A GAME OF CROCS & OTTERS
Crocodiles and alligators aren’t famous for playfulness, but a recent survey of crocodile experts reveals a host of unpublished observations, involving 10 crocodilian species, indicating an overlooked sense of fun.
Reported behaviours include repeatedly sliding down slippery slopes into water, surfing waves, giving piggyback rides to each other and playing with floating objects for long periods.
There was even an apparent game between river otters and an American alligator. The otters took to splashing water at the alligator, who lunged at them in response. When the alligator actually caught an otter in his jaws, he’d release it unharmed, and the game would continue. A spectacular case of a parasite manipulating its host involves a tiny wasp named Dinocampus coccinellae, which lays its eggs in ladybirds. After eating the ladybird from within, the larva emerges to pupate, and somehow compels its host to stand over it protectively until the adult hatches a week later.
Biologists have now found that the parasite relies on highly specialised assistance. The wasp harbours a virus, which, once transferred to the ladybird with the egg, accumulates in the victim’s brain and paralyses it.
Nolwenn Dheilly, one of the scientists involved, said that this is the first demonstration of a third party being involved in behavioural manipulation. But not, perhaps, the last. “We strongly believe that such three-way systems are extremely common, and that many parasites use microbes as biological weapons to modify the host to their advantage,” she said. Named after the crucial central stone at the apex of a masonry arch, a keystone species is one that plays a pivotal role in the functioning of an ecosystem. Its removal causes dramatic changes.
The term was first applied to the purple sea star, whose predatory behaviour boosts species diversity in Pacific coastal waters. Other examples include prairie dogs (which create specialised habitats), hummingbirds (which pollinate many different trees) and jaguars (which regulate a wide range of mammal populations).