Wild skuas can follow human-given behavioural cues when objects resemble natural food

Abstract

The capacity to follow human cues provides animals with information about the environment and can hence offer obvious adaptive benefits. Most studies carried out so far, however, have been on captive animals with previous experience with humans. Further comparative investigation is needed to properly assess the factors driving the emergence of this capacity under natural conditions, especially in species that do not have longstanding interactions with humans. Wild brown skuas (Catharacta antarctica ssp. lonnbergi) are non-neophobic seabirds that live in human-free habitats. In test 1, we assessed this species’ capacity to use human behavioural cues (i.e., pecking at the same object previously picked up and lifted by a human experimenter) when the items presented were food objects: anthropogenic objects (wrapped muffins) and natural-food-resembling objects (plaster eggs). In test 2, we examined the response of another skua population towards non-food objects (sponges). Although all skuas in test 1 pecked at the objects, they pecked significantly more at the same previously handled items when they resembled natural food (plaster eggs). Most skuas in test 2, however, did not approach or peck at the non-food objects presented. Our results lead us to suggest that the use of human behavioural cues may be influenced by skuas’ foraging ecology, which paves the way to further field studies assessing whether this capacity is directed specifically towards food objects and/or develops after previous interaction with humans.

“Cognition in marine mammals: the strength of flexibility in adapting to marine life”

Abstract

In this theme issue, our multidisciplinary contributors highlight the cognitive adaptations of marine mammals. The cognitive processes of this group are highly informative regarding how animals cope with specifics of and changes in the environment, because, not only did modern marine mammals evolve from numerous, non-related terrestrial animals to adapt to an aquatic lifestyle, but some of these species regularly move between two worlds, land and sea. Here, we bring together scientists from different fields and take the reader on a journey that begins with the ways in which modern marine mammals (whales, dolphins, seals, sea lions and manatees) utilize their perceptual systems, next moves into studies of the constraints and power of individuals’ cognitive flexibility, and finally showcases how those systems are deployed in social and communicative contexts. Considering the cognitive processes of the different marine mammals in one issue from varying perspectives will help us understand the strength of cognitive flexibility in changing environments—in marine mammals and beyond.

Heterospecific eavesdropping on disturbance cues of a treefrog

Abstract

Alarm signals and cues are crucial to animal survival and vary greatly across species. Eavesdropping on heterospecific alarm signals and cues can provide eavesdroppers with information about potential threats. In addition to acoustic alarm signals, evidence has accumulated that chemical alarm cues and disturbance cues can also play a role in alerting conspecifics to potential danger in adult anurans (frogs and toads). However, there is very little known about whether disturbance cues are exploited by heterospecifics. In the present study, we conducted a binary choice experiment and a prey chemical discrimination experiment, respectively, to test the responses of a sympatric anuran species (red webbed treefrogs, Rhacophorus rhodopus) and a sympatric predator species (Chinese green tree vipers, Trimeresurus stejnegeri) to disturbance odors emitted by serrate-legged small treefrogs (Kurixalus odontotarsus). In the binary choice experiment, we found that the presence of disturbance odors did not significantly trigger the avoidance behavior of R. rhodopus. In the prey chemical discrimination experiment, compared with odors from undisturbed K. odontotarsus (control odors) and odorless control, T. stejnegeri showed a significantly higher tongue-flick rate in response to disturbance odors. This result implies that disturbance odor cues of K. odontotarsus can be exploited by eavesdropping predators to detect prey. Our study provides partial evidence for heterospecific eavesdropping on disturbance cues and has an important implication for understanding heterospecific eavesdropping on chemical cues of adult anurans.

Context-effect bias in capuchin monkeys (Sapajus spp.): exploring decoy influences in a value-based food choice task

Abstract

Decision making is known to be liable to several context effects. In particular, adding a seemingly irrelevant alternative (decoy) to a set of options can modify preferences: typically, by increasing choices towards whatever option clearly dominates the decoy (attraction effect), but occasionally also decreasing its appeal and generating a shift in the opposite direction (repulsion effect). Both types of decoy effects violate rational choice theory axioms and suggest dynamic processes of preference-formation, in which the value of each alternative is not determined a priori, but it is instead constructed by comparing options during the decision process. These effects are well documented, both in humans and in other species: e.g., amoebas, ants, honeybees, frogs, birds, cats, dogs. However, evidence of decoy effects in non-human primates remains surprisingly mixed. This study investigates decoy effects in capuchin monkeys (Sapajus spp.), manipulating time pressure across different conditions, to test whether such effects require time-consuming comparative processes among available alternatives. Whereas the time-dependent nature of decoy effects is a robust finding in the human literature, this is its first investigation in non-human animals. Our results show that capuchins exhibit an attraction effect with decoys targeting their preferred food, and that this effect disappears under time pressure; moreover, we observe preliminary evidence of a repulsion effect when decoys target instead the less-preferred food, possibly due to the larger distance between decoy and target in the attribute space. Taken together, these results provide valuable insight on the evolutionary roots of comparative decision making.

Killer whale innovation: teaching animals to use their creativity upon request

Abstract

Thinking flexibly is a skill that enables animals to adapt to changing environments, which enhances survival. Killer whales, Orcinus orca, as the ocean apex predator display a number of complex cognitive abilities, especially flexible thinking or creativity when it comes to foraging. In human care, smaller dolphins and other marine mammals have been trained to think creatively while under stimulus control. The results of these previous studies have demonstrated that bottlenose dolphins, Tursiops truncatus, can create original behaviors in response to an innovative cue. We trained and tested a total of nine killer whales from two different facilities on the innovate concept, using the same methodology. The killer whales ranged in age from 5 to 29 yrs with 4 females and 5 males. The results indicate that the killer whales demonstrated high fluency, originality, some elaboration, and flexibility in their behaviors. Individual variability was observed with younger animals demonstrating more variable behaviors as compared to the older animals. Males seemed to display less complex and lower energy behaviors as compared to females, but this impression may be driven by the age or size of the animal. These results support existing evidence that killer whales are dynamic in their thinking and behavior.

Through the looking glass: how do marked dolphins use mirrors and what does it mean?

Abstract

Mirror-guided self-inspection is seen as a cognitive hallmark purportedly indicating the existence of self-recognition. Only a few species of great apes have been reported to pass a standard mark test for mirror self-recognition in which animals attempt to touch a mark. In addition, evidence for passing the mark test was also reported for Asian elephants, two species of corvids, and a species of cleaner fish. Mirror self-recognition has also been claimed for bottlenose dolphins, using exposure of marked areas to a mirror as evidence. However, what counts as self-directed behaviour to see the mark and what does not has been debated. To avoid this problem, we marked the areas around both eyes of the animals at the same time, one with visible and the other with transparent dye to control for haptic cues. This allowed the animal to see the mark easily and us to investigate what side was exposed to the mirror as an indicator for mark observation. We found that the animals actively chose to inspect their visibly marked side while they did not show an increased interest in a marked conspecific in the pool. These results demonstrate that dolphins use the mirror to inspect their marks and, therefore, likely recognise a distinction between self and others.