisions.

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