Study links blue-depleted lighting to lower stress in shelter cats

A Michigan State University study suggests that one of the simpler shelter-environment changes may also be one of the more useful: adjust the lights. In the peer-reviewed paper, published in iScience in June 2025, researchers followed 101 shelter cats during their first five days after intake and found urinary cortisol fell more under dim, blue-depleted overhead lighting than under standard bright lighting by day 5. The team also tracked behavior with daily stress scoring and PetPace smart collars, adding objective activity data to the shelter-medicine picture. (sciencedirect.com)

Why it matters: For veterinary professionals working in shelters, the finding is notable because lighting is a relatively low-cost environmental variable compared with staffing changes, housing redesign, or pharmacologic intervention. The study also adds nuance: time in shelter reduced stress markers across all groups, dim light alone increased hiding, and the strongest cortisol benefit appeared under dim, orange or blue-depleted light rather than standard lighting. That means lighting changes may be most useful as part of a broader feline stress-reduction plan that still includes hiding space, handling protocols, and close monitoring during the first several days after intake. (pmc.ncbi.nlm.nih.gov)

What to watch: Whether shelters test these lighting protocols in adoption rooms and longer stays, not just controlled intake housing, will determine how quickly the findings translate into day-to-day shelter practice. (pmc.ncbi.nlm.nih.gov)