Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 1980 Size and spacing of sedentary guanaco family groups Robert Thomas Jefferson Jr. Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Biology Commons Recommended Citation Jefferson, Robert Thomas Jr., "Size and spacing of sedentary guanaco family groups" (1980). Graduate Theses and Dissertations. 16257. https://lib.dr.iastate.edu/etd/16257 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. - '(. Size and spacing of sedentary guanaco family groups .t~ --~ I '!/ ?.:J ~ :r~~ -9 by Robert Thomas Jefferson, Jr. A Thesis Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Department of Animal Ecology Major: Wildlife Biology Signatures have been redacted for privacy Signatures have been redacted for privacy Iowa State University Ames, Iowa 1980 1276116 i i TABLE OF CONTENTS Page ABSTRACT iii INTRODUCTION 1 Study Area 2a METHODS 5 RESULTS 8 Distribution and Feeding Preferences of Vegetation Types 8 Feeding Territories 15a DISCUSSION 24 LITERATURE CITED 29 ACKNOWLEDGEMENTS 31 i i i ABSTRACT A socioecological study of the South American guanaco (Lama guanicoe) was conducted from July 1977 to June 1978 on Isla Grande, Tierra del Fuego, Chile. The study area was situated in an ecotone between open Patagonian plains and closed austral forest habitats. Observations of guanaco family groups were made from a 2 story observation hut and from a motor vehicle positioned on the road . Twelve vegetation types were defined and analyzed by the point frame method to determine plant species composition and percent cover. Sites of territorial defenses by family group males were plotted; maps for neighboring males were then compared and territorial boundaries for each season were drawn. Feeding territories were defended year-round by the family group adult male; neighboring groups overlapped very little in their use of space. Shapes of feeding territories were approximately rectangular; territories averaged 29.5 ha in size. Territory quality was estimated using mean primary production per unit area of territory, percentage surface area occupied by the 4 most preferred vegetation types, percentage surface area occupied by the 2 least preferred vegetation types, and mean escape distance from a highly preferred vegetation type to the forest. Two of the 12 vegetation types (VT-4 and VT-5) were highly preferred by adult female guanacos; VT-4 exhibited a statistically significant higher primary production than 8 of the other 11 vegetation types .. Feeding territories dominated by the 2 least preferred vegetation types (VT-11 and VT~14) were nearly twice the size of those territories with a low percentage surface area of those types. Guanaco family groups averaged 7 animals; however , the size of individual family iv groups fluctuated on a seasonal basis. There was no statistically significant difference in the number of adult females between groups. There also was no significant correlation between group size and total primary production per territory (r= -0.21, d.f.=6), but group size and production per ha of territory were close to the acceptable level of significance (r= 0.61). A negative correlation existed between summer and fall mean number of adult females and percentage surface area of the 2 least preferred vegetation types; no correlation existed between number of adult females and the percentage surface area of the 4 most preferred vegetation types. Territory size was positively correlated with the pe rcentage surface area of the 2 least preferred vegetation types and also with mean distance from VT-4 to the forest edge. No statistically significant differences were found between territories using the territory quality variables for analysis. Hm>~ever, the differences that did exist may have caused females to select one territory over another. Explanations for female selection of territories and the benefits accrued to the female are discussed. Adult females did not appear to select territories on the basis of preferred forage availability; however, the amount of least preferred forage may have acted as a selective factor. 1 INTRODUCTION The guanaco (Lama guanicoe) is one of two wild members of the camel family inhabiting South America. Guanacos range from the highlands of Peru, into parts of Bolivia, the length of Chile onto the Patagonian plains and south to Tierra del Fuego (Franklin 1975). This paper is based upon results obtained during the second year of a 2-year project on the socioecology of the guanaco. Prior to this study no detailed investigation of guanaco social organization nor territorial behavior had been conducted. A short-term study of guanacos by Franklin (1975) on t he arid west-facing slope of the Andes in northern Peru suggested that this species was territorial, and Raedeke (1978) reported that guanacos defended territories on Tierra del Fuego. Guanacos are organized socially into sedentary or migratory family groups, male groups, and solo males. Adult females are found within family groups, although occasionally adult female groups without an adult male form in the winter. ·Sedentary family groups and solo adult males live i.n permanent year-round territories. Only the adult male participates in defense of the territory. The exact nature of guanaco social organization and territor iality has been described elsewhere (W. Franklin and R. Jefferson, Department of Animal Ecology, Iowa State University, unpublished manuscript). Objectives of this phase of the study were to determine: (1) if territories of sedentary guanaco family groups were sharply separated 2a and exclusively occupied, (2) if family groups occupied territories of differing resource quality and, if so, what was the effect on group size and degree of occupancy, and (3) if a relationship existed between territory si ze and family group size. Study Area This investigation was conducted on Isla Grande, the principal and largest island of the archipelago of Tierra del Fuego, at the southern tip of South America (see Humphrey et al., 1971). Roughly triangular in shape, Isla Grande is bounded to the north and west by the Straits of Magellan, to the east by the Atlantic Ocean, and to the south by the Beagle Channel. The island is approximately 29,000 km 2 in area; the 2 eastern port ion (12, 500 km ) is part of the republic of Argentina and 2 the west part (16,500 km ) belongs to Chile (Talbot 1974). The study area, locally known as Campo Asseraderro, is on the Chilean side of Isla Grande on the sheep ranch Estancia Cameron (53° 40• S, 69° 55• W). It is located 35 km east of Cameron and 2 km west of the sub- ranch Russfin. Elevation is 488 m above sea level. The study site is a 152 ha open meadow bordered by a beech forest (Nothofagus pumilio) on the north, a road and dwarf beech forest (Nothofagus antarctica) on the south, and a wire fence on the east and west (Fig. 1). This region of the island is an ecotone between open Patagonian pampa and closed · austral forest habitats. The west end of the study area (lines 1 through 12, Fig. 1) is characterized by xeric plant communities and sloping topography, while the central and eastern portions are dominated by mesic to hydric plant communities and flat terrain. The Russfin River, varying 2b Figure 1. Campo Asseraderro study area showing observation hut, grid, and major land features. 3 .J..n lil ... ~ ., ::;) II lo'7 :z: II "II'! ~ z II z~ ,, 0 ojCII ~ j: 0 Ill 17 Ill ~ ~ 1111 Ill: Ill: Ill: "'N 0 Ill ,, ... Ill •I~ ! Ill ,, ~ c ~ ·'"':~ t Ill .,~ Ill Ill: II u Ill z ., ... Ill ~ ,, ... t Ill: "-i z "IN 0 llil 0 N I~ N c II "_, ... I I I II Cllll II II I I I I I I •= I I • '!/ I • .A,I ...I I • .,. I r1 11'1 .I ... I I o/N,,... ,., ... ,,I .,. • I lo 0 II ... •I I •ell I I I I ,.I •Ill I I .... '·'I I I• I •UI I 1 IJ ,,I •Ill • I I" .... I I .I I • •I'! II •N I /·'I I I" .... I I 4 in width from 3 to 5 m. flows from west to east across the study area. Data concerning the climate of Campo Asseraderro are reported elesewhere (Franklin and Jefferson, unpublished manuscript). 5 METHODS Methodology was based on techniques developed by Franklin (1978). A grid of 1.5 km 2 was established on the meadow of Campo Asseraderro. Painted wooden stakes 1.5 m in height were spaced 100m apart in lines roughly perpendicular to the road (Fig. 1). By using the stakes I was able to estimate locations within the grid to the nearest 10 m. Obser vations of guanaco family groups were made from a 2 story observation hut and from a motor vehicle positioned along the road. Once every hour t he area was scanned from left to right and the following . information about each family group present was recorded on a map of the study area: location; total number of animals, including adult males, adult females, yearlings, and juveniles; numbers and age-class of individuals feeding on defined vegetation types; and the distance the adult male was from his family group. An estimate of a group•s continuous daily movement on the meadow was obtained from these hourly samples. Intergroup encounters and territorial defenses were recorded throughout the hour. Four to six groups were typically under observation at the same time.