How noisy males control the GNU cycle | At the Smithsonian

The crossing of the Grumeti Game Reserve, Tanzania, on an interception trail of a migrating wildebeest herd is not what most people imagine when they are in the wild. they think about scholarly scientific research. But for the authors of a recently published article on wildebeest reproductive indices, four or four escapades worthy of Indiana Jones were their field work.

This initial excitement took place 15 years ago. Allison Moss Clay of the Smithsonian Conservation Biology Institute, co-lead author on paper, was at the time a starry-eyed doctoral student, introduced to the Serengeti unexpectedly thanks to an idea from eminent biologist Richard Estes.

Estes, who has been dubbed the "wildebeest guru" for his knowledge of wildebeest behavior, had the intuition that frantic mating periods of animals depended on a female physiological response. to the quick vocalizations of the males, and invited his colleague Steven Monfort to Amenez Clay on a trip to southeastern Africa to study the situation closely.

With permission from the Tanzania Wildlife Research Institute and the help of a professional serengeti veteran with a tranquilizer rifle, Clay, Estes and other researchers followed a group of transient wildebeest through sweeping plains, dropping 15 females with darts containing a knockout concoction of etorphine and xylazine. Estes helped the vet identify the gravid targets, specimens ideal for the experiment, as they were guaranteed to be fertile. "We were launching these pregnant women, migrating, to the back of a Land Rover," recalls Clay. "It was pretty crazy."

This week, the fruits of the team's ambitious hoax-giflage expedition appeared in the journal Science Reports . The paper confirmed Estes' suspicion that the collective drone mating calls for wildebeest bulls had a significant effect on the ovulation of females. In fact, the link between the audio coming from the rutting males and the timeliness and synchronicity of the menstrual cycles of the beasts was so strong that the researchers tentatively concluded that it was the primary mechanism by which wildebeest kept in the season of loves. [19659003] Exhilarating off-road hunting has been the cornerstone of several months of grueling manual labor. "There was no research camp when I went there," Clay says. "No cell phone, no radio, it was literally in the middle of nowhere, no electricity, nothing." In addition to providing shelter and rudimentary infrastructure – a single propane generator was what the group was installing to power its energy – Clay and his colleagues had to erect a paddock enclosing tens of grassy acres for captive wildebeests.

Once the wildebeest were secured and their babies were born, the experiment began in earnest. After dividing the 15 females into three groups of five, the researchers exposed group 1 (the control) to no male stimulus, group 2 to masculine vocalizations characteristic of the mating season, and group 3 to male vocalizations as well as # 39, a test of flesh and blood. eligible elephant wildebeest. What they found was a striking assumption of the Estes hypothesis: the call to mating male wildebeest concretely affected the female's menstrual cycle, whether the bull was or not physically present, accelerating ovulation by a factor of three. In the wild, this effect would ensure mating in 80% of females within three weeks.

Why the rush? It has to do with survival, Clay said. Wildebeests on the Serengeti do not have the luxury of hiding their little ones like forest roe deers under the sun and short grass, large cattle and their offspring are constantly exposed. If wildebeest reproduce throughout the calendar year, their scattered youngsters would be attracted to predators every turn. The adaptive solution of Gnus is to have their young people all at once, to overwhelm and disorient potential abusers.

"They go to the opposite approach," says Clay, "and have just so much [babies] at a time that it submerges the predators." The flock is thus safe, and it becomes physically impossible for predators to escape with more than a few young wildebeest. "If you are a female wildebeest and you have a calf outside this woodpecker," she adds, "it comes off like a sore thumb, and risks much more predation. "

For the successful bombardment strategy of babies, wildebeest must adhere to a tight breeding schedule." So that they can calve at the same time, Clay said, "They have to get pregnant at the same time. And to get pregnant at the same time, they must all produce an egg at the same time. It's here that the acceleration and timing of the menstrual cycle come into play. And the paper just published by Clay shows that these essential effects are brought about by the chorus characteristic of the hees and haws of wildebeest males. during the mating season

How do wildebeest know exactly when to trigger their mating cries is an enigma in itself, and the main author of Clay Justin Calabrese, also with the Smithsonian Conservation Biology Institute, is eager to conduct a thorough statistical analysis of the relevant literature to shed light on this side of the equation in the coming years.

Ranking among the most abundant critters on the Serengeti, western wildebeest to those studied by Clay and Company are considered a "key species". They play a vital role in maintaining their ecosystem and the associated food web. In summary, no wildebeest is bad news – and wildebeest populations are in decline.

Clay hopes that subsequent research on a larger scale will help determine whether the effectiveness of male mating calls will decrease dramatically as populations increase. "If this calving synchrony depends on density," says Clay, "and as the density decreases, will it cause a precipitous loss of population?"

Studies built on the basis of it could ultimately pave the way for valuable wildebeest conservation efforts, which stem the tide of habitat destruction and hunting by humans. "If the population decreases due to habitat loss or poaching," Clay adds, "and on top of that, the dwindling population will affect the effectiveness of their anti-predation strategy for their young people, which could seriously affect the population. "

I like this article?
REGISTER to our newsletter