Antler Characteristics and Body Mass of Spike- and Fork-antlered Yearling White-tailed Deer at Maturity

We compared antler characteristics and body mass at 4.5 years of age (adult) of 140 white-tailed deer (Odocoileus virginianus) reared in a captive herd at the Kerr Wildlife Management Area (Hunt, Texas) from 1973 to 1990. Each yearling (1.5 years old) was classified as spike(N = 43) or fork-antlered (N = 97), and its live body mass recorded. Fork-antlered yearlings were further partitioned into 3-5 points (N = 33) and >6 points (N = 64) subclasses based on the number of antler points >2.54 cm in length. All deer were reared in 1.62-ha enclosures and maintained on a 16% crude protein diet ad libitum. In ensuing years, antlers were removed and live body mass recorded. At 4.5 years, the gross Boone and Crockett (GBC) score of each buck was measured. The average GBC score of adult deer that were fork-antlered yearlings (127.8 ± 2.0 SE) was greater (P <0.001) than those of spike-antlered yearlings (89.9 ± 2.8). This difference arose from increases (P <0.001) among fork-antlered yearlings relative to spike-antlered yearlings in the average score of 4 GBC components. Adults that had forked antlers as yearlings also had greater (P <0.001) tine lengths and beam circumferences than did adults that were spike-antlered yearlings at each of the 4 GBC measurement positions. Mean body mass of fork-antlered yearlings was greater (P <0.001) than that of spikeantlered yearlings at both 1.5 years (54.0 ± 0.7 vs. 43.6 ± 1.0 kg, respectively) and 4.5 years (78.7 ±1.0 vs. 66.7 ±1.6 kg). When fork-antlered yearlings were partitioned into 3-5 points and >6 points classes, the GBC scores at maturity of the 3 classes of yearlings differed significantly (P <0.05). Average GBC scores of adults that had >6 points as 1997 Proc. Annu. Conf. SEAFWA Spikeand Fork-antlered Deer 401 yearlings (134.0 ± 2.3) exceeded that of adults that were spike-antlered as yearlings by 44 GBC points; and all GBC components differed (P <0.001) among the classes of deer. Our results show that classifying yearlings as either spikeor fork-antlered was useful for predicting antler characteristics and body mass at maturity, and that spike-antlered bucks continued to produce smaller antlers at maturity in our controlled population. Proc. Annu. Conf. Southeast Assoc. Fish and Wildl. Agencies 51:400-413 The relative expression of antler traits and overall antler quality in white-tailed deer changes with age (Sauer 1984). However, because antler development is physiologically linked to body maintenance and growth (French et al. 1956, Moen 1978), the expression of antler traits can be correlated with body mass within (Severinghaus and Moen 1983, Williams et al. 1983) and among (Williams and Harmell 1984) ageclasses and with body condition within age-classes (Smith et al. 1983). Given the linkage between body condition and the expression of antler traits, it is axiomatic that variation in the nutritional quality of forage included in the diet plays a significant role in generating variation in antler trait expression (Teer et al. 1965, Ullrey 1983). Antler size and body mass vary also as a function of an individual's multilocus genotype, as demonstrated by the finding of significant heritabilities for body mass and antler traits at 1.5 years of age (Harmel et al. 1989, Williams et al. 1994, but see Lukefahr and Jacobson 1998). Moreover, antler quality can vary as a function of heterozygosity within an age-class (Smith et al. 1983; Scribner et al. 1984,1989; Scribner and Smith 1990). At the population level, antler quality varies temporally within populations (Smith et al. 1983, Scribner et al. 1989) and spatially among populations with differences in habitat quality (Scribner et al. 1984, Shea et al. 1992a). Within the yearling age-class, the production of spike antlers in white-tailed deer is influenced by parental genotypes (Harmel 1983, Smith et al. 1983, Harmel et al. 1989, Williams et al. 1994) and nongenetic factors, such as maternal effects (Lukefahr and Jacobson 1998), and parturition date (Knoxetal. 1991, Shea etal. 1992fc, but see Causey 1990). While there is general agreement that the incidence of spike-antlered yearlings varies temporally and spatially within and among populations within a region, and among regions, data directly addressing the relative importance of genetic and environmental factors in the production of spike-antlered yearlings in natural populations are nonexistent. Moreover, data addressing this issue in controlled populations are both scant and contradictory (Williams et al. 1994, Lukefahr and Jacobson 1998). As a result, there is disagreement concerning the relative roles of environmental and genetic variation in the production of spike-antlered yearlings in the scientific and especially the popular literature, which is readily accessible to the land manager (Brothers and Ray 1982, Kroll 1991, Armstrong et al. 1995). Thus, the management decision to protect or remove spike-antlered bucks in natural or high-fenced populations remains controversial throughout the southeastern United States (Jacobson and White 1985, Armstrong et al. 1995). 1997 Proc. Annu. Conf. SEAFWA