Archives of The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 32, Number 1;   January, 2005

Gopherus agassizi (Cooper, 1863) - Desert Tortoise

by Edward O. Moll

Adjunct Professor
School of Renewable Natural Resources University of Arizona

"To see a tortoise with wrinkled neck and solemn eyes, moving like an animated rock, is an essential part of the experience of the desert. The removal of even a single adult extinguishes a presence that was meant to persist for years to come and snuffs out a prehistoric spark of life in a spartan environment where life so hard-won, should be celebrated." John Alcock from Desert Spring.

My first encounter with desert tortoise dens occurred in November of 1963 on the Beaver Dam Slope in the Mojave Desert of extreme southwestern Utah, a couple of miles north of the Arizona Border. As a new graduate student at the University of Utah, fresh from the Midwest, I wanted to see as much of my new environment as I could before beginning school in earnest. Being a turtle enthusiast and having read the celebrated and much-cited 1948 monograph on the desert tortoise by Angus M. Woodbury and Ross Hardy, their study area was one of the first places I set out to visit. While I saw no tortoises that day, I did find a number of what I presumed to be their winter dens. Woodbury and Hardy reported that these dens were dug into gravel banks to depths of 2 to 10 meters, housed up to 23 individuals, and were utilized from November to March. Upon leaving the dens in the spring, they disperse into the surrounding countryside. As long as temperatures remain comfortable, they might not seek more shelter than a convenient creosote bush or shrub. However, with the scorching temperatures of summer, they again become troglodytes, utilizing impermanent holes of 1 - 1.5 meters depth that tend to accommodate individuals only.

In January, 2000, almost four decades later, I had the opportunity to see Desert Tortoise wintering dens of quite a different nature. Roy Averill-Murray, then tortoise honcho for the Arizona Game and Fish Department, invited me to accompany him to his study area for Sonoran Desert tortoises near Sugar Loaf Mountain in the T onto National Forest of Maricopa County. As it was winter, I envisioned finding tortoises deeply ensconced in lengthy burrows far below the substrate. My expectations could nor have been further from the truth. We located 13 tortoises (or I should say tortoise backsides) that day. Each was located either barely inside a burrow with its bum even with the entrance or hanging outside a bit. One tortoise was even found - fully exposed under a nearby bush. Six others did occupy deeper burrows or rock piles, bur these were definitely in the minority. I drove back to Tucson somewhat baffled. How could there be such major behavioral differences between two conspecific populations?

Recently in the course of reading chapters by Thomas Van Devender in The Sonoran Desert Tortoise compendium, I gained some insight into this question. The Mojave tortoise population, like the desert itself, has appeared relatively recently on the scale of geological time (ca. 2.4 million years ago). Ancestors of the modern desert tortoise originally moved into the Southwest from the tropics. Elaborate burrows were not required in their former environment (except for the more vulnerable juveniles) and, as warmer than present climates prevailed during the late Miocene and Pliocene, there was little selection for such traits in adults. Shallow dens were adequate to escape the heat of the summer and mild winter temperatures. During these warm periods, tortoises extended their range into the area of the present Mojave Desert. With the advent of the Pleistocene, climatic conditions changed radically for these northern outliers, which had become somewhat isolated. It became cooler, most rainfall fell only in the winter, and a diverse spring annual flora evolved in the region. Presumably the majority of tortoises in the region died off, but those that survived carried traits allowing them to be active at cooler temperatures, to dig deeper, more elaborate burrows, and to heavily exploit the spring annuals during the short favorable season before going into extended dormancy. Thus, today we have the Sonoran tortoise and the Mojave tortoise, two look-alikes with markedly different behavior.

The Desert Tortoise owes its specific epithet to two pioneer naturalists. James Graham Cooper (1830 - 1902), the collector and describer of the type series, and Louis Adolphe Agassiz (1807 - 1873), who became the namesake of these venerable chelonians. James, the son of William Cooper, a distinguished naturalist from New York, made his name in natural history through work in western US. Like so many naturalists of the pioneer west in the 1850s, Cooper acted as both surgeon and naturalist for several expeditions in the western United States (e.g., I. I. Steven's Pacific railroad survey, F. Bryan's Wagon Road Expedition), positions that he obtained with the aid of Spencer Baird, Asst. Secretary of the Smithsonian Institution, a friend of his father. Due to respiratory problems, Cooper spent much of his career in the favorable environs along the West Coast. He was a general naturalist but is best known for his studies of ornithology and conchology. The Cooper Ornithological Society was named in his honor.

In late 1860, Cooper took an assignment as surgeon for Fort Mojave on the east bank of the Colorado River in what was then New Mexico Territory. This gig proved to be short-lived. Due to the onset of the Civil War, troops were needed in the East and on May 28, 1861, Fort Mojave was abandoned. Cooper's short stay at Fort Mojave was nevertheless productive as he left with three new species - a tiny owl, a warbler, and three specimens of a desert tortoise.

Cooper described the three species together in the 1863 Proceedings of the California Academy of Sciences. The (elf) owl was named Athene (Micrachene) whitneyi after Josiah Dwight Whitney, who was in the process of organizing the California Geological Survey and for whom Cooper had agreed to collect specimens while at Fort Mojave. Whitney had indicated that he was looking to hire a zoologist for the new survey and this may have influenced Cooper's choice of patronyms. He wrote Baird that he had considered naming the tortoise after Whitney bur decided it might be a better compliment to name "the bird of wisdom instead of the emblem of slowness" after him (it apparently worked as he got the job). He named the warbler Helminthophaga (Vermivora) luciae in honor of "the interesting little daughter of my kind friend, Prof. S. F. Baird." In a letter to Baird about the naming of Lucy's warbler in honor of his 13 year old daughter, Cooper wrote: "I hope she may never have to live in such a country as the bird inhabits, but if she does, her presence, like the birds, would go far to make a garden of the desert."

Now the question remained of what patronym would be suitable for the tortoise. Cooper decided upon Xerobates (Gopherus) agassizii with the following dedication: "I take the liberty of naming this fine tortoise after the celebrated Zoologist, whose work on the development, anatomy and classification of American Turtles (Contrib. to Nat. Hist. of U. S.) leaves nothing to be desired in these particulars. We may hope before long to see his descriptions of the genera and species, of which he has been engaged for several years, and which, like the tortoise itself, though slow in coming, will doubtless prove of solid worth and durable quality."

Agassiz, though one of the foremost biologists of his day, was noted for biting off more than he could chew. For every project that he completed, he started a dozen more. He was continually borrowing large numbers of natural history specimens from the Smithsonian that would never be examined or returned. Particularly in his later life, Agassiz lost the ability to focus on specific projects, as his fertile mind was continually creating ever more exciting ones. However, I am getting ahead of myself. In order to understand how Louis Agassiz became the best known natural history scientist of the New World, we must go back to his roots in Switzerland.

John Louis Rodolphe Agassiz was born the son of a minister on May 28, 1807 in Montier, Switzerland. He was educated in universities in Switzerland and Germany as a physician but his great passion was always for what his father considered to be the less practical side of biology: i.e., natural history. Agassiz got his PhD degree from the University of Erlangen in 1829 and then to please his parents continued on to receive his MD at the University of Munich in 1830. Freed of this parental obligation, he immediately headed for Paris to study anatomy under Cuvier, the most famous anatomist and taxonomist of the day. Both Agassiz and Cuvier had been working independently on a compendium of fossil fishes. While this could have proven a source of friction between the young student and the old master, Cuvier was so impressed by Agassiz' work that he turned over his own notes and drawings to him for the project. Although Cuvier died in 1832, only 6 months after coming to work with him, Agassiz became his intellectual heir, promoting Cuvier's ideas on catastrophism (an alternative to evolution) and taxonomy through-out his career.

Agassiz also impressed another highly influential scientist and peregrinator of the day, Alexander von Humboldt. Humboldt supplanted Cuvier as his mentor serving as patron, advisor, and protector. He even contributed 1000 francs toward the publication of Agassiz's work on fossil fish, Recherces sur les Poissons Fossiles, which appeared in five volumes from 1833 to 1844, firmly establishing his reputation as a scientist. Agassiz began his academic career in 1832 by accepting a professorship at the College of Neuchâtel in Switzerland. Never one to complete one project before starring another, Agassiz became interested in glaciology while still completing his works on fossil fish. He published Etude sur les glaciers in 1840, a book proposing the theory that the world had experienced a great ice age replete with continent-sized glaciers.

As his celebrity continued to spiral upward in Europe, Agassiz decided to conquer the new world as well (but also to recoup financial losses from publishing ventures). He landed in Boston in 1846 to do a series of public lectures. A charming and persuasive speaker, Agassiz was always a great draw and his lectures were extremely popular with the American public. Despite speaking on advanced scientific topics, he had the ability to make even abstruse subjects both comprehensible and exciting to nonscientists. Recognizing his potential as a renowned teacher and promoter of Science, Harvard College offered him a professorship in 1848 which Agassiz accepted and there remained for the rest of his career.

Despite the difficulty in finishing what he starred, Agassiz made a number of significant contributions to science during his North American career. In 1850, he was elected president of the American Association for Advancement of Science, indicating his early popularity and respect among the scientists of his new home. However, one of his greatest joys was popularizing and interpreting natural science to his new countrymen and much of his U.S. reputation was made through presenting public lectures. In 1855 he went a step further and announced his plan to publish a 10 volume study (Contributions to the Natural History of the United States), financed by public subscriptions that would cover the complete scope of American natural history. Only four volumes were published during his life time (a fifth posthumously). Volumes 1 and 2 contain the well-known "Essay on Classification" (demonstrating his continued loyalty to the ideas of Cuvier), along with his most significant herpetological contributions, a treatise on the biology and classification of North American turtles including exceptional drawings of juvenile turtles, eggs, and their embryology. A highly successful fund-raiser throughout his career, Agassiz succeeded in financing the building of the Museum of Comparative Zoology on the Harvard campus to house his rapidly growing collection in 1859. Always campaigning for support of science in his new homeland, he with several colleagues were instrumental in founding the National Academy of Sciences.

On the negative side, Agassiz tended to be quite rigid in his beliefs and, upon once accepting an idea, rarely could be swayed by new information. Darwin's theory of evolution is a case in point. Agassiz saw the Divine Plan of God in nature and could not accept any theory that did not invoke divine design. He was one of the last reputable scientists to continue to dismiss evolutionary theory outright. Instead he continued to postulate the idea of catastrophism as espoused by his mentor Cuvier. Cuvier publicly debated and soundly defeated Geoffroy Saint Hillaire concerning the radical idea that species were not fixed but could change with time. Again in the Cuvier tradition, Agassiz eschewed debate in scientific journals and forums and took his criticism of Darwinian evolution to the public directly in the form of lectures and popular magazine articles. Not only were Agassiz' views on evolution challenged by his scientific colleagues (especially Asa Gray, the renowned Harvard botanist) but, much to his chagrin, also by most of his students, including his son Alexander, who succeeded his father as Director of the Museum of Comparative Zoology.

Another character defect plaguing Agassiz throughout his academic career was an inability to work with others as equals. In this regard he had several clashes over his alleged adopting of work by his assistants and students with little or no recognition. Some of these accusations led to public scandals. Early in his American career, Desor Clark, his longtime secretary, accused Agassiz of pirating embryological research from him, along with other morals-related accusations. However, Agassiz fought these accusations in private court and was eventually vindicated. Later following publication of Volume 4 of his "Contributions" another assistant, H. James Clark, whose name had appeared in the acknowledgments but not on the title pages, complained that, of the latter three volumes, he had written most of the second and third, "and so much of the fourth that he was unable to determine what had actually been written by Agassiz." In the early 1860s a number of students in the museum clashed with Agassiz over his authoritarian treatment and a number left the fold. Agassiz was typically vindictive toward any person that challenged his authority. One well known instance concerned Charles Girard, a Swiss student that had followed Agassiz to America. Girard later jumped ship and accepted a position as assistant to Spencer Baird at the Smithsonian. Agassiz was furious with both Girard and Baird and henceforth, whenever they would coauthor any scientific work, it would be roundly criticized by Agassiz. When Baird was brought up for membership in the National Academy of Science, Agassiz attempted to use his influence to have him rejected. However, he underestimated Baird's support and when the vote was counted Spencer Baird had become a member of the Academy.

Due to these and similar events, the last decade of Agassiz' life was marked by professional isolation. However, he never lost his popularity with the everyday American and, when he died of a cerebral hemorrhage in 1873, Agassiz was considered by his public the greatest of America's men of science. Despite his faults, Agassiz left a great legacy of scientific theory, a celebrated museum, and of course, a deliberate, slow-moving, but lovable western tortoise to carry his name ever into the future.

Acknowledgments: Thanks to Roy Averill Murray for reading portions of the manuscript and for supplying information on our winter trip to view tortoise dens.

SOURCES:
Adler, Kraig A. 1989. Herpetologists of the past Pp. 5-41 in K. A. Adler (ed.). Contributions to the history of herpetology. No.5. Society For The Study Of Amphibians And Reptiles.
Coan, Eugene. 1981. James Graham Cooper, pioneer western naturalist. A northwest naturalist book. University Press of Idaho.
Cooper, Jarnes G. 1861. New Californian Animals. California Academy of Science 2: 118-123.
Fischer, Dan L. 200l. Early Southwest ornithologists, 1528 - 1900. Univ. Arizona Press, Tucson.
Hume, Edgar E. 1942. Ornithologists of the United States Army Medical Corps. The Johns Hopkins Press, Baltimore.
Lurie, Edward. 1988. Louis Agassiz, a life in science. The Johns Hopkins Press, Baltimore.
Van Devender, Thomas R. 2002. The Sonoran Desert tortoise: natural history, biology, and conservation. Univ. Arizona Press/Arizona-Sonoran Desert Museum, Tucson.
Woodbury, Angus M. and Ross Hardy. 1948. Studies of the desert tortoise, Gopherus agassizii. Ecological Monographs 19: 145-200.