Researchers test fiddler crab mating strategies by introducing a robot with a waving claw, dubbed “Wavy Dave.” CNN speaks to one of the scientists about the study and some surprising moments caught on camera.

Exeter

Researchers at the University of Exeter developed a robot, named Wavy Dave, to study the courtship tactics of male fiddler crabs. The robot, equipped with interchangeable claws, was placed among real crabs to observe their reactions during mating displays.

The study found that male fiddler crabs altered their behavior in response to the robot, extending their courtship displays and spending less time in their burrows. Some males were deterred by larger robotic claws, while others continued to compete, even managing to break off the robot's claw in some cases. The findings, published in Proceedings of the Royal Society B, highlight the adaptability of animal behavior in the face of novel challenges.

Crab vs. machine: Robot tests fiddler crab courtship tactics

It's crab versus machine. As researchers at the University of Exeter built this robot, dubbed Wavy Dave, to study how male fiddler crabs compete for female attention. Male fiddler crabs have an enlarged claw and it can weigh up to 30% of their entire body mass. They wave it about to attract the attention of female crabs. And the female crabs prefer males that wave faster and have a larger claw. Scientists placed Wavy Dave on a mudflat teeming with thousands of crabs and gave the robot claws of varying sizes to wave near a real male's burrow. I was very surprised at how they reacted because the pessimist in me thought they won't see this as a crab, that they'll see through it, that we're essentially trying to pull a magic trick on them. And I didn't think that it would work. Cameras captured how the crabs adapted, finding that the males abandoned their normal routines and continued waving their massive claw to compete with the robot. Adapting your strategy and kind of rolling with the punches, that's not something that's special to humans. We know how males are responding to this robot. They're lengthening their courtship out, so they're signaling for longer and they're spending less time in their burrow. The results of the study, published in the journal Proceedings of the Royal Society B, show that while some males were less likely to compete when a rival had a larger claw, others would not back down from this robotic intruder. The fight between the fiddle crab and Wavy Dave, I wasn't expecting it when the individual did manage to break the claw off. I thought it wouldn't be strong enough. That just goes to show you should never try and predict what's going to happen when you're working with animals.

After almost four decades of a bloody conflict that until recently had no end in sight, Azerbaijan and Armenia signed a peace agreement in the presence of the US President Donald Trump. Notably absent in this historic moment is Russia, which no longer plays a central role in the South Caucasus.

Washington

Azerbaijan and Armenia sign historic agreement

Montana's governor said that the dayslong manhunt for the suspect in a bar shooting has ended. 45-year-old Michael Brown was taken into custody on Friday.

Anaconda

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President Trump announced Friday that he will hold a one-on-one meeting with Russian President Vladimir Putin on Aug. 15 in Alaska. The summit comes as Russia has been pushing to keep all the Ukrainian territory it gained from its invasion. Nancy Cordes and Margaret Brennan have the latest.

Ukraine Invasion

Trump, Putin to hold meeting in Alaska next week

The U.S. Department of Justice issued subpoenas in its investigation into New York Attorney General Letitia James. CBS News' Jake Rosen reports.

New York

Trump's DOJ subpoenas New York AG Letitia James

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Moscow

Kremlin says Trump, Putin to meet soon; Ukraine seeks role for Europe

U.S. President Donald Trump's rushed deadline for Russia to strike a ceasefire deal or face more sanctions has arrived without much movement from Russian President Vladimir Putin.

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Protesters in Israel are voicing their concerns about a plan approved by Prime Minister Benjamin Netanyahu's Security Cabinet to take over Gaza City. CBS News' Debora Patta has more.

Jerusalem

Middle East Conflict

Israel's security cabinet approves plan to take over Gaza City

Israeli Prime Minister Benjamin Netanyahu says Israel intends to take full military control of Gaza and push a new offensive, despite mounting international criticism over the war’s human toll and growing hunger crisis.

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U.S. President Donald Trump said that there is a good chance he'll meet with Russian leader Vladimir Putin soon over Russia's war with Ukraine.

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U.S. President Donal Trump officially began levying higher import taxes on dozens of countries on Thursday (August 7), just as the economic fallout of his months-long tariff threats was beginning to create visible damage to the U.S. economy.

Global Tariffs

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The man accused of killing two Israeli Embassy staffers in Washington, D.C., earlier this year has been charged with federal hate crime charges. CBS News Justice reporter Jake Rosen has more.

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Mike Huckabee, the U.S. ambassador to Israel, blamed Hamas when asked about starvation in Gaza, saying, "Hamas has not allowed the food to get to the people who are hungry." Huckabee also addressed questions over the controversial aid sites.

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On "T-Day," the US began enforcing Trump's new tariffs, raising average rates from 2% to 15% after a 90-day pause allowed some countries to negotiate reduced deals while others, like India and Brazil, faced hikes. These tariffs have generated over $150 billion in revenue by July, impacting various sectors and aiming to address trade imbalances.

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Brazil’s President Luiz Inacio Lula da Silva says he plans to call the leaders of China and India, to discuss a joint response to new US tariffs. The announcement came as Brazil and India were hit with 50 percent levies - the highest imposed by President Donald Trump.

State of Rio de Janeiro

Brazil halts U.S. trade talks as Lula condemns new tariffs

U.S. President Donald Trump imposed an additional 25% tariff on Indian goods, citing New Delhi's continued imports of Russian oil in a move that sharply escalated tensions between the two nations after trade talks reached a deadlock.

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President Trump has been briefed about the shooting at Fort Stewart in Georgia, the White House press secretary says. At least five soldiers were shot before a suspect was apprehended, officials say.

Fort Stewart

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A Russian official said President Trump's special envoy to the Middle East, Steve Witkoff, had a "useful and constructive" conversation with Russian President Vladimir Putin in Moscow on Wednesday.

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The U.S. aims to deploy nuclear power reactors on the Moon and Mars, targeting the first launch by decade’s end. A new NASA directive, revealed by Politico and AFP, calls for appointing a nuclear power czar to choose two commercial proposals within six months, aiming to outpace a Chinese-Russian collaboration.

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Japan held a memorial service and ceremony for victims and the remaining survivors of the U.S. atomic bombing of Hiroshima, marking its 80th anniversary and renewing pledges of working towards a world without nuclear weapons.

Hiroshima

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The U.S. is warning travelers as cases of chikungunya, a mosquito-borne illness, spreads in China. Health officials in China have ordered mass disinfection measures. The region near Hong Kong reported more than 7,000 cases in recent weeks.

Beijing

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Japan has commemorated the 80th anniversary of the Hiroshima atomic bombing during World War II. Ceremonies at Peace Memorial Park honoured the victims of the 1945 nuclear attack by US forces.

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Multiple media outlets in Israel have reported that Israeli Prime Minister Benjamin Netanyahu wants a complete military takeover of Gaza, while almost 600 former Israeli military and security officials are petitioning Washington to stop the fighting.

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Ukrainian President Volodymyr Zelenskyy said Tuesday that he had a productive talk with President Trump focused on ending the war with Russia. CBS News national security contributor Samantha Vinograd has more.

Kyiv

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Family members of two of the victims from the 2023 implosion are demanding tougher regulations following the damning report released on Tuesday. Five people died when the submersible imploded off the coast of Newfoundland.

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The House Oversight Committee has subpoenaed multiple people over the Jeffrey Epstein files, including former President Bill Clinton and former Secretary of State Hillary Clinton. CBS News' Jake Rosen has more details.

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U.S. Customs and Border Patrol agents have been directed through a federal court order to stop deportations under President Trump's asylum ban, sources say. CBS News' Camilo Montoya-Galvez has more details.

Breakdown