Predator detection and avoidance by starlings under differing scenarios of predation risk

Practically all animals must find food while avoiding predators.An individual's perception of predation risk may depend on manyfactors, such as distance to refuge and group size, but it isunclear whether individuals respond to different factors ina similar manner. We tested whether flocks of foraging starlingsresponded in the same way to an increased perception of predationrisk by assessing three factors: (1) neighbor distances, (2)habitat obstruction, and (3) recent exposure to a predator.We found that in all three scenarios of increased risk, starlingsreduced their interscan intervals (food-searching bouts), whichincreased the frequency of their vigilance periods. We thenexamined how one of these factors, habitat obstruction, affectedescape speed by simulating an attack with a model predator.Starlings were slower to respond in visually obstructed habitats(long grass swards) and slower when they had their head downin obstructed habitats than when they had their head down inopen habitats. In addition, reaction times were quicker whenstarlings could employ their peripheral fields of vision. Ourresults demonstrate that different sources of increased riskcan generate similar behavioral responses within a species.The degree of visibility in the physical and social environmentaffects both the actual and perceived risk of predation.     

Behavioral response of 12 ungulate species in captivity to the presence of humans

Twelve species of captive ungulates were studied to determine behavioral responses to the presence of a zookeeper within the exhibit and in front of the exhibit, with and without zoo visitors present. Significant differences in behavior occurred between species for nearly all behaviors observed. A significantly greater occurrence of vigilance and approach behavior was directed toward the zookeeper while within the exhibit relative to when the zookeeper stood in front of the exhibit. A significantly lower occurrence of eating or drinking occurred when the zookeeper was inside the exhibit. Significant differences occurred across size categories in the occurrence of approaching the zookeeper. The most frequently scored behavior was visual orientation. Statistically significant differences in the occurrence of visual orientation directed by females toward the zookeeper existed across size category, with more vigilance by species with larger body size. A statistically higher occurrence of vigilance toward the zookeeper was directed by female ungulates but not by males when the zoo was closed to the public. Although no statistical significance was found regarding the intraspecific vigilance of males, data on females revealed significant differences across species and across size categories. When data regarding vigilance toward the public were analyzed, statistically significant differences existed between species for females only. Likewise, when data regarding interspecific vigilance were examined, statistically significant differences were found across size categories for females, but not for males. The potential roles of vigilance in the wild are discussed in reference to its role in captivity.     

Vigilance behavior during the birth and lactation season in naturally occurring ring-tailed lemurs (Lemur catta) at the Beza-Mahafaly Reserve,Madagascar

I examined the vigilance behavior of adult males and females in two groups of ring-tailed lemurs(Lemur catta)during the birth and lactation season at the Beza-Mahafaly Reserve, southwestern Madagascar. I found no sex difference with respect to the rates of overall vigilance, rates of vigilance toward a potential predator or unfamiliar sound, or rates of vigilance toward conspecifics from other social groups, nor were there sex differences in the percentage of time spent vigilant in any of the above categories. Higher-ranking females were vigilant significantly more often toward predators or potential predators than lower-ranking females were. I detected no relationship between vigilance behavior and dominance rank among adult males. The alpha female in each group exhibited significantly more vigilance behavior than all other members of her group. It was predicted that males should exhibit more vigilance behavior than females do, particularly during the birth and lactation season, when predator pressure is high, if they are benefiting females in this respect. I discuss the results in the context of this prediction and in terms of how ring-tailed lemur males benefit females, and why they may be tolerated in social groups.     

Consistent contrast between eyelid and iris brightness supports a role for vigilance signalling in ducks

Signalling self‐ability to maintain vigilance may help in securing a mate, while providing accurate information about vigilance status may result in conspecifics adjusting their own scanning rate of the environment, potentially to the individual's benefit. In birds, vigilance is often associated with head‐up postures adopted within a bout of head‐down activity, and this can be used by conspecifics to assess the vigilance of their flock mates. However, vigilance behaviour is not always obvious and other cues may then be used to assess vigilance rates of conspecifics. Here we assess whether iris/eyelid/face patterns from 43 duck species are consistent with the hypothesis that eyelid brightness has evolved so as to contrast with iris brightness, which may then help in signalling individual vigilance status. Ducks generally flock when resting during the day, and because of their wide visual fields, individuals can monitor their environment while remaining in a resting head‐down position. Ducks also show a wide variety of plumage and iris patterns, with both light‐headed and dark‐headed species. Matching our prediction, most ducks with dark irises had pale eyelids, irrespective of head colour. Furthermore, the smaller number of species with a pale iris generally have darker eyelids. A phylogenetic analysis shows a clear and significant association in the evolution of eyelid and iris brightness patterns in both males and females. These data therefore provide support for the hypothesis that eyelid brightness has evolved to act as a contrast with iris brightness. Further studies are now needed to examine the extent to which and the way this is used in vigilance information transfer between individuals.     

Disturbance and predation risk influence vigilance synchrony of black‐necked cranes Grus nigricollis,but not as strongly as expected

Animals monitor surrounding dangers independently or cooperatively (synchronized and coordinated vigilance), with independent and synchronized scanning being prevalent. Coordinated vigilance, including unique sentinel behavior, is rare in nature, since it is time‐consuming and limited in terms of benefits. No evidence showed animals adopt alternative vigilance strategies during antipredation scanning yet. Considering the nonindependent nature of both synchronization and coordination, we assessed whether group members could keep alert synchronously or in a coordinated fashion under different circumstance. We studied how human behavior and species‐specific variables impacted individual and collective vigilance of globally threatened black‐necked cranes (Grus nigricollis) and explored behavior‐based wildlife management. We tested both predation risk (number of juveniles in group) and human disturbance (level and distance) effects on individual and collective antipredation vigilance of black‐necked crane families. Adults spent significantly more time (proportion and duration) on scanning than juveniles, and parents with juveniles behaved more vigilant. Both adults and juveniles increased time allocation and duration on vigilance with observer proximity. Deviation between observed and expected collective vigilance varied with disturbance and predation risk from zero, but not significantly so, indicating that an independent vigilance strategy was adopted by black‐necked crane couples. The birds showed synchronized vigilance in low disturbance areas, with fewer juveniles and far from observers; otherwise, they scanned in coordinated fashion. The collective vigilance, from synchronized to coordinated pattern, varied as a function of observer distance that helped us determine a safe distance of 403.75 m for the most vulnerable family groups with two juveniles. We argue that vigilance could constitute a prime indicator in behavior‐based species conservation, and we suggesting a safe distance of at least 400 m should be considered in future tourist management.     

Sleep,Sleepiness, and Neurobehavioral Performance While on Watch in a Simulated 4 Hours on/8 Hours off Maritime Watch System

Seafarer sleepiness jeopardizes safety at sea and has been documented as a direct or contributing factor in many maritime accidents. This study investigates sleep, sleepiness, and neurobehavioral performance in a simulated 4?h on/8?h off watch system as well as the effects of a single free watch disturbance, simulating a condition of overtime work, resulting in 16?h of work in a row and a missed sleep opportunity. Thirty bridge officers (age 30?±?6 yrs; 29 men) participated in bridge simulator trials on an identical 1-wk voyage in the North Sea and English Channel. The three watch teams started respectively with the 00–04, the 04–08, and the 08–12 watches. Participants rated their sleepiness every hour (Karolinska Sleepiness Scale [KSS]) and carried out a 5-min psychomotor vigilance test (PVT) test at the start and end of every watch. Polysomnography (PSG) was recorded during 6 watches in the first and the second half of the week. KSS was higher during the first (mean?±?SD: 4.0?±?0.2) compared with the second (3.3?±?0.2) watch of the day (p?<?0.001). In addition, it increased with hours on watch (p?<?0.001), peaking at the end of watch (4.1?±?0.2). The free watch disturbance increased KSS profoundly (p?<?0.001): from 4.2?±?0.2 to 6.5?±?0.3. PVT reaction times were slower during the first (290?±?6?ms) compared with the second (280?±?6?ms) watch of the day (p?<?0.001) as well as at the end of the watch (289?±?6?ms) compared with the start (281?±?6?ms; p?=?0.001). The free watch disturbance increased reaction times (p?<?0.001) from 283?±?5 to 306?±?7?ms. Similar effects were observed for PVT lapses. One third of all participants slept during at least one of the PSG watches. Sleep on watch was most abundant in the team working 00–04 and it increased following the free watch disturbance. This study reveals that—within a 4?h on/8?h off shift system—subjective and objective sleepiness peak during the night and early morning watches, coinciding with a time frame in which relatively many maritime accidents occur. In addition, we showed that overtime work strongly increases sleepiness. Finally, a striking amount of participants fell asleep while on duty.     

Time to wake up: No impact of COMT Val158Met gene variation on circadian preferences,arousal regulation and sleep

Dopamine has been implicated in the regulation of sleep–wake states and the circadian rhythm. However, there is no consensus on the impact of two established dopaminergic gene variants: the catechol-O-methyltransferase Val158Met (COMT Val158Met; rs4680) and the dopamine D4 receptor Exon III variable-number-of-tandem-repeat polymorphism (DRD4 VNTR). Pursuing a multi-method approach, we examined their potential effects on circadian preferences, arousal regulation and sleep. Subjects underwent a 7-day actigraphy assessment (SenseWear Pro3), a 20-minute resting EEG (analyzed using VIGALL 2.0) and a body mass index (BMI) assessment. Further, they completed the Morningness–Eveningness Questionnaire (MEQ), the Epworth Sleepiness Scale (ESS) and the Pittsburgh Sleep Quality Index (PSQI). The sample comprised 4625 subjects (19–82 years) genotyped for COMT Val158Met, and 689 elderly subjects (64–82 years) genotyped for DRD4 VNTR. The number of subjects varied across phenotypes. Power calculations revealed a minimum required phenotypic variance explained by genotype ranging between 0.5% and 1.5% for COMT Val158Met and between 3.3% and 6.0% for DRD4 VNTR. Analyses did not reveal significant genotype effects on MEQ, ESS, PSQI, BMI, actigraphy and EEG variables. Additionally, we found no compelling evidence in sex- and age-stratified subsamples. Few associations surpassed the threshold of nominal significance (p < .05), providing some indication for a link between DRD4 VNTR and daytime sleepiness. Taken together, in light of the statistical power obtained in the present study, our data particularly suggest no impact of the COMT Val158Met polymorphism on circadian preferences, arousal regulation and sleep. The suggestive link between DRD4 VNTR and daytime sleepiness, on the other hand, might be worth investigation in a sample enriched with younger adults.     

Individuals in foraging groups may use vocal cues when assessing their need for anti-predator vigilance

Many studies of social species have reported variation in the anti-predator vigilance behaviour of foraging individuals depending on the presence and relative position of other group members. However, little attention has focused on how foragers assess these variables. It is commonly assumed that they do so visually, but many social species produce frequent calls while foraging, and these 'close' calls might provide valuable spatial information. Here, we show that foraging pied babblers (Turdoides bicolor) are less vigilant when in larger groups, in the centre of a group and in closer proximity to another group member. We then show that foragers are less vigilant during playbacks of close calling by more individuals and individuals on either side of them when compared with calls of fewer individuals and calls on one side of them. These results suggest that foragers can use vocal cues to gain information on group size and their spatial position within a group. Future studies of anti-predator vigilance should consider the relative importance of both visual and vocal monitoring of group members.     

Impact of increased predation risk on vigilance behaviour in a gregarious waterfowl,the Egyptian goose Alopochen aegyptiaca

Vigilance is amongst the most universal of anti‐predator strategies and commonly declines with increasing group size. We experimentally manipulated predation risk in a system with a known relationship between group size and vigilance levels to explore whether this relationship changes in response to elevated predation risk. We investigated the vigilance levels of Egyptian geese Alopochen aegyptiaca at eight golf courses in the western Cape, South Africa, to assess the perception of and reaction to predation risk. We manipulated predation risk by introducing trained Harris's hawks Parabuteo unicintus where avian predation was otherwise low or absent. The study confirmed the typical reduction in vigilance with group size on control sites, where the risk of predation is low. However, at experimental sites with elevated predation risk, a positive relationship between vigilance and group size was observed. We hypothesize that the mechanism for this relationship might be linked to social information transfer via copying behaviour and manipulation to induce vigilance. Thus, larger groups will have a higher probability of containing individuals with experience of elevated predation risk and their increased vigilance behaviour is copied by naïve individuals. This prediction is based on the intended outcome of introducing avian predation to make the geese feel less safe and to eventually leave the site as a management tool for controlling nuisance geese.