Ram Groups Research Articles

The effects of ram exposure during progestagen oestrus synchronisation and time of ram introduction post progestagen withdrawal on fertility in ewes

Three experiments were undertaken to investigate the effect of a pre-mating ram exposure during progestagen synchronisation treatment on time of breeding, ovulation rate, embryo quality and fertility and any interaction with time of ram introduction for breeding post sponge withdrawal. Crossbred ewes in experiment 1a ( n = 348), 1b (mule; n = 133) and 2 ( n = 58) underwent a 12–14 days synchronisation protocol. Three days prior to sponge withdrawal ewes were divided into Control (ewes in continued isolation from rams) or +Ram (ram-exposed) groups. Rams were introduced to +Ram ewes and remained with ewes until sponge withdrawal. Ewes in experiments 1a and 2 received eCG at sponge withdrawal and were reintroduced to rams at either 36 or 48 h post sponge removal (PSR). In experiment 1b, ewes did not receive eCG and were reintroduced to rams at 24 h PSR. In experiments 1a and 1b time of breeding, date of lambing and litter size were recorded. In experiment 2, ewes were slaughtered 5 days post breeding, reproductive tracts flushed and corpora lutea, ova and embryos assessed. Fewer +Ram ewes were mated by 96 h PSR ( P < 0.001) than Control ewes in experiment 1a but not when rams were introduced earlier in experiment 1b. In experiment 1a, ram introduction at 36 h PSR improved conception to first service compared to introduction at 48 h PSR ( P < 0.01) in both +Ram and Control groups. In experiments 1a and 1b, +Ram ewes had reduced litter size caused by more single births (1a; P < 0.001, 1b; P < 0.01). In experiment 2, +Ram ewes had fewer corpora lutea than Control ewes ( P < 0.001) but embryo quality was similar. However, more good embryos were produced when rams were introduced for breeding at 36 h compared to 48 h PSR ( P < 0.001). We conclude that a pre-mating ram exposure during the synchronisation treatment reduced the number of ewes mated at and conceiving to the first service. This was partially overcome by introducing rams for breeding earlier (24 or 36 h compared to 48 h PSR) but the most dramatic decrease in fertility was due to a reduction in ovulation rate in the ram-exposed ewes.

VIGILANCE, PREDATION RISK, AND THE ALLEE EFFECT IN DESERT BIGHORN SHEEP

Knowledge of how predation risk affects population survivorship is important for understanding predator–prey relationships and designing effective conservation strategies. The Allee effect (inverse density dependence) can be generated when antipredator strategies become inefficient in small groups of prey, thus making the population more susceptible to catastrophic population collapse and extinction. Many populations of desert bighorn sheep (Ovis canadensis) are declining, and predation is, in many cases, a major mortality factor. We studied desert bighorns at the Red Rock Wildlife Area, New Mexico, USA, to assess predation risk in different group types (ram, ewe, mixed) and age–sex classes. Multiple regression analysis revealed that predation risk (as estimated by individual vigilance) increased with smaller group size and greater inter-individual distance for all bighorns, with groups of <5 individuals subject to the greatest risk. Although rugged terrain is thought to provide refuge from predators, habitat ruggedness did not influence vigilance. The biggest males in ram groups experienced the greatest predation risk in that they were in the smallest groups, were most likely to be solitary, and were spaced farther apart from conspecifics. Although big rams spent twice as much time vigilant as other age–sex classes, collective alertness was lowest for ram groups. The conclusion that big rams were most at risk from predation was partially supported by the recent predation history of the population and previous studies in which mountain lion (Felis concolor) kills were biased toward rams. We discuss the management implications of these results for small populations subject to Allee effects, including reintroduction and/or translocation practices and selective removal of problem predators. We suggest that the use of multivariate techniques to simultaneously explore the influence of multiple factors and the use of vigilance as a correlate of predation risk would be useful management tools for assessing seasonal and class-specific vulnerability to predation.

Effect of ram exposure at the end of progestagen treatment on estrus synchronisation and fertility during the breeding season in ewes

Two experiments were conducted to examine the effects of ram exposure during the breeding season, in combination with progestagen treatment on estrus synchronization, fertility the LH surge and ovulation in ewes. Experiment 1 was subdivided into experiments 1a and 1b. In all experiments cross-bred ewes were treated with an intravaginal sponge for 12–14 days and three days before sponge withdrawal ewes were divided into control (no further treatment; n=191, 103 and 50 for experiments 1a, 1b and 2, respectively) or ram exposed (three mature rams per 50 ewes were introduced; +Ram; n=187, 99 and 49 for experiments 1a, 1b and 2, respectively). At sponge withdrawal ewes in Experiments 1a and 2 received 500 IU eCG and rams were removed from all the +Ram groups. In Experiments 1a and 1b, raddled, entire rams were introduced to ewes 48 h after sponge withdrawal. The timing of mating was recorded and ewes were maintained until lambing. In Experiment 2, estrus behavior was determined every 4 h and the time of the LH surge and ovulation were determined from a subset of 10 ewes per group. In Experiment 1a, less +Ram ewes were bred by 48 h after ram introduction (control 98% versus +Ram 89%, P<0.001) and in Experiments 1a and 1b 14% fewer ( P<0.05) of the ewes bred in the first 3 h after ram introduction lambed to that service. In Experiment 1a, ram exposed ewes had a lower litter size than control ewes (1.93±0.06 versus 1.70±0.06 lambs per ewe; P<0.05). In Experiment 2, rams advanced ( P<0.05) estrus, the LH surge and ovulation by 2–6 h compared with control ewes. We speculate that exposure of ewes to rams increased LH secretion and that this in turn increased follicle development and the production of oestradiol that led to a more rapid onset of estrus, the LH surge and ovulation compared to control ewes. Unexpectedly, ewes that were bred had lower fertility in the +Ram groups than control groups.

Sexual segregation in desert bighorn sheep (Ovis canadensis mexicana)

One or several factors could explain sexual segregation, in which males and females of polygynous, sexually dimorphic species form separate herds during most of the year. Bighorn sheep (Ovis canadensis) are polygynous ungulates that exhibit extreme sexual dimorphism and segregate into ram and ewe herds outside of the rutting season. Four major hypotheses for sexual segregation were tested in a population of desert bighorn (O. c. mexicana) at the Red Rock Wildlife Area, New Mexico, from 1999-2001. We collected data on the size, composition, and location of ram and ewe groups during the summer period of segregation. Activity budgets were recorded for males in ram herds and females in ewe herds, and foraging selectivity was measured for males and females in mixed groups during early rut. Habitat was evaluated by measuring forage availability, ruggedness, and visibility at sites utilized by ram and ewe groups. Ram herds utilized areas with more available forage compared with ewe sites, while ewe groups preferred more rugged terrain than that used by ram groups. Ewe groups occurred much closer to free water sources than did ram groups. Bighorns in ram and ewe groups did not differ in foraging time or selectivity, nor did time spent moving, reclining, or ruminating differ between the sexes as predicted by the 'activity budget hypothesis'. The results support the predictions of the 'reproductive strategy-predation risk hypothesis', which proposes that males seek more abundant forage in order to build up body condition needed to maximize mating success (even if exposing themselves to greater predation risk), while females choose rugged terrain that minimizes predation risk to themselves and their offspring (even if sacrificing forage abundance). Female bighorns chose sites that provided access to water, also predicted by the 'reproductive strategy-predation risk hypothesis', indicating that lactation-related water requirements may constrain the movements of ewe groups and contribute to patterns of sexual segregation in desert bighorn.

Behavioral and endocrine responses of hair sheep ewes exposed to different mating stimuli around estrus

Hair sheep ewes were used to evaluate the influence of various levels of mating stimuli on the duration and timing of estrus and LH concentrations around estrus. Ewes were treated with PGF2α (15 mg, im) 10 d apart. At the time of the second PGF2α treatment (Day 0) ewes were placed in groups and exposed to different types of mating stimuli. One group of ewes (n = 16) was exposed to an epididymectomized ram (RAM), a second group of ewes (n = 16) was exposed to an epididymectomized ram wearing an apron to prevent intromission (APRON) and a third group of ewes (n = 17) was exposed to an androgenized ovariectomized ewe (T-EWE). Jugular blood samples were collected from ewes at 6-h intervals through Day 5. Plasma was harvested and LH concentration was determined by RIA. The ewes were observed at 6-h intervals to detect estrus. A ewe was considered to be out of estrus when she no longer stood to be mounted by the teaser animal. There was no difference (P > 0.10) in the proportion of ewes expressing estrus (79.6%) or having an LH surge (85.7%) among the treatments. Neither the time to estrus nor the duration of estrus were different (P > 0.10) among APRON, RAM or T-EWE groups (41.6 ± 3.8 vs 43.6 ± 3.6 vs 46.1 ± 3.6 h, respectively, and 26.5 ± 2.2 vs 24.8 ± 2.3 vs 30.5 ± 2.2 h, respectively). The time to LH surge was similar (P > 0.10) among APRON, RAM and T-EWE groups (51.2 ± 4.5 vs 51.2 ± 4.7 vs 52.7 ± 4.5 h, respectively). The magntude of the LH surge was similar (P > 0.10) in the T-EWE, APRON and RAM ewes (99.7 ± 4.9 vs 87.2 ± 4.9 vs 85.8 ± 5.0 ng/ml, respectively). The time from estrus to the LH surge was no different (P > 0.10) among APRON, RAM or T-EWE ewes (10.1 ± 2.2 vs 9.8 ± 2.3 vs 11.6 ± 2.3 h, respectively). These results show that the expression and duration of estrus are not influenced by different types of mating stimuli in hair sheep ewes. In addition, the timing and the magnitude of LH release does not appear to be influenced by mating stimuli around the time of estrus.

Influence of castration and estrogen replacement on sexual behavior of female-oriented, male-oriented, and asexual rams.

An experiment was conducted to determine whether exogenous estradiol-17beta (E2) could restore sexual behavior in castrated rams. The protocol consisted of three sequential 6-wk periods during which rams were studied while 1) intact, 2) bilaterally castrated, or 3) implanted s.c. with two 7.6-cm silastic implants each containing 309+/-16 mg of E2. Rams (classified as female-oriented [FOR, n = 7], male-oriented [MOR, n = 7], or asexual [n = 7]) were subjected to 30-min sexual behavior tests every 2 wk during the ensuing 18 wk. Rams were observed for mounts and ejaculations using two ovariectomized, estrous ewes and two intact males secured in stanchions. Behavioral data were analyzed using the signed rank test, but asexual rams showed no sexual behavior and therefore were not evaluated statistically. Jugular blood was collected prior to castration and at the end of the 18-wk period, and testicular venous (n = 21) and arterial (n = 8) bloods were collected immediately prior to castration. Radioimmunoassay was used to quantify systemic levels of estrone (E1), E2, and testosterone (T) and testicular serum concentrations of oxytocin (OT). Mounting behavior of MOR and FOR declined after castration (P < .05 and P < .10, respectively). Castration reduced the number of ejaculations by FOR (P < .05), but not by MOR (P > .10). Mounting behavior of castrated MOR and FOR was not affected by E2 treatment relative to that observed if castrated only (P > .10). Treatment of asexual rams with E2 did not stimulate sexual behavior in these rams. There were no marked differences (P > .10) among ram groups with regard to serum concentrations of E1, E2, or T prior to castration (overall mean +/- SE, 12.8+/-.7, 7.6+/-.5, and 2,670+/-780 pg/mL, respectively) or any difference (P > .10) in systemic concentration of E1 or E2 among ram groups after rams were implanted with E2 (overall mean +/- SE, 9.7+/-.7 and 9.0 +/-.7 pg/mL, respectively). Serum concentrations of E2 after implantation of the steroid did not differ from those present while rams were intact (P > .10). Testicular venous and arterial serum concentrations of OT were low and did not differ within or between rams. These results suggest that restoration of E2 concentrations to physiological levels in castrated adult rams (regardless of sexual orientation) cannot stimulate or reestablish sexual behaviors to levels observed prior to castration.

Myocardial fibrosis rather than hypertrophy induces diastolic dysfunction in renovascular hypertensive rats

The aim of the present study was to evaluate the effect of interstitial fibrosis alone or associated with hypertrophy on diastolic myocardial function in renovascular hypertensive rats. Myocardial function was evaluated in isolated papillary muscle from renovascular hypertensive Wistar rats (RHT, n = 14), renovascular hypertensive rats treated with the angiotensin converting enzyme inhibitor (ACEI) ramipril, 20 mg.kg-1.day-1 (RHT RAM, n =14), and age-matched unoperated and untreated Wistar rats (CONT, n = 12). The ACEI treatment for 3 weeks allowed the regression of myocyte mass and the maintenance of interstitial fibrosis. Myocardial passive stiffness was analyzed by the resting tension-length relationship. The myocardial fibrosis was evaluated by measuring myocardial hydroxyproline (Hyp) concentration and by histological studies of the myocardium stained with hematoxylin and eosin or picrosirus red. Left ventricular weight was significantly higher in RHT (0.97 +/- 0.12 g) compared with CONT (0.66 +/- 0.06 g) and RHT RAM (0.69 +/- 0.14 g). The Hyp levels were 2.9 +/- 0.4, 3.4 +/- 0.3, and 3.8 +/- 0.4 micrograms/mg of dry tissue for the CONT, RHT, and RHT RAM, respectively. Perivascular and interstitial fibrosis were observed in RHT and RHT RAM groups. There were lymphononuclear inflammatory exudate and edema around arteries, involving adjacent myocytes in the RHT group. There was an increased passive stiffness in RHT and RHT RAM groups compared with the CONT group. In conclusion, our results indicate that the impaired diastolic function in the renovascular hypertensive rats is related to interstitial fibrosis rather than to myocardial hypertrophy.

The Social Organization of Feral Ovis aries Ram Groups in the Pre‐rut Period

AbstractPrimates are described as having peculiarly complex social behaviour when compared with other mammals, but the methods and expectations of primatologists also differ from those of other mammalogists, confounding the comparison. A very simple social organization has been described for sheep (Ovis aries). Rams of a long‐established feral flock were observed during the pre‐rut period of three successive years, and their communicative behaviour was described and quantified using individual‐focussed methods commonly applied to primates. Rams were found to form long term relationships and their pattern of interaction was partly determined by these as well as by age and rank. Correlation between the effects of age and rank varied with current demography. There was no correlation between rank and horn size. Rams intervened on behalf of weaker colleagues and supported each other in fights. They showed more affiliative behaviour and associated more closely than did ewes. While the leader of the ewe flock was nearly always the oldest ewe present, leadership of ram flocks was less restricted; when together, rams always followed the ewe flock. Comparison is drawn between monkey and sheep social behaviour, and it is concluded that perceived differences are partly due to differences in the expectations and methods of their respective students.

Luteinizing hormone and testosterone response of sexually active and inactive rams.

The objective of this study was to identify rams exhibiting high (HP) and low (LP) levels of sexual performance and to determine whether their respective behavioral responses to ewes in estrus were related to changes in serum testosterone (T) and LH concentrations. Rams were selected on the basis of standardized serving capacity tests. Plasma T and LH concentrations in rams were measured in three experiments: 1) after 15 min of exposure to estrous ewes, 2) after an injection of 500 ng of LHRH, and 3) during an 11-h exposure to estrous ewes. During 15 min of exposure to ewes, HP rams were sexually active, whereas LP rams showed no sexual interest. Secretion of LH was similar (P greater than .05) between ram groups. Sexual arousal, copulation, and ejaculation of HP males were not related (P greater than .05) to LH secretion. Exposure to estrous ewes for 11 h, however, stimulated LH pulse frequency and elevated basal LH and T concentrations in HP but not LP rams (P less than .001). Luteinizing hormone secretion was positively correlated to the frequency of mounts (r = .19; P less than .01) and ejaculation (r = .17; P less than .03). Aggressive behavior of rams directed at ewes was negatively correlated to LH (r = -.22 P less than .003). Concentrations of LH and T after LHRH injection were similar between HP and LP rams (P greater than .05). These results show that the effects of the ewe on LH secretion of rams depend on length of the exposure period and sexual activity of the male.

Effects of treatment with melatonin on the response of seasonally anovular ewes to the introduction of rams

AbstractSixty-four mature ewes (equal numbers of Bluefaced Leicester ♂ × Swaledale ♀ and Suffolk ♂ × (Bluefaced Leicester ♂ × Swaledale ♀) which had lambed in March were separated from their lambs on 1 fune. They were randomly allocated from breed and live-weight blocks to one of four treatments arranged in a 2 × 2 factorial design. All received vaginal implants, with or without melatonin, on 1 June. The implants were removed, all ewes given 20 mg progesterone in oil intramuscularly and equal numbers isolated or introduced to rams on 12 July. Ovarian activity was monitored by progesterone concentrations in blood taken three times weekly from the jugular vein. Four ewes receiving melatonin and four control ewes were bled for 24 h on 6 July to determine plasma melatonin concentrations.Melatonin treatment increased plasma melatonin concentrations during the day. All ewes were anovular prior to 12 July. There were no differences between the two ewe types in their response to treatment. The number of ewes ovulating before 27 August was: control 1; melatonin 6; ram 16; melatonin + ram 16. The mean date of emulation for both the ram and melatonin + ram groups was 21 July. The number of ewes showing oestrous behaviour was 16 and 15 for the ram and melatonin + ram treatments respectively. The proportion of ewes responding to ram introduction was judged as unusually high, possibly as a result of the favourable male:female ratio. Pregnancy rate was in excess of 80% for both treatments, with resulting litter sizes of 14 for the ram and 1·8 for the melatonin + ram treatments respectively (P &gt; 0·05).

The social system of bighorn sheep: grouping patterns, kinship and female dominance rank

The social system of bighorn sheep, Ovis canadensis, was studied for 10 years in a marked population in southwestern Alberta. Yearling sons did not associate with their mothers. Males switched from ewe to ram groups between the ages of 2 and 4 years. No evidence of permanent emigration was found, but some rams left their native group to rut elsewhere, and the proportion so doing increased with the number of rams in the population. Most ewes coexisted with their mothers until 6 years of age, but other uterine kin, such as maternal sisters, rarely overlapped in time. Known matrilines were small and 29% of the ewes had no known live adult maternal kin. The mother's survival did not affect the reproductive success of young daughters. Yearling ewes were in the same group as their mother more often than predicted by a random model, but were not in the same group as their mother for most sightings. Two- and 3-year-old ewes did not associate with their mothers. The outcome of aggressive interactions among ewes was age related, the older ewe winning 92% of interactions. When age was controlled, dominance was not correlated with reproductive success and was negatively correlated with the proportion of male offspring. The social system of bighorn sheep appears to have been shaped by anti-predator and foraging strategies that rely upon learned traditions. Kinship appears to play a limited role. There is little scope for female dominance status to affect reproductive success, because bighorns seldom require resources that can be defended against conspecifics.

Profiles of serological reactivity against cytosoluble antigens of Brucella ovis in experimentally infected rams

Sera from rams infected with and excreting Brucella ovis in the semen (shedders), as well as from animals which had recovered from previous experimental challenge with B. ovis, were analyzed for their serological reactivities against cytosolic antigens of the bacterium. Membrane vesicles, including outer and inner membrane components, were precluded from the analyses by subjecting French-pressed bacteria to ultracentrifugation. The resulting cytosolic supernatant was fractionated into four major antigenic fractions, fractions A, B, C, and D, by high-pressure liquid chromatography. Temporal enzyme-linked immunosorbent assays with the A antigen revealed that all shedder rams displayed a rise-and-surge response, while rams which recovered from experimental challenge showed a rise-and-fall profile. The B antigen was less discriminatory in detecting a difference between the two ram groups, while C and D antigens were serologically unreactive in the enzyme-linked immunosorbent assay. In contrast to the reactivity patterns shown by native high-pressure liquid chromatography-fractionated cytosolic supernatant antigens, immunoblotting of C and D polypeptides generated by boiling in the presence of sodium dodecyl sulfate and mercaptoethanol was particularly useful in distinguishing between sera collected at the mid-surge phase of infected rams from sera obtained at the mid-fall stage of recovered animals. It is likely that native or denatured antigens of different cytosolic fractions may provide useful serological reagents for differentiating between infected rams and those which have recovered from exposure to B. ovis.

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Hair sheep ewes were used to evaluate the influence of various levels of mating stimuli on the duration and timing of estrus and LH concentrations around estrus. Ewes were treated with PGF2α (15 mg, im) 10 d apart. At the time of the second PGF2α treatment (Day 0) ewes were placed in groups and exposed to different types of mating stimuli. One group of ewes (n = 16) was exposed to an epididymectomized ram (RAM), a second group of ewes (n = 16) was exposed to an epididymectomized ram wearing an apron to prevent intromission (APRON) and a third group of ewes (n = 17) was exposed to an androgenized ovariectomized ewe (T-EWE). Jugular blood samples were collected from ewes at 6-h intervals through Day 5. Plasma was harvested and LH concentration was determined by RIA. The ewes were observed at 6-h intervals to detect estrus. A ewe was considered to be out of estrus when she no longer stood to be mounted by the teaser animal. There was no difference (P > 0.10) in the proportion of ewes expressing estrus (79.6%) or having an LH surge (85.7%) among the treatments. Neither the time to estrus nor the duration of estrus were different (P > 0.10) among APRON, RAM or T-EWE groups (41.6 ± 3.8 vs 43.6 ± 3.6 vs 46.1 ± 3.6 h, respectively, and 26.5 ± 2.2 vs 24.8 ± 2.3 vs 30.5 ± 2.2 h, respectively). The time to LH surge was similar (P > 0.10) among APRON, RAM and T-EWE groups (51.2 ± 4.5 vs 51.2 ± 4.7 vs 52.7 ± 4.5 h, respectively). The magntude of the LH surge was similar (P > 0.10) in the T-EWE, APRON and RAM ewes (99.7 ± 4.9 vs 87.2 ± 4.9 vs 85.8 ± 5.0 ng/ml, respectively). The time from estrus to the LH surge was no different (P > 0.10) among APRON, RAM or T-EWE ewes (10.1 ± 2.2 vs 9.8 ± 2.3 vs 11.6 ± 2.3 h, respectively). These results show that the expression and duration of estrus are not influenced by different types of mating stimuli in hair sheep ewes. In addition, the timing and the magnitude of LH release does not appear to be influenced by mating stimuli around the time of estrus.

Summer Habitat Use by Mountain Sheep

Summer habitat use by mountain sheep (Ovis canadensis mexicana) was examined in the Pusch Ridge Wilderness (PRW), Santa Catalina Mountains, Arizona, during 1982 and 1983. Diurnal sheep activity was concentrated in areas 550 m of escape terrain. Sheep selected nonprecipitous open oak (Quercus spp.) woodland associations. Slopes of 59-79% and elevations of 1,098-1,341 m were selected on upper slopes of drainages or on the tops of ridges or mountains. Ewe-juvenile groups selected more precipitous areas than ram groups and mixed groups. Groups with lambs used steeper and lower areas than groups without lambs. J. WILDL. MANAGE. 50(2):331-336 Mountain sheep habitat in the PRW of the Santa Catalina Mountains near Tucson, Arizona, may be affected by extensive suburban development on privately owned land abutting the wilderness boundary. Development is 50.6 km of the most heavily used mountain sheep habitat. The impact of human encroachment on mountain sheep abundance, distribution, and habitat use should be monitored carefully. Our study provides information on mountain sheep habitat use prior to encroachment. Financial support was provided by the Estes Co. and the Univ. Arizona, School Renewable Nat. Resour. S. D. Seidler assisted in all phases of the fieldwork. S. W. Carothers, R. W. Mannan, J. E. Rodiek, W. W. Shaw, and V. C. Supplee provided ideas throughout the study and offered constructive comments on an earlier draft of this manuscript. J. C. deVos, Jr., S. R. Lawry, R. C. Miller, and R. J. Olding of the Ariz. Game and Fish Dep. and P. W. Karp and C. E. Kennedy of the U.S. For. Serv. provided technical assistance. B. D. Leopold and M. C. Wallace provided statistical and technical ad-

Mating performance of paddock-mated rams. I. Changes in mating performance, ejaculate characteristics and testicular size during the joining period

A series of field experiments was undertaken to examine the possible relationship between the major factors thought to influence the paddock-mating performance of rams (sperm producing capacity, sperm output and mating behaviour) and flock fertility. Also the effect of mating on these factors was examined. Six mating groups were used, four ram groups were subjected to conventional paddock-mating conditions, using paddocks ranging in size from 2.5 to 30 ha and were joined for 6 to 7 weeks to 110 (two rams), 112 (two rams), 204 (three rams) and 336 ewes (six rams) respectively at a rate of 7.6, 10.3, 6.3 and 6.5 g testicular tissue per ewe. Rams of the remaining two groups, of three rams each, were selected for High (High TV) and Low (Low TV) testicular volume and were joined to 152 and 150 ewes each at a rate of 5.5 and 4.1 g testicular tissue per ewe for 16 days, following which they were immediately rejoined with a second group of 140 ewes each for 34 days. In all groups the proportion of ewes mated during the first 17 days was high (87–92%); this level of sexual activity had no apparent adverse effect on the fertility of the rams as reflected by percentage of ewes returning to first service. Semen collections were taken from the Working rams and the Control rams prior to, during and after the joining period. Semen samples were evaluated for the ejaculate quantity parameters of volume, sperm density, and total number of sperm, and for the ejaculate quality parameters of motility score, % live sperm and % morphologically abnormal sperm. For the paddock mated rams, volume, density, and total sperm per ejaculate were high during the pre-joining period with mean values ranging from 0.79–1.10 ml, 3.16 · 10 9–4.25 · 10 9 sperm/ml and 3.59 · 10 9–4.09 · 10 9 sperm respectively. The values decreased to a stable minimum level during the peak mating period with mean values ranging from 0.35–0.49 ml, 0.97 · 10 9–1.29 · 10 9 sperm/ml and 0.37 · 10 9–0.56 · 10 9 sperm respectively, and increased to near pre-joining levels during the latter stages of the joining period. For all mated rams combined, there were no significant relationships between prejoining testicular size and ejaculate quantity characteristics recorded during the joining period. At male to female breeding ratios of 2.0% it does not seem warranted to select for increased testicular size prior to joining. The effects of mating on semen motility, % live sperm and % morphologically abnormal sperm were not as clear cut as those on ejaculate volume or density. Motility score for mated rams followed a pattern similar to that for ejaculate density, but no consistent pattern was observed in the percentages of live or abnormal sperm. The relationships between the characteristics of ejaculates collected during the period of high mating activity and flock fertility were not significant for individual semen characteristics or for all characteristics combined. Incorporating the estimated number of services per ewe did not significantly improve this relationship. Testicular volume and scrotal circumference decreased significantly to 56–86% and 80–92% of pre-joining levels respectively in all the mated ram groups excepting Low TV rams. The rate of decrease was linearly related to pre-joining testicular size of the rams and was not solely attributable to liveweight change. It was concluded that mating had a direct and adverse effect on the testicular size of rams which appears to be accelerated by the sudden decrease in liveweight often experienced by paddock-mated rams.

CIRCANNUAL CHANGES IN SERUM LEVELS OF PITUITARY HORMONES AND TESTOSTERONE AND IN TESTIS SIZE OF SEXUALLY ACTIVE AND INACTIVE ADULT RAMS

The influence of the social environment of adult rams on testicular function and the secretion of pituitary hormones was investigated between May 1978 and October 1979. Twelve rams, 3–6 yr of age, were penned in three groups of four, either as a sexually inactive all-male group or as sexually active groups adjacent to or together with ovariectomized ewes that were hormonally induced into estrus every 10 days. At approximately monthly intervals measurements of testis size were recorded and rams were bled by venepuncture from the jugular vein at 20-min intervals for 8 h (0900–1700 h). Sera were assayed for luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL) and testosterone. Since seasonal changes in testicular and endocrine characteristics for the sexually active groups were similar, data for these groups were combined. Differences in the circannual testicular rhythm were not observed between ram groups until the onset of the second breeding season; at this time (August 1979), sexually active rams had significantly (P &lt; 0.05) higher scrotal circumference measurements (36.0 ± 0.9 vs. 32.2 ± 1.0 cm) and circulating testosterone levels (10.7 ± 1.6 vs. 6.7 ± 1.5 ng/mL), and significantly (P &lt; 0.05) lower LH levels (0.75 ± 0.10 vs. 2.04 ± 0.40 ng/mL) than sexually inactive rams. The increase in rate of testicular redevelopment for sexually active rams during late summer was not preceded by significantly (P &gt; 0.05) higher seasonal elevations in circulating LH and FSH levels, although PRL levels in May through July were only 50% of those observed for the sexually inactive rams. Sexually active rams also exhibited significant (P &lt; 0.01) increases in LH and testosterone secretion in the nonbreeding season when ewes were sexually receptive. Ejaculation frequency during a 4-h test period at the conclusion of the study was similar for both groups of rams. Data indicate that long-term exposure of adult rams to estrual ewes results in an increase in rate of testicular redevelopment during the summer in preparation for the fall breeding season. Key words: Circannual changes, pituitary hormones, testosterone, testis, mating, ram

INFLUENCE OF AGE AND BREED ON CIRCULATING LH, FSH AND TESTOSTERONE LEVELS IN THE RAM

Possible age and breed differences in circulating levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone in the ram were investigated. In exp. 1, blood was collected from a group of 28 rams of various ages and breeds by venepuncture from the jugular vein at 20-min intervals for an 8-h period (May). Comparison of mean serum hormone concentrations for postpubertal Finnish Landrace (Finn), Suffolk and Managra Synthetic (Line M) rams did not reveal significant (P &gt; 0.10) breed differences. However, when rams of the three breeds were categorized by age, the mean (±SE) LH levels in lambs (n = 8), yearling (n = 12) and adult (n = 8) animals were 2.1 ± 0.4, 1.1 ± 0.2 and 0.5 ± 0.1 ng/mL, respectively; the significant decrease (P &lt; 0.05) in LH levels in adult vs. yearling rams was due to fewer and smaller LH releases. Mean testosterone levels averaged 1.3 ± 0.2, 2.8 ± 0.4 and 2.4 ± 0.3 ng/mL for the lamb, yearling and adult ram groups, respectively. FSH levels were similar for all age groups. In exp. 2, a series of blood samples were collected from 3-mo-old Finn (n = 6) and Suffolk/Line-M crossbred (n = 6) rams in October. In comparison with crossbred rams, rams of the more prolific Finn breed exhibited substantially higher mean levels of LH (1.0 ± 0.2 vs. 0.4 ± 0.2 ng/mL; P &lt; 0.10), FSH (250 ± 26 vs. 121 ± 16 ng/mL; P &lt; 0.01) and testosterone (2.8 ± 0.9 vs. 0.4 ± 0.1 ng/mL; P &lt; 0.05); higher LH and testosterone in Finn rams were associated with larger and/or more frequent elevations in the level of these hormones during the 8-h bleeding period. Results of this study seem to indicate (1) age-associated differences in the pattern of LH release in adult rams in the spring; and (2) that breed differences in blood reproductive hormone levels in postpubertal rams are not significant in the spring, but levels in 3-mo-old rams differ during the fall months according to genotype. Key words: Age, breed, gonadotropins, testosterone, serum, ram

Winter Habitat Selection by Mountain Sheep

During winter 1975-76, 197 observations of groups of wintering mountain sheep (Ovis canadensis) provided data on habitat selection near Thompson Falls in northwestern Montana. Sheep selected against upper elevations, drainage bottoms, upper slopes on ridges, areas with a slope steepness of 10-35%, east and southeast aspects, areas greater than 320 m from steep terrain, and closed forests. Preferences (P < 0.1) were shown for cliffs, areas with slope steepness greater than 80% and closer than 320 m to steep terrain or cliffs, and shrubland-grassland and open forest vegetation types. Adult ram groups were observed at higher elevations (P < 0.05) than ewe-juvenile or young ram groups. Sheep apparently sought warmer elevations throughout the winter. There was general agreement on the selection of habitat as estimated from direct observations and fecal group counts. J. WILDL. MANAGE. 46(2):359-366 The importance of winter range in the welfare of mountain sheep has been expressed by several investigators (Honess and Frost 1942, Smith 1954, Buechner 1960, Oldemeyer et al. 1971, Rutherford 1972). However, the mixture of meterological, topographic, and biotic variables which provide adequate winter range has received limited study. Knowledge of variables selected would provide criteria for selecting transplant sites containing adequate winter range. Rutherford (1972) observed that evaluation of potential transplant sites is complicated because mountain sheep are selective and their habitat requirements are not well understood. Our objectives were to quantitatively describe the habitat used by mountain sheep in winter, identify the selection of sites among those available, and evaluate the preference of mountain sheep for biotic and abiotic environmental variables on winter range. STUDY AREA The Thompson Falls mountain sheep winter range is along the southeast end of the Cabinet Mountains just north of the Clark Fork River midway between Plains and Thompson Falls, Montana (Brown 1974). Poorly developed soils and numerous talus slopes emanating from rugged crags of exposed bedrock cover much of the 1,660-ha study area. The valley floor is at 730 m, with the mountains rising to over 1,800 m in less than 2.4 km with south-southwest exposures predominating. Climate is Pacific maritime and January is the coldest month with temperatures averaging -3.1 C (range -37.8 to 13.3 C). Mean annual precipitation is 57.2 cm with greatest amounts falling during November-January. The winter of 1975-76 was slightly milder than average in severity. Plant communities were bryoids on talus slopes, shrubland-grassland complexes, low to mid-elevation Douglas-fir (Pseudotsuga menziesii)-common snowberry (Symphoricarpos albus) communities, and higher Douglas-fir-mallow ninebark (Physocarpus malvaceus) communities. Major grass species present were bluebunch wheatgrass (Agropyron spicatum), pine reedgrass (Calamagros1 Funded by the National Rifle Association, Wildlife Management Institute, Montana Forest and Conservation Experiment Station, and Montana Cooperative Wildlife Research Unit. 2 Present address: Soil Conservation Service, Roseburg, OR 97470. J. Wildl. Manage. 46(2):1982 359 This content downloaded from 207.46.13.111 on Sun, 22 May 2016 04:21:07 UTC All use subject to http://about.jstor.org/terms 360 WINTER HABITAT SELECTION BY MOUNTAIN SHEEP' Tilton and Willard tis rubescens), and rough fescue (Festuca scabrella). Other important shrubs were Rocky Mountain maple (Acer glabrum), Saskatoon serviceberry (Amelanchier alnifolia), snowbrush ceanothus (Ceanothus velutinus), Lewis mockorange (Philadelphus lewisii), antelope bitterbrush (Purshia tridentata), and common chokecherry (Prunus virginiana).

PARASITES FROM CALIFORNIA BIGHORN SHEEP IN SOUTHERN BRITISH COLUMBIA

Seven nematode and two tick species were found during postmortem examination of two adult California bighorns at the Ashnola River, British Columbia. Another nematode and a coccidium were extracted from fecal material by zinc sulphate centrifugal flotation. Protostrongylin lungworm larvae were isolated by the Baermann technique from 80% of 101 fresh bighorn droppings. Little variation in frequency of infection with lungworm larvae was noted among yearling, ewe, and ram groups, but lambs appeared to be freer of the parasite than older animals. Both lambs and yearlings appeared to pass considerably fewer lungworm larvae in their droppings than older animals. The earliest date of collection of an infected lamb dropping was July 6, when the lamb was about 8 weeks old. The bighorn sheep is reported as a new host of the abomasal worm Ostertagia ostertagi (Stiles 1892).