How does an animal's (specifically dogs and cats) body "know" to shed fur in the spring and retain fur in the autumn?

Google just tells me that it happens, not the biological process of turning off the follicles and then turning them back on.


1 Answer 1


Their seasonal (colour) moulting is controlled by pituitary hormones, including prolactin, melatonin and alpha-melanocyte stimulating hormone (α-MSH), together with glucocorticoids, gonadal steroids and thyroid hormones (Zimova et al., 2018).

From the link:

We found that across species, ... photoperiod is the main driver of the moult phenology

In other words, daylight getting longer is a signal of spring/summer; daylight getting shorter is a signal of fall/winter.

  • $\begingroup$ Thanks for the editing from Bryan and Ron. I'm not experienced in this field and I learned from your contribution :-) $\endgroup$
    – X Zhang
    Jun 22, 2022 at 3:57
  • $\begingroup$ @BryanKrause but my indoor cats shed in the summer. $\endgroup$
    – RonJohn
    Jun 22, 2022 at 4:58
  • $\begingroup$ @RonJohn Do your indoor cats see daylight? $\endgroup$
    – Bryan Krause
    Jun 22, 2022 at 8:05
  • $\begingroup$ @BryanKrause much less than they see indoor light at night, or a dark room during the day. $\endgroup$
    – RonJohn
    Jun 22, 2022 at 18:10

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