How does e.g rabbits change their fur? And how does it trigger? Like how do they know when to change or do they?
In: Biology
They shed their old fur and grow new fur of a different color. Obviously not all at once like a lizard shedding its skin, but over time, hairs naturally fall out and the replacement hairs come in with a different color.
This change is triggered by hormonal changes, usually in response to a particular set of environmental changes. Temperature, food quantities, light exposure, etc. can signal the difference between summer and winter, and can trigger the change within the animal. (We humans don’t change color, but we have similar triggers; for example, specific times and locations can make us feel hungry and bright lights can keep us awake since both sleep and hunger are regulated by hormones.)
Hair normally grows in a cycle. In the first stage the hair from a previous cycle falls out. Next the follicle enters an active growth phase for a certain amount of time. The follicle then enters a resting phase where base of the hair thickens and then growth stops. In most cases the follicle spends the majority of time in this phase. Finally, the old hair is shed and the cycle repeats.
The time spent in the active phase determines the length of the hair.
At each stage, a certain set of specific chemical and genetic signals need to occur before the hair proceeds to the next stage. Exactly how this occurs and which signalling factors are involved isn’t well understood. Epinephrine/adrenaline appears to play a role.
Latest Answers