Environmental factors controlling the foraging behavior of a desert subterranean termite, Gnathamitermes perplexus (Banks) Item Type text; Thesis-Reproduction (electronic) Authors La Fage, Jeffery Paul, 1945- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 02/10/2021 15:55:15 Link to Item http://hdl.handle.net/10150/554748 ENVIRONMENTAL FACTORS CONTROLLING THE FORAGING BEHAVIOR OF A DESERT SUBTERRANEAN TERMITE, GNATHAMITERMES PERPLEXUS (BANKS) by Jeffery Paul La Fage A Thesis Submitted to the Faculty of the DEPARTMENT OF ENTOMOLOGY In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE In the Graduate College THE UNIVERSITY OF ARIZONA 1 9 7 4 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfill­ ment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowl­ edgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the inters ests of scholarship. In all other instances, however, permission must be obtained from the author. APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown Below; ■ 4 / /Ir r /A WILLIAM L. NUTTING' Professor of Entomology/ ACKNOWLEDGMENTS My sincere gratitude is extended to Dr. William L . Nutting for his continued advice and patience throughout the preparation of this thesis. I am also indebted to Dr. Larry Crowder and Dr. Gordon Waller for reviewing this manuscript and for serving on my graduate committee. For their helpful suggestions concerning statistical analyses, I am indebted to Dr. James Gebert and Dr. Robert Kuehl. Appreciation is also extended to Mr. Mike Topliff of the University of Arizona Computer Center for his patient assistance in computer graphing. For their assistance in gathering field data, I am grateful to my wi f e , Wendy, Dr. W. L, Nutting, Dr. Michael I . Haverty, Marsha Haverty, Mrs. Ruth Nutting, Jeff Nutting, Gardner Nutting, Don Chandler, Dr. Margaret Collins, and Dr. Richard V. Carr. For their help in processing field data, appreciation is extended to Ms. Verne King, Dr. C. Romesburg. Dr. Kim Bridges, and Dr. Mark Westoby. TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS ..... "............ '.......... vi LIST OF TABLES ? ® o■ » » * ® o © © © © © © © © © © © © v n ABSTRACT viii INTRODUCTION 1 MATERIALS AND METHODS 4 i Site Description . 4 Sampling Methods . 6 Environmental Measurements 14 a t a .A.n a l^z sis © © © © © © © © © * © © © © © © © © 15 RESULTS AND DISCUSSION . 17 Seasonal Trends in Foraging 17 Environmental Factors Affecting Foraging . © . © , 21 Equation Development 24 SUMMARY © © © - © © © © © © © © © © © © © © © © © © © © 38 REFERENCES © © © © © © © © © © © © © © * © © © © © © © 40 LIST OF ILLUSTRATIONS Figure 1. Earthen shelters built by Gnathamitermes sp. in California 2. Daily maximum and minimum air temperatures from August 29, 1971 to October 13, 1972 (day 0-420) on the Santa Rita Experimental Range, Pima County, Arizona ......... 3. Toilet paper roll attacked by Gnathamitermes perplexus, X 0.83 ............. 4. Toilet paper roll attacked by Heterotermes ^iur eu s, 3C 1.15 . ..... 5. Area for studying foraging behavior of Gnathamitermes perplexus on the Santa Rita Experimental Range, Pima County, Arizona ................... 6. Aerial view of the 40 x 40-m area used to monitor the foraging behavior of Gnathamitermes perplexus ........... 7. Map of 16 10 x 10-m plots for studying Gnathamitermes perplexus foraging behavior on the Santa Rita Experimental Range, Pima County, Arizona ......... 8. Seasonal foraging trends of Gnathamitermes perplexus at toilet paper rolls on the Santa Rita Experimental Range, Pima County, Arizona, from 10/15/71 to 10/13/72 »...., 9. Foraging activity of Gnathamitermes perplexus (Y) plotted against temperature (T) (0-40oC) at the roll-soil interface and cumulative rainfall (R)_ (0^6.0 cm) for the week prior to activity checks 10. Foraging intensity of Gnathamitermes perplexus predicted by the equation, Y = -1742.31 - 29.17 T T 20.78 R + 1044.87 In T + 214.16 In R . « , . e . ? , . vi LIST OF ILLUSTRATIONS— Continued Figure Page 11. Foraging intensity of Gnathamitermes perplexus predicted by the equation, Y = -1795.69 - 30.55 T + 1070.36 In T + 212.63 In R — 3.24 R^ ........... 29 12. Foraging intensity of Gnathamitermes perplexus predicted by the equation, Y =-992.32 + 559.26 In T + 172.70 In R , . 30 13. Foraging intensity of Gnathamitermes perplexus predicted by the equation. In Y = 2.39 + 0.31 T - 0.11 R - 0.01 T 2 + 0.54 In R 31 LIST OF TABLES Table Page 1. Equations predicting the number of Gnathamitermes perplexus foragers at 100 toilet paper rolls (Y) as a function of daily mean temperature at the roll^ soil interface (T) and daily rainfall ) eoo ooooeo'opoeeooooo 25 vii ABSTRACT Toilet paper rolls, set out at l-m intervals in a block of 16 10 x 10-m plots, provided the basis for a year­ long study of daily and seasonal variations in the foraging behavior of the subterranean termite, Gnathamitermes perplexus (Banks) (Termitidae: Amitermitinae). Maximum foraging density and dry-weight biomass were estimated at 705,200 foragers/ha and 451.2 g/ha respectively. Foraging activity was limited by upper soil temperatures (0-15 cm) within the range 9-49°C, Periodic rises in soil moisture resulting from rainfall modified foraging intensity. G. perplexus foraged at nearly 100 per cent of the toilet paper rolls on the study site, The number of foragers observed at the surface at a given point in time can be predicted by 2 the equation, In Y = 2.39 + 0.31 T - 0.11 R - 0.01 T + 0.54 In R, where Y = the number of termites at 100 rolls of toilet paper, T = the daily mean temperature at the roll-soil interface, and R = daily rainfall. yiii INTRODUCTION Subterranean termites are among the most abundant but cryptic of animals, a factor making behavioral studies very difficult. Consequently, little is known of their foraging behavior or general activity patterns. Previous studies dealing with the diurnal or seasonal dynamics of foraging have been primarily restricted to harvesters which forage in the open (Bodot 1967, Bouillon 1970) or mound builders which construct above-ground structures (Bodot . 1967, Bouillon and Lekie 1964, Sands 1961). This concentra­ tion of effort on the harvester and mound^building species has created the impression that they are more important ecologically than the more cryptic, totally subterranean species (Sands 1972). Although the density of a totally subterranean termite population has never been estimated reliably (Lee and Wood 1971), it is probable that these species are at least as numerous and ecologically signifi­ cant as the harvesters or mound builders (Sands 1972). The genus Gnathamitermes includes four species which are found in the semi-arid to arid regions of the south­ western United States and northern Mexico (Weesner 1970). All four species construct protective shelters of soil particles over food substrates (Light 1934, Weesner 19701 (Figure 1)., Within these shelters they often entirely 2 Figure 1. Earthen shelters built by Gnathamitermes sp. in California The hollow tubes were left after the plant was consumed. X 0.92. (From Light, Randall, and White, 1930.) consume the plant material leaving nothing but the hollow tubes. From larger or woody materials only the outer weathered layer is removed. G. perplexus (Banks) is found throughout Arizona, southern California, southern Nevada, far-western Texas, and northern Mexico (Weesner 1970). It normally does not attack agricultural crops or structures and thus is not considered an economic pest. It is probable, moreover, that this termite is an important and highly beneficial detritivore in the Sonoran Desert. In this area, where earthworms are apparently absent (Nutting, Haverty, and La Page 1973), G. perplexus may be an important factor in aerating the upper soil horizon. Recent data (Nutting et al. 1973). demonstrate that this termite moves considerable quantities of soil to the surface annually. Furthermore, like all termites, it is active in the gradual breakdown and recycling of dead organic materials. This study was undertaken with the objective of determining some of the environmental factors which regulate the foraging behavior of G„ perplexus. MATERIALS AND METHODS . Site Description The study site was located 40 km south of Tucson, Arizona, on the Santa Rita Experimental Range, at 950 m elevation. The United States Forest Service has made this study area available to the United States International Biological Program, Desert Biome on a continuing basis since 1970. The average annual rainfall of 33 cm occurs equally divided between the winter and summer rainy seasons. Air temperatures typically range from near 40°C in mid-summer to a few degrees below 0°C during winter months. The differ­ ence between maximum and minimum daily air temperatures varied from 6^24°C during the study period (Figure 2\. The area is a shrub-invaded, grassland ecotone, characterized by scattered trees, shrubs, and cacti. The predominant trees are mesquite iProsopis juliflora var. velutina CWoot. )„ Sarg.j and blue palo verde CCe'rcidium f loridum Bentful ,, The shrub layer is made up mainly of burrow weed jAplopappus tenuisectus (Green) Blake] r and the dominant cacti are the chollas lOpuntia fulgida Engel, and ■ 0. spinosior (Engel, and Bigel.) Tourney]. The perennial grasses, which constitute an important part of the diet of G.