Journal of Comparative Physiology B

, Volume 158, Issue 2, pp 213–221

Consequences of skin color and fur properties for solar heat gain and ultraviolet irradiance in two mammals

  • Glenn E. Walsberg
Article

Summary

In animals with fur or feather coats, heat gain from solar radiation is a function of coat optical, structural, and insulative characteristics, as well as skin color and the optical properties of individual hairs or feathers. In this analysis, I explore the roles of these factors in determining solar heat gain in two desert rodents (the Harris antelope squirrel,Ammospermophilus harrisi, and the round-tailed ground squirrel,Spermophilus tereticaudus). Both species are characterized by black dorsal skin, though they contrast markedly in their general coat thickness and structure. Results demonstrate that changes in coat structure and hair optics can produce differences of up to 40% in solar heat gain between animals of similar color. This analysis also confirms that the model of Walsberg et al. (1978) accurately predicts radiative heat loads within about 5% in most cases. Simulations using this model indicate that dark skin coloration increases solar heat gain by ≤5%. However, dark skin significantly reduces ultraviolet transmission to levels about one-sixth of those of the lighter ventral skin.

Symbols and abbreviations: (unless noted, all radiation relations refer to total solar radiation)

α

absorptivity of individual hairs

αC

absorptivity of the coat

β

backward scattering coefficient [‘reflectivity’] of individual hairs

βC

reflectivity of coat

βS

reflectivity of skin

τ

forward scattering coefficient [‘transmissivity’] of individual hairs

τC

transmissivity of coat

τS

transmissivity of the skin

\(\tau _{\begin{array}{*{20}c} {C + S} \\ {UV} \\ \end{array} } \)

transmissivity of the coat and skin

\(\tau _{\begin{array}{*{20}c} C \\ {UV} \\ \end{array} } \)

transmissivity of the coat to ultraviolet radiation

τS

transmissivity of the skin to ultraviolet radiation

η

[(1 − τ)2 − δ2]

hC

coat thermal conductance [W/m2-°C]

hE

coat surface-to-environment thermal conductance [W/m2-°C]

I

probability per unit coat depth that a ray will be intercepted by a hair [m−1]

K

volumetric specific heat of air at 20°C [1200 J/m3-°C]

lC

coat thickness [m]

lH

hair length [m]

d

hair diameter [m]

n

hair density per unit skin area (m−2]

QABS

heat load on animal's skin from solar radiation [W/m2]

QI

solar irradiance at coat surface [W/m2]

rE

external resistance to convective and radiative heat transfer [s/m]

rC

coat thermal resistance [s/m]

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Davis LB, Birkebak RC (1975) Convective energy transfer in fur. In: Gates DM, Schmerl RB (eds) Perspectives in biophysical ecology. Springer, Berlin Heidelberg New York, pp 525–548Google Scholar
  2. Campbell GS (1977) An introduction to environmental biophysics. Springer, Berlin Heidelberg New YorkGoogle Scholar
  3. Campbell GS, McArthur AJ, Monteith JL (1980) Windspeed dependence of heat and mass transfer through coats and clothing. Boundary-Layer Meteorol 18:485–493Google Scholar
  4. Cena K, Clark JA (1973) Thermal radiation from animal coats. Phys Med Biol 18:432–443Google Scholar
  5. Cena K, Monteith JL (1975) Transfer processes in animal coats. I. Radiative transfer. Proc R Soc Lond [B] 188:395–411Google Scholar
  6. Fitzpatrick TB, Pathak MA, Harber LC, Seiji M, Kukita A (1972) Sunlight and man. University of Tokyo Press, TokyoGoogle Scholar
  7. Grojean RE, Sousa JA, Henry MC (1980) Utilization of solar radiation by polar animals: an optical model for pelts. Appl Optics 19:339–346Google Scholar
  8. Hamilton WJ (1973) Life's color code. McGraw-Hill, New YorkGoogle Scholar
  9. Hinze HO (1959) Turbulence. An introduction to its mechanism and theory. McGraw-Hill, New YorkGoogle Scholar
  10. Hutchinson JCD, Brown GB (1969) Penetrance of cattle coats by radiation. J Appl Physiol 26:454–464Google Scholar
  11. Idso SB (1971) A simple technique for the calibration of long-wave radiation probes. Agric Meteorol 8:235–243Google Scholar
  12. Kovarik M (1964) Flow of heat in an irradiated protective cover. Nature 201:1085–1087Google Scholar
  13. Lentz CP, Hart JS (1960) The effect of wind and moisture on heat loss through the fur of newborn caribou. Can J Zool 38:679–688Google Scholar
  14. Monteith JL (1975) Principles of environmental biophysics. Arnold, LondonGoogle Scholar
  15. Øritsland NA (1970) Energetic significance of absorption of solar radiation in polar homeotherms. In: Holgate MW (ed) Antarctic ecology, vol 1. Academic Press, New York, pp 464–470Google Scholar
  16. Porter WP (1967) Solar radiation through the living body walls of vertebrates with emphasis on desert reptiles. Ecol Monogr 87:273–296Google Scholar
  17. Tanner CB (1963) Basic instrumentation and measurements for plant environment and micrometeorology. Univ Wisconsin Dept Soil Sci Bull 6:S1-S15Google Scholar
  18. Treager RT (1965) Hair density, wind speed, and heat loss in mammals. J Appl Physiol 20:796–801Google Scholar
  19. Walsberg GE (1983) Coat color and solar heat gain in animals. Bioscience 33:88–91Google Scholar
  20. Walsberg GE, Campbell GS, King JR (1978) Animal coat color and radiative heat gain: a re-evaluation. J Comp Physiol 126:211–222Google Scholar

Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Glenn E. Walsberg
    • 1
  1. 1.Department of ZoologyArizona State UniversityTempeUSA

Personalised recommendations