Leonard F. Ruggiero

DNA reveals high dispersal synchronizing the population dynamics of Canada lynx

Population dynamics of Canada lynx (Lynx canadensis) have been of interest to ecologists for nearly sixty years. Two competing hypotheses concerning lynx population dynamics and large-scale spatial synchrony are currently debated. The first suggests that dispersal is substantial among lynx populations, and the second proposes that lynx at the periphery of their range exist in small, isolated patches that maintain cycle synchrony via correlation with extrinsic environmental factors. Resolving the nature of lynx population dynamics and dispersal is important both to ecological theory and to the conservation of threatened lynx populations: the lack of knowledge about connectivity between populations at the southern periphery of the lynxs geographic range delayed their legal listing in the United States. We test these competing hypotheses using microsatellite DNA markers and lynx samples from 17 collection sites in the core and periphery of the lynxs geographic range. Here we show high gene flow despite separation by distances greater than 3,100 km, supporting the dispersal hypothesis. We therefore suggest that management actions in the contiguous United States should focus on maintaining connectivity with the core of the lynxs geographic range.

Landscape location affects genetic variation of Canada lynx (Lynx canadensis).

The effect of a populations location on the landscape on genetic variation has been of interest to population genetics for more than half a century. However, most studies do not consider broadscale biogeography when interpreting genetic data. In this study, we propose an operational definition of a peripheral population, and then explore whether peripheral populations of Canada lynx (Lynx canadensis) have less genetic variation than core populations at nine microsatellite loci. We show that peripheral populations of lynx have fewer mean numbers of alleles per population and lower expected heterozygosity. This is surprising, given the lynxs capacity to move long distances, but can be explained by the fact that peripheral populations often have smaller population sizes, limited opportunities for genetic exchange and may be disproportionately affected by ebbs and flows of species’ geographical range.

Non-target effects of an introduced biological control agent on deer mouse ecology

Abstract Release of exotic insects as biological control agents is a common approach to controlling exotic plants. Though controversy has ensued regarding the deleterious direct effects of biological control agents to non-target species, few have examined the indirect effects of a ”well-behaved” biological control agent on native fauna. We studied a grassland in west-central Montana infested with spotted knapweed (Centaurea maculosa) to examine the effects of knapweed invasion and two gall flybiological control agents (Urophora affinis and U. quadrifasciata) on the native deer mouse (Peromyscus maniculatus). Stomach-content analysis revealed that Urophora were the primary food item in Peromyscus diets for most of the year and made up 84–86% of the winter diet. Stomach contents indicated that wild-caught mice consumed on average up to 247 Urophora larvae mouse–1 day–1, while feeding trials revealed that deer mice could depredate nearly 5 times as many larvae under laboratory conditions. In feeding trials, deer mice selected knapweed seedheads with greater numbers of galls while avoiding uninfested seedheads. When Urophora larvae were present in knapweed seedheads, deer mice selected microhabitats with moderately high (31–45% cover) and high knapweed infestation (≥46% cover). After Urophora emerged and larvae were unavailable to Peromyscus, mice reversed habitat selection to favor sites dominated by native-prairie with low knapweed infestation (0–15%). Establishment of the biological control agent, Urophora spp., has altered deer mouse diets and habitat selection by effecting changes in foraging strategies. Deer mice and other predators may reduce Urophora populations below a threshold necessary to effectively control spotted knapweed.

Hybridization between Canada lynx and bobcats: Genetic results and management implications

Hybridization between taxonomically similar species is an often-overlooked mechanism limiting the recovery of threatened and endangered species. We present molecular genetic data for the first time demonstrating that Canada lynx and bobcats hybridize in the wild. We verify that two microsatellite loci Lc106 and Lc110 have non-overlapping allele ranges between Canada lynx and bobcats, and that three putative lynx from Minnesota contain DNA from both bobcats and lynx. Additionally, we use a published test for the 16S rRNA region of mitochondrial DNA (mtDNA) to determine the maternal species; all hybrids had lynx mothers. Fifteen per cent (3/20) of our ‘putative lynx’ samples were hybrids, although these data are not from a representative sampling effort. Hybridization may be an under-appreciated factor limiting the distribution and recovery of lynx. The presence of hybrids is thus a new factor in the population management of both species with potential implications for hunting and trapping of bobcats.

Characteristics of American marten den sites in Wyoming

We examined characteristics of den structures and den sites used by female American marten (Martes americana) for natal and maternal dens in the Sierra Madre Range, Wyoming. During 1988-95, we located 18 natal dens (parturition sites) and 97 maternal dens (sites where kits were present exclusive of parturition) used by 10 female marten. Important den structures included rock crevices (28%), snags (25%), red squirrel (Tamiasciurus hudsonicus) middens (19%), and logs (16%). Resource selection function (RSF) analysis showed that an individual selection model provided a significantly better fit than a null model or pooled selection model, indicating that the sample of marten selected maternal den sites that differed from random sites, and that individual animals did not select maternal den sites in the same manner. Six marten individually exhibited significant selection for maternal den sites within home ranges. Overall selection coefficients for maternal dens indicated the number of squirrel middens was the most important variable, followed by number of snags 20-40 em diameter at breast height (dbh), number of snags 2:41 em dbh, and number of hard logs 2:41 em in diameter. Selection of natal den sites was also significant via comparison between selection and no-selection models, with number of middens, number of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) >20 em dbh, and number of hard logs 2:41 em in diameter the most important variables in descending order of importance. Large logs, large snags, and large, live spruce and fir trees are important characteristics for marten den sites in the central Rocky Mountains. The prominence of middens at den sites suggests red squirrels provide important denning structures as well as prey for marten.

Identification of mustelids using mitochondrial DNA and non-invasive sampling

, mitochondrial DNA, mtDNA, mustelids, non-invasivesampling,wolverineOne of the most fundamental issues in conservationbiology is the determination of species distributionand richness. Many species, including forest carni-vores, are elusive and secretive, making it difficult orimpossible to make even basic conservation decisionson listing, delisting, or threat status. Non-invasivesampling of hairs left on hair snares can substan-tially increase our detection of such species. In anextension of a nationwide project using hair snaresacross 12 states to identify lynx (

Winter Prey Selection of Canada Lynx in Northwestern Montana

Abstract The roles that diet and prey abundance play in habitat selection of Canada lynx (Lynx canadensis) in the contiguous United States is poorly understood. From 1998–2002, we back-tracked radiocollared lynx (6 F, 9 M) for a distance of 582 km and we located 86 kills in northwestern Montana, USA. Lynx preyed on 7 species that included blue grouse (Dendragapus obscurus), spruce grouse (Canachites canadensis), northern flying squirrel (Glaucomys sabrinus), red squirrel (Tamiasciurus hudsonicus), snowshoe hare (Lepus americanus), least weasel (Mustela nivalis), and white-tailed deer (Odocoileus virginianus). Snowshoe hares (69 kills) accounted for 96% (4-yr average, range = 94–99%) of prey biomass during the sample period. Red squirrels were the second-most-common prey (11 kills), but they only provided 2% biomass of the winter diet. Red squirrels contributed little to the lynx diet despite low hare densities. A logistic regression model of snowshoe hare, red squirrel, and grouse abundance, as indexed by the number of track crossings of use and available lynx back-tracks, was a significant (Wald statistic = 19.03, df = 3, P < 0.001) predictor of habitat use. As we expected, lynx (P < 0.001) selected use-areas with higher snowshoe hare abundance compared to random expectation. However, the red squirrel index had a weak (P = 0.087) negative relationship to lynx use, and grouse was nonsignificant (P = 0.432). Our results indicate that lynx in western Montana prey almost exclusively on snowshoe hares during the winter with little use of alternative prey. Thus, reductions in horizontal cover for hares would degrade lynx habitat.

Seasonal Resource Selection of Canada Lynx in Managed Forests of the Northern Rocky Mountains

Abstract We investigated seasonal patterns in resource selection of Canada lynx (Lynx canadensis) in the northern Rockies (western MT, USA) from 1998 to 2002 based on backtracking in winter (577 km; 10 M, 7 F) and radiotelemetry (630 locations; 16 M, 11 F) in summer. During winter, lynx preferentially foraged in mature, multilayer forests with Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) in the overstory and midstory. Forests used during winter were composed of larger diameter trees with higher horizontal cover, more abundant snowshoe hares (Lepus americanus), and deeper snow compared to random availability; multilayer, spruce–fir forests provided high horizontal cover with tree branching that touched the snow surface. During winter, lynx killed prey at sites with higher horizontal cover than that along foraging paths. Lynx were insensitive to snow depth or penetrability in determining where they killed prey. During summer, lynx broadened their resource use to select younger forests with high horizontal cover, abundant total shrubs, abundant small-diameter trees, and dense saplings, especially spruce–fir saplings. Based on multivariate logistic-regression models, resource selection occurred primarily at a fine spatial scale as was consistent with a sight-hunting predator in dense forests. However, univariate comparisons of patch-level metrics indicated that lynx selected homogenous spruce–fir patches, and avoided recent clear-cuts or other open patches. Given that lynx in Montana exhibit seasonal differences in resource selection, we encourage managers to maintain habitat mosaics. Because winter habitat may be most limiting for lynx, these mosaics should include abundant multistory, mature spruce–fir forests with high horizontal cover that are spatially well-distributed.

Hierarchical Den Selection of Canada Lynx in Western Montana

Abstract We studied den selection of Canada lynx (Lynx canadensis; hereafter lynx) at multiple ecological scales based on 57 dens from 19 females located in western Montana, USA, between 1999 and 2006. We considered 3 spatial scales in this analysis, including den site (11-m-radius circle surrounding dens), den area (100-m-radius circle), and den environ (1-km radius surrounding dens). Lynx denned in preexisting sheltered spaces created by downed logs (62%), root-wads from wind-thrown trees (19%), boulder fields (10%), slash piles (6%), and live trees (4%). Lynx preferentially selected den sites with northeasterly aspects that averaged 24°. Average distance between dens of 13 females monitored in consecutive years was 2,248 m, indicating low den site fidelity. Lynx exhibited habitat selection at all 3 spatial scales. Based on logistic regression, den sites differed from the surrounding den areas in having higher horizontal cover and log volume. Abundant woody debris from piled logs was the dominant habitat feature at den sites. Lynx generally denned in mature spruce–fir (Picea–Abies) forests with high horizontal cover and abundant coarse woody debris. Eighty percent of dens were in mature forest stands and 13% in mid-seral regenerating stands; young regenerating (5%) and thinned (either naturally sparse or mechanically thinned) stands with discontinuous canopies (2%) were seldom used. Female lynx selected den areas with greater spruce–fir tree basal area, higher horizontal cover, and larger-diameter trees compared to random locations within their home range. Lynx selected den environs in topographically concave or drainage-like areas, and farther from forest edges than random expectation. Maintaining mature and mid-seral regenerating spruce–fir forests with high horizontal cover and abundant woody debris would be most valuable for denning when located in drainages or in concave, drainage-like basins. Management actions that alter spruce–fir forests to a condition that is sparsely stocked (e.g., mechanically thinned) and with low canopy closure (<50%) would create forest conditions that are poorly suitable for lynx denning.

Nest-site preference of northern goshawks in southcentral Wyoming

In 1992, we studied the nest-site preference of goshawks (Accipiter gentilis atricapillus) nesting in lodgepole pine (Pinus contorta) forests of the Medicine Bow National Forest, southcentral Wyoming. For 39 active pairs of goshawks, we described nesting habitat at 3 spatial scales: nest tree, nest-tree area (0.04 ha circle centered at nest tree), and nest stand (homogeneous forest stand surrounding nest). Nest stands ranged from 0.4 ha to 13.0 ha (x = 2.7 ha, SE = 0.4). We compared habitat characteristics at nest-sites to those measured at random sites. The mean diameter at breast height (dbh) of nest trees was larger (P < 0.001) than the mean dbh of trees in either the nest-tree area or the nest stand. Nest trees also were taller (P < 0.001) and had greater dbh (P < 0.001) than trees in random stands. Slopes at goshawk nests were more (P = 0.04) moderate (x = 11%, SE 1.1, range 1 to 34%) compared to those available. Aspects at goshawk nests were similar (P = 0.61) to those available. The tree density in goshawk nest stands was lower (P = 0.045) than random stands. However, nest stands had a higher (P < 0.001) density of large trees compared to random stands. Trees in nest stands also were taller (P < 0.001) with greater (P = 0.006) heights to live canopy compared to trees in random stands. The mean density of small trees at nest stands was less than (P = 0.001) one-half those present in random stands. Nest stands were not old-growth in the classic sense of being multi-storied stands with large diameter trees, high canopy closure, and abundant woody debris. Rather, nest stands were in even-aged, single-storied, mature forest stands with high canopy closure (x = 65%, SE 1.4) and clear forest floors. We recommend changes in procedures for identifying mature and old-growth lodgepole pine forests and describe silvicultural methods for creating goshawk nest stands.