鬣 is rare and literary - you'll see it in classical poetry, zoology terms (鬣狗 = hyena, 鬣蜥 = iguana), and high-register prose. In everyday speech, the more common word for an animal's mane is 鬃 or just 毛.
memory
The character has 髟 (long hair) on top - the same radical you see in 髮 (hair) and 鬓 (temples). Whenever you spot 髟, expect a hair-related meaning.
Top long-hair radical (Kangxi #190) - 长 (long) over 彡 (streaks), picturing flowing tresses cascading down. It indexes 鬣 in the hair family: 髮 hair, 髯 whiskers, 鬃 horse-mane. The radical anchors the meaning as hair.
phonetic
巤liè
mane; bristles (phonetic)
Bottom 巤 is itself an ancient graph of an animal head with hair bristling outward, supplying the sound liè directly. The same phonetic powers 蜡 wax, 猎 hunt, 腊 cured-meat. It is the original 'mane' graph; the hair radical was added later as a clarifying semantic marker.
