Some animal vocalizations are relatively simple in acoustic structure, but many are also very complex and can be energetically costly to produce. So, why produce them? Here we examine some data on frog and bird vocalizations that offer possible explanations.

In an attempt to ascertain how some species of song birds learn their songs, researchers have developed techniques to disrupt auditory input as well as output and assess the results on adult song.

An examination of the complexity of bird song, the syrinx—a structure that is primarily responsible for it, and how song develops from nestlings to adults.

How nonhuman animals use sounds within the human hearing range to refer to specific items, such as threats from potential predators as well as food items.

Many nonhuman species send and receive auditory signals outside the range of human hearing. Low-frequency infrasound and high-frequency ultrasounds play numerous roles, as discussed here.

Infrared & ultraviolet senses are used extensively by a wide variety of nonhuman organisms, even though these senses are outside the range of visible light to which humans are sensitive. Some examples shown here involve California Ground Squirrel tail wagging, avian mate choice, Jumping Spider courtship, and butterfly wingspots.

Bioluminescence is a form of visual communication involving pulses of light produced by specific organs in a variety of species, such as deep-sea fishes, jellyfishes, and fireflies.

Various aspects of how animals communicate visually, including the waggle dance of honey bees, how honeyguides help Boran people locate honey, asymmetrical tail-wagging of dogs that reflect different emotional states, and mockingbird recognition of threatening humans.

Locating the source of an animal vocalizing ranges from relatively easy to quite difficult, and it all depends on structure of the signal. Easy-to-localize sounds are used for specific purposes, and difficult-to-localize sounds are used for other purposes, as discussed in this screencast.

How nonhuman organisms deal with environmental noise to enable effective communication. Noise includes signal attenuation and signal degradation, and has effects on stimulus detection and stimulus recognition.