Ecology on‐exhibit: careers in zoos and aquariums

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Antiphonal exchanges in African elephants (Loxodonta africana): collective response to a shared stimulus, social facilitation, or true communicative event?

Female African elephants are thought to exchange \u27rumble\u27 vocalizations, but such temporally associated calls may not constitute communicative events. Affiliated females are more likely to engage in antiphonal calling, but affiliation is defined according to time spent in proximity. Affiliated partners may vocalize in sequence simply because their proximity causes them to collectively respond to shared external stimuli or due to a social facilitation effect. We used bi-variate and partial correlation analyses to test for the independent effects of the strength of the social relationship and distance between vocal partners on the likelihood of a vocal response. Female African elephants at Disney\u27s Animal Kingdom were video-taped and outfitted with audio-recording collars that allowed for the individual identification of low-frequency rumbles. Affiliation had a strong influence on response likelihood, even after controlling for the effects of the distance between vocalizing partners. Further, the distance between vocalizing partners did not correlate with response likelihood, and factoring out the effects of affiliation did not significantly alter this result. These results suggest that rumble exchanges are communicative events that reflect social bonds, not simply artifacts of increased proximity and, therefore, provide support for functional hypotheses concerning rumble exchanges in wild African elephants

Infant African Elephant Rumble Vocalizations Vary Accourding to Social Interactions with Adult Females

Research on African elephant (Loxodonta africana) vocal communication has increased in recent years, yet there has been very little data collected on the vocal production of infant African elephants. Vocalizations were recorded from a group of five adult female African elephants and 3 dependent offspring (1 male and 2 female) at Disney\u27s Animal Kingdom, Florida, U.S.A., using custom-designed audio-recording collars worn by the adult females. We measured both source and filter features of infant ‘rumble’ vocalizations made during affiliative social interactions and after cessation of nursing from adult females. Rumble vocalizations produced in the ‘nurse cessation’ context exhibited an upward shift in formant frequency locations, compared to rumbles produced during the ‘affiliation’ context. Additionally, call duration increased and fundamental frequencies decreased after nurse cessations for the male, but both females showed the opposite acoustic response. When infant rumbles accompanied nurse cessations, nursing was more likely to resume within 30 seconds compared to nurse cessations without vocalizations. These results suggest that infant rumbles associated with cessation of nursing reflect the motivational state of infants and may influence maternal responsiveness

The Expression of Affect in African Elephant (Loxodonta africana) Rumble Vocalizations

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

Rumble vocalizations mediate interpartner distance in African elephants, Loxodonta africana

The ability to utilize contact calls to facilitate reunions with social partners has been documented in a number of species showing a fission/fusion social organization. Field observations and playback experiments suggest that African elephants use low-frequency rumble vocalizations to reunite with their herd members following periods of fission. Using a digital audio and GPS recording collar system, we documented the production of rumbles and subsequent movements of five adult female African elephants at Disney\u27s Animal Kingdom, Bay Lake, Florida, U.S.A. This recording system allowed us to identify the producer of each rumble and to document the effect of rumbles on the movements of herd members relative to the caller. Our findings provide the first empirical evidence that spontaneously produced elephant rumble vocalizations function in part to mediate the spatial relationships of group members. Overall, the production of rumbles resulted in a net decrease in distance between the caller and her social partners. This approach behaviour was enhanced if the partner was highly affiliated with the caller, if the partner replied with a rumble of her own, and if the pair was initially far apart (≥61 m). Rumble production was likely to result in avoidance behaviour only when there was no rumble reply by the partner and the dyad was close together prior to the initial call. These results suggest that a general function of elephant rumbles is to promote spatial cohesion among separated group members, but they may also mediate a variety of other close-distance social interactions

Identifying Parentage Using Molecular Markers: Improving Accuracy Of Studbook Records For A Captive Flock Of Marabou Storks (Leptoptilus Crumeniferus)

Extra-pair copulations (EPCs) leading to extra-pair fertilization (EPF) are common in avian mating systems, despite the prevalence of observed social monogamy in many species. Colonially breeding birds are interesting species to investigate the prevalence of EPCs and EPF because they show nesting habits including close proximity of nest sites and sexual partners, which are proposed to promote alternative reproductive tactics. Endemic to Africa, the colonial marabou stork (Leptoptilos crumeniferus) is one of the most commonly held avian species in North American zoos. The aims of this study were to use genetic information to verify parentage in a population of marabou stork housed at Disney\u27s Animal Kingdom® based on five microsatellite loci and to investigate reproductive behavior. We compared genetic analyses of parents and offspring to studbook data collected through behavioral observations of parental behavior at the nest. Using genetic analyses to reconstruct the pedigree of the marabou stork flock using the program COLONY led to improvement of studbook records by determining parentage of an individual that had previously unknown parentage, and identified one individual that had a sire that differed genetically from studbook records. An important contribution of our analyses was the identification and verification of the most likely parents for offspring hatched in this colony and improving incorrect or undocumented parentage in the studbook. Additionally, the colonial nature of this species makes it difficult to observe and understand reproductive behavior. Gaining better understanding of the mating system of a species is essential for successful breeding and captive management. © 2013 Wiley Periodicals, Inc