Wednesday, December 1

Gazelles Mhorr: The rescue to the limit of the lady of the Sahara | Science


A young gazelle dama (Mhorr), with its mother, at the CSIC facilities in Almería in December 2019.
A young gazelle dama (Mhorr), with its mother, at the CSIC facilities in Almería in December 2019.

The crossfire of the Sahara conflict and the indiscriminate hunting of railroad workers to Nouadhibou (Mauritania) pushed red-necked ostriches, oryx, addax (antelope) and desert gazelles to the limit 50 years ago. The researcher and conservationist José Antonio Valverde, known as the Doñana’s father To promote the protection of the Andalusian national park, a Spanish army captain and a photographer then devised an unusual rescue operation of the last specimens of dama gazelles (also known as mhorr), an African ungulate that can reach 75 kilometers per hour, but was unable to evade the killings with automatic weapons and SUVs. They disappeared from their natural environment. The only ten specimens that survived thanks to that quixotic operation took refuge in Almería. Half a century later, its descendants and those of two other spices (dorcas and cuvier) are now four thousand and have been reintroduced in Tunisia, Morocco and Senegal. One of the great challenges has been to manage the forced inbreeding by having a meager population for reproduction.

Valverde, a biologist and naturalist, had already participated in research expeditions in Africa. But it was in the Sahara, in 1970, where he fell in love with the gazelle mhorr, an antelope, as he describes in his memoirs, “dazzling white and brown, incredibly slender and elegant.”

The disappearance of the species was imminent and there was no time to devise a long-term operation. The biologist learned that the Spanish captain Julián Estalayo, stationed at the Daora detachment in Western Sahara, was home to a dozen specimens of dama gazelles and negotiated their acquisition with him to transfer them to Spain and create a refuge.

Specimens of gazelle 'mhorr', at the Almería facilities 50 years after the rescue operation.
Specimens of gazelle ‘mhorr’, at the Almería facilities 50 years after the rescue operation.CSIC-EEZA (Europa Press)

Manuel Mendizábal, then director of the Almería Acclimatization Institute (today called the Experimental Station of Arid Zones, EEZA, of the CSIC), offered his facilities, whose climatic and aridity characteristics were similar to those of the desert from which the animals came. The company was joined by the naturalist, journalist and photographer Antonio Cano, a friend of Valverde and who started the current Saharan Fauna Rescue Center, located on the La Hoya farm.

The Almería Provincial Council assumed the maintenance costs and the Army made a Douglas DC-4 aircraft available to the group to transport the specimens. In 1971, the first refugees arrived. In four years they added 19 copies.

The host plan immediately became a captive breeding program that would ensure the survival of the species and allow for the recovery of a sufficient group to reintroduce the specimens in the place where they belonged. The researcher Mar Cano, daughter of the photographer and who died in 2015, successfully achieved the objectives and expanded the work to other endangered species: At the mhorr (Gazella dama mhorr) Dorcas joined (Gazella torcas), Cuvier’s gacelas (Gazella cuvieri) and mouflon ruined (Ammotragus lervia sahariensis), from Smara, El Aaiún or Dakhla.

Programs have managed to save species from extinction

Teresa Abáigar, researcher at the EEZA-CSIC

The plan was successful and in 14 years the first specimens from captive breeding in Almería could be reintroduced in Africa, a program to which other Spanish centers have joined. The EEZA-CSIC researcher, Teresa Abáigar, now assures, 50 years after that environmental adventure, that “the programs have managed to save species from extinction.”

But the plan still has to face difficulties and threats. The first, to ensure that specimens bred in captivity and without predators, can survive in the environment that was theirs. In this sense, Abáigar explains: “We try to intervene as little as possible and, when a reintroduction is made, a progressive adaptation to another type of diet, to another space and to a social organization that depends on them and not on us is encouraged”.

The biologist adds that it is also a challenge for them to learn to identify their predators after years of living in a harmless environment. So far they have been reintroduced, mainly, in protected reserves, but that has not prevented some encounters with jackals. However, its biggest predators are still people: “The main problem is poaching.”

Release of a mhorr gazelle in Western Sahara.
Release of a mhorr gazelle in Western Sahara.

Another difficulty is the limitation of space. The 20-hectare farm in Almería currently has about 400 specimens and, according to Abáigar, “now it is practically at the limit of its capacity”. Added to that are the difficulties of breeding, such as disease prevention.

But the fundamental challenge from the beginning was to recover a species from such a small number of specimens, that it condemned the herd to inbreeding. However, an investigation by Eulalia Moreno, from the CSIC, in collaboration with Aurora García-Dorado, from the Complutense University of Madrid, and Eugenio López-Cortegano, from the University of Edinburgh, has determined that the management of this limitation has become an advantage by “favoring natural selection to maintain good juvenile survival in Cuvier’s gazelles and mhorr”.

According to research, published in Heredity, of the Nature group, although it is always expected that smaller populations show less aptitude and adaptation potential, the experience in the Almeria center has shown that these limitations can be minimized “allowing a certain level of random mating and natural selection or carrying out reintroductions in nature as soon as possible ”.

The main goal must always be to increase the size of the population as much as possible while maintaining the greatest genetic variability, but it must also be given the opportunity for natural selection to act to a greater or lesser degree

Eulalia Moreno, researcher at the CSIC

Captive breeding programs for endangered species most often start with a very small population size; not infrequently, with less than 10 individuals, as is the case of three of the four species in the center of Almería, according to the CSIC. Under these conditions, the main concern of the managers of these programs is to minimize the loss of genetic diversity in the population and to avoid as much as possible inbreeding, which normally makes individuals more vulnerable. According to Moreno, this study shows that in two of the four species managed in the EEZA, Cuvier and mhorr, the management of inbreeding “has favored the purge of some harmful genetic variants, which has contributed to maintaining a good survival of the offspring of these two species and, probably, to allowing the subsistence of the populations”.

In this sense, the researcher explains: “In populations of threatened species, especially if they are managed through captive breeding programs, the main goal should always be to increase the size of the population as much as possible while maintaining the greatest genetic variability. , but it is also necessary to give opportunity for natural selection to act to a greater or lesser degree and it must be taken into account that the systematic choice of reproductive pairs with minimal kinship reduces the possibilities of purging by natural selection of many harmful variants ”.

The results of the work also show that the elimination of harmful variants in the populations must occur slowly and progressively, to avoid the collapse that would lead to a rapid and high increase in consanguinity.

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