This week, we have…

• A fun fact inspired by Metazooa

• Answers to last week's games

• Reader survey

Vampire bats are universal blood donors

Although vampires in movies are typically nasty creatures, you might be surprised to learn that vampire bats (Metazooa animal #784) have a softer side. While it's true that these tiny mammals feed exclusively on blood, the story of how they feed each other is a tale of animal altruism that's stranger than fiction.

Vampire bats live in colonies, and not every hunt is a success. If a bat fails to find a meal for two nights in a row, it risks starving to death. But here's where the bat community steps in: bats that have recently eaten will regurgitate blood to share with hungry companions. Essentially, they "spit up" a life-saving snack for a friend in need. Scientists call this "reciprocal altruism," and it's one of the best-studied examples in the animal kingdom. There is even evidence that bats keep track of who's helped them in the past and are more likely to return the favour to those generous friends in the future.

This bat-based social safety net is so effective that a single act of sharing can determine whether a bat survives or not. Biologist Gerald Wilkinson, who first studied this phenomenon in the 1980s, found that vampire bats form social bonds and even occasionally "adopt" unrelated pups in captivity, though researchers are still uncertain how often this happens in the wild. This makes their colonies surprisingly compassionate.

Learn more: National Geographic

Trivia

Answers to last week's games

Monday, September 22 to Sunday, September 28.

Linxicon

The following are the shortest paths from last week:

• #587 branch → tree → nature → abundance → frequent

• #588 forget → memorize → study → research

• #589 diet → food → wages → salary

• #590 define → meaning → explanation → signal

• #591 layer → shape → geometry → calculus → derive

• #592 north → place → working → excellent

• #593 professional → career → year

• #594 Play now!

Elemingle

• #243 Mendelevium

• #244 Curium

• #245 Vanadium

• #246 Oganesson

• #247 Boron

• #248 Calcium

• #249 Lanthanum

• #250 Play now!

Forgeous

Play Forgeous for Sep 29