Cooperative vigilance: The guanaco's (Lama guanicoe) key antipredator mechanism

Llamas use social information from conspecifics and humans to solve a spatial detour task

Learning by observing others (i.e. social learning) is an important mechanism to reduce the costs of individual learning. Social learning can occur between conspecifics but also heterospecifics. Domestication processes might have changed the animals' sensitivity to human social cues and recent research indicates that domesticated species are particularly good in learning socially from humans. Llamas (Lama glama) are an interesting model species for that purpose. Llamas were bred as pack animals, which requires close contact and cooperative behaviour towards humans. We investigated whether llamas learn socially from trained conspecifics and humans in a spatial detour task. Subjects were required to detour metal hurdles arranged in a V-shape to reach a food reward. Llamas were more successful in solving the task after both a human and a conspecific demonstrated the task compared to a control condition with no demonstrator. Individual differences in behaviour (i.e. food motivation and distraction) further affected the success rate. Animals did not necessarily use the same route as the demonstrators, thus, indicating that they adopted a more general detour behaviour. These results suggest that llamas can extract information from conspecific and heterospecific demonstrations; hence, broadening our knowledge of domesticated species that are sensitive to human social behaviour.

Cooperation increases bottlenose dolphins' (Tursiops truncatus) social affiliation

Dolphins live in a fission-fusion society, where strong social bonds and alliances can last for decades. However, the mechanism that allows dolphins to form such strong social bonds is still unclear. Here, we hypothesized the existence of a positive feedback mechanism in which social affiliation promotes dolphins' cooperation, which in turn promotes their social affiliation. To test it, we stimulated the cooperation of the 11 dolphins studied by providing a cooperative enrichment tool based on a rope-pulling task to access a resource. Then we measured the social affiliation [simple ratio index (SRI)] of each possible pair of dolphins and evaluated whether it increased after cooperation. We also evaluated whether, before cooperation, pairs that cooperated had a higher SRI than those that did not cooperate. Our findings showed that the 11 cooperating pairs had significantly stronger social affiliation before cooperation than the 15 non-cooperating pairs. Furthermore, cooperating pairs significantly increased their social affiliation after cooperation, while non-cooperating pairs did not. As a result, our findings provide support to our hypothesis, and suggest that the previous social affiliation between dolphins facilitates cooperation, which in turn promotes their social affiliation.

Sociability strongly affects the behavioural responses of wild guanacos to drones

Drones are being increasingly used in research and recreation but without an adequate assessment of their potential impacts on wildlife. Particularly, the effect of sociability on behavioural responses to drone-associated disturbance remains largely unknown. Using an ungulate with complex social behaviour, we (1) assessed how social aggregation and offspring presence, along with flight plan characteristics, influence the probability of behavioural reaction and the flight distance of wild guanacos (Lama guanicoe) to the drone's approach, and (2) estimated reaction thresholds and flight heights that minimise disturbance. Sociability significantly affected behavioural responses. Large groups showed higher reaction probability and greater flight distances than smaller groups and solitary individuals, regardless of the presence of offspring. This suggests greater detection abilities in large groups, but we cannot rule out the influence of other features inherent to each social unit (e.g., territoriality) that might be working simultaneously. Low flight heights increased the probability of reaction, although the effect of drone speed was less clear. Reaction thresholds ranged from 154 m (solitary individuals) to 344 m (mixed groups), revealing that the responsiveness of this guanaco population to the drone is the most dramatic reported so far for a wild species.

An experimental approach to evaluate the potential of drones in terrestrial mammal research: a gregarious ungulate as a study model

Research on the use of unmanned aircraft systems (UAS) in wildlife has made remarkable progress recently. Few studies to date have experimentally evaluated the effect of UAS on animals and have usually focused primarily on aquatic fauna. In terrestrial open arid ecosystems, with relatively good visibility to detect animals but little environmental noise, there should be a trade-off between flying the UAS at high height above ground level (AGL) to limit the disturbance of animals and flying low enough to maintain count precision. In addition, body size or social aggregation of species can also affect the ability to detect animals from the air and their response to the UAS approach. To address this gap, we used a gregarious ungulate, the guanaco (Lama guanicoe), as a study model. Based on three types of experimental flights, we demonstrated that (i) the likelihood of miscounting guanacos in images increases with UAS height, but only for offspring and (ii) higher height AGL and lower UAS speed reduce disturbance, except for large groups, which always reacted. Our results call into question mostly indirect and observational previous evidence that terrestrial mammals are more tolerant to UAS than other species and highlight the need for experimental and species-specific studies before using UAS methods.

Are there different vigilance strategies between types of social units in Lama guanicoe?

Group vigilance is a cooperative behaviour in social species that reduces individual risk of predation. Lama guanicoe is a social species of camelid performing cooperative vigilance, but little is known about the vigilance behaviour of different social units. We analysed the vigilance behaviour in different types of social units of L. guanicoe, to better understand the complexity of this behaviour. The best supported models for both the frequency of vigilance and the proportion of time vigilant included the type and size of social units as the most important predictors that affect the vigilance behaviour. Solitary males devoted proportionally more time in vigilance behaviour than family, mixed or bachelor groups, whereas females in female groups spent more time vigilant than guanacos in mixed groups. Frequency of vigilance was higher in family individuals and solitary males than in bachelor or mixed groups. It is likely that that in family and females groups, the presence of offspring would increase the vigilance behaviour to detect possible predators. Topography and habitat characteristics that determine the predation risk, affected vigilance behaviour of mixed groups and solitary males. Our results suggest that vigilance behaviour should not be generalized for this species, since there are differences between the types of social units, probably related to intrinsic characteristics of each one and the perception of risk.

Physiological and behavioral stress responses to predators are altered by prior predator experience in juvenile qingbo (Spinibarbus sinensis)

All vertebrates exhibit physiological responses to predator stress and these responses are the basis of appropriate behavioral adaptation. We aimed to identify the physiological and behavioral responses of juvenile qingbo (Spinibarbus sinensis) to its natural predator, the southern catfish (Silurus meridionalis) and to test whether these responses could be altered by prior predator experience. We measured the routine metabolic rate (RMR), cortisol levels and spontaneous behavior of both predator-naive and predator-experienced qingbo under predator-absent, predator-present and non-predator-present (Hemibarbus maculatus) conditions. Predator-naive qingbo showed a typical stress response in the form of increased RMR and cortisol when exposed to predators. Spontaneous activity showed no difference between prior-experience groups or among stimulus conditions when tested alone; however, when tested with a companion, predator-naive qingbo showed increased activity and decreased distance to the stimulus arena under the predator-present condition than they did under the predator-absent condition. Both predator-naive and predator-experienced qingbo showed different physiological and behavioral responses between predatory and non-predatory fish, which suggested that predator-naive qingbo can instinctually discriminate between natural predators and non-predators. Predator-naive qingbo increase their inspection behavior when exposed to a predator compared with the predator-absent condition only when tested with a companion, which is possibly due to decreased predation risk and increased boldness.

Summary: A predator-naive carp can recognize its natural predator, and this recognition can be intensified by prior experience with a predator or the presence of a conspecific.

Polish Pony Changes Lower Layer Biodiversity in Old Growth Scots Pine Stands

The study examines the influence of Polish primitive horse grazing on vegetation in deciduous and coniferous old forest stands in north-east Poland. It was conducted in both forest sites in two complexes located in: (i) the fenced area of the Popielno Research Station of the Polish Academy of Sciences, with free-living Polish pony [Polish primitive horse (Equus ferus caballus Linnaeus, 1758)] in 130-year-old stands, and (ii) in the open 116-year-old managed (harvested) Maskulińskie Forest District, without horses. In both areas the stands are inhabited by free-living red and roe deer. The impact of forest animals on ground cover layer as well as on understory shrub layer and undergrowth was compared. Very significant differences in the structure of the understory and undergrowth (above 0.5 m) layer vegetation communities between both areas and type of stands were found. The results suggest that the presence of the Polish horse substantially changed the species composition and increased the species diversity of the ground layer and shrub layer both in the coniferous forest and deciduous forest habitats. The height of the shrub layer trees was lower by 30% in the area with the Polish horse. The level of biodiversity of forest plants was dependent on the presence of the Polish horse, which in the past was one of the natural inhabitants of forests in the area of research.

Diversity of risk assessment patterns in antipredator behavior of goitered gazelles

In predator-prey encounters, risk assessment and threat identification are particularly important aspects in the prey's decision in how, when and where to escape. Previous studies devoted to this topic investigated mostly factors influencing risk perception by a prey animal and on its decision when to flee; however, information on the diversity of risk assessment displays is still very limited. Therefore in this paper, I considered various display types of risk assessments and the circumstances under which they were performed. I found that the contagious effect of alarm behavior among conspecifics and the investigative approach toward the threat were the types of risk assessment found most often, while mobbing was observed least often. Every type of risk assessment had a specific usage according to the sort of suspicious object and the prey's display circumstances. Adult females with few exceptions demonstrated threat assessment behavior most often, while adult males displayed assessment behavior less frequently; in all cases, sub-adults and fawns showed these patterns significantly less often than adults. Antipredator strategy of adult females likely differed from males. Adult females had the highest response and sensitivity to any kind of potential threat and a high rate of vigilance, including risk assessment, likely related to the responsibility of rearing young. In contrast, adult males were busy mostly with social vigilance and monitored conspecifics more than predators. Adolescents and fawns showed the lowest rate of risk assessment, most likely because information on the potential risk of threat was not as useful to them since they did not have enough experience to recognize and avoid predators; instead of relying on their own experience, younger animals followed and repeated the behaviors of adults. As a result, young of many ungulate species typically have the highest losses from predation and adult females the lowest, with adult male deaths in between. This regularity was also likely true for the risk assessment behaviors of goitered gazelles in my study.

Collective gradient sensing in fish schools

Throughout the animal kingdom, animals frequently benefit from living in groups. Models of collective behaviour show that simple local interactions are sufficient to generate group morphologies found in nature (swarms, flocks and mills). However, individuals also interact with the complex noisy environment in which they live. In this work, we experimentally investigate the group performance in navigating a noisy light gradient of two unrelated freshwater species: golden shiners (Notemigonuscrysoleucas) and rummy nose tetra (Hemigrammus bleheri). We find that tetras outperform shiners due to their innate individual ability to sense the environmental gradient. Using numerical simulations, we examine how group performance depends on the relative weight of social and environmental information. Our results highlight the importance of balancing of social and environmental information to promote optimal group morphologies and performance.

The effects of poaching and habitat structure on anti-predator behavioral strategies: A guanaco population in a high cold desert as case study

The effects of poaching on wildlife have been widely studied in conservation biology and can be heterogeneous, particularly on ungulates. These effects can be estimated through different methodologies whose use depends on several conditions such as Flight-initiation distance (FID). Our objectives were: 1- to evaluate whether poaching affects the FID and group structure of a guanaco (Lama guanicoe) population in a high cold desert in San Juan (Argentina); 2- to assess whether habitat structure (slope and vegetation cover) influences FID and group structure in this population. The study area included a site with poaching (unprotected area), and a site without poaching (protected area).

We recorded 100 groups of guanacos: 70 in the protected and 30 in the unprotected area. FID and group size were greater in the unprotected than in the protected area, whereas proportions of group categories (with offspring, without offspring and solitary) were similar between areas. Besides, in relation to habitat structure, FID increased when vegetation cover decreased. On the other hand, FID and group size were not affected by slope. Our study shows that guanacos respond to poaching pressure as do other ungulate species, and that other factors such as vegetation cover also affect this behavior. Managers should be aware when interpreting FID due to its relation to habitat structure; the guanaco appears to assume greater risk (lower FID) in areas with high vegetation cover.