Facial age recognition based on deep manifold learning.

Facial age recognition has been widely used in real-world applications. Most of current facial age recognition methods use deep learning to extract facial features to identify age. However, due to the high dimension features of faces, deep learning methods might extract a lot of redundant features, which is not beneficial for facial age recognition. To improve facial age recognition effectively, this paper proposed the deep manifold learning (DML), a combination of deep learning and manifold learning. In DML, deep learning was used to extract high-dimensional facial features, and manifold learning selected age-related features from these high-dimensional facial features for facial age recognition. Finally, we validated the DML on Multivariate Observations of Reactions and Physical Health (MORPH) and Face and Gesture Recognition Network (FG-NET) datasets. The results indicated that the mean absolute error (MAE) of MORPH is 1.60 and that of FG-NET is 2.48. Moreover, compared with the state of the art facial age recognition methods, the accuracy of DML has been greatly improved.

The role of visual cues in mother-pup reunions in a colonially breeding mammal.

Parental care is an important factor influencing offspring survival and adult reproductive success in many vertebrates. Parent-offspring recognition ensures care is only directed to filial young, avoiding the costs of misallocated resource transfer. It is essential in colonial mammal species, such as otariids (fur seals and sea lions), in which repeated mother-offspring separations increase the risk of misdirecting maternal effort. Identification of otariid pups by mothers is known to be multi-modal, yet the role of visual cues in this process remains uncertain. We used three-dimensional visual models to investigate the importance of visual cues in maternal recognition of pups in Australian sea lions (Neophoca cinerea). We showed that the colour pattern of pup pelage in the absence of any other sensory cues served to attract the attention of females and prompt investigation. Furthermore, females were capable of accurately distinguishing between models imitating the age-class of their own pup and those resembling older or younger age-classes. Our results suggest that visual cues facilitate age-class discrimination of pups by females and so are likely to play an important role in mother-pup reunions and recognition in otariid species.

Chemosensory age discrimination in the snake Boa constrictor (Serpentes: Boidae)

Many snakes are able to use their chemosensory system to detect scent of conspecifics, which is important in many social contexts. Age discrimination based on chemical cues may be especially important to ensure access to sexually mature potential partners. In this study, we used 24 individual Boa constrictor snakes (12 adults mature and 12 non-mature individuals) that had been captured in different areas of Ecuador, and were maintained in captivity at the Vivarium of Quito. We used tongue-flick experiments to examine whether these snakes were able to discriminate between scents from mature and non-mature individuals. Results showed that B. constrictor snakes used chemical cues to recognize conspecifics and that the scent of individuals of different ages elicited chemosensory responses of different magnitudes. The scents from adult conspecifics elicited the quickest and highest chemosensory responses (i.e., short latency times and high tongue-flick rates), although we did not find differential responses to scent of males and females. The magnitude of the responses was lower to scent of sub adult individuals, and then even lower to scent of juvenile snakes, but in all cases the scent of snakes was discriminated from a blank control. We discuss the potential chemical mechanisms that may allow age recognition and its implications for social and sexual behavior of this snake species.

Muchas serpientes son capaces de usar su sistema quimiosensorial para detectar el olor de individuos coespecíficos, lo que es importante en muchos contextos sociales. La discriminación de la edad basada en señales químicas puede ser especialmente importante para asegurar el acceso a parejas potenciales que sean sexualmente maduras. En este estudio, usamos 24 individuos de una especie de boa (Boa constrictor) (12 individuos adultos y 12 inmaduros) que habían sido capturados en diferentes partes de Ecuador y eran mantenidos en cautividad el Vivarium de Quito. Usamos experimentos de protusiones linguales para examinar si esta serpiente es capaz de discriminar entre el olor de individuos maduros y no maduros. Los resultados mostraron que B. constrictor usa señales químicas para reconocer co-específicos y que el olor de individuos de distinta edad provoca respuestas quimiosensoriales de diferente magnitud. El olor de individuos adultos provocó las respuestas más rápidas y elevadas (esto es, tiempos de latencia más cortos y tasas más altas de protusiones linguales), aunque no encontramos diferencias en las respuestas a olores de machos y hembras. La magnitud de las respuestas fue más baja a olores de sub adultos, e incluso más baja a olor de juveniles, pero en todos los casos el olor de una serpiente era discriminado de un control no oloroso. Discutimos los posibles mecanismos químicos que pueden permitir esta discriminación de la edad y sus implicaciones para el comportamiento social y sexual de esta serpiente.