Lorenz, Konrad Zacharias (1903-1989), an Austrian zoologist, was a founder of ethology, the study of animal behavior. He and two other ethologists, Karl von Frisch of Austria and Nikolaas Tinbergen, born in the Netherlands, received the 1973 Nobel Prize in physiology or medicine for their work on animal behavior. Lorenz studied animals in their natural environments and concluded that instinct plays a major role in animal behavior. This view challenged behavioral animal psychology, which defined all behavior as learned.

Konrad Lorenz was the younger son of Adolf Lorenz, a distinguished orthopedic surgeon, and Emma Lecher Lorenz, a physician who worked with her husband. Lorenz grew up in Vienna and at the family's summer estate in Altenberg, a village onthe Danube River. As a young child, he became fascinated with animals.

Lorenz attended one of Vienna's best secondary schools. By the time he graduated, he knew that he wanted to study animals. However, to please his father, Lorenz studied medicine at the Anatomical Institute of the University of Vienna. After obtaining his degree in 1928, he stayed on at the institute as an assistant. He also began studying zoology, in which he received a Ph.D. degree from the University of Vienna in 1933. One of Lorenz's first professional writings, based on his detailed observations of a pet jackdaw, a small, clever crow, was published as an article in an ornithological journal in 1927.

From about 1927 to 1935, Lorenz worked in the anatomy department of the University of Vienna. From 1935 to 1938, he made studies of geese and jackdaws. Many of his most significant scientific papers were based on this work.

The best-known concept Lorenz developed during his early career is that of imprinting, the process by which an animal follows an object, normally its biological mother. He observed how a newly hatched duckling follows the sound of its mother's quacking and thereby becomes permanently imprinted on her. He observed that if he imitated a mother duck quacking to a brood of newly hatched ducks, the ducklings would follow him.

Lorenz also developed an innate releasing mechanism theory. He believed that an animal's inherited behavior pattern will remain dormant until a stimulating event triggers it. Lorenz called the triggering event the “releaser” and called the inherited behavior that responds to it the “innate releasing mechanism.” For example, the strong brooding instinct of a hen is released by the sound of peeping chicks.

In 1937, Lorenz was appointed lecturer of comparative anatomy and animal psychology at the University of Vienna. Three years later, he left Austria to become professor of psychology at the University of Konigsberg in East Prussia (now Kaliningrad in the Soviet Union). World War II (1939-1945) soon interrupted his academic career. He joined the German army and served on the eastern front as a doctor. In June 1944, Russian soldiers took him prisoner, and he spent almost four years in prison camps.

He resumed his studies at Altenberg after the war with a small stipend from the Max Planck Society for the Advancement of Science. His 1949 book, published in English as King Solomon's Ring: New Light on Animal Ways (1952) became an international success and introduced concepts of ethology to many readers. He also wrote the popular Man Meets Dog (1955), in which he explored the relationship between humans and pets. In his controversial book On Aggression (German, 1963; English, 19661, he defined aggression as behavior directed toward members of one's own species and argued that aggression is innate in humans as well as animals.

In 1951, Lorenz became head of a research station of the Max Planck Institute for Marine Biology in what is now Westphalia, Germany. In the mid-1950's, he and two other scientists established the Institute for Behavioral Physiology in Seewiesen, Bavaria, near Munich. Lorenz became its sole director after 1961. In 1973 Lorenz became director of the Institute of Comparative Ethology of the Austrian Academy of Sciences in 1973.