Sex hormones are not the only hormones that are affected by the increase in amount of daylight that occurs in spring. Plus, buns and humans, both male and female, have some testosterone production in their adrenal glands, and this production persists or gets exacerbated by castration. An increase in amount of daylight causes a decrease in melatonin (“sleep hormone”), and an increase in sex hormones. Rabbit behaviour is highly hormone-dependant. Elevated testosterone is known to cause exaggerated aggression in some individuals, both humans and animals.

Ambient heat also affects hormones. This makes total sense of course, wild male rabbits wont produce sperm during the coldest winter months, because it’d be counter-productive for girl buns to be pregnant and have kits when food is really scarce (girl rabbits are induced ovulators, meaning they ovulate in response to mating). In house buns this doesnt really matter though, since indoors temps stay mostly the same all year round.

Could you arrange some sort of darker curtains in the bun area? That could enable you to give them sth similar to 12 hours of “night” and 12 hours of “day”. My buns currently go totally bonkers every morning at 4 am. They dont fight but they gallop around like a herd of genuinly annoying wildebeest. I banish them to the (predator-proof) veranda around 4.15, but if I didnt have that option, I’d try dark curtains to try and mimick a longer night.