{'fraction_non_alphanumeric': 0.02891566265060241, 'fraction_numerical': 0.001606425702811245, 'mean_word_length': 5.048543689320389, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Shallow torpor keeps hummingbirds on their toes when conserving energy

Keeping warm is costly, especially when paired with one of the world’s fastest lifestyles. During the day, hummingbirds zip about feeding on sugar-rich nectar to fuel their high-octane existence, but at night, the aeronautic acrobats must conserve energy, slipping into a miniature form of hibernation, known as torpor; many drop their body temperature to around 10°C and some get even chillier. But animals that use torpor are in danger from predators, so some minimise the risk by entering a shallower version from which they can emerge more rapidly. However, it wasn’t clear to Anusha Shankar (Cornell University, USA), Catherine Graham (Swiss Federal Research Institute) and Donald Powers (George Fox University, USA) whether birds are also capable of using both shallow and deep types of torpor, either to avoid incurring the costs of deep torpor or as an intermediate step along the way. To find out, Shankar with Powers, Isabelle Cisneros and Sarah Thompson, also from George Fox University, headed to the Chiricahua Mountains of Arizona, USA – home to many migrating hummingbirds during spring and summer – to find out how the energetic birds deal with cold nights.