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Abstract

Population densities are costly and logistically infeasible to measure directly across the broad geographic ranges of many wildlife species. For snowshoe hares (Lepus americanus), a keystone species in northern boreal forest, indirect approaches for estimating population densities based on fecal pellet densities have been developed for boreal forest in northwestern Canada and in conifer-dominated montane forest in Idaho. Previous authors cautioned against applying these estimates across the geographic range of hares without further testing, but no published relationships for estimating densities from pellet counts are available for the mixed conifer–deciduous forests of the southeastern portion of the hare's range in North America. Thus, we estimated pellet and hare densities in 12 forested stands, 4 sampled twice during 1981–1983 and 8 sampled once during 2000–2002. Mark–recapture estimated densities of snowshoe hares from eastern and western Maine during 1981–1983 were linearly related to pellet densities to 15,000 pellets/ha/month (1.5 hares/ha) (Adj. r2 = 0.87, n = 8, P < 0.001) and accurately predicted densities of hares (x̄ = 7 % greater) estimates than actually observed at higher pellet densities sampled in northern Maine during 2000–2002.

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... Fecal pellet counts have been used to estimate hare relative abundance and have been calibrated with population estimates to develop regression equations that can be used to estimate hare density from pellet counts (Pietz and Tester 1983, Fuller and Heisey 1986, Krebs et al. 1987. Equations have been developed in the western and eastern hare range but have not been developed in the central portion of the hare range (Murray et al. 2002, Homyack et al. 2006. The relationship between hare numbers and pellet counts varies across the hare range and using western and eastern equations to estimate hare numbers from pellet counts in the central portion of the hare range could yield inaccurate population estimates (Homyack 2003, Mills et al. 2005, McCann 2006). ...
... We then compared equations developed using annual pellet counts with equations developed using semiannual counts and compared equations developed using functional regression with equations developed using linear regression. We expected that using semiannual pellet counts with functional regression would improve the correlation between hare numbers and pellet counts because semiannual counts would reduce the effect of seasonal variation in pellet deposition and decomposition rates and because functional regression has been preferred in similar studies (Mills et al. 2005, Homyack et al. 2006. Lastly, we identified minimum mean pellet counts expected to support lynx in Minnesota, USA, given the current understanding of the relationship between hare numbers and lynx persistence. ...
... We restrained captured hares in cloth handling bags, recorded body mass and applied one uniquely numbered ear tag (Dalton I.D. Systems, Henley-on-Thames, Oxfordshire, United Kingdom) to each ear. We calculated number of hares per hectare using minimum number alive estimates divided by an effective trapping area (ETA) calculated for each grid (Boutin 1984, Boutin et al. 1985, Homyack et al. 2006. We used an ETA equaling the grid area plus a buffer that was one-half the mean maximum distance moved between trap stations per trapping session (Litvaitis 1990, Mills et al. 2005. ...
Article
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We calibrated snowshoe hare (Lepus americanus) numbers with pellet counts in Minnesota, USA, to understand the relationship between hare numbers and pellets in the central portion of the hare range. We found a strong and significant correlation between hare numbers and pellet counts using either linear or functional regression with either annual or semiannual pellet counts. Equations we developed using linear or functional regression predicted >1 hare/ha at similar pellet-density thresholds. These equations can be used to efficiently identify habitats that support hare numbers necessary for Canada lynx (Lynx canadensis) persistence in Minnesota.
... Although pellet counts are noninvasive, efficient, cheap, and have repeatedly been used to monitor lagomorph populations, pellet counts give only an index of the population of interest (Krebs et al. 1987, Anderson 2001, Murray et al. 2002. A more rigorous method to monitor lagomorphs is to establish a correlation between lagomorph abundance and lagomorph pellet density (Wood 1988, Krebs et al. 2001, Murray et al. 2002, Homyack et al. 2006, McCann et al. 2008. ...
... Densities estimated from capture-recapture methods likely provide more accurate population estimates than minimum number alive estimates commonly used to relate pellets to capture estimates (Homyack et al. 2006). When studies have used estimated rabbit densities from capture-recapture efforts, they did not account for varying capture probabilities (Krebs et al. 1987, Forys 1995, Forys and Humphrey 1997, Mills et al. 2005, Homyack et al. 2006. ...
... Densities estimated from capture-recapture methods likely provide more accurate population estimates than minimum number alive estimates commonly used to relate pellets to capture estimates (Homyack et al. 2006). When studies have used estimated rabbit densities from capture-recapture efforts, they did not account for varying capture probabilities (Krebs et al. 1987, Forys 1995, Forys and Humphrey 1997, Mills et al. 2005, Homyack et al. 2006. Closed-population models, incorporating time variation, behavioral response, and heterogeneity in the capture probabilities are more robust than models in which the capture probabilities are fixed (Chao and Huggins 2005). ...
Article
We conducted the most intensive estimate of the endangered Lower Keys marsh rabbit (Sylvilagus palustris hefneri) metapopulation to date using pellet surveys and capture–recapture methodology. We livetrapped 83 rabbits, evaluated 5 closed population models, and selected the model that best represented the data. We considered the variation in behavioral response model the best model and correlated (r2 = 0.913) its patch population estimates to patch pellet densities. From the prediction equation, we generated a range-wide metapopulation estimate of 317 rabbits, a western clade population of 257 rabbits, an eastern clade population of 25 rabbits, and translocated marsh rabbit populations of 35 and zero on Little Pine and Water keys, respectively. A subset of patches whose marsh rabbit subpopulations were last estimated in 1993 exhibited a 46% decline in abundance over 15 yr. Due to the low estimate of the eastern clade population, special effort should be initiated to avoid loss of genetic diversity. The prediction equation suffers from limited data at high pellet densities, patches with ≥5 pellets/m2. Future studies should investigate if the slope of the regression is indeed near 1 by sampling patches across the range of pellet densities, especially those with ≥5 pellets/m2. The equation provides managers a quick, efficient, and noninvasive method to estimate marsh rabbit abundance from pellet counts but the confidence of predicted rabbit densities from high pellet density patches is low. © 2011 The Wildlife Society
... Pellet counts are widely used for these questions relating to snowshoe hare abundances and habitat use because pellet counts have a relatively strong and repeatable relationship to mark- recapture population estimates at different times, places, and hare densities ( Krebs et al., 1987Krebs et al., , 2001Murray et al., 2002;Mills et al., 2005;Homyack et al., 2006;McCann et al., 2008). Because different plot sizes and shapes produce different estimates of the mean and variance of pellet density (McKelvey et al., 2002;Murray et al., 2002), researchers using pellet counts to infer snowshoe hare abundance should use equations relating to the particular plot type Index methods can be valuable for monitoring forest-dwelling vertebrates over broad spatial or temporal scales. ...
... Kloor, 1999), our results suggest that researchers should explicitly address the power of their sampling design for estimating pellet densities correctly. Equations to relate pellet density estimates to hare density are developed in several other papers (Krebs et al., 1987(Krebs et al., , 2001Murray et al., 2002;Mills et al., 2005;Homyack et al., 2006;McCann et al., 2008); our work adds to this literature by highlighting ways to improve pellet surveys themselves to ensure the per stand pellet values used to link to hare density are as accurate as possible. ...
... Second, we sampled a wide range of pellet densities ($0.35-45 pellets/1 m 2 circle). Our highest sites had higher densities of pellets than have been recently observed in British Columbia ( Sullivan et al., 2006), Idaho (Murray et al., 2002;McKelvey et al., 2002), elsewhere in Montana (Malloy, 2000;McKelvey et al., 2002;Ausband and Baty, 2005), Minnesota ( McCann et al., 2008), Quebec (de Bellefeuille et al., 2001;Potvin et al., 2005), Labrador (Newbury and Simon, 2005) and Maine ( Homyack et al., 2006). In contrast, higher pellet densities have been observed in Alaska ( Prugh and Krebs, 2004) and the Yukon ( Krebs et al., 2001), so our results should be interpreted with caution in these far northern areas with higher hare and pellet densities. ...
Article
Index methods can be valuable for monitoring forest-dwelling vertebrates over broad spatial or temporal scales. Fecal pellet counts are often used as an index of density or habitat use of snowshoe hares, Lepus americanus, but previous surveys have used different plot types and sample sizes, leading to problems comparing results from different studies and questions about the inferential power of each study. In this paper, we use field data and simulations to examine how the precision, bias, and efficiency of four commonly used plot types vary with plot type, pellet density, and sample size. Although no one plot type was consistently superior, we recommend thin rectangles (5.08 cm × 305 cm (2 in. × 10 ft), 0.155 m2) or 1 m2 circles over 0.155 m2 circles or 10 cm × 10 m (1 m2) rectangles. We recommend that researchers explicitly address the power of their survey design to detect different pellet densities, because much larger sample sizes are needed at low pellet densities than at high pellet densities to obtain similar precision. Small sample sizes are also much more likely to be biased, which could lead to incorrect inferences about management of snowshoe hare populations. Both uncleared and cleared plots performed well and will have value in different research contexts.
... The variable SCU adjusts for a difference in visual obstruction of softwood stems; therefore, high values were inferred to indicate greater thermal or predator escape cover for hares [26]. Other studies from Maine indicated that standscale density of hares was highest in regenerating clearcuts [9,34] where understory stem densities were greatest, and densities of hares were an order of magnitude greater than other stand types [9]. Densities were intermediate in clearcut stands where regenerating understory was thinned [34] and were lowest in mature and recent partially harvested stands where understory stems were relatively sparse [9]. ...
... Other studies from Maine indicated that standscale density of hares was highest in regenerating clearcuts [9,34] where understory stem densities were greatest, and densities of hares were an order of magnitude greater than other stand types [9]. Densities were intermediate in clearcut stands where regenerating understory was thinned [34] and were lowest in mature and recent partially harvested stands where understory stems were relatively sparse [9]. Contrary to results from Maine, woody stem density was not a significant predictor of hare pellet counts in Wyoming, but horizontal cover was significant [31]; this suggests that functional needs of hares for thermal and escape cover may be met in different ways in different regions. ...
... The recommendations at both the microsite and stand scales are consistent, suggesting that habitat use by hares is strongly associated with conifer and deciduous saplings that are in the stage of stem exclusion and self-thinning with reduced overstory canopies. In the Acadian forest of eastern North America, these stand conditions typically occur 10-35 years following partial or complete overstory removal [17,34]. We recommend additional work to more specifically elucidate the precise threshold of canopy closure and SCUs for which managers should strive to maximize hare use after forest harvesting. ...
Article
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Snowshoe hare (Lepus americanus) is an important prey species for many Carnivora and has strong influences on community structure and function in northern forests. An understanding of within-stand (microsite) forest structural characteristics that promote high use by hares is important to provide forest management guidelines. We measured forest structural characteristics at the microsite-scale in north-central Maine and used an information-theoretic modeling approach to infer which characteristics were most strongly associated with use by hares during winter. We measured overwinter hare pellet density to model relationships among microsite-scale vegetation structure and hare use. Overwinter pellet density was positively associated with live stem cover (3 × coniferous saplings + deciduous saplings) and negatively associated with overstory canopy closure; the two variables explained 71% of the variation in microsite use by hares. The highest pellet densities were in grids with canopy closure <72% and stem cover units >22,000 stems/ha. Silvicultural practices that create dense areas of conifer and deciduous saplings should receive high within-stand use by hares in winter. These conditions can be achieved by promoting the release of advanced regeneration and reducing overstory cover to encourage establishment of shade-intolerant species; clearcutting is one such silvicultural prescription to achieve these conditions.
... al 1958). In Maine, both snowshoe hare (Lepus americanus) and white-tailed deer (Odocoileus virginianus) are reported tree herbivores, which can hinder regeneration (Homyack et al., 2006;Russell et al., 2001;Table A.1). Since the early 1980s, Maine has averaged 200,000 wintering deer (MDIFW, 2020). In the 2000s, snowshoe hare densities were estimated to be 0.56-3.04 ...
... In the 2000s, snowshoe hare densities were estimated to be 0.56-3.04 hares/ha based on pellet density studies (Homyack et al., 2006). Waller and Alverson (1997) reported a high probability of deer removing both arboreal and non-arboreal species from forest ecosystems. ...
Article
When extracting large volumes of biomass from our nation’s forests, it is imperative to consider the sustainability of these intensive harvesting practices on future forests and timber products, and wildlife habitat and populations. The goal of this study was to assess if plant density and ecological integrity are affected by strip-cut harvesting silvicultural practices, prescribed burning on slash left on site and slash residue left unburned, and mammalian browse. A summer 2019 inventory of plant species throughout Compartment 33 on the Penobscot Experimental Forest, a management unit that recently was harvested for the second time in the past 55years, which utilized whole-tree harvesting, stem-only harvesting, and stem-only harvesting with prescribed burning. We evaluated the effects of strip clearcutting (stem-only removal and whole-tree removal), burning, and mammalian browse one year after the stand was harvested and burned Harvests with slash removal and slash left on site had consistently higher diversity, but lower ecological integrity based on floristic quality assessments, when compared to areas without harvest. Slash removal in conjunction with burning reduced arboreal density, particularly that of softwood species, but did not negatively impact ecological integrity. Effect of mammalian browse varied heavily by treatment, and the plant communities present on site, but did not have an overall impact on stem density. Browse was found to be particularly important for diversity indices and floristic quality assessments within stem only harvest, and harvest with burning. This investigation provided insight into successional forest composition, density, and ecological integrity (diversity and floristic quality assessment) changes in arboreal and non-arboreal plant species in response to these disturbance effects.
... Canada lynx (Lynx canadensis) occur across the boreal forest of North America, where their primary prey is snowshoe hare (Lepus americanus). Since lynx are dependent upon snowshoe hares, they select forested habitat based on high hare abundance or where they are most easily depredated [16][17][18], whereas hares select young coniferous forests where both food and cover are adequate [19,20]. In the southern periphery of the lynx range, forest composition is more heterogeneous and hare densities are naturally lower, leading to reduced abundance and restricted distribution of lynx [21], which require densities between 1 to 1.5 hares per hectare to persist [22].Because habitat for both lynx and hare has become both reduced and fragmented due to anthropogenic activities in their southern ranges, the distribution and abundance of both species is now restricted [23,24]. ...
... As predicted by the literature-based habitat suitability model, lynx were most likely to occur in sapling-stage coniferous forest. These results are consistent with other literature on lynx habitat ecology [17,18] and also describes snowshoe hare habitat preferences [19,20]. Road density and annual snowfall were not important for describing lynx occurrence in Ontario. ...
Article
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Peripheral populations often experience more extreme environmental conditions than those in the centre of a species' range. Such extreme conditions include habitat loss, defined as a reduction in the amount of suitable habitat, as well as habitat fragmentation, which involves the breaking apart of habitat independent of habitat loss. The 'threshold hypothesis' predicts that organisms will be more affected by habitat fragmentation when the amount of habitat on the landscape is scarce (i.e., less than 30%) than when habitat is abundant, implying that habitat fragmentation may compound habitat loss through changes in patch size and configuration. Alternatively, the 'flexibility hypothesis' predicts that individuals may respond to increased habitat disturbance by altering their selection patterns and thereby reducing sensitivity to habitat loss and fragmentation. While the range of Canada lynx (Lynx canadensis) has contracted during recent decades, the relative importance of habitat loss and habitat fragmentation on this phenomenon is poorly understood. We used a habitat suitability model for lynx to identify suitable land cover in Ontario, and contrasted occupancy patterns across landscapes differing in cover, to test the 'threshold hypothesis' and 'flexibility hypothesis'. When suitable land cover was widely available, lynx avoided areas with less than 30% habitat and were unaffected by habitat fragmentation. However, on landscapes with minimal suitable land cover, lynx occurrence was not related to either habitat loss or habitat fragmentation, indicating support for the 'flexibility hypothesis'. We conclude that lynx are broadly affected by habitat loss, and not specifically by habitat fragmentation, although occurrence patterns are flexible and dependent on landscape condition. We suggest that lynx may alter their habitat selection patterns depending on local conditions, thereby reducing their sensitivity to anthropogenically-driven habitat alteration.
... With careful planning, snow tracking could also be used to monitor mammal communities (Thompson et al. 1989, Pellikka et al. 2005) instead of only one focal species. However, fecal pellet inventories are probably more appropriate for determining the real abundance of snowshoe hare (e.g., Krebs et al. 2001, Murray et al. 2002, Homyack et al. 2006), as long as fecal pellet degradation rates are correctly estimated. Both techniques might be affected by detection issues and care should be taken to control for this factor whenever it is possible. ...
Article
Au Québec, il devient de plus en plus apparent qu'en aménagement forestier, l'atteinte de la conservation de la biodiversité ne pourra pas être réalisée sans une diminution substantielle du volume ligneux prélevé en forêt publique. Afin de maintenir des niveaux d'approvisionnement stables, certains scientifiques ont proposé d'appliquer le concept de la Triade. Dans ce système, une partie du territoire est allouée à l'utilisation de plantations ligneuses afin de combler les pertes d'apprivoisement occasionnées dans les zones de conservation et d'aménagement écosystémique. Toutefois, les plantations sont généralement mal perçues par le public et elles ont des impacts négatifs sur la biodiversité. Pour ces raisons, on recommande généralement de les installer dans des endroits qui sont déjà dégradés. En Abitibi-Témiscamingue, la conversion de friches agricoles en sites voués à la ligniculture est attrayante, car elle permettrait d'accroître la production de matière ligneuse à proximité des usines de transformation tout en remettant des sites abandonnés en production. Toutefois, les sites en début de régénération représentent généralement un habitat propice pour plusieurs espèces de petit gibier et leurs prédateurs. La transformation rapide d'un milieu hétérogène dominé par une strate arbustive en un milieu homogène pourrait donc avoir un impact négatif sur la faune. Le but de notre étude était donc d'évaluer et de comparer le potentiel faunique de plantations et de friches agricoles afin de déterminer leur contribution respective au maintien de la faune gibier régionale. Pour ce faire, nous avons réalisé des inventaires fauniques dans des plantations (n = 19) et des friches (n = 22) de différents stades de croissance. Deux espèces étaient visées: le lièvre d'Amérique et la gélinotte huppée. Pour le lièvre, des inventaires de crottin ont été réalisés en 2004, 2005 et 2006 et des transects de pistage hivernal ont été réalisés à l'hiver 2004-2005. Les résultats des deux techniques utilisées concordent et indiquent que l'abondance du lièvre est principalement influencée par le couvert végétal disponible plutôt que par le type de milieu. Toutefois, les inventaires de végétation nous indiquent que le couvert latéral, un élément important de l'habitat du lièvre, diminue de façon importante dans le temps dans les plantations ce qui indique que celles-ci auront un effet négatif sur le lièvre à long terme. Dans le cas de la gélinotte huppée, des inventaires auditifs de mâles tambourineurs ont été réalisés au printemps 2005 et 2006. L'analyse des résultats de l'année 2005 n'a pas déterminé de différences dans l'utilisation des deux milieux par les mâles tambourineurs, mais nous avons probablement sous-estimé notre rayon d'audibilité lors de cet inventaire. Les inventaires auditifs ont été répétés au printemps 2006, toutefois, le site de tambourinage de chaque mâle entendu a été répertorié afin de déterminer si celui-ci était à l'intérieur du site d'étude. Des 22 friches inventoriées, 14 étaient utilisées par la gélinotte huppée alors que seulement 2 des 19 plantations étaient occupées. L'analyse des résultats en 2006 démontre que les plantations sont évitées par les gélinottes huppées et que la transformation des friches en plantations résineuses a des effets négatifs sur cette espèce. Puisque les deux espèces seront affectées négativement par la transformation des friches agricoles en plantation, une attention particulière devra être portée à leur installation et leur configuration dans la matrice agroforestière pour diminuer ces impacts. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Friches, Plantations, Lièvre d'Amérique, Gélinotte huppée.
... We processed all data using ARC/INFO GIS version 9.2. In 2002, we documented winter snowshoe hare densities in different habitats (cover type and stand development) within our study area by establishing 1.5-m 2 rectangular snowshoe hare fecal-pellet plots in 18 forested stands, following methods described by Homyack et al. (2006). We sampled 42 plots at 40-m intervals along 4 400-m parallel transects (Homyack et al. 2007) in 7 stands classified as conifer-dominated sapling (CCDSAP), 3 stands classified as deciduous-dominated sapling (DCSAP), 4 stands classified as conifer or mixed pole (POLE), 2 stands classified as mature deciduous (DM), and 2 stands classified as DM with a regenerating mixed deciduous forest understory (Table 1). ...
Article
In March 2000, Canada lynx (Lynx canadensis) were listed as a federally threatened species in 14 states at the southern periphery of their range, where lynx habitat is disjunct and snowshoe hare (Lepus americanus) densities are low. Forest conditions vary across lynx range; thus, region-specific data on the habitat requirements of lynx are needed. We studied lynx in northern Maine, USA, from 1999 to 2004 to assess quality and potential for forests in Maine to sustain lynx populations. We trapped and radiocollared 43 lynx (21 M, 22 F) during this period and evaluated diurnal habitat selection by 16 resident adult lynx (9 M, 7 F) monitored in 2002. We evaluated lynx selection of 8 habitats at multiple spatial scales, and related lynx habitat selection to snowshoe hare abundance. Lynx preferred conifer-dominated sapling stands, which supported the highest hare densities on our study site ( = 2.4 hares/ha), over all other habitats. The habitats where lynx placed their home ranges did not differ by sex. However, within their home ranges, males not only preferred conifer-dominated sapling stands, but also preferred mature conifer, whereas females singularly preferred conifer-dominated sapling stands. Approximately one-third of Maine's spruce-fir forest and nearly 50% of our study area was regenerating conifer or mixed-sapling forest, resulting from a disease event and intensive forest management (e.g., large clear-cuts). Our findings suggest that current habitat conditions in Maine are better than western montane regions and approach conditions in boreal forests during periods of hare abundance. We recommend that forest landowners maintain a mosaic of different-aged conifer stands to ensure a component of regenerating conifer-dominated forest on the landscape.
... There is only one study measuring defecation rates of rabbits from the Iberian Peninsula (Gonzalez-Redondo 2009). Future research should investigate further in these areas and also in quantifying the relationship between the census method and the current density of the species (Homyack et al. 2006). In central southern Spain, clearance pellet counts corrected for pellet persistence , estimated as described in our paper, was the index best related to rabbit density estimates in summer (Fernandez-de-Simon et al., in press). ...
Article
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The European rabbit Oryctolagus cuniculus is a key species in Mediterranean ecosystems of the Iberian Peninsula, and reliable methods for monitoring its abundance are urgently required. Although clearance plot pellet counts may be useful in monitoring rabbit populations, such counts are potentially affected by variation in the persistence of rabbit pellets. The aim of our study was to assess persistence of rabbit pellets in the Iberian Peninsula for reliable estimates of rabbit abundance from clearance plot counts.Wecarried out the experiment from July 2006 to November 2007 at seven localities in central southern Spain. Marked fresh pellets were monthly placed at experimental plots, and their persistence was monitored monthly. Persistence was estimated from the proportion of marked pellets remaining between consecutive counts. Independent variables in analysis included slope steepness, vegetation, rabbit and ungulate activity, meteorology and temporal variables. Persistence significantly varied among localities and seasons and with their interaction. The final model showed that pellet persistence was best explained by total rainfall between counts, and also included the time between visits and slope steepness and the interactions rainfall*time between visits and rainfall*slope. Our results suggest that estimating pellet persistence for each locality and season is necessary to make estimates obtained from different localities and months comparable. In the Mediterranean region, early summer at the start of the dry season would be the recommended time for yearly rabbit monitoring based on any pellet-count index, since reduced rainfall favours pellet persistence. Sampling protocols must standardise the number of days between counts, and plots must be established in areas with gentle slope to maximise pellet persistence between counts.
... The density of animals in each area was calculated from pellet count transects using equation (1), where D a is the density of the animal, D s is the total number of pellet groups counted per area, P i is the mean time to degradation of the pellets, I is the defecation rate (Homyack et al., 2006;Periago & Leynaud, 2009): ...
Article
Many species of large herbivores are declining in numbers as a consequence of direct exploitation or habitat loss. In the Ethiopian highlands, rapid human population growth has resulted in an expansion of human settlements and farmland, threatening many endemic species such as the mountain nyala Tragelaphus buxtoni. Despite being listed as an endangered species, the mountain nyala is still the most important trophy hunting species in Ethiopia. We counted faecal pellets of mountain nyala within plots distributed along transects to estimate population size and identify key environmental variables associated with the presence of faecal pellet groups. The total mountain nyala population was estimated at 3756 (95% confidence intervals: 2506–7135) individuals, mainly occupying woodlands while avoiding human developments (agriculture and settlements). The total suitable area was estimated at 8333 km2. Only 31.6% of the total population lived within a national park, while 53.5% of the population inhabited two controlled hunting areas in the eastern mountains. Abundance was 3.7 times higher in areas patrolled by wardens, regardless of being in a national park or hunting area, suggesting that formal protection must be followed by surveillance to avoid poaching and habitat destruction. We found no negative correlation between pellet abundance and trophy hunting. Yet, it is too early to conclude that trophy hunting is sustainable as it has only recently been initiated in the studied populations.
... Southern lynx and hare populations do not reach the high densities observed during cyclic peaks in the boreal forest (Keith 1990, Hodges 2000, Murray 2000, and, until recently, southern populations of either species had not received research attention commensurate with that afforded to their northern counterparts. The recent listing of lynx as Threatened under the Endangered Species Act (U.S. Fish and Wildlife Service 2000) prompted a spate of research activity on the ecology of southern lynx (e.g., Schwartz et al. 2002;Hoving et al. 2004Hoving et al. , 2005Steury and Murray 2004;Squires and Ruggiero 2007) and southern hares (e.g., Murray et al. 2002Murray et al. , 2005Mills et al. 2005;Homyack et al. 2006), but considerable uncertainty and disagreement remain regarding their ecology and conservation at lower latitudes. We address key topics related to southern lynx and snowshoe hare ecology that either have not been tested adequately or received conflicting (and in some cases misleading) support in the literature. ...
Article
Abstract The ecology of Canada lynx (Lynx canadensis) and their main prey, snowshoe hares (Lepus americanus), is poorly understood in southern Canada and the contiguous United States compared to the boreal forest of Canada and Alaska, USA, where both species are well studied. However, given recent listing of lynx under the Endangered Species Act, accurate understanding of lynx and snowshoe hare ecology and conservation requirements in the United States is a high priority. We critically examined unchallenged perceptions and important research needs related to lynx and hare ecology and conservation at the southern extent of their range. Contrary to popular dogma, lynx do not require old-growth forest for denning, but further research on lynx and hare use of fragmented landscapes at lower latitudes is required. The contention that southern lynx are subject to higher interference or exploitative competition compared to their northern counterparts remains without strong empirical support. Lynx rely more on red squirrels (Tamiasciurus hudsonicus) and possibly other alternate prey at lower latitudes, but hares are the predominant food type for lynx across their range. Southern lynx and hare populations do not exhibit periodic cyclicity, but harvest statistics suggest that lynx abundance in the southern range is highly variable, implying that numerical fluctuations likely are fueled by immigration from Canada. Southern lynx population viability in the absence of ingress is suspect and thus maintaining connectivity with northern areas of occupancy should be a priority. Successful conservation of lynx populations in the contiguous United States will require 1) improved understanding of lynx population and habitat ecology at lower latitudes, 2) protection and management of large tracts of lynx and snowshoe hare habitat, and 3) ensured connectivity between lynx populations at the core and periphery of the species' range. However, in light of the numerous challenges facing conservation of populations of many species at their southern distributional limit, the long-term prognosis for lynx in the southern range currently is uncertain.
... A landscape-scale approach that considers multiple spatial scales, from distances traveled during daily activities up to areas used during seasonal and annual activities, could be used to identify areas with hare abundance adequate to support a lynx population. Estimating relative abundance of hares across broad spatial scales is possible because hare pellet counts are correlated with hare abundance (Krebs et al. 1987;Homyack et al. 2006;McCann et al. 2008). Areas used frequently by lynx have more habitat containing high hare pellet counts than areas where lynx are detected infrequently (Koehler 1990;Murray et al. 1994;Vashon et al. 2008). ...
Article
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We used location data from radio-collared Canada lynx (Lynx canadensis Kerr, 1792), pellet-count data from snowshoe hares (Lepus americanus Erxleben, 1777), and cover-type data from satellite imagery to evaluate the relationship between the scale of habitat measurement and the potential for persistence of lynx in northeastern Minnesota, USA, at the southern extent of their range. We counted hare pellets at transects throughout northeastern Minnesota to index hare abundance in cover types. Pellet counts were highest in coniferous forest, regenerating–young forest, and shrubby grassland, and these cover types were greater inside lynx use areas than outside of them. Proportions of regenerating–young forest were greater at scales ≥5 km2. We used these results and satellite imagery to map potential lynx core areas. We predicted that 7%–20% of the study area was suitable for lynx. Areas that we predicted to be suitable for lynx corresponded with known core areas, including those withheld from analyses. To maintain habitat for lynx persistence, forest management should retain current levels of 10- to 30-year-old coniferous forest and include ≥5 km2 areas containing 40% of 10- to 30-year-old coniferous forest. Mapping of potential core areas would be improved if cover-type data from satellite imagery identified conifer regeneration.
... A partir del análisis de sus heces, se han estudiado diversos aspectos de la ecología de S. floridanus: su distribución (Dorantes-Villalobos, 2017; Trent y Rongstad, 1974), factores que afectan su abundancia (Glebskiy, 2016;Glebskiy et al., 2018;Wainright, 1969) y su dieta (Dalke y Sime, 1941;Glebskiy, 2019). Este tipo de estudios sobre las heces se han realizado para conocer, por ejemplo, el tamaño poblacional de la liebre americana, Lepus americanus Erxleben (Homyack et al., 2006), la distribución del mapache Procyon lotor (Linnaeus) (Hoffmann y Gottschang, 1977) y la distribución, abundancia y dieta del coyote Canis latrans Say (Kays et al., 2008), con muy buena precisión. ...
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Reproduction requires large amounts of energy, so many organisms look for the ideal season to carry out this process. For example, each population of the Eastern Cottontail, Sylvilagus floridanus, is expected to adjust its life cycle to reproduce in the most suitable season of the year, which may vary depending on the particular conditions of the site where each one lives. The objective of this study was to determine at what time of the year this rabbit reproduces in the xerophilous scrub of the Pedregal of San Ángel, México City, based on an analysis of seasonal variation of the abundance and size of its feces. Monthly systematic sampling of abundance of feces was made at established sites for 4 years and, during the first year, the size of excreta was also recorded. Data was analyzed using a χ2 test. It was recorded that small fecal pellets are concentrated in September and that the highest abundance values were recorded between October and December. The data suggest that the reproductive period occurs in August, which is a month of greater food availability. The data obtained do not coincide with the reproductive season recorded by this species in other locations.
... Hare dropping densities should rather be estimated in plots (e.g. Murray et al. 2005, Homyack et al. 2006 as pellet groups cannot be easily distinguished from each other and counting single pellets while walking a transect is too time-consuming. While it was possible to detect nearly Table 2. Mean detectability as (density on transects) (density in plots) -1 with 95% confidence intervals of red deer, roe deer and wild boar droppings (n = 190 transect sectors) in winter after snowmelt (March/April) and summer (May-October) in different forest types of the Białowieża Forest, from 1997 to 1999 (a confidence interval that does not include the value 1 indicates a reduced detectability). ...
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We counted droppings of ungulates and hare on transects in order to assess (1) seasonal changes in detectability and disappearance of pellet groups, (2) whether the detectability varies according to the forest type, and (3) the degree of misidentification between pellets of roe deer (Capreolus capreolus) and red deer (Cervus elaphus). The summer decrease in detectability of pellet groups was the most important factor for all species but European bison (Bison bonasus). Detectability did not significantly depend on forest type. In summer, decay reduced significantly the dropping density of red deer, roe deer, wild boar (Sus scrofa) and European hare (Lepus europaeus) but not those of bison and moose (Alces alces). Misidentification of roe and red deer droppings did not influence much density estimates of red deer but resulted in an important overestimation of roe deer in areas were roe deer were much less common than red deer.
... We used faecal pellet counts as a measure of relative abundance of snowshoe hares because of the strong link between pellet density and hare density across the species range ( Krebs et al. 2001b;Mills et al. 2005;Homyack et al. 2006). Grids of pellet plots were installed at each site in the chronosequence (n = 84). ...
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Understory regeneration within canopy gaps in old-growth boreal forests may provide suitable habitat for wildlife typically associated with early-seral stages, leading to an increase in their abundance in late succession. We surveyed a chronosequence of postfire (17–265 years) and postharvest (3–63 years) stands in Canada’s eastern boreal forest to deter- mine whether snowshoe hares (Lepus americanus Erxleben, 1777) followed a bimodal abundance distribution with stand age that reflects changes in food and cover during postdisturbance succession. A strong peak in relative hare abundance oc- curred during the first 80 years of succession, with highest faecal pellet densities observed between 40 and 50 years after disturbance. Changes in hare abundance during this period were similar among fire- and clearcut-origin stands and closely tracked changes in lateral cover and vertical cover. Pellet density increased again in stands >180 years. Variation in hare abundance during late succession was partially mediated by gap dynamics, with highest pellet densities in stands occupied by an intermediate proportion of mortality-origin canopy gaps. Hares thus undergo rapid changes in abundance during early succession followed by a much longer period of subtle changes in density as stands develop old-growth structure. Shifting forest age-class distribution induced by forest management could therefore significantly alter regional spatiotemporal dynamics of snowshoe hares.
... Pellet counts have been found to be strongly correlated with snowshoe hare abundance across their range (e.g., Mills et al., 2005;Homyack et al., 2006), and in our study area in particular ( Murray et al., 2002). We calculated the total number of pellets counted at all plot locations within a stand per year as the response variable in subsequent analyses. ...
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a b s t r a c t Maintaining forest biodiversity requires an understanding of how forest-dependent species respond to a variety of forestry activities. This is particularly true for mammals, which often act as keystone species or focal species for conservation efforts in forest ecosystems. Snowshoe hares (Lepus americanus) serve as an important herbivore and prey resource throughout their range in the boreal forest. We examined the response of hares to partial and clearcut harvest, site preparation activities (post-harvest burning or chemical/mechanical preparation for regrowth), and precommercial thinning, using pellet plots on 359 forest stands across an expansive landscape in northern Idaho over a 5-year period. Hares initially responded negatively to harvest, with clearcut harvest having a greater negative impact than partial har-vest, and this response was exacerbated by site preparation activities. Mid-successional stands (15– 40 years old) that had been clear cut with site preparation treatments applied or partially harvested with no site preparations applied had greater snowshoe hare pellet counts than mature or recently harvested stands. Pre-commercial thinning had no detectable effect on hares in this landscape. Our findings suggest an interaction between site preparation and type of harvest (clear-cut vs. partial), which suggests that both the initial negative impacts and subsequent positive response to site preparation as stands age are attenuated somewhat in partially harvested vs. clear-cut stands. Our results likely relate to the influ-ence of management activities on vegetative cover, which is strongly related to hare abundance in a vari-ety of systems. They suggest that silvicultural activities such as site preparation could be damaging to hare populations when applied widely across landscapes, particularly when young age classes predom-inate. However, because the effects of harvest and site preparation are largely transitory, use of these techniques may not substantially depress hare populations if enough stands can be maintained in the 15–40 year age class. Ó 2012 Elsevier B.V. All rights reserved.
... We determined population density along each transect based on the average number of pellets collected on each plot type (rectangular and circular). Use of pellet counts for estimating hare density has been validated for our study area (Murray et al. 2002) as well as more broadly across the hare distribution (Krebs et al. 1987, 2001, Mills et al. 2005, Homyack et al. 2006). Given that we included 2 plot shapes in our design, we estimated hare densities from pellet numbers in rectangular plots using the relationship established for the Yukon (Krebs et al. 2001), whereas those from circular plots were derived from the exponential equation for northern Idaho (Murray et al. 2002). ...
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Th e infl uence of habitat quality and population density on occupancy dynamics may surpass that of traditional metrics of area and isolation, but often this is not considered explicitly in studies of spatially structured populations. In landscapes that are not easily characterized as binary habitat/non-habitat (e.g. variegated landscapes), this infl uence may be even more important and occur at both local and landscape levels. It follows that occupancy dynamics may be driven by dispa-rate processes depending on how extinction or colonization relate to habitat quality and population density. We examined the relative infl uence of area, structural isolation, habitat quality, local population density, and neighborhood popula-tion density (i.e. population density in the landscape around a site) on the probability of extinction and colonization of snowshoe hare Lepus americanus across an expansive forest mosaic landscape (encompassing the northern third of Idaho). Habitat quality and population density were highly infl uential in determining extinction and colonization, whereas patch area and isolation were much less important. Sites with heavier vegetative cover at the site or landscape-level were more likely to be colonized and less likely to go extinct, and sites with greater local population density in the previous time step had lower probability of extinction. Sites embedded in high density neighborhoods also were less likely to go extinct, but not more likely to be colonized. We found a signifi cant interaction between local and neighborhood population density on extinction in 1 yr, suggesting that the strength of demographic rescue may vary dependent on local site densities. Our results add to a growing literature showing that factors outside of structural metrics of area and isolation are important drivers of occupancy dynamics. Given the multi-scaled infl uence of habitat quality and population density on occupancy dynamics, our work also indicates that research on snowshoe hare must extend beyond simply assessing local factors to understand the spatial dynamics of populations. Occupancy dynamics in spatially structured populations largely have been understood by reference to the area-isolation paradigm, which states that extinction and colon-ization processes are controlled primarily by patch area and isolation, respectively (MacArthur and Wilson 1967, Hanski 1999). Th e area-isolation paradigm has guided research in fragmented or patchy environments, and heavily informs landscape ecology, metapopulation models, and applied conservation eff orts (e.g. reserve design). However, for species inhabiting landscapes that are not easily con-ceptualized as binary habitat/non-habitat (e.g. variegated landscapes), or for generalist species that may be able to use, or move through, many habitat types of diff ering quality, area and isolation may be less important drivers of occu-pancy, or even diffi cult to measure when discrete patches cannot be easily defi ned (Manning and Lindenmayer 2004, Prugh et al. 2008, Price et al. 2009). Moreover, recent work reveals that even in heavily fragmented landscapes where patches are more easily defi ned, area and isolation are not always strong predictors of occupancy patterns and other factors may mediate or surpass their infl uence
... Therefore, equations we developed provided an important reference point for future pellet count surveys to estimate hare density in the southern GYE. Significant relationships between snowshoe hare density and pellet counts in western Wyoming were consistent with other studies throughout North America (e.g., Murray et al. 2002Murray et al. , 2005Mills et al. 2005;Homyack et al. 2006). Similar to other geographic areas where they were implemented, pellet counts from 1-m 2 circular plots were highly correlated to hare density estimates obtained from associated markrecapture studies (Murray et al. 2002, McCann et al. 2008. ...
Article
ABSTRACT Snowshoe hares (Lepus americanus) are an important prey species for Canada lynx (Lynx canadensis) and are considered critical for lynx population persistence. Determination of snowshoe hare distribution and abundance is needed by land management agencies for lynx conservation. An accepted approach for estimating snowshoe hare abundance is the use of fecal-pellet plot counts. Locally derived regression equations are preferred for accurate calibration of pellet counts to snowshoe hare density due to local differences in pellet deposition and decomposition. We used linear regression to examine correlations between snowshoe hare density, as determined by mark–recapture estimates, and pellet plot counts on both uncleared plots and annually cleared plots on the Bridger-Teton National Forest, western Wyoming, USA. We found significant correlations between snowshoe hare density estimates and fecal pellet counts for both uncleared and annually cleared pellet counts; however, the relationship was stronger (higher r) when using pellet counts from annually cleared plots. In addition, we found that adjusting the buffer size by omitting hard habitat edges (not used by hares) around trapping grids improved correlations between snowshoe hare density and fecal pellet counts for both uncleared plots and annually cleared plots. Though precision is sacrificed when using uncleared plots, they may be useful as a coarse index of habitat use by snowshoe hares. Our derived regression equations may be useful to identify important foraging habitat for Canada lynx in western Wyoming. Land managers responsible for conserving snowshoe hare habitat in western Wyoming may use these equations to monitor changes in hare populations among habitats and during prescribed management actions.
... In areas where direct observation of animals is difficult, due to either low local abundance of the species, secretive behavior, low visibility, or human disturbance, the use of indirect methods such as the quantification of tracks and feces (pellet groups) can be more appropriate [2,3]. Pellet-group counting methods have been assessed to accurately evaluate the population density of both old and new world ungulates, lagomorphs, and elephants [e.g.,456789. In the field, pellet groups have been quantified in sampling units (e.g., circular plots, strip transects, ST) and for estimating decay rate (FSC, Fecal Standing Crop), or in re-sampling the same plots two or more times (FAR, Fecal Accumulation Rate) [10]. ...
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Wildlife species population density estimation is important from both ecological and management perspectives. The pellet-group counting method has been used to evaluate density of the white-tailed deer (Odocoileus virginianus). This species is an important component of human diet in tropical habitats. The objectives of this study were to: 1) compare density estimates using four methods: counts in circular plots (FSC, Fecal Standing Crop and FAR, Fecal Accumulation Rate), and counts in transects (LT, Line Transect and ST, Strip Transect); 2) simulate the effect of increased sampling effort on density and precision, and; 3) evaluate the effort required to detect changes in population density using LT. From 2006 to 2007, we intensively sampled a 1 km 2 quadrant in a Mexican tropical dry forest. The results indicate that all four methods produce similar mean population density estimates. However, estimates of precision were dependent on sample size which in turn was associated with the particular counting method used. In descending order of estimate precision, the methods ranked as: LT, ST, FSC, and FAR. To detect population changes of < 20%, we suggest the establishment of 5 to 22 transects (LT) of 390 m during the dry season. To reduce bias in density estimation, it is important to obtain defecation and pellet decomposition rates in the study site.
... Future research should investigate further in these areas and also in quantifying the relationship between the census method and the current density of the species (Homyack et al. 2006). In central southern Spain, cleared-plot pellet counts corrected for pellet persistence, estimated as described in our paper, was the index best related to rabbit density estimates in summer (Fernandez-de-Simon et al. 2011a). ...
... With careful planning, snow tracking could also be used to monitor mammal communities (Thompson et al. 1989, Pellikka et al. 2005 instead of only one focal species. However, fecal pellet inventories are probably more appropriate for determining the real abundance of snowshoe hare (e.g., Krebs et al. 2001, Murray et al. 2002, Homyack et al. 2006, as long as fecal pellet degradation rates are correctly estimated. Both techniques might be affected by detection issues and care should be taken to control for this factor whenever it is possible. ...
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Au Québec, il devient de plus en plus apparent qu'en aménagement forestier, l'atteinte de la conservation de la biodiversité ne pourra pas être réalisée sans une diminution substantielle du volume ligneux prélevé en forêt publique. Afin de maintenir des niveaux d'approvisionnement stables, certains scientifiques ont proposé d'appliquer le concept de la Triade. Dans ce système, une partie du territoire est allouée à l'utilisation de plantations ligneuses afin de combler les pertes d'apprivoisement occasionnées dans les zones de conservation et d'aménagement écosystémique. Toutefois, les plantations sont généralement mal perçues par le public et elles ont des impacts négatifs sur la biodiversité. Pour ces raisons, on recommande généralement de les installer dans des endroits qui sont déjà dégradés. En Abitibi-Témiscamingue, la conversion de friches agricoles en sites voués à la ligniculture est attrayante, car elle permettrait d'accroître la production de matière ligneuse à proximité des usines de transformation tout en remettant des sites abandonnés en production. Toutefois, les sites en début de régénération représentent généralement un habitat propice pour plusieurs espèces de petit gibier et leurs prédateurs. La transformation rapide d'un milieu hétérogène dominé par une strate arbustive en un milieu homogène pourrait donc avoir un impact négatif sur la faune. Le but de notre étude était donc d'évaluer et de comparer le potentiel faunique de plantations et de friches agricoles afin de déterminer leur contribution respective au maintien de la faune gibier régionale. Pour ce faire, nous avons réalisé des inventaires fauniques dans des plantations (n = 19) et des friches (n = 22) de différents stades de croissance. Deux espèces étaient visées: le lièvre d'Amérique et la gélinotte huppée. Pour le lièvre, des inventaires de crottin ont été réalisés en 2004, 2005 et 2006 et des transects de pistage hivernal ont été réalisés à l'hiver 2004-2005. Les résultats des deux techniques utilisées concordent et indiquent que l'abondance du lièvre est principalement influencée par le couvert végétal disponible plutôt que par le type de milieu. Toutefois, les inventaires de végétation nous indiquent que le couvert latéral, un élément important de l'habitat du lièvre, diminue de façon importante dans le temps dans les plantations ce qui indique que celles-ci auront un effet négatif sur le lièvre à long terme. Dans le cas de la gélinotte huppée, des inventaires auditifs de mâles tambourineurs ont été réalisés au printemps 2005 et 2006. L'analyse des résultats de l'année 2005 n'a pas déterminé de différences dans l'utilisation des deux milieux par les mâles tambourineurs, mais nous avons probablement sous-estimé notre rayon d'audibilité lors de cet inventaire. Les inventaires auditifs ont été répétés au printemps 2006, toutefois, le site de tambourinage de chaque mâle entendu a été répertorié afin de déterminer si celui-ci était à l'intérieur du site d'étude. Des 22 friches inventoriées, 14 étaient utilisées par la gélinotte huppée alors que seulement 2 des 19 plantations étaient occupées. L'analyse des résultats en 2006 démontre que les plantations sont évitées par les gélinottes huppées et que la transformation des friches en plantations résineuses a des effets négatifs sur cette espèce. Puisque les deux espèces seront affectées négativement par la transformation des friches agricoles en plantation, une attention particulière devra être portée à leur installation et leur configuration dans la matrice agroforestière pour diminuer ces impacts.
... Harrison, University of Maine, unpublished data) estimated from pellet counts using the regression of Homyack et al. (2006). Lynx used in this study were equipped with only VHF collars during HIGH and with only GPS collars during LOW. ...
Article
Previous studies of Canada lynx (Lynx canadensis) within the northern boreal forest region have documented that lynx respond spatially to a decline in snowshoe hare (Lepus americanus) density, as exhibited by expansion of territories and changes in social structure. I compared home range area and spatial overlap in the southeastern portion of their geographic range during periods of relatively high and relatively low hare density. Home range areas of lynx did not change between periods of high and low hare density, except that home ranges of females during the denning season expanded during the low period. The presence of kittens constrained home range areas of reproductive females during denning because females were attending kittens. Intra- and intersexual overlap did not change as hare density declined, with the exception of a decrease in overlap between females. This decrease was likely caused by decreased reproduction during the low period, which reduced potential for territorial overlap among mothers and daughters. Hare density during the nadir of cycles in more northerly populations can reach levels nearly a magnitude lower than reported for Maine during my study. This may have prevented breakdowns in territories and changes in social structure by lynx, which may have shifted life history strategies towards territorial maintenance and reduced reproduction as hare densities declined. I also investigated changes in use of high-quality hare habitat (HQHH) at the landscape scale, and habitat selection of HQHH within home ranges of lynx between periods of high and low hare density. Lynx did not change their extent of use of HQHH at the landscape scale, suggesting lynx had adequate amounts of HQHH within their home ranges to encounter hares during both the high and low periods of hare density. Lynx exhibited stand-scale selection for HQHH during both hare density periods, but the intensity of female selection for HQHH declined as hare density declined. This suggests that lynx continued to remain focused on foraging for hares during both periods, but that females may become more generalized in habitat and prey selection during the period of lower hare density. Lynx monitored during this study wore GPS collars during a period of low hare density and VHF collars during a period of high hare density. This presented methodological challenges when I compared lynx responses between hare density periods. Errors associated with VHF collars were known for this study, but errors associated with GPS collars were not. Failed fix attempts and location inaccuracy caused by environmental and satellite configurations can bias habitat selection and spatial analyses. I evaluated fix success and location error of GPS collars in 7 habitat classes during 2 seasons in northern Maine. I also used an information-theoretic modeling approach to investigate covariates influencing fix success and location error. Canopy cover had the greatest influence on fix success and the configuration of available satellites had the greatest influence on location error. Results were used to compensate for habitat bias and location error caused by GPS collars worn by lynx during a period of low hare density.
... Aún cuando la técnica presenta algunas dificultades, como la pérdida de muestras, debida al lavado por lluvias ( Barnes & Dunn, 2002) y al ataque por insectos coprófagos, el método presenta una ventaja considerable al tratarse de evidencias inertes, que pueden ser muestreadas, sistemáticamente, en el campo (Neff, 1968;Putman, 1984), ofreciendo un método robusto para el establecimiento del número de individuos en poblaciones con densidades bajas (Murray et al. 2002). El conteo de materia fecal, el tamaño de grupos de excrementos, la tasa de defecación y el uso de letrinas han sido utilizados para estimar parámetros poblacionales relacionados, incluso, con el uso del hábitat de diversas especies (Vernes, 1999;De Boer et al. 2000;Theuerkauf & Ellenberg, 2000;Krebs et al. 2001;Lombardi et al. 2003;Homyack et al. 2006). ...
... Aún cuando la técnica presenta algunas dificultades, como la pérdida de muestras, debida al lavado por lluvias (Barnes & Dunn, 2002) y al ataque por insectos coprófagos, el método presenta una ventaja considerable al tratarse de evidencias inertes, que pueden ser muestreadas, sistemáticamente, en el campo (Neff, 1968; Putman, 1984), ofreciendo un método robusto para el establecimiento del número de individuos en poblaciones con densidades bajas (Murray et al. 2002). El conteo de materia fecal, el tamaño de grupos de excrementos, la tasa de defecación y el uso de letrinas han sido utilizados para estimar parámetros poblacionales relacionados, incluso, con el uso del hábitat de diversas especies (Vernes, 1999; De Boer et al. 2000; Theuerkauf & Ellenberg, 2000; Krebs et al. 2001; Lombardi et al. 2003; Homyack et al. 2006). Algunos vertebrados se caracterizan por defecar en letrinas, visitadas repetitivamente por individuos de la misma especie. ...
Article
The systematic fecal pellet-group count has been used to estimate population parameters of various species. The Pacarana (Dinomys branickii) is characterized by defecating in latrines which are used repeatedly by a family group, so that sampling of the fecal pellets is an alternative, since the species lives in small populations with discontinuous distribution. However, the technique requires knowledge of the defecation rate and fecal morphology unknown for this species. The main objective of this study was to monitor the latrines in three populations of D. branickii with different numbers of individuals between males and females kept in a seminatural environment, in order to generate information on the morphology and the daily production of feces. For each group of animals the total number of droppings deposited at each latrine was collected, counted and measured. The total number of droppings/animal/day was obtained using fecal markers. The mean droppings per latrine varied according to group size. Individual defecation rates showed statistically significant differences between sexes. The cylindrical shape of the droppings of D. branickii shows a clear difference between the average length and width. The dimensions of the droppings varied more frequently in the latrines than in the individual samples. The estimation of the population size of D. branickii based on the use of latrines is promising, but needs to be validated in its natural habitat.
... Due to these limitations, index methods are often used for broad surveys. Pellet counts for lagomorphs are widely used for these questions relating abundances and habitat use because pellet counts have a relatively strong and repeatable relationship to mark-recapture population estimates at different times, places, and densities (Krebs et al., 1987(Krebs et al., , 2001Homyack et al., 2006;Berg and Gese, 2010). Swamp rabbit latrines on elevated substrates are visually obvious; therefore, swamp rabbit surveys are simple, inexpensive and frequently used to monitor distribution, occupancy, and index relative abundance. ...
Article
Reforestation of bottomland hardwood (BLH) forests has occurred within the Lower Mississippi Alluvial Valley (LMAV), USA, to support a wide range of ecosystem services, but especially wildlife habitat enhancement. As ecosystem restoration efforts proceed in BLH ecosystems, managers and policymakers are seeking criteria to evaluate wildlife habitat enhancement goals. Specialist wildlife that evolved within forest ecosystems can be sensitive to the composition, structure, and function of an ecosystem in relation to the system's natural or historical range of variation and thereby serve as indicators of habitat quality. The swamp rabbit (Sylvilagus aquaticus) is a specialist species of BLH forests throughout the LMAV and therefore may be an appropriate indicator species for this ecosystem. To address this, we reviewed peer-reviewed literature to evaluate the utility of swamp rabbits as an indicator species according to three commonly-used criteria: habitat factors defining swamp rabbit relationships to BLH forests, the importance of swamp rabbit habitat to other wildlife, and the efficiency of swamp rabbit monitoring. We conclude that the swamp rabbit is a suitable indicator of wildlife habitat quality in BLH ecosystems in the LMAV because they evolved and remain endemic to the ecosystem, use habitat that integrates desirable characteristics that positively influence wildlife biodiversity, and are easy to monitor routinely.
... On RNR, less homogenous habitats, especially extensive brushy habitats, prevented us from using linetransect sampling effectively. Therefore, we used pellet-count indices to estimate relative abundance of hares and springhares (Homyack et al. 2006). In September 2007, we randomly established 25 transects, each separated by .500 ...
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ABSTRACT To investigate the role of black-backed jackals (Canis mesomelas) as predators, we studied diet, prey selection, and predation impact of jackals on 2 game ranches in South Africa that differed in ungulate diversity and biomass. Results showed that large (>15 kg) ungulate species dominated jackal diets throughout the year on both the less diverse (range of ingested biomass across seasons = 39–78%) and more diverse (26–69%) game ranch. Other important food items included medium-sized mammals (1–3 kg; 1–26%) and fruit (2–69%), whereas small mammals comprised 3–11% of ingested biomass across seasons on both sites. Jackals were not random in consumption of ungulates, and consumption patterns suggested jackals actively hunted certain species rather than consumed them as carrion. During ungulate birthing periods, jackals consumed almost exclusively those ungulate species that were hiders (i.e., fawns were hidden in tall vegetation away from herd) regardless of ungulate densities, suggesting that primarily fawns were preyed upon. Among hiders, there was a negative relationship (P = 0.01) between body size and percent of population consumed by jackals, indicating smaller species were more susceptible than larger species to jackal predation. Consequently, springbok (Antidorcas marsupialis) were always selected over other ungulate species on both sites, and this species was the most impacted by jackal predation. In contrast, ungulate species that were followers (i.e., fawns immediately followed mothers within protection of the herd) were scarcely or not at all consumed by jackals, regardless of body size or density. Medium-sized mammals were selectively consumed over ungulates, and there was a negative relationship (P < 0.01) between consumption of berries and ungulates, indicating alternative food resources influenced consumption of ungulates on our study sites. Our results will help wildlife managers in Africa identify ungulate species susceptible to jackal predation, and can be used to develop management strategies for reducing jackal predation in areas where it is problematic.
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Snowshoe hares (Lepus americanus) are a critically important prey species for Canada lynx (Lynx canadensis). Determination of snowshoe hare distribution and abundance is needed in western Wyoming for lynx conservation. We used linear regression to examine the correlations between snowshoe hare density, as determined by mark-recapture estimates, and fecal pellet plot counts on both uncleared and annually cleared plots on the Bridger-Teton National Forest, western Wyoming. We found significant correlations between hare density estimates and fecal pellet counts for both uncleared and annually cleared pellet counts; however the relationship was much stronger for annually cleared pellet counts. Adjusting the buffer size by omitting hard habitat edges (not used by hares) around the trapping grids improved correlations between hare density and fecal pellet counts further. We recommend pellet counts from annually cleared plots be used when precise estimates of snowshoe hare abundance are required. Though precision is sacrificed when using uncleared plots, they are useful as a coarse index of habitat use by hares. The derived regression equations should be used to identify foraging habitat for lynx in western Wyoming. In addition to snowshoe hares, in western Wyoming red squirrels (Tamiasciurus hudsonicus) and grouse (Bonasa umbellus and Dendragapus obscurus) are used by Canada lynx. Whether young forests or older multi-storied forests contain more snowshoe hares, red squirrels, and grouse in western Wyoming is currently unknown. We estimated snowshoe hare density, and indexed red squirrel and forest grouse abundance in 3 classes of 30-70-year-old lodgepole pine (Pinus contorta) and 4 classes of mature multi-storied forest with a spruce (Picea engelmannii)-fir (Abies lasiocarpa) component. We recorded landscape and forest structure characteristics to understand how these influence lynx prey abundance. Overall, snowshoe hares, red squirrels, and forest grouse were more abundant in multi-storied forests than young forests. Forest attributes that predicted prey abundance were often more prevalent in multi-storied forests. Results from this study suggest that multi-storied forests with a spruce-fir component were disproportionately important to snowshoe hares, red squirrels, and forest grouse in western Wyoming. Canada lynx conservation efforts should focus on maintaining, enhancing, and promoting multi-storied forests in this region.
Conference Paper
Complex chronic diseases are usually not caused by changes in a single causal gene but by an unbalanced regulating network resulting from the dysfunctions of multiple genes or their products. Therefore, network based systems approach can be helpful for the identification of candidate genes related to complex diseases and their relationships. The Axial spondyloarthropathy (SpA) is a group of chronic inflammatory joint diseases that mainly affects the spine and the sacroiliac joints, yet, the pathogenesis of SpA remains largely unknown. In this paper, we conducted a networked systems study on the pathogenesis of SpA. We integrated data related to SpA, from the OMIM database, proteomics and microarray experiments of SpA, to prioritize SpA candidate disease genes in the context of human protein interactome. Based on the top ranked SpA related genes, we constructed a PPI network and identified potential pathways associated with SpA. The PPI network and pathways reflect the well-known knowledge of SpA, i.e., immune mediated inflammation, as well as imbalanced bone modeling caused new bone formation and bone loss. This study may facilitate our understanding of the SpA pathogenesis from the perspective of network systems.
Thesis
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Computer printout. Thesis (M.S.)--University of Minnesota, Duluth : 2006. Includes bibliographical references (l. 51-54).
Article
Boreal ecosystems are experiencing extensive changes because of anthropogenic stressors such as climate change. Information on density of species at multiple sites is vital to understand and manage the impact of these changing conditions on boreal forest communities. Yet, for most boreal forest species, including the vast majority of mammals, obtaining reliable estimates of density is exceedingly difficult. Recently developed methods for the estimation of densities of unmarked animals from camera-trapping data could help to overcome this hurdle, but have not yet been empirically validated in many ecosystems. Here, we assess the ability of camera traps to estimate density of snowshoe hare (Lepus americanus) using three different models: the random encounter model (REM), the random encounter and staying time (REST) model, and the time-to-event (TTE) model. We additionally evaluate the relationship between hare density and two simple indices based on camera detection rate and pellet counts. Across 13 sites in North Central Washington, United States, we compared live-trapping spatially explicit capture–recapture (SECR) estimates of density to the three camera-based density models and the two indices. We found that the camera-based models, in particular the REM and REST models, performed well in estimating densities consistent with the live-trapping data, with an average difference in density from SECR-based estimates of only 0.12 and 0.13 hares/ha, respectively. Both indices also had strong predictive relationships with hare density. Our results show that, owing to their noninvasive nature and relative ease of application, camera-based methods could be used to obtain hare density estimates at much larger spatiotemporal scales than have been applied to date. Given the keystone role of hare in boreal ecosystems, and emerging evidence of hare range retraction, the ability to estimate densities across many sites is a key tool for hare conservation and management. Moreover, our results are highly encouraging for the application of camera-based methods to obtain density estimates on a wide variety of boreal forest species, though additional validation will be necessary.
Article
Snowshoe hares (Lepus americanus) are an important prey species and a dominant herbivore across much of their North American range, and researchers have questioned the influences of forestry practices that alter habitat for hares and the potential community-level effects on carnivores. We examined the effects of precommercial thinning (PCT) from 1 to 11 years posttreatment on snowshoe hares. In the commercial forests of northern Maine, USA, we counted and cleared hare pellets twice a year during 2001 and 2002 on >46 km of pellet transects across 30 regenerating conifer stands (17 treated with PCT) previously treated with an aerial application of herbicide. We compared densities of snowshoe hare pellets among 3 development classes with (1 yr after thinning, 6 yr after thinning, and 11 yr after thinning) and without thinning (stands with a similar history of clearcut and herbicide treatment but no thinning). During both years, densities of hares were lower in stands treated with PCT than in similar unthinned stands across the 3 development classes and during both leaf-off and leaf-on seasons (P < 0.001). Within both thinned and unthinned stands, hare density was greatest in stands in the 1-year development class when compared to the 6-year and 11-year development classes, but a statistical difference (P = 0.048) among classes was evident only during leaf-off seasons. Precommercial thinning was associated with densities of snowshoe hares that were approximately half of those in similar unthinned stands up to at least 11 years posttreatment; however, thinned stands may retain densities of hares greater than stands managed using other forest harvesting regimes. Our results apply to core portions of stands with crop trees spaced at 1.8–2.4-m intervals following complete overstory removal and herbicide treatment. We advocate caution when applying our results to other thinning regimes or across broader spatial scales.
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The systematic fecal pellet-group count has been used to estimate population parameters of various species. The Pacarana (Dinomys branickii) is characterized by defecating in latrines which are used repeatedly by a family group, so that sampling of the fecal pellets is an alternative, since the species lives in small populations with discontinuous distribution. However, the technique requires knowledge of the defecation rate and fecal morphology unknown for this species. The main objective of this study was to monitor the latrines in three populations of D. branickii with different numbers of individuals between males and females kept in a seminatural environment, in order to generate information on the morphology and the daily production of feces. For each group of animals the total number of droppings deposited at each latrine was collected, counted and measured. The total number of droppings/animal/day was obtained using fecal markers. The mean droppings per latrine varied according to group size. Individual defecation rates showed statistically significant differences between sexes. The cylindrical shape of the droppings of D. branickii shows a clear difference between the average length and width. The dimensions of the droppings varied more frequently in the latrines than in the individual samples. The estimation of the population size of D. branickii based on the use of latrines is promising, but needs to be validated in its natural habitat.
Article
We investigated habitat selection and home-range characteristics of American martens (Martes americana) that occupied home ranges with partially harvested stands characterized by basal area of trees <18 m2/ha and canopy closure <30%. During the leaf-on season (1 May–31 Oct), martens selected second-growth (80–140-years-old, >9-m tree height) forest stands (deciduous, coniferous, and mixed coniferous-deciduous) and mixed stands that were partially harvested (x̄ = 13 m2/ha residual basal area, >9-m tree height), and they selected against forests regenerating after clearcutting (≤6-m tree height, cuts ≤24-years-old). Marten home ranges included a greater proportion of partially harvested stands during the leaf-on season (maximum = 73%) than during leaf-off (1 Nov–30 Apr; maximum = 34%). Higher use of partially harvested stands during the leaf-on season coincided with greater canopy closure, higher use of small mammals, and greater relative densities of small mammals. During the leaf-off season, martens exhibited reduced relative selection for partially harvested and regenerating stands and increased selection for second-growth forest types. Partially harvested and regenerating clearcut stands had canopy closure <30% and basal area of trees >9-m tall of <13 m2/ha; both were below published thresholds required by martens. Coincidentally, home-range areas of martens increased during the leaf-off season to include a greater proportion of second-growth forest and less partially harvested forest. Further, martens with partial harvesting in their home ranges used areas almost twice as large during the leaf-off season as martens with no partial harvesting. Snowshoe hares (Lepus americanus) were prevalent prey for martens during the leaf-off season, and partially harvested stands had the lowest density of hares among all forest overstory types. Our findings suggest that the combination of insufficient basal area and overhead canopy closure, subnivean behavior of small mammals, increased reliance on hares, and reduced density of snowshoe hares relative to second-growth forest types reduced habitat quality in partially harvested stands during the leaf-off season. We suggest land managers retain basal areas >18 m2/ha and canopy closure >30% during winter to maximize use by martens in stands where partial harvesting is practiced.
Article
This technical note is a product of the Ecosystem Management and Restoration Research Program (EMRRP) work unit titled "Natural Resource Inventories for Special Status Species on Corps Operating Projects." The objective of this note is to provide information on methods for conducting inventories of mammalian species to satisfy the requirements of Level II Natural Resources Inventories for Corps of Engineers operating projects. General information is provided on survey methodologies for a variety of mammalian species, with emphasis on broadbased methods that can be used to obtain occurrence/non-occurrence data for multiple species within a community (Martin et al. 2006). Selected techniques used to survey ungulates (hoofed mammals), carnivores, lagomorphs (rabbits and hares), squirrels, large aquatic rodents (beavers, muskrats, nutria), ground-dwelling rodents, and insectivores (shrews and moles) are described. Methods to determine presence/absence and/or relative abundance are emphasized. Inventory methods for bats are addressed separately in Part II of Mammalian Survey Techniques (Martin et al., in preparation).
Thesis
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This thesis explores how different components of natural and human disturbance regimes shape the distribution of a key boreal forest herbivore, the snowshoe hare (Lepus americanus). I investigated both broad-­scale changes in hare abundance during forest succession and fine-­scale responses to heterogeneity created by canopy gap dynamics in old-­growth forests. I then evaluated how hare respond to silvicultural treatments designed to maintain the irregular structure of old-­growth stands using patterns of density-­dependent habitat selection and browse history reconstruction. Snowshoe hare followed a bimodal abundance distribution with stand age, with a pronounced peak in density between 40-­50 years post-­disturbance followed by a second more subtle increase phase during late-­ succession. Within old-­growth stands, canopy gaps offered areas of higher food availability, but foraging and movement behaviours indicated that hares perceived a greater risk of predation within openings. The structure of old-­growth stands thus appears to impose a trade-­off between acquiring food and avoiding predation. The response of snowshoe hare to forest harvesting depended on both disturbance intensity and local population density. Preference for uncut forest stands over harvest treatments with >50% tree retention quickly diminished as local populations increased. In contrast, preference for uncut forests over treatments with <20% tree retention became more pronounced with increasing local population density. Similarly, in the first years following harvesting, browse use patterns of white birch (Betula papyrifera) stems in low intensity treatments (>50% retention) remained similar to those in uncut old-­growth forest stands, whereas browse use declined rapidly in intensive harvest treatments (<20% retention) over the same period. These findings suggest that silvicultural treatments that conserve old-­growth forest structure can also maintain distributions of hare that are characteristic of late-­succession. This thesis helps to further our understanding of the links between snowshoe hare distribution and regional disturbance regimes in managed boreal forests.
Article
Understanding the ecological factors affecting habitat use by the Canada lynx (Lynx canadensis) and its primary prey, the snowshoe hare (Lepus americanus), could help formulate conservation strategies for this carnivore, which is federally listed as threatened and occurs in only four regions of the U.S.A. I measured vegetation characteristics and snowshoe hare densities in 15 regenerating conifer clearcuts and 21 partially harvested stands in northern Maine during the leaf-off seasons, 2005 and 2006; and the leaf-on season, 2005. Regenerating clearcut stands had been harvested between 1974 and 1985 and were subsequently treated with an aerial application of herbicide between 1982 and 1997. Partially harvested stands were last harvested between 1985 and 2004 and included selection harvests, shelterwood harvests, and overstory removal harvests. Vegetation characteristics varied widely across partially harvested stands. This variance can be described by two principal components associated with the conifer composition and understory density within these stands. Snowshoe hare densities also varied widely in partially harvested stands: 0.26-1.65 hares/ha for the combined 2005-2006 leaf-off seasons. All 21 partially harvested stands had lower hare densities than the mean hare density for regenerating conifer clearcuts (2.10 hares/ha, SE=0.22) during these two years. I modeled the relationship of individual vegetation variables to hare densities across the 36 stands surveyed using an information theoretic approach. Hare density during the leaf-off season was positively associated with conifer stem densigy and basal area removed was negatively related to the density of logs in the stand. These three variables explained 67% of the variance in observed hare densities; however, conifer stem density was the single variable that was most strongly related to hare densities. I used GIS modeling to evaluate the relationships between lynx occurrence/non-detection and hare density, bobcat occurrence, fisher harvest density, maximum snow depth, and elevation at the geographic range- and the home range-scales in Maine. At the geographic-scale, lynx occurrence was associated with: 1) areas of higher hare density, and 2) absence of bobcats. Within the geographic range of lynx, simulated home ranges centered on lynx occurrences were associated with: 1) higher hare densities, 2) absence of bobcats, and 3) an interaction between hare density and bobcat occurrence, compared to surveyed areas without lynx detections. Only two surveys detected both bobcats and lynx, but these data suggest geographic- and home range-scale allopatry between these two species. At the geographic scale, the area of land in regenerating clearcuts was positively associated with lynx occurrence, likely as a result of the high hare densities supported by regenerating clearcuts. Annual clearcutting in Maine has been decreasing since the early 1990's and this trend may result in less regenerating forest on the landscape in the future, which might have long-term negative consequences if the objective is to maintain or increase current population levels of Canada lynx in Maine.
Article
Studies of rabbits and hares often use fecal pellet counts to estimate population density, create indices of abundance, and monitor habitat use, because fecal pellet counts are more easily deployed and less labor intensive than visual surveys and live trapping. In some habitats, plot size and shape can affect the measured pellet density and the resulting estimates of habitat use by rabbits. We compared rabbit (Sylvilagus spp.) fecal pellet density estimates derived from 0.155-m² rectangular, 0.155-m² circular, 1-m² square, and 1-m² circular plots in southern California chaparral and coastal sage scrub communities to evaluate habitat use by rabbits. Pellet plots were not an effective sampling design in our chaparral site where rabbit pellet density was low. Our coastal sage scrub site had an abundance of fecal pellets, and pellet density estimates varied by plot design. The 0.155-m² plots were more easily deployed and counted, however they produced higher estimates of fecal pellet density, exhibited greater variance, and were unable to detect habitat differences in fecal pellet density. The 1-m² plots required more effort but produced lower pellet density estimates, exhibited less variation, and were both able to detect habitat differences in fecal pellet density. We recommend that researchers conducting rabbit fecal pellet counts in Californian Mediterranean scrub habitats use 1-m² circular plots for their ease of deployment, counting, and clearing and for their greater detection and precision in estimates of pellet densities.
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We counted the number of snowshoe hare (Lepus americanus) fecal pellets on 50 quadrats of 0.155 m2 on each of six areas near Kluane Lake, Yukon Territory, once a year from 1977 to 1983. On four of these areas we livetrapped hares once a month and estimated population density from the Jolly–Seber model. Average hare density for the year was linearly related to fecal pellet counts (r = 0.94) over the range 0–10 hares/ha. Mean turd counts also are related to the variance of these counts by Taylor's power law with exponent 1.30, indicating a clumped pattern in turd deposition. Fecal pellet counts provide a quick and accurate method for snowshoe hare censuses on an extensive scale.
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Habitat partitioning between sexes of snowshoe hares (Lepus americanus) was examined in relation to seasonal dominance patterns and other factors that influence intraspecific competition (population density, habitat quality, and habitat heterogeneity). Significant differences in microhabitat use between males and females were detected in three of the 12 comparisons made; males were associated with sites that had more understory cover and greater overstory cover, and females were at sites having a greater abundance of forage. Seasonal dominance and population density did not influence habitat segregation. Differences in use of habitats by males and females may have been a response to their different roles in reproduction.
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A variety of plot shapes and sizes have been used to estimate pellet densities of snowshoe hares (Lepus americanus), but we lack a clear understanding of whether plot shape and size affect measured pellet density. Snowshoe hare pellet densities associated with several plot designs were compared at 2 locations in the Rocky Mountains. Plot designs and pellet-inclusion rules were identical on both sites, but crews were independent. Density estimates were systematically biased by plot size and shape, with smaller plots and higher edge-to-area ratios leading to higher density estimates. In particular, the plot size and dimensions suggested by Krebs et al. (1987, 2001) produced the highest density estimates on both sites. Thus, we caution against using the regression equations developed by Krebs et al. (1987, 2001) if plot dimensions differ from theirs. Similarly, we believe that direct comparison of hare pellet densities (and, by inference, hares) between studies using different plot designs is not valid. Within the pellet density range associated with our study areas, we suggest using large circular plots except where comparison with other studies using Krebs et al.'s (1987, 2001) methodologies is vital. Large circular plots minimize potential inclusion bias associated with pellets on the plot boundary, are easy to implement, and are common in the literature.
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Eastern North America's spruce-fir forests have a unique ecological and human history which is reflected in their current vegetation, ownership patterns, and forest management practices. Furthermore, there are important differences within the region between the true boreal forest and the sub-boreal Acadian forest; this paper emphasizes the Acadian forest. Applying New Forestry to this region will require a modified approach which we outline by describing three basic principles. First, to provide the landscape context for New Forestry, we propose a triad of forest land allocation in which reserves and plantations would co-exist, surrounded by and embedded within a landscape managed by alternative silvicultural systems based on New Forestry principles. The second principle is that silvicultural systems should be patterned after local natural disturbance regimes. The third principle is that ecosystems that have been altered by past practices should be restored. Implementing these principles is discussed in a review of specific silvicultural practices: conservation and restoration of seed sources; retention of residual trees; long rotations; limited whole-tree harvesting; and two-aged stands maintained by irregular shelterwood cutting. At the landscape level we discuss how the triad might be implemented and the importance of size and distribution of harvest areas and riparian zones.
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Snowshoe hares exhibit eight to 11 year population fluctuations across boreal North America, typically with an amplitude of 10 to 25 fold. These fluctua- tions are synchronous across the continent, with the most recent peak densities occurring in 1990 and 1991. The numeric cycle is driven by changes in survival and reproduction, with annual survival of adults ranging from approximately five to 30% and annual natality ranging from approximately six to 20 leverets/female. These parameters show cyclic changes because of functional and numerical re- sponses of predators and changes in food supply. Predator densities show approxi- mately two to 10 fold fluctuations during the hare cycle. The cyclicity of hares may be partly explained by regular behavioral shifts, with repercussions on their physiology, availability to predators, reproduction, and survival. However, this hypothesis needs more empirical support before it can be accepted.
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We counted fecal pellets of snowshoe hares (Lepus americanus) once a year in 10 areas in the southwestern Yukon from 1987 to 1996. Pellets in eighty 0.155-m2 quadrats were counted and cleared each June on all areas, and we correlated these counts with estimates of absolute hare density obtained by intensive mark-recapture methods in the same areas. There is a strong relationship between pellet counts and population density ( r = 0.76), and we present a predictive log-log regression to quantify this relationship, which improves on our previously published 1987 regression, particularly at low hare densities. The precision of density estimates can be improved most easily by increasing the number of sets of quadrats in an area (one set = 80 plots), rather than increasing the number of plots counted within one set. The most important question remaining concerns the generality of this relationship for snowshoe hares living in other habitats in the eastern and southern portions of their geographic range.
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Current methods of evaluating wildlife habitat for management,purposes can be arranged in a hierarchy of increasing generality. The most general level is evaluation of wildlife habitat for entire com- munities on the basis of inferences drawn from vegetational structure. At the base of the hierarchy the high resolution studies, upon which accuracy at the higher hierarchical levels depends, usually assume that habitat quality for a species is positively correlated with the density of the species. If habitat quality for a wildlife species is a measure of the importance of habitat type in maintaining a particular species, habitat quality should be defined in terms of the survival and production characteristics, as well as the density, of the species occupying that habitat. Situations in which habitat quality thus defined is not expected to be positively
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The use of indices to evaluate small-mammal populations has been heavily criticized, yet a review of small-mammal studies published from 1996 through 2000 indicated that indices are still the primary methods employed for measuring populations. The literature review also found that 98% of the samples collected in these studies were too small for reliable selection among population-estimation models. Researchers therefore generally have a choice between using a default estimator or an index, a choice for which the consequences have not been critically evaluated. We examined the use of a closed-population enumeration index, the number of unique individuals captured (Mt+1), and 3 population estimators for estimating simulated small populations (N = 50) under variable effects of time, trap-induced behavior, individual heterogeneity in trapping probabilities, and detection probabilities. Simulation results indicated that the estimators produced population estimates with low bias and high precision when the estimator reflected the underlying sources of variation in capture probability. However, when the underlying sources of variation deviated from model assumptions, bias was often high and results were inconsistent. In our simulations, Mt+1 generally exhibited lower variance and less sensitivity to the sources of variation in capture probabilities than the estimators.
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Snowshoe hare (Lepus americanus) populations found at high densities can be estimated using fecal pellet densities on rectangular plots, but this method has yet to be evaluated for low-density populations. We further tested the use of fecal pellet plots for estimating hare populations by correlating pellet densities with estimated hare numbers on 12 intensive study areas in Idaho; pellet counts from extensive transects (n = 615) across northern Idaho enabled rectangular plots (0.155 m2) to be compared with paired small (0.155 m2) and large (1 m2) circular plots (metre-circle plots). Metre-circle plots had higher pellet prevalence, lower sample variance, and lower estimates of pellet density than the other plot types. Transects comprising circular plots required less establishment time, and observer training reduced the pellet-count bias attributable to plot shape. The number of hares occupying intensive study sites was correlated with pellet density on all plot types, but rectangular plots provided a slightly closer linear fit to hare numbers than did metre-circle plots. The relationship between pellet density and hare number may have been curvilinear rather than linear, but linear and nonlinear models provided similar numerical estimates over much of the range of pellet densities. These results indicate that pellet counts are a robust estimator of hare numbers in low-density populations, and that metre-circle plots represent an improvement over standard rectangular plots in terms of unbiased pellet counts, sacrificing little predictive power. We recommend using pellet counts in metre-circle plots for estimating populations of snowshoe hares in their southern distribution.
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MARK provides parameter estimates from marked animals when they are re-encountered at a later time as dead recoveries, or live recaptures or re-sightings. The time intervals between re-encounters do not have to be equal. More than one attribute group of animals can be modelled. The basic input to MARK is the encounter history for each animal. MARK can also estimate the size of closed populations. Parameters can be constrained to be the same across re-encounter occasions, or by age, or group, using the parameter index matrix. A set of common models for initial screening of data are provided. Time effects, group effects, time x group effects and a null model of none of the above, are provided for each parameter. Besides the logit function to link the design matrix to the parameters of the model, other link functions include the log—log, complimentary log—log, sine, log, and identity. The estimates of model parameters are computed via numerical maximum likelihood techniques. The number of parameters that are estimable in the model are determined numerically and used to compute the quasi-likelihood AIC value for the model. Both the input data, and outputs for various models that the user has built, are stored in the Results database which contains a complete description of the model building process. It is viewed and manipulated in a Results Browser window. Summaries available from this window include viewing and printing model output, deviance residuals from the model, likelihood ratio and analysis of deviance between models, and adjustments for over dispersion. Models can also be retrieved and modified to create additional models. These capabilities are implemented in a Microsoft Windows 95 interface. The online help system has been developed to provide all necessary program documentation.
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Includes vita. Thesis (M.S.) in Wildlife Ecology--University of Maine, 2003. Includes bibliographical references (leaves 145-164).
Article
Many investigators begin field studies by using convenience sampling and then collect only index values (i.e., raw counts). This combination of poor field practices is nearly certain to yield untrustworthy results. Numbers (i.e., index values) are not always data, and many numbers (large sample size) do not always mean good data. Instead, the word data implies an information content with respect to some objective. Often numbers can be collected, but they may not represent data because they have little meaning and cannot be interpreted without making critical, but very unrealistic, assumptions. Such numbers are not trustworthy and cannot lead to valid inferences about the population of interest. We have made serious errors in ad hoc surveys of many terrestrial populations; efforts are underway to try to alter survey protocol to lessen these deficiencies in some cases. However, new surveys are being planned for reptile, amphibian, and insect populations, and the same fundamental errors may be repeated. Convenience samples are being relied upon without a way to make valid inferences about populations of interest. Index values are being taken without regard for highly variable and perhaps time-trending detection probabilities. Numbers from such surveys will not provide a basis for reliable knowledge and will represent only wasted resources. We must improve our understanding of these 2 fundamental issues and obtain reliable information or professionals in other disciplines will not take us seriously. Delury (1954: 293) commented,"...it is an expensive impropriety to maintain that an untrustworthy estimate is better than none." Professors ought to instill in their students the importance of probabilistic sampling in field studies. Similarly, the use of index values ought to be discouraged strongly because alternatives exist that will provide, under given assumptions, meaningful parameter estimates, measures of their precision, and other forms of reliable hfformation (see Thompson et al. 1998, Seber and Schwarz 1999). Editors and referees must begin to ask whether the sample data were taken in such a way as to allow a formal inductive inference to the population of interest. Such information should appear clearly in the Methods section of papers submitted for publication. Data resulting from convenience sampling are not acceptable on fundamental grounds. Similarly, raw counts as index values are not reliable and should be published only in unusual circumstances. In my opinion, we need a much higher standard for what is intrinsically acceptable in our profession.
Article
Lepus americanus habitat use patterns were investigated in Maine using fecal pellet counts, snow track counts and livetrapping. - from Authors
Article
Winter feeding experiments with captive snowshoe hares (Lepus americanus) indicated a mean daily requirement of about 300 g of woody browse having a maximum diameter of 3-4 mm. Food supplies were measured near Rochester, Alberta, during 6 consecutive winters, (1970-71 to 1975-76). Food was insufficient for hare populations on 2 study areas during a cyclic peak (winter 1970-71) and the following winter; food was still in short supply on a 3rd study area 2 winters after the peak. Twenty hare exclosures and their control plots, established in 1968 and sampled in summer 1971 and 1972, showed that hares had reduced the total biomass of woody stems ≤1.5 cm in diameter by more than 50%. Browsing-intensity surveys conducted in 1971, at the end of the peak winter, disclosed that almost 50% of the woody stems had been severely or heavily browsed; 2 years later, less than 2% were so intensively browsed. Marked changes occurred in nutrient levels of 6 common browse species monitored during 1969-74, but these appeared unrelated in any causal way to changes in hare population parameters. Mortality of malnourished captive hares was significantly related to ambient winter temperatures. Results of these field observations and feeding trials are discussed in relation to the hypothesis that cyclic declines of snowshoe hare populations are initiated by overwinter food shortage.
Article
Sixteen snowshoe hares (Lepus americanus) were radiotracked between December 1977 and June 1979 in a 10-km2 area containing several upland and lowland habitat types. Radiolocations, winter track surveys, browse surveys, and pellet counts provided information on habitat use and selection. Overall trends included an avoidance of open habitats of all types, an increase in use of upland types at night and in the spring, and a correlation between intensity of hare use and percent cover of shrubs over 1 m tall. Individual hares varied considerably in patterns of habitat use. Nine of 16 radio-tagged hares were most often in lowland habitat types; 4 were most frequently in edge types. Habitat selection was strongest for alder (Alnus spp.) fen, upland-alder edge, and conifer bogs.
Article
The influence of forest understory characteristics on snowshoe hare (Lepus americanus) habitat use and density was studied in eastern (Cherryfield) and western (Pierce Pond) Maine during 1981-83. Fecal pellet counts indicated that hares at Cherryfield preferred hardwood and avoided mixedwood and open understories during the leaf-off season (Oct-May) (P < 0.05). At Pierce Pond, hares used softwood more and hardwood and open understories less than expected during leaf off (P < 0.05). Hardwood understories provided the densest cover at Cherryfield, whereas at Pierce Pond softwoods were the densest cover. Hares in both areas used dense understories less during the leaf-on season (Jun-Sep). Spring population densities (0.1-1.7/ha) were correlated with understory density (r = 0.94, P < 0.001). Overwinter survival also was associated with understory density (r = 0.74, P < 0.04). Dense understories provided escape and thermal cover.
Article
This paper describes and evaluates some techniques used in population studies of the snowshoe hare (Lepus americanus). Methods of live capture included use of baited and unbaited traps in runway sets, and the driving of hares into nets. Fur dyeing, ear tattooing, and web tagging of hind feet proved satisfactory marking devices. Embryos were aged in utero through palpation; body measurements, lens weights, penis shape, teat length, and uterine characteristics were useful for aging juvenile and adult hares. Miscellaneous techniques involved the detection of pregnancy, lactation and suckling, and the treatment of trap sickness.
Article
The use of indices to evaluate small-mammal populations has been heavily criticized, yet a review of small-mammal studies published from 1996 through 2000 indicated that indices are still the primary methods employed for measuring populations. The literature review also found that 98% of the samples collected in these studies were too small for reliable selection among population-estimation models. Researchers therefore generally have a choice between using a default estimator or an index, a choice for which the consequences have not been critically evaluated. We examined the use of a closed-population enumeration index, the number of unique individuals captured (Mt+1), and 3 population estimators for estimating simulated small populations (N = 50) under variable effects of time, trap-induced behavior, individual heterogeneity in trapping probabilities, and detection probabilities. Simulation results indicated that the estimators produced population estimates with low bias and high precision when the estimator reflected the underlying sources of variation in capture probability. However, when the underlying sources of variation deviated from model assumptions, bias was often high and results were inconsistent. In our simulations, Mt+1 generally exhibited lower variance and less sensitivity to the sources of variation in capture probabilities than the estimators.L'utilisation d'indices pour évaluer les populations de petits mammifères est très critiquée et pourtant les études publiées entre 1996 et 2000 sur les petits mammifères démontrent que l'utilisation d'indices est toujours la méthode la plus courante d'évaluation des populations. Dans la littérature, 98 % des échantillons recueillis pour les études étaient trop petits pour permettre le choix judicieux d'un modèle d'estimation de population. Les chercheurs se retrouvent donc devant un choix à faire entre une méthode par défaut ou un indice, choix dont les conséquences n'ont pas été évaluées de façon formelle. Nous avons examiné les résultats de l'utilisation d'un indice de dénombrement d'une population fermée, du nombre d'individus particuliers capturés (Mt+1), et de 3 estimateurs de population pour estimer de petites populations simulées (N = 50) soumises à des effets divers du temps, du comportement relié au piégeage, de l'hétérogénéité dans la probabilité de capture des individus et des probabilités de détection. Les résultats de cette simulation ont démontré que les estimateurs donnent des évaluations qui comportent peu d'erreur et qui sont d'une grande précision lorsque l'estimateur utilisé reflète les sources de variation sous-jacentes des probabilités de capture. Cependant, lorsque les sources de variation sous-jacentes s'éloignent des présuppositions du modèle, les chances d'erreur sont souvent élevées et les résultats sont changeants. Dans nos simulations, Mt+1 a généralement une faible variance et manifeste moins de sensibilité aux sources de variation des probabilités de capture que les autres estimateurs.[Traduit par la Rédaction]
Article
While Engeman (2003) makes a good case for the importance of study design and that studies that provide only index values are sometimes easier and less expensive, I find I do not agree with his central comments concerning the value of indices. Without estimates of detection probabilities, the use of index values is without a scientific or logical basis. Index values, almost by definition, are not "appropriately constructed"; they are fundamentally flawed. I believe we must focus increased attention on empirical estimates of detection probabilities as an integral part of study design, data collection, estimation, and valid inference.
Article
On the grounds of "the need to get the basics right in wildlife field studies," Anderson (2001:1294-1297) recently included a general condemnation of the use of population indices. My purpose in this brief note is to add a few paragraphs of my thoughts to the comments by Anderson (2001) with respect to indexing animal populations. In general, I agree with the quantitative concepts described by Anderson (2001); however, I would like to place his comments into a broader perspective of general statistical rigor, without condemning the use of population indices if they are appropriately constructed.
Article
Despite their wide use in scientific journals such as The Journal of Wildlife Management, statistical hypothesis tests add very little value to the products of research. Indeed, they frequently confuse the interpretation of data. This paper describes how statistical hypothesis tests are often viewed, and then contrasts that interpretation with the correct one. I discuss the arbitrariness of P-values, conclusions that the null hypothesis is true, Dower analysis, and distinctions between statistical and biological significance. Statistical hypothesis testing, in which the null hypothesis about the properties of a population is almost always known a priori to be false, is contrasted with scientific hypothesis testing, which examines a credible null hypothesis about phenomena in nature. More meaningful alternatives are brief-ly outlined, including estimation and confidence intervals for determining the importance of factors, decision theory for guiding actions in the face of uncertainty, and Bayesian approaches to hypothesis testing and other statistical practices.
Article
We investigated habitat selection and home-range characteristics of American martens (Martes americana) that occupied home ranges with partially harvested stands characterized by basal area of trees <18 m2/ha and canopy closure <30%. During the leaf-on season (1 May–31 Oct), martens selected second-growth (80–140-years-old, >9-m tree height) forest stands (deciduous, coniferous, and mixed coniferous-deciduous) and mixed stands that were partially harvested (x̄ = 13 m2/ha residual basal area, >9-m tree height), and they selected against forests regenerating after clearcutting (≤6-m tree height, cuts ≤24-years-old). Marten home ranges included a greater proportion of partially harvested stands during the leaf-on season (maximum = 73%) than during leaf-off (1 Nov–30 Apr; maximum = 34%). Higher use of partially harvested stands during the leaf-on season coincided with greater canopy closure, higher use of small mammals, and greater relative densities of small mammals. During the leaf-off season, martens exhibited reduced relative selection for partially harvested and regenerating stands and increased selection for second-growth forest types. Partially harvested and regenerating clearcut stands had canopy closure <30% and basal area of trees >9-m tall of <13 m2/ha; both were below published thresholds required by martens. Coincidentally, home-range areas of martens increased during the leaf-off season to include a greater proportion of second-growth forest and less partially harvested forest. Further, martens with partial harvesting in their home ranges used areas almost twice as large during the leaf-off season as martens with no partial harvesting. Snowshoe hares (Lepus americanus) were prevalent prey for martens during the leaf-off season, and partially harvested stands had the lowest density of hares among all forest overstory types. Our findings suggest that the combination of insufficient basal area and overhead canopy closure, subnivean behavior of small mammals, increased reliance on hares, and reduced density of snowshoe hares relative to second-growth forest types reduced habitat quality in partially harvested stands during the leaf-off season. We suggest land managers retain basal areas >18 m2/ha and canopy closure >30% during winter to maximize use by martens in stands where partial harvesting is practiced.
Article
Compared with forest interiors, forest edges typically have a different plant species composition and community structure, a phenomenon known as “edge effect.” Edge effects make the functional interior area of a forest smaller than its actual area. The objective of this study was to estimate how far the effects of agriculturally maintained edges penetrate the mixed hardwood forests of the Roanoke River Basin, North Carolina. I determined percentage cover for all vascular plant species in 10-by-100-meter belt transects on north-facing or south-facing edges of four relatively undisturbed forests. Changes in the percentage cover of individual species, the relative cover of exotic species, and species richness all indicated that edge effects penetrate deeper on south-facing edges (to 60 meters) than on north-facing edges (to 20 meters). Analyses of species responses to the edge showed a number of species to be edge oriented, but no species was found to be interior oriented. The results of multivariate analyses (ordination and cluster analysis) suggested that edge effects could be detected to 50 meters on south-facing edges and 10–30 meters on north-facing edges. These results allow us to better understand the difference between a forest’s actual area and its functional interior area.
Article
We show evidence of differential predation on snowshoe hares (Lepus americanus) by great horned owls (Bubo virginianus) and ask whether predation mortality is related to antipredator behaviour in prey. We predicted higher predation on (1) young and inexperienced hares, (2) hares in open habitats lacking cover to protect from owl predation, and (3) hares in above average condition assuming that rich food patches are under highest risk of predation. Information on killed hares was obtained at nest sites of owls and by monitoring hares using radio-telemetry. The availability of age classes within the hare population was established from live-trapping and field data on reproduction and survival. Great horned owls preferred juvenile over adult hares. Juveniles were more vulnerable to owl predation before rather than after dispersal, suggesting that displacement or increased mobility were not causes for this increased mortality. Owls killed ratio-collared hares more often in open than in closed forest types, and they avoided or had less hunting success in habitats with dense shrub cover. Also, owls took hares in above average condition, although it is unclear whether samples from early spring are representative for other seasons. In conclusion, these results are consistent with the hypothesis that variation in antipredator behaviours of snowshoe hares leads to differential predation by great horned owls.
Article
Includes vita. Thesis (M.S.) in Wildlife Ecology--University of Maine, 1997. Includes bibliographical references (leaves 57-67).
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Operational density control in spruce-fir sapling stands -production of a mechanical swath cutter and brush-saw workers. Maine Cooperative Forestry Research Note 14
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Seymour, R. S., R. A. Ebeling, and C. J. Gadzik. 1984. Operational density control in spruce-fir sapling stands -production of a mechanical swath cutter and brush-saw workers. Maine Cooperative Forestry Research Note 14, Orono, Maine, USA.
New forestry in eastern spruce-fir forests: principles and applications to Maine. Maine Agricultural and Forestry Experiment Station Miscellaneous Publication 716
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