title: Coping with copepods: do right whales (Eubalaena glacialis) forage visually in dark waters?
abstract: North Atlantic right whales (Eubalaena glacialis) feed during the spring and early summer in marine waters off the northeast coast of North America. Their food primarily consists of planktonic copepods,Calanus finmarchicus, which they consume in large numbers by ram filter feeding. The coastal waters where these whales forage are turbid, but they successfully locate copepod swarms during the day at depths exceeding 100 m, where light is very dim and copepod patches may be difficult to see. Using models ofE. glacialisvisual sensitivity together with measurements of light in waters near Cape Cod where they feed and of light attenuation by living copepods in seawater, we evaluated the potential for visual foraging by these whales. Our results suggest that vision may be useful for finding copepod patches, particularly ifE. glacialissearches overhead for silhouetted masses or layers of copepods. This should permit the whales to locateC. finmarchicusvisually throughout most daylight hours at depths throughout their foraging range. Looking laterally, the whales might also be able to see copepod patches at short range near the surface.This article is part of the themed issue 'Vision in dim light'.
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA cronin@umbc.edu.
authors.forename: Thomas W
authors.identifier: http://orcid.org/0000-0001-7375-9382
authors.initials: TW
authors.lastname: Cronin
authors.affiliation: Department of Biological Sciences, The University of Tampa, Tampa, FL 33606, USA.
authors.forename: Jeffry I
authors.initials: JI
authors.lastname: Fasick
authors.affiliation: Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL 32901, USA.|Biology Department, Duke University, Durham, NC 27708, USA.
authors.forename: Lorian E
authors.identifier: http://orcid.org/0000-0001-6903-5226
authors.initials: LE
authors.lastname: Schweikert
authors.affiliation: Biology Department, Duke University, Durham, NC 27708, USA.
authors.forename: Sönke
authors.identifier: http://orcid.org/0000-0002-3943-8320
authors.initials: S
authors.lastname: Johnsen
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA.
authors.forename: Lorren J
authors.initials: LJ
authors.lastname: Kezmoh
authors.affiliation: Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
authors.forename: Mark F
authors.initials: MF
authors.lastname: Baumgartner
mesh_terms: D000818:Animals; D033342:Copepoda; D003624:Darkness; D005247:Feeding Behavior; D020387:Food Chain; D014796:Visual Perception; D014907:Whales / Q000502:physiology*
keywords: contrast vision; environmental radiometry; right whale; visual sensitivity