Four research articles on baby rabbits and how they keep warm.

Private Heat for Public Warmth: How Huddling Shapes Individual Thermogenic Responses of Rabbit Pups

By providing public warmth with minimal individual costs at a stage of life when pups are the most vulnerable, huddling buffers cold challenges and ensures a constant allocation of energy to growth by reducing BAT activation.

ScienceShot: Baby Rabbits Band Together

Such cooperation, like investors making a joint business venture, comes at a small private cost, as generating heat uses body fat that in turn uses up oxygen, and using too much oxygen can stunt a rabbit’s growth.

Why do heavy littermates grow better than lighter ones? A study in wild and domestic European rabbits.

Our study indicates that at least two main mechanisms account for this relationship in our study species: heavier pups had a higher milk intake and also showed a more efficient conversion of milk into body mass. Furthermore, our study suggests that the better milk conversion by heavy pups was driven by three synergistic mechanisms: heavier pups had comparatively more huddling partners in the nest, they did not need to perform large amounts of proactive behavior in order to reach and remain in a central position within the litter huddle, and they could maintain a comparatively higher body temperature most probably due to their more favorable surface area to volume ratio.

Brown adipose tissue and the response of new-born rabbits to cold. I was unable to copy and paste a quote from the article. Scientific language used, has pics to show where the brown adipose tissue is. I found it interesting to learn that cold baby rabbits can increase their oxygen intake.