Toxins on poison dart frog skin mold the skin's microbial community, boosting species variety and potentially even feeding some daredevil bacteria.

When fed peanuts, red squirrels in Britain developed weaker bites — showing that food supplements to threatened animals could have unintended side effects.

Experts say clinical obesity is more than a high BMI and instead is a disease in which excess body fat harms tissues, organs or doing daily activities.