Owls hunt at night when the moon is full and bright

The moon makes a difference for predators and prey. It’s easier to see during the full moon, which might mean greater opportunities for nocturnal predators, except that nocturnal prey might adjust their behaviour accordingly. It’s a delicate balancing act.

This paper looked at the changes in behaviour of eagle owls (Bubo bubo) over the lunar cycle. Not this Bubo:

This Bubo:

The team categorized their owls into “breeders” and “dispersers.” Over 459 nights (whew!), the team tracked the movements, predation, and calling of their radiotagged owls.

The breeders paid attention to the moon. The breeders were moving more, and calling more, on the nights of the full moon. The authors think that this is because hunting is less efficient on the darker nights of the full moon. Reasonable idea, but the discussion section describing how the reproductive status of the owls is affecting their behaviour is loaded with qualifiers like “could,” “might,” “could be interpreted,” “may be,” and “probably.” There’s more work to be done to clarify.

The dispersers, however, paid no attention to the moon. The authors argue that disperser might have the luxury of reducing their effort when there is less food to be had, which the breeding owls can’t do.

This is a slightly frustrating paper, because it is one small chunk of a long-term study. It seems like there are certain details that make lots of sense if you have read all the papers arising from this project, but that are hard to glean here. For instance, I can’t quite figure out how the team categorized breeders and dispersers. the distinction is probably spelled out in another paper in the series


Reference

Penteriani V, Kuparinen A, Delgado M, Lourenço R, Campioni L. 2011. Individual status, foraging effort and need for conspicuousness shape behavioural responses of a predator to moon phases. Animal Behaviour 82(2): 413-420. DOI: 10.1016/j.anbehav.2011.05.027

Photo by FurLined on Flickr; used under a Creative Commons license.