HEARING IN THE BLACKFOOTED PENGUIN, Spheniscus demersus , AS REPRESENTED BY THE COCHLEAR POTENTIALS

Abstract

Abstract.-A study of the hearing of the penguin Sphenikcus demersus, in terms of the cochlear potentials, showed sensitivity over a range at least of 100 to 15,000 Hz, with the best sensitivity in the region of 600 to 4000 Hz. The form of the sensitivity function is consistent with the vocalizations of these animals. In general, this species of penguin shows good agreement with other birds in both the form and range of auditory sensitivity.The auditory capabilities of one species of penguin, Spheniscus demermus, commonly called the Blackfooted or Jackass Penguin, were investigated by means of the cochlear potentials. This is one of the smaller penguin species, breeding on islands off the western coast of South Africa. Three animals were used for the observations.The animals were anesthetized with ethyl carbamate, administered intraperitoneally in a 20 per cent solution at a dosage of 0.01 cc per gram of body weight. During the experiments the animal rested on a heating blanket, and a body temperature of 380C was maintained by means of a temperature probe in the cloaca that led to a regulating instrument.The middle ear cavity was exposed by a lateral approach, as indicated in Figure 1. The right side of the head is shown, with the region of the skin incision indicated. The removal of skin and muscle tissue in this region exposed the poster-

A comparison of auditory brainstem responses across diving bird species

“…Of these 50 species, only two are considered aquatic– the black-footed penguin ( Spheniscus demersus; Wever et al 1969), and the mallard duck ( Anas platyrhynchos; Trainer 1946). These two species are from different taxonomic families, and vary in the habitat they occupy (penguins are exclusively marine and mallards are found throughout coastal and freshwater waterways), their aquatic lifestyle (penguins are adapted for swimming underwater and mallards live at the water’s surface), their social structure (penguins nest in dense colonies with males and females both incubating the eggs, while mallard nests are scattered throughout a range of environments and only females care for young), and foraging habits (penguins pursue live fish, while mallards eat grasses, seeds, and invertebrates).…”

“…Only one species of diving bird, the black-footed penguin ( Spheniscus demersus ), has been studied in respect to auditory capabilities (Wever et al 1969). We therefore measured in-air auditory threshold in ten species of diving birds, using the auditory brainstem response (ABR).…”

Gentoo penguins (Pygoscelis papua) react to underwater sounds

“…The stimulus contained frequencies between 0.2 and 6 kHz. This encompasses the known hearing range of penguins in air [15] and makes it likely that the frequency range of underwater hearing is similar. Judging by the gentoo penguins' fast swimming and curious behaviour, the extension of the pause between playback trials, as well as the restriction on the maximum number of playbacks per day, seemed to have been adequate to avoid any habituation to the signals.…”

“…Much less is known about underwater hearing in marine birds. In air, all avian species, including marine birds such as penguins, have excellent hearing abilities [6,[15][16][17]. They use airborne sounds for behaviours such as mating displays, courtship, predator warning and to establish the relation between mother and chicks [18].…”

In-air hearing of a diving duck: A comparison of psychoacoustic and auditory brainstem response thresholds

“…Approximately half of all birds for which there are hearing data are from the order Passeriformes (perching birds-includes the songbirds), as well as 13 species of owl and several other non-passerine, non-aquatic birds (Dooling et al, 2000;Dooling, 2002). There are few data on aquatic birds, with only the blackfooted penguin (Spheniscus demersus, Wever et al, 1969) and the mallard duck (Anas platyrhynchos, Trainer, 1946) represented in the literature. Adaptations for living in an aquatic environment may be related to auditory sensitivity.…”