What do you associate with rabbits?
Sure, the hopping, the twitchy noses, the long ears. Rabbit’s feet are good luck (though, when detached, not especially for the rabbit). The whole, mystifying, carrot thing. And then…
Well, then there’s that other thing you don’t teach your kids about Flopsy and Lord Benjamin Bunny.
That thing about them being ferocious sex fiends. Their propensity to have sex at the twitch of a cottontail is legendary – and occasionally problematic, as Australia found when they became something akin to a plague in the wild.
But the prodigiousness of their breeding means people often ask whether rabbits go into heat like other mammals.
Believe it or not, that’s a more complicated question than you ever imagined.
First of all, we need to know what we mean by going “Into heat.”
Technically, it’s a period of time when the females of some species are more receptive to mating, immediately prior to ovulation.
What initially confuses some people is that they assume a period of being “in heat” must be followed by either conception, or by menstruation if an egg is not fertilized during the “in heat” period.
But here’s the thing. Many mammals don’t technically menstruate. Instead of shedding their endometrial lining if it’s not needed to host an embryo, many animals reabsorb the lining instead. Animals that do this are said not to have a menstrual cycle but an estrus cycle.
So, it’s wise to keep in mind that animals can go “into heat” without it resulting in either a fertilized egg or a menstrual discharge.
Dogs have an estrus cycle, rather than a menstrual cycle, but are one of the most famous animals to go “into heat.” Cats too – estrus, not menstrual, and famous for their noisy seeking out of mating partners during that period.
(Not for nothing, there’s quite a body of research that suggests that women frequently or occasionally feel more sexually aroused around the time of ovulation – usually around two weeks before their period.
Do not, do not, do not quote us as your intro-line on Tinder, we beg you for the future of the species. “So, hey, you in heat right now?” is a 100% copper-bottomed, gold-plated way to ensure you will never find out.)
The key thing to remember is that these mammals “in heat” are responding to hormonal signals sent out by their bodies, telling them to seek mates NOW because ovulation is imminent, and the best chance they have of successful procreation will be to have an awful lot of sex over the next species-or-breed-specific number of days. It’s like a biological version of Black Friday – get it now or it’s gone till next season…
Sexual receptivity immediately prior to ovulation are the words to hold in your head. Because they’re the words that let rabbits out of being “in heat” on a biological technicality.
What the hell, rabbits?
Rabbits have an estrus, rather than a menstrual, cycle. Now, in rabbits, what happens is that follicular development in the ovaries triggers the release of estrogen, making the female more receptive to sexual activity. The follicles grow and release estrogen over the course of about two weeks. If there’s been no pregnancy within that time, the follicles degenerate, and estrogen levels drop.
So, wait, that’s a season, right? That’s the rabbit’s heat cycle. Case closed.
Stick with us, Sparky, we’re not done yet.
Two weeks of luscious, estrogen-soaked sexual receptivity for Flopsy the rabbit, then her estrogen levels drop and she’s just not into you.
Mm-hmm. For four… days.
Then boom! The cycle starts again and Flopsy’s hanging round the entrance to your burrow making big eyes at you and twitching her nose in jusssst that right way again.
Roughly, if we were to class a female rabbit’s estrus cycle as being “in heat,” she’d be in heat for roughly 14 days, then just chilling, no Netflix for 4, and then back “in heat” again.
Mmmmore or less constantly, from about the age of four months.
This doesn’t make any difference to the life of poor Flopsy, but we’re not going to class it as being “in heat.”
We should, surely – the length of the cycle of heat/no heat should make no difference. It still IS a cycle of intensified sexual receptivity, right?
Yes, it absolutely is.
But this is where you need to go back and read the words in bold. The words we told you to keep in mind.
Being “in heat” is a period in which animals are more receptive to mating immediately prior to ovulation.
The rabbit’s “heat cycle” takes place whether or not they’re ovulating. In fact, they won’t ovulate in response to the hormone banquet of their ovarian follicles. They are what is known in nature as “induced ovulators.”
That means that while there’s undoubtedly what looks, sounds and, for those with attuned noses, smells like a period in which female rabbits are “in heat,” the disconnection from the ovulation process means it’s not a true “heat” period. It’s more a “ready when you are” period, which, added to its state of near constancy, explains a lot about why rabbits are such phenomenal breeders (up to 50 offspring per year, per rabbit, since you didn’t ask).
So, if they’re not induced to ovulate by their own hormones… what gets a rabbit egg moving?
Well, not to put too fine a point on it, mating will do the trick. If Lord Benjamin Bunny slips on the Barry White and makes like a jackhammer, Flopsy will ovulate within around ten hours. Her egg is kind of like the hostess who won’t attend her own party until she’s sure all the guests are there.
But other things can induce ovulation, too. Mechanical stimulation will get the egg moving. So will being mounted by another female (Go, sisters!) and so – which is the most disturbing thought if you scale it up to human experience – will simply being close to a male.
Can you imagine the subway?
The point being, ovulation can be induced by all kinds of things and is at least technically unrelated to the female’s sexual receptivity.
That means that no, rabbits don’t technically go “into heat”. It’s just that female rabbits are almost always in a state of sexual receptivity which would normally be described as being in heat.
Is that as near as makes no difference to being in heat? Probably, from Flopsy’s point of view.
But not within the definitions we as humans have for it.