Heat Cycles

Yes, just like real animals, Hewan have heat cycles. It's a natural thing, nobody can help it. Its usually very intense, the smaller the hewan breed, the more intense the 'urge'. Heat cycles start usually at around 13 for most Hewan, though it could be anywhere from 11 to 15.

Symptoms are listed below (All of which may vary, but these are some of the most common)

Symptoms of Heat (Female)
Anxiety

Possessiveness (Not to be confused with territorial, which is about everything, while possessiveness usually refers to their mate.)

Panting

Jumpyness

Symptoms of Heat (Male)
Aggression

Territorial

Constant erection

Twitching

Length and Intensity
If the length of a cycle is long, it's usually very un-intense and bearable. If it's short, like say a day like rabbits have, it's so uncontrollable they can't handle it and spend their day... You know. The longest heat cycle is a week, and the shortest is a day.

Random Facts
Aquatic Hewan lack heat cycles. It is unknown why, but they don't,