A yellow turtle against silhouettes of hundreds of tropical fish.

Scientific links of the week » Explorersweb

A passion for the natural world drives many of our adventures. And when we’re not really outdoors, we like to dive into the discoveries of the places we live and travel. Here are some of the best natural history links we found this week.

Life on the Great Pacific Garbage Patch: In 2019, Benoit Lecomte swam across the Great Pacific Garbage patch to raise awareness of plastic pollution. The patch, between Hawaii and California, contains 79,000 tons of plastic waste.

As he swam, he noticed sea life around him. In some areas, there were almost many organisms living on the surface in the form of plastic. The gigantic heap of floating garbage had become a habitat.

Researchers believe that the same gyres that cause the accumulation of waste have also brought in marine wildlife. They fear that this newly discovered life among the plastic will hamper conservation efforts.

A couple of unusual monkeys

Hybrid monkeys in Borneo: In 2017, a photographer captured an unknown species of monkey in Borneo. At the time, the monkey was a juvenile, so researchers had trouble identifying the creature. Over the years, more photos and in-person sightings have led to a better understanding of this animal, now a mature female.

The monkey appears to be a hybrid of two species that share the same habitat, a proboscis monkey and a silver langur. “She seemed to be breastfeeding a baby. We were all amazed,” said primatologist Nadine Ruppert.

It is very rare for different species to mate and produce viable offspring. In these few cases, the two species are very similar. But proboscis monkeys and silver langurs don’t even belong to the same genus.

“We concluded that male proboscis monkeys mate with female silver langurs…and that there are mixed groups where female proboscis monkeys even care for baby silver langurs,” Ruppert said.

Hawksbill turtle Photo: Shutterstock

A turtle’s sense of direction is pretty bad, actually.

Migratory sea turtles do not know where they are going: Researchers have made new inroads into that perplexing old question, how do migrating animals know where to go? In the case of sea turtles, most of the time this is not the case.

Scientists tracked the movement of hawksbill turtles as they swam from their breeding grounds in an Indian Ocean archipelago to various feeding sites. Over shorter distances, they zigzagged until they reached their destination. Most of the time they swam double the distance in a straight line. In one case, a particularly erratic turtle swam 1,306 km to reach a location 176 km away.

As marine scientist Graeme Hays said, “They’re almost certainly using a geomagnetic map, but that’s a pretty coarse resolution.”

They use this “map” to reach the general area they are looking for, then use visual cues and scents to navigate to their final destination.

Female octopuses self-harm to death after laying eggs: After laying their eggs, female octopuses stop eating and eventually starve to death. By the time the eggs hatch, the mothers are dead.

This unusual maternal behavior occurs because of the optic gland of octopuses. One way or another, it alters cholesterol metabolism and, in turn, steroid hormones. Steroids increase in three ways after breeding. First, the octopus produces the steroids necessary for pregnancy. Second, they produce bile acid. Third, they increase levels of a particular chemical called 7-DHC, which is a precursor to cholesterol. In humans, high levels of 7-DHC are a symptom of a genetic condition known to cause repetitive self-harm. This is mirrored by female octopuses.

The beauty secrets of dolphins

Corals are dolphins skin care: Biologist Angela Ziltener was diving in the Indo-Pacific when she noticed dolphins lining up to rub against coral. Ziltener observed it several times and came up with a theory. She believes the rubbing transfers antibacterial compounds and antioxidants from corals and sea sponges to the dolphins’ skin.

Dolphins only show this behavior with gorgonian and leather corals. These corals contain 10 antibacterial compounds, which help dolphins maintain healthy skin.

Two dolphins swimming above each other

Bottlenose dolphins rub against the coral. Photo: Shutterstock

Wild pigs increase the number of crocodiles: In the 1970s, crocodile numbers in Australia were at an all-time low due to unregulated hunting. Since then, conservationists and the government have worked to protect them. More than 100,000 crocodiles now live in the Northern Territory.

One of the reasons for this success is the changing diet of crocodiles. Researchers compared natural carbon and nitrogen isotopes in crocodile bones and tissues. Over the past 50 years, carbon 13 and nitrogen 1 have decreased. This showed that crocodiles are moving away from a diet based on marine estuaries. Instead, they feast on wild pigs and buffaloes. Feral pigs are an invasive species and the crocodile boom has helped control the damage these pigs cause.

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