Giraffes make decisions based on statistical information.

The ability to make inferences based on statistical information has so far been tested only in animals having large brains in relation to their body size, like primates and parrots. Here we tested if giraffes (Giraffa camelopardalis), despite having a smaller relative brain size, can rely on relative frequencies to predict sampling outcomes. We presented them with two transparent containers filled with different quantities of highly-liked food and less-preferred food. The experimenter covertly drew one piece of food from each container, and let the giraffe choose between the two options. In the first task, we varied the quantity and relative frequency of highly-liked and less-preferred food pieces. In the second task, we inserted a physical barrier in both containers, so giraffes only had to take into account the upper part of the container when predicting the outcome. In both tasks giraffes successfully selected the container more likely to provide the highly-liked food, integrating physical information to correctly predict sampling information. By ruling out alternative explanations based on simpler quantity heuristics and learning processes, we showed that giraffes can make decisions based on statistical inferences.

Innovation across 13 ungulate species: problem solvers are less integrated in the social group and less neophobic.

Innovation is the ability to solve new problems or find novel solutions to familiar problems, and it is known to provide animals with crucial fitness benefits. Although this ability has been extensively studied in some taxa, the factors that predict innovation within and across species are still largely unclear. In this study, we used a novel foraging task to test 111 individuals belonging to 13 ungulate species-a still understudied taxon. To solve the task, individuals had to open transparent and opaque cups with food rewards, by removing their cover. We assessed whether individual factors (neophobia, social integration, sex, age, rank) and socio-ecological factors (dietary breadth, fission-fusion dynamics, domestication, group size) predicted participation and performance in the task. Using a phylogenetic approach, we showed that success was higher for less neophobic and socially less integrated individuals. Moreover, less neophobic individuals, individuals of domesticated species and having higher fission-fusion dynamics were more likely to participate in the task. These results are in line with recent literature suggesting a central role of sociality and personality traits to successfully deal with novel challenges, and confirm ungulates as a promising taxon to test evolutionary theories with a comparative approach.

Neophobia in 10 ungulate species-a comparative approach.

ABSTRACT: Neophobia (the fearful reaction to novel stimuli or situations) has a crucial effect on individual fitness and can vary within and across species. However, the factors predicting this variation are still unclear. In this study, we assessed whether individual characteristics (rank, social integration, sex) and species socio-ecological characteristics (dietary breadth, group size, domestication) predicted variation in neophobia. For this purpose, we conducted behavioral observations and experimental tests on 78 captive individuals belonging to 10 different ungulate species-an ideal taxon to study inter-specific variation in neophobia given their variety in socio-ecological characteristics. Individuals were tested in their social groups by providing them with familiar food, half of which had been positioned close to a novel object. We monitored the individual latency to approach and eat food and the proportion of time spent in its proximity. Using a phylogenetic approach and social network analyses, we showed that across ungulate species neophobia was higher in socially more integrated individuals, as compared to less integrated ones. In contrast, rank and sex did not predict inter-individual differences in neophobia. Moreover, species differed in their levels of neophobia, with Barbary sheep being on average less neophobic than all the other study species. As group size in Barbary sheep was larger than in all the other study species, these results support the hypothesis that larger group size predicts lower levels of neophobia, and confirm ungulates as a highly promising taxon to study animal behavior and cognition with a comparative perspective. SIGNIFICANCE STATEMENT: In several species, individuals may respond fearfully to novel stimuli, therefore reducing the risks they may face. However, it is yet unclear if certain individuals or species respond more fearfully to novelty. Here, we provided food to 78 individual ungulates with different characteristics (e.g., sex, rank, social integration, group size, domestication, dietary breadth) in different controlled conditions (e.g., when food was close to novel or to familiar objects). Across species, we found that socially integrated individuals responded more fearfully in all species. Moreover, being in larger groups decreased the probability of fearfully responding to novelty. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00265-021-03041-0.

Problem solving in European bison (Bison bonasus): two experimental approaches.

The ability to solve novel problems is crucial for individual fitness. However, studies on problem solving are usually done on few taxa, with species with low encephalization quotient being rarely tested. Here, we aimed to study problem solving in a non-domesticated ungulate species, European bison, with two experimental tasks. In the first task, five individuals were presented with a hanging barrel filled with food, which could either be directly accessed (control condition) or which could only be reached by pushing a tree stump in the enclosure below it and stepping on it (experimental condition). In the second task, five individuals were repeatedly fed by an experimenter using a novel bucket to retrieve food from a bag. Then, three identical buckets were placed in the enclosure, while the experimenter waited outside with the bag without feeding the bison, either with a bucket (control condition) or without it (experimental condition). In the first task, no bison moved the stump behind the barrel and/or stepped on it to reach the food. In the second task, two individuals solved the task by pushing the bucket within the experimenter's reach, twice in the experimental and twice in the control condition. We suggest that bison showed a limited ability to solve novel problems, and discuss the implications for their understanding of the functional aspects of the tasks.

Giraffes go for more: a quantity discrimination study in giraffes (Giraffa camelopardalis).

Many species, including humans, rely on an ability to differentiate between quantities to make decisions about social relationships, territories, and food. This study is the first to investigate whether giraffes (Giraffa camelopardalis) are able to select the larger of two sets of quantities in different conditions, and how size and density affect these decisions. In Task 1, we presented five captive giraffes with two sets containing a different quantity of identical foods items. In Tasks 2 and 3, we also modified the size and density of the food reward distribution. The results showed that giraffes (i) can successfully make quantity judgments following Weber's law, (ii) can reliably rely on size to maximize their food income, and (iii) are more successful when comparing sparser than denser distributions. More studies on different taxa are needed to understand whether specific selective pressures have favored the evolution of these skills in certain taxa.

Gaze Following in Ungulates: Domesticated and Non-domesticated Species Follow the Gaze of Both Humans and Conspecifics in an Experimental Context.

Gaze following is the ability to use others' gaze to obtain information about the environment (e.g., food location, predators, and social interactions). As such, it may be highly adaptive in a variety of socio-ecological contexts, and thus be widespread across animal taxa. To date, gaze following has been mostly studied in primates, and partially in birds, but little is known on the gaze following abilities of other taxa and, especially, on the evolutionary pressures that led to their emergence. In this study, we used an experimental approach to test gaze following skills in a still understudied taxon, ungulates. Across four species (i.e., domestic goats and lamas, and non-domestic guanacos and mouflons), we assessed the individual ability to spontaneously follow the gaze of both conspecifics and human experimenters in different conditions. In line with our predictions, species followed the model's gaze both with human and conspecific models, but more likely with the latter. Except for guanacos, all species showed gaze following significantly more in the experimental conditions (than in the control ones). Despite the relative low number of study subjects, our study provides the first experimental evidence of gaze following skills in non-domesticated ungulates, and contributes to understanding how gaze following skills are distributed in another taxon-an essential endeavor to identify the evolutionary pressures leading to the emergence of gaze following skills across taxa.

Innovation in wild Barbary macaques (Macaca sylvanus).

Innovation is the ability to solve novel problems or find novel solutions to familiar problems, and it is known to affect fitness in both human and non-human animals. In primates, innovation has been mostly studied in captivity, although differences in living conditions may affect individuals' ability to innovate. Here, we tested innovation in a wild group of Barbary macaques (Macaca sylvanus). In four different conditions, we presented the group with several identical foraging boxes containing food. To understand which individual characteristics and behavioural strategies best predicted innovation rate, we measured the identity of the individuals manipulating the boxes and retrieving the food, and their behaviour during the task. Our results showed that success in the novel task was mainly affected by the experimental contingencies and the behavioural strategies used during the task. Individuals were more successful in the 1-step conditions, if they participated in more trials, showed little latency to approach the boxes and mainly manipulated functional parts of the box. In contrast, we found no effect of inhibition, social facilitation and individual characteristics like sex, age, rank, centrality, neophobia and reaction to humans, on the individuals' ability to innovate.

Object permanence in Giraffa camelopardalis: First steps in giraffes' physical cognition.

Although behavior, biology, and ecology of giraffes have been widely studied, little is known about their cognition. Giraffes' feeding ecology and their fission-fusion social dynamics are comparable with those of chimpanzees (Pan troglodytes), suggesting that they might have complex cognitive abilities. To assess this, we tested 6 captive giraffes on their object permanence, short-term memory, and ability to use acoustic cues to locate food. First, we tested whether giraffes understand that objects continue to exist even when they are out of sight. Giraffes saw one of two opaque containers containing food, then containers were closed, and 2 s later giraffes could choose one. Second, we measured giraffes' memory repeating the procedure but with a delay of 30 s, 60 s, or 2 min between closing the containers and subjects' choice. Finally, we investigated whether giraffes could locate food inside one of two identical opaque containers, when the only cue provided was the sound made by food when shaking the baited container, or the lack of sound when shaking the empty container. Our results show that giraffes form mental representations of completely hidden objects, but may not store them for longer than 30 s. Moreover, they rely on stimulus enhancement rather than acoustic cues to locate food, when no visual cues are provided. Finally, we argue that giraffes and other ungulates might be a suitable model to investigate the evolution of complex cognitive abilities from a comparative perspective. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Quantity discrimination in angelfish (Pterophyllum scalare) is maintained after a 30-s retention interval in the large but not in the small number range.

The ability to discriminate between sets that differ in the number of elements can be useful in different contexts and may have survival and fitness consequences. As such, numerical/quantity discrimination has been demonstrated in a diversity of animal species. In the laboratory, this ability has been analyzed, for example, using binary choice tests. Furthermore, when the different number of items first presented to the subjects are subsequently obscured, i.e., are not visible at the moment of making a choice, the task requires memory for the size of the sets. In previous work, angelfish (Pterophyllum scalare) have been found to be able to discriminate shoals differing in the number of shoal members both in the small (less than 4) and the large (4 or more) number range, and they were able to perform well even when a short memory retention interval (2-15 s) was imposed. In the current study, we increased the retention interval to 30 s during which the shoals to choose between were obscured, and investigated whether angelfish could show preference for the larger shoal they saw before this interval. Subjects were faced with a discrimination between numerically small shoals (≤4 fish) and also between numerically large (≥4 fish) shoals of conspecifics. We found angelfish not to be able to remember the location of larger versus smaller shoals in the small number range, but to exhibit significant memory for the larger shoal in the large number range as long as the ratio between these shoals was at least 2:1. These results, together with prior findings, suggest the existence of two separate quantity estimation systems, the object file system for small number of items that does not work with the longer retention interval and the analogue magnitude system for larger number of items that does.