Acta Biotheoretica

, Volume 34, Issue 2–4, pp 165–174 | Cite as

The legs of ostriches (Struthio) and moas (Pachyornis)

  • R. McNeill Alexander
Article

Abstract

Ostriches were filmed running at maximum speed, and forces on the feet were calculated. Measurements were made of the principal structures in the legs of an ostrich. Hence peak stresses in muscles, tendons and bones were calculated. They lay within the range of stresses calculated for strenuous activities of other vertebrates. The ostrich makes substantial savings of energy in running, by elastic storage in stretched tendons.

Pachyornis was a flightless bird, much heavier than ostriches and with massively thick leg bones. These bones are shorter than predicted for its estimated body mass, by extrapolation from allometric equations for flying birds. An attempt is made to calculate the stresses that acted in the leg bones in running, for all possible patterns of leg movement. The stresses were probably rather low, unless Pachyornis was capable of running fast. It is argued that the optimum factor of safety for moo leg bones may have been exceptionally high, as a consequence of the absence of predators.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Alexander, R.McN. (1981). Factors of safety in the structure of animals. Sci Prog Oxford 67: 109–130.Google Scholar
  2. 2.
    Alexander, R.McN. (1983). Allometry of leg bones of moas (Dinornithes) and other birds.- J Zool London 200: 215–231.Google Scholar
  3. 3.
    Alexander, R.McN. (1983). On the massive legs of a moa (Pachyornis elephantopus, Dinornithes).- J Zool London 201: 363–376.Google Scholar
  4. 4.
    Alexander, R.McN. (1983). Animal mechanics. 2nd ed- Oxford: Blackwell, x + 301 p.Google Scholar
  5. 5.
    Alexander, R.McN., and Bennet-Clark, H.C. (1977). Storage of elastic strain energy in muscle and other tissues.- Nature London 265: 114–117.Google Scholar
  6. 6.
    Alexander, R.McN., Maloiy, G.M.O., Njau, R., and Jayis, A.S. (1979). Mechanics of running of the ostrich (Struthio camelus).- J Zool London 187: 169–178.Google Scholar
  7. 7.
    Alexander, R.McN., and Jayes, A.S. (1983). A dynamic similarity hypothesis for the gaits of quadrupedal mammals.- J Zool London 201: 135–152.Google Scholar
  8. 8.
    Biewener, A.A., Thomason, J., Goodship, A., and Lanyon, L.E. (1983). Bone stress in the horse fore limb during locomotion at different gaits: a comparison of two experimental methods.- J Biomechan 16: 565–576.Google Scholar
  9. 9.
    Cavagna, G.A., Heglund, N.C., and Taylor, C.R. (1977). Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure.- Am J Physiol 223: R243-R261.Google Scholar
  10. 10.
    Heglund, N.C., Cavagna, G.A., and Taylor, C.R. (1982). Energetics and mechanics of terrestrial locomotion. III. Energy changes of the centre of mass as a function of speed and body size in birds and mammals.- J exp Biol 97: 41–56.Google Scholar
  11. 11.
    Jayes, A.S., and Alexander, R.McN. (1982). Estimates of mechanical stresses in leg muscles of galloping greyhounds (Canis familiaris).- J Zool London 198: 315–328.Google Scholar
  12. 12.
    Ker, R.F. (1981). Dynamic tensile properties of the plantaris tendon of sheep (Ovis aries).- J exp Biol 93: 283–302.Google Scholar

Copyright information

© Martinus Nijhoff/Dr W. Junk Publishers 1985

Authors and Affiliations

  • R. McNeill Alexander
    • 1
  1. 1.Department of Pure and Applied ZoologyUniversity of LeedsLeedsEngland

Personalised recommendations