Review
Visual Acuity and the Evolution of Signals

https://doi.org/10.1016/j.tree.2018.03.001Get rights and content

Highlights

Recent increased interest in visual acuity, the ability to perceive static spatial detail, has shown that acuity is highly variable, ranging over four orders of magnitude across species with image-forming eyes.

Human visual acuity is some of the highest in the animal kingdom, meaning that researchers may develop hypotheses regarding the function of spatial patterns that do not account for the relevant viewer’s sensory capabilities.

Signals can potentially exploit differences in visual acuity between species, which may arise due to differences in eye type, eye size, and/or viewing distance.

Because acuity can vary between two viewers of the same scene, it represents a promising yet understudied channel for private communication.

Small animals, particularly those with compound eyes, have low acuity and thus can only perceive fine patterns over very short distances.

Acuity, the fineness with which sensory systems perceive and parse information, limits the information that organisms can extract from stimuli. Here, we focus on visual acuity (the ability to perceive static spatial detail) to discuss relationships between acuity and signal form and evolution. Research suggests that acuity varies by orders of magnitude across species, and that most animals have much lower acuity than humans. Thus, hypotheses regarding the function of spatial patterns must account for the acuity of relevant viewers. New data quantifying acuity in a range of taxa allow us to examine correlations between acuity and ecology, elucidate the selective forces that receiver acuity places on signal evolution, and examine how signals might appear to viewers with different acuities.

Section snippets

Sensory Acuity

Animal behavior is influenced by the information that an organism can perceive and process, which is in turn mediated by sensory systems. Thus, studies of how animals interact with both other animals and with the environment must consider the relevant perceptual systems. One way that individuals can extract information is via signals, which also form the basis for communication [1]; thus, signals are fundamental to the behavior and fitness of organisms. Though many definitions of ‘signal’

Incorporating Visual Acuity into Studies of Signaling

Including acuity in studies of animal signaling is important for several reasons. First, humans have exceptionally high acuity, surpassed only by a few predatory bird species, and thus researchers sometimes develop hypotheses regarding signal function that do not reflect what is seen by the intended viewer. Second, because acuity dictates what patterns can and cannot be resolved, it determines the spatial information that can be extracted from visual scenes by signal receivers (hereafter

The Effect of Eye Size and Type on the Perception of Signals in Interspecies Interactions

Interspecies interactions, from mutualism to parasitism to predation, are often mediated by signals. However, assumptions about which viewers can resolve the details of a signal are often untested. In interspecies interactions, heterospecifics can impose selection pressure on signals that impact the success or efficiency of an interaction [31]. In the common case where two animals interact but have different acuities (Box 3), signals can be more distinguishable by heterospecifics but not

Concluding Remarks and Future Directions

The human ability to both see and process spatial patterns is elite in the animal kingdom. Our high acuity allows us to resolve fine-scale details that are likely not resolvable by the vast majority of animal viewers, and at far greater distances. The examples presented here are by no means exhaustive, and illustrate the importance of considering acuity when making hypotheses about the function of animal visual signals. For example, predictions that deserve further attention include that: (i)

Acknowledgements

We thank three anonymous reviewers, Drs Eric Warrant, Stephen Nowicki, and Lorian Schweikert, as well as Kate Thomas and Sarah Solie for comments on earlier versions of this manuscript.

Glossary

Cycles per degree (cpd)
a measure of visual acuity; the number of black and white stripe pairs that an organism can discriminate within a single degree of visual angle.
Minimum resolvable angle
(αmin) another measure of visual acuity; the angular width of the narrowest black and white stripe pair that can be discerned. When given in degrees, its inverse is cpd.
Visual acuity
the ability of a visual system to resolve static spatial detail.

References (96)

  • D. Northmore et al.

    Sensitivity and acuity of the goldfish

    Vision Res.

    (1979)
  • R.L. Rutowski

    Visual acuity and sensitivity increase allometrically with body size in butterflies

    Arthropod Struct. Dev.

    (2009)
  • J.W. Merry

    The eyes of a patrolling butterfly: visual field and eye structure in the orange sulphur, Colias eurytheme (Lepidoptera, Pieridae)

    J. Insect Physiol.

    (2006)
  • R.A. Johnstone

    The evolution of animal signals

  • J.A. Endler

    Evolutionary implications of the interaction between animal signals and the environment

  • J. Maynard Smith et al.

    Animal Signals

    (2003)
  • T.W. Cronin

    Visual Ecology

    (2014)
  • M.F. Land

    Visual acuity in insects

    Annu. Rev. Entomol.

    (1997)
  • M.F. Land et al.

    Animal Eyes

    (2002)
  • J. Zeil

    Sexual dimorphism in the visual system of flies: the compound eyes and neural superposition in Bibionidae (Diptera)

    J. Comp. Physiol. A

    (1983)
  • J. Zeil et al.

    The visual ecology of fiddler crabs

    J. Comp. Physiol. A

    (2006)
  • Hughes, A. (1977) The topography of vision in mammals of contrasting lifestyle: comparative optics and retinal...
  • T.J. Lisney et al.

    Retinal ganglion cell distribution and spatial resolving power in elasmobranchs

    Brain Behav. Evol.

    (2008)
  • S. Johnsen

    The Optics of Life

    (2012)
  • E.J. Warrant et al.

    Vision in the deep sea

    Biol. Rev. Camb. Philos. Soc.

    (2004)
  • R.A. Kiltie

    Scaling of visual acuity with body size in mammals and birds

    Funct. Ecol.

    (2000)
  • C.C. Veilleux et al.

    Visual acuity in mammals: effects of eye size and ecology

    Brain Behav. Evol.

    (2014)
  • E.M. Caves

    Visual acuity in ray-finned fishes correlates with eye size and habitat

    J. Exp. Biol.

    (2017)
  • C. Arrese

    Retinal structure and visual acuity in a polyprotodont marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata)

    Brain Behav. Evol.

    (1999)
  • C. Arrese

    Visual system in a diurnal marsupial, the numbat (Myrmecobius fasicatus): retinal organization, visual acuity, and visual fields

    Brain Behav. Evol.

    (2000)
  • C. Arrese

    Visual capabilities in a crepuscular marsupial, the honey possum (Tarsipes rostratus): a visual approach to ecology

    J. Zool.

    (2002)
  • C.C. Veilleux et al.

    Visual acuity in the cathemeral strepsirrhine Eulemur macaco flavifrons

    Am. J. Primatol.

    (2009)
  • M.I. Hall et al.

    Eye shape and activity pattern in birds

    J. Zool.

    (2007)
  • K. Kirschfeld

    The resolution of lens and compound eyes

  • S.P. Collin et al.

    Retinal topography in reef teleosts. I. Some species with well-developed areae but poorly-developed streaks

    Brain Behav. Evol.

    (1988)
  • S.P. Collin et al.

    Retinal topography in reef teleosts II. Some species with prominent horizontal streaks and high-density areae

    Brain Behav. Evol.

    (1988)
  • M.F. Land

    Visual acuity in insects

    Annu. Rev. Entomol.

    (1997)
  • L. Litherland et al.

    Comparative visual function in elasmobranchs: spatial arrangement and ecological correlates of photoreceptor and ganglion cell distributions

    Vis. Neurosci.

    (2008)
  • A.P. Dobberfuhl

    Visual acuity, environmental complexity, and social organization in African cichlid fishes

    Behav. Neurosci.

    (2005)
  • E.M. Caves et al.

    AcuityView: an R package for portraying the effects of visual acuity on scenes observed by an animal

    Methods Ecol. Evol.

    (2017)
  • M. Stevens

    Predator perception and the interrelation between different forms of protective coloration

    Proc. Biol. Sci.

    (2007)
  • I.M. Côté

    Evolution and ecology of cleaning symbioses in the sea

    Oceanogr. Mar. Biol.

    (2000)
  • E.M. Caves

    Spectral sensitivity, spatial resolution, and temporal resolution and their implications for conspecific signalling in cleaner shrimp

    J. Exp. Biol.

    (2016)
  • H. Cott

    Adaptive Coloration in Animals

    (1957)
  • G. Ruxton

    Avoiding Attack: The Evolutionary Ecology of Crypsis, Warning Signals, and Mimicry

    (2004)
  • S.D. Finkbeiner

    Warning signals are seductive: relative contributions of color and pattern to predator avoidance and mate attraction in Heliconius butterflies

    Evolution

    (2014)
  • M.D. Bowers

    Bird predation as a selective agent in a butterfly population

    Evolution

    (1985)
  • M.S. Livingstone

    Is it warm? Is it real? Or just low spatial frequency?

    Science

    (2000)
  • Cited by (0)

    View full text