It is the equivalent of saying “I want you now”. When giant pandas are in the mood for sex, they bleat at each other.
That’s the finding of a joint Chinese-American study which could help breeding managers find promising sex partners among the endangered bamboo-eating mammals. At the same time, it could indicate which combinations of panda bears would fizzle at sex.
“Our findings show that vocal exchanges are crucial for signalling an intention to mate in giant pandas,” said Benjamin Charlton of the San Diego (California) Zoo’s Institute for Conservation Research. “And [the discovery] could provide a valuable tool for breeding programmes, helping conservation managers to assess the likelihood of breeding success.”
Charlton co-led the study with Zhang Hemin of the China Research and Conservation Centre for the Giant Panda in the southwestern Chinese province of Sichuan.
The results were published last month in the London-based online journal Royal Society Open Science.
The researchers recorded 2,566 sounds produced by 23 adult pandas at two conservation centres in Sichuan. The recordings were scrutinised and divided into bleats, chirps, moans, barks and roars.
The researchers found that if the pandas bleated at each other – making wavering calls like sheep – they were more likely to have intercourse than those that did not emit the sound.
Another finding was that when the female pandas let out with a high-pitched chirp, it generally suggested sex was on the horizon. By contrast, roars and barks usually were a way of saying “this courtship is over”.
Researchers also found that while chirping is rare among male giant pandas, both sexes produce bleats, barks, moans, roars, growls and squeals when they interact with other members of the species. When pandas are alone, they tend to make sounds that appear like honks.
“Although the function of honks is unknown, it is generally assumed that barks, growls and roars are aggressive calls produced during agonistic encounters,” Zhang said. “Squeals are produced by subordinate individuals during or after a fight.”
Zhang said the pandas relied heavily on effective communication “not only to locate opposite-sexed individuals for mating purposes, but also to overcome their natural avoidance and aggressive tendencies”.
Living in the remote, mountainous regions of central and southwestern China, the pandas are solitary by nature and typically avoid other each other outside the annual breeding season, which starts in February and ends in May, according to the study.
The giant pandas involved in this study were housed at the China Research and Conservation Centre for the Giant Panda, at Bifengxia near Yaan, Sichuan, and Shenshuping in Gengda, Sichuan. Aged from 6 to 18 years, all the animals were sexually mature and had mating experience before the study.
The pandas are endangered because of habitat loss through logging, human encroachment, road construction and agriculture. But trying to revive the species by having them reproduce in captivity can be challenging.
Giant pandas reach sexual maturity at around age five. Females can mate with any of several different competing male suitors, but any of these males can seek sex with different females who are in heat, according to the study.
Female pandas typically live up to 20 years but can survive as long as 30 years in captivity. On average, each female panda gives birth to one cub every two years, according to WWF, a global conservation body.
Although the species was taken off the “endangered list” by the International Union for Conservation of Nature, only 1,864 giant pandas remained alive in the wild, WWF said, citing statistics from the latest census in 2014.
The international union classified pandas as “vulnerable” instead of “endangered” in 2014, citing China’s conservation efforts to expand the population up from fewer than 1,000 in the 1980s.