Desert bighorn sheep (Ovis canadensis) populations often occur in remote areas at low densities, leading to gaps in knowledge of life history. In November 2011, we translocated 11 female desert bighorn sheep from the Fra Cristobal Mountains and 9 from Red Rock Wildlife Management Area (RRWMA) to the Peloncillo Mountains in southwestern New Mexico. In December 2012, we captured 21 adult females in the Peloncillo Mountains, 14 of which were recaptured from 2011. We fitted each animal with a very high frequency (VHF) collar and vaginal implant transmitter (VIT) to monitor for parturition. We captured 26 lambs (5 females, 7 males in 2012; 7 males, 7 females in 2013), recorded morphometric measurements and fitted lambs with VHF collars to monitor survival. Over the study, 14 lambs died, with 12 mortalities from predation, one from abandonment, and one from unknown causes. Lambing season was protracted over 3-4 months and survival was unrelated to birth timing. Body mass differences between sex varied by year, suggesting a connection to annual climate. Because most studies focus on captive animals with access to supplemental food, captive lambs may not be representative of free-ranging populations. Thus, we investigated morphological trends in a free-ranging population.

Abundance estimates inform ungulate management and recovery efforts. Yet effective and affordable estimation techniques remain absent for most ungulates lacking identifiable marks and inhabiting rugged or highly vegetated terrain. Methods using N-mixture models with camera trap imagery form an appealing solution but remain unvalidated. We assess this method using populations of desert bighorn sheep (DBS; Ovis canadensis) in New Mexico, USA, plus bison (Bison bison bison) and Texas longhorn cattle (Bos taurus taurus) in Oklahoma, USA, by calculating and comparing abundance estimates to censused values. We parsed data by 3 and 7-day intervals, using images filtered or unfiltered, and collected with motion detection or timed camera settings. We employed priors informed by subject matter experts (SME) and calculated using detection-nondetection methods. Abundance estimates from filtered images captured by motion detection in 3-day intervals included the censused value across all seasons for adult DBS, rams and ewes, indicating “best practices”. This “best practices” method also captured censused values for population estimates of bison (detection-nondetection) and cattle with both priors. Our assessment validates the use of N-mixture with camera trap imagery, while presenting sampling approaches, data handling procedures and model calibration to estimate wildlife population sizes more appropriately and accurately.

With most of the world's Caprinae taxa threatened with extinction, the IUCN appeals to the development of simple and affordable sampling methods that will produce credible abundance and distribution data for helping conserve these species inhabiting remote areas. Traditional sampling approaches, like aerial sampling or mark-capture-recapture, can generate bias by failing to meet sampling assumptions, or by incurring too much cost and logistical burden for most projects to address them. Therefore, we met the IUCN's challenge by testing a sampling technique that leverages imagery from camera traps with conventional distance sampling, validating its operability in mountainous topography by comparing results to known abundances. Our project occurred within a captive facility housing a wild population of desert bighorn sheep (Ovis canadensis) in the Chihuahuan desert of New Mexico, which is censused yearly. True abundance was always within our 90% confidence bounds, and the mean abundance estimates were within 4.9 individuals (average) of the census values. By demonstrating the veracity of this straightforward and inexpensive sampling method, we provide confidence in its operability, urging its use to fill conservation voids for Caprinae and other data-deficient species inhabiting rugged or heavily vegetated terrain.

We investigated survival and cause-specific mortality for a mountain goat ( Oreamnos americanus ) population during a period when the puma ( Puma concolor ) population was growing in the Black Hills, South Dakota, 2006–2018. We obtained survival data from 47 adult goats ( n = 33 females, n = 14 males). Annual survival varied from 0.538 (95% CI [0.285–0.773]) to 1.00 (95% CI [1.00–1.00]) and puma predation was the primary cause-specific mortality factor over a 12-year period. Cumulative hectares of mountain pine beetle ( Dendroctonus ponderosae ) disturbance was a covariate of importance ( w i = 0.972; β = 0.580, 95% CI [0.302–0.859]) influencing survival. To our knowledge, this is the first account of puma being the primary mortality factor of mountain goats over a long-term study. The Black Hills system is unique because we could examine the expanded realized niche of puma in the absence of other large carnivores and their influence on mountain goats. We hypothesize that puma were being sustained at higher densities due to alternate prey sources (e.g., white-tailed deer; Odocoileous virginianus ) and this small population of mountain goats was susceptible to predation by one or several specialized puma in the Black Hills. However, we also hypothesize a changing landscape with increased tree mortality due to insect infestation provided conditions for better predator detection by goats and increased survival. Alternatively, open canopy conditions may have increased understory forage production potentially increasing mountain goat survival but we did not evaluate this relationship. Survival and mortality rates of mountain goats should continue to be monitored as this small population may be highly susceptible to population declines due to slow growth rates.

Long-term datasets are becoming increasingly important for assessing population- and species-level responses to a changing environment. Programs that record morphological measurements of horns, antlers, and pronghorns were established in the early- to mid-20th century to collect biological information about animals that possess large horns, antlers, or pronghorns, which could be used to assess the effectiveness of conservation efforts for large mammals in North America. The general relevance of record books has been questioned because of the minimum size requirements for inclusion in a record book, which may mask trends when changes in the population occur. We compared trends in size of antlers, horns, and pronghorns through time using records from three records programs with different minimum size requirements to evaluate the influence of entry requirements on temporal trends. We also investigated whether horn, antler, or pronghorn size affected the probability of specimens being submitted to a records program. Only two of 17 categories exhibited less-pronounced trends in the record book with the highest size requirements for entry, and in two categories trends were more pronounced. Although societal interest in submitting eligible specimens increased slightly over time in one of six categories, the probability of voluntary entry was largely random and not affected by year of harvest or size of specimen. In contrast to previous criticisms, trends in record books should not be expected to represent the size of all males within a population. Instead, our evaluation indicates that the records programs we examined can provide a useful resource for assessing long-term changes in phenotypic characteristics of ungulates, but importantly, they represent the respective range of sizes within which each program collects data.

ABSTRACTJuvenile recruitment in desert bighorn sheep (Ovis canadensis mexicana) is highly variable, yet the mechanisms influencing neonate survival are not well understood. Because few studies have equipped desert bighorn sheep lambs with telemetry collars, definitive data on cause‐specific mortality, and lamb survival estimates are lacking. Our objectives were to estimate lamb survival rates and determine cause‐specific mortality for desert bighorn sheep lambs during a period of mountain lion (Puma concolor) and coyote (Canis latrans) removal in southwestern New Mexico, USA. We captured pregnant adult females each fall and fitted them with a telemetry collar and a vaginal implant transmitter to aid with neonate captures. We captured and radio‐collared 12 desert bighorn sheep lambs in 2012 and 14 in 2013 within 48 hours of parturition in the Peloncillo Mountains, New Mexico. We estimated lamb survival to 6 months of age. Across both years there were 14 mortalities, 12 of which were due to predation. Mountain lions killed 5 lambs (2 in 2012 and 3 in 2013), coyotes killed 4 lambs (all in 2013), a gray fox (Urocyon cinereoargenteus) killed 1 lamb in 2012, and 2 lambs were killed by unknown predators in 2013. Staged‐based survival estimates indicated the highest mortality rates occurred in the first week post birth; 5 of 14 lamb mortalities occurred before 7 days of age. Lamb survival to 6 months was substantially lower in 2013 (0.20 ± 0.11 [SE]) than in 2012 (0.71 ± 0.14) with the differences in survival attributed to increased coyote predation in 2013. We did not detect differences in body mass at birth between years or differences in body mass, chest girth, or neck circumference at birth between lambs that were killed by predators and those that survived. Coyotes, mountain lions, and the gray fox killed lambs <8 weeks of age, but only mountain lions killed lambs >8 weeks old. Predator removals focused around the parturition period of desert bighorn sheep may be more likely to influence lamb survival rates than removals outside of the lambing season. © 2018 The Wildlife Society.

ABSTRACTThe objective of this review is to generate a synthesis of research conducted on predation of bighorn sheep (Ovis canadensis) and to suggest directions for future research relative to current knowledge gaps and a novel hypothesis. This review is primarily based on literature from the last 60 years on desert bighorn sheep (O. c. nelsoni), Rocky Mountain bighorn sheep (O. c. canadensis), and mountain lion (Puma concolor) predation. Although, many predators kill bighorn sheep, only mountain lions are currently considered to be the primary proximate cause of mortality for many bighorn sheep populations. The ultimate cause of this phenomenon has vexed wildlife managers for >40 years. There are 3 primary reasons for increased predation on bighorn sheep by mountain lions. First, there is an increased presence of mountain lions in habitats where they were historically absent or rare because of the expansion of mule deer (Odocoileus hemionus) following the extensive conversion of fire‐maintained grasslands to shrublands in the late‐1800s. Second, is the extirpation of the 2 dominant apex carnivores (wolves [Canis lupus] and grizzly bears [Ursus arctos]) during this same time period and a hypothesized numerical response of mountain lions to those extirpations. Finally, the response of mountain lions to the cessation of >70 years of intensive predator control has often resulted in unsustainable mountain lion‐bighorn sheep ratios, especially for desert bighorn sheep. Additionally, the effect of mountain lion predation is exacerbated by declines in bighorn sheep that do not result in declines in mountain lions because of their ability to prey switch to mule deer, elk (Cervus canadensis), or domestic cattle; kleptoparasitism of mountain lions kills, by ursids and canids, resulting in higher kill rates for mountain lions; and a possible ecological trap where adaptations derived over evolutionary time are no longer adaptive because of human‐induced changes in the sympatric apex predator guild. Control of mountain lions, when mountain lion‐ungulate ratios are high, might be required to protect small or endangered bighorn sheep populations, and to produce bighorn sheep for restoration efforts. © 2017 The Wildlife Society.

Fitness of female ungulates is determined by neonate survival and lifetime reproductive success. Therefore, adult female ungulates should adopt behaviors and habitat selection patterns that enhance survival of neonates during parturition and lactation. Parturition site location may play an important role in neonatal mortality of desert bighorn sheep (Ovis canadensis mexicana) when lambs are especially vulnerable to predation, but parturition sites are rarely documented for this species. Our objectives were to assess environmental characteristics at desert bighorn parturition, lamb nursery, and predation sites and to assess differences in habitat characteristics between parturition sites and nursery group sites, and predation sites and nursery group sites. We used vaginal implant transmitters (VITs) to identify parturition sites and capture neonates. We then compared elevation, slope, terrain ruggedness, and visibility at parturition, nursery, and lamb predation sites with paired random sites and compared characteristics of parturition sites and lamb predation sites to those of nursery sites. When compared to random sites, odds of a site being a parturition site were highest at intermediate slopes and decreased with increasing female visibility. Odds of a site being a predation site increased with decreasing visibility. When compared to nursery group sites, odds of a site being a parturition site had a quadratic relationship with elevation and slope, with odds being highest at intermediate elevations and intermediate slopes. When we compared predation sites to nursery sites, odds of a site being a predation were highest at low elevation areas with high visibility and high elevation areas with low visibility likely because of differences in hunting strategies of coyote (Canis latrans) and puma (Puma concolor). Parturition sites were lower in elevation and slope than nursery sites. Understanding selection of parturition sites by adult females and how habitat characteristics at these sites differ from those at predation and nursery sites can provide insight into strategies employed by female desert bighorn sheep and other species during and after parturition to promote neonate survival. © 2016 The Wildlife Society.

ABSTRACTForaging behavior affects animal fitness and is largely dictated by the resources available to an animal. Understanding factors that affect forage resources is important for conservation and management of wildlife. Cattle sympatry is proposed to limit desert bighorn population performance, but few studies have quantified the effect of cattle foraging on bighorn forage resources or foraging behavior by desert bighorn. We estimated forage biomass for desert bighorn sheep in 2 mountain ranges: the cattle‐grazed Caballo Mountains and the ungrazed San Andres Mountains, New Mexico. We recorded foraging bout efficiency of adult females by recording feeding time/step while foraging, and activity budgets of 3 age‐sex classes (i.e., adult males, adult females, yearlings). We also estimated forage biomass at sites where bighorn were observed foraging. We expected lower forage biomass in the cattle‐grazed Caballo range than in the ungrazed San Andres range and lower biomass at cattle‐accessible versus inaccessible areas within the Caballo range. We predicted bighorn would be less efficient foragers in the Caballo range. Groundcover forage biomass was low in both ranges throughout the study (Jun 2012–Nov 2013). Browse biomass, however, was 4.7 times lower in the Caballo range versus the San Andres range. Bighorn in the Caballo range exhibited greater overall daily travel time, presumably to locate areas of higher forage abundance. By selecting areas with greater forage abundance, adult females in the Caballo range exhibited foraging bout efficiency similar to their San Andres counterparts but lower overall daily browsing time. We did not find a significant reduction in forage biomass at cattle‐accessible areas in the Caballo range. Only the most rugged areas in the Caballo range had abundant forage, potentially a result of intensive historical livestock use in less rugged areas. Forage conditions in the Caballo range apparently force bighorn to increase foraging effort by feeding only in areas where adequate forage remains. © 2015 The Wildlife Society.

ABSTRACT Bender and Weisenberger (2005) reported that desert bighorn sheep (Ovis canadensis) on San Andres National Wildlife Refuge (SANWR), New Mexico, USA, were primarily limited by rainfall. However, they failed to mention, or were unaware, that persistent long‐term predator control was used to enhance population growth at SANWR. Additionally, lamb:female ratios were collected throughout the year, rather than dates typically associated with assessing recruitment, and therefore influence of precipitation on lamb recruitment was unknown. Finally, model predictions forwarded by Bender and Weisenberger (2005), that carrying capacity of SANWR is zero when annual rainfall is <28.2 cm, were not supported by data, nor were their model results properly interpreted. The coefficient of determination value of 88.9% for the relationship between population size and current year's precipitation was primarily a function of serial correlation between successive years in population data, with current year's precipitation accounting for only 3.8% of this value. This suggests that precipitation was a weak predictor of population increase. These errors in concert make biological inferences reported in Bender and Weisenberger (2005) of limited value.

Conservation BiologyVolume 20, Issue 5 p. 1341-1341 Bighorn Sheep, Mountain Lions, and the Ethics of Conservation Eric M. Rominger, Corresponding Author Eric M. Rominger Wildlife Management Division, New Mexico Department of Game and Fish, P.O. Box 25112, Santa Fe, NM 87504, U.S.A.email [email protected] [email protected]Search for more papers by this authorVernon C. Bleich, Vernon C. Bleich Sierra Nevada Bighorn Sheep Recovery Program, California Department of Fish and Game, 407 West Line Street, Bishop, CA 93514, U.S.A.Search for more papers by this authorElise J. Goldstein, Elise J. Goldstein Wildlife Management Division, New Mexico Department of Game and Fish, P.O. Box 25112, Santa Fe, NM 87504, U.S.A.Search for more papers by this author Eric M. Rominger, Corresponding Author Eric M. Rominger Wildlife Management Division, New Mexico Department of Game and Fish, P.O. Box 25112, Santa Fe, NM 87504, U.S.A.email [email protected] [email protected]Search for more papers by this authorVernon C. Bleich, Vernon C. Bleich Sierra Nevada Bighorn Sheep Recovery Program, California Department of Fish and Game, 407 West Line Street, Bishop, CA 93514, U.S.A.Search for more papers by this authorElise J. Goldstein, Elise J. Goldstein Wildlife Management Division, New Mexico Department of Game and Fish, P.O. Box 25112, Santa Fe, NM 87504, U.S.A.Search for more papers by this author First published: 21 September 2006 https://doi.org/10.1111/j.1523-1739.2006.00535_2.xCitations: 4Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Literature Cited Bleich, V. C., and B. M. Pierce. 2005. Management of mountain lions in California. Pages 63– 69 in E. L. Buckner and J. Reneau, editors. Records of North American big game. 12th edition. Boone and Crockett Club, Missoula , Montana . Minteer, B. A., and J. P. Collins. 2005. Ecological ethics: building a new tool kit for ecologists and biodiversity managers. Conservation Biology 19: 1804– 1812. NMDGF (New Mexico Department of Game and Fish). 2003. Plan for the recovery of desert bighorn sheep in New Mexico 2003–2013. NMDGF, Santa Fe , New Mexico . Rominger, E. M., H. A. Whitlaw, D. L. Weybright, W. C. Dunn, and W. B. Ballard. 2004. The influence of mountain lion predation on bighorn sheep translocations. Journal of Wildlife Management 68: 993– 999. West, K. 2002. Lion versus lamb. Scientific American 286: 20– 21. Citing Literature Volume20, Issue5October 2006Pages 1341-1341 ReferencesRelatedInformation

Neuhaus & Ruckstuhl (2004), in a rather vitriolic critique, claim that the primary weakness of our study of desert bighorn sheep, Ovis canadensis mexicana (Mooring et al., 2003), is its lack of congruity with their hypothesized explanation for sexual segregation, the ‘activity budget hypothesis’. In a series of papers published over the past 5 years (Ruckstuhl, 1998, 1999; Ruckstuhl & Neuhaus, 2000, 2002; Neuhaus & Ruckstuhl, 2002; Ruckstuhl & Kokko, 2002), these authors have argued vigorously that the activity budget hypothesis is the only general explanation for sexual segregation, in which males and females of sexually dimorphic ungulates form separate groups for much of the year. Neuhaus and Ruckstuhl have repeatedly argued that all other proposed explanations for sexual segregation are secondary factors. They predicted that “the activity budget hypothesis would fail to explain sexual segregation if males and females showed the same activity patterns but lived segregated. . .” (Ruckstuhl & Neuhaus, 2002: p. 80). This is, in fact, one of the conclusions of our study (Mooring et al., 2003). However, we believe that the issues raised by Neuhaus & Ruckstuhl have implications beyond the specific context of our study. Although the activity budget hypothesis contributes to the multiple hypotheses proposed to explain the phenomenon of

We studied the effects of mountain lion (Puma concolor) predation on 2 translocated populations of bighorn sheep (Ovis canadensis) in New Mexico, USA. During 1993, 32 Rocky Mountain bighorn sheep (O. c. canadensis) were translocated to Wheeler Peak Wilderness Area in northern New Mexico, and during 1992-1993, 31 desert bighorn sheep (O. c. mexicana) were translocated to Sierra Ladron in central New Mexico. We monitored both populations from release through 2000 using fixed-wing aircraft and ground and/or helicopter surveys. We determined cause of mortality for radiomarked individuals (n = 26) and calculated survival rates, cause-specific mortality rates, exponential growth rates, and lamb:ewe ratios. The post-lambing population estimates in 2000 were 180 in Wheeler Peak and 21 in Sierra Ladron. Annual adult survival was higher (P < 0.005) in the Wheeler Peak population (0.955) than in the Sierra Ladron population (0.784). Annual lamb:ewe ratios also were higher (P < 0.001) in the Wheeler Peak population (66.7 vs. 29.8). Mean annual exponential growth rate (r) in the Wheeler Peak population was 0.25 compared to -0.01 for the Sierra Ladron population. Predation by mountain lions was the primary proximate cause (75%) of 16 known-cause mortalities of radiomarked bighorn sheep in the Sierra Ladron population, while we did not document any predation in Wheeler Peak. The annual cause-specific mortality rates due to mountain lion predation in Sierra Ladron were 0.13 for males, 0.09 for females, and 0.11 for all adult bighorn sheep. Mountain lion predation may have limited the Sierra Ladron bighorn sheep population and could be imposing a destabilizing inverse density-dependent mortality. Mountain lions preyed on domestic cattle in the Sierra Ladron area and throughout desert bighorn sheep habitat in New Mexico; we therefore hypothesize that cattle "subsidized" the diets of mountain lions (i.e., reduced or eliminated natural starvation). The ultimate cause of mortality for these desert bighorn sheep may be related to subsidized mountain lion populations that do not appear to decline following native ungulate population decreases. In addition, the encroachment of woody vegetation may increase the hunting success of ambush predators like mountain lions. High mountain lion predation may require mitigation for the successful restoration of bighorn sheep.

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.

Foraging options of woodland caribou (Rangifer tarandus caribou) in the high snowpack ecosystems of western North America become narrowed. after freezing; temperatures in autumn precipitate leaf-drop in deciduous shrubs. The objectives of this research were to determine the influence of (1) removing arboreal lichen (Ascomycetes) on windthrown trees and myrtle boxwood. (Pachistima myrsinites) and (2) stand type (old-growth versus clearcut) on woodland caribou foraging dynamics during autumn. Foraging trials were conducted with 3 tame woodland. caribou in 6 0.5-ha pens. In 3 treatment pens all windthrown arboreal lichen-bearing trees were removed from the old-growth portion of tie pen and extant myrtle boxwood plants were removed from the entire pen. In the 3 control pens all extant windthrown trees and myrtle boxwood plants were retained. In addition, pens were constructed such that half of each pen was in an old-growth stand of western red-cedar (Thuja plicata)-Western hemlock (Tsuga heterophylla) and half was in an adjacent clearcut. Arboreal lichen had the greatest influence on dry-matter intake rate (DMIR) because of the large bite size provided by this forage. In control pens, caribou had higher DMIR (P = 0.006) and crude protein intake rate (CPIR) (P = 0.007) than in treatment pens where lichen-bearing windthrown trees had been removed, Arboreal lichen from windthrown trees was 52% (range = 43-64) of the total DMI in the old-growth portions of control pens. Arboreal lichen from windthrown trees comprised 81% (range = 75-92) of the arboreal lichen bites (i.e., 19% of arboreal lichen bites were from litterfall and standing trees), and 28% (range = 16-48) of total bites in the timbered portion of control pens. The DMIR (P = 0.004) and CPIR (P = 0.004) of caribou was also greater in old-growth than in clearcut portions of pens. Search time was greater (P = 0.003) in clearcut portions of pens than in old-growth portions. Myrtle boxwood comprised <0.4% of caribou diets. These data suggest that arboreal lichen is an important dietary component earlier in autumn than previously reported.

Unlike other North American cervids, woodland caribou (Rangifer tarandus caribou) in the Selkirk ecosystem do not forage on browse.Therefore, during autumn as forbs become senescent and deciduous shrubs defoliare, caribou foraging decisions are narrowed.Shallow snow depths preclude a dier shift to arboreal lichen (Ascomycetes) in standing trees, as is observed in late winter.The objective of this research was to determine the importance of the two principal forage items previously reported in autumn diets: (1) arboreal lichen on windthrown trees and (2) the evergreen shrub myrtle boxwood (Pacbistima myrsimtes).Foraging trials were conducted with three tame woodland caribou in six 5000 m 2 pens experimentally manipulated to either remove all windthrown trees and myrtle boxwood or retain extant myrtle boxwood and add "windthrown" trees by felling trees.Additionally, the pen design was such that half was in an oldgrowth stand of western red cedar (Thuja plkata)!wesrern hemlock (Tsuga heterophylla) and half was in an adjacent clear-cut.Arboreal lichen, as a result of a large bite size, had the greatest influence on intake rate.Caribou in pens with lichen bearing windthrown trees had significantly higher intake rates (P<0.0()6)and significantly lower (P<0.01)eating bite rate (exclusive of search time between plants).Foraging bite rate (inclusive of search time between plants) did not differ (P<0.20)due to treatment.Intake rates (P<0.005)and foraging bite rates (P<0.03) of caribou were significantly greater in timbered portions of pens.Search rime was significantly greater (P<0.005) in clear-cut portions of pens.In the timbered portion of treatment pens, lichen comprised 34% of the total bites and 67% of the dry matter intake and arboreal lichen from windthrown trees comprised 27% of the total bites and 52% of the dry matter intake.These dara suggesr that arboreal lichen is an important dietary component earlier in autumn than previously reported and extends the period that woodland caribou subsist primarily or solely on arboreal lichen 30-60 days in high snowpack ecosystems of western North America.Tame caribou autumn diets were comprised of <1% myrtle boxwood, in apparent conflict with observations of wild caribou in timbered habitats with myrtle boxwood.However, in these trials >95% of the myrtle boxwood occurred in the clear-cur portion of trial pens, and forages in clear-cuts have been reported to have significantly higher levels of secondary plant compounds.Total phenolics in myrtle boxwood samples collected from the clear-cut portion of trial pens and from clear-cuts in British Columbia were 3-times greater than levels in myrtle boxwood samples collected from old-growth stands in British Columbia.In addition, snow depths underneath the forest canopy never covered the primary forage species.I hypothesize that these woodland caribou foraged very little on myrtle boxwood because of (1) the availability of other forage species, and (2) the high level of phenolics present in myrtle boxwood during these rrials.

To better understand late winter foraging ecology of woodland caribou (Rangifer tarandus caribou) feeding on arboreal lichens, we used bottle-raised caribou in experimental arena trials with artificial trees, and in field trials within historical late-winter habitat. Factors with the greatest influence on intake rate differed between experimental arena and field trials. Bite size was the most important variable in experimental arena trials; bite rate was the most important in field trials. During late winter field trials, caribou foraged on lichen primarily on standing subalpine fir (Abies lasiocarpa) and dead trees. Bite size, bite rate, intake rate, tree resident time, and amount of lichen eaten per tree were included in a general linear model with tree species, tree size class, and tree lichen class ( average) as the independent variables. Tree lichen class was the most important variable in the model and 76% of all bites occurred on >average lichen class trees. Compared to theoretical maximums, intake rate was low on all lichen class trees (range = 1.4-2.1 g/min). At these intake rates caribou would have to forage 14-21 hours to meet predicted daily requirements. Tree resident time and time between trees varied inversely with tree density. In cafeteria style preference trials with the 2 primary arboreal lichen genera, caribou strongly preferred Bryoria spp. (92%) compared to Alectoria sarmentosa (8%). Apparent dry matter digestibility of this diet was 82%. Timber stands must be substantially older than traditional harvest rotation lengths to provide the high lichen biomass found on >average lichen class trees. Caribou remained in habitats where Bryoria was the predominant genus of arboreal lichen and would not forage in A. sarmentosa dominated valley bottom habitat.

All caribou exhibited a strong preference (92%) for lichen in the multi-species Bryoria complex (range=87-99%).Preference for Bryoria may be a function of higher protein content, lower tensile strength, or differences in concentrations of secondary plant constituents.

The data suggest that arboreal lichen biomass and/or bite size are primary factors influencing intake rate. Caribou did not increase bite rate to compensate for smaller bite sizes or decreased biomass. Forest management should enhance lichen production to maximize intake rates for woodland caribou.

Research, primarily on the endangered Selkirk woodland caribou population has enabled biologists to answer many of the basic ecology questions pertaining to caribou in high snowpack ecosystems.