Major-histocompatibility-complex-associated variation in secondary sexual traits of white-tailed deer (Odocoileus virginianus): evidence for good-genes advertisement

Abstract Good-genes hypotheses predict that development of secondary sexual characters can be an honest advertisement of heritable male quality. We explored this hypothesis using a cervid model (adult, male white-tailed deer, Odocoileus virginianus ) to determine whether antler development could provide an honest signal of a male's genetic quality and condition to adversaries. We compared antler, morphometric, hormonal, and parasitic data collected from hunter-harvested deer to characteristics of the Mhc-DRB (Odvi) , the most widely studied gene of the major histocom-patibility complex (MHC) in Artiodactyla. We detected associations between genetic characteristics at Odvi-DRB and antler development and body mass, suggesting that antler development and body mass may be associated with pathogen resistance in deer and thus may be an honest signal of genetic quality. We also detected associations between Odvi-DRB characteristics and serum testosterone during the breeding season, suggesting that certain MHC characteristics may help deer cope with stresses related to breeding activity. In addition, we observed a negative relationship between degree of antler development and overall abundance of abomasal helminths. Our observations provide support for the hypothesis that antler development in white-tailed deer is an honest signal of quality.     

Does fluctuating asymmetry of antlers in white-tailed deer (Odocoileus virginianus) follow patterns predicted for sexually selected traits?

Secondary sexual characters have been hypothesized to signal male quality and should demonstrate a negative relationship between the size of the trait and degree of fluctuating asymmetry because they are costly to produce. We collected morphometric and antler data from 439 white-tailed deer (Odocoileus virginianus) in Oklahoma, USA, in order to determine whether measures of antler asymmetry follow the patterns predicted for sexually selected characters. Relative fluctuating asymmetry was negatively related to antler size for all deer and within age groups up to five and a half years of age. We did not detect an association between asymmetry and antler size among deer that were six and a half years or older. When categorizing deer by antler size, we found that deer with small antlers (< or = 33rd percentile) had greater levels of relative asymmetry than deer with large antlers (< or = 67th percentile). The relative asymmetry of antlers was negatively related to age and was greatest in deer that were one and a half years old. Relative asymmetry was also negatively related to carcass mass, inside spread, skull length and body length. These data suggest that asymmetry in the antlers of white-tailed deer may be a reliable signal of quality and, as such, may be important in maintaining honesty in intrasexual advertisements during the breeding season.     

Seasonal variations in semen characteristics, semen cryopreservation, estrus synchronization, and successful artificial insemination in the spotted deer (Axis axis)

Ten adult male spotted deer were monitored over a 2-year interval to determine seasonal variations in testicular size, semen characteristics and serum testosterone concentrations, and to determine if there was an association between season and type of antler. Mean (+/-S.E.M.) testicular volume (118.8+/-4.6 cm(3)), serum testosterone concentration (1.2+/-0.1 ng/mL), semen volume (4.1+/-0.6 mL), sperm concentration (338.3+/-24.9 x 10(6) mL(-1)), percentage of morphologically normal sperm (79.1+/-2.8%), and percentage of motile sperm (66.5+/-1.5%) were higher (P<0.05) in hard antler deer (peaked from March to May) than in deer with velvet antlers or in deer in which the antler has been shed. Thus, March-May was considered the physiologic breeding season for these deer; at this time, all stags had hard antlers. Furthermore, a Tris-citrate-based semen extender containing 4% glycerol and 20% egg-yolk was adequate for cryopreservation of semen. Estrus was induced with an implant containing norgestomet, timed transcervical AI was done with fresh semen, and 3 of 10 females were pregnant at 60 days, with fawns born 120 (premature), 240 and 243 days after AI. These results were considered a model for the use of assisted reproductive techniques to conserve other critically endangered deer species of India.     

梅花鹿(Cervus nippon hortulorum)茸角生长发育各阶段血浆睾酮、雌二醇的含量变化

本文用放射免疫测定法对3个不同年龄组的雄性东北梅花鹿茸角生长发育各阶段外周血中的睾酮、雌二醇含量进行了测定。茸期两种激素差异很大,睾酮含量低,雌二醇高,骨化期二者增高很快。对这两种激素含量的变化与茸角发育各阶段的关系进行了讨论。认为只有在二种激素同时增加时,鹿角才能骨化。     

Effect of pinealectomy on seasonal changes in antler growth and concentrations of testosterone and prolactin in white-tailed deer

A 2-year study was conducted to determine under controlled conditions the role of the pineal gland in regulating the seasonal changes in antler growth and reproduction of male white-tailed deer. Blood samples were drawn from 6 pinealectomized (PX) and 18 control (C) deer at intervals of 2 weeks and analyzed for testosterone (T) and prolactin (Prl). Relative scrotal circumference and main beam antler length were recorded. Relative scrotal circumference was similar in PX and C groups, but the normal pattern was delayed 1 to 3 months in the PX deer relative to the C deer. The mean dates of beginning antler growth, velvet shedding, antler casting and pelage changes were significantly later in both years for PX deer than in C deer. Testosterone concentrations peaked 1 month later in the PX deer than in the C deer for both yearling and 2-year-old deer. Prl concentrations in C deer, but not in PX deer, were correlated highly with day length, and the PX deer were delayed relative to the C deer in showing the normal Prl pattern. Increasing levels of Prl in both groups coincided with beginning antler growth in both years. These results indicate that the pineal gland does not originate the seasonal cycles of male white-tailed deer but may synchronize cycles among individual deer, and regulate the circannual rhythm of Prl concentrations which may in turn influence other hormonal cycles.     

The effect of artificial photoperiodicity and antiandrogen treatment on the antler growth and plasma levels of LH, FSH, testosterone, prolactin and alkaline phosphatase in the male white-tailed deer

1. Artificial extension of day-length in adult male white-tailed deer during the autumn induced: (a) premature casting of antlers, early onset of the new antler growth and out of season mineralization, (b) early elevation of plasma levels of prolactin, LH, FSH, testosterone and alkaline phosphatase and (c) out of season hair molt. 2. Intramuscular administration of the antiandrogen cyproterone acetate immediately after velvet shedding induced: (a) dramatic reduction of testosterone levels in plasma, (b) premature casting in bucks with fully mineralized antlers and (c) renewal of bone rebuilding activity in incompletely mineralized antlers which resulted in blockage of casting.     

Effect of antiandrogen cyproterone acetate on the development of the antler cycle in Southern pudu (Pudu puda)

The antler cycle of pudu is similar to other cervids, but unlike most boreal deer, male Southern pudu (Pudu puda) exhibits two seasonal peaks of LH and testosterone. In that respect, pudu is similar to roe deer. Whereas the antler cycle in some deer species, such as roe deer or white-tailed deer, is very sensitive to variation of testosterone, in other cervids, such as fallow deer or reindeer, a blockade of androgens with cyproterone acetate (CA) has little or no effect on the timing of the antler casting. In order to test the sensitivity of pudu antlers to variations of androgens, CA (administered 2x weekly at 50 mg/buck) was injected intramuscularly for 3 weeks in 5 adult male pudu, starting February 19 (late summer). Four other males of similar age served as controls. The experiment was performed at the University of Concepcion, Chile, latitude 36.6 degreeS. Blood samples were taken once a week between January 19 and April 3. In CA-treated bucks, the antlers were cast approximately 3 weeks after the initiation of CA treatment and a new antler growth began almost immediately. The antlers reached about 5 cm in length, before ceasing to grow at the end of April, when they became mineralized and were subsequently polished. CA had no effect on the already declining levels of LH. Plasma levels of testosterone in controls increased from February 15, whereas in CA-treated bucks remained depresses until March 21. It is concluded that similarly to white-tailed deer, the antler cycle of Southern pudu is very sensitive to manipulation of androgen levels.     

Assessment of the sexual and antler potential of the male white-tailed deer (Odocoileus virginianus) by Gn-RH stimulation test

Twelve mature white-tailed bucks were injected with gonadotropin regulating hormone (Gn-RH, 100 micrograms/deer) during the rut (November) and during the spring (April). In the rut, superior bucks (with actual or potential large body weight, trophy antlers and a high social rank) responded to Gn-RH with a small increase of LH (below 20 micrograms/ml) and a profound rise in testosterone (T) (30-50 ng/ml). The inferior animals exhibited high increase of LH (30-40 ng/ml) but a low rise in T (below 10 ng/ml). FSH levels increased only slightly after Gn-RH and the concentrations were not related to reproductive performance. During the spring, increase in LH levels after Gn-RH administration greatly exceeded the rise of T, but no relationship was found between hormonal levels and the reproductive potential. FSH levels increased remarkably after Gn-RH administration. Gn-RH (administered during the rut) might be used for assessment of the potential for reproductive and antler performance.     

Effect of metabolic acidosis on white-tailed deer antler development

Metabolic acidosis can result when herbivores consume browse diets high in plant secondary compounds. One mechanism for buffering excess acid is the mobilization of calcium and other alkaline salts from the skeletal system. White-tailed deer (Odocoileus virginianus) and other cervids consuming browse during antler formation may use minerals essential for antler development as buffers, resulting in altered antler characteristics. Our research objectives were to examine the effects of metabolic acidosis on mineral metabolism, acid-base homeostasis, and antler development in white-tailed deer. Fifteen male white-tailed deer were assigned to one of three diets: 2% NH(4)Cl, 3% commercial tannic acid, or a basal ration without additive. Two feeding trials were completed on each deer to determine nutrient use. Urine pH and the percentage of urinary nitrogen excreted as NH+4 varied by diet. No significant diet or trial effects occurred for nitrogen, calcium, phosphorus, magnesium, or sodium use. Urinary calcium excretion varied between diets. No dietary differences were observed for antler characteristics. The NH(4)Cl diet induced metabolic acidosis but did not alter antler development in white-tailed deer. Skeletal mineral reserves and mineral intake appeared sufficient to buffer excess acids and support antler development.     

Testosterone and estradiol concentrations in serum, velvet skin, and growing antler bone of male white-tailed deer

The growth and mineralization of antlers correlate with the seasonal variation of serum androgens. Whereas seasonal levels of testosterone (T) in plasma are well established, steroid concentrations have not yet been determined in the tissues of growing antlers. Therefore, RIA was used to determine T and 17beta estradiol (E2) in serum, and three areas (tip, middle, and base) of the antler bone and the antler skin, called velvet. Blood and antler tissues of white-tailed deer (Odocoileus virginianus) were collected from May to August. The difference between levels of T and E2 among the sites was calculated using the square root transformation followed by a mixed model analysis with individual deer and an interaction of individual and year (individual(*)year) as a random factor. Concentrations of T in serum (799+/-82 pg/ml) were higher than T values in the velvet (589+/-58 pg/ml, P<0.01) and in the antler bone (538+/-58 pg/ml, P<0.001). Estradiol concentrations differed among antler tissues and serum (P<0.001) and between years (P<0.01). Estradiol concentrations in serum (25+/-25 pg/ml) were consistently lower than those in antler bone (208+/-11 pg/ml, P<0.001) and velvet (150+/-12 pg/ml, P<0.001). The E2:T ratio in serum was 1:10-60. The same ratio for the antler bone was only 1:2-3 and for the velvet 1:3.5. It is concluded that higher T and lower E2 concentrations found in plasma, as compared to antler bone or antler velvet, may indicate a partial metabolism of systemic androgens into estrogens xin the tissues of growing antlers.     

Thyroxine levels and antler growth in white-tailed deer

1. Five normal male, 5 female, and 3 castrated fawns and 5 adult male white-tailed deer were housed in individual pens for one year to compare the relationships between thyroxine (T4) and other blood parameters and the antler cycle. 2. Biweekly serum samples were examined for T4 titers and levels of serum calcium (Ca), inorganic phosphorus (P), and alkaline phosphatase activity (AP). 3. Seasonal T4 changes were found in all deer groups, with elevated titers in the fall. Female fawns had overall lowered T4 levels. In male fawns and adult bucks, T4 seemed to play a synergistic role in antler initiation and growth. 4. Serum Ca levels remained constant throughout the year, but with lower levels in the female fawns. 5. Serum P levels were also constant seasonally, but with higher levels in the female fawns. There was no age effect on either Ca or P. 6. An age effect was evident on plasma alkaline phosphatase with lower activity in adult bucks. There was no sex effect on AP activity. 7. T4 might have an indirect association with the enzyme AP in Ca and P transport system in white-tailed deer.     

Patterns of testosterone in male white‐tailed deer (Odocoileus virginianus): Seasonal and lifetime variation

Testosterone is strongly associated with the annual development of antlers in cervids, but endocrine research on wild, freely breeding ungulates is often done without repeated capture of known‐aged individuals. As a result, our knowledge on how testosterone fluctuates over the course of a lifetime and variation in lifetime patterns among individuals is limited. We investigated patterns of testosterone in a freely breeding population of white‐tailed deer (Odocoileus virginianus) in Alabama, USA, that breeds in January. Testosterone peaked during the height of the breeding season, despite this period occurring approximately 2 months later than in most temperate‐region white‐tailed deer populations. Age‐related differences in testosterone were only prevalent during the breeding season, with bucks ≥3.5 years old having greater testosterone (853 ng/dl ± 96 SE; p = 0.012) than bucks 1.5–2.5 years old (364 ng/dl ± 100 SE). Additionally, an individual''s testosterone level as a yearling was not positively associated with their lifetime maximum testosterone level (p = 0.583), and an individual''s mean testosterone level was positively associated with lifetime testosterone variation (p < 0.001). To our knowledge, our study is one of the first to assess how testosterone early in life might relate to individual testosterone later in life. We believe these data provide insight into lifetime hormonal patterns in cervids, and that these patterns may indicate intraspecific variation of lifetime reproductive strategies.     

Genetic and Environmental Interaction in White-Tailed Deer

ABSTRACT We applied an 8-year selection process in an attempt to determine if yearling antler quality in subsequent cohorts could be improved by selecting for yearling male white-tailed deer (Odocoileus virginianus) exhibiting relatively superior antler potential under suboptimal nutritional conditions. In 41 single-sire (breeding M) breeding herds, 217 yearling males were produced on an 8% protein diet of limited quantity. All antler measurements increased significantly (P < 0.001) during the study: number of points (+3.2), inside spread (+96.5 mm), main beam length (+129.1 mm), basal circumference (+21.6 mm), and total antler weight (+231.3 g). Furthermore, mean gross Boone and Crockett (GBC) score increased (P < 0.001) linearly throughout the study, with the GBC of the 1999 cohort exceeding that of the 1993 cohort by 36.4 in (923.0 mm). These data provide insight to the effectiveness of a selection process (i.e., culling) in an overall deer-management program.     

Serum and urinary levels of reproductive hormones associated with the estrous cycle in white-tailed deer (Odocoileus virginianus)

Concentrations of estradiol-17β (E₂), progesterone (P_o), and luteinizing hormone (LH) in serum and estrone glucuronide (E₁G) and pregnanediol glucuronide (PdG) in urine were determined by direct radioimmunoassay in five yearling and three adult female white-tailed deer (Odocoileus virginianus) from 14 October to 20 December 1985. Elevated levels of LH were recorded before the first estrus of the breeding season and immediately preceding or during behavioral estrus. Urinary E₁G and PdG concentrations were poorly correlated with serum levels of E₂ and P_o, respectively. Serum P_o levels prior to the first estrus of the breeding season indicate that pubertal yearlings experience silent ovulations and suggest that silent ovulations may be important in the transition from adolescence to cycling adult in white-tailed deer. © 1992 Wiley-Liss, Inc.     

Effectiveness of Spayvac for reducing white-tailed deer fertility

Overabundant white-tailed deer (Odocoileus virginianus) populations have been reported in many urban and suburban communities across the United States. Large populations of deer can potentially increase the risk of human-wildlife conflicts, such as deer-vehicle collisions, transmission of disease to humans, and vegetation damage. In 2003, efforts to control white-tailed deer numbers were initiated at the National Aeronautical and Space Agency's (NASA) Lyndon B. Johnson Space Center (JSC) in Houston, Texas, using the long-lasting, single-dose contraceptive SpayVac. Our objectives were to evaluate the effectiveness of SpayVac for reducing white-tailed deer fertility and determine the partial cost for treatment. Between 2003 and 2004, we monitored 45 adult female deer (34 treated with SpayVac, 11 controls treated with a placebo). Fawning rate over 2 yr for deer treated with SpayVac >30 days prior to the rut was 0% (n=31), whereas the fawning rate for control deer was 78% (n=11). Inoculation 1 mo prior to the breeding season was sufficient time to achieve fertility control. We conclude that SpayVac can effectively reduce the fertility of urban white-tailed deer.     

Correlates of variation in deer antler stiffness: age, mineral content, intra-antler location, habitat, and phylogeny

To test correlations between the stiffness of deer antler and aspects of cervid ecology, we measured the stiffness (in bending) of antler from white-tailed deer ( Odocoileus virginianus ) and compared our results to previous measurements from antlers of other cervid species. Stiffness of antler specimens did not correlate significantly with mineral content or the location within the antler from which specimens were taken in O. virginianus. However, antler stiffness in white-tailed deer decreased significantly between two- and three-year-old bucks, matching the time in O. virginianus life history when males shift from sparring with mostly larger individuals to sparring with mostly smaller individuals. Stiffer antlers may enable younger, smaller bucks to have a more effective lever through which their smaller muscular forces can be transmitted during sparring with older, larger bucks. The stiffnesses we measured for white-tailed deer antler are similar to values measured previously from other members of the odocoileine lineage, which are lower than those previously measured from the antlers of deer living in tropical habitats. However, confidence limits for maximum likelihood reconstructions of the ancestral stiffness of deer antler span the range of high stiffnesses found among tropical deer; furthermore, parsimony-based reconstructions of ancestral antler stiffness are equivocal. Thus, the high antler stiffnesses of tropical deer may reflect the retention of an ancestral condition, rather than adaptation to year-round antler use.     

Effect of advancing births on testosterone until 2.5 years of age and puberty in Iberian red deer (Cervus elaphus hispanicus)

This study aimed to determine the age of attainment of puberty, as well as the pattern of reproductive seasonality in males of Iberian red deer and the relationship of these factors with antler development. A second aim was to examine the effect of the advance of births on the variables mentioned. Fourteen males of Iberian deer were used, five of them born 2.5 months before the others (early group). Male deer were blood sampled from birth until 2.5 years of age to assess the time course of plasma testosterone. The study also included measurements of testicular and neck circumference. As in most cervids, concentration of plasma testosterone was associated to the phases of antler development. Early development affected testosterone titres, since the most precocious males in antler growth also showed higher levels of testosterone during the first and second year of age. In the same way, results suggested that the advance of calving may result in puberty attainment in the first autumn of its life. However, this would require an advance of calving greater than the one we induced since puberty in the Iberian deer is usually attained during second autumn of life at 15-16 months of age. Finally, calving advance also affected antler development. Thus, two of the five males whose birth was advanced, showed two antler cycles in their first year of life.     

Survival and Cause-Specific Mortality of Mature Male White-Tailed Deer

ABSTRACT Understanding sources of male deer mortality is a prerequisite to a successful management program, especially in Texas, USA, where white-tailed deer (Odocoileus virginianus) are the most economically important game species. South Texas, USA, is one of the few areas where males reach older age classes (> 4.5 yr), in part because of intense population management. Therefore, we obtained survival rates and causes of mortality of 48 mature male deer in south Texas, USA, over 2 years. We calculated Kaplan—Meier survival estimates during 2 study years modified for a staggered-entry design and annual survival rates for one cohort of deer from 1998 to 2004 using recapture and radiotelemetry data. We documented 21 mortalities (16 harvest and 5 nonhunting mortalities). Average annual survival of the known-aged 1998 cohort was 82% with 52% of surviving to 6.5 years of age. Survival in study year 2 (0.497 ± 0.069) was less than in study year 1 (0.781 ± 0.073; P = 0.0047), largely because males had finally reached harvestable age (> 6.5 yr old). All but one non-harvest mortality occurred during the rut or postrut periods. It appears that a large percentage of males can reach mature age classes under intense population management, making them available for harvest when at peak antler size. This allows for increased economic returns on intensively managed white-tailed deer populations.     

Effects of selective harvest on antler size in white-tailed deer: A modeling approach

Selective harvesting in wild deer (Odocoileus spp.) populations is a common practice that may influence antler size. However, in free-ranging populations, response due to selection is unknown or difficult to quantify because antlers are influenced by nutrition and population demographics. We used quantitative genetic models to predict how white-tailed deer (O. virginianus) antlers would respond to selection and what variables (i.e., population size, age structure, mating ratio, and heritability) most affected antler size. We validated our quantitative genetics program by comparing model results with a population of deer used for controlled breeding experiments; modeled antler points (AP) and score increased (2.2–4.3 AP and 48.5–97.7 cm, respectively) after 8 years of selection, similar to observed increases in AP (3.2) and score (92.3 cm) from the controlled population. In modeled free-ranging populations, mating ratio, age structure, and heritability were more important in influencing antler size than size of the population. However, response to selection in free-ranging populations was lower (0.1–0.9 AP) than controlled breeding populations even after 20 years of selection. These results show that selective harvesting of free-ranging white-tailed deer may be inefficient to change population-level genetic characteristics related to antler size. Response of antlers in free-ranging deer will be less than controlled populations, and possibly modeled free-ranging simulations, because individual reproductive success of males is lower, breeding is done by a large group of males, and reproductive and survival rates are lower. These factors, and others, reduce the amount of improvement that can be made to antlers due to selection. Therefore, selective harvesting in free-ranging populations should be justified for managing population demographics and dynamics, but not for changing the genetic characteristics of populations. © 2011 The Wildlife Society.     

Seasonal variation in male testosterone levels in a tropical bird with year‐round territoriality

Testosterone is important in mediating investment in competing activities such as territoriality, parental care, and maintenance behavior. Most studies of testosterone function have focused on temperate species and less is known about the role of testosterone in territoriality or variation in mating systems of tropical species. Results of studies of tropical species with year‐round territoriality indicate that territorial aggression during the non‐breeding season is maintained with low levels of testosterone, and increased levels of testosterone in males during the breeding season may increase mating opportunities or aid in competition for mates. We studied seasonal variation in testosterone levels of male Red‐throated Ant‐tanagers (Habia fuscicauda), a socially monogamous species with year‐round territoriality and with high levels of extra‐pair matings (41% of young), to determine if testosterone levels increased during the breeding season. We captured males during the non‐breeding and breeding seasons and collected blood samples for hormone analysis. We found that mean testosterone concentrations were low during the non‐breeding season (0.18 ± 0.05 [SD] ng/ml, range = 0.11–0.31 ng/ml), and significantly higher during the breeding season (2.37 ± 2.47 ng/ml, range = 0.14–6.28 ng/ml). Testosterone levels of breeding males were not related to aggression levels as measured by attack rates toward a stuffed decoy or singing rates during simulated territorial intrusions. These results suggest that the higher testosterone levels of breeding male Red‐throated Ant‐tanagers may be important in an extra‐pair mating context, possibly in display behavior or mate attraction, but additional study is needed to clarify the role of testosterone during the breeding season.