Printer Friendly

Seasonal foraging strategies of migrant and nonmigrant Pronghorn in Yellowstone National Park.

ABSTRACT--We characterized the seasonal composition and quality of migrant and non-migrant Pronghorn (Antilocapra Americana) diets in Yellowstone National Park during 2006-2007. During winter (January-April), when migrants and non-migrants occupied the same winter range, the overall percent relative density for each forage class in Pronghorn diets (n = 51 composite fecal samples) was 67 + 6% (standard error) shrubs, 17 + 3% forbs, 13 + 3% grasses, and 3 + 1% other. However, spring and summer diets differed for migrants and non-migrants. Diets of migrants (n = 34) to higher-elevation ranges with higher precipitation and forage quality during May-August were dominated by 68 + 2% forbs, whereas summer diets of non-migrants (n = 21) remaining on the winter range were co-dominated by 48 + 2% forbs and 42 + 1% shrubs. Diet quality for migrant Pronghorn, as indexed by fecal nitrogen and DAPA, was also generally higher than for nonmigrants during a period when the demands of late gestation and lactation were high. These results suggest that improved perinatal condition among fawns born to migrant females in Yellowstone National Park may be driven by higher-quality forage conditions in migrant areas, bolstering conclusions from previous studies that migration represents an adaptive strategy in this population given current conditions in the Park.

Key words: Antilocapra americana, diet composition, diet quality, foraging, migration, Pronghorn, Yellowstone National Park

**********

The rolling grasslands and shrub-steppe communities occupied by Pronghorn (Antilocapra americana) are often strongly influenced by plant phenology and abiotic conditions (Yoakum 2004a). Pronghorn selectively feed on a variety of forbs and shrubs, with grasses and grass-like plants (graminoids) typically comprising a minor portion of their diet (Yoakum 2004b). Seasonal conditions force many Pronghorn populations to remain in relatively low-elevation, windswept areas during winter where snow is less deep and food is more readily available (Yoakum 2004a).

The Yellowstone Pronghorn population was once numerous (1000 to 1500 animals) in the shrub-steppe and mixed-forest habitats of what is now Yellowstone National Park (Skinner 1922). During winter, individuals migrated 80 to 130 km down the Yellowstone River valley from higher-elevation summer ranges on and surrounding the northern Yellowstone Plateau to lower-elevation winter ranges in south-central Montana. However, Euro-American colonization and settlement reduced Pronghorn numbers and effectively eliminated their migration outside the park sometime before 1920. Portions of this migratory route have been reestablished over the past decade through efforts by the National Parks Conservation Association, working with landowners to remove and modify fences in critical bottlenecks (Skinner 1922; White and others 2007; Barnowe-Meyer and others 2013). Nonetheless, the Yellowstone Pronghorn population is now almost entirely restricted to a relatively small winter range along Yellowstone National Park's northern boundary adjacent to Gardiner, Montana.

During summer, the Yellowstone Pronghorn population is partially migratory, with >70% of the individuals migrating 15-50 km to spend May-October at higher elevations (White and others 2007). The spring migration typically occurs in April when snow begins to melt and new vegetation starts to grow at higher elevations, allowing migrants to track plant phenology across a range of elevations (Barnowe-Meyer and others 2011). Despite this seasonal access, a small proportion of Yellowstone Pronghorn (<30%) remain year-round on the winter range near Gardiner, Montana. Eighty percent (n = 44) of radio-collared females monitored during 1999-2005 showed fidelity across years to their migration strategy and summer-use area (White and others 2007).

The adequacy of available forage to meet metabolic demands, in terms of quality and quantity, is reflected in the rates of ingestion and digestion of energy and nutrients (nutrition) and the resulting state of body condition (such as fat and protein; Harder and Kirkpatrick 1994; Parker and others 1999). In turn, body condition strongly influences the probability of breeding, overwinter survival, fawn survival and recruitment, and vulnerability to predation (Cook 2002). Higher-elevation ranges receive more precipitation and likely support higher-quality forage during the growing season (Despain 1990; Fames and others 1999). As a result, migratory Pronghorn could have access to more-nutritious new vegetation growth at a critical time of year when the demands of lactation are high, thereby enhancing milk production and quality and, in turn, reproductive success. Previous research has found that migrant Yellowstone Pronghorn have higher reproductive success than non-migrants, despite occupying areas with abundant and diverse predator communities (Barnowe-Meyer and others 2009, 2010).

We characterized the composition and quality of Yellowstone Pronghorn diets during summer and winter, and evaluated the foraging strategies of migrant and non-migrant Pronghorn across seasons. We predicted spring and summer diets would be of higher quality in the higher-elevation mountain areas accessed by migrants than the lower-elevation valley winter range used by non-migrants during this period.

METHODS

Study Area

Yellowstone Pronghorn occupy foothills, mountain slopes, and valley bottoms along the Gardiner, Lamar, and Yellowstone Rivers in the northern portion of Yellowstone National Park, Wyoming, and adjacent areas of Montana (Fig. 1; White and others 2007; Boccadori and others 2008). Summers are generally short and cool, and winters are long and cold, resulting in a mean annual temperature of 1.8[degrees]C. Mean annual precipitation varies from about 25 cm in the Gardiner basin (approximately 1615 m elevation), where migrant and non-migrant Pronghorn share a winter range, to about 35 cm in the mountain summer ranges (approximately 2135 m elevation) used by migrants. Average snow-water equivalents (amount of water in snow) range from about 2 to 30 cm along this elevation gradient (Fames and others 1999). However, drought conditions persisted in northwestern Wyoming during 1999-2007 (National Oceanic and Atmospheric Administration 2015).

The vegetation and plant composition of the winter range for Yellowstone Pronghorn consists primarily of open grassland-sagebrush steppe with interspersed upland grasslands, wet meadows, old agricultural fields and pastures, alfalfa fields and livestock pastures on private land outside of the Park, and non-vegetated areas (Boccadori and others 2008). The vegetation and plant composition of summering areas used by migrants in the park consists of mixed grassland, shrub-steppe, and forest types, with minor patches of riparian habitat (Despain 1990; Barnowe-Meyer and others 2011).

Diet Composition

We estimated the botanical composition of Pronghorn diets using microscopic examination of plant fragments in fresh fecal material (Sparks and Malachek 1968) collected during January-August 2006 and January-April 2007. We observed groups of individuals, noted defecation events, then collected fecal samples once the group had left the area. We collected samples generally within 30 min of defecation from both male and female individuals, though males were likely under-sampled relative to females. We then composited samples of 7 to 10 pellets each from 3 to 4 adult Pronghorn by month and area. We sampled the winter range and main summering areas for Yellowstone Pronghorn. The latter included: (1) the Gardiner basin and northwestern portion of Mount Everts; (2) Blacktail Deer Plateau, including Blacktail ponds and Oxbow/Geode creeks; (3) Specimen Ridge, including Crystal Bench and Little America; and (4) Lamar Valley, including the Soda Butte area (Fig. 1; White and others 2007). Staff at the Wildlife Habitat and Nutrition Laboratory, Washington State University, Pullman, Washington, oven-dried (70[degrees]C) and ground (1-mm size) each composite before preparing 4 slides from each composite and examining 25 views per slide for a total of 100 views per composite sample. They identified each forage class (such as shrubs, forbs, grasses, sedge-rushes, and conifers) and all plants >5% of the diet to at least the genus level using epidermal-cell-tissue fragments. We calculated monthly means per area as percent relative density based on the average of all composites collected per month. Highly digestible species may be underestimated because we did not adjust results for differential digestibility (Sparks and Malachek 1968; Striby and others 1987).

Forage Quality

During January-April 2007, we collected and froze (-17[degrees]C) 2 to 3 replicate samples per month of edible portions of major forage plants used by Yellowstone Pronghorn on their winter range (Boccadori 2002). Sampled plants included the following forage types and genera: shrubs (Artemisia, Chrysothamnus, Eriogonum, Krascheninnikovia, Salix, Sarcobatus); forbs (Alyssum, Atriplex, Phlox); grasses (Agropyron, Bromus, Oryzopsis, Poa); sedges-rushes (Carex); conifers (Juniperus); and lichens. Replicate samples (1 g oven-dried at 70[degrees]C) were sent to the Wildlife Habitat and Nutrition Laboratory for freeze drying, grinding, and estimation of percent crude protein (% nitrogen times 6.25), percent in vitro dry-matter digestibility, and gross energy (cals [g.sup.-1]).

To estimate the quality of winter diets, we calculated the sum of products of forage-quality values (percent crude protein, %CP; percent in vitro dry-matter digestibility, %IVDMD; and gross energy, GE) of individual forage types and their relative composition in diets. This approach incorporates biases from fecal diet composition estimates and likely underestimates variance due to analyzing the product of diet composition and forage quality (Hobbs and others 1979; Parker and others 2005). In addition, staff from the Wildlife Habitat and Nutrition Laboratory measured fecal nitrogen (%FN) and 2, 6 diaminopimelic acid (DAPA; mg [g.sup.-1]) from composite samples of pellets collected during January-August 2006 and January-April 2007. Fecal nitrogen reflects dietary nitrogen and should lead to an increase in fecal DAPA, which is an amino acid residue in the cell walls of rumen bacteria. As digestible energy in the rumen increases, bacteria loads increase, causing more DAPA to be excreted in feces (Mould and Robbins 1981; Davitt and Nelson 1984).

RESULTS

Winter Diets

The overall percent relative density for each forage class in Pronghorn diets during January-April in 2006 and 2007 based on microscopic examination of 51 composite fecal samples was 67 + 6% (SE) shrubs, 17 + 3% forbs, 13 + 3% grasses, and 3 +1 % other (sedge, lichen, juniper; Table 1). Pronghorn diets during January through March were dominated by sagebrush (Artemisia; = 64 + 3%), with Big Sagebrush (Artemisia tridentata) making up an average of 58 + 3% of diets. Coinciding with new vegetation growth in spring, however, the proportion of shrubs in April diets decreased to 34%, with sagebrush making up 31% of April diets. Forbs increased to 36% of April diets, with grasses accounting for another 30%. Mean percent crude protein was similar during January and February for shrubs (= 10.0 + 0.5%) and forbs (= 10.2 + 0.3%), but increased substantially by April to 16.7% for shrubs and 15.1% for forbs (Table 2). Mean percent in vitro dry-matter digestibility increased from January to April for shrubs (38.0 to 53.2), forbs (44.0 to 65.6), and grasses (42.5 to 56.4; Table 2). Mean gross energy (cals [g.sup.-1]) was similar from January to April for shrubs (= 4902 +18.9 cals [g.sup.-1]), forbs (= 4554 + 32.5 cals [g.sup.-1]), and grasses (= 4576 + 47.5 cals [g.sup.-1]; Table 2).

Winter diets contained mean proportions of 11.7 + 0.7% crude protein and 49.8 + 1.3% digestible dry matter from January through March. Both crude protein and dry-matter digestibility varied significantly by month, with April values significantly greater than in January, February, and March (pairwise comparisons following one-way ANOVA, P [less than or equal to] 0.018 and < 0.001, respectively). Coinciding with new vegetation growth in spring, these proportions increased in April to 16.8% crude protein and 65.6% digestible dry matter. Gross energy in Pronghorn diets stayed relatively constant from January through March (5086-5030 cals [g.sup.-1]), but then decreased substantially to 4674 cals [g.sup.-1] during April.

Composite fecal samples contained mean proportions of 1.74 + 0.02% nitrogen and 0.51 + 0.01 mg/g DAPA during January-March 2006 and 2007 (Table 3; Fig. 2). Fecal nitrogen did not vary by month during the winters of 2006 or 2007 (one-way MANOVA, P [greater than or equal to] 0.146). DAPA did not vary by month during the winter of 2006 (one-way MANOVA, P = 0.332), but did vary during the winter of 2007 (one-way MANOVA, P = 0.005), rising from 0.46 mg [g.sup.-1] during January to 0.53-0.55 mg [g.sup.-1] during February-March. Coinciding with new vegetation growth in the spring of 2007, overall values increased during April to 2.18 + 0.16% fecal nitrogen and 0.59 + 0.07 mg [g.sup.-1] DAPA (Fig. 2).

Summer Diets

Based on microscopic examination of 55 composite fecal samples, the overall percent relative density for each forage class in Pronghorn diets during May-August in 2006 was 58 + 5% forbs, 31 +5% shrubs, 8 + 0.8% grasses, and 3 + 0.4% other (sedge, lichen; Table 4). Diets of non-migratory Pronghorn that remained on the Gardiner basin winter range through the summer were composed primarily of 42 + 1 % shrubs and 48 + 2% forbs, with 8 + 1% grasses, and 2 + 0.2% other (Table 4). In contrast, diets of migratory Pronghorn were dominated by 68 + 2% forbs, with 20 + 3% shrubs, 8 + 1% grasses, and 4 + 0.5% other. There was wide variation in diet composition for migrant Pronghorn using different summering areas (Table 4).

Composite fecal samples contained mean proportions of 2.8 + 0.07% nitrogen and 54 + 0.02 mg [g.sup.-1] DAPA during May-June through August, with these indices of diet quality peaking in May-June (Table 3; Fig. 2). Fecal nitrogen varied by month for non-migrants and migrants in 2006 (one-way MANOVA, P [less than or equal to] 0.005), peaking in May and June, respectively, in both groups (though May was not sampled for migrants, and June was not sampled for non-migrants; Table 5). Values of DAPA followed a similar pattern (one-way MANOVA, P [less than or equal to] 0.006). Composite fecal samples from non-migratory Pronghorn from May-June through August contained mean proportions of 2.48 + 0.06% fecal nitrogen and 0.56 + 0.02 mg [g.sup.-1] DAPA. Diets of migratory Pronghorn over this period contained mean proportions of 2.98 + 0.10% fecal nitrogen and 0.53 + 0.02 mg g 1 DAPA. Migrants had statistically higher values of percent fecal nitrogen (one-way ANOVA, P < 0.001), but not DAPA (one-way ANOVA, P = 0.117), than non-migrants in May-June; higher values of fecal nitrogen in July (one-way ANOVA, P < 0.001); and similar values of fecal nitrogen and DAPA in August (FN: one-way ANOVA, P = 0.319; DAPA: one-way ANOVA, P = 0.373; Table 3; Fig. 2). Interestingly, non-migrants had statistically higher values of DAPA than migrants in July (one-way ANOVA, P = 0.009).

DISCUSSION

The composition and quality of Yellowstone Pronghorn diets varied seasonally in patterns similar to other locales, with a predominant focus on shrubs in winter, forbs in summer, and a mixture of forbs and shrubs in spring and autumn (see Yoakum 2004b). In autumn and winter, Pronghorn in shrub-steppe habitats often browse on shrubs because they are higher in protein and more available than most forbs or grasses (Yoakum 2004b). Winter is the leanest period of the year, and both migrants and non-migrants in Yellowstone National Park have similar food supplies because they share a winter range (Boccadori and others 2008). Not surprisingly, the winter diets of these Pronghorn were dominated by shrubs. Though the digestibility of shrubs is relatively low, they have high crude-protein content and are readily available (not covered by snow). Conversely, the availability of forbs, which are fairly high in crude protein and digestibility, is lower in winter due to plant phenology and snow cover. Likewise, grasses are a poor choice during winter because the relatively small rumens in Pronghorn are not well-adapted to handle bulky fibrous grasses. Selective browsing by Yellowstone Pronghorn in winter likely contributed to their over-winter survival because the crude protein content of diets was well above the minimum level (5 to 7%) required for maintenance (Yoakum 2004b). Also, fecal nitrogen and DAPA were similar or higher to levels reported for other Pronghorn populations (Yoakum 2004b).

Tracking the protein content and digestibility of new plant growth in spring and summer is a common strategy of wild ruminants (Fryxell and others 1988). As a small ruminant, Pronghorn can benefit from being more selective during the growing season because emerging forbs and grasses are highly nutritious, digestible, and abundant. As expected, Yellowstone Pronghorn transitioned from a shrub-focused diet in winter to a diet focused on young grasses and forbs in spring and summer.

Barnowe-Meyer and others (2011) investigated a range of body condition and reproductive metrics for this population from 1999-2001, and noted higher indexed condition at birth and age at death for fawns born to migrant females. This study was partly intended to investigate possible drivers of these patterns. We were not able to differentiate the diets of migratory and non-migratory individuals during winter. Nutritionally, however, late May and June coincide with high reproductive demands during late gestation and lactation. Diets during this period can have a strong influence on the condition and survival of newborn young (Pettorelli and others 2005, 2007). By migrating to higher-elevation areas, migrant females have access to potentially more and higher-quality forage for approximately 6 wk prior to parturition in June (Barnowe-Meyer and others 2011).

In the spring and summer months of 2006, migrants grazed primarily on forbs, whereas non-migrants selected more evenly among forbs and shrubs. Diet quality for migrant Pronghorn, as indexed by fecal nitrogen, appears to have been substantially higher than for non-migrants during May-June and July, though we urge caution in the interpretation of these results because of sampling limitations during May and June. These results are particularly noteworthy because higher fawn survival rates in migrant areas (Barnowe-Meyer and others 2011) likely correspond to a higher relative abundance of lactating females in these areas, with correspondingly lower fecal nitrogen levels (Monteith and others 2014). DAPA levels for migrants in July were lower than for non-migrants, an unexpected result requiring additional investigation. Nonetheless, DAPA levels for migrants exceeded those for non-migrants in August (though not significantly). Collectively, our results suggest an overall pattern of higher diet quality for migrant Pronghorn relative to non-migrants.

In conjunction with previous research on this population, our results provide further evidence of an adaptive advantage of migration for this population, given current conditions in Yellowstone National Park. Migratory individuals gain access to and make use of high-quality foraging areas within the park, which likely leads to improved perinatal condition among fawns born to females in these areas (Barnowe-Meyer and others 2011). This enhanced condition of migrant fawns appears to contribute, in turn, to improved rates of summer survival and recruitment among migrants and, over time, an increasing proportion of migrants in the Yellowstone Pronghorn population (White and others 2007; Barnowe-Meyer and others 2010). The extent to which migration represents an adaptive strategy in this population is therefore sensitive to changes in the relative quality of spring and summer forage between migrant and non-migrant areas as well as other biotic and abiotic determinants of reproductive success in Yellowstone Pronghorn.

ACKNOWLEDGMENTS

This project received financial support from the Bernice Barbour Foundation, Montana State University, National Park Service, University of Idaho, and Yellowstone Park Foundation. We thank the Rocky Mountains Cooperative Ecosystem Studies Unit, College of Forestry and Conservation, University of Montana, for facilitating agreements.

Submitted 22 February 2016, accepted 30 September 2016. Corresponding Editor: Denim Jochimsen.

LITERATURE CITED

Barnowe-Meyer KK, White PJ, Davis TL, Byers JA. 2009. Predator specific mortality of Pronghorn on Yellowstone's northern range. Western North American Naturalist 69:186-194.

Barnowe-Meyer KK, White PJ, Davis TL, Smith DW, Crabtree RL, Byers JA. 2010. Influences of Wolves and high-elevation dispersion on reproductive success of Pronghorn (Antilocapra americana). Journal of Mammalogy 91:712-721.

Barnowe-Meyer KK, White PJ, Byers JA. 2011. Maternal investment by Yellowstone Pronghorn following winter habitat deterioration. Western North American Naturalist 71:222-233.

Barnowe-Meyer KK, White PJ, Waits LP, Byers JA. 2013. Social and genetic structure associated with migration in Pronghorn. Biological Conservation 168:108-115.

Boccadori SJ. 2002. Effects of winter range on a Pronghorn population in Yellowstone National Park, Wyoming [thesis]. Bozeman, MT: Montana State University.

Boccadori SJ, White PJ, Garrott RA, Borkowski JJ, Davis T. 2008. Yellowstone Pronghorn alter resource selection after sagebrush decline. Journal of Mammalogy 89:1031-1040.

Cook JG. 2002. Nutrition and food. In: Toweill DE, Thomas JW, editors. North American Elk: Ecology and management. Washington, DC: Smithsonian Institution Press, p 259-349.

Davitt BB, Nelson JR. 1984. Methodology for the determination of DAPA in feces of large ruminants. In: Nelson RW, editor. Proceedings of the western states and provinces Elk workshop. Edmonton, Alberta, p 133-147.

Despain DG. 1990. Yellowstone vegetation: Consequences of environment and history in a natural setting. Boulder, CO: Roberts Rinehart Publishers. 239 p.

Farnes P, Heydon C, Hansen K. 1999. Snowpack distribution across Yellowstone National Park. Final report Cooperative Agreement CA 1268-1-9014. Available from Department of Earth Sciences, Montana State University, Bozeman, MT 59717.

Fryxell JM, Greever J, Sinclair ARE. 1988. Why are migratory ungulates so abundant? American Naturalist 131:781-798.

Harder JD, Kirkpatrick RL. 1994. Physiological methods in wildlife research. In: Bookhout TA, editor. Research and management techniques for wildlife and habitats. Bethesda, MD: The Wildlife Society, p. 275-306.

Hobbs NT, Baker DL, Ellis JE, Swift DM. 1979. Composition and quality of Elk diets during winter and summer: A preliminary analysis. In: Boyce MS, Hayden-Wing LD, editors. North American Elk: Ecology, behavior, and management. Laramie, WY: University of Wyoming, p 47-53.

Monteith KB, Monteith KL, Bowyer RT, Leslie DM Jr, Jenks JA. 2014. Reproductive effects on fecal nitrogen as an index of diet quality: An experimental assessment. Journal of Mammalogy 95:301-310.

Mould ED, Robbins CT. 1981. Nitrogen metabolism in Elk. Journal of Wildlife Management 45:323-334.

National Oceanic and Atmospheric Administration. 2015. Historical Palmer Drought Indices, http:// www.ncdc.noaa.gov/temp-and-precip/drought/ historical-palmers. Accessed 6 November 2015.

Parker KL, Gillincham MP, Hanley TA, Robbins CT. 1999. Energy and protein balance of free-ranging Black-tailed Deer in a natural forest environment. Wildlife Monographs 143:1-48.

Parker KL, Barboza PS, Stephenson TR. 2005. Protein conservation in female Caribou (Rangifer tarandus): Effects of decreasing diet quality during winter. Journal of Mammalogy 86:610-622.

Pettorelli N, Weladji RB, Holand O, Mysterud A, Breie H, Stenseth NC. 2005. The relative role of winter and spring conditions: Linking climate and landscape-scale plant phenology to alpine Reindeer body mass. Biology Letters 1:24-26.

Pettorelli N, Pelletier F, Von Hardenberg A, Festa-Bianchet M, COte SD. 2007. Early onset of vegetation growth vs. rapid green-up: Impacts on juvenile mountain ungulates. Ecology 88:381-390.

Skinner MP. 1922. The prong-horn. Journal of Mammalogy 3:82-105.

Sparks DR, Malachek JC. 1968. Estimation percentage dry weight in diets using a microscope technique. Journal of Range Management 21:264-265.

Striby KD, Wambolt CL, Kelsey RG, Havstad KM. 1987. Crude terpenoid influence on in-vitro digestibility of sagebrush. Journal of Range Management 40:244-248.

White PJ, Davis TL, Barnowe-Meyer KK, Crabtree RL, Garrott RA. 2007. Partial migration and philopatry of Yellowstone Pronghorn. Biological Conservation 135:518-526.

Yoakum JD. 2004a. Habitat characteristics and requirements. In: O'Gara BW, Yoakum JD, editors. Pronghorn ecology and management. Boulder, CO: Wildlife Management Institute, University Press of Colorado, p 409-445.

Yoakum JD. 2004b. Foraging ecology, diet studies and nutrient values. In: O'Gara BW, Yoakum JD, editors. Pronghorn ecology and management. Boulder, CO: Wildlife Management Institute, University Press of Colorado, p 447-502.

Kerey K Barnowe-Meyer

Nez Perce Tribe, Wildlife Division, Lapwai, ID 83540 USA; kereybm@nezperce.org

PJ White, Troy L Davis, John J Treanor

National Park Service, Yellou'stone National Park, Mammoth, WY 82190 USA

John A Byers

Department of Biological Sciences, University of Idaho, Moscow, ID 83844 USA

Caption: FIGURE 1. The annual range of Pronghorn in and adjacent to Yellowstone National Park, Montana and Wyo

Caption: FIGURE 2. Variation in fecal nitrogen (%) and 2,6 diaminopimelic acid (DAPA; mg [g.sup.-1]) by month and migratory strategy from composite samples of pellets collected from migratory and non- migratory Yellowstone Pronghorn in 2006 and 2007.
TABLE 1. Percent relative density of each forage class in
Yellowstone Pronghorn diets during January-April in 2006
and 2007, based on microscopic examination of 51 composite
fecal samples.

Plant/Forage              Jan    Feb    Mar    Jan    Feb    Mar
                          2006   2006   2006   2007   2007   2007

Total Shrubs              74.4   73.5   66.4   75.1   75.4   68.9
  Artemisia tridentata    44.4   65.6   60.2   61.6   58.3   56.2
  Artemisia frigida        9.7    3.1    1.7    5.4   10.1    5.2
  Chrysothamnus            8.8    2.0    2.2    5.2    4.6    7.4
  Krascheninnikovia       10.1    0.3    0.0    0.9    1.6    0.0
  Salix                    0.0    0.3    0.0    0.0    0.0    0.0
  Minor shrubs             1.3    2.2    2.3    1.9    0.9    0.2
Total Forbs               12.7   16.3   14.1   16.4   12.0   11.4
  Alyssum                  1.7    7.4    5.9    0.3    0.0    6.9
  Atriplex                 5.9    4.5    4.9   11.9    5.8    0.0
  Descurainia              0.0    0.0    0.0    0.0    0.0    0.0
  Phlox/Leptodactylon      2.8    1.6    0.7    1.7    1.2    0.0
  Minor forbs              2.3    2.0    1.9    1.9    3.9    3.5
  Unknown forb             0.0    0.7    0.9    0.5    1.1    1.0
Total Grasses              0.5    7.2   15.7    2.2    8.1   17.9
  Agropyron                1.9    0.6    3.3    0.0    2.1    7.5
  Bromus                   1.9    1.0    3.2    0.0    0.5    3.8
  Koeleria                 0.0    0.0    0.0    0.0    0.0    0.0
  Oryzopsis                0.0    0.0    0.5    0.0    0.0    0.0
  Poa                      4.7    1.8    5.5    0.0    1.8    4.6
  Minor grasses            1.9    3.7    3.2    2.2    3.7    2.2
Total Sedge/Rush           0.2    0.2    0.0    0.1    0.1    0.4
Total Conifers             2.3    1.7    2.9    5.8    3.7    1.0
  Juniperus                1.3    1.1    1.1    4.8    2.6    0.0
  Pseudotsuga              0.0    0.0    1.3    0.0    0.0    0.0
  Minor conifers           1.0    0.6    0.5    0.9    1.0    1.0
Total Lichen/Moss/Thorn    0.0    1.2    0.9    0.6    0.8    0.6

Plant/Forage              Apr
                          2007

Total Shrubs              34.1
  Artemisia tridentata    21.0
  Artemisia frigida        9.7
  Chrysothamnus            1.7
  Krascheninnikovia        0.0
  Salix                    0.0
  Minor shrubs             1.6
Total Forbs               35.5
  Alyssum                 21.8
  Atriplex                 0.0
  Descurainia              6.5
  Phlox/Leptodactylon      0.0
  Minor forbs              5.5
  Unknown forb             1.7
Total Grasses             29.3
  Agropyron               10.7
  Bromus                   3.8
  Koeleria                 1.1
  Oryzopsis                0.0
  Poa                      9.8
  Minor grasses            3.9
Total Sedge/Rush           0.3
Total Conifers             0.0
  Juniperus                0.0
  Pseudotsuga              0.0
  Minor conifers           0.0
Total Lichen/Moss/Thorn    0.8

TABLE 2. Crude protein, in vitro dry matter digestibility, and gross
energy of potential forage plants on the winter range for
Yellowstone Pronghorn during January-April 2007.

Plant/Forage                     Crude protein (%)

                               Jan    Feb    Mar    Apr

Average Shrubs                  9.5   10.5   12.2   16.7
  Artemisia tridentata         11.1   12.2   14.1   20.4
  Artemisia frigida            10.6    9.1   13.4   15.8
  Chrysothamnus                 8.7    9.8    8.8    9.2
  Krascheninnikovia            11.1   17.3   21.5   29.4
  Sarcobatus *                 13.7   14.5   14.6   25.7
  Salix *                       6.5    7.2    7.3    8.1
  Eriogonum *                   5.1    3.4    5.9    8.4
Average Forbs                  10.5    9.9   14.5   15.1
  Alyssum                       7.7   11.8   19.8   16.2
  Atriplex                     13.1    9.5   12.8   19.0
  Phlox/Leptodactylon          10.8    8.4   10.8   10.1
Average Grasses                 9.9    8.9    8.7   16.2
  Agropyron                     4.2    6.1    6.5   13.7
  Bromus                       17.3   19.5   18.5   18.9
  Oryzopsis                            4.3    3.8   13.2
  Poa                           8.1    5.7    5.8   19.0
Average Sedge/Rushes           11.6                 16.6
Average Conifer (Juniperus)     8.6    9.1    8.9    9.4
Average Lichen/Moss/Thorn       7.0    9.1    7.5    6.7

Plant/Forage                   Dry-matter digestibility (%)

                               Jan    Feb    Mar    Apr

Average Shrubs                 38.0   42.0   45.1   53.2
  Artemisia tridentata         49.9   57.1   62.5   77.5
  Artemisia frigida            39.1   37.8   45.1   48.7
  Chrysothamnus                44.5   49.5   51.3   51.1
  Krascheninnikovia            35.4   39.8   51.5   63.9
  Sarcobatus *                 42.4   42.2   41.6   61.6
  Salix *                      28.9   40.6   38.0   37.6
  Eriogonum *                  25.6   27.3   25.9   32.4
Average Forbs                  44.0   44.7   54.7   65.6
  Alyssum                      51.3   49.6   52.8   72.2
  Atriplex                     45.0   44.9   59.1   68.5
  Phlox/Leptodactylon          35.6   39.5   52.0   56.2
Average Grasses                42.5   38.4   43.8   56.4
  Agropyron                    37.8   43.1   48.6   60.2
  Bromus                       48.8   38.1   50.4   52.7
  Oryzopsis                    31.6   28.1   39.0   48.9
  Poa                          51.9   44.1   37.3   64.1
Average Sedge/Rushes           42.6   45.7   52.0   78.9
Average Conifer (Juniperus)    46.8   49.8   43.9   49.2
Average Lichen/Moss/Thorn      33.4   34.3   40.9   36.4

Plant/Forage                   Gross energy (cals [g.sup.-1])

                               Jan    Feb    Mar    Apr

Average Shrubs                 4913   4921   4927   4846
  Artemisia tridentata         5137   5185   5221   5123
  Artemisia frigida            4920   4908   4727   4635
  Chrysothamnus                5464   5454   5485   5429
  Krascheninnikovia            4796   4943   4758   4596
  Sarcobatus *                 4857   4810   4855   4693
  Salix *                      4917   5035   5016   4915
  Eriogonum *                  4298   4112   4430   4528
Average Forbs                  4651   4513   4524   4527
  Alyssum
  Atriplex                     4719   4592   4375   4457
  Phlox/Leptodactylon          4584   4434   4673   4597
Average Grasses                4648   4576   4639   4442
  Agropyron                    4648   4554   4639   4468
  Bromus
  Oryzopsis                                         4264
  Poa                                 4597          4595
Average Sedge/Rushes
Average Conifer (Juniperus)    5830   5747   5875   5725
Average Lichen/Moss/Thorn      4211   4301   4297   4262

* Only trace amounts were detected (Table 1).

TABLE 3. Fecal nitrogen (%) and 2,6 diaminopimelic acid
(DAPA; mg [g.sup.-1]) from composite samples of pellets
collected from Yellowstone Pronghorn during January-August
2006 and January-April 2007.

                                       2006

Nutrition Index   Jan    Feb    Mar    Jun    Jul    Aug

Fecal Nitrogen
Mean              1.71   1.80   1.77   3.56   2.62   2.69
SE                0.07   0.05   0.06   0.25   0.06   0.09
DAPA
Mean              0.55   0.51   0.55   0.73   0.52   0.46
SE                0.04   0.02   0.03   0.05   0.01   0.02
n                 5      13     6      5      35     11

                         2007

Nutrition Index   Jan    Feb    Mar    Apr

Fecal Nitrogen
Mean              1.65   1.73   1.87   2.18
SE                0.05   0.03   0.11   0.16
DAPA
Mean              0.46   0.55   0.53   0.59
SE                0.01   0.02   0.00   0.07
n                 13     6      2      6

TABLE 4. Percent relative density of each forage class in
migrant and non-migrant Yellowstone Pronghorn diets in
each of the main summering areas during May-August 2006.
Results are based on microscopic examination of 55 composite
fecal samples. Main summering areas (Gardiner Basin [also
the winter range], Blacktail Deer Plateau, Specimen Ridge,
and Lamar Valley) are described in detail in the text and
appear in Figure 1.

Plant/Forage               Non-migrant diets

                           May    July   Aug

Total Shrubs               39.9   43.1   43.1
  Artemisia tridentata     17.7    3.9    2.7
  Artemisia frigida        20.7   35.0   31.5
  Chrysothamnus             0.0    1.2    5.5
  Other shrubs each <5%     1.5    3.0    3.4
Total Forbs                52.8   48.4   44.3
  Achillea                  1.5    0.5    1.1
  Alyssum                   6.5    1.1    0.0
  Erodium/Geranium          0.0    1.9    0.0
  Erysimum/Litkospermum     4.5    2.8    2.4
  Heliauthus/Rudbeckia/     0.0    1.5    2.5
  Solidago
  Lomatium                  6.4    6.4    4.9
  Lupinus                   1.5    1.0    12.5
  Other forbs each <5%     32.4   33.2   20.9
Total Graminoids            7.0    7.2    11.4
Total Other                 0.3    1.3    1.2

Plant/Forage               Migrant diets

                           Jun    July   Aug

Total Shrubs               14.8   23.6   22.9
  Artemisia tridentata     10.7    4.1   10.7
  Artemisia frigida         2.3   13.0    4.7
  Chrysothamnus             0.9    1.8    3.9
  Other shrubs each <5%     0.9    4.7    3.6
Total Forbs                71.4   67.5   65.8
  Achillea                  9.7    0.3    3.4
  Alyssum                   0.0    0.0    0.0
  Erodium/Geranium          6.2   15.7    5.5
  Erysimum/Litkospermum     1.5    3.8    0.0
  Heliauthus/Rudbeckia/     1.2    2.6    8.4
  Solidago
  Lomatium                  2.7    3.2    4.8
  Lupinus                   5.9    4.9    3.9
  Other forbs each <5%     44.2   37.0   39.8
Total Graminoids           13.7    7.7   10.6
Total Other                 0.1    1.2    0.7

Plant/Forage               Diets in main summering areas

                           Gardiner   Blacktail   Specimen   Lamar

Total Shrubs               43.1       17.0        28.4       9.8
  Artemisia tridentata      3.9        3.1         4.6       3.2
  Artemisia frigida        35.0        9.4        16.2       3.0
  Chrysothamnus             1.2        2.6         1.5       1.5
  Other shrubs each <5%     3.0        1.9         6.1       2.1
Total Forbs                48.4       74.2        63.0      77.4
  Achillea                  0.5        0.5         0.3       0.0
  Alyssum                   1.1        0.0         0.0       0.0
  Erodium/Geranium          1.9       18.3        12.7      26.8
  Erysimum/Litkospermum     2.8        1.3         5.5       0.0
  Heliauthus/Rudbeckia/     1.5        2.6         2.1       6.6
  Solidago
  Lomatium                  6.4        1.3         3.9       4.5
  Lupinus                   1.0        4.4         5.4       2.7
  Other forbs each <5%     33.2       45.8        33.1      36.8
Total Graminoids            7.2        8.2         7.0       9.6
Total Other                1.3        0.6         1.6        3.2

TABLE 5. Fecal nitrogen (%) and 2,6 diaminopimelic acid (DAPA; mg
[g.sup.-1]) from composite samples of pellets collected from
migrant and non-migrant Yellowstone Pronghorn during May-August 2006.

                         Non-migrants

Nutrition Index   May    July   August

Fecal Nitrogen
Mean              2.84   2.37   2.53
SE                0.15   0.06   0.10
DAPA
Mean              0.65   0.56   0.43
SE                0.07   0.01   0.06
n                 4      14     3

                         Migrants

Nutrition Index   June   July   August

Fecal Nitrogen
Mean              4.14   2.80   2.75
SE                0.16   0.06   0.11
DAPA
Mean              0.80   0.49   0.47
SE                0.05   0.02   0.02
n                 5      21     8
COPYRIGHT 2017 Society for Northwestern Vertebrate Biology
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2017 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Barnowe-Meyer, Kerey K.; White, PJ; Davis, Troy L.; Treanor, John J.; Byers, John A.
Publication:Northwestern Naturalist: A Journal of Vertebrate Biology
Article Type:Report
Geographic Code:1USA
Date:Sep 1, 2017
Words:5744
Previous Article:Genetic characteristics of Red Foxes in Northeastern Oregon.
Next Article:Occurrence of amphibians in northern California coastal dune drainages.
Topics:

Terms of use | Privacy policy | Copyright © 2021 Farlex, Inc. | Feedback | For webmasters |