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Why do many mammals have skin glands that produce odors?

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A pangolin walks through grass with a blue circle around it and the word endangered written in white across the image. — Integument The pangolin is the only mammal in the world covered in scales.

Many mammals possess specialized skin glands that produce odors primarily to facilitate sexual or social communication. These glands, which can be found across various areas of the body, serve several critical biological functions:1

Territorial Marking: Many species use glandular secretions to advertise and defend their territories. By depositing complex chemical mixtures on objects like grass or twigs, animals can signal their presence to others, distinguish between residents and intruders, and even judge the age of a scent mark based on how it has changed over time.23
Reproductive Coordination: Odors act as pheromones that influence both behavior and physiology. These chemical signals can synchronize sexual maturation, trigger or delay ovulation, and assist in individual recognition between mates.45
Social Signaling: Beyond reproduction, scent is used to threaten rivals or convey information during social interactions. In some cases, such as when alarmed, animals may leave scent marks that serve as danger signals to others.3

These glands are highly diverse in structure—including sebaceous, tubular, and apocrine types—reflecting the complex ways mammals utilize chemical cues to navigate their environments and social structures.13