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Animal communication depends on signals conveying information to a receiver who must perceive and decode them. Signals involved in territoriality are usually complex stimuli that should be correctly interpreted to avoid unnecessary conflicts. Lacertids use both visual and chemical stimuli in modulating their aggressive response against conspecifics and the rival’s size is one of the most important information, affecting the success probability in combat. To assess the actual ability of decoding information about a rival’s size based on its chemical stimulus alone, 60 males of Podarcis muralis were tested for three consecutive days in an arena bearing a mirror (to simulate an equal-sized intruder), and the chemical cues (femoral secretions) from an unknown individual of different size. Significant differences were observed in tongue-flicks number, which grew as the size difference between the focal lizard and the secretion donor decreased. This can be interpreted as the need for the lizard to better evaluate the potential competitor’s characteristics. The size difference also affected the number of bites against the mirror. They increased when the size of the focal lizard was larger than the donor triggering the aggressive response with a higher probability of winning the contest. This confirms that the focal lizard had correctly decoded the information about the opponent’s size by chemical stimulus. Although previous studies have shown that some components of the chemical signals are potentially informative about the signaler’s size, this is the first demonstration that male P. muralis is actually able to decode and use such information.

The courtship and mounting behavior of promiscuous tortoises is based on a multiple signaling system that includes visual, olfactory, tactile, and acoustic signals. Vocalizations related to mounting seem to be particularly intriguing because tortoises vocalize mainly at this time. Vocalizations and courtship behavior might be costly for males, and if these costs increase differentially for different males, then the potential exists for vocalizations and displays to reveal male individual quality on which females could base their mate choice. In the present study, by using individuals breeding in seminatural enclosures, we experimentally investigated whether the mounting call of male Hermann’s tortoises (Testudo hermanni) represents a relevant stimulus to both males and females. We also looked for potential preference toward different acoustic stimuli in order to determine which call features, if any, played a role in attracting potential partners or deterring rivals. Females were sensitive to call playback, whereas males apparently paid little attention to playback. In addition, females showed a significant preference toward high-pitched calls emitted at high rate. Also, females exhibited a strong tendency toward short-duration calls. Because call rate is related to hematocrit in Hermann’s tortoise males, by responding to fast-rate calls females are also choosing high-quality partners as sires of their offspring. This is the first study in which an attractive function of tortoise vocalizations has been documented. Key words: call features, calling rate, mate choice, playback experiments, tortoise, Testudo hermanni. [Behav Ecol]

Altricial offspring of birds solicit food provisioning by complex begging displays, implying acoustic and visual signals. Different components of begging behavior may function as reliable signals of offspring state and thus reproductive value, on which parents base optimal parental decisions about allocation of critical resources (e.g., food). We experimentally manipulated components of general condition of nestling barn swallows (Hirundo rustica) by (1) altering brood size by cross-fostering an unbalanced number of nestlings between pairs of synchronous broods and thus manipulating the level of within-brood competition for food, (2) injecting some nestlings with a harmless immunogen, simulating an infection, and (3) preventing part of the nestlings from receiving food for a short period while establishing control groups. We recorded rate of begging response by individual nestlings as parents visited the nest and recorded begging calls using a DAT recorder to analyze six sonagraphic features of vocalizations. Our factorial experiment revealed that nestlings deprived of food begged more frequently when parents visited the nest compared to their non--food-deprived nest mates. Food deprivation increased duration of syllables forming begging calls, whereas brood size enlargement resulted in increased latency of response to parental calls. Heavy nestlings in good body condition vocalized at a relatively low peak frequency. To our knowledge, this is the first study in which begging rate and sonagraphic structure of begging calls are shown to reliably reveal a diverse set of components of offspring general state, on which parental decisions may be based. Copyright 2002.

Male secondary sexual characters may have evolved as intra- or intersexual signals of male phenotypic or genetic quality. In birds, singing performance may have the function to honestly reveal .health and vigor of individual males. Infectious diseases and poor body conditions would therefore be expected to negatively influence singing performance. Since bird pathogens are known to elicit both a humoral and a cell-mediated immune response, it can be predicted that a negative relationship exists between singing performance and activity of the immune system. This prediction was tested for the first time in this correlational study. The relationships between song rate and features and hematological variables (concentration of leukocytes in peripheral