Variation in female songbird state determines signal state needed to evoke copulation

It is the female response to male signals that determines courtship success. In most songbirds, females control reproduction via the copulation solicitation display (CSD), an innate, stereotyped posture produced in direct response to male displays. Because CSD can be elicited in the absence of males by the presentation of recorded song, CSD production enables investigations into the effects of underlying signal features and behavioral state on female mating preferences. Using computer vision to quantify CSD trajectory in female brown-headed cowbirds (Molothrus ater), we show that both song quality and a female's internal state predict CSD production, as well as the onset latency and duration of the display. We also show that CSD can be produced in a graded fashion based on both signal strength and internal state. These results emphasize the importance of underlying receiver state in determining behavioral responses and suggest that female responsiveness acts in conjunction with male signal strength to determine the efficacy of male courtship.

Acoustic coordination by allied male dolphins in a cooperative context

Synchronous displays are hallmarks of many animal societies, ranging from the pulsing flashes of fireflies, to military marching in humans. Such displays are known to facilitate mate attraction or signal relationship quality. Across many taxa, synchronous male displays appear to be driven by competition, while synchronous displays in humans are thought to be unique in that they serve a cooperative function. Indeed, it is well established that human synchrony promotes cooperative endeavours and increases success in joint action tasks. We examine another system in which synchrony is tightly linked to cooperative behaviour. Male bottlenose dolphins form long-lasting, multi-level, cooperative alliances in which they engage in coordinated efforts to coerce single oestrus females. Previous work has revealed the importance of motor synchrony in dolphin alliance behaviour. Here, we demonstrate that allied dolphins also engage in acoustic coordination whereby males will actively match the tempo and, in some cases, synchronize the production of their threat vocalization when coercing females. This finding demonstrates that male dolphins are capable of acoustic coordination in a cooperative context and, moreover, suggests that both motor and acoustic coordination are features of coalitionary behaviour that are not limited to humans.

Maristella, a new bioluminescent ostracod genus in the Myodocopida (Cypridinidae)

One new species from Belize and six described species from Panama of bioluminescent ostracods (Myodocopida: Cypridinidae) are compared and placed in the new genus, Maristellagen. nov.. Maristella belongs to a diverse Caribbean clade of bioluminescent ostracods in which males perform species-specific luminescent courtship displays. Other genera of the clade include Enewton, Photeros, Konickeria and, nominally, Vargula.Maristella is likely the most species-rich genus in the clade. Maristella chicoi sp. nov., from Belize, is described as the type species. Species from Panama reassigned to Maristella are Vargula ignitula, V. lucidella, V. micamacula, V. noropsela, V. psammobia, V. scintilla. New information is presented on the sixth and eighth limbs of the species from Panama, providing additional characters for distinguishing taxa. Maristella is the only genus that contains species with lateral or diagonal luminescent courtship displays. Maristella chicoi has male displays oriented horizontal to the substrate and showing high levels of entrainment. The displays run in near-parallel bifurcations resulting in spectacular fan-like radiations of light pulse trains. The description of Maristella advances the taxonomy of the highly diverse Caribbean clade that has become a model system for studying the evolution of bioluminescence and the role of luminescent displays in speciation.

Five Cases of Dental Anomalies Attributable to Congenital Syphilis from Early 20th Century American Anatomical Collections

Specific dental abnormalities are considered pathognomonic of congenital syphilis (CS); however, European physicians recognized their variation during the late 19th to mid 20th centuries. Observations of syphi-lis-related dental abnormalities in American individuals from similar time periods are made to determine types of variation among the American population.From a survey of the Smithsonian Institution’s National Museum of Natural History anatomical human skeletal collection, five individuals demonstrated dental characteristics consistent with CS (P00011R, P219398, P000707, P000679, and P000161). Hutchinson’s three categories of dental anomalies were used to describe variations among syphilitic individuals.Previously identified pathological dental characteristics related to CS were present in the analyzed individuals. P00011R, 24-year-old Black female, has a maxillary right Moon’s molar. P219398, approximately 20-year-old Black female, has Hutchinson’s incisors and Fournier’s molars. P000707, 26-year-old Black male, displays severe hypoplasia on all incisors, canines and maxillary first molars. P000679, 33-year-old Black female has “screw-driver” shaped maxillary central incisors, altered occlusal morphology of first maxillary molars and hypoplasia. P000161, 45-year-old Black female, demonstrates severe hypoplasia on incisors and canines (molars lost).“Classic” dental characteristics of CS are not ubiquitous to all identified cases. This study exemplifies that den-tal anomalies associated with CS do not all have to be present for diagnosis. Although other causes for some of these anomalies are possible, observations in these five cases are most consistent with CS.

Mate choice in the eye and ear of the beholder? Female multimodal sensory configuration influences her preferences

A common assumption in sexual selection studies is that receivers decode signal information similarly. However, receivers may vary in how they rank signallers if signal perception varies with an individual's sensory configuration. Furthermore, receivers may vary in their weighting of different elements of multimodal signals based on their sensory configuration. This could lead to complex levels of selection on signalling traits. We tested whether multimodal sensory configuration could affect preferences for multimodal signals. We used brown-headed cowbird ( Molothrus ater ) females to examine how auditory sensitivity and auditory filters, which influence auditory spectral and temporal resolution, affect song preferences, and how visual spatial resolution and visual temporal resolution, which influence resolution of a moving visual signal, affect visual display preferences. Our results show that multimodal sensory configuration significantly affects preferences for male displays: females with better auditory temporal resolution preferred songs that were shorter, with lower Wiener entropy, and higher frequency; and females with better visual temporal resolution preferred males with less intense visual displays. Our findings provide new insights into mate-choice decisions and receiver signal processing. Furthermore, our results challenge a long-standing assumption in animal communication which can affect how we address honest signalling, assortative mating and sensory drive.

Male cowbirds vary the attractiveness of courtship songs with changes in the social context

Courtship-signalling theory often incorporates the assumption that males must consistently produce the highest-intensity displays they can achieve, thereby indicating their underlying quality to females. Contest-signalling theory, in contrast, assumes that flexible signal performance is routine. The two frameworks thereby suggest conflicting predictions about male flexibility when the same signal operates in both intrasexual and intersexual communication. Sexual competition often occurs within complex social environments where male displays can be received by potential mates, rivals, or both at once. In brown-headed cowbirds’ breeding flocks, for example, multiple males sometimes vie directly for a single female’s attention; at other times males have opportunities to sing to females without interference. We tested whether cowbirds vary the intensity of their signalling across contexts like these. We recorded songs from males courting females both with and without a male competitor in sight. We then played those recordings to solitary, naïve females in sound attenuation chambers, and also to a naïve aviary-housed flock. The songs males had produced when they could see their competitors were more attractive, eliciting more copulatory postures from naïve females and more approaches from birds in the flock. Results suggest high-intensity displays function within a larger, flexible signalling strategy in this species, and the varying audience composition that accompanies social complexity may demand flexible signalling even in classic display behaviours such as birdsong.

Sex or power? The function of male displays in rhesus macaques

Male behavioral displays (e.g., branch-shaking) are common across Anthropoidea, but their function remains unclear. We examined free-ranging rhesus macaques on Cayo Santiago, Puerto Rico, to test three major hypotheses for the function of male displays: (1) mate attraction, (2) mate guarding and (3) male–male dominance competition. Focal and ad libitum behavioural data were recorded for 21 adult males across 9 groups during the mating season. Display rates were calculated for each male in each context (i.e., agonistic, mating). In stable groups, males with high mating success displayed more during consortships than in other contexts and displays were more likely to follow than to precede copulation, whereas males in unstable groups were more likely to displays in agonistic contexts. These results suggest that mate guarding and male–male dominance competition are the primary functions of male display behaviours in rhesus macaques.

The limits of sexual conflict in the narrow sense: new insights from waterfowl biology

Sexual conflict occurs when the evolutionary interests of the sexes differ and it broadly applies to decisions over mating, fertilization and parental investment. Recently, a narrower view of sexual conflict has emerged in which direct selection on females to avoid male-imposed costs during mating is considered the distinguishing feature of conflict, while indirect selection is considered negligible. In this view, intersexual selection via sensory bias is seen as the most relevant mechanism by which male traits that harm females evolve, with antagonistic coevolution between female preferences and male manipulation following. Under this narrower framework, female preference and resistance have been synonymized because both result in a mating bias, and similarly male display and coercion are not distinguished. Our recent work on genital evolution in waterfowl has highlighted problems with this approach. In waterfowl, preference and resistance are distinct components of female phenotype, and display and coercion are independent male strategies. Female preference for male displays result in mate choice, while forced copulations by unpreferred males result in resistance to prevent these males from achieving matings and fertilizations. Genital elaborations in female waterfowl appear to function in reinforcing female preference to maintain the indirect benefits of choice rather than to reduce the direct costs of coercive mating. We propose a return to a broader view of conflict where indirect selection and intrasexual selection are considered important in the evolution of conflict.