The tiny elusive vaquita has the sad honor of being the most endangered marine mammal in the world. Paula Olson/NOAA/Wikimedia Commons

The plight of the vaquita, the world’s most endangered marine mammal, is well known. The smallest of all cetaceans, their numbers have plummeted over the last few years to the point where extinction is almost guaranteed. From around 100 animals in 2014, their numbers dropped to just 30 in 2017, and estimates now put them at around just 10 left on the planet.

However, the little porpoises are so elusive, researchers have had to revise population estimates a few times, and are still learning about their behavior.

Recent expeditions to survey the mammals have offered a tiny glimmer of hope: scientists spotted three pairs of mothers and calves. Not only does this mean the porpoises are still reproducing, but it may mean vaquitas actually produce young every year, instead of every other year as previously thought.

Vaquitas only live in a small strip of the Gulf of California’s northern tip, near Mexico. Despite the Mexican government’s efforts to enforce a protected refuge for the vaquita, the cause of their dramatic decline is also well-known: illegal fishing practices.

The vaquitas share their habitat with the (also critically endangered) totoaba fish, a hugely prized commodity in China for its supposed "medicinal value", the bladders of which can fetch thousands of dollars on the black market. Poachers use gillnets – despite them being banned by the government – to catch the fish, and the vaquitas inevitably end up caught in them.

Increasingly desperate efforts to save the animals from extinction have included the government teaming up with Leonardo DiCaprio’s Foundation to pledge to conserve their ecosystem, deploying Navy-trained dolphins to locate them, and various attempts to round up and move them to a specially protected marine refuge to start a captive breeding program, which had to be abandoned after the death of a female caught.

Visual surveys of the vaquita carried out in August and September of this year yielded sightings of at least six different individuals from two groups, reports Mongabay. Now, another expedition in October spotted three mother and calf pairs.

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“So the good news is they are producing calves,” Lorenzo Rojas-Bracho, head of the Marine Mammal Research Group for the Mexican National Commission of Natural Protected Areas, told the San Diego Union-Tribune. “And we have the survivors who have been able to survive all these years, and it’s important to protect them, because the survival of vaquita depends on these individuals we have now.”

Rojas-Bracho and colleagues have been monitoring the remaining animals with acoustic equipment for the last few years. They also observed mothers and babies in 2017 and 2018, authoring a paper that suggests despite previous indications that vaquitas gave birth every other year, the ability to identify the remaining individuals and the observations of the same animals with a new calf in consecutive years suggested that vaquitas, like harbor porpoises, are capable of annual calving.

"The ability of a small population to recover after a severe decline is strongly influenced by its reproductive biology," they wrote in the study published in Marine Mammal Science. If the vaquitas really are more inclined to reproduction than previously thought this could be key to bringing them back from the brink. The biggest hurdle is enforcing the gillnet ban, something the Mexican government is under fire from as per multiple accounts the illegal poaching is still rampant in the federally protected Vaquita Refuge in Mexico.

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