RESUMEN
The ability of Norway rats to use binaural time- and intensity-difference cues to localize sound was investigated by determining their ability to localize pure tones from 500 Hz to 32 kHz. In addition, their ability to use the binaural time cues present in the envelope of a signal was determined by presenting them with a 1-kHz tone that was amplitude modulated at either 250 or 500 Hz. Although the animals were easily able to localize tones above 2 kHz, indicating that they could use the binaural intensity-difference cue, they were virtually unable to localize the lower-frequency stimuli, indicating that they could not use the binaural phase (time) cue. Although some animals showed a residual ability to localize low-frequency tones, control tests indicated that they were using the transient interaural intensity difference in the onset of a sound that exists after it reaches the near ear but before it reaches the far ear. Thus, in contrast to earlier studies, we conclude that the Norway rat is unable to use the ongoing time cues available in low-frequency tones to localize sound, raising the possibility that the rat may not use interaural time differences to localize sound.
Asunto(s)
Conducta Animal , Señales (Psicología) , Percepción de la Altura Tonal , Localización de Sonidos , Animales , Audiometría de Tonos Puros , Masculino , Ratas , Factores de TiempoRESUMEN
Affective states are thought to be expressed in the mammalian voice, but such investigations are most common in primates. Source and filter features of rumbles were analyzed from 6 adult female African elephants (Loxodonta africana) at Disney's Animal Kingdom. Rumbles produced during periods of minimal social interaction ("low affect") were compared to those produced during dominance interactions ("high affect"). Low-ranking females produced rumbles with increased and more variable fundamental frequencies, and increased durations and amplitudes during dominance interactions with superiors, compared to the low affect context. This acoustic response is consistent with the expression of affect in mammals and may signal submission to superiors. The 2 highest ranking females were codominant and competed for alpha status. They produced rumbles with decreased and less variable fundamental frequencies, increased durations and amplitudes, and a decrease in formant dispersion during dominance interactions with each other, compared to the low affect context. This response is not generally consistent with the expression of affect, but may signal large body size to competitors. These results suggest that affect can be expressed in the voiced sounds of elephants.
Asunto(s)
Afecto/fisiología , Comunicación Animal , Vocalización Animal/fisiología , Animales , Tamaño Corporal/fisiología , Conducta Competitiva/fisiología , Dominación-Subordinación , Elefantes/fisiología , Femenino , Jerarquia Social , Conducta Social , Espectrografía del SonidoRESUMEN
The movements of elephants in captivity have been an issue of concern for animal welfare activists and zoological professionals alike in recent years. In order to fully understand how movement rates reflect animal welfare, we must first determine the exact distances these animals move in the captive environment. We outfitted seven adult female African elephants (Loxodonta africana) at Disney's Animal Kingdom with collar-mounted global positioning recording systems to document their movement rates while housed in outdoor guest viewing habitats. Further, we conducted preliminary analyses to address potential factors impacting movement rates including body size, temperature, enclosure size, and social grouping complexity. We found that our elephants moved at an average rate of 0.409+/-0.007 km/hr during the 9-hr data collection periods. This rate translates to an average of 3.68 km traveled during the observation periods, at a rate comparable to that observed in the wild. Although movement rate did not have a significant relationship with an individual's body size in this herd, the movements of four females demonstrated a significant positive correlation with temperature. Further, females in our largest social group demonstrated a significant increase in movement rates when residing in larger enclosures. We also present preliminary evidence suggesting that increased social group complexity, including the presence of infants in the herd, may be associated with increased walking rates, whereas factors such as reproductive and social status may constrain movements.