NatureWrap: Blue whales return to South Georgia

Critically endangered Antarctic blue whales are returning to the sub-Antarctic island of South Georgia five decades after whaling all but wiped them out.

That good news, provided by a UK-led team in the journal Endangered Species Research, is based on analysis of 30 years of sightings, photographs and underwater sound recordings. It follows recent research showing that humpback whales also are back in the region.

Blue whales were abundant off South Georgia until 42,000 were killed during industrial whaling from 1904 to 1971. Only one was sighted by dedicated whale surveys between 1998 and 2018, but a survey in February reported 58 sightings and numerous acoustic detections.

“[W]e have become quite optimistic about the numbers of blue whales seen and heard around the island, which hadn’t been happening until very recently,” says lead author Susannah Calderan of the Scottish Association for Marine Science (SAMS). “This year was particularly exciting, with more blue whale sightings than we ever could have hoped for.”

Plants know when we’re around

Can the presence of people affect how plants grow? Quite possibly, suggests a new study in the journal Current Biology.

Researchers from China and the UK say a plant used in traditional Chinese medicine has evolved to become less visible to humans. Fritillaria delavayi, which live on rocky slopes of the Hengduan mountains, match their backgrounds most closely in areas where they are heavily harvested.

“Many plants seem to use camouflage to hide from herbivores that may eat them, but here we see camouflage evolving in response to human collectors,” says Martin Stevens from the University of Exeter. “It’s possible that humans have driven evolution of defensive strategies in other plant species, but surprisingly little research has examined this.”

The researchers measured how closely plants from different populations matched their mountain environment and how easy they were to collect, then spoke to local people to estimate how much harvesting took place in each location. They found that the level of camouflage in the plants was correlated with harvesting levels.

In a computer experiment, more-camouflaged plants also took longer to be detected by people.

“Commercial harvesting is a much stronger selection pressure than many pressures in nature,” says Hang Sun, from the Kunming Institute of Botany. “The current biodiversity status on the Earth is shaped by both nature and by ourselves.”

Fritillaria delavayi in a population with low (left) and high harvest pressure. Credit: Yang Niu

What’s your poison?

Locals have long suspected the African crested rat (Lophiomys imhausi) is poisonous, and now researchers have confirmed it.

In fact, says a team from the US and Kenya, its fur is packed with a poison so lethal it can fell an elephant; a few milligrams can kill a human. It is the only mammal known to sequester plant toxins for chemical defence, they write in a paper in the Journal of Mammology (which also explains more about its social life).

A previous study reported a single L. imhausi sequestering toxins from the poison arrow tree (Acokanthera schimperi) – a source of traditional arrow poisons – and this is confirmed by the new work, which documented 25 of them for 1000 hours.

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Credit: Stephanie Higgins

Closer study revealed that the animals sequester the poison into special hairs. Exposure to the Acokanthera toxins did not alter their behaviour, and neither did eating milkweed, the same cardenolide-enriched plant used as chemical defence by monarch butterflies.

Combined, the researchers say, these observations suggest that crested rats are uniquely resistant to these toxins. “Most people think that it was a myth because of the potency of the tree,” says co-author Katrina Nyawira. “But we caught it on video. It was very crazy.”

The project was a collaboration between the University of Utah, Smithsonian Conservation Biology Institute, and National Museums of Kenya.

You’re on your own kid

Some songbirds avoid putting all their (former) eggs in one basket, researchers suggest.

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Radio-tagged fledgling Common Yellowthroat. Credit: Todd Jones

Two thirds of the species they studied in habitats across the US throw fledglings out of the nest before they are really ready – and thus at greater risk – in the hope that some will survive, the team from the University of Illinois writes in a paper in the journal PNAS.

“The parents are distributing the risk,” says senior author Mike Ward. “The longer chicks stay in the nest, the greater the chance the whole brood will be lost to predators like snakes or raccoons.

“But we see parents physically separating chicks in space outside the nest, and that way, the probability of them all dying is almost zero.”

Ward says he is a little surprised at quite how ruthless the parents are but “it makes sense from an evolutionary perspective”. Putting a lot of resources into kids favours their survival, but can leave parents depleted, at risk of predation or disease, and potentially less able to produce additional offspring.

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