Printer Friendly

A novel method of performing moose browse surveys.

ABSTRACT: We measured browse availability and use along foraging paths of GPS radio-collared moose (Alces alces) in northeastern Minnesota to estimate diet composition and browse species preference. On foraging paths during summer and winter we counted twigs via traditional methods for comparison with a novel method that attempted to better simulate moose foraging behavior. Twigs were collected and used to develop diameter at point of browsing--biomass regressions for each browse species. These regressions, different under open and closed canopy, were used to estimate biomass consumption on foraging paths and to compare 4 approaches. The average diets were similar to previously measured regional diets, and importantly, our data identified variance among individual seasonal diets. Our field method allowed us to better quantify and compare diet composition and browse selection of individual free-ranging moose directly on foraging paths.

Key words: bite size, browse availability method, browse selection, diameter-biomass regressions, diet composition, Minnesota

**********

Large herbivores like moose (Alces alces) view their food resources at the landscape, patch, and feeding station levels (Senft et al. 1987). At the landscape level moose choose which patches to visit based on the spatial distribution of browse density and forage availability within each patch. At the patch level, moose must choose where to forage based on the available browse species, and tree and shrub heights at different feeding stations. Younger patches can provide large quantities of high quality browse while older patches that have grown out of reach provide less browse (Schwartz 1992). Within a feeding station, bite size is based on the tradeoff between cropping and processing (Spalinger and Hobbs 1992).

Moose need to consume about 130 g dry mass/kg body [weight.sup.0.75] daily in summer and about 40 g dry mass/kg body [weight.sup.0.75] daily in winter (Renecker and Hudson 1985). Using an average bite size of 1.02 g/bite (Renecker and Hudson 1986), this equates to at least 13,000 bites in summer and 4,000 bites in winter for a 454 kg (1000 lb) moose. Winter consumption may be up to 50% higher depending on browse availability and species composition (Hjeljord et al. 1994). This large demand for forage forces moose to move between patches and feeding stations in order to consume enough biomass.

Browse availability and bite size have been measured by following moose or moose tracks in snow and counting the number of available twigs per species, the number of bites per species, and measuring diameter at point of browsing, dry mass, and twig length (Risenhoover 1987, Shipley et al. 1998). Locations of moose were found via radio telemetry (Risenhoover 1987, Hjeljord et al. 1990) or finding a track crossing a road (Shipley et al. 1998). These methods were largely opportunistic and data collection was either clumped (location every hour for 2 days) or spread temporally (1-2 tracks weekly).

Another typical method is to measure browse availability in plots along randomly placed straight transects instead of following moose foraging paths. This provides an estimate of absolute browse density in a patch, rather than an estimate of browse availability encountered by moose. We measured intensively used feeding patches with 3 different protocols and a randomly placed straight transect in northeastern Minnesota. Our new protocol (the large feeding station method) attempted to simulate how a moose browses, which we contrasted with measurements along the foraging path and with absolute browse density.

STUDY AREA

This study was conducted in northeastern Minnesota where moose were previously collared for a VHF telemetry study (Fig. 1) (Lenarz et al. 2011). These forests transition between the Canadian boreal and northern hardwood forests and experience a continental climate with short warm summers and severe winters (Heinselman 1996). Most was part of the Superior National Forest with the remaining either state, county, tribal, or industrial forest land (Lenarz et al. 2010, Moen et al. 2011). More specific details are provided in the Minnesota Moose Research and Management Plan (MNDNR 2011).

METHODS

Regressions and Estimating Bite Mass

Summer leaves were collected between July and September 2012, and winter twigs between January and April 2012 and 2013; twigs from both years were combined in the regression analyses. We clipped (standard garden clippers) browsed (~3 cm below the browse point) and unbrowsed twigs of all browse species (Table 1). Samples were bagged and labeled with the location, date, and species. All browsed and unbrowsed twigs and leaves were stored at 2-3[degrees]C prior to measurements. These twigs were used to develop diameter-biomass regressions for each season (Telfer 1969). In summer we collected stripped twigs of each species which we clipped directly above the first unbrowsed petiole. A winter bite was equal to the twig biomass and a summer bite the leaf biomass from one twig, both with current annual growth >5 cm.

On browsed twigs we measured (nearest 0.01 mm) the diameter at point of browsing and on unbrowsed twigs the simulated diameter at point of browsing. In summer, the simulated point of browsing was the diameter underneath the last stripped petiole. The wet weight of winter twigs and stripped summer leaves was weighed to the nearest 0.01 g. After weighing the wet mass of leaves, they were placed in the same bag with the corresponding twig. All unbrowsed twigs in both seasons were stored in labeled bags.

All unbrowsed summer and winter twigs were dried at 60 [degrees]C for 48 h in a drying oven. Dried twigs in winter and dried leaves in summer were stored at room temperature before being weighed to the nearest 0.01 g. Most winter twigs (74%) and summer leaves (90%) were measured within 5 days of removal from the drying oven; the remainder was measured 6-9 days later.

GPS Collars

We captured adult moose in February and early March 2011 by darting them from helicopters. GPS radio-collars (Sirtrack Ltd. and Lotek Wireless) fitted to each moose were programmed to transmit a location every 20 min. Animal capture and handling protocols met the guidelines recommended by the American Society of Mammalogists (Sikes et al. 2011) and were approved by University of Minnesota and National Park Service Animal Care and Use committees (#0912A75532).

Measuring Browse Availability

Summer browse availability was measured between 25 July and 14 September 2012, and winter browse availability between 3 January and 22 March 2013. Browse availability was measured at the patch scale which we identified from the GPS locations--patches had a concentrated number of moose locations. We used a handheld Garmin GPS to reach our pre-identified patches and then searched for a feeding station to identify a foraging path. A feeding station was defined as a plant or clump of plants with browsed twigs that were accessible when the forefeet of a moose are stationary (Goddard 1968, Novellie 1978, Senft et al. 1987).

A foraging path was defined as a trail of feeding stations within a patch. Summer foraging paths were measured 1 to 15 days after the moose departed, and winter foraging paths were measured 3 to 17 days after departure. Patches were considered accessible if they were on public land and we could access them by walking <2 km on a trail and/or <550 m from a trail. We measured winter patches containing 29 foraging paths from 8 moose (6F, 2M), and summer patches containing 31 foraging paths from 7 moose (5F, 2M).

We defined a large feeding station as a location that appeared to have [greater than or equal to] 10 bites. At all sites we measured browse under 4 different protocols to produce 4 foraging path types: 1) large feeding stations along the foraging path, 2) random plots along the foraging path, 3) random feeding stations along the foraging path, and 4) plots along a straight transect through the area containing the foraging path. Each path type consisted of 10 measurement plots.

Large feeding station plots--The first large feeding station encountered was the first plot of the site and marked as a waypoint on the handheld GPS. The plot or feeding station to be measured was a half circle with radius of 99.1 cm (39 in), with the center of the back side (straight line diameter) held at the approximate place where the moose stood. Tracks in winter, other sign in either season, or placement of bites relative to open space were also used to determine where the moose stood and the direction it faced. At each large feeding station we counted the unbrowsed and browsed twigs of each browse species between 0.5 and 3 m above the ground (Table 1; Shipley et al. 1998). Each cut-off twig was considered a bite. Although an occasional large feeding station had <10 bites, we included it as a large feeding station because the observer estimated it had at least 10 bites. This only occurred at 10 of 290 (3%) large feeding stations in winter and 36 of 297 (12%) in summer.

We established the foraging path type from the first large feeding station by following tracks and browsing sign to the next large feeding station, marked it as the second waypoint on the GPS, and repeated the measurements (Fig. 2). Plots could not overlap and this process continued until 10 large feeding stations had been measured on the foraging path.

Random plots on the foraging path--We created the random plot path type by stopping along the foraging path and repeating our browse measurements in random plots. A list of random distances between 5 and 14 m was generated using Microsoft Excel, and in the field we established the random plots using these distances in the GPS "find" feature (Fig. 2).

Random feeding stations--If a random plot had been browsed (evident bites), then that random plot was also defined as a random feeding station. If no browsed bites were in the random plot, we followed the foraging path to the next browsed twig (even if only one bite) and this became the location of the next random feeding station (Fig. 2), eventually creating the random feeding path type.

Straight transect plots--After completing the large feeding station, random plot, and random feeding station measurements, we established a straight line transect that returned to the first plot. Along this transect we stopped at random distances between 5 and 14 m until 10 plots were measured. If we reached the first large feeding station plot before completing 10 plots, we lengthened the transect. If, however, the cover type changed past the first plot and <10 plots were measured, we established a new transect in a random direction within the same cover type; 10 of 29 straight transects were angled in winter and 15 of 31 in summer.

Some cover types had little available browse making the foraging path difficult to follow in summer when 10 of 30 foraging paths had <10 plots in all path types. If no bites were found within 20 m of the previous feeding station when moving forward, we assumed the moose stopped foraging. Effectively this meant that there were <10 large feeding stations, random feeding stations, and/or random plots in that foraging path. Snow tracking in winter allowed us to more easily identify the foraging path; thus, 10 plots in all path types were measured in 28 of 30 foraging paths.

Canopy cover was measured 3 times with a densiometer (every 8th plot) to produce an average value in each patch. Twigs collected from sites with 0-50% canopy closure were considered grown in open canopy, and twigs from sites with 70-100% canopy closure were considered grown in closed canopy. Twigs from sites with 51-69% canopy cover were not used in the regressions or bite size summary statistics.

Statistical Analyses

Biomass-diameter at point of browsing regressions, ANOVAs on browse density, Kruskal-Wallis comparisons of diet, Pearson [chi square] Goodness of Fit tests, and Bonferroni Z-tests were all performed in Jmp 10.0. Significance level was set at P = 0.05.

Regressions--Simulated diameters at point of browsing and dry masses of twigs from the unbrowsed winter twigs were [log.sub.10] transformed and used to make 2 separate diameter-biomass regressions for each of the main browse species. The first regression used twigs grown in open canopy (0-50% shaded) and the second twigs from closed canopy (70-100% shaded). Similarly, 2 summer regressions were made using leaf dry mass of each browse species. The raw data are found in Ward (2014) and only results are presented here.

Statistics on bite size diameter and bite mass were calculated for each species. A t-test was used to test for statistical differences between the average diameter at point of browsing in open and closed canopy in both seasons for each species.

Available browse density--Browse density was estimated as twig counts and as biomass. To obtain the total number of available twigs per path, we added the number of available twigs and the number of browsed bites. We estimated the total biomass originally available (browsed or unbrowsed) along a foraging path by multiplying the number of twigs of a given species by the average biomass of one bite of that species. For foraging paths in 0-50% shade, we used the average biomass values from open canopy regressions. Likewise, we used the average biomass values from closed canopy regressions for foraging paths in 51-100% shade. Although the closed canopy regressions were developed with twigs grown in 70-100% shaded areas, we felt the foraging paths in 51-69% shade were better classified as closed canopy than open canopy. Balsam fir was not included in summer browse density estimates because it is not typically part of the summer diet.

Available and consumed browse density along each of the 4 path types were estimated using twig counts and biomass in both seasons. The length of each path was calculated by measuring the length of a line passing through all of the plots of each path type. The area of the foraging path was considered twice this distance to represent the ability of moose to browse either side of the foraging path. To calculate browse density we divided the twig count (available or consumed) by the area of the foraging path. These same calculations were made using biomass and twig counts. The browse density on large feeding station paths was compared with those on the random feeding, random, and straight transect paths using an ANOVA of the log transformed data.

Diet composition--Diet composition was calculated for each moose on the 4 path types in both seasons. We made a weighted average of those diet compositions to estimate diet composition for all moose on each path type in winter and summer. Species were considered rare when they made up <1% of the average diet (Shipley et al. 1998) at large feeding station paths. The percentage of the diet consisting of rare species is reported in the tables (but not text) to illustrate how a few individual moose consumed many bites of rare species.

Each individual diet had at least one browse species not identified on the foraging paths. Because these data were not normally distributed and no transformation could correct this skewedness, we used a Kruskal-Wallis test to test for significant differences between diet composition on the 4 path types. A Kruskal-Wallis test was also used to test for differences between each individual diet.

Browse species selection--We also determined the selection for each browse species from a combined average of all moose and for each individual using the data from large feeding station paths. A Pearson [chi square] Goodness of Fit test and a Bonferroni Z-test were performed on the availability and use of all browse species for all moose combined and each individual moose (Neu et al. 1974). A species was considered "positively selected", "negatively selected", or neither if there was a significantly larger, smaller, or equal proportion of browsed versus available twigs.

RESULTS

Regressions

All of the twig diameter--biomass regressions had slopes significantly different from zero. The slopes ranged from 0.58-2.80 in winter and 0.45-2.07 in summer. In winter, 75% of the regressions had an [R.sup.2] >0.60, and in summer 43% had an [R.sup.2] >0.60. There was no consistent pattern between the open canopy or closed canopy regression slopes being larger or smaller (Ward 2014).

Bite Size

Across all species in winter, the mean diameter at point of browsing was 3.0 [+ or -] 0.02 mm in open canopy (range = 0.5-9.0 mm) and 3.1 [+ or -] 0.1 mm in closed canopy (range = 0.2-8.4 mm) (Table 2). In summer, the mean across species was 2.3 [+ or -] 0.02 mm in open canopy (range = 0.02-11.1 mm) and 2.4 [+ or -] 0.04 mm in closed canopy (range = 0.2-6.1 mm) (Table 3).

Using the regressions found in Ward (2014), we calculated the average biomass consumed per bite for each browse species (Tables 2 and 3). In winter, pin cherry had the largest bite size (2.3 [+ or -] 1.4 g) under closed canopy and the smallest bite size under open canopy (0.4 [+ or -] 0.1 g). Mountain maple had the smallest bite size under closed canopy (0.4 [+ or -] 0.2 g). Mountain ash had the largest (1.7 [+ or -] 1.4 g) and quaking aspen the smallest bite size (0.3 [+ or -] 0.2 g) under closed canopy in summer.

Bite Density at Feeding Stations

One purpose of establishing the random feeding station plots was to estimate the frequency of feeding stations of different sizes occurring along foraging paths. In winter 57% of random feeding station plots (n = 281) had [greater than or equal to] 10 or more bites, and in summer 49% (n = 267). In both seasons at least 80% of twig consumption on the foraging path was from feeding stations with [greater than or equal to] 10 bites, although moose occasionally consumed <10 bites at a station.

Browse Density

Total available browse density was measured at 29 patches in winter and 30 patches in summer. It was significantly different among the 4 path types in both seasons using either method (winter twigs: [F.sub.3,112] = 62.7, summer twigs: [F.sub.3,118] = 32.5, winter biomass: [F.sub.3,112] = 84.3, summer biomass: [F.sub.3,120] = 16.8, [P.sub.all] < 0.0001). Likewise, density of consumed browse was also significantly different in winter and summer among the 4 path types (winter twigs: [F.sub.3,112] = 63.4, summer twigs: [F.sub.3,120] = 31.2, winter biomass: [F.sub.3,112] = 70.9, summer biomass: [F.sub.3,119] = 5.0, [P.sub.all] < 0.0025). As expected, both available and consumed browse densities were highest at large feeding station paths, followed by random feeding station, random plot, and straight transect paths (Table 4).

The average available browse density estimated by biomass at large feeding stations was 53% higher in summer (15.2 [+ or -] 1.7 g/[m.sup.2]) than winter (9.9 [+ or -] 1.0 g/[m.sup.2]). Conversely, density estimated by twig counts was ~2.5x larger in winter (15.2 [+ or -] 1.6 twigs/[m.sup.2]) than in summer (5.9 [+ or -] 0.6 twigs/[m.sup.2]). Large feeding station paths had ~60% more available twigs (727 [+ or -] 3) in winter than in summer (460 [+ or -] 37), whereas the available biomass was ~2.5x larger in summer (1166 [+ or -] 88 g) than winter (471 [+ or -] 26 g). The same seasonal differences existed for consumed twigs and biomass. The distance walked in winter to complete the large feeding station paths (27.6 [+ or -] 2.0 m, n = 29) was about half that in summer (50.5 [+ or -] 4.9 m, n = 31).

The available and consumed browse density for each browse species was largest at large feeding station paths followed by random feeding station, random plot, and straight transect paths. The one exception (based on twig count) was that the highest browse density of hazel was found on the straight transect path in summer (when hazel is rarely consumed).

Consumption Rate

The pattern of consumption rate was similar to that of consumed browse density. The proportion of consumed twigs was highest on the large feeding station paths and declined progressively to the random feeding station, random plot, and straight transect paths. Consumption was 45% in summer and 35% in winter on the large feeding station paths. Overall, it was 23-45% on all paths except the straight transects where rates were 13% in winter and 9% in summer.

Diet Composition

Season--At least 70% of all bites (all moose) consumed in winter along the 4 path types consisted of hazel, paper birch, willow, and quaking aspen. The remaining 30% consisted of balsam fir, juneberry, mountain maple, red maple, red-osier dogwood, pin cherry, and choke cherry. Rare species were alder, mountain ash, balsam poplar, and white pine (Table 5).

In summer 70% of bites consisted of mountain maple, willow, and paper birch on large feeding station, random feeding station, and random plot paths. The remaining 30% was juneberry, red maple, pin cherry, choke cherry, quaking aspen, and mountain ash. Rare species were hazel, balsam poplar, red-osier dogwood, balsam fir, alder, bog birch, black ash, oak, elderberry, and white pine. On straight transects at least 70% of consumed twigs were mountain maple, willow, quaking aspen, and species considered rare (Table 5).

Path type--Despite the general similarities in diet diversity, all browse species comprised different portions of the winter diet on the 4 path types (Kruskal-Wallis, [H.sub.3] > 12.3, P < 0.007) except paper birch and hazel (Kruskal-Wallis, [H.sub.3] < 1.2, P > 0.60; Table 6). In summer Juneberry, quaking aspen, and mountain ash comprised different portions of the diet on all 4 path types in summer (Kruskal-Wallis, [H.sub.3] > 8.1, P < 0.045; Table 5). No difference existed among the 4 path types for red maple, mountain maple, paper birch, cherry, and willow (Kruskal-Wallis, [H.sub.3] < 5.7, P > 0.13).

Individuals--Diets based on twigs consumed on large feeding station paths varied individually and from the pooled average (Tables 6 and 7). One winter example of this individual difference was female moose 31180 that consumed 26% red maple and 50% hazel (4 paths combined) compared to the group average of 5% red maple and 26% hazel (Table 6); red maple was more available in her foraging patches. An example in summer was male moose 31190 that consumed 10% mountain maple and 61% willow (4 paths combined) compared to the group average of 41% mountain maple and 21% willow (Table 7).

Browse Species Selection

The average diet in winter (all moose combined) was different from that available ([[chi square].sub.9] = 3122, P < 0.0001). A Bonferroni Z-test on the combined data indicated that juneberry, red maple, mountain maple, paper birch, red-osier dogwood, and quaking aspen were eaten more than available in summer. Hazel was eaten less than available, and cherry and willow were used in proportion to availability (Table 8). Individual diets were also different from browse availability on their respective foraging paths (all moose: [[chi square].sub.[less than or equal to]9] [greater than or equal to] 74.6, P < 0.0001 for all moose).

The average summer diet (all moose combined) was also different from available ([[chi square].sub.8] = 840, P < 0.0001), as were individual diets (all moose: [[chi square].sub.[less than or equal to]8] [greater than or equal to] 43.9, P < 0.0001). A Bonferroni Z-test on the combined summer data indicated that red maple, mountain maple, cherry, and mountain ash were eaten more than available in summer, willow less than available, and juneberry, paper birch, and quaking aspen proportional to availability (Table 8).

DISCUSSION

We initially chose to measure large feeding stations ([greater than or equal to] 10 bites) because field observations indicated that these sites were common and theory (Senft et al. 1987) supports the strategy of such foraging behavior. By contrasting browse density along a foraging path at large feeding stations with alternate routes, we demonstrated how moose increased effective browse density by selecting a specific foraging path. For example, moose took at least 80% of their bites at large feeding stations with [greater than or equal to] 10 bites. The identification of large feeding stations provided a fast and efficient manner to measure browse availability and consumption along presumed foraging paths, and this method can also be used to evaluate the relative quality of browsed and unbrowsed patches (Ward 2014, Ward and Moen 2014)

This method avoids 2 potential complications associated with the straight transect method: 1) measuring random locations, and 2) empty plots. The foraging path approach eliminates these concerns by ensuring plentiful data at actual foraging locations. Arguably, it also reflects the browse availability a moose would actually perceive. Randomly placed plots in straight transects are often empty, which would mean that many more plots would be required to accurately estimate the availability of patchy browse. Our method avoids empty plots, incorporates distance moved between feeding stations, and provides an estimate of effective browse density. A challenge to simulating foraging decision rules when following a foraging path is that humans find large feeding stations by sight, but moose likely use other senses as well.

Diet composition was statistically different among seasons and path types. The average combined diet in both winter and summer was best categorized as generalist because one genus did not account for >60% of the diet (Shipley 2010). The two primary browsed species were hazel and paper birch in winter and mountain maple and willow in summer, hence, moose may forage in different areas in winter and summer. For example, available browse density estimated by twig counts was higher in winter than in summer, with hazel consumed commonly in winter but rarely in summer. Use of GPS locations may help distinguish seasonal differences in foraging locations and browse species availability.

The diet composition was similar to that measured >3 decades previously in the region (Peek et al. 1976). The top 5 summer species (percent of diet) were the same in both studies: mountain maple, willow, paper birch, cherry, and quaking aspen. Mountain maple was ranked first in our study and fifth by Peek et al. (1976), and quaking aspen had the opposite rankings. Hazel, willow, and quaking aspen were 3 of the top 5 winter species in both studies. One difference was that paper birch and juneberry were included in our top 5, whereas Peek et al. (1976) had balsam fir and red-osier dogwood. During both seasons the primary species consumed were consistent regardless of path type. Because more twigs were counted on the large feeding station paths, they probably provided the better estimate of diet and species consumption rates.

This study was unique because we collected data from individual free-ranging moose by using their GPS locations to identify their foraging paths shortly after use. Presumably each moose selected browse based on availability within the patch they occupied. Individual consumption differences occurred in both winter and summer, and though previous studies have not provided for analysis and comparison of individual diet selection, individual differences in habitat selection by moose were documented in British Columbia (Gillingham and Parker 2010). Pooling the data from many foraging paths identified the generalized seasonal diets and the most important browse species in this region, and concurred with previous research. It also identified individual diet variation which suggests that moose adapt their diet based on the local composition and availability of browse species.

We were able to simulate how a moose browsed in a patch using the large feeding station method. There was some subjectivity in choosing which large feeding station was closest (consecutive) when establishing the foraging path; however, a moose would face the same choice. Contrasting browse measurements between simulated and actual foraging paths in the same patch would provide a good evaluation of our approach and potential differences. We offer that incorporating large feeding stations and the distance between adjacent large feeding stations is an efficient method to estimate browse availability at the patch level.

ACKNOWLEDGEMENTS

We would like to thank the EPA Great Lakes Restoration Initiative and the Minnesota Environment and Natural Resources Trust Fund (ENRTF) for funding and N. Bogyo of the 1854 Treaty Authority for winter field work assistance.

REFERENCES

GILLINGHAM, M. P., and K. L. PARKER. 2010. Differential habitat selection by moose and elk in the Besa-Prophet area of northern British Columbia. Alces 44: 41-63.

GODDARD, J. 1968. Food preferences of two black rhinoceros populations. African Journal of Ecology 6: 1-18.

HEINSELMAN, M. 1996. The Boundary Waters Wilderness Ecosystem. University of Minnesota Press, Minneapolis, Minnesota, USA.

HJELJORD, O., N. HOVIK, and H. B. PEDERSEN. 1990. Choice of feeding sites by moose during summer, the influence of forest structure and

plant phenology. Holarctic Ecology 13:281-292.

--, B. E. SAETHER, and R. ANDERSEN. 1994. Estimating energy intake of free-ranging moose cows and calves through collection of feces. Canadian Journal of Zoology 72: 1409-1415.

LENARZ, M. S. 2011. 2011 Aerial Moose Survey. Minnesota Department of Natural Resources, St. Paul, Minnesota, USA.

(MNDNR) Minnesota Department of Natural Resources. 2011. Minnesota Moose Research and Management Plan. Minnesota Department of Natural Resources, St. Paul, Minnesota, USA.

MOEN, R. A., R. PETERSON, S. WINDELS, L. FRELICH, D. BECKER, and M. JOHNSON. 2011. Minnesota Moose Status: Progress on Moose Advisory Committee Recommendations. NRRI Technical Report No. NRRI/TR-2011/41. Natural Resources Research Institute, Duluth, Minnesota, USA.

NOVELLIE, P. A. 1978. Comparison of the foraging strategies of blesbok and springbok on the Transvaal Highveld. South African Journal of Wildlife Research 8: 137-144.

NEU, C. W., C. R. BYERS, and J. M. PEEK. 1974. A technique for analysis of utilization-availability data. Journal of Wildlife Management 38: 541-545.

PEEK, J. M., D. L. URICH, and R. J. MACKIE. 1976. Moose habitat selection and relationships to forest management in north-eastern Minnesota. Wildlife Monographs 48: 3-65.

RENECKER, L. A., and R. J. HUDSON. 1985. Estimation of dry matter intake of free-ranging moose. Journal of Wildlife Management 49: 785-792.

--, and --. 1986. Seasonal foraging rates of free-ranging moose. Journal of Wildlife Management 50: 143-147.

RISENHOOVER, K. L. 1987. Wintering foraging strategies of moose in subarctic and boreal forest habitats. Ph. D. Thesis, Michigan Technical University, Houghton, Michigan, USA.

SCHWARTZ, C. C. 1992. Physiological and nutritional adaptations of moose to northern environments. Alces Supplement 1: 139-155.

SENFT, R. L., M. B. COUGHENOUR, D. W. BAILEY, L. R. RITTENHOUSE, O. E. SALA, and D. M. SWIFT. 1987. Large herbivore foraging and ecological hierarchies. Bioscience 37: 789-799.

SHIPLEY, L. A. 2010. Fifty years of food and foraging in moose: lessons in ecology from a model herbivore. Alces 46: 1-13.

--, S. BLOMQUIST, and K. DANELL. 1998. Diet choices made by free-ranging moose in northern Sweden in relation to plant distribution, chemistry, and morphology. Canadian Journal of Zoology 76: 1722-1733.

SIKES, R. S., and W. L. GANNON. 2011. The Animal Care and Use Committee of the American Society of Mammalogists. (2011). Journal of Mammalogy 92: 235-253.

SPALINGER, D. E., and N. T. HOBBS. 1992. Mechanisms of foraging in mammalian herbivores: new models of functional response. The American Naturalist 140: 325-348.

TELFER, E. S. 1969. Twig weight-diameter relationships for browse species. Journal of Wildlife Management 33: 917-921.

WARD, R. L. 2014. Browse availability, bite size, and effects of stand age on species composition and browse density for moose in northeastern Minnesota. M.S. Thesis, University of Minnesota, Minneapolis, Minnesota, USA.

--, and R. A. Moen. 2014. Effects of stand age on species composition and browse density in northeastern Minnesota. NRRI Technical Report No. 2014-36. Natural Resources Research Institute, Duluth, Minnesota, USA.

Rachel L.W. Portinga (1,2,3) and Ron A. Moen (1,2)

(1) Biology Department, University of Minnesota Duluth, 1049 University Drive, Duluth, MN 55812; (2) University of Minnesota Duluth Natural Resources Research Institute, 5013 Miller Trunk Hwy, Duluth, MN, 55811

(3) Present Address: Hibbing Community College, 1515 25th St E, Hibbing, MN 55746

Table 1. The common and scientific names for each potential browse
species in northeastern Minnesota and seasons in which each species
is consumed. "Rare" species make up <1% of the diet at large feeding
station paths. "Not Browsed" species were not consumed along the
foraging paths.

Common Name         Scientific Name         Winter        Summer

Balsam fir          Abies balsamea          Common        Not Browsed
Red maple           Acer rubrum             Common        Common
Mountain maple      Acer spicatum           Common        Common
Alder               Ain us rugosa           Rare          Rare
Juneberry           Amelanchier spp.        Common        Common
Paper birch         Betula papyrifera       Common        Common
Bog birch           Betula pumila           Not Browsed   Rare
Red-osier dogwood   Cornus stolonifera      Common        Rare
Hazel               Corylus cornuta         Common        Rare
Black ash           Fraxinus niger          Not Browsed   Rare
White pine          Pinus strobus           Rare          Rare
Balsam poplar       Populus balsamifera     Rare          Rare
Quaking aspen       Populus tremuloides     Common        Common
Pin cherry          Prunus pennsylvanicus   Common        Common
Choke cherry        Prunus virginianus      Common        Common
Oak                 Quercus spp.            Not Browsed   Rare
Willow              Salix spp.              Common        Common
Elderberry          Sambucus pubens         Not Browsed   Rare
Mountain ash        Sorbus decora           Rare          Common

Table 2. Summary statistics on browsed twigs in winter for all
browse species. Open canopy indicates twigs grown in locations
shaded 0-50% and closed canopy indicates twigs grown in locations
shaded 70-100%. P-values indicate t-test results between the
diameter at point of browsing (DPB) of each species in open and
closed canopy. We did not find enough individual twigs of juneberry,
paper birch, pin cherry, or willow in closed canopy to calculate
reliable averages for those categories.

                              Diameter at Point of Browsing (mm)

Species         Canopy      Average [+ or -] SE   Minimum   Maximum

Balsam fir **   Open         2.7 [+ or -] 0.1        0.9       6.5
                Closed       2.2 [+ or -] 0.1        1.0       4.0

Red maple **    Open         3.5 [+ or -] 0.1        1.3       7.4
                Closed       4.1 [+ or -] 0.1        2.7       6.9

Mountain        Open         2.8 [+ or -] 0.3        1.5       4.6
maple *         Closed       2.4 [+ or -] 0.3        0.4       4.9

Juneberry       Open         2.4 [+ or -] 0.1        0.9       4.5
                Closed              NA                NA        NA

Paper birch     Open         2.7 [+ or -] 0.1        0.6       4.8
                Closed              NA                NA        NA

Hazel           Open         2.7 [+ or -] 0.1        1.1       5.3
                Closed       2.8 [+ or -] 0.1        1.1       4.5

Red-osier       Open         3.5 [+ or -] 0.1        1.5       6.1
dogwood ***     Closed       4.3 [+ or -] 0.2        2.0       6.6

Quaking         Open         3.5 [+ or -] 0.1        0.9       6.8
aspen           Closed       3.2 [+ or -] 0.1        1.0       5.7

Pin cherry      Open         2.4 [+ or -] 0.1        0.6       4.9
                Closed              NA                NA        NA

Choke cherry    Open         3.0 [+ or -] 0.3        1.5       4.8
                Closed       2.6 [+ or -] 0.4        0.2       4.1

Willow          Open         3.1 [+ or -] 0.1        0.5       6.4
                Closed (1)         NA                NA        NA

Mountain        Open         4.3 [+ or -] 0.1        1.6       6.8
ash *           Closed       3.7 [+ or -] 0.1        1.2       8.4

Combined        Open         3.0 [+ or -] 0.02       0.5       9.0
                Closed       3.1 [+ or -] 0.1        0.2       8.4

                              Diameter at Point of Browsing (mm)

                                  Average
Species         Canopy      Bite [+ or -] SE (g)    n        P

Balsam fir **   Open          1.6 [+ or -] 0.3      82     0.002
                Closed        1.2 [+ or -] 0.2      50

Red maple **    Open          0.7 [+ or -] 0.3     125     0.009
                Closed        1.4 [+ or -] 0.5      27

Mountain        Open          0.6 [+ or -] 0.3      47     0.019
maple *         Closed        0.4 [+ or -] 0.2      56

Juneberry       Open          0.5 [+ or -] 0.1     161     0.583
                Closed               NA              8

Paper birch     Open          0.8 [+ or -] 0.1     188      NA
                Closed               NA              7

Hazel           Open          0.6 [+ or -] 0.1     301     0.104
                Closed        0.6 [+ or -] 0.1     132

Red-osier       Open          1.1 [+ or -] 0.1     332    <0.0001
dogwood ***     Closed        1.4 [+ or -] 0.4      40

Quaking         Open          0.9 [+ or -] 0.1     209     0.155
aspen           Closed        0.7 [+ or -] 0.4      32

Pin cherry      Open          0.4 [+ or -] 0.1     216      NA
                Closed               NA              6

Choke cherry    Open          0.7 [+ or -] 0.1      53     0.120
                Closed        0.4 [+ or -] 0.1      20

Willow          Open          0.9 [+ or -] 0.1     501      NA
                Closed (1)           NA              0

Mountain        Open          1.3 [+ or -] 0.3      43     0.045
ash *           Closed        0.7 [+ or -] 0.5      53

Combined        Open                 NA            2388
                Closed               NA            454

Table 3. Summary statistics on browsed twigs of all species in
summer. Open canopy indicates twigs grown in locations shaded 0-50%
and closed canopy indicates twigs grown in locations shaded 70-100%.
P-values indicate t-test results between the diameter at point
of browsing (DPB) of each species in open and closed canopy. We did
not find enough individual twigs of red maple in open canopy or pin
cherry, willow, or mountain ash in closed canopy to calculate
reliable averages for those categories.

                           Diameter at Point of Browsing (mm)

Species        Canopy   Mean [+ or -] SE    Minimum   Maximum

Red maple      Open            NA               NA        NA
               Closed   2.8 [+ or -] 0.2       1.3       6.0

Mountain       Open     2.3 [+ or -] 0.03      0.5       4.7
maple ***      Closed   3.0 [+ or -] 0.1       0.5       4.9

Juneberry      Open     1.6 [+ or -] 0.04      0.1       3.2
               Closed   2.1 [+ or -] 0.3       0.2       4.2

Paper          Open     2.3 [+ or -] 0.1      0.02       5.1
birch **       Closed   2.0 [+ or -] 0.1       0.6       3.8

Hazel          Open     1.6 [+ or -] 0.1       0.5       3.5
               Closed   1.6 [+ or -] 0.1       0.6       2.5

Red-osier      Open     2.9 [+ or -] 0.1       1.5       5.7
dogwood ***    Closed   2.1 [+ or -] 0.2       0.5       4.4

Quaking        Open     3.1 [+ or -] 0.2       0.5      11.1
aspen ***      Closed   1.6 [+ or -] 0.1       0.3       4.3

Pin cherry     Open     2.2 [+ or -] 0.1       0.6       4.2
               Closed          NA               NA        NA

Choke cherry   Open     2.2 [+ or -] 0.1       1.0       4.1
               Closed   2.0 [+ or -] 0.1       0.8       3.9

Willow ***     Open     2.3 [+ or -] 0.1       0.5       5.5
               Closed          NA               NA        NA

Mountain ash   Open     4.0 [+ or -] 0.1       2.0       7.0
               Closed          NA               NA        NA

All Species    Open     2.3 [+ or -] 0.02     0.02      11.1
               Closed   2.4 [+ or -] 0.04      0.2       6.1

                          Diameter at Point of Browsing (mm)

                            Mean Bite
Species        Canopy    [+ or -] SE (g)     n        P

Red maple      Open            NA            14     0.349
               Closed   1.4 [+ or -] 0.3     27

Mountain       Open     0.7 [+ or -] 0.1    675    <0.0001
maple ***      Closed   1.0 [+ or -] 0.1    264

Juneberry      Open     0.5 [+ or -] 0.04   149     0.145
               Closed   1.0 [+ or -] 0.4     20

Paper          Open     0.8 [+ or -] 0.1    316     0.003
birch **       Closed   0.5 [+ or -] 0.1     84

Hazel          Open     0.7 [+ or -] 0.04   105     0.739
               Closed   0.6 [+ or -] 0.1     48

Red-osier      Open     1.3 [+ or -] 0.1     41     0.001
dogwood ***    Closed   0.7 [+ or -] 0.1     26

Quaking        Open     1.4 [+ or -] 0.2    169    <0.0001
aspen ***      Closed   0.3 [+ or -] 0.2     53

Pin cherry     Open     0.8 [+ or -] 0.1     53      NA
               Closed          NA             0

Choke cherry   Open     0.8 [+ or -] 0.1     44     0.085
               Closed   0.8 [+ or -] 0.1     80

Willow ***     Open     0.9 [+ or -] 0.1    242    <0.0001
               Closed          NA            14

Mountain ash   Open     1.1 [+ or -] 0.1     72     0.802
               Closed          NA             7

All Species    Open            NA           2071     NA
               Closed          NA           627

Table 4. Available browse density and consumed browse density along
four path types in summer and winter measured by twigs/[m.sup.2]
[+ or -] SE and biomass (g)/[m.sup.2] [+ or -] SE. W = winter,
S = summer.

                                  Large Feeding      Random Feeding
             Method    Season        Station             Station

Available    # Twigs     W      15.4 [+ or -] 1.6   2.3 [+ or -] 0.2
                         S       5.9 [+ or -] 0.6   2.0 [+ or -] 0.2

             Biomass     W       9.9 [+ or -] 1.0   1.7 [+ or -] 0.1
                         S      15.2 [+ or -] 1.7   6.8 [+ or -] 1.9

Consumed     # Twigs     W       5.3 [+ or -] 0.6   2.1 [+ or -] 0.1
                         S       2.7 [+ or -] 0.3   1.0 [+ or -] 0.3

             Biomass     W       4.0 [+ or -] 0.4   0.5 [+ or -] 0.04
                         S       6.7 [+ or -] 0.7   2.4 [+ or -] 0.4

             Method    Season      Random Plot      Straight Transect

Available    # Twigs     W      2.0 [+ or -] 0.2    1.4 [+ or -] 0.2
                         S      1.8 [+ or -] 0.3    1.1 [+ or -] 0.1

             Biomass     W      1.5 [+ or -] 0.1    1.0 [+ or -] 0.1
                         S      4.5 [+ or -] 0.8    2.9 [+ or -] 0.4

Consumed     # Twigs     W      0.5 [+ or -] 0.1    0.2 [+ or -] 0.03
                         S      0.4 [+ or -] 0.1    0.1 [+ or -] 0.03

             Biomass     W      0.4 [+ or -] 0.04   0.2 [+ or -] 0.02
                         S      1.0 [+ or -] 0.2    0.3 [+ or -] 0.04

Table 5. Diet composition (average percent of diet [+ or -] SE)
measured on four path types. Averages and SE were weighted by moose.
Rare includes species that made up <1% of the diet at large feeding
station paths. 29 foraging paths were measured in winter 2013 and 31
were measured in summer 2012.

                                     Winter

                       Large Feeding        Random Feeding
Species                   Station              Station

Hazel                  27 [+ or -] 7        26 [+ or -] 8
Paper birch            26 [+ or -] 7        26 [+ or -] 6
Willow                 11 [+ or -] 5        14 [+ or -] 6
Quaking aspen           7 [+ or -] 3         8 [+ or -] 4
Juneberry               6 [+ or -] 2         5 [+ or -] 2
Red maple               5 [+ or -] 3         4 [+ or -] 2
Red-osier dogwood       5 [+ or -] 4         3 [+ or -] 3
Balsam fir              4 [+ or -] 2         6 [+ or -] 2
Mountain maple          4 [+ or -] 3         3 [+ or -] 1
Cherry                  3 [+ or -] 1         2 [+ or -] 1
Rare                    2 [+ or -] 2         2 [+ or -] 1

                                     Summer

Mountain maple         42 [+ or -] 11       45 [+ or -] 10
Willow                 21 [+ or -] 8        21 [+ or -] 9
Paper birch            11 [+ or -] 3         9 [+ or -] 4
Cherry                  9 [+ or -] 4         7 [+ or -] 4
Quaking aspen           8 [+ or -] 4        10 [+ or -] 3
Mountain ash            4 [+ or -] 2         3 [+ or -] 2
Juneberry               2 [+ or -] 1         3 [+ or -] 2
Red maple               1 [+ or -] 1              0
Rare                    1 [+ or -] 0.3       1 [+ or -] 0.4

                                     Winter

                                               Straight
Species                 Random Plot            Transect

Hazel                  27 [+ or -] 9        28 [+ or -] 8
Paper birch            25 [+ or -] 6        18 [+ or -] 6
Willow                 13 [+ or -] 6        11 [+ or -] 5
Quaking aspen          10 [+ or -] 5        13 [+ or -] 6
Juneberry               4 [+ or -] 1         4 [+ or -] 2
Red maple               5 [+ or -] 3         4 [+ or -] 4
Red-osier dogwood       3 [+ or -] 3        10 [+ or -] 11
Balsam fir              6 [+ or -] 3         2 [+ or -] 2
Mountain maple          2 [+ or -] 1         2 [+ or -] 1
Cherry                  2 [+ or -] 1         2 [+ or -] 1
Rare                    2 [+ or -] 1         5 [+ or -] 6

                                     Summer

Mountain maple         43 [+ or -] 11       25 [+ or -] 11
Willow                 28 [+ or -] 11       23 [+ or -] 11
Paper birch             6 [+ or -] 4         6 [+ or -] 5
Cherry                  6 [+ or -] 4         3 [+ or -] 5
Quaking aspen           8 [+ or -] 3        14 [+ or -] 7
Mountain ash            4 [+ or -] 4              0
Juneberry               2 [+ or -] 1         8 [+ or -] 5
Red maple                    0               7 [+ or -] 4
Rare                  0.2 [+ or -] 0.1      10 [+ or -] 7

Table 6. Diet composition of individual moose in winter 2013
measured by twigs consumed at large feeding station paths. There are
diets for eight collared moose. 31189 and 31190 are male, the rest
are females. N is the number of foraging paths measured. Rare
species made up <1% of the combined moose diet at large feeding
stations.

                                          Moose Number

Species              All Moose   31166   31174   31175   31178

Hazel                   27        21      38      29      13
Paper birch             26        14      41      15      57
Willow                  11         5               9       6
Quaking aspen            7        28      16      12      <1
Juneberry                6        18               1       8
Red maple                5                                26
Red-osier dogwood        5                15      <1      38
Balsam fir               4         2       4      15       1
Mountain maple           4        16       1               1
Cherry                   3        11       1       5       6
Rare                     1         2       5       1
N                       29         2       2       3       3

                              Moose Number

Species              31180   31182   31189   31190

Hazel                 50      33       9      68
Paper birch            9       3      56       3
Willow                 5       3
Quaking aspen          8       2
Juneberry              9       1
Red maple              9
Red-osier dogwood      4
Balsam fir            14
Mountain maple        25
Cherry                <1       3       6
Rare
N                      4       2       5       3

Table 7. Diet composition of individual moose in summer 2012
measured by twigs consumed at large feeding stations only. There are
diets for seven collared moose. 31189 and 31190 are male, the rest
are females. N is the number of sites measured. Rare species made up
<1% of the combined moose diet at large feeding stations.

                                         Moose Number

Species           All Moose    31166     31168     31175     31178

Mountain maple       41          3        57        84        90
Willow               21         53         3         9
Paper birch          11         12                             1
Cherry                9          8         5         3         2
Quaking aspen         8          4        36
Mountain ash          4         17                             5
Juneberry             2
Red maple             1
Rare                  1                              1         1
N                    31          3         2         3         3

                         Moose Number

Species            31180     31189     31190

Mountain maple      36        57        10
Willow              17                  61
Paper birch         17        13         7
Cherry              24         1         3
Quaking aspen        1        23         2
Mountain ash         5                   3
Juneberry                      1        12
Red maple                      5
Rare                                     3
N                    3         6         4

Table 8. Browse species selection in both seasons when data from all
moose was combined. If the moose were simply browsing at random, we
would expect the 95% confidence interval of the percent browsed to
contain the percent available at large feeding stations.

                              Percent
                             Available
                             at Large      95% Confidence Interval of
                              Feeding       Percent Browsed at Large
Season        Species        Stations           Feeding Stations

Winter       Juneberry          4.7      5.1 [less than or equal to] -
                                           [greater than or equal to]
                                                      6.8

             Red maple          3.3      3.8 [less than or equal to] -
                                           [greater than or equal to]
                                                      5.3

          Mountain maple        2.7      4.0 [less than or equal to] -
                                           [greater than or equal to]
                                                      5.5

            Paper birch        19.3       24.7 [less than or equal to]
                                          - [greater than or equal to]
                                                      27.9

         Red-osier dogwood      2.1      3.3 [less than or equal to] -
                                           [greater than or equal to]
                                                      4.8

           Quaking aspen        5.6      5.8 [less than or equal to] -
                                           [greater than or equal to]
                                                      7.6

              Cherry            3.0      2.7 [less than or equal to] -
                                           [greater than or equal to]
                                                      4.0

              Willow           11.9       11.2 [less than or equal to]
                                          - [greater than or equal to]
                                                      13.5

            Balsam fir          9.0      2.8 [less than or equal to] -
                                           [greater than or equal to]
                                                      4.1

               Hazel           36.8       26.3 [less than or equal to]
                                          - [greater than or equal to]
                                                      29.5

Summer       Red maple          0.5      0.6 [less than or equal to] -
                                           [greater than or equal to]
                                                      1.3

          Mountain maple       27.6       34.6 [less than or equal to]
                                          - [greater than or equal to]
                                                      38.2

              Cherry            7.2      8.3 [less than or equal to] -
                                           [greater than or equal to]
                                                      10.5

           Mountain ash         4.2      8.6 [less than or equal to] -
                                           [greater than or equal to]
                                                      10.8

             Juneberry          3.3      2.2 [less than or equal to] -
                                           [greater than or equal to]
                                                      3.4

            Paper birch        10.4      9.8 [less than or equal to] -
                                           [greater than or equal to]
                                                      12.1

           Quaking aspen        8.1      6.1 [less than or equal to] -
                                           [greater than or equal to]
                                                      8.1

              Willow           28.6       18.9 [less than or equal to]
                                          - [greater than or equal to]
                                                      21.9

Season        Species        Selection

Winter       Juneberry           +

             Red maple           -

          Mountain maple         +

            Paper birch          +

         Red-osier dogwood       +

           Quaking aspen         +

              Cherry             0

              Willow             0

            Balsam fir           -

               Hazel             -

Summer       Red maple           +

          Mountain maple         +

              Cherry             +

           Mountain ash          +

             Juneberry           0

            Paper birch          0

           Quaking aspen         0

              Willow             -
COPYRIGHT 2015 Alces
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2015 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Portinga, Rachel L.W.; Moen, Ron A.
Publication:Alces
Article Type:Statistical table
Geographic Code:1U4MN
Date:Jan 1, 2015
Words:7963
Previous Article:Variation in fine-scale movements of moose in the upper Koyukuk River drainage, Northcentral Alaska.
Next Article:Shoot growth responses at supplementary feeding stations for moose in Norway.
Topics:

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