Owl droppings — more than meets the eye

Humans build fences. Dogs water fire hydrants. And new evidence is suggesting the owls might use their own feces to demarcate their territories. 

The new finding, reported in the August 20 issue of the journal PLoS ONE, hasn’t been reported very widely for the same reason my ever-astute editors at National Geographic News declined to publish it: it’s very preliminary. But it’s bizarre enough to warrant a post on my fledgling blog!

The research team that keyed into the well-placed owl droppings is based at the Estación Biológica de Doñana in Seville, Spain.

A prevailing belief has it that social communication between nocturnal critters is most often vocal. But co-authors Vincenzo Penteriani and María del Mar Delgado weren’t satisfied with that. 

After all, species like the satin bowerbird do very visual things like chew plants and paint objects with a plant-saliva mix during courtship (the females then peck at it). See more about that wild scene at the University of Maryland’s website, http://www.life.umd.edu/biology/borgialab.

Furthermore, the researchers were noticing abundant, “extremely visible” signs like white feces and prey feathers on posts and other conspicuous areas, especially during the nesting period for eagle owls. 

Among other investigations, Penteriani and Delgado visited the owl territories throughout the year, and found that the owls ramp up their defecation in the months leading up to the birth of their young (September to March), but then abruptly stop showing off their feces if the nests fail, or once the young owls fledge. And when the researchers covered up the fecal markings with spray paint, the owls replaced them in an average of two days — sometimes in less than 24 hours — in the exact same spot.

The owls’ trick may help protect the nest and save energy, as eagle owls are known to be fierce defenders of their nests. For many species, there might be a risk in advertising nest locations, but owls don’t have too many natural predators, the authors point out.

In a statement, Penteriani said that feces “may represent an ideal substance for marking, because it has a minimal energetic cost to the signaler.”

Penteriani and Delgado admit that their results are speculative, and more research is needed. But it’s neat to know there are modes of animal communication to which we are still blind — with new ones just waiting to be discovered.

The full eagle owl study is here: http://dx.plos.org/10.1371/journal.pone.0003014