How do proximate causes differ from ultimate causes in animal behaviour?

In the study of animal behaviour, researchers differentiate between proximate and ultimate causes to provide a comprehensive understanding of why animals act as they do. This framework, originally clarified by the ethologist Nikolaas Tinbergen, distinguishes between the immediate mechanisms of a behaviour and its evolutionary significance.12

Proximate Causes

Proximate causes address the "how" of a behaviour—the immediate mechanisms that allow it to occur. These include:12
* Causation: The physiological, neural, and cognitive machinery, such as hormonal responses, sensory processing, and muscular activity, that triggers a specific action.132
* Ontogeny: The developmental processes, including the influence of genes and individual experience, that shape a behaviour as an animal matures.2

Ultimate Causes

Ultimate causes address the "why" of a behaviour from an evolutionary perspective. These include:12
* Function: The survival value of a behaviour and how it contributes to an individual's genetic success and reproduction.12
* Evolutionary History: The historical origins of a trait and the sequence of selective processes over geologic time that led to its current form.12

While proximate causes explain the internal and external factors directly underlying a behaviour, ultimate causes explain the selective pressures that have shaped that behaviour over generations.12