Panda

Ever woken up to find that a crafty raccoon has overturned your garbage bin and spread the discarded contents of your life across the street? Raccoons—sometimes referred to as "trash pandas"—are renowned as excellent innovators and problem-solvers who can often find their way through the trickiest barriers in their search for food.

Mammals are not especially diverse. Roughly 6,800 mammal species are known to exist, compared with about 8,800 species of amphibian, 11,000 species of bird and 12,500 of reptile. Yet when most people picture biodiversity, they often think of charismatic mammals first: pandas, orangutans, elephants or tigers.

Members of the arachnid class—think spiders, scorpions and harvestmen (daddy long legs)—are often the targets of revulsion, disgust and fear. Yet, they are crucial for ecosystems to thrive. Given the crash in worldwide biodiversity, including what some call the "insect apocalypse," a pair of ecologists at the University of Massachusetts Amherst decided to check in on the general state of insects and arachnids in the U.S.—only to discover massive gaps in the data.

Scientists have uncovered an elegant biophysical trick that tuberculosis-causing bacteria use to survive inside human cells, a discovery that could lead to new strategies for fighting one of the world's deadliest infectious diseases.

It might be less visible than dwindling lion populations or vanishing pandas, but the quiet crisis of small mammal extinction is arguably worse for biodiversity. These species are crucial indicators of environmental health, but they can be very hard to monitor, and many species with very different ecological niches look almost identical.