"Much like the human version
… depression in animals spans the full spectrum of severity, from brief and shallow periods of low mood to long and intense stretches of depression. Animals also experience the same hormonal changes that depressed humans do, including higher secretion of steroid hormones and dampened immune system function. Perhaps most interestingly and indicatively, the body clocks of depressed animals — their circadian rhythms, which we already know are of tremendous importance to human well-being
— are so disrupted that they produce the same irregularities in body temperature and sleep-wake cycle seen in depressed humans."
Can pets be depressed?
The science behind what every pet-owner intuits. (via explore-blog