The idyllic islands of the Caribbean can seem like paradise not only to people wanting to relax on the beach, but also to many birds who find predator-free havens in which to breed. But some of these islands hide a dark secret, home to a species of tree known to trap and kill fledgling birds, the bodies of which then go on to feed the trees themselves.
Known as “bird-catcher” trees, scientists have just discovered two new species of the macabre plants, describing them in the journal Phytokeys. The two large trees have been found concealed in the forests of Puerto Rico. The fact that two big plants have remained unknown to science on such a relatively small and well-studied island for so long makes the discovery for the scientists even more exciting.
Belonging to the group of Pisonia trees, the sinister actions truly read like something from a horror story. At the base of some bird-catcher trees, the ground is littered with small fragile bones, all that remains of their victims. Sometimes, a mummified body will dangle from the branches.
The trees produce fruits that are incredibly sticky and covered in little hooks. Ordinarily, these stick to the backs of visiting birds, which then transport them to other islands, spreading the seeds, but occasionally the plants turn on their messengers.
As the fruits fall to the ground, the sticky sap attracts insects that then get stuck. This, in turn, attracts birds looking for an easy meal, who themselves get trapped in the lethal combination of goo and hooks. Those birds that are not feasted upon by crabs and scavengers die of starvation as they can no longer fly, and then rot at the base of the trees, providing nourishment to the plant itself.
Occasionally, the birds do not even make it to the ground, and are left hanging from the branches. There are even reports of these grim decorations bringing in owls and other predators, which in turn get caught too and suffer the same fate.
“Birds are the main dispersal agents for Pisonia trees, carrying the sticky fruits glued to their feathers to distant islands,” explained Marcus A. Caraballo-Ortiz, who led the study. “However, sometimes these fruits can trap too tightly and even kills birds, as seen in documentaries. So far, we do not know of cases where birds have been trapped by the sticky fruits of the new species, but future studies will explore this possibility.”
The two new species have been named Pisonia horneae and Pisonia roqueae, to honor two extraordinary women, Frances W Horne and Dr Ana Roqué de Duprey, who both spent their lives dedicated to furthering education and botany.