During January 1968 through September 1973, 233 Key deer (Odocoileus virginianus clavium) were marked for individual recognition and monitored to gain information on their life history, habitat requirements, and behavior. As part of the study, the group size and composition were studied and compared to that of other races of white-tailed deer. The group composition of Key deer was basically matriarchal, with the family group comprised of an adult doe with her offspring. Groups appeared less stable and the ties less strong between family members than those of other whitetails. Adult males were essentially solitary except for transitory associations with females during the breeding season and with other adult males when feeding and bedding during the summer. The weaker family ties between Key deer may reflect their history of isolation in an insular environment, where lack of predators and different competition and selective pressures from that on the mainland resulted in modified social organization and behavior. J. WILDL. MANAGE. 40(3):454-463 This paper reports on a study of Key deer group size and composition as it compares to other populations of white-tailed deer. Formation of family units appears characteristic of all deer in the genus Odocoileus; however, white-tailed deer appear the least gregarious (deVos et al. 1967:413). The social organization of white-tailed deer has been characterized as a matriarchal society with the basic family group comprised of an older doe with her fawns and offspring from previous years (Queal 1962:40, Severinghaus and Cheatum 1956:117, Tibbs 1967:38, Townsend and Smith 1933:305). Hawkins and Klimstra (1970:409) characterized the "family group" as "any grouping involving does and fawns that are spatially and socially related (frequency of association between all members of 50 percent or more) over a substantial period of time (usually s veral months)." Although generally small, groups as large as six (Chapman 1939:260) or seven individuals (Queal 1962:40) were not uncommon. Peterle (1975) suggested that the grouping of deer was related to food distribution, which influenced the formation of a cohesive social unit, which in turn may have been involved in population control. If this were the case it follows that populations of deer evolving under very different feeding conditions could be expected to exhibit differences in their sociobiology, which could be reflected in their group composition. The Key deer, smallest of the eastern races of North American white-tailed deer, has been reported to occur only on a few of the lower Florida Keys (Barbour and Allen 1922). Although the history of these deer is largely unknown, it appears that the population fluctuated, with very low numbers occurring in some years (Barbour and Allen 1922, Dickson 1955:86, U.S. Fish and Wildlife Service unpublished Narrative Reports 1939-1967). It is currently considered endangered (U.S. Fish and Wildlife Service 1974). Information on the Key deer, prior to our study, was mainly from reports by 1 This paper includes information that was part of a dissertation submitted by the senior author in partial fulfillment of the Ph.D. degree requirements at Southern Illinois University, Carbondale. Funding was provided by the U.S. Fish and Wildlife Service, National Geographic Society, North American Wildlife Foundation, National Wildlife Federation, and Southern Illinois University at Carbondale. 2 Present address: Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station 77843. 454 J. Wildl. Manage. 40(3):1976 This content downloaded from 207.46.13.128 on Wed, 07 Sep 2016 06:41:11 UTC All use subject to http://about.jstor.org/terms GROUP SIZE AND COMPOSITION OF KEY DEER" Hardin et al. 455 local residents and occasional sightings in the early 1950's when the population was low (Dickson 1955:83). In 1968 a study was initiated to investigate those factors influencing the Key deer population size, rate of increment, and relationships to the insular environment (Klimstra et al. 1974, unpubl. rep.). A study on behavior, social organization, and life history, which represented a portion of the investigation, was conducted to ascertain their effects on the population dynamics of the herd, and to contribute a feasible management program for this endangered species. During this study data were gathered mainly around and within a portion of the Key Deer National Wildlife Refuge, including the north one-half (about 1,215 ha) of Big Pine Key. Largest of the lower Florida Keys, Big Pine has an area of about 2,430 ha, is 13.4 km long and 3.2 km wide at the widest point (Dickson 1955:20), and had an estimated population of 200-250 deer during the study (Klimstra et al. 1974, unpubl. rep.). Except for periods during January 1972 to 15 March 1972, and 16 June 1972 to 15 March 1973, staff of the Cooperative Wildlife Research Laboratory (CWRL), Southern Illinois University, Carbondale, were in residence on the islands from January 1968 until September 1973. Periods of about 2 weeks also were spent in the field during September and December 1972. Very special thanks are extended J. C. Watson, Sr., Refuge Manager, Key Deer National Wildlife Refuge, for providing unlimited cooperation and making equipment and research facilities available. Others who provided time and effort included A. L. Dooley, R. T. Eberhardt, R. E. Hawkins, B. N. Jacobson, W. B. Klimstra, D. E. Morthland, J. L. Roseberry, and V. H. Silvy. Many residents of the lower Florida Keys contributed substantially to our research efforts.