[Which place has experimentation in ethology?] / Quelle place pour l'expérimentation en éthologie ?

The experimental approach has been at the center of my thoughts since my baccalaureate of "experimental sciences". Trained in neurosciences, I very quickly chose the field of ethology, thinking I would escape certain experimental approaches and offer myself research more respectful of animal life. Today, I have to note that this option did not necessarily lead to what I had imagined. I have been both the witness and the actor of practices that deserve attention. This path, punctuated by an evolution of the conceptions of our relations with living beings, leads me to question the ethics, sometimes contradictory, of action and knowledge.

Title: Quelle place pour l'expérimentation en éthologie ? Abstract: La démarche expérimentale est au centre de mes réflexions depuis mon baccalauréat « sciences ex ¼. Formé aux neurosciences, j'ai très vite choisi l'éthologie de terrain, pensant échapper à certaines démarches expérimentales et m'offrir des activités de recherche plus respectueuses de la vie animale. Aujourd'hui, je dois constater que cette option n'aboutit pas forcément à ce que j'avais imaginé. J'ai été à la fois le témoin et l'acteur de pratiques qui méritent attention. Ce parcours, jalonné par une évolution des conceptions de nos relations avec les être animés, me conduit à questionner les éthiques, parfois contradictoires, de l'action et de la connaissance.

Bilateral coordination and the motor basis of female preference for sexual signals in canary song.

The preference of female songbirds for particular traits in the songs of courting males has received considerable attention, but the relationship of preferred traits to male quality is poorly understood. Female domestic canaries (Serinus canaria, Linnaeus) preferentially solicit copulation with males that sing special high repetition rate, wide-band, multi-note syllables, called 'sexy' or A-syllables. Syllables are separated by minibreaths but each note is produced by pulsatile expiration, allowing high repetition rates and long duration phrases. The wide bandwidth is achieved by including two notes produced sequentially on opposite sides of the syrinx, in which the left and right sides are specialized for low or high frequencies, respectively. The emphasis of low frequencies is facilitated by a positive relationship between syllable repetition rate and the bandwidth of the fundamental frequency of notes sung by the left syrinx, such that bandwidth increases with increasing syllable repetition rate. The temporal offset between notes prevents cheating by unilaterally singing a note on the left side with a low fundamental frequency and prominent higher harmonics. The syringeal and respiratory motor patterns by which sexy syllables are produced support the hypothesis that these syllables provide a sensitive vocal-auditory indicator of a male's performance limit for the rapid, precisely coordinated interhemispheric switching, which is essential for many sensory and motor processes involving specialized contributions from each cerebral hemisphere.

Amplitude modulation of sexy phrases is salient for song attractiveness in female canaries (Serinus canaria).

Song discrimination and recognition in songbird species have usually been studied by measuring responses to song playbacks. In female canaries, Serinus canaria, copulation solicitation displays (CSDs) are used as an index of female preferences, which are related to song recognition. Despite the fact that many studies underline the role of song syntax in this species, we observed that short segments of songs (a few seconds long) are enough for females to discriminate between conspecific and heterospecific songs, whereas such a short duration is not sufficient to identify the syntax rules. This suggests that other cues are salient for song recognition. In this experiment, we investigated the influence of amplitude modulation (AM) on the responses (CSDs) of female canaries to song playbacks. We used two groups of females: (1) raised in acoustic isolation and (2) raised in normal conditions. When adult, we tested their preferences for sexy phrases with different AMs. We broadcast three types of stimuli: (1) songs with natural canary AM, (2) songs with AM removed, or (3) song with wren Troglodytes troglodytes AM. Results indicate that female canaries prefer and have predispositions for a song type with the natural canary AM. Thus, this acoustic parameter is a salient cue for song attractiveness.

Finding good acoustic features for parrot vocalizations: the feature generation approach.

A crucial step in the understanding of vocal behavior of birds is to be able to classify calls in the repertoire into meaningful types. Methods developed to this aim are limited either because of human subjectivity or because of methodological issues. The present study investigated whether a feature generation system could categorize vocalizations of a bird species automatically and effectively. This procedure was applied to vocalizations of African gray parrots, known for their capacity to reproduce almost any sound of their environment. Outcomes of the feature generation approach agreed well with a much more labor-intensive process of a human expert classifying based on spectrographic representation, while clearly out-performing other automated methods. The method brings significant improvements in precision over commonly used bioacoustical analyses. As such, the method enlarges the scope of automated, acoustics-based sound classification.

Referential learning of French and Czech labels in African grey parrots (Psittacus erithacus): different methods yield contrasting results.

Some African grey parrots (Psittacus erithacus), the most famous being Pepperberg's parrot Alex, are able to imitate human speech and produce labels referentially. In this study, the aim was to teach ten African grey parrots from two laboratories to label items. Training three parrots from the first laboratory for several months with the Model/Rival method, developed by Pepperberg, in which two humans interact in front of the subject to demonstrate the use of a label, led to disappointing results. Similarly, seven parrots from the second laboratory, having been trained with several variants of Model/Rival attained little success. After the informal observation of the efficiency of other methods (i.e. learning to imitate labels either spontaneously or with specific learning methods and use of these labels referentially), four different teaching methods were tested with two birds: the Model/Rival; Repetition/Association which consisted of repeating a label and presenting the item only when the parrot produced the label; Intuitive in which the experimenter handled an item and repeated its name in front of the subject; Diffusion in which labels with either variable or flat intonation were played back daily to parrots. One bird learned three labels, one of which was used referentially, with the Repetition/Association method. He learned one label non-referentially with the Model/Rival but no labels were acquired using the other methods. The second bird did not learn any labels. This study demonstrates that different methods can be efficient to teach labels referentially and it suggests that rearing conditions and interindividual variability are important features when assessing learning ability of African grey parrots.

Conspecific discrimination in an object-choice task in African grey parrots (Psittacus erithacus).

Living in social groups presents the opportunity to use information provided by other individuals. Several animal species emit specific vocalizations when they find food. Here, we investigate whether African grey parrots (Psittacus erithacus) use vocal and non-vocal information provided by a conspecific in order to find a hidden food source. One subject was attracted by the presence or the vocalizations of a subordinate conspecific, but not of a dominant, which brings us to hypothesize that parrots could be capable of individual vocal discrimination.

Spontaneous categorization of vocal imitations in African grey parrots (Psittacus erithacus).

The ability to categorize elements of the environment is a fundamental aspect of information processing. Many experiments demonstrate the ability of birds and non-human primates to classify items according to their perceptual similarities. Few data are available regarding spontaneous classification of items according to a non-perceptual account in non-human animals. Here, we report unexpected results obtained with African grey parrots learning the referential use of French labels. Parrots did not learn the correct labels but they spontaneously produced more labels corresponding to food when a food item was presented to them and more labels corresponding to an object when shown an object item, although they were never rewarded for doing so. These results demonstrate a form of spontaneous categorization by using vocal imitation of the human language.

The discrimination of discrete and continuous amounts in African grey parrots (Psittacus erithacus).

A wealth of research in infants and animals demonstrates discrimination of quantities, in some cases nonverbal numerical perception, and even elementary calculation capacities. We investigated the ability of three African grey parrots (Psittacus erithacus) to select the largest amount of food between two sets, either discrete food items (experiment 1) or as volume of a food substance (experiment 2). The two amounts were presented simultaneously and were visible at the time of choice. Parrots were tested several times for all possible combinations between 1 and 5 seeds or 0.2 and 1 ml of food substance. In both conditions, subjects performed above chance for almost all combinations. Accuracy was negatively correlated with the ratio, that is performance improved with greater differences between amounts. Therefore, these results with both individual items and volume discrimination suggest that parrots use an analogue of magnitude, rather than object-file mechanisms to quantify items and substances.

Use of experimenter-given cues by African gray parrots (Psittacus erithacus).

One advantage of living in a social group is the opportunity to use information provided by other individuals. Social information can be based on cues provided by a conspecific or even by a heterospecific individual (e.g., gaze direction, vocalizations, pointing gestures). Although the use of human gaze and gestures has been extensively studied in primates, and is increasingly studied in other mammals, there is no documentation of birds using these cues in a cooperative context. In this study, we tested the ability of three African gray parrots to use different human cues (pointing and/or gazing) in an object-choice task. We found that one subject spontaneously used the most salient pointing gesture (looking and steady pointing with hand at about 20 cm from the baited box). The two others were also able to use this cue after 15 trials. None of the parrots spontaneously used the steady gaze cues (combined head and eye orientation), but one learned to do so effectively after only 15 trials when the distance between the head and the baited box was about 1 m. However, none of the parrots were able to use the momentary pointing nor the distal pointing and gazing cues. These results are discussed in terms of sensitivity to joint attention as a prerequisite to understand pointing gestures as it is to the referential use of labels.

Women use voice parameters to assess men's characteristics.

The purpose of this study was: (i) to provide additional evidence regarding the existence of human voice parameters, which could be reliable indicators of a speaker's physical characteristics and (ii) to examine the ability of listeners to judge voice pleasantness and a speaker's characteristics from speech samples. We recorded 26 men enunciating five vowels. Voices were played to 102 female judges who were asked to assess vocal attractiveness and speakers' age, height and weight. Statistical analyses were used to determine: (i) which physical component predicted which vocal component and (ii) which vocal component predicted which judgment. We found that men with low-frequency formants and small formant dispersion tended to be older, taller and tended to have a high level of testosterone. Female listeners were consistent in their pleasantness judgment and in their height, weight and age estimates. Pleasantness judgments were based mainly on intonation. Female listeners were able to correctly estimate age by using formant components. They were able to estimate weight but we could not explain which acoustic parameters they used. However, female listeners were not able to estimate height, possibly because they used intonation incorrectly. Our study confirms that in all mammal species examined thus far, including humans, formant components can provide a relatively accurate indication of a vocalizing individual's characteristics. Human listeners have the necessary information at their disposal; however, they do not necessarily use it.

Bilateral song production in domestic canaries.

We studied the mechanism of song production in the outbred common or domestic canary (Serinus canaria). The contribution that each side of the syrinx makes to song was investigated by observing the effect of unilaterally occluding the left or right primary bronchus, followed by section of the ipsilateral branch of the tracheosyringeal nerve. In other birds with a bilaterally intact vocal system we monitored airflow through each side of the syrinx, together with subsyringeal pressure, during spontaneous song. Song production by domestic canaries is not strongly lateralized as it is in the conspecific song-bred waterslager strain. Some syllables are produced entirely on the left or right side of the syrinx, whereas others contain sequential contributions from each side. Low fundamental frequencies are produced with the left syrinx and high frequencies by the right syrinx, increasing the frequency range of domestic canary song compared to that of the waterslager strain. Midrange frequencies can be generated by either side. Syllables at repetition rates below about 25 s(-1) were accompanied by minibreaths, which were usually bilateral. Unilateral minibreaths were typically on the left side. At higher syllable repetition rates, minibreaths were replaced by a respiratory pattern of pulsatile expiration. Our data show that strong unilateral dominance in song production, present in the waterslager strain, is not a trait of the species as a whole and that the pattern of song lateralization can be altered by selective breeding for particular song characteristics.

Female canaries produce eggs with greater amounts of testosterone when exposed to preferred male song.

Male birdsong has a great influence in the stimulation of female reproduction. However, female physiological responsiveness to song may depend on the degree of complexity of male song. This is expected because females of iteroparous organisms may increase their fitness by matching their reproductive investment to the predicted value of each reproductive attempt. To the extent that the expression of male ornaments is a signal of male quality, we expect females to increase their investment when paired to highly ornamented males. However, female investment may be cryptic and difficult to detect, such as androgen content in the eggs. In this study, we exposed female canaries (Serinus canaria) to attractive and unattractive song repertoires using a crossover design. As predicted, females invested greater concentrations of testosterone in their eggs when exposed to attractive repertoires than when exposed to unattractive repertoires. This implies that song repertoires convey important information about the reproductive value of a given male and suggests that testosterone deposition in egg yolk may be costly.

Directional female preference for an exaggerated male trait in canary (Serinus canaria) song.

Motor constraints on vocal production impose a trade-off between trill rate and frequency bandwidth within birdsong. We tested whether domesticated canary (Serinus canaria) females, reared either in acoustic isolation or in aviary conditions, had a preference for broad bandwidth songs with artificially increased syllable rates. The copulation solicitation display (CSD) was used as an index of female preference. As predicted, both naive and experienced females were especially responsive to syllables with a broad bandwidth emitted at an artificially increased rate. Female preference for supernormal stimuli provide support for the honest-signalling hypothesis and our results are consistent with recent findings indicating that production of song phrases maximizing both bandwidth and syllable rate may be a reliable indicator of male physical or behavioural qualities. We suggest that female preference for vocal emissions, which simultaneously maximize these two parameters, could be a widespread pattern within songbirds.