This undated image, published by the National Oceanic and Atmospheric Administration (NOAA), shows a mother and calf emerging in the waters off San Felipe, Mexico.

Vaquita guinea pigs are on the verge of extinction, with only 10 remaining in their only habitat in the Gulf of Mexico.


However, a new study published Thursday in the journal science offers some hope: the world’s rarest marine mammals are not doomed to a lack of genetic diversity and can recover if illegal gillnet fishing stops immediately.

“We’re trying to dispel the idea that there’s no hope that nothing we’re doing can save them right now. It’s just not an assumption,” lead author Jacqueline Robinson of the University of California, San Francisco, told AFP.

Guinea pigs are closely related to dolphins and share many common things, including great intelligence.

Wakita, whose name means “little cow” in Spanish, is four to five feet (about 1.5 meters) long, making it the smallest of all cetaceans.

Shy and elusive, they are known for their distinctive dark circles around their eyes and relatively large dorsal fins, which are thought to help dissipate heat in their warm habitat.

The number of wokis was destroyed in the 20th century as a result of accidentally trapped and drowned in gillnets: long walls of nets hanging in open water, used to catch fish and shrimp.

Fishermen were looking in particular for totoaba, a large wakita-sized fish whose swimming bladder is valuable in traditional Chinese medicine.

Totoaba itself is endangered and its fishing is illegal, but the ban is not always observed.

The historical abundance of vaquita is unknown, but by the time of the first study, in 1997, only about 570 remained.

There were fears that harmful mutations among surviving wakites could seal the fate of the species due to inevitable inbreeding.

To find out if this is the case, the researchers analyzed the genomes of 20 wakites who lived between 1985 and 2017 and found that in the last 250,000 years, their population has never exceeded several thousand.

They also learned that their genetic diversity has always been low compared to other cetacean species such as dolphins, killer whales and other whales.

This material was taken in the photo on October 18, 2017 and issued by the Mexican Minister of Environment and Natural Resources (Sem

This material, taken in a photo taken on October 18, 2017 and published by the Mexican Minister of Environment and Natural Resources (Semarnat), shows scientists with a six-month-old wakita calf.

Benefits of low genetic diversity

“In general, we would think that low genetic diversity is a bad thing. But in this case, it’s somewhat beneficial to the Wakits for their ability to recover,” Robinson said.

Inbreeding increases the chances of offspring inheriting two copies of harmful mutations, leading to genetic disorders.

But the frequency of these mutations has been shown to be very low in vaquitas, as the population has always been small.

“So these mutations have historically been eliminated much more effectively than in a larger population, where these mutations can continue and remain hidden from natural selection,” Robinson explained.

There are other species that appear to be more resistant to so-called “inbreeding depression”, including mountain gorillas and narwhals, for similar reasons.

The team then performed simulations to predict the future of the species.

It is encouraging that there is only a six percent chance of vaquitas disappearing if gillnet fishing is eliminated.

But if such fishing is only reduced, then the risk of extinction increases dramatically.

Even with an 80% reduction in fishing, guinea pigs have a 62% chance of disappearing.

“While we now know that the species’s ability to recover is not limited by their genetics, vaquitas have very little time left,” said co-author Christopher Kyriazis of the University of California, Los Angeles.

“If we lose them, it will be the result of our human choices, not inherent genetic factors.


Only 10 vaquita guinea pigs survive, but the species may not be doomed


More information:
Jacqueline A. Robinson et al, The critically endangered vaquita is not doomed to extinction through inbreeding depression, science (2022). DOI: 10.1126 / science.abm1742. www.science.org/doi/10.1126/science.abm1742

© 2022 AFP

Quote: Inbreeding will not doom the last of the vakiti, but fishing can: a study (2022, 8 May), drawn on 8 May 2022 from

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https://phys.org/news/2022-05-inbreeding-wont-doom-vaquitas-fishing.html

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