The monthslong annual migration of Tibetan antelopes began recently with about 100,000 mothers-to-be expected to get involved this year, experts revealed on Wednesday.

"About 100,000 female antelopes are expected to join in the long breeding journey, about one-third of the species' current total population," said Wu Xiaomin, a Tibetan antelope expert from Shaanxi Institute of Zoology, which is also the Northwest Institute of Endangered Zoological Species.

On Thursday, seven experienced rangers sent by the Hoh Xil management office at the Three-River-Source National Park will also head to the antelopes' "delivery room"－Zonag Lake－h(huán)elping to take care of mother antelopes and the newborns, according to Karma Tseten, head of the office.

"Some of them had nearly 20 years' experience in wild animal protection and are able to give necessary medical aid to the antelopes," he said.

"Moreover, they will also record the antelopes' daily activities and the number of newborns to build a database for further studies."

About five months after the mating season in winter, pregnant antelopes, mostly from the Three-River-Source National Park in Qinghai, Changtang National Nature Reserve in Tibet and Altun Mountains in Xinjiang Uygur autonomous region, will travel hundreds of kilometers for one particular destination－Zonag Lake in Hoh Xil.

After giving birth, they will then migrate back to their habitats with their offspring in August.

"The journey is one of the world's most magnificent wild animal migrations, and the driving force behind this decadeslong habit is still a mystery," Wu said.

This year's first migrating spearhead was witnessed on April 30 at the Three-River-Source National Park, according to Karma.

The park has two sections along the Qinghai-Tibet highway, marked at 2,998 km and 3,002 km, that had witnessed the greatest number of migrating antelopes.

Karma said this year's first migration group consisting of 43 pregnant antelopes was found on the 3,002 km section, where rangers have seen more than 600 antelopes cross as of Tuesday.

To guarantee their safety, Karma said the number of rangers in the station covering the two sections doubled from last year to about 10 people.

The Tibetan antelope is timid by nature. It can run in bursts up to 80 kilometers per hour.

In 2008, it was listed as an endangered species on the Red List of Threatened Species by the International Union for the Conservation of Nature and Natural Resources.

Thanks to China's protection efforts, including combating illegal hunting, improving the living environment as well as increasing investment in the protection work, the species' population grew to nearly 300,000 last year and the IUCN lowered it from "endangered" status to "threatened" in 2016.

Data collected on the 2,998 km and 3,002 km sections along the Qinghai-Tibet highway last year showed that 3,646 pregnant antelopes went across in May, and a total of 4,860 antelopes returned.

Since 2017, the BeiDou Navigation Satellite System has helped scientists study the species.

Wu said nine Tibetan antelopes in Qinghai and 15 in Tibet now have high-tech collars that monitor their daily movements.

The e-collars cost about 100,000 yuan ($14,100) each.