Compassionate conservation is based on the ethical position that actions taken to protect biodiversity

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The ability to perceive biological motion (BM) has been demonstrated in a number of species including humans but the few studies of non-human primates have been relatively inconclusive. We investigated whether common marmosets (Callithrix jacchus) are able to perceive biological motion, using a novel method to test non-human primates. Marmosets (7 male and 7 female) were trained to remove a cover from a container and look inside it, revealing a computer screen. Then they were presented with images on this computer screen consisting of a novel BM pattern (a walking hen) and 4 manipulations of that pattern (a static frame of this pattern and inverted, scrambled, and rotating versions of the pattern). The behavioural responses of the marmosets were recorded and used to assess discrimination between stimuli. BM was attended to by females but not males, as shown by active inspection behaviour, mainly movement of the head towards the stimulus. Females paid significantly less attention to all of the other stimuli. This indicates the females' ability to attend to biological motion. Females showed slightly more attention to the inverted BM than to the static, scrambled, and rotating patterns. The males were less attentive to all of the stimuli than were the females and, unlike the females, responded to all stimuli in a similar manner. This sex difference could be due to an inability of males to recognise BM altogether or to a lesser amount of curiosity. Considered together with the findings of previous studies on chicks and humans, the results of the present study support the notion of a common mechanism across species for the detection of BM.

Australian magpies (Gymnorhina tibicen) are notable for their vocal prowess. We investigated the syringeal and respiratory dynamics of vocalization by two 6-month-old males, whose songs had a number of adult features. There was no strong lateral syringeal dominance and unilateral phonation was most often achieved by closing the syringeal valve on the contralateral side of the syrinx. Unlike other songbirds studied, magpies sometimes used an alternative syringeal motor pattern during unilateral phonation in which both sides of the syrinx are partially adducted and open to airflow. Also, in contrast to most other songbirds, the higher fundamental frequency during two-voice syllables was usually generated on the left side of the syrinx. Amplitude modulation, a prominent feature of magpie song, was produced by linear or nonlinear interactions between different frequencies which may originate either on opposite sides of the syrinx or on the same side. Pulse tones, similar to vocal fry in human speech, were present in some calls. Unlike small songbirds, the fundamental of the modal frequency can be as low as that of the pulse tone, suggesting that large birds may have evolved pulse tones to increase acoustic diversity, rather than decrease the fundamental frequency.

Marmosets, as do many other primates, live in forest environments, are group living and constantly at risk of predation. Retaining contact with one another is therefore a matter of survival. We ask here whether their contact calls (phee and twitter vocalizations) are in some way ordered acoustically by sex or age and whether the calls of older marmosets elicit different responses than those of younger marmosets. In our study, marmosets (2-14 years) were visually isolated from conspecifics and the vocal responses to each isolated caller by other marmosets in the colony were recorded. Vocal responses to phee calls largely consisted of phee calls and, less commonly, twitter calls. No differences between the responses to calls by males and females were apparent. However, we found a strong positive and significant correlation between the caller's age and the percentage of its phee calls receiving a phee response, and a significant negative correlation between the caller's age and the percentage of its phee calls receiving a twitter response. The older the marmoset, the more antiphonal calling occurred. Two-syllable phee calls were emitted more often by older marmosets (10-14 years) than by younger ones (2-6 years). Hence, we have found age-dependent differences in phee-call production and a consistent change in the response received across the adult life-span. This age-dependent effect was independent of kinship relations. This is the first evidence that marmosets distinguish age by vocal parameters alone and make social decisions based on age.

Mobbing calls are produced by many avian species as part of a defence strategy against predators. However, as most studies have described small prey species, little is known of mobbing by species large enough to inflict harm on the predator when working cooperatively. We investigated the mobbing calls of the Australian magpie (Gymnorhina tibicen tibicen), a large, territorial songbird known to be exceptionally vigilant and to attack predators. We were particularly interested in this species because it has a very large vocal repertoire. Magpie groups (N=45) in semi-rural and rural localities were presented with taxidermic specimens of three predators, two species of eagle and a monitor lizard, the latter known to be a risk to their eggs and nestlings. We identified five distinct types of alarm calls, one of which (a complex, tonal call of more than two syllables) was elicited almost exclusively by the eagles in environments where they are known to be a threat to magpies. This alarm call usually preceded intense swooping attacks of the eagle models and often continued during the attacks. A harsh and noisy call of one syllable was the most frequently produced call and appeared to indicate level of arousal. The lizard did not elicit the multi-syllable call or any swooping attacks but it did elicit the harsh call. Some other call types showed less stimulus specificity although a two-syllable call was elicited more commonly by the eagles than lizard. Hence, this species has an acoustically complex, multi-syllable alarm call to signal the presence of an aerial predator in contexts of genuine threat, and this call is markedly different from the harsh single-syllable call, which indicates arousal level and is used most frequently when mobbing a monitor lizard.

Facial expressions have been studied mainly in chimpanzees and have been shown to be important social signals. In platyrrhine and strepsirrhine primates, it has been doubted that facial expressions are differentiated enough, or the species socially capable enough, for facial expressions to be part of their communication system. However, in a series of experiments presenting olfactory, auditory and visual stimuli, we found that common marmosets (Callithrix jacchus) displayed an unexpected variety of facial expressions. Especially, olfactory and auditory stimuli elicited obvious facial displays (such as disgust), some of which are reported here for the first time. We asked whether specific facial responses to food and predator-related stimuli might act as social signals to conspecifics. We recorded two contrasting facial expressions (fear and pleasure) as separate sets of video clips and then presented these to cage mates of those marmosets shown in the images, while tempting the subject with food. Results show that the expression of a fearful face on screen significantly reduced time spent near the food bowl compared to the duration when a face showing pleasure was screened. This responsiveness to a cage mate's facial expressions suggests that the evolution of facial signals may have occurred much earlier in primate evolution than had been thought.