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<br />7. E. Corle, The Glfa (Univ. of Nebraska
<br />Press, Llacoln, 1951).
<br />8. C. D. Vanicek, theses, Utah State University,
<br />1967.
<br />9. R. R. Millet, Nat. Parks Mag. 37, 4 (1963).
<br />10. W. J. Koster, Southwest Naturalist S, 174
<br />(1960).
<br />11. R R Miller, Copeia 1963.1 (1963).
<br />12. C. L. Hubbs and R. R. Miller, Papers Mich.
<br />Acad. Scl. 38, 207 (1953).
<br />13. W. F. Sigler and R R MtUer, Fisher of
<br />Utah (Utah Stato Game and Flsh Depart-
<br />ment, Salt Lake City, 1963).
<br />14. W. H. Dill, Calif• Flsh Gams 30, 109 (1944);
<br />O. L. Wallis, Trans, Amer. Fish. Soc. 80,
<br />84 (1951).
<br />15. R. R. Miller, Papers Mieh. Acad. Sci. 40,
<br />125 (1955).
<br />16. W. L. Minckley sad N. T. Alger, P/areau,
<br />In press.
<br />17. W, L. Minckley, In AAAS Committes an
<br />Desert and Arid Lands Research Contrib. No.
<br />8 (1965), p. 48.
<br />18. B. A. Branson et al., Southwestern Naturalist
<br />11, 300 (1966).
<br />19. J. K. Andersen, personal communication.
<br />20. N. Wood, personal communication
<br />21. P. A. Douglas, Calif. Fish Game 38, 149
<br />(1952).
<br />23. Personal observations; personal communica-
<br />tions from personnel of tite Arlmna Game
<br />and Fish Department.
<br />23. R R Miller and C. L. Hubbs. Univ. Mich.
<br />Museum Zool. Misc. Pub. 115, 1 (1960).
<br />24. W. O. Bradley and J. E. Deacon, Desert
<br />Res. Inst. Univ. Nevado (Las Vegas) Prs-
<br />Print No. 9 (1965), p. I.
<br />25. Personal eommunlcatlon from U.S. Bureau
<br />of Reclamation, Boulder City Office.
<br />26. W. E. Barber and W. L. Minckley, South-
<br />western Naturalist 11, 313 (1966),
<br />27. W. J. Koster, Guide to the Fishes of New
<br />Mexlrn (Univ. of Ncw Mexico ,Press, Al-
<br />buquerque, 1957)..
<br />28. C. L. Hubbs and R R. Miller, Unly. Mich.
<br />Museum Zool. Occasional Paper No. 433
<br />(1941), p. 1.
<br />29. J. R. Hastings, J. Arizona Acad, Scl. 1, fi0
<br />(1959); J. R. Hastings and R. M. Turner,
<br />The Changing Mife (Univ. of Arizona Press,
<br />Tucson, 1%5).
<br />30. O. 5. Myers, Tropical Fish Hobbyist 1965,
<br />(Jan 1965), p. 31.
<br />31. J. E. Deacon, C. Hubbs. B. J. Zahuraaec,
<br />Copeia 1964, 384 (1964).
<br />32. G. T. Malmberg, U.S.. Geol. Surv. Water
<br />SuPPI. Paper 1832 (1%7), p. 1.
<br />33. C. L. Hubbs and R. R Miller, Unlv. Mleh.
<br />Museum Zool. Occasional Paper No. 507
<br />(]948), p. 1.
<br />34. I. LaRivers, Flsh and Fisheries of Nevada
<br />(Nevada Game and Fish Commission, Reno,
<br />1962).
<br />35. B. L. Wilson, J. E. Deacon, W. G. Bradley,
<br />Trans. California-Nevada Sect. Wild111e Soc.
<br />19.66, 12 (1966).
<br />36. T. A. Eakin, U.S. Geol. Surv. Ground-Water
<br />Res: Reconnaissance Ser. 25, 1 (1964).
<br />Population Regulation and
<br />Genetic Feedback
<br />Evolution provides foundation for control of
<br />herbivore, parasite, and predator numbers in nature.
<br />David Pimentel
<br />Although within a relatively short
<br />period man has learned how to put him-
<br />self into space, he still is not certain
<br />how the numbers of a single plant or
<br />animal population are naturally con-
<br />trolled. Aspects of this problem have
<br />been investigated since Aristotle's time,
<br />they were given important consideration
<br />in Darwin's Origin of Species, and yet
<br />the unknowns far outweigh the discov-
<br />eries. If we knew more about natural
<br />regulation of population, we would be
<br />in a better position to devise more effec-
<br />tive and safer means of control for im-
<br />portant populations of plant and animal
<br />pests. We Wright also be better able. to
<br />limit the growth of human populations,
<br />although that problem is exceeding)}~
<br />complex because of the social actin hies
<br />and nature of man.
<br />Population Characteristics
<br />Before considering how populations
<br />in nature are regulated, we should re-
<br />view various characteristics of animals
<br />and plants-as individuals and as popu-
<br />lations. Do populations of animals in
<br />nature fluctuate severely or are they
<br />relatively constant? Stability and con-
<br />stancy have been proposed as charac-
<br />teristics of natural populations. Speak-
<br />ing about birds, Lack (1) says, "of the
<br />species which are familiar to us in
<br />England today, most were familiar to
<br />our Victoria^ great-grandparents and
<br />many to our medieval ancestors; and
<br />the known changes in numbers are
<br />largely attributable to man." He con-
<br />tinues, "All the available censuses con-
<br />firm the view that, where conditions are
<br />1432
<br />.. _--
<br />37. F. B. Sumner and U. Lanham, Blof. BuII. 8
<br />313 (1942); C. Hubbs and W. F. Het[lt
<br />Southwestern Naturalist 9, 245 (1964);
<br />Hubbs, R. C. Baird, J. W. Gerald, Amr
<br />Midland Naturalist 77, 104 (1967); J. E. lie
<br />con and B. L. Wilson, Southwestern Nahero
<br />ist 12, 31 (1967).
<br />38. C. Hubbs arM H. J. Broderick, Southrveste.
<br />Naturalist 8, d6 (1%3).
<br />39. D. Nyqufst, thesis, University of Nevad
<br />(1%3).
<br />40. W. L. Minckley and L. H. Carufel, Sortt.
<br />western Naturalist 12, 291 (1%7).
<br />41. G. A. Waring, U.S. Geol. Surv. Water Su
<br />ply Paper 450 (1920), p. 51.
<br />42. G. B. Maxey and T. W. Robinson, U.
<br />Geol. Surv. Water Res. Btdl. 6, 1 (1947),
<br />43. Personal communication from Nevada, Sta
<br />Engineer, Reno. t'.
<br />44. The support of the followl6~egencIes, to 0
<br />or both of its, is gratefully acknowledge
<br />Desert Research Institute, University of
<br />vada; Faculty Research Committee, Arim~
<br />State University; The Nature Conservane
<br />Sports Fishing Institute; U.S. Bureau
<br />Sports Fisheries and Wildlife; U.S. Natior.
<br />Park Service; and National Science Fours:
<br />tion. Permits and information were i .
<br />and supplied by numerous game ands
<br />departments. We especially thank our ..
<br />dents and colleagues for assistance ir.
<br />field and the laboratory, and Drs., <:.
<br />Hubbs and R. R. Miller for providing rsa
<br />data from their early and recent resear~'".
<br />fishes of the American Southwest.
<br />not disturbed, birds fluctuate in nun
<br />hers between very restricted litni
<br />Thus, among the populations consider
<br />above, the highest total recorded w
<br />usually between two and six times, rat
<br />ly as much as ten times, the Lowe:
<br />This is a negligible range compared.wi
<br />what a geometric rate of increase wou
<br />allow." Discussing the stability in at
<br />mal populations in general, MacFady~
<br />(2) writes: "it is generally agreed th
<br />the same species are usually found
<br />the same habitats at the same seaso
<br />for many years in succession, and th
<br />they occur in numbers which aze of f
<br />same order of magnitude."
<br />Further evidence for the thesis t1,
<br />species populations are relatively co
<br />stant is found in a study of the Chang
<br />in the fauna of Ontario, Canada (.
<br />When Snyder (~ evaluated the bi
<br />fauna, he found that, over a period
<br />about 70 years, two species became e
<br />tinct, 23 species increased is numb
<br />and six species decreased in numb
<br />This represents a total change of onl}
<br />percent of 351 bird species found
<br />Ontario (S) and agrees favorably w
<br />an 11-percent change (~ for 149 spec
<br />of birds over a 50-year period in F
<br />land. These data suggest that there
<br />relative constancy in the abundance
<br />species populations. The word."relati~
<br />must be emphasized because changes
<br />numbers must be related to a sped
<br />real potential for fluctuations; to pa
<br />The author is chairman of the departmen[
<br />en[omology and limnology, Cornell Univer
<br />Ithaca, New York.
<br />SCIENCE. VOL.
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