624 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



remained consciously aloof from consideration of habitats, and geographic dis- 

 tribution was cited as if it were a matter of occurrence in space independent even 

 of altitude. The characteristics that distinguish species were referred to as "use- 

 ful" if they were useful to the taxonomist in his discrimination of systematic 

 groups. 



The realization that species and subspecies had to be revalued and redescribed 

 in terms of the general environments and special habitat niches in which they 

 occur came first from the side of popular natural history (e.g., Brehm's Tierlehen) . 

 Laboratory studies of the reactions and tolerances of animals afford another of the 

 roots of animal ecology. A pioneer paper in tlie United States was based by 

 Alexander G. Ruthven on field studies in the American Southwest in 1906 (Ruth- 

 ven, 1907) , in which he was obviously influenced by C. C. Adams. Since that date 

 there has been increasing interest in the observation of the biotic and physical 

 environments in which amphibians and reptiles live, how they meet the adverse 

 factors in their surroundings, and, in general, how they "behave" in relation 

 to them. The importance of environmental observation to a definitive taxonomy 

 is especially illustrated by the work of Henry S. Fitch on the garter snakes of 

 the Pacific region (1940). Ecological observation, of course, stands on its own 

 feet independent of its significance to taxonomy, and becomes increasingly inde- 

 pendent as the taxonomy becomes mature, and thus a sound foundation for 

 ecology. Ecology involves a vast variety of subsciences from physiography, mete- 

 orology, and chemistry to the complex of biotic relations, and more particularly 

 for herpetology, the relation of animal life to its plant matrix. Finally, since 

 animal behavior rests on the interaction of internal physiology and stimulus from 

 the environment, the ecology of animals must particularly include their behavior, 

 the study of which tends to be distinguished as the separate science of animal 

 behavior. Physiological investigation in herpetological ecology is to be discerned 

 in the continuing studies of Raymond B. Cowles (b. 1896) and of his student and 

 colleague, C. M. Bogert, on the temperatures of amphibians and reptiles in rela- 

 tion to the temperature range of their environment. The sharpness of limitation 

 to specific habitat niches reflects the long evolution of the reptile group; it is illus- 

 trated by the rock-crevice habitat of such lizards as Sauromalus in the American 

 Southwest, and especially by Xantusia henshawi and arizonae, which live under 

 the loose exfoliating rockflakes of rounded granite boulders. Courtship behavior, 

 with the frequent correlation of the spacing of individual animals of breeding 

 groups into territories, is an important fleld of study pioneered in herpetology by 

 G. K. Noble (Noble and Bradley, 1933). The sub.ject of "Home Ranges and Wan- 

 derings of Snakes" {Copeia, 1947, pp. 127-136) is summarized by William F. 

 Stickel and James B. Cope. That the populations of amphibians and reptiles are 

 often vast has long been known from their breeding aggregations. Actual meas- 

 urements of population density are extraordinarily few. Pioneering studies in 

 this direction rest on the techniques of marking individuals by tagging, toe- 

 clipping, scale-clipping, or tattooing, pioneered by F. N. Blanchard in 1933. 

 Cagle's paper in 1950, "The Life History of the Slider Turtle, Pseudemys scripta 

 troostii (Holbrook)" in Ecological Monographs (20:31-54, 18 figs.) summarizes 

 ten years of work in this field. The study of distribution depends directly on 

 examination of the present environment and on speculations regarding the past 

 changes in environment, i.e., on ecology and paleoecology. Studies on defensive 



