Cues For Individual Recognition Research Articles

Chemical signals in the echidna: differences between seasons, sexes, individuals and gland types

AbstractSeasonally reproducing animals show many behavioural and physiological changes during the mating period, including increased signalling for mate attraction. Mammals often rely on chemical signals for communication and coordination of mating and other social behaviours, but our understanding of the subtleties and functions of mammalian signalling could be increased with more input from non‐model systems. We used gas chromatography–mass spectrometry and non‐parametric statistics to investigate the volatile and non‐volatile composition of odorous secretions in an egg‐laying mammal (monotreme), the short‐beaked echidna Tachyglossus aculeatus. We collected a total of 778 odorant samples from 69 wild, sexually mature individuals over 3 years at our field site in southern Tasmania. Animals were sampled during the breeding and non‐breeding seasons, as well as during hibernation. Odorants included swabs from the cloaca and ‘waxy’ secretions from putative scent glands in the cloacal wall and at the base of the spurs. Chemical profiles varied between different gland secretions and by sex and season. Female spur and cloacal wax secretion profiles had higher relative abundances of sterols, whereas male wax secretion profiles had more long chain fatty acids. Male spur secretions changed significantly during the mating season and could function in intra‐sexual competition or female mate choice. Echidna scent gland secretions also varied between individuals, suggesting olfactory cues could be used for individual recognition. Our results indicate that echidna secretions contain information that could be used by individuals to attract and locate mates during the breeding season. We also provide evidence for the potential importance of compounds traditionally classified as ‘non‐volatile’, including sterols and fatty acids, as cues for individual recognition or mate assessment.

Overview on the Diversity of Sounds Produced by Clownfishes (Pomacentridae): Importance of Acoustic Signals in Their Peculiar Way of Life

BackgroundClownfishes (Pomacentridae) are brightly colored coral reef fishes well known for their mutualistic symbiosis with tropical sea anemones. These fishes live in social groups in which there is a size-based dominance hierarchy. In this structure where sex is socially controlled, agonistic interactions are numerous and serve to maintain size differences between individuals adjacent in rank. Clownfishes are also prolific callers whose sounds seem to play an important role in the social hierarchy. Here, we aim to review and to synthesize the diversity of sounds produced by clownfishes in order to emphasize the importance of acoustic signals in their way of life.Methodology/Principal FindingsRecording the different acoustic behaviors indicated that sounds are divided into two main categories: aggressive sounds produced in conjunction with threat postures (charge and chase), and submissive sounds always emitted when fish exhibited head shaking movements (i.e. a submissive posture). Both types of sounds showed size-related intraspecific variation in dominant frequency and pulse duration: smaller individuals produce higher frequency and shorter duration pulses than larger ones, and inversely. Consequently, these sonic features might be useful cues for individual recognition within the group. This observation is of significant importance due to the size-based hierarchy in clownfish group. On the other hand, no acoustic signal was associated with the different reproductive activities.Conclusions/SignificanceUnlike other pomacentrids, sounds are not produced for mate attraction in clownfishes but to reach and to defend the competition for breeding status, which explains why constraints are not important enough for promoting call diversification in this group.

Memory for individuals: Hamsters (Mesocricetus auratus) require contact to develop multicomponent representations (concepts) of others.

In humans, individuals recognize other individuals by numerous types of independent information, such as the quality of the voice, appearance of the face, smell, gait, and posture. Humans also have integrated memories of others--that is, in response to a face or a voice the individual is recognized by name and other information about that individual is remembered. In many nonhuman species, individual recognition also occurs. Although observational studies suggest that individuals of some nonhuman species may be able to use several different cues for individual recognition, little experimental proof for this is available. Golden hamsters have at least 5 individually distinctive odors and they develop integrated, multi-odor memories (concepts) of familiar individuals, as shown by across-odor habituation experiments. Little is known, however, about the conditions that are necessary to develop such integrated memories. In these experiments we investigated what kinds of experiences were necessary for male hamsters to develop multiodor memories of females. The results show that exposure to all of the odors of another individual was not sufficient to develop such multiodor memories but that physical contact between the subjects and stimulus animals was necessary. Multiodor representations were developed after interactions with anesthetized individuals, confirming the finding that physical contact was important but also showing that interaction with an awake, behaving individual was not necessary to form multiodor representations of other individuals. We are not aware of experimental proof for integrated, multicomponant memories in any other nonhuman species.

Parturient women can recognize their infants by touch.

This article shows that parturient women can identify their newborns by tactile cues alone and that the discriminative features are learned, without intent, during routine mother-infant interactions. To test for touch recognition, mothers were instructed to stroke the hand (dorsal surface) of 3 newborns, 1 of which was her own. She then guessed which of the 3 was her own infant. The results showed that the majority of women were successful at the task if they has been with their infant for 1 hr or more since childbirth. Control experiments showed that the discrimination was not based on olfactory or other nontactile cues. It was concluded that during routine mother-infant contact, mothers learn the unique tactile features of their infant's skin and use these cues for individual recognition