Effects of reproductive status, social rank, sex and group size on vigilance patterns in Przewalski's gazelle

Zebra Risk Perception in a Landscape of Fear

Animals' assessments of predation risk are influenced by a variety of external and internal factors, including predator space use. However, it remains unclear what variables mediate prey species behavior within a landscape where predation risk is heterogeneous. To address this, we employed three assays to examine zebra (Equus quagga) responses to varying predation risk in a multiple-use area of northern Tanzania: (1) quantifying head-up posture as a proxy for vigilance through direct behavioral observation in areas of high and low likelihood of lion (Panthera leo) presence, (2) quantifying head-up posture as a proxy for vigilance when exposed to a lion roar playback, and (3) measuring flight initiation distances (FIDs) when approached by a person. Using generalized linear (mixed) models, we tested how lion space use and habitat type (as proxies for predation risk), normalized difference vegetation index (NDVI, as proxy for primary productivity), time of the day, and zebra-related variables (sex-age category, zebra herd size, group size including heterospecifics, and location within the herd) influenced vigilance and flight responses. We found that (1) neither vigilance nor FID were markedly influenced by estimated lion space use, habitat type, and NDVI; (2) vigilance decreased with group size, was lower for zebras positioned centrally in the herd, and during midday; (3) FID increased with a greater number of associated heterospecifics; and (4) zebras increased vigilance when exposed to lion roar playbacks, irrespective of lion space use. These findings suggest that zebra vigilance and flight behavior are not necessarily mediated by spatial variation in apparent predation risk but instead reflect a strategy of maintaining a consistent monitoring of possible threats across the landscape. Rather than relying on spatial clues alone, zebras primarily mitigate predation risk by increasing group size and associating with other species.

Environmental drivers of vigilance behaviour in painted stork (Mycteria leucocephala) nesting colonies

Vigilance in animals, crucial for predator detection, impacts survival and reproduction by diverting time from activities like foraging and mating. Painted Stork (Mycteria leucocephala), a colonially nesting bird, experiences disturbances from avian predators and human presence while nesting in colonies across varied habitats in India. We measured environmental vigilance behaviour at two diverse types of nesting sites in North India, the National Zoological Park and Keoladeo National Park. We studied the study role of several variables viz. sex, nestling age, number of neighbours, number of visitors, and other variables on vigilance, by camera techniques. Our findings revealed significant sex-based differences, with males being more vigilant than females, likely due to their roles in territoriality, mate guarding, and nest protection. Parental vigilance increased as nestlings aged, underscoring its importance as parental investment. Generalized Linear Mixed Models (GLMMs) indicated that number of visitors, number of neighbours, and other habitat variables significantly affected vigilance behaviour. Painted Storks at the National Zoological Park displayed higher vigilance than Storks in Keoladeo National Park, attributed to site specific variables.

Studies of a Naturally Occurring Selenium-Induced Microcytic Anemia in the Przewalski's Gazelle

Due to the fencing of the Przewalski's gazelle (Procapra przewalskii), the microcytic anemia incidence rate continues to increase. The primary pathological symptoms include emaciation, anemia, pica, inappetence, and dyskinesia. To investigate the cause of microcytic anemia ailment in the Przewalski's gazelle, the Upper Buha River Area with an excessive incidence was chosen as the experimental pasture, and the Bird Island Area without microcytic anemia disease was chosen as the control field. Then, the mineral contents in the soil, forage, blood, and liver, as well as the blood routine parameters and biochemical indexes were measured. The findings showed that the experimental pasture had much lower Se content in the soil and forage than the control field (p < 0.01), while the impacted pasture had significantly higher S content in the forage. The damaged gazelles had considerably lower Se and Cu contents and higher S content in the blood and liver than the healthy gazelles (p < 0.01). The presences of Hb, HCT, MCV, and MCH were significantly decreased compared to those in healthy gazelles (p < 0.01). The experimental group had a significantly lower level of GSH-Px activity in their serums compared to the control group (p < 0.01). In the treatment experiment, ten gazelles from the affected pasture were orally administered CuSO4, 6 g/animal once every 10 days for two consecutive times, and all gazelles were successfully cured. Therefore, it is possible that low Se content in the soil induced an increase in the absorption of S content by forage, leading to the deficiency of secondary Cu in the Przewalski's gazelles, resulting in microcytic anemia.

Metabolomic Analysis Reveals the Adaptation in the P. przewalskii to Se-Deprived Environment

The Procapra przewalskii inhabits in a selenium (Se)-deprived environment in long-term, but they have no pathological manifestations due to the Se deprivation. This study aimed to reveal the underlying adaptation induced by Se deprivation. In the analysis, a total of 93 significantly changed metabolites were identified in positive and negative ion modes, including 46 upregulated and 47 downregulated compounds in the Se-deprived group. The differential metabolites were annotated as the major molecules in bile acid biosynthesis, biosynthesis of unsaturated fatty acids, and pyrimidine metabolism, respectively. This study systematically analyzed the serum metabolomics characteristics of P. przewalskii under Se-deprived conditions for the first time, providing a basis for further understanding of the metabolic mechanism of P. przewalskii in the Se-deprived environment.

“Ecology of fear” in ungulates: Opportunities for improving conservation

Because ungulates are important contributors to ecosystem function, understanding the “ecology of fear” could be important to the conservation of ecosystems. Although studying ungulate ecology of fear is common, knowledge from ungulate systems is highly contested among ecologists. Here, we review the available literature on the ecology of fear in ungulates to generalize our current knowledge and how we can leverage it for conservation. Four general focus areas emerged from the 275 papers included in our literature search (and some papers were included in multiple categories): behavioral responses to predation risk (79%), physiological responses to predation risk (15%), trophic cascades resulting from ungulate responses to predation risk (20%), and manipulation of predation risk (1%). Of papers focused on behavior, 75% were about movement and habitat selection. Studies were biased toward North America (53%), tended to be focused on elk (Cervus canadensis; 29%), and were dominated by gray wolves (40%) or humans (39%) as predators of interest. Emerging literature suggests that we can utilize predation risk for conservation with top‐down (i.e., increasing predation risk) and bottom‐up (i.e., manipulating landscape characteristics to increase risk or risk perception) approaches. It is less clear whether fear‐related changes in physiology have population‐level fitness consequences or cascading effects, which could be fruitful avenues for future research. Conflicting evidence of trait‐mediated trophic cascades might be improved with better replication across systems and accounting for confounding effects of ungulate density. Improving our understanding of mechanisms modulating the nature of trophic cascades likely is most important to ensure desirable conservation outcomes. We recommend future work embrace the complexity of natural systems by attempting to link together the focal areas of study identified herein.

A meta-analysis of the group-size effect on vigilance in mammals

Group-size effects, whereby antipredator vigilance decreases as group size increases, are widely reported in mammals and birds but a meta-analysis has only been conducted in birds. We systematically reviewed the literature on mammalian group-size effects, estimated the effect sizes in each study, and conducted a phylogenetic meta-analysis. We obtained 296 effect sizes from 97 species belonging to 10 Orders and 26 Families. Overall, effect sizes indicated a moderate negative effect of group size (r = −0.44), but 43% of the effect sizes were compatible with a null effect of group size. There was significant heterogeneity in effect sizes. Weaker effect sizes occurred when vigilance was measured as a frequency or a duration rather than as a percentage of time spent vigilant, when measured in closed habitats, during the reproductive season, and in mixed-sex groups or during times when juveniles were absent. We infer a “file drawer problem” because there were relatively few studies with smaller sample sizes reporting small group-size effects. The results confirm the importance of group size in explaining variation in mammalian vigilance but also suggest which a substantial amount of variation remains unexplained. We suggest that future studies should aim to study mammalian group-size effects by quantifying the percentage of time allocated to vigilance rather than lower-power methods such as frequency or duration of vigilance.

Breeding Strategies to Optimize Effective Population Size in Low Census Captive Populations: The Case of Gazella cuvieri

Simple Summary

Small-sized populations frequently undergo a significant loss of genetic variability that can lead to their extinction. Therefore, research on animal breeding has focused on mating systems for minimizing the disappearance of genetic variability. Minimizing the average coancestry of offspring has been described as the best strategy for this purpose. Traditionally, the preservation of genetic variability has been approached via breeding strategies for increasing the effective population size (Ne). The main objective of this study was to compare, via computer simulations, the performance of different breeding schemes to limit the losses of genetic diversity in small populations. This objective was achieved by monitoring the evolution of the effective size obtained by different strategies across 20 generations with a starting point of two pedigree real populations of Gazella cuvieri. The results showed that minimizing average coancestry in a cohort did not maximize the effective size as compared with new strategies that were designed for this study. Furthermore, the best strategy may vary for each population and should be studied individually.

Abstract

Small-sized animal populations can undergo significant loss of genetic variability that can lead to their extinction. Therefore, studies on animal breeding have focused on mating systems for minimizing the disappearance of genetic variability. The main objective of this study was to compare, using computer simulations, the performance of different breeding schemes to limit the loss of genetic diversity in small-sized populations. This objective was achieved by monitoring the evolution of the effective population size obtained by 23 strategies throughout 20 generations in two populations of Gazella cuvieri. The scenarios were designed with different assumptions, in both reference subpopulations, regarding: the use of parents coancestry or offspring coancestry, the use of their increases or the coefficients themselves, and the number of males and females involved. Computations were performed using an experimental module of Endog v4.9 developed for this purpose. The results of the study showed that strategies for minimizing the coancestry of the parents were better in the short term; however, these strategies were worse in the long term. Minimizing the average coancestry of the offspring was a better approach in the long term. Nevertheless, in both populations, the best results were obtained when both the coancestry of the parents and the coancestry of the offspring were weighted at 5% each and neither males nor females were assumed to contribute to the next generation. In any case, not all strategies had the same evolutionary pattern throughout generations in both populations. The current results show that neither traditional nor new strategies have any general use. Therefore, it is important to carefully test these strategies before applying them to different populations with different breeding needs under different conditions, such as different generation intervals, and different natural breeding systems such as monogamy or polygyny.

Responses of Przewalski's Gazelle (Procapra przewalskii) to Zinc Nutrition in Physical Habitat

To study responses of Procapra przewalskii to zinc (Zn) nutrition in physical habitat, we analyzed the content of mineral elements in soil, forage, and animal tissues. Physiological and biochemical indexes were also determined. The results showed that Zn contents in the soil and forage from affected pasture were significantly lower (P < 0.01) than those in unaffected areas. Zn concentrations in the blood, liver, and hair from affected P. przewalskii were also significantly lower (P < 0.01) than those in healthy animals. The levels of hemoglobin, erythrocyte count, and packed cell volume from affected P. przewalskii were significantly lower (P < 0.01) than those in healthy animals. Serum aspartate aminotransferase and alanine transaminase activities were significantly lower (P < 0.01) in affected P. przewalskii than in healthy animals, while serum lactate dehydrogenase and alkaline phosphatase levels were significantly higher (P < 0.01) in affected compared with healthy animals. The activities of superoxide dismutase, glutathione peroxidase, and catalase in serum were significantly lower and the malondialdehyde content was significantly higher (all P < 0.01) in affected compared with healthy animals. Affected P. przewalskii were treated orally with ZnSO₄. The Zn content in the blood increased gradually and serum antioxidant indexes gradually returned to within the healthy range. Zn deprivation in forage thus not only influenced the blood mineral content but also severely disrupted blood parameters and antioxidant function in P. przewalskii.

The group size effect and synchronization of vigilance in the Tibetan wild ass

Vigilance behavior is considered as an effective strategy for prey species to detect predators. An individual benefits from living in a group by reducing the time spent being vigilant without affecting the probability of detecting a predator. However, the mechanism producing a decrease in vigilance with increasing group size is unclear. Many models of vigilance assume that group members scan independently of one another. Yet in recent studies, the other 2 patterns of vigilance, coordination and synchronization, were reported in some species. In 2 summers (2018 and 2019), we studied the group-size effect on vigilance and foraging of Tibetan wild ass in Chang Tang Nature Reserve of Tibet. We also tested whether individuals scan the environment independently, tend to coordinate their scans, or tend to synchronize their vigilance. The results showed that individuals decreased the time spent on vigilance with increasing group size, while increased the time spent foraging. Group members scanned the environment at the same time more frequently and there was a positive correlation between group members’ behaviors, indicating that Tibetan wild asses tend to synchronize their vigilance.

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.

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.

Vigilance behaviour in Siberian ibex (Capra sibirica): Effect of group size, group type, sex and age

Gregarious prey species modify their behaviours in response to predation risk in two ways: by increasing vigilance level or enlarging herd size. However, individuals of various sex and age have different responses to the same danger, and even the same individuals react differently depending on their status during biological events or within group types. But how these factors influence the interactions between vigilance level and group size is still poorly understood. Therefore, we studied this phenomenon by observing and analyzing the behaviours of the Siberian ibex (Capra sibirica) in the Eastern Tian-Shan Mountains (China). We found that similar to many other gregarious ungulates, Siberian ibex demonstrated a decrease in vigilance level with an increase in group size, since staying in larger groups increased the probability of predator detection and reduced the possibility of being captured. In general, males were more vigilant than females during the rut due to the sharp increase in their social alertness to achieve greater success in reproduction. In contrast, females were more vigilant than males out of rutting time, particularly significantly following parturition, since mothers spent a lot of their energy in maternal care, which coupled with having small and unexperienced newborns, made them more vulnerable to predation than other conspecifics. Siberian ibex had the same vigilance level in summer and winter, because of seasonally opposite trade-offs between feeding duration and vigilance level based on seasonal changes in food availability. Individuals in mixed-sex and female groups were more often targeted by predators, prompting individuals from these groups to be more vigilant than in male groups. The vigilance level in males decreased with age likely because of their increased body size and enhanced vigilance experience, which reduced their risk of predation. Our study confirmed that the Siberian ibex' vigilance level inversely correlated with group size, but other various factors, such as forage biomass/quality, sex, biological cycle, group types and age, had significant impacts on their interrelationship.

Inter- and intraspecific vigilance patterns of two sympatric Tibetan ungulates

Vigilance is an important antipredation technique that can be affected by many factors, such as body size and group size. Small animals are more vulnerable than large ones, so the former are expected to behave more vigilantly than the latter. This effect of body size on vigilance may occur inter- or intraspecifically. We studied the vigilance behavior of two sympatric wild ungulates, Tibetan antelopes (Pantholops hodgsonii) and Tibetan gazelles (Procapra picticaudata). Tibetan antelopes, with a body size of 33 kg are much larger than Tibetan gazelles, with a body size of approximately 14 kg. Tibetan antelopes are sexually and body-size dimorphic; that is, males are much heavier than females. Alternately, Tibetan gazelles are sexually dimorphic but the sexes do not differ in weight. Tibetan gazelles scanned their environment more frequently than Tibetan antelopes did. Small female Tibetan antelopes scanned their environment more frequently than males did, whereas male Tibetan gazelles scanned their environment more frequently than females did. Group size did not affect the vigilance of Tibetan gazelle, but its negative effect on the vigilance of male Tibetan antelopes was marginally significant. In female Tibetan antelopes, vigilance in large groups was high probably because of scramble competition and social monitoring. Our results suggested that body mass and group size play an important role in shaping the vigilance of these two rare Tibetan ungulates.

On how risk and group size interact to influence vigilance

Vigilance allows animals to monitor their surroundings for signs of danger associated with predators or rivals. As vigilance is costly, models predict that it should increase when the risk posed by predators or rivals increases. In addition, vigilance is expected to decrease in larger groups that provide more safety against predators. Risk and group size are thus two key determinants of vigilance. Together, they could have additive or interactive effects. If risk and group size interacted, the magnitude of the group-size effect on vigilance would vary depending on the level of risk experienced, implying that the benefits of sociality in terms of vigilance vary with risk. Depending on the model, vigilance is predicted to decrease more rapidly with group size at low risk or at high risk. Little work has focused directly on the interaction between risk and group size, making it difficult to understand under which conditions particular interactive effects arise and whether interactive effects are common in natural systems. I review the vast literature on vigilance in birds and mammals to assess whether interactive effects between risk and group size are common, and if present, which pattern occurs more frequently. In studies involving predation risk, the greatest proportion reported no statistically significant interactive effects. In other cases, vigilance decreased with group size more rapidly at low or high risk in a similar proportion of studies. In studies involving risk posed by rivals (social risk), most documented a more rapid decrease in vigilance with group size at low than at high risk, as predicted if the need to monitor rivals increases in larger groups. Low statistical power to detect interactive effects might have been an issue in several studies. The absence of interactive effects, on the other hand, might suggest constraints or limits on the ability of animals to adjust vigilance to current risk or group sizes. Interactive effects on vigilance have implications for the evolution of sociality and for our understanding of the phenotypic plasticity of predator- and competitor-induced defences and deserve more attention in future studies.

Individual vigilance profiles in flocks of House Sparrows (Passer domesticus)

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.

Breeding chronology and social interactions affect ungulate foraging behavior at a concentrated food resource

Prey species must balance predator avoidance behavior with other essential activities including foraging, breeding, and social interactions. Anti-predator behaviors such as vigilance can impede resource acquisition rates by altering foraging behavior. However, in addition to predation risk, foraging behavior may also be affected by socio-sexual factors including breeding chronology and social interactions. Therefore, we investigated how time-of-day, distance-to-forest, group size, social interactions (presence of different sex-age class), and breeding chronology (pre-breeding, breeding, post-breeding seasons) affected probability of feeding (hereafter: feeding) for different sex and age-classes (mature males, immature males, adult females, and juveniles) of white-tailed deer at feed sites. We developed a set of candidate models consisting of social, habitat, reproductive, and abiotic factors and combinations of these factors. We then used generalized linear mixed models (GLMMs) to estimate the probability of feeding and used model averaging of competing models for multimodel inference. Each adult sex-age class’ feeding was influenced by breeding chronology. Juveniles were more likely to be feeding than adults in all seasons. Feeding increased with group size for all sex-age classes. The presence of a mature male negatively influenced the feeding of immature males and juveniles were more likely to be feeding when an adult female was present. Feeding decreased with increasing distance-to-forest for mature males but not for other sex-age classes. Our results indicate that each sex-age class modulates vigilance levels in response to socio-sexual factors according to the unique pressures placed upon them by their reproductive status and social rank.

Group or ungroup - moose behavioural response to recolonization of wolves

Background

Predation risk is a primary motivator for prey to congregate in larger groups. A large group can be beneficial to detect predators, share predation risk among individuals and cause confusion for an attacking predator. However, forming large groups also has disadvantages like higher detection and attack rates of predators or interspecific competition. With the current recolonization of wolves (Canis lupus) in Scandinavia, we studied whether moose (Alces alces) respond by changing grouping behaviour as an anti-predatory strategy and that this change should be related to the duration of wolf presence within the local moose population. In particular, as females with calves are most vulnerable to predation risk, they should be more likely to alter behaviour.

Methods

To study grouping behaviour, we used aerial observations of moose (n = 1335, where each observation included one or several moose) inside and outside wolf territories.

Results

Moose mostly stayed solitary or in small groups (82% of the observations consisted of less than three adult moose), and this behavior was independent of wolf presence. The results did not provide unequivocal support for our main hypothesis of an overall change in grouping behaviour in the moose population in response to wolf presence. Other variables such as moose density, snow depth and adult sex ratio of the group were overall more influential on grouping behaviour. However, the results showed a sex specific difference in social grouping in relation to wolf presence where males tended to form larger groups inside as compared to outside wolf territories. For male moose, population- and environmentally related variables were also important for the pattern of grouping.

Conclusions

The results did not give support for that wolf recolonization has resulted in an overall change in moose grouping behaviour. If indeed wolf-induced effects do exist, they may be difficult to discern because the effects from moose population and environmental factors may be stronger than any change in anti-predator behaviour. Our results thereby suggest that caution should be taken as to generalize about the effects of returning predators on the grouping behaviour of their prey.

Electronic supplementary material

The online version of this article (doi:10.1186/s12983-017-0195-z) contains supplementary material, which is available to authorized users.

Refuge or predation risk? Alternate ways to perceive hiker disturbance based on maternal state of female caribou

Human presence in natural environments is often a source of stress that is perceived by large ungulates as an increased risk of predation. Alternatively, disturbance induced by hikers creates a relatively predator‐free space that may serve as a refuge. We measured the behavioral responses of female caribou to disturbance associated with the presence of hikers during summer in the Gaspésie National Park. We used those data to determine whether caribou responded negatively to human activity (i.e., the predation risk hypothesis) or whether human activity resulted in a decrease in the magnitude of perceived risk (i.e., the refuge hypothesis). Female caribou with a calf spent nearly half of their time feeding, regardless of the presence of a trail or the number of hikers. They also decreased their vigilance near trails when the number of hikers increased. Conversely, lone females fed less frequently and almost doubled the time invested in vigilance under the same circumstances. However, both groups of females moved away from trails during the day, especially in the presence of hikers. We demonstrated that risk avoidance was specific to the maternal state of the individual. Lactating females accommodated the presence of hikers to increase time spent foraging and nutritional intake, providing support for the refuge hypothesis. Alternatively, lone females with lower energetic requirements and no maternal investment in a vulnerable calf appeared less tolerant to risk, consistent with the predation risk hypothesis. Synthesis and applications: Hikers influenced the vigilance–feeding trade‐off in caribou, underlining the importance of appropriate management of linear structures and human activities, especially across the critical habitat of endangered species. Even if some individuals seemed to benefit from human presence, this behavioral adaptation was not sufficient to reduce annual calf mortality associated with predation.

Vigilance and activity time-budget adjustments of wintering hooded cranes, Grus monacha, in human-dominated foraging habitats

Due to loss and degradation of natural wetlands, waterbirds increasingly rely on surrounding human-dominated habitats to obtain food. Quantifying vigilance patterns, investigating the trade-off among various activities, and examining the underlying mechanisms will help us understand how waterbirds adapt to human-caused disturbances. During two successive winters (November-February of 2012–13 and 2013–14), we studied the hooded crane, Grus monacha, in the Shengjin Lake National Nature Reserve (NNR), China, to investigate how the species responds to human disturbances through vigilance and activity time-budget adjustments. Our results showed striking differences in the behavior of the cranes when foraging in the highly disturbed rice paddy fields found in the buffer zone compared with the degraded natural wetlands in the core area of the NNR. Time spent vigilant decreased with flock size and cranes spent more time vigilant in the human-dominated buffer zone. In the rice paddy fields, the birds were more vigilant but also fed more at the expense of locomotion and maintenance activities. Adult cranes spent more time vigilant and foraged less than juveniles. We recommend habitat recovery in natural wetlands and community co-management in the surrounding human-dominated landscape for conservation of the hooded crane and, generally, for the vast numbers of migratory waterbirds wintering in the middle and lower reaches of the Yangtze River floodplain.

White-tailed deer vigilance: the influence of social and environmental factors

Vigilance behavior may directly affect fitness of prey animals, and understanding factors influencing vigilance may provide important insight into predator-prey interactions. We used 40,540 pictures taken withcamera traps in August 2011 and 2012to evaluate factors influencing individual vigilance behavior of white-tailed deer (Odocoileus virginianus) while foraging at baited sites. We used binary logistic regression to determine if individual vigilance was affected by age, sex, and group size. Additionally, we evaluated whether the time of the day,moon phase,and presence of other non-predatorwildlife species impacted individual vigilance. Juveniles were 11% less vigilant at baited sites than adults. Females were 46% more vigilant when fawns were present. Males and females spent more time feeding as group size increased, but with each addition of 1 individual to a group, males increased feeding time by nearly double that of females. Individual vigilance fluctuated with time of day andwith moon phase but generally was least during diurnal and moonlit nocturnal hours, indicating deer have the ability to adjust vigilance behavior to changing predation risk associated with varyinglight intensity.White-tailed deer increased individual vigilance when other non-predator wildlife were present. Our data indicate that differential effects of environmental and social constraints on vigilance behavior between sexes may encourage sexual segregation in white-tailed deer.

Human disturbances, habitat characteristics and social environment generate sex-specific responses in vigilance of Mediterranean mouflon

In prey species, vigilance is an important part of the decision making process related to predation risk effects. Therefore, understanding the mechanisms shaping vigilance behavior provides relevant insights on factors influencing individual fitness. We investigated the role of extrinsic and intrinsic factors on vigilance behavior in Mediterranean mouflon (Ovis gmelini musimon×Ovis sp.) in a study site spatially and temporally contrasted in human pressures. Both sexes were less vigilant in the wildlife reserve compared to surrounding unprotected areas, except for males during the hunting period. During this period, males tended to be less strictly restricted to the reserve than females what might lead to a pervasive effect of hunting within the protected area, resulting in an increase in male vigilance. It might also be a rutting effect that did not occur in unprotected areas because males vigilance was already maximal in response to human disturbances. In both sexes, yearlings were less vigilant than adults, probably because they traded off vigilance for learning and energy acquisition and/or because they relied on adult experience present in the group. Similarly, non-reproductive females benefited of the vigilance effort provided by reproductive females when belonging to the same group. However, in the absence of reproductive females, non-reproductive females were as vigilant as reproductive females. Increasing group size was only found to reduce vigilance in females (up to 17.5%), not in males. We also showed sex-specific responses to habitat characteristics. Females increased their vigilance when habitat visibility decreased (up to 13.8%) whereas males increased their vigilance when feeding on low quality sites, i.e., when concomitant increase in chewing time can be devoted to vigilance with limited costs. Our global approach was able to disentangle the sex-specific sources of variation in mouflon vigilance and stressed the importance of reserves in managing and conserving wild sheep populations.