Showing papers in "Ethology in 2018"

trajr: An R package for characterisation of animal trajectories

Abstract: Animal movement is studied in fields as diverse as population ecology (Turchin, 1998), foraging theory and resource exploitation (Mouillot & Viale, 2001; Pyke, Pulliam, & Charnov, 1977), and conservation biology (Gulesserian, Slip, Heller, & Harcourt, 2011). The analysis of trajectories, which are recorded tracks of individual animals moving through space and time, has been applied to answer questions about animal foraging, navigation, dispersal ecology, migration and behavioural mimicry (Codling, Plank, & Benhamou, 2008; Shamble, Hoy, Cohen, & Beatus, 2017). Animal trajectories are analysed as a set of time specific discrete locations, generally restricted to two spatial dimensions. As animal motion is continuous, trajectories are obtained by repeatedly sampling the location of an animal over time. A variety of techniques has been used to sample locations, including GPS tracking coupled with satellite or radio telemetry (Mouillot & Viale, 2001), manual tracking (Angilletta, Roth Ii, Wilson, Niehaus, & Ribeiro, 2008), digitising from video of a moving animal (Shamble et al., 2017), harmonic radar (Mascanzoni & Wallin, 1986) and following tracks in snow (Fortin, Morales, & Boyce, 2005). Location sampling may occur at constant time intervals, or at biologically meaningful step “endpoints,” such as landing sites of a foraging butterfly (Kareiva & Shigesada, 1983). Trajectories can be conveniently represented and analysed as a series of steps, each of which has a length and a direction. The steps correspond to vectors between consecutive locations in the sampled trajectory.

Citizen science and wildlife biology: Synergies and challenges

Abstract: 1Core facility Konrad Lorenz Forschungsstelle for Behaviour and Cognition, University of Vienna, Grünau im Almtal, Austria 2Department of Behavioural Biology, University of Vienna, Vienna, Austria 3Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic 4Department of Invasive Ecology, Institute of Botany, The Czech Academy of Sciences, Průhonice, Czech Republic 5Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany 6Department of Ecological Dynamics, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany 7Institute for Integrative Nature Conservation Research and Division of Plant Protection, University of Natural Resources and Life Sciences Vienna, Vienna, Austria 8Helmholtz Centre for Environmental Research – UFZ, German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany

The evolution of intraspecific variation in social organization

Abstract: Many species show intraspecific variation in their social organization (IVSO), which means the composition of their social groups can change between solitary living, pair living, or living in groups. Understanding IVSO is important because it demonstrates species resilience to environmental change and can help us to study ultimate and proximate reasons for group living by comparing solitary and group-living individuals in a single species. It has long been realized that the environment plays a key role in explaining the occurrence of IVSO. IVSO is expected to have evolved in variable environments and can thus be a key adaptation to environmental change. It has previously been suggested that four different mechanisms relying on the environment exist that can lead to IVSO: environmental disrupters, genetic differentiation, developmental plasticity, and social flexibility. All four mechanisms depend on the environment such that focusing only on environmental factors alone cannot explain IVSO. Importantly, only three represent evolved mechanisms, while environmental disrupters leading to the death of important group members induce nonadaptive IVSO. Environmental disrupters can be expected to cause IVSO even in species where IVSO is also an adaptive response. Here, we focus on the questions of why IVSO occurs and why it evolved. To understand IVSO at the species level, it is important to conduct continuous long-term studies to differentiate between nonadaptive and adaptive IVSO. We predict that IVSO evolves in environments that vary in important ecological variables, such as rainfall, food availability, and population density. IVSO might also depend on life history factors, especially longevity. IVSO is predicted to be more common in species with a short life span and that breed only for one breeding season, being selected to respond optimally to the prevailing environmental situation. Finally, we emphasize the importance of accounting for IVSO when studying social evolution, especially in comparative studies, as not every species can be assigned to one single form of social organization. For such comparative studies, it is important to use data based on the primary literature.

Guppies learn faster to discriminate between red and yellow than between two shapes

Abstract: Animal species are expected to evolve specialised cognitive abilities to solve the tasks that are critical for their fitness. The literature contains several examples of specialised cognitive abilities, but few regard fish. The guppy, Poecilia reticulata, is a freshwater fish in which females choose their mates based on colouration, and orange‐coloured fruits are important diet enrichments for both sexes. For these reasons, we expect that this species has evolved enhanced learning abilities in colour discrimination compared to other types of discrimination. The comparison between studies in which guppies were tested for colour discrimination and studies in which guppies were tested for shape discrimination seems to support this hypothesis, but direct testing is still lacking. We experimentally compared the learning performance of guppies trained in a red–yellow colour discrimination learning task and that of guppies trained in a shape discrimination learning task using the same, automated conditioning procedure. Guppies trained in the colour discrimination showed greater learning performance, which provides support to the hypothesis that guppies possess enhanced colour discrimination abilities. Moreover, we found that male guppies performed better than females in both shape and colour discrimination learning.

Evolutionary transitions to cooperative societies in fishes revisited

Abstract: Unravelling the evolution of complex social organization in animals is an important aim, not least because it helps to understand the evolutionary roots of human sociality. Recent advances in comparative methods allow to approach this question in a phylogenetic context. The validity of such comparative approaches depends strongly on the quality of information regarding the behaviour, sociality, and reproduction of animals in natural systems, and on the quality of the phylogenetic reconstruction. Applying a novel comparative approach, a recent study of Dey et al. (2017, Nature Ecology & Evolution, 1, 137) concluded that evolutionary transitions to cooperative breeding in cichlid fishes were not associated with the social mating pattern. Here we argue that this result was adversely affected by equivocal classifications of mating patterns, and inadequate phylogenetic data. In order to illustrate the impact of the mating system misclassifications, we scored mating patterns as reported in the original literature and re‐analysed the dataset based on Dey et al.’s tree topology. The result suggests that the mating system does in fact significantly explain the evolutionary transition to cooperative breeding in lamprologine cichlids, but we submit that a reliable conclusion cannot be reached before improving the behavioural information and the underlying phylogenetic reconstruction. The problems identified in this case study are not unique and we urge caution in the interpretation of results from comparative phylogenetic studies in general. We do agree with Dey et al. (2017) though that the lamprologine cichlids of Lake Tanganyika may constitute a fundamental test case for the theory of social evolution, but better information on their behaviour and phylogenetic relationships is needed to allow meaningful analyses.

Predator occurrence and perceived predation risk determine grouping behavior in guanaco (Lama guanicoe)

Abstract: © 2018 Blackwell Verlag GmbH Grouping behavior of social ungulates may depend on both predator occurrence and perceived predation risk associated with habitat structure, reproductive state, and density of conspecifics. Over 3 years, we studied grouping behavior of guanaco (Lama guanicoe) families in Chilean Patagonia during the birthing season and determined their response to variation in predator occurrence and perceived predation risk (habitat structure, calf/adult rate, and density of conspecifics). We considered the effect of two predators, puma (Puma concolor) and culpeo fox (Lycalopex culpaeus). We measured two common (family group size and vigilance) and one novel (family group cohesion) behavioral responses of guanaco. Our results show that guanaco family groups adapted their grouping behavior to both predator occurrence and perceived predation risk. Larger family groups were found in open habitats and areas with high puma occurrence, while guanacos stayed in small family groups in areas with high shrub cover or low visibility. Group cohesion increased in areas with higher occurrence of pumas and culpeo foxes, and also increased in smaller family groups and in areas with low guanaco density. Vigilance (number of vigilant adults) was mainly related to group size and visibility, increasing in areas with low visibility, while residual vigilance (vigilance after removing the group-size effect) did not vary with the explanatory variables examined. Our results suggest that a mix of predator occurrence and perceived predation risk influences guanaco grouping behavior and highlights the importance of evaluating different antipredator responses together and considering all predator species in studies aimed at understanding ungulate behavior.

The oddity effect drives prey choice but not necessarily attack time

Abstract: The tendency of predators to preferentially attack phenotypically odd prey in groups (the oddity effect) is a clear example of how predator cognition can impact behaviour and morphology in prey. Through targeting phenotypically odd prey, predators are thought to avoid the cognitive constraints that delay and limit the success of attacks on homogenous prey groups (the confusion effect). In addition to influencing which prey a predator will attack, the confusion and oddity effects would also predict that attacks on odd prey can occur more rapidly than attacking the majority prey type, as odd prey are more easily targeted, but this prediction has yet to be tested. Here, we used kerri tetra fish, Inpaichthys kerri, presented with mixed phenotypic groups of Daphnia dyed red or black to investigate whether odd prey in groups are preferentially attacked and whether these attacks were faster than those on the majority prey type. In agreement with previous work, odd prey were targeted and attacked more often than expected from their frequency in the prey groups, regardless of whether the odd prey was red in a group of black prey or vice versa. However, no difference was found in the time taken to attack odd vs. majority prey items, contrary to our predictions. Our results suggest that the time taken to make an attack is determined by a wider range of factors or is subject to greater variance than the choice of which prey is selectively targeted in a group.

Melodic males and flashy females: Geographic variation in male and female reproductive behavior in red‐eyed treefrogs (Agalychnis callidryas)

Abstract: Geographic variation in courtship behavior can affect reproductive success of divergent phenotypes via mate choice. Over time, this can lead to reproductive isolation and ultimately to speciation. The Neotropical red-eyed treefrog (Agalychnis callidryas) exhibits high levels of phenotypic variation among populations in Costa Rica and Panama, including differences in color pattern, body size, and skin peptides. To test the extent of behavioral premating isolation among differentiated populations, we quantified male advertisement calls from six sites and female responses to male stimuli (acoustic and visual signals) from four sites. Our results show that both male advertisement calls and female behavior vary among populations: Discriminant function analyses can predict the population of origin for 99.3% ± 0.7 of males based on male call (dominant frequency and bandwidth) and 76.1% ± 6.6 of females based on female response behavior (frequency and duration of visual displays). Further, female mate choice trials (n = 69) showed that population divergence in male signals is coupled with female preference for local male stimuli. Combined, these results suggest that evolved differences among populations in male call properties and female response signals could have consequences for reproductive isolation. Finally, population variation in male and female behavior was not well explained by geographic or genetic distance, indicating a role for localized selection and/or drift. The interplay between male courtship and female responses may facilitate the evolution of local variants in courtship style, thus accelerating premating isolation via assortative mating.

Habitat‐specific capture timing of deer mice (Peromyscus maniculatus) suggests that predators structure temporal activity of prey

Abstract: Editor: L. Ebensperger Abstract Timing is an essential component of the choices that animals make: The likelihood of successful resource capture (and predator avoidance) depends not just on what an animal chooses to do, but when it chooses to do it. Despite the importance of activity timing, our ability to understand the forces that constrain activity timing has been limited because this aspect of animal behavior is shaped by several factors (e.g., interspecific competitors, predators, physical conditions), and it is difficult to examine activity timing in a setting where only a single factor is operating. Using an island system that makes it possible to focus on the effect of predation risk in the absence of interspecific competition, we examine how the onset of activity of the deer mouse (Peromyscus maniculatus) varies between habitats with unique predation risks (i.e., minimalshrub cover versus abundantshrub cover sites). Using capture time to assess the timing of mouse activity, we found that mice in habitats with minimal shrub cover were captured 1.7 hr earlier than mice in habitats with abundant shrub cover. This difference in timing between habitats was likely a direct response to differences in predation risk between the two habitats: There were no differences in thermal conditions between the two habitats, and the difference in activity timing disappeared during a night when overcast skies reduced islandwide predation risk. Our results demonstrate that predation risk, independent of interspecific competition, can generate significant changes in animal activity timing. Our work suggests that habitat structure that provides safety (i.e., refuge habitats) plays a direct role in the timing of prey activity and that habitat modification that alters refuge availability (e.g., shrub dominance) may alter the timing of animal activity.

Habitat complexity dampens selection on prey activity level

Abstract: Editor: E. Hebets Abstract Conspecific prey individuals often exhibit persistent differences in behavior (i.e., animal personality) and consequently vary in their susceptibility to predation. How this form of selection varies across environmental contexts is essential to predicting ecological and evolutionary dynamics, yet remains currently unresolved. Here, we use three separate predator–prey systems (sea star–snail, wolf spider–cricket, and jumping spider–cricket) to independently examine how habitat structural complexity influences the selection that predators impose on prey behavioral types. Prior to conducting staged predator–prey interaction encounters, we ran prey individuals through multiple behavioral assays to determine their average activity level. We then allowed individual predators to interact with groups of prey in either open or structurally complex habitats and recorded the number and individual identity of prey that were eaten. Habitat complexity had no effect on overall predation rates in any of the three predator–prey systems. Despite this, we detected a pervasive interaction between habitat structure and individual prey activity level in determining individual prey survival. In open habitats, all predators imposed strong selection on prey behavioral types: sea stars preferentially consumed sedentary snails, while spiders preferentially consumed active crickets. Habitat complexity dampened selection within all three systems, equalizing the predation risk that active and sedentary prey faced. These findings suggest a general effect of habitat complexity that reduces the importance of prey activity level in determining individual predation risk. We reason this occurs because activity level (i.e., movement) is paramount in determining risk within open environments, whereas in complex habitats, other behavioral traits (e.g., escape ability to a refuge) may take precedence.

Testosterone pulses at the nest site modify ultrasonic vocalization types in a monogamous and territorial mouse

Abstract: Modulation of baseline testosterone (T) via long-lasting T implants alters territorial, sexual, and social behavior of animals in the field. Transient T increases occur in numerous species after social interactions, but these transient increases in T have not been manipulated in the field. In the laboratory, these T increases can influence future behavior for days, causing changes in social behavior and inducing preferences for specific locations. We manipulated transient increases in T in the field at the nests of the monogamous and territorial California mouse (Peromyscus californicus) to examine long-term (>24 hr) changes in ultrasonic vocalizations (USVs). Males of bonded male–female dyads (=pair) were administered a T injection (vs. saline) three times over seven days and USVs of the male–female dyad were measured for three days after the last injection. At T nests, the male–female dyad produced significantly more 1SV (one call SV: an SV is a sustained vocalization that is long in duration and low in modulation) and 4SV (four call SV) type USVs than controls, but no significant changes in aggressive barks. Overall, male–female dyad mice at T nests produced a greater diversity in call types such that 1SV, 4SV, 5SV, and a complex sweep were produced at T nests but not control nests. There were significantly more USVs produced at T nests on night 2 after the final injection. There were no differences in spectral characteristics of SV calls or aggressive barks between T and control nests. The function of the changes that occurred is unknown, but is consistent with increased long-term changes in behavioral interactions with nest mates and may reflect T-induced conditioned place preferences to the nest site. Significantly, transient increases in T influence future acoustic communication under field conditions with competing biotic and abiotic stimuli.

Collared peccary (Pecari tajacu) behavioral reactions toward a dead member of the herd

Abstract: Humans, elephants, chimpanzees, and cetaceans show concern with the death of other members of their species and respond to death in particular ways. Science considers that these species are exceptions and that other mammal species show little or no reaction to the dead bodies of individuals of their species. Collared peccaries (Pecari tajacu; Tayassuidae) are social animals that live in groups of 5–50 individuals maintaining close and complex social relationships. The collared peccary occupies many different environments and it is widely distributed from the south of North America to the north of Argentina. Their behavior is well studied, but we know little about their behavior toward the dead. We directly observed and filmed with a camera trap the reactions of a five-member herd of collared peccaries to the death of a herd member. We worked on a suburban forested area in the mountains of central Arizona. We found that the herd visited and spent time with the dead body for 10 days after the peccary died. The frequency of the visits declined until the cadaver was consumed by coyotes. Most of the videos showed two individuals visited the dead animal (44%), solitary records were also frequent (39%) and only 4% of the videos recorded three peccaries. Visits were more frequent during the night (64%). Peccaries do react to the death of a herd member by behaving in particular ways. Reactions include pushing at the dead individual, staring at it, biting it, and trying to pick it up by putting their snout under the corpse and pushing it up, and defending it from coyotes, among others. These levels of behavioral complexity for peccaries are beyond those known so far. The behaviors of this herd of peccaries resemble those of humans, cetaceans, chimpanzees, and elephants and show that these groups are not the only ones that react to death.

Does it always pay to defend one's nest? A case study in African penguin

Abstract: Editor: T. Tregenza Abstract Throughout the animal kingdom, individual variation in reproductive success is commonly observed, even under similar environmental conditions. However, the mechanisms behind such differences remain unclear. The notion of behavioural consistency in animals has developed rapidly since the early 21st century partly as an approach to understand amongindividual differences. In this context, a number of studies have highlighted the influence of pair assortment in personality on breeding success. In this study, we related breeding success to individual behaviour, specifically a risktaking behaviour, and pair assortment per behaviour in African penguins (Spheniscus demersus) over two breeding seasons of contrasting food availability. On Bird Island, Algoa Bay, South Africa, we used indices of boldness and overall mobility in penguins’ nest defence behaviour as a response to a standard pedestrian approach during chickrearing. These behaviours were consistent over the trials and indicated these traits may be related to personality in African penguins. Individuals were categorized as riskprone (“bold,” “mobile”) or riskaverse (“shy,” “nonmobile”). We then assessed their breeding success through chick growth and survival over 4 weeks in 2015 and 2016. There was weak positive assortment of pairs in relation to nest defence behaviour. However, pair assortment did not significantly influence birds’ breeding success. Shy penguins were generally the most successful (had the highest chick growth rates), which was especially apparent during a food shortage in 2016, possibly reflecting a higher energy investment when foraging. In contrast, chicks from bold parents grew significantly slower, especially in 2016. Bold parents may defend their nest successfully against predation or intraspecific aggression when food is abundant, but when predation risks are limited and food availability is low, this strategy may not be beneficial. In the context of climate change, where food shortage events may become more frequent, riskaverse individuals may be favoured and genetic diversity may be reduced in African penguins.

Lifespan and age, but not residual reproductive value or condition, are related to behaviour in wild field crickets

Abstract: Behaviour differs among species, among populations of the same species and among individuals within the same population (Wilson, 1998). This amongindividual variation in behaviour, aka “animal personality” (Dall, Houston, & McNamara, 2004), has received extensive theoretical and empirical interest in the last two decades, with a range of suggested evolutionary and ecological consequences (Wolf & Weissing, 2012). Amongindividual differences, which are contingent on limited individual flexibility, are widespread (Bell, Hankison, & Laskowski, 2009) and linked to fitness (Smith & Blumstein, 2008). As selection is expected to purge lessfit phenotypes, there must be evolutionary Received: 21 January 2018 | Revised: 14 February 2018 | Accepted: 18 February 2018 DOI: 10.1111/eth.12735

Hunt or hide: How insularity and urbanization affect foraging decisions in lizards

Abstract: Natural selection theory predicts that the decisions made by animals should reflect a balance between the costs and benefits of alternative behavioural strategies (Brock, Bednekoff, Pafilis, & Foufopoulos, 2014; Lima & Dill, 1990; Miranda, Schielzeth, Sonntag, & Partecke, 2013). For example, both resource availability and predation risk in the particular environment may determine whether an individual should behave more or less cautious during foraging (Cooper, 2000; Kortet, Hedrick, & Vainikka, 2010; Luttbeg & Sih, 2010). In general, individuals are Received: 25 October 2017 | Revised: 23 November 2017 | Accepted: 29 December 2017 DOI: 10.1111/eth.12722

On the neglected behavioural variation among neighbouring primate groups

Abstract: Behavioural variation in primates has been well studied at the level of individuals by behavioural ecologists, and more recently at a population level by cultural biologists. Behavioural differences between groups of the same population, however, have rarely been considered. Here, I review intergroup variation in universally occurring behaviours between up to six neighbouring groups of vervet monkeys. Group differences have been found in several domains including foraging, conflicts, grooming and proximity. An exclusively ecological explanation for the observed variation appears implausible, as these monkey groups have overlapping home ranges, and their ecology is therefore very similar. The presence of a genetic bias underlying the observed group differences is also implausible, as males disperse between groups at sexual maturity and multiple times within their lives creating a continuous gene flow between the six groups. This leaves socially learned group-level traditions as the most plausible explanation. I discuss ways in which this working conclusion can be tested. The likely presence of group-level traditions in close proximity, well known in humans, has rarely been considered for non-human primates and adds an important dimension to research on conformity in non-human cultures.

Olfactory eavesdropping: The odor of feathers is detectable to mammalian predators and competitors

Abstract: The role of olfactory eavesdropping in interactions between mammalian predator and prey species is well established. Bird plumage can be odorous and consequently nest predators could use odor to identify and locate avian prey, and nest competitors could use odor to assess occupancy of nest cavities by birds. However, despite extensive research on avian nest predation and competition, the costs of olfactory eavesdropping on plumage odor by nest predators or competitors remain largely unknown. We used two experiments to investigate whether feather odor is detected by marsupial species which are competitors for nest hollows and predators of eggs and nestlings of crimson rosellas, Platycercus elegans. In the first experiment, odor presentation at nest boxes utilized by ringtail possums (Pseudocheirus peregrinus) and rosellas showed that the latency of possums to enter the nest was shorter when crimson rosella odor was present compared to the controls. In the second experiment, carried out away from nest hollows, brushtail possums (Trichosurus vulpecula) discriminated odors of two predators (dingo, Canis lupus dingo, and cat, Felis catus) from crimson rosella and control odors; however, they did not discriminate between crimson rosella odor and a control. We show that marsupials may use feather odor cues to assess nest hollow status, information which could aid their detection of avian prey or their vigilance at nest hollows (for which they compete with parrots). To our knowledge, our study is the first to show that wild mammalian predators and competitors of birds respond to plumage odor at nests and suggest that odor signaling may have hitherto unrecognized costs for birds.

Locomotion is not a privilege after birth: Ultrasound images of viviparous shark embryos swimming from one uterus to the other

Abstract: Underwater ultrasound, a new tool for observing the internal body parts of aquatic animals by scuba divers, allowed us long‐term and frequent observations of the embryos of captive aquatic vertebrates. New ultrasound data of captive tawny nurse sharks (Nebrius ferrugineus) revealed that their embryos frequently migrate between the right and left uteri during gestation. This report is the first reliable evidence of active embryonic locomotion in live‐bearing vertebrates and is contradictory to the concept of “sedentary embryo” which has mainly arisen from studies of mammals. The tawny nurse shark is unique among orectolobiform sharks, in which the embryo develops by feeding on sibling eggs in utero. Thus, we hypothesized that swimming aids in an efficient search and capture of these eggs in the uterine environment.