These generous creatures show that the right present can be the key to winning another’s heart
Gentoo penguins search for the perfect pebble to give their partner
Gentoo penguins mainly live in coastal Antarctica, inhabiting colonies that can consist of several thousand individuals. In such a large community, it can be tricky to stand out from the crowd. But the males of this species have developed an endearing way to win a partner’s heart: males gather pebbles to present as tokens of love to potential mates.
From smoothness to size, each pebble is carefully considered before the male penguin presents his pick to the female. Choosing the right stone is of utmost importance, and gentoos are willing to play dirty to get the one they want, stealing from other penguins in order to secure the ideal prize.
The pebbles aren’t mere ornaments; they’ll be used as part of the female’s nest, where she’ll lay a pair of spherical eggs and share
incubation duties with her male partner. When the chicks are born, they’ll remain in the nest for around a month. Both parents help to ensure that the baby birds remain safe and well fed. Throughout this process the male and female develop a strong bond; consequently, they often remain partners for life.
Chimps and bonobos give food to form social bonds
Chimpanzees and bonobos are some of our closest relatives; humans share around 99 per cent of their DNA with these genetically similar great apes. It’s perhaps no surprise then that the jungle-dwelling primates exhibit behaviours also found in human culture.
Gift giving is one such example. Scientists observing the social structures of these apes have found that both species give gifts of food to other individuals, seemingly without the expectation of anything in return.
However, a deeper look at this apparently altruistic behaviour reveals that their motives
may not be entirely selfless. Although there’s not always a short-term reward for sharing food with other group members, scientists found that female chimpanzees were more likely to mate with males who had shared with them over the previous few months.
Likewise, while bonobos have been observed donating food to strangers, researchers found that this is only the case when there’s a possibility for social interaction — in other words, the gift giver usually gets something in return for their generosity, even if they have to wait.
These snails use not-so-romantic love darts to increase their fertility
Stabbing your partner with a mucus-filled dart sounds more macabre than romantic. Yet this is a precoital behaviour commonly undertaken by gastropods: around one-third of all snail species produce ‘love darts’ to aid their reproduction.
Most snails are hermaphrodites, meaning they have both male and female organs. Their love darts, which are made from calcium carbonate or chitin, contain mucus and hormones that help the snail’s sperm survive for longer once transferred to a partner.
This is helpful since snails’ bodies have evolved to be picky about the sperm that they accept. The love darts help to break down the other snail’s natural defences, maximising the sperm donor’s chances of successful reproduction. However, this process can cause early death.