There are two known species of manta ray, the giant manta ray and the reef manta ray. Both populations are at-risk due to threats like fisheries and pollution. The IUCN lists the giant manta ray as endangered and the reef manta ray as vulnerable. Rachel T Graham/MarAlliance hide caption
Richard Leakey, Kenyan wildlife conservationist, places a rhino horn to be burned at the zoo in Dvur Kralove, Czech Republic, in 2017. Leakey, known for his fossil-finding and conservation work in his native Kenya, has died at 77. Petr David Josek/AP hide caption
A nurse practitioner fills a syringe with the Pfizer COVID-19 vaccine at the Beaumont Health offices in Southfield, Mich., on Nov. 5. Jeff Kowalsky/AFP via Getty Images hide caption
A woman walks by a closed store in a shopping mall in Montreal, Sunday as the COVID-19 pandemic continues in Canada. Some new measures put in place by the Quebec government, including the closure of stores, go into effect today. Graham Hughes/AP hide caption
Delta-8-THC is derived from the cannabidiol (CBD) in hemp plants. Gillian Flaccus/AP hide caption
Dr. Anthony Fauci said on Sunday that the CDC was considering adding testing negative to its recommendations for when people could stop isolating after testing positive. Anna Moneymaker/Getty Images hide caption
As the coronavirus pandemic drags on, there are still a lot of questions to be answered about how to keep kids safe. Cindy Ord/Getty Images hide caption
When Dr. Tiffany M. Osborn received her COVID-19 vaccination shortly after vaccines became available in late 2020, she felt hopeful about the pandemic's trajectory. A year later, she's sad and frustrated to see so many COVID patients in the ICU. Matt Miller / Washington University School of Medicine hide caption
A colorized electron micrograph image of a cell (red) infected with with SARS-CoV-2 virus particles (yellow), isolated from a patient sample. Science Source hide caption
Health care workers administer COVID-19 tests at a drive-through clinic in Sydney, Friday, Dec. 31. Australian health authorities have reported a record 32,000 new virus cases, many of them in Sydney. Bianca De Marchi/AP hide caption
A health care worker holds doses of J&J; vaccines at the Gandhi Phoenix Settlement in Bhambayi township, South Africa, on Sept. 24. A study of the J&J; booster shot in the country had promising results against the omicron variant. Rajesh Jantilal/AFP via Getty Images hide caption
A Pileated Woodpecker (Dryocopus pileatus) flies around a residential neighborhood in Silver Spring, Maryland, on April 28, 2012. The non-migratory Pileated woodpecker is the largest of the common woodpeckers found in most of North America. JEWEL SAMAD/AFP via Getty Images hide caption
The sun sets over the dark Manhattan skyline on August 14, 2003. A power outage affected large parts of the northeastern United States and Canada. Robert Giroux/Getty Images hide caption
An artist's rendition of the James Webb Space Telescope with its sunshield deployed. NASA hide caption
Dermatologist Dr. Jenna Lester treats her patient Geoffry Blair Hutto in the UCSF Primary Care clinic. Barbara Ries hide caption
A health care worker administers a COVID-19 PCR test at a free test site in Farragut Square on Tuesday in Washington, D.C. On Tuesday, the CDC revised data reflecting the prevalence of the omicron variant in new COVID-19 cases. Anna Moneymaker/Getty Images hide caption