Pandas, as a species, seem absolutely resolute in their desire not to breed, regardless of how much panda porn we seem to show them. Just to further drive this point home comes new research — not only do females pandas have a reproductive window, but the males do too.
The reproductive cycle of female pandas has been relatively well studied, and we know that they only go into heat once a year, for a period of around 24-72 hours, which helps explain the creatures' abysmal breeding rate. But for the first time, a multi-year large study has examined male pandas' fertility too, which runs on its own cycle.
The male panda's sexual seasonality is unsurprisingly based around meeting that extremely short window that the females are in estrus, which can occur at any point between February and May. The males have a three-phase cycle: pre-breeding, breeding, and non-breeding, with that central phase located when the females are most likely to be up for it.
How do you measure panda sex drive? Testes size, fecal androgen excretion, ejaculated sperm density, and frequency of reproductive behaviors, it turns out. These ramp up in the months prior to breeding season, and, as the paper points out:
Testes volume and sperm concentration were maximal from Mar 22 through Apr 15, a period coinciding with maximal female breeding activity.
So rather than the razor thin window of breeding that the females have, the males have evolved a longer period where they're at the most fertile, so that they're ready to go when the lady-bears are. Since these two cycles line up pretty well, why does this information matter? Because now scientists know when they can gather the highest quality sperm for artificial insemination, as these darn animals refuse to breed on their own.
Image credit: Zhang Zhihe, Chengdu Research Center for Panda Breeding