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The influence of human harvest on evolution of secondary sexual characteristics has implications for sustainable management of wildlife populations. The phenotypic consequences of selectively removing males with large horns or antlers from ungulate populations have been a topic of heightened concern in recent years. Harvest can affect size of horn‐like structures in two ways: (a) shifting age structure toward younger age classes, which can reduce the mean size of horn‐like structures, or (b) selecting against genes that produce large, fast‐growing males. We evaluated effects of age, climatic and forage conditions, and metrics of harvest on horn size and growth of mountain sheep (Ovis canadensis ssp.) in 72 hunt areas across North America from 1981 to 2016. In 50% of hunt areas, changes in mean horn size during the study period were related to changes in age structure of harvested sheep. Environmental conditions explained directional changes in horn growth in 28% of hunt areas, 7% of which did not exhibit change before accounting for effects of the environment. After accounting for age and environment, horn size of mountain sheep was stable or increasing in the majority (~78%) of hunt areas. Age‐specific horn size declined in 44% of hunt areas where harvest was regulated solely by morphological criteria, which supports the notion that harvest practices that are simultaneously selective and intensive might lead to changes in horn growth. Nevertheless, phenotypic consequences are not a foregone conclusion in the face of selective harvest; over half of the hunt areas with highly selective and intensive harvest did not exhibit age‐specific declines in horn size. Our results demonstrate that while harvest regimes are an important consideration, horn growth of harvested male mountain sheep has remained largely stable, indicating that changes in horn growth patterns are an unlikely consequence of harvest across most of North America.

Horns, antlers, and other horn-like structures are products of sexual selection, confer reproductive advantages, and are heritable and honest indicators of individual quality. In addition to serving key biological functions, horns and antlers garner societal interest that, when combined with the powerful motivation to acquire trophy animals, likely has spawned a growing hornographic culture fixated on males with exceptional horn-like structures. The concern that harvest of large, fast-growing males may cause evolutionary change to the very trait being sought has been the source of controversy in the popular and scientific literature over the past 2 decades. Mountain sheep (i.e., bighorn and thinhorn; Ovis spp.), possibly the only large ungulates in North America managed almost exclusively as trophy species throughout their ranges, embody this controversy, which has led to polarizing views among scientists and stakeholders as to how mountain sheep should be managed. Our goal in this commentary was to discuss the relative contributions of the key ecological and intrinsic factors that influence horn growth, how those factors might interact with harvest strategies, and identify what determinants of horn size are most amenable to management and most effective in achieving desired outcomes. Despite repeated results demonstrating that age or nutrition frequently override genetic contributions to size of horns, attention has been given to the role of genetics and its relationship to harvest of mountain sheep. Given the hyperbole surrounding trophy management and big horns, we suggest the importance of females in the management of mountain sheep has been largely forgotten. Maternal condition can instigate life-long effects on size and growth of males (via maternal effects), and abundance of females, in turn, affects nutritional limitation within populations through density-dependent feedbacks. If production of males with large horns is an objective, we contend that management programs should, integrate monitoring of nutritional status of populations, and where evidence indicates nutritional limitation through density dependence, seek to regulate abundance and per capita nutrition via harvest of females. We propose that extrinsic regulation (i.e., removal by harvest or translocation) is the most effective way to manage per capita availability of forage resources and, thus, nutritional limitation on growth of males. Not only can female harvest improve growth in body size and horns of males through enhanced nutrition of growing males and their mothers, such management also 1) may yield a nutritional buffer against environmental stochasticity and erratic population fluctuations, 2) be employed in areas where other management alternatives such as habitat manipulation may not be feasible, 3) may reduce frequency or magnitude of epizootic die-offs, and 4) will increase hunter opportunity and involvement in management. Ultimately, we call for greater recognition of the pervasive role of the ewe, and other female ungulates, in the production of trophy males, and that accordingly, females be better integrated into harvest and management programs. © 2017 The Wildlife Society.

Information about the people recorded in 813–14 on the estate of St Victor de Marseilles shows that although considered to belong to the monastery they were an independent peasant class. Family size and structure varied: some farms were run by the labour of the family which included unmarried sons and ‘married-in’ sons-in-law; other farmers employed living-in servants in husbandry. The mountain sheep farms had large groups of unmarried young people. Inheritance systems ensured that the peasant family property remained intact over the generations and provided support for unmarried sons who remained to work there.

Different ungulate species that co-occur over evolutionary time have been hypothesized to develop mechanisms to limit the degree to which they directly compete for the same limited resources (i.e. resource partitioning). In situations where an exotic ungulate has been recently introduced to a system, resource partitioning has not likely developed; this appears to be the situation between introduced feral ass Equus asinus and indigenous mountain sheep Ovis canadensis in the Sonoran Desert of southeastern California, USA. We analysed data from aerial surveys conducted during 1993–2003 to look for evidence of an effect of feral ass abundance on mountain sheep demography. After controlling for the influence of forage availability via rainfall, we found no evidence of relationship between an index of feral ass abundance and indices of reproduction or recruitment in mountain sheep (P≥0.360). However, we found strong evidence for an effect on indices of sheep abundance and population rate of change. The...

The separation of populations by ice sheets into large refugia can account for much of the genetic diversity found in present day populations. The evolutionary implications of small glacial refugia have not been as thoroughly explored. To examine refugial origins of North American mountain sheep Ovis spp., we analyzed a 604 bp portion of the mitochondrial DNA (mtDNA) control region from 223 O. dalli and O. canadensis. Major refugia were identified in eastern Beringia and southern North America, and we found evidence for two smaller refugia situated between the Laurentide and Cordilleran glaciers. Our results are the first to demonstrate support for survival of any organism in the latter two refugia. These refugia also appear to have conserved a genetic signal that confirms past hybridization of O. dalli and O. canadensis.

Turner et al. (2004) developed a habitat selection model for a population of desert bighorn sheep (Ovis canadensis) in the Peninsular Ranges of southern California that is listed as a threatened and endangered population by the state of California and the federal government, respectively. We are concerned that the recent publication of an article by Turner et al. (2004) could be detrimental to the management and recovery of bighorn sheep in the Peninsular Ranges because it lends credibility to a flawed analysis of bighorn sheep habitatuse patterns. The model attempts to extrapolate conclusions from a limited subset of bighorn sheep data that is not representative of the study area and was not gathered in a manner conducive to the analysis methods used by the authors. The authors classified habitat pixels as “active” or “inactive” based on the presence-absence of bighorn sheep observations without considering monitoring intensity. Turner et al. (2004) also failed to consider the implications of basing their model almost entirely on a bighorn sheep subpopulation known to have atypical habitat selection patterns. This subpopulation in the northwestern Santa Rosa Mountains frequently used food and water sources within hillside urban areas. Because the Turner et al. (2004) model was developed using data primarily from this atypical subpopulation, the model has low external validity and is unlikely to accurately predict habitat selection by other bighorn sheep subpopulations in the Peninsular Ranges. Furthermore, with the NW sub-population used in model development now excluded from urban areas, the Turner et al. (2004) model is unlikely to accurately predict habitat selection patterns of even this sub-population. We suggest the Turner et al. (2004) model is at best only applicable to this subpopulation between the years 1994–1998.

Wildlife Society Bulletin 2004, 32(3):987–991 Peer edited Investigators have used marking collars and telemetry collars to enhance knowledge about movements of ungulates for many decades. Technological advances have provided increasingly dependable and sophisticated equipment (Fancy et al. 1988; Mourao and Merdi 2002), and methods of collar attachment have evolved substantially, particularly with respect to juvenile ungulates (Smith et al. 1998, Bleich and Pierce 1999). Nevertheless, recent observations of mule deer (Odocoileus hemionus) and mountain sheep (Ovis canadensis) fitted with telemetry collars that incorporate Global Positioning Systems (GPS) and other satellite technology indicate those collars may cause injury to the study animal. The intent of investigators should be to minimize injuries and effects of marking on the behavior of animals (White and Garrott 1990), but our observations suggest lack of compliance in some cases with existing guidelines (Committee on Acceptable Field Methods 1987, Institutional Animal Use and Care Committee [Powell and Proulx 2003]). We placed collars incorporating GPS receivers and very high frequency (VHF) transmitters (Telonics, Mesa, Ariz.; and Posrec, TVP Positioning AB, Lindesberg, Sweden) on mule deer and mountain sheep. We collared female deer in Round Valley, Inyo, and Mono counties, California during March (n=12) and November 2002 (n=1). Four of 6 deer recaptured in November 2002, 2 of 3 recaptured in January 2003, and 2 of 2 recaptured in March 2003 (1 of which was collared in November 2002) exhibited all stages of ulcer formation except bone involvement. Patchy alopecia, nonblanchable erythema, induration, and edema of the intact skin surrounding ulceration were present. In some deer there was only partial skin loss and the ulcers were superficial; others revealed skin loss to the subcutaneous layer resembling a deep abrasion. The most severely affected deer had skin loss with extensive destruction of muscle on the dorsal aspect of the neck (Figure 1). Affected areas varied from 4–100 cm2 and extended from 4–8 cm distal of the occiput or jaw to the mid-cervical region on the dorsal and ventral surfaces of the neck, respectively; lateral surfaces were not involved. We removed collars from the 6 deer that exhibited lesions in November 2002 and January 2003. Three of those animals were recaptured in March 2003, and all lesions had healed completely. As part of long-term ecological investigations (Pierce et al. 2000a,b), we placed VHF collars from 3 manufacturers on 113 juvenile ( 500 adult mule deer of both sexes since 1992. We From the Field: Neck lesions in ungulates from collars incorporating satellite technology

Morphologische Ahnlichkeiten zwischen Hausschafrassen und bestimmten Subspezies des Ovis ammon L. 1758 konnen nicht als zwingender Beweis einer Domestikation der betreffenden Unterart gelten, da Einkreuzungen fremder Wildschafformen in Hausschafe anderer genetischer Herkunft gleichfalls als Ursache von Ubereinstimmungen anerkannt werden mussen. Das Heranziehen des maternal vererbten mitochondrialen Genoms eroffnet jedoch die Moglichkeit, heutige Schafrassen – trotz domestikationsbedingter morphologischer Veranderungen und Einkreuzungen u. a. m. –uber zahlreiche Generationen bis zu domestizierten Wildschafformen zuruckzuverfolgen, sofern diese nicht bereits ausgestorben sind. Mittels haplogruppenspezifischen polymorphen HinfI-Fragmenten von mtDNA und Proteinpolymorphismen bei Tieren verschiedener Bergschafrassen, die maternal als Torfschaf-Abkommlinge gelten, sowie auch von zur Gruppe der Zaupel gehorenden Waldschafen, sollte geklart werden, ob der in Europa vorwiegend auftretende Haupt-mtDNA-Haplotyp B mit dem altesten Hausschaf in Europa, dem Torfschaf (Ovis aries palustris RUTIMEYER 1862) in Zusammenhang gebracht werden kann. Die Stichproben aus Steinschafbestanden slowenischer und bayerischer Herkunft, weisen und braunen Bergschafen, Brillenschafen aus Bayern und Villnosserschafen weisen einheitlich den Haupt-mtDNA-Haplotyp B auf, wie dies auch bei einem zusatzlich untersuchten Bergamaskerbock der Fall ist. Allerdings wurde in der Waldschafgruppe bei mehr als der Halfte der Tiere dieser Stichprobe der Typ A festgestellt, was zeigt, das nicht alle Zaupelschaf – Nachkommen auf die gleiche Wildschaf – Unterart wie die Steinschaf – Nachkommen zuruckgefuhrt werden konnen. Im Hamoglobin (HBB) kommen die Varianten HBBA und HBBB in allen untersuchten Rassen in ausgeglichener Frequenz vor, wobei beim braunen Bergschaf die Frequenz von HBBA (0.857) erhoht ist. Bayerische Steinschafe waren am CA2-Locus, Waldschafe am GC-Locus polymorph. Im Transferrin wurden deutliche Unterschiede im Vorkommen und in der Frequenz der einzelnen Allele zwischen den Populationen nachgewiesen. Zusammenhange zwischen Torfschaf, Kupferschaf, Steinschaf, Zaupelschaf, Bergamasker und ‘europaischem’ Mufflon werden diskutiert. Der Weg zum domestizierten Vorfahren der meisten europaischen Hausschafe fuhrt jedoch uber das kleine Torfschaf zu einer noch nicht ermittelten Ovis ammon– Subspezies in Asien. Biochemical polymorphisms and major mtDNA haplotypes in Bergschaf breeds and Waldschaf as contribution to descent of domestic sheep Morphological similarities between domestic sheep and certain subspecies of Ovis ammon L. 1758 are not necessarily proof of the domestication of a specific subspecies, as crossbreeding of foreign wild sheep populations of different genetic origin with domestic sheep could have led to observed similarities. The maternal inherited mitochondrial genome offers the opportunity to trace modern domestic sheep breeds across numerous generations to presumptive wild ancestors regardless of domestication induced morphological changes and crossbreeding, etc. An investigation based on haplotype specific HinfI – mtDNA fragments and protein polymorphisms in different mountain sheep breeds thought to represent maternal descendants of the Torfschaf as well as in the Waldschaf breed, which belongs to the Zaupel group, were used to help clarify if the major European mtDNA haplotype B was associated with the Torfschaf (Ovis aries palustris RUTIMEYER 1862), the oldest domesticated sheep in Europe. Samples derived from Steinschaf of the Slovenian and Bavarian type, white and brown varieties of Bergschaf, Brillenschafe from Bavaria and Villnosserschafe showed haplotype B. A single investigated ram of the Bergamasker breed was of the same haplotype. mtDNA haplotype A was detected in more than 50% of the Waldschaf animals. This demonstrates that not all sheep breeds derived from Zaupelschaf are descendants of the same wild ancestor. Within haemoglobin (HBB) the variants HBBA and HBBB occur in a well balanced pattern in all breeds investigated, while the frequency of HBBA was high (0.857) in the brown Bergschaf. Steinschafe of Bavarian type were polymorphic at the CA2-locus and Waldschafe at the GC-locus. At the transferrin locus, differences in the occurrence and frequency of the different alleles could be demonstrated between populations. Relationships between Torfschaf, Kupferschaf, Steinschaf, Zaupelschaf, Bergamasker and European Mouflon are discussed. It is likely that the domesticated ancestors of most European sheep can be traced from the Torfschaf to an as yet unknown wild sheep (Ovis ammon) subspecies in Asia.

Bighorn sheep (Ovis canadensis) once were ubiquitous in large areas, including lands now contained in the national parks of the Intermountain and Colorado Plateau regions of the United States. Due to catastrophic declines in the late 1800s and early 1900s, most extant populations now occur as small, isolated groups with a highly fragmented distribution. Three different subspecies of bighorn sheep were extirpated from 14 of 18 areas that are now managed by the National Park Service. We describe an eight-year plan to restore bighorn sheep to currently suitable historic habitats in the national parks within a six-state intermountain region of the western United States, 1991-1998. A seven-point program was recommended for each park unit that included: (1) survey the existing populations; (2) conduct a GIS-based habitat assessment to identify suitable habitat; (3) convene scientific advisory panels to review results of habitat assessment; (4) convene interagency panels to discuss metapopulation management and to plan the restoration(s); (5) draft interagency restoration and management plans; (6) conduct translocation(s); and (7) monitor the populations. We evaluated 38,781 km 2 of area; 32% (12,329 km 2 ) was potential habitat for bighorn sheep. The scientific advisory panels and the GIS modeling recommended bighorn restoration on 73 sites within these areas. By 1996, 36 of these sites (2,647 km 2 or 22% of the entire suitable area) were inhabited by bighorn sheep. By 1999, the translocated animals increased 25%, and restoration efforts will continue in many of the remaining sites.

Predicting extinction probabilities for populations of various sizes has been a primary focus of conservation biology. Berger (1990) presented an empirically based extinction model for mountain sheep (Ovis canadensis) populations in five southwestern states that predicted disappearance within 50 years of all populations estimated to number 50 sheep or fewer, but essentially no loss in that time period of populations estimated at over 100. The majority of the 122 populations he used in his analysis were from California, but his analysis did not use many of the historical size estimates for these populations. I tested Berger’s (1990) model using the complete data set from California and found—contrary to his results—that, for all size classes of population estimates, at least 61% of the populations persisted for 50 years. Also, two predictions from Berger’s model were not consistent with the data from California: (1) 10 populations have increased from estimates of 50 or fewer animals to over 100, whereas the Berger model predicted that these populations would only decline to extinction; and (2) of 27 extant populations with long enough records, 85% were estimated at least 50 years ago to be 50 individuals or fewer and should therefore be extinct by now. Berger’s model has now failed tests in three states and therefore does not support the strong population size effect on extinction probability that it first appeared to provide, and it may serve conservation poorly through misdirected effort if it is used as the basis for setting policies or taking actions. Resumen: La prediccion de las probabilidades de extincion de poblaciones de varios tamanos ha sido el enfoque principal de la biologia de la conservacion. Berger (1990) presento un modelo de extincion con bases empiricas para poblaciones del borrego de montana (Ovis canadensis) en cinco estados del suroeste y que eran predecidas a desaparecer dentro de 50 anos en todas las poblaciones estimadas con ≤50 borregos, pero escencialmente no se predecian perdidas en poblaciones> 100 para ese tiempo. La mayoria de las 122 poblaciones que el uso en su analisis fueron de California, pero su analisis no uso muchas de las estimaciones historicas de tamano para estas poblaciones. Probe el modelo de Berger (1990) utilizando un juego de datos completos de California y encontre que contrariamente a sus resultados, la mayoria de las clases de tamano estimadas para por lo menos un 62% de las poblaciones persistio por 50 anos. Adicionalmente, dos predicciones del modelo de Berger (1990) no fueron consistentes con los datos de California: (1) 10 poblaciones han incrementado de un estimado de 50 o menos animales a mas de 100, mientras que el modelo de Berger predecia que estas poblaciones unicamente declinarian hasta extinguirse, (2) de las 27 poblaciones existentes con datos historicos suficientes, un 85% tuvo estimaciones de por lo menos 50 anos y tuvieron ≤50 individuos por lo que deberian haberse extinguido a la fecha. El modelo de Berger (1990) ha fallado las pruebas en tres estados y por lo tanto no soporta un efecto fuerte del tamano poblacional en la estimacion de la probabilidad de extincion, al menos como lo aparenta en un principio y podria servir pobremente a la conservacion mediante una guia incorrecta de esfuerzos si es usado como base para determinar politicas o para llevar a cabo acciones.

Longitudinal studies of survival are valuable because age-specific survival affects population dynamics and the evolution of several life history traits. We used capture–mark–recapture models to assess the relationship between survival and sex, age, population, year of study, disease, winter weather, and population density in two populations of bighorn sheep (Ovis canadensis) in Alberta, Canada. The Ram Mountain population, monitored for 20 yr, more than doubled in density; the Sheep River population, monitored for 13 yr, experienced a pneumonia epizootic. Yearling survival varied among years and was lower than that of older sheep of the same sex, except for yearling males at Ram Mountain. Yearling females at Ram Mountain were the only sex-age class exhibiting density dependence in survival. Senescence was evident for both sexes in both populations. Female survival from age 2 to age 7 was very high in both populations, but males aged 2 and 3 yr enjoyed better survival than males aged 4–6 yr. Our data support the suggestion that where hunters remove many males older than 5 yr of age, the natural mortality of males increases at 3–5 yr, possibly because young males suffer a mortality cost of participating in rutting activity. The decline in survival for sheep older than 7 yr was greater for males than for females. Survival was lower for males than for females, both among prime-aged sheep (0.896 vs. 0.939 at Sheep River; 0.837 vs. 0.945 at Ram Mountain) and among older sheep (0.777 vs. 0.859 at Sheep River; 0.624 vs. 0.850 at Ram Mountain), but not among yearlings. Survival of sheep aged 2–7 yr was not significantly different between the two populations. Winter weather did not affect survival. Survival of sheep 2 yr of age and older did not vary significantly between years, except at Sheep River where survival of prime-aged sheep of both sexes was lower in the year of the pneumonia epizootic. Studies of survival of mountain sheep based upon skull collections may have overestimated survival of young rams. Our results underline the need for accurate information on age-specific survival.

In the south-western United States and Mexico, mountain sheep were found to have low levels of mtDNA sequence divergence among haplotypes and low overall nucleotide diversity. Potential causes for this low diversity are discussed. Significant differences in mtDNA haplotype distributions over short distances and high values of NST on a local scale appear to be a result of the tendency of female mountain sheep to disperse less frequently and over shorter distances than males. A lack of concordance between mtDNA haplotype distributions and assumed subspecies boundaries suggest that some taxonomic labels need to be revised.

Large interarcual spaces have been described between the arcus vertebrae C5/C6 and C6/C7 in the cervical vertebral column of Nubian goats. This aperture enables direct access to spinal cord and rootlets without the need to perform a hemilaminectomy. The present study was performed in order to determine whether these large interarcual spaces can also be found in the vertebral column of the Tyrolean mountain sheep, as this small ruminant, which is anatomically very similar to the Nubian goat, is frequently used for experimental purposes at the Surgical University Clinic in Austria. The carcasses of 10 sheep (six females, four males; range of age: 2.5-6 years, range of weight: 52-89 kg) were dissected and the vertebral column was exposed. All 10 sheep showed elliptic openings between the fourth cervical and the first thoracal vertebrae. Three sheep had additional openings between the first and the second thoracal vertebrae. All openings were covered solitarily by the ligamentum flavum and under this ligamentum lay the spinal cord without any further osseous or ligamentous protection. These findings are not mentioned in the common textbooks of veterinary anatomy and deserve attention, as they can be a step forward towards non-traumatic experimental surgery on the spinal cord.

Mountain sheep (Ovis canadensis) are closely associated with steep, mountainous, open terrain. Their habitat consequently occurs in a naturally fragmented pattern, often with substantial expanses of unsuitable habitat between suitable patches; the sheep have been noted to be slow colonizers of vacant suitable habitat. As a result, resource managers have focused on (1) conserving “traditional” mountainous habitats, and (2) forced colonization through reintroduction. Telemetry studies in desert habitats have recorded more intermountain movement by desert sheep than was previously thought to OCCUT. Given the heretofore unrecognized vagility of mountain sheep, we argue that existing corridors of “nontraditional” habitat connecting mountain ranges be given adequate conservation consideration. Additionally, small areas of mountainous habitat that an? not permanently occupied but that may serve as “stepping stones” within such corridors must be recognized for their potential importance to relatively isolated populations of mountain sheep. We discuss the potential importance of such corridors to other large, vagile species. Resumen: Los borregos cimarrones (Ovis canadensis) exhi-ben una asociacion cercana con terrenos montanosos escar-pados y abiertos. En consecuencia, su habitat ocurre en un patron naturalmente fragmentado, frecuentemente con grandes extensiones de habitat impropio separando las areas apropiadas; y se ha notado gue los borregos cimarrones son lentos en colonizar habitat apropiado vacante. Como resultado de estes observaciones, gerentes de recursos naturales ban enfocado su atencion en (1) constrvacion de habitat montanoso “tradicional” y (2) colonizacion forzado por reintroduccion. Estudios telemetricos en habitates desiertos ban demostrado mas movimiento entre sierras que antes se creia que ocurria. Dado la tendencia de vagar basta abora no reconocido de los borregos cimarrones, proponemos que corredores actuales de habitat no tradicional que conectan sierras merecen consideracion adecuada para consmacion. Ademas, se debe reconocer la importancia para poblaciones relativamente aisladas de los borregos cimarrones de areas pequenas de habitat montanoso que, aunque no ocupadas de manera permanente, pueden facilitar el movimiento de los borregos cimarrones dentro de dichos corredores. Se senala la importancia de estos cowedores para ohos especies errantes grandes.

SYNOPSIS Total numbers, generic distribution and percentage species distribution were determined for the ciliate protozoa in rumen contents obtained from Alaskan moose (Alces americana), musk-ox (Ovibos moschatus) and Dall mountain sheep (Ovis dalli). The musk-ox has a fauna somewhat similar to that previously observed in reindeer and caribou. In contrast, only protozoa in the genus Entodinium were observed in moose, while Dall mountain sheep have a fauna unique among Alaskan ruminants studied to date. Other than Entodinium exiguum which was common to all animals, only 2 additional species of Entodinium, observed in the moose and musk-ox, occurred in more than one animal species. Four new species of protozoa are described, Entodinium dalli sp.n., Entodinium constrictum sp.n. and Polyplastron alaskum sp.n. from the Dall mountain sheep and Entodinium alces sp.n. from moose.

In proportion to body size, North American wild sheep (Ovis canadensis and Ovis dalli) carry the largest horns among ruminants. Their horns have been recorded as exceeding 51 inches (130 cm.) in length, and 16 inches (40.6 cm.) in circumference at the base (Anonymous, 1964). Old males may bear eight to twelve per cent of their body weight as horns. The horns of rams grow substantially in length and mass each year. This increase is greatest in the early years of life and smallest in later years. The horns of females remain quite small throughout life and rarely exceed nine inches (23 cm.) in length. The huge horns of rams invite enquiry as to what selection processes brought about and retain such disproportionate organs. Several functions can be proposed for ram horns. Horns act as weapons.-This implies that horns can inflict damage on opponents when used in fighting. This I have found. The tiny horns of mountain goat (Oreamnos), however, also serve as weapons (Geist, 1964). Hence this proposed function alone explains little about the evolution of sheep horns. Horns act as a shield.-During fighting rams attempt to catch the opponents' head blows with their horns (Fig. 1). There is little doubt that sheep horns function in this manner. Other bovids, however, also attempt to catch an opponent's attack with their horns, i.e., Bos and Bison. These cattle carry only small, curved horns. Again, this function explains by itself little about the evolution of mountain sheep horns. Horns act as shock absorbers.-During their frequent social interactions, rams collide head on. They may run on their hindlegs at each other and then jump into the clash. Since the rams may weigh about 220--250 pounds each, the collisions must be frightful. It appears quite reasonable hence, that the heavy horns function in absorbing the heavy impact. This appearance is deceptive. A number of Artiodactyla clash head on during fighting, or deal out blows with their heads. None carry horns to match those of sheep males. Though female sheep fight very similar to rams, they carry only tiny horns. The wart hogs (Phacochoerus) and giant forest hogs (Hylockoerus) in fighting clash head on after a run at each other (Mohr, 1960; Fradrich, 1965). They possess no horns at all. Bison bulls may clash head on with considerable force (McHugh, 1958). They have only tiny horns. Giraffes (Giraffa) deal out severe blows with their heads, but carry only little ossicones on the skull. All these species (including sheep of both sexes) possess however one feature in common. They have a pneumated skull with a double roof of bone over the brain. Since there is no correlation between horn size and the mode of fighting: I reject the "shock-absorption" function. Horns act as display organs.-This is an old, but unverified concept of obscure origin. Beninde (1937) stated it clearly. He proposed that large-antlered deer could intimidate small-antlered opponents with their horn size, and hence gain social advantages without fighting. This hypothesis was never carried through to its various logical conclusions and hence never verified or rejected. If the horns of mountain sheep have been selected for as display or intimidation organs, then the following predictions must be inherent