Individual Vigilance Research Articles

Plains zebras bring evidence that dilution and detection effects may not always matter behaviorally and demographically

AbstractGroup living is assumed to benefit prey by reducing predation risk due to dilution and detection effects. This increased safety could be exchanged against a reduced individual vigilance leading to increased foraging and fitness until costs of intra‐group competition offset this benefit. However, very few studies have been able to directly test the relationship between individual fitness and group size in non‐cooperative breeding species. Therefore, evidence that dilution and detection effects do indeed translate into increased fitness under predation risk remains mostly theoretical. Here, we aimed at empirically testing whether group size influences beneficial and costly behaviors, and ultimately the survival of individuals, in a prey species facing heavy predation pressure. We focused on plains zebra Equus quagga of Hwange National Park in Zimbabwe, a high lion density area. We collected behavioral data (i.e., individual vigilance and foraging, collective vigilance, and agonistic interactions) that we used as proxies to investigate the costs and benefits of grouping in this species. We then fitted multistate capture‐mark‐recapture and Cox proportional‐hazards models to estimate apparent survival of adults and young zebras, respectively, and assess whether a demographic signal of group size could be found. Our results show that collective vigilance increases with group size, a prerequisite of the detection effect, but individual vigilance does not consistently decrease with group size, which suggests that there is no group size effect on individual vigilance. Agonistic interactions were rare. These results suggest that there are no foraging costs of grouping here, and even some benefits such as a better collective vigilance. However, any benefits of being in larger groups did not translate into increased survival, as we found no effect of group size on the apparent survival of individuals. Since dilution and detection effects do not matter behaviorally and demographically in these plains zebras living under high predation risk, these results challenge our understanding of how predation shapes animal sociality: fitness benefits of dilution or detection should not be assumed.

Attention, impulsivity, and vigilance in agenesis of the corpus callosum.

Questions regarding the role of the corpus callosum in attention are raised by the reports of attention problems in some persons with agenesis of the corpus callosum (AgCC), as well as by abnormalities in callosal size in persons with attention-deficit/hyperactive disorder. The current study assessed inattention, impulsivity, and vigilance in individuals with AgCC. These domains of attention were assessed using the Conners' Continuous Performance Test II in 18 older adolescents and adults (ages 16-52) with complete AgCC and normal intelligence (full scale intelligence quotient > 80). Scores were converted to T scores using age-specific norms and assessed for departure from the normative sample. Scores were significantly elevated in older adolescents with AgCC for errors of commission (p = .050, d = 0.55) and detectability (p = .03, d = 0.58). Older adolescents were worse than adults for commissions (p = .06, ηp² = .201) and detectability (p = .03, ηp² = .273). Also, male individuals had significantly higher (worse) scores than did female in vigilance (p = .01, ηp² = .337). These results suggest moderate levels of difficulties in sustained attention in AgCC, particularly in maintaining response inhibition and in vigilance, that are modulated by age and sex. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Sleeping Eurasian oystercatchers adjust their vigilance in response to the behaviour of neighbours, human disturbance and environmental conditions

AbstractVigilance is a costly behaviour but it enables animals to detect and avoid threats of predation and intraspecific competition. To compensate for the increased risk while sleeping, many bird species have evolved eye‐blinking strategies called peeking, which allows vigilance to persist in a sleep‐like state. However, the drivers of vigilance behaviour during sleep have rarely been explored. We investigated how social factors, anthropogenic disturbance and environmental conditions affected the sleep‐vigilance trade‐off in the Eurasian oystercatcher (Haematopus ostralegus). Data were collected on the frequency, total duration and average duration of peeking at two locations on the Menai Strait, North Wales. Our results reveal that exposure to anthropogenic disturbance, particularly the presence of people exercising dogs, led to an increase in vigilance duration and reduced time sleeping, while increasing boat traffic resulted in elevated levels of peek frequency, but the overall duration of vigilance was in fact reduced. Furthermore, oystercatchers adjust their vigilance behaviour according to social context, with reduced levels of individual vigilance when a greater number of animals were present. However, if surrounding neighbours were awake – then the observed animal was more likely to be alert, demonstrating the importance of monitoring the behaviour of conspecifics. Likewise, the temperature and wind speed influenced vigilance with elevated levels of peek frequency observed in warmer and windier conditions. Oystercatchers are able to make fine‐scale adjustments to their vigilance behaviour while asleep, which reduces the risk of external threats such as predators. Nevertheless, they are making these decisions against the backdrop of a finely balanced energy budget, particularly during the winter months. Increased levels of human activity and disturbance may elevate the costs of vigilance and ultimately have fitness implications for this species.

Vigilance strategy differentiation between sympatric threatened and common crane species

Studies have indicated that threatened species may show reduced or elevated antipredator behavior compared with their close common relatives, but remarkably few studies revealed such differences in behavior among populations. Exploring factors affecting behavior between phylogenetically related common and threatened species could help understand such discrepancy. We tested for effects of external and internal variables including month, time of day, habitat type, distribution area, group composition status and group size on vigilance behavior (including group scan frequency and level) of two sympatric common Grus grus and threatened G. nigricollis cranes with generalized linear models. We detected significant species effect on group scan level, and grus was more vigilant than nigricollis. Model tests also indicated that group size had common effect on group scan frequency for both species, and distribution area significantly correlated with the vigilance of nigricollis, while grus was more affected by time of day and group composition status in areas of sympatry with nigricollis. But when nigricollis was absent, time had no effects on behavior by individuals belonging to grus, implying existence of inter-specific competition. We also found that grus decreased individual vigilance efforts by foraging with other species (e.g., Bar-headed Goose Anser indicus) to share large group alertness benefits (collective vigilance). As our results demonstrated, we argued that, with diverse antipredation tactics e.g., foraging with other species, alternating time rhythm or partitioning spatial utilization to mitigate inter-specific competition, reducing time allocation to preening while maintaining foraging efforts, common grus could maintain high level of vigilance, which may benefit their survival and population increase. Whereas less time spent vigilant antipredation strategy adopted by threatened nigricollis, this may have negative effects on their populations.

Self-disgust, loneliness and mental health outcomes in older adults: An eye-tracking study

BackgroundSelf-disgust has been associated with loneliness and mental health difficulties in clinical and non-clinical populations, but there is limited research on the role of self-disgust in loneliness and mental health outcomes in older adults. MethodsIn Study 1 (N = 102; M age = 68.4 years, SD = 10.9, 68% females) we used a cross-sectional survey to explore the association between loneliness, self-disgust and mental health outcomes. In Study 2 (N = 80; M age = 68.8 years, SD = 11.4, 57% females) we used eye-tracking to investigate attentional vigilance, maintenance and avoidance in individuals with high (vs. low) self-disgust. ResultsIn study 1 we found that self-disgust mediated the associations of loneliness with anxiety and depressive symptoms, and in study 2 it was demonstrated that older adults with high (vs. low) self-disgust displayed attentional avoidance to their own faces, compared to the faces of unknown others, a process that may perpetuate loneliness. LimitationsThe cross-sectional design used in Study 1 limits our potential to make causal inferences. Additionally, both studies included a wide age range of older adults. ConclusionsOur findings are novel and highlight the importance of self-disgust experiences in the context of loneliness and mental health outcomes in older adults. Implications for practice and interventions against loneliness in this age group are discussed.

Effect of group size and reproductive status on faecal glucocorticoid concentration and vigilance in a free-ranging population of Przewalski's gazelle.

Elevated glucocorticoid (GC) concentration and increased vigilance are two common responses to predation risk in mammals. Chronic high-level GC concentration and vigilance occur at the expense of other life maintenance and reproduction activities, reflecting a trade-off between individual survival and future fecundity. Przewalski’s gazelle (Procapra przewalskii) is a group-living ungulate endemic to the high-altitude Qinghai Lake region of China. Group-size effect on gazelle vigilance has been examined, yet little is known about how their GC concentration is affected by group size or reproductive status. In this study, we examined the effect of group size and reproductive status on faecal glucocorticoid metabolite (FGM) concentrations and individual vigilance during different stages of the reproduction cycle (i.e. non-breeding, lambing and rutting) in free-ranging adult female Przewalski’s gazelles. Group size did not influence FGMs significantly, but mean vigilance duration increased with group size. The gazelles’ FGMs and vigilance peaked in lambing season. FGMs showed no difference between rutting season and non-reproductive season, but vigilance was lowest in the rutting season. FGMs correlated with vigilance frequency and vigilance duration. Antipredator responses of female Przewalski’s gazelles appear to change with reproductive status but not with group size in free-ranging females. Management measures should be taken in the lambing season to minimize stress on mother gazelles.

Keeping safe and fed: large heterospecific shorebird flocks to decrease intraspecific competition

Shorebirds join cohesive flocks for safety. The joining of individuals of several species in large heterospecific flocks can optimise individual vigilance and foraging. However, a large number of conspecific individuals in flocks may deplete food resources and increase intraspecific competition. In the present study, we argue that Nearctic–Neotropical migratory shorebird species join large heterospecific flocks in a balanced number as a way of controlling intraspecific competition. We recorded monospecific and heterospecific flocks in urban beaches from southeastern Brazil and annotated the species richness and the number of individuals per bird species per flock. Besides, we recorded the number of people around shorebird flocks to examine any relationship with flock size. We also recorded the foraging rate of the semipalmated plover Charadrius semipalmatus, a common migrant species in the region, as a species model to test competition and vigilance. We hypothesised that this species would exhibit a low foraging rate in scenarios with high intraspecific competition (i.e. large flocks with a high number of conspecifics) and high density of people, which may disturb birds. In the initial results, the density of people did not influence size of monospecific and heterospecific flocks; heterospecific flocks were larger than monospecific flocks, and heterospecific flocks increased in size by the addition of more species rather than more individuals of the same species. These data reflect a decrease in the relative abundance of individuals per species. Additionally, the semipalmated plover foraging rate was reduced in monospecific flocks, flocks with a high relative abundance (and total number) of the specific individuals and flocks surrounded by a high density of people. All these results indicate that shorebirds may adjust flock composition and size according to preferred foraging conditions, i.e. large and balanced heterospecific flocks with less intraspecific competition and less vigilance to potential predators in wintering areas.

Watch out! Insecure relationships affect vigilance in wild spider monkeys (Ateles geoffroyi)

Vigilance is used to monitor extra-group threats as well as risky group members. We examined whether relationship quality affects vigilance patterns of spider monkeys. We used focal animal sampling to collect data on social interactions and individual vigilance of all adults and subadults (N = 22) in a community of well-habituated Geoffroy’s spider monkeys living in the protected area of Otoch Ma’ax Yetel Kooh, Yucatan, Mexico. Through a principal component analysis of seven indices of social interactions, we previously obtained three components of relationship quality, reflecting the levels of compatibility, value, and security. Such components could differentially affect vigilance depending on whether vigilance is directed to extra-group threats or risky group members. We tested whether an individual’s vigilance was affected by (1) the mean level of compatibility, the mean level of value and the mean level of security across subgroup members; (2) the lowest level of compatibility, the lowest level of value, and the lowest level of security with any subgroup member; and (3) the mean level of compatibility, the mean level of value, and the mean level of security with neighbors (i.e., subgroup members within 5 m). We did not find evidence for any effect of compatibility and value; however, security did affect vigilance, as individuals were more vigilant when they had a less secure relationship with the subgroup member with the lowest level of security or with the average neighbor. Vigilance for monitoring group members is common in primate species. We examined whether the quality of social relationships with subgroup members and neighbors modulates vigilance in wild spider monkeys. We used three components of relationship quality (reflecting the levels of compatibility, value, and security) and predicted each component would affect vigilance depending on whether vigilance was directed to extra-group threats or risky group members. We found no evidence that compatibility and value affected vigilance. However, an increase in vigilance occurred when spider monkeys had a less secure relationship with (1) the subgroup member with the lowest level of security and (2) the average neighbor. Our results show monitoring risky group members is an important component of vigilance, especially in species facing low predation pressure.

Increased neural reactivity to emotional pictures in men with high hair testosterone concentrations.

Testosterone has been linked to alterations in the activity of emotion neurocircuitry including amygdala, orbitofrontal cortex (OFC) and insula and diminished functional amygdala/prefrontal coupling. Such associations have only ever been studied using acute measures of testosterone, thus little is known about respective relationships with long-term testosterone secretion. Here, we examine associations between hair testosterone concentration (HTC), an index of long-term cumulative testosterone levels and neural reactivity during an emotional passive viewing task using functional magnetic resonance imaging (fMRI). Forty-six men viewed negative, positive and neutral pictures in the MRI. HTCs were assessed from 2 cm hair segments. The emotional paradigm elicited neural activation in the amygdala, insula and OFC. HTCs were associated with increased reactivity to negative pictures in the insula and increased reactivity to positive pictures in the OFC. We show an association of long-term testosterone levels with increased emotional reactivity in the brain. These results suggest a heightened emotional vigilance in individuals with high trait testosterone levels.

Number of neighbors instead of group size significantly affects individual vigilance levels in large animal aggregations

The group size effect states that animals living in groups gain anti‐predator benefits through reducing vigilance levels as group size increases. A basic assumption of group size effect is that all individuals are equally important for a focal individual, who may adjust its vigilance levels according to social information acquired from them. However, some studies have indicated that neighbors pose greater influences on an individual's vigilance decisions than other group members, especially in large aggregations. Vigilance has also been found to be directed to both predators (anti‐predation vigilance) and conspecifics (social vigilance). Central individuals might rely more on social vigilance than peripheral individuals. To test these hypotheses, we examined the effects of flock size, number of neighbors and position within a flock on vigilance and competition of greater white‐fronted goose Anser albifrons that form large foraging flocks in winter, controlling the effects of other variables (group identity, winter period and site). We found that individual vigilance levels were significantly affected by number of neighbors and position within a flock, whereas flock size showed no effect. Individuals devoted a large component of vigilance to nearby flock mates. Central individuals directed a relatively larger proportion of vigilance to monitor neighbors than peripheral ones, indicating that central individuals more relied on social information acquired from neighbors, possibly caused by the more blocked visual field of central individuals. Moreover, some social vigilance may function as conducting or preventing agonistic interactions since competition intensity was positively correlated with number of neighbors. Our study therefore demonstrate that the number of neighbors is more important than group size in determining individual vigilance in large animal groups. Further studies are still needed to unravel which neighbors pose greater influence on individual vigilance, and the factors that influence individuals to acquire information from their neighbors to adjust vigilance behaviors.

Group-enhanced predator detection and quality of vigilance in a social ground squirrel

Animals may form groups for different reasons, and one major benefit of grouping in many species is reduced predation risk. In diurnal species, vigilance is used to detect predators, resulting in a trade-off between feeding activity and predation risk. Species can reduce the cost of this trade-off with low-quality vigilance – performing another behaviour while vigilant – in comparison to high-quality vigilance (only being vigilant). Two nonmutually exclusive hypotheses explaining an inverse relationship between individual vigilance and group size are the dilution effect, where predation risk decreases in larger groups, and collective detection, where larger groups have more individuals that may detect a predator. Two predictions that support collective detection but not the dilution effect are that (1) overall group (collective) vigilance will increase with increasing group size, even while individual vigilance decreases, and (2) at least one group member must be vigilant to detect potential danger and communicate that information to group members. To test these predictions, we recorded behavioural data on low- and high-quality vigilance and alarm calling in the gregarious Barbary ground squirrel, Atlantoxerus getulus. Barbary ground squirrels allocated more time to high-quality vigilance than low-quality vigilance. The collective detection hypothesis was partly supported: as group size increased, individual low- and high-quality vigilance did not decrease, but collective high-quality vigilance did increase. Furthermore, we found that repetitive alarm calling warned group members of terrestrial threats. Our results show that this invasive species displays specific antipredator behaviours to different aerial and terrestrial predators compared to predators in their endemic range. The low level of time allocated to low-quality vigilance indicates that natural selection strongly favours high-quality vigilance in this species despite the trade-off with foraging. Our study broadens our understanding of antipredator and risk-sensitive behaviour.

Closed-loop application of tDCS to promote responsiveness in patients with disorders of consciousness

Transcranial direct current stimulation (tDCS) applied on the left dorsolateral prefrontal cortex has already been shown to efficiently promote the recovery of conscious awareness in patients with disorders of consciousness following severe brain injury, especially those in minimally conscious state (MCS). However, one potential barrier to clinically respond to tDCS is accounting for the timing of the stimulation with regard to the fluctuations of vigilance that characterize this population. Indeed, the vigilance of MCS patients has periodic average cycles of 70 minutes (range 57-80 minutes), potentially preventing them to be in an optimal neural state to benefit from tDCS when applied at random moments. To tackle this issue, we propose a new protocol to optimize the application of tDCS by selectively stimulating at high vigilance and low vigilance states, as measured by real-time spectral entropy (as a marker of vigilance) and based on pre-identified individual thresholds, in a closed-loop fashion. We will conduct a clinical trial on 36 patients in MCS who will undergo a 4-hour EEG recording beforehand to set individual vigilance thresholds. The patients will then be randomized in three groups based on the moment of tDCS application: high vigilance, low vigilance and sham. These EEG-tDCS sessions will last for 6 hours with a maximum of two tDCS sessions of 20 min at 2 mA. Behavioral effects will be assessed using the Coma Recovery Scale-Revised at baseline, after 3 and 6 hours. The device used will be provided by Starlab and enable real-time analysis of EEG dynamics and spectral entropy as well as control of the tDCS stimulator (a customized version of Neuroelectrics’ Startsim 8). This unique and novel approach will provide new insights for the identification of tDCS responders and provide treatment options for the challenging population of patients with disorders of consciousness.

Monitoring the effects of feeding in groups: Behavioural trials in farmed elk in winter

We studied the effect of managing group size in domesticated elk in the context of social foraging theory, and toward recommendations for livestock well-being and efficient use of common pastures. We compared foraging in adult female elk presented with feeding trays of alfalfa pellets mixed with segments of plastic tube. As the ratio of alfalfa pellets to plastic tubes decreases, there is a point called the giving-up density (GUD), measured as the weight of remaining food, at which a foraging elk stops searching for pellets. We compared individual scanning rates, or vigilance, as well as GUDs, over trials in repeated measures that included single elk and elk in groups of two, three, four, five, seven, 10, 13 and 17. We also compared a group of four and a group of seven elk with and without their calves, and groups with and without a dominant individual, defined as a female that moved to a feeding tray and resulted in its being abandoned by another female. We found an exponential decline in GUDs with increasing group size (F1,117 = 5.14, P = 0.02) regardless of presence of calves and consistent with the ‘group size effect,’ which predicts lower individual vigilance with a greater number in a group, a welfare benefit of social foraging. Among 10 adults tracked as focal animals through at least three trials, all but one elk expressed lower GUDs in larger groups, leading to 14% less scanning with each additional elk individual in a group (F1,117 = 8.42, R2 = (118 repeated measures) = 0.60, P < 0.01). With the exponential decline in both GUDs and scanning rate, we conclude that captive elk experience greater security as group size increases. Contrary to predictions from free-ranging elk, GUDs were significantly lower with calves present for the two group sizes compared (group of four, F1,32 = 17.1, P < 0.01; seven, F1,29 = 111.2, P < 0.01). With or without calves, neither scanning rate (F1,59 = 2.34, P = 0.13) nor the relationship of scanning rate with group size (F2,59 = 1.34, P = 0.25) changed. Separating dominant elk did not produce any significant effects. Pasture configuration to foster closer groups of elk could promote a healthier herd and more effective use of foraging areas. Farmers should manage elk groups to include calves with their dams whenever possible.

Individual vigilance profiles in flocks of House Sparrows (Passerdomesticus)

Individual vigilance against threats typically decreases with group size. However, group size often explains a small amount of variation in vigilance, suggesting that other factors such as individual differences might contribute. For instance, individuals could maintain different vigilance levels overall and also respond differently to variation in group size. We investigated individual variation in vigilance and its patterns of plasticity in flocks of House Sparrows (Passer domesticus (Linnaeus, 1758)). We carried out observations at one provisioned site and used multiple observations of the same individuals (n = 14) in flocks of different sizes over two consecutive months. The typical decline in vigilance with flock size occurred at the population level. Controlling for food density, flock size, time of year, and sex, we documented consistent individual differences in various measurements of vigilance. Plasticity of vigilance adjustments to variation in flock size occurred for the frequency of high vigilance postures. Male House Sparrows with larger bibs, which signal higher dominance status, tended to spend less time vigilant and obtained food at a higher rate, supporting a state-dependent explanation for the origin of individual vigilance profiles. Individual differences can contribute to explaining the large scatter in the relationship between vigilance and group size in many species.

Vigilance, staring and escape running in antipredator behavior of goitered gazelle

Predation is a very powerful force that shapes many ungulate traits. It is widely known that increasing vigilance intensity is costly and leads to a decline of forage intake. Consequently, ungulates gather into larger groups to reduce an individual vigilance burden by using the “many eyes” effect and to enhance their survival through the “safety in numbers” effect. Vigilance rate and related aggregation changes are two of the most discussed antipredator responses of ungulates to predation risk, but less considered factors also have a significant impact. To enhance our knowledge on these impact factors, I investigated the antipredator responses (vigilance, staring, and escape running) of goitered gazelles. I found that: a) adult females demonstrated vigilance, staring and escape running significantly more often than adult males, sub-adults and fawns; b) adult gazelles (females and males), having more experience in responding to threats, were more vigilant than young individuals (sub-adults and fawns), having likely more involvement in finding food; c) during the birthing and hiding periods, mothers displayed higher rates of vigilance than in other seasons, while staring and escape running were observed most often at the end of the hiding period, when fawns altering their hiding strategy to following one, started to walk a lot in the absence of mothers, as well; and d) goitered gazelles changed their vigilance rate in response to predation risks before changing group size. The events of the yearly biological cycle (birthing/rearing young for females; rutting for males) also had significant impacts on the antipredator responses (vigilance rate and aggregation) in adult gazelles.

Group size effects on inter-blink interval as an indicator of antipredator vigilance in wild baboons

Vigilance in animals is an important means for predator detection. Animals living in groups reduce their predation risk as more individuals are present. In contrast to most other animals studied, many studies on primates do not support the prediction that individual vigilance will decline as group size increases. For animals to obtain visual information during vigilance behaviour, their eyes must be open. Therefore, if animals are able to perceive differential risk of predation, the inter-blink interval (eye-opening) should increase, and the blink duration (eye-closure) should decrease under higher predation risk. We tested this prediction by measuring inter-blink interval in wild anubis baboons (Papio anubis) in peripheral and centre individuals within a group, and between larger and smaller groups. We found that the inter-blink interval for young males, often located at the front edge of the group, was longer than that of adult males, adult females, and young females, often located in the center of the group, and that the inter-blink interval for adult males was longer when the group was smaller. These results suggest that inter-blink interval can be used as an indicator of primate vigilance toward predators.

Organization enhances collective vigilance in the hovering guards of Tetragonisca angustula bees.

One benefit of group living is vigilance against predators. Previous studies have investigated the group size effect, where individual vigilance decreases as group size increases without reducing the overall ability of the group to detect predators. However, there has been comparatively little research on whether the positioning of individuals can improve the collective vigilance of the group. We studied the coordination of vigilance and its effect on predator detection in the eusocial bee Tetragonisca angustula. Nests are defended by hovering guards that detect and intercept intruders before they reach the nest entrance, in addition to those that stand upon it. We show that hovering guards are positioned nonrandomly, with a strong tendency for equal numbers on both sides of the entrance. This organization increases the collective vigilance of the guard group, as groups distributed in an even ratio, either side of the entrance, have a greater collective field of view than groups that deviate from an even ratio. Finally, we use a bioassay to show that when guards are on both sides of the entrance, their ability to detect intruders before they reach the entrance increases. Overall, our results provide strong evidence that vigilance is coordinated and that this improves nest defense. Although other group-living animals are often selfish in their individual vigilance behaviors and face competing time constraints such as foraging, the altruistic nature of eusocial insect workers has probably facilitated the evolution of coordinated vigilance, as documented here in T. angustula.

Unintentional sulfonylurea toxicity due to a drug\u2013drug interaction: a case report

BackgroundSulfonylureas are widely used for type 2 diabetes mellitus, but these medications carry a risk of hypoglycemia. Drug–drug interactions that inhibit sulfonylurea metabolism and thus increase systemic exposure can cause unintentional sulfonylurea toxicity.Case presentationA 56-year-old man presented with severe, recurrent hypoglycemia. He had a history of type 2 diabetes mellitus and was taking the sulfonylurea gliclazide with no prior episodes of hypoglycemia. The onset of his hypoglycemia occurred within days after starting voriconazole and subsequently fluconazole for a fungal pneumonia. Unintentional sulfonylurea toxicity developed due to an adverse drug–drug interaction between gliclazide and these antifungals. Azole antifungals inhibit the metabolism of sulfonylureas resulting in increased systemic exposure and consequent toxicity. After the diagnosis of sulfonylurea toxicity was recognized, the patient was treated initially with dextrose and then administered octreotide to prevent recurrent hypoglycemia. He was successfully managed, his hypoglycemic episodes resolved, and his medications were adjusted to avoid any further adverse interactions.ConclusionsAdverse drug–drug interactions continue to pose challenges to clinicians. Both individual vigilance and system wide strategies are needed to prevent and mitigate consequences. This case highlights an important drug–drug interaction and reviews the presentation, management and antidotal therapy of sulfonylurea toxicity.

Vigilance responding to number of conspecifics among mixed groups of cranes in demilitarized zone

ABSTRACTNumerous studies have addressed antipredatory benefits of mixed-species flocks of foragers, but studies on individual's vigilance as a function of group size are limited. In the Cheolwon area of the Korean Demilitarized Zone, vigilance of the subordinate White-naped cranes (Grus vipio) in 11 groups composed of conspecifics and the dominant Red-crowned cranes (Grus japonensis) was examined. Vigilance correlated negatively with group size due to negative correlation with the number of conspecifics, but not the dominant heterospecifics. This is consistent with the hypothesis that a decrease in vigilance in larger groups is due to antipredatory benefits from increased predator detection in larger groups (associated with the presence of a larger number of conspecifics). This suggested that the mechanism leads to canceling out of the otherwise expected antipredatory benefits to the subordinate species from the increased predator detection by larger group size (associated with larger number of dominants). This is one of only a few behavioral studies of these endangered crane species in the relatively inaccessible wintering area of international importance in the areas of high conservation value.

Are wintering Common Redpolls &lt;i&gt;Carduelis flammea&lt;/i&gt; more exposed to avian predators than other small passerines?

The Common Redpoll Carduelis flammea is a highly social flocking bird which forms cohesive groups outside the breeding season. Being small birds (12-15g), they need to forage almost continuously during a few hours of daylight in winter to meet their energy demands. Although predation risk is reduced as a result of improved surveillance of many eyes, increased flock size may also increase the agonistic interactions among individuals within the flock and as a consequence lower the probability of detection of a predator’s approach. To examine whether Common Redpolls, living in relatively large winter flocks, are more exposed to avian predators than small passerines living in groups of only a few individuals, I recorded the responses of Common Redpolls, Willow Tits Poecile montanus and Great Tits Parus major to a life-like stuffed specimen of two different predators, the Siberian Jay Perisoreus infaustus (body length 30 cm) and the Hooded Crow Corvus cornix (50 cm). After the presentation of a predator model, Redpolls returned to the seed sites on the average earlier than the tits, and significantly so versus both tit species after exposure to the Siberian Jay, and for Great Tits after exposure to the Hooded Crow. Whereas Willow and Great Tits seemed to pick up sunflower seeds in the snow without much competition, Common Redpolls displayed a more conspicuous, aggressive, intraspecific behaviour. Thus, the individual vigilance of Common Redpolls was most likely reduced and exposure time to predation increased. The seed-eating Common Redpolls may be more food-stressed than the year-round resident Willow Tits that have stored food within their territories. If so, Common Redpolls may be forced to take greater predation risks because of a higher hunger level. If the differences in return times after exposure to a predator model reflected an adaptation to perceived predation risk, the Common Redpolls apparently evaluated the Siberian Jay as less dangerous than did the tits.