A new paper from our group presents the seasonal weight changes that laboratory ferrets undergo when exposed to regulated light changes.
In contrast to other laboratory species like mice, ferrets have an annual reproductive cycle in which they come into season during the spring and would normally mate and have kits in the summer. With this annual cycle come pronounced physical changes in coat color and thickness, as well as body weight, which we describe in the paper.
Importantly, the animals in our laboratory live in a regulated environment in which temperature, humidity and food availability are controlled and thus vary much less than the natural world. While this makes for a much nicer life for our animals, we still want them to follow a normal annual cycle. We therefore provide physical cues about the time of year through lighting - changing when their day starts and ends. In summer, lights come on early in the morning (6 am) and go out late in the evening (8 pm), while in winter, evenings end earlier (6 pm) and mornings start later (8 am). Transitions in spring and autumn are managed by weekly shifts in timing of one hour.
We show that these changes in light timing are associated with changes in body weight that mirror the natural variation expected with annual reproductive cycles. A ferret’s body weight can change substantially, by up to 30% - that’s like a human going from 70 kg (154 lbs) at Christmas (in the northern hemisphere) to 49 kg (108 lbs) by the summer!
Understanding these variations is important for research because it helps us determine whether an animal is losing weight because of a health issue, or simply because of the time of year. For example, losing 50 grams in the middle of January or July mean very different things. By reporting our data on weights, collected over many years, we hope to provide insight into these changes so that vets and researchers looking at an animal’s health have the appropriate information to make good decisions.
You can find the paper here:
Jones EJ, Poole KC, Sollini J, Town SM, Bizley JK (2020) Seasonal weight changes in laboratory ferrets. PLoS ONE 15(8): e0232733. https://doi.org/10.1371/journal.pone.0232733