A system for observing animals, including at least one mobile identification unit configured to be worn by an animal, wherein the identification unit at least includes a memory, an on/off-switchable first-type transmitter unit for transmitting a radio wave for transmitting data, a first-type receiver unit, and a control circuit connected with the memory, the first-type receiver unit and the first-type transmitter unit, wherein the first-type receiver unit includes a resonant circuit which responds when it is introduced into an electromagnetic interrogation field, wherein the identification unit is configured such that the first-type transmitter unit can be activated for transmitting data when the first-type receiver unit responds when it is introduced into the interrogation field, wherein the system further includes at least one second-type receiver unit for receiving the radio wave which is transmitted with the first-type transmitter unit, wherein the system further includes at least one reader unit for generating the interrogation field and for detecting a response of the first-type receiver unit when it is located in the interrogation field, wherein the reader unit is configured to modulate the interrogation field with a transmission code, wherein the identification unit is configured for, in response to the reception of the transmission code with the aid of the first-type receiver unit, transmitting the radio wave with the first-type transmitter unit with a response code related to the received transmission code, for receiving of the response code with the second-type receiver unit.
