Thomas A. Nelson

Roost-Site Selection by Eastern Red Bats (Lasiurus Borealis)

Abstract To investigate natural roost-site selection by eastern red bats (Lasiurus borealis) in an urban area we equipped 12 bats with radio-transmitters and located them at 75 individual roost sites in central Illinois from 16 July to 30 September 1996. Bats used a diversity of roosts including mature trees, leaf litter, dense grass and the shingles of houses, but the majority of roosts (89%) were in the foliage or on the trunks of large deciduous trees (>45 cm dbh). Sweetgum (Liquidambar syraciflua) and oaks (Quercus spp.) were commonly used. Most roosts were located in foliage, >5 m above the ground, within 1.5 m of the edge of the crown and with few branches beneath to obstruct flight paths. Red bats showed fidelity to roost sites within a small geographic area, but not to particular roosts. Individuals rarely used the same roost on consecutive days, but 82% of roosts used on successive days were within 100 m of each other. In the cornbelt region of the Midwest, where forests have been extensively cleared and fragmented, large urban trees provide important roosting habitat for red bats.

Raccoons Use Habitat Edges in Northern Illinois

ABSTRACT Raccoons (Procyon lotor) have been implicated as important predators impacting nesting birds in the Midwest. Raccoon populations have increased dramatically in Illinois during the past 20 y prompting suggestions that lethal control programs may be warranted. Non-lethal approaches that separate avian nesting habitat from raccoon travel corridors may provide an acceptable alternative, but little is known about foraging patterns by raccoons in agricultural landscapes. Therefore, the objectives of this study were to: (1) evaluate home range size and movements of raccoons during the avian nesting season, (2) describe patterns of habitat selection at multiple spatial scales and (3) suggest management strategies to reduce the impact of raccoons on nesting birds. Twenty-one raccoons were radio-tracked at the Richardson Wildlife Foundation in northern Illinois from May through Aug. of 2002 and 2003. The mean 95% kernel home range was 60.5 ha and the mean 50% core area was 8.1 ha. Males moved faster than females at night, averaging 355.5 m/h vs. 192.3 m/h, respectively. Raccoons tended to follow linear landscape features such as fencerows, forest edges and mowed trails as they foraged at night. Home ranges contained more forest edge and less cropland than expected, and within their home ranges, raccoons foraged selectively along forest edges and wetlands, but generally avoided grasslands and crop fields.

Microsatellite analysis of mating and kinship in beavers (Castor canadensis)

Abstract Monogamy is rare among mammals and molecular investigations have revealed that many socially monogamous species participate in extrapair mating. The North American beaver (Castor canadensis) is a socially monogamous species that exhibits classic monogamous behavior, generally living in discrete colonies composed of a mated pair and their offspring. We examined genetic relationships within and among beaver colonies for 2 populations in Illinois to investigate average relatedness within colonies, occurrences of extrapair mating within or between colonies, and the influence of geographic distance on intercolony relatedness. Seven microsatellite loci developed for the beaver were used to estimate relatedness and parentage for 55 beavers in central Illinois and 72 beavers in southern Illinois. Average within-colony relatedness varied widely in both populations, ranging from 0.04 to 0.64 in central Illinois and from 0.16 to 0.41 in southern Illinois. Colonies were composed primarily of 1st- and 2nd-order relatives, but included unrelated individuals. Paternity analysis revealed that 5 (56%) of 9 litters had been sired by ≥2 males. Extrapair mating frequently occurred between members of neighboring colonies in southern Illinois. In contrast to long-held views that beavers are genetically monogamous and colonies are typically 1st-order relatives, we documented a wide range of relationships among colony members and multiple paternity in >50% of litters.

Composition and Demographics of Beaver (Castor canadensis) Colonies in Central Illinois

Abstract Beavers (Castor canadensis) exhibit wide variations in colony composition and demographics over their broad geographic range, so regional population studies are important for sound management of this species. The objectives of this study were to investigate the: (1) size and sex-age composition of beaver colonies in Illinois, (2) reproductive potential of female beavers in these colonies and (3) efficacy of night-vision surveys versus removal trapping for estimating colony size. We harvested and aged 239 beavers (128 males:111 females) during the 1999–2000 and 2000–2001 trapping seasons. The average colony contained 5.6 beavers. Family groups consisting of a breeding pair and at least 1 offspring composed 86% of these colonies; the other 14% consisted of only a breeding pair. Samples of beavers harvested by commercial trappers were skewed towards yearlings and 2-y olds relative to samples taken from trapped-out colonies. Fetal rates were 3.0, 3.4 and 4.2/female for yearlings, 2-y olds and older adults, respectively. In utero loss was estimated as 13%. Our estimates suggest that over 50% of kits die during the first 6 mo of life. We found no evidence that the presence of older offspring in a colony allowed parents to raise more kits. Night-vision surveys conducted 10 m downwind from the den for 2.5 h after sunset underestimated the size of colonies, accounting for only 55% of the beavers present.

Canine heartworms in coyotes in Illinois.

Canine heartworm (Dirofilaria immitis) disease affects wild canids and may be a factor impacting the health and population dynamics of coyotes (Canis latrans). Coyotes may serve also as a potential reservoir for transmission of these parasites to domestic dogs. We investigated 920 coyotes harvested by hunters and trappers throughout Illinois (USA) from 1995–1997. The objectives of the study were to: 1) survey the regional prevalence and intensity of heartworms in coyotes in Illinois, 2) determine whether heartworm intensity correlates with physical condition, particularly body weight and winter fat levels, and 3) evaluate the relationship between heartworm infections and the reproductive success of females. Prevalence of heartworms statewide was 16.0%. Prevalence was significantly higher in males (17.7%) than in females (14.1%; P=0.04) and was higher in the older age-classes (P<0.0001). The regional prevalence of heartworms increased from northern to southern Illinois. Intensity ranged from 1 to 111 with a mean of 8.7 (SD=13.2) worms. Intensities did not differ significantly between sexes (P=0.53) or among age-classes (P=0.84). Most infected coyotes had low intensity infections, 78.2% carried <12 heartworms, 11.6% had 12–24 worms, and 10.2% were infected with >24 worms. Body weights were not correlated with the presence of heartworms, nor were levels of kidney fat and marrow fat. However, reproductive success was lower in infected females. The percent of yearling females that bred was lower among infected females, as was the number of offspring produced by adults ≥3.5 yr old. Our study demonstrates that heavy infections adversely affect fur quality and reduce fecundity of some females, but these effects are small and few coyotes (4.1%) had enough worms to trigger them. Coyote populations have increased in Illinois during the past 20 yr, but prevalence and intensity of heartworm disease appears to have changed little in that period. We conclude that heartworm disease is only a minor factor influencing coyote population dynamics in Illinois.

Birth size and growth of deer fawns in southern Illinois

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Habitat Selection and Movements of Raccoons on a Grassland Reserve Managed for Imperiled Birds

Abstract Seasonal habitat selection and foraging movements are important aspects of predator ecology, and individual movements can provide a method to link predator–prey dynamics to the spatial mosaic of the environment. Prairie Ridge State Natural Area in Jasper County, Illinois, is a highly fragmented reserve that provides critical habitat for many declining grassland-dependent birds. Nest predation in this area is likely to be substantial because of high mesopredator populations. We undertook a 2-year telemetry study to investigate raccoon (Procyon lotor) movements and habitat selection on the reserve. During the avian nesting season, raccoon pathways had significantly lower fractal dimension, indicating more linear movements and less searching behavior than for fall–winter pathways. Movement distances and rates did not differ between the sexes or seasons. Habitat selection was significantly different among seasons on 2 hierarchical levels. Raccoons generally avoided grasslands in spring and summer, and the shape of pathways indicated that raccoons apparently did not search for nests in grassland habitats. Consequently, nest predation likely occurred incidentally as raccoons moved across grasslands to richer food patches such as wetlands, streams, and residential areas.

Isolation and characterization of microsatellite loci in the beaver (Castor canadensis).

We have isolated and characterized 10 microsatellite loci in the beaver (Castor canadensis). Sixty individuals from southern and central Illinois were screened at each locus. All loci exhibited moderate levels of polymorphism, ranging from five to 13 alleles per locus with average heterozygosity ranging from 0.317 to 0.867. Locus Cca5 deviated significantly from HWE (P < 0.001). The locus pair Cca4/Cca5 was shown to be in linkage disequilibrium in southern Illinois, but not in the central Illinois population. The remaining eight loci will be useful in investigations of mating and kinship patterns in beaver populations in Illinois.

Genetic Population Structure Within and Between Beaver (Castor canadensis) Populations in Illinois

Abstract Mating behavior and social structure can influence genetic structure within and between populations, yet most studies focus on highly kin-structured, polygynous species. The North American beaver (Castor canadensis) is socially monogamous; however, examination of recent genetic data suggests that this species may be opportunistically promiscuous. We used 7 microsatellite loci to quantify genetic structure within and between 2 beaver populations in Illinois. An analysis of molecular variance revealed significant genetic subdivision among breeding groups in southern Illinois (FST = 0.086, P < 0.001), whereas regional genetic subdivision was evident in central Illinois (FST = 0.037, P < 0.001). Overall FST between populations also was significant (0.068 ± 0.012 SE, P < 0.001). Bayesian clustering assigned individuals from the 2 geographic sampling regions into 2 distinct genetic clusters with 70% of individuals assigned to 1 of the 2 clusters. Migration between populations was low at 0.16 individuals/generation (confidence interval = 0.0079–0.33). Estimates of population subdivision, cluster analysis, and dispersal indicate that these populations are genetically distinct, but are connected by infrequent dispersal.

A Comparison of Field and Molecular Techniques for Sexing Beavers

Abstract The traditional method of sex identification in beavers (Castor canadensis) by external palpation can be inaccurate. We tested 2 genetic methods for determining sex in beavers, the zinc-finger DNA marker and the Y chromosome–specific sex determining region (SRY) marker. The SRY marker identified sex correctly in 57 of 67 (85%) beavers, whereas the zinc-finger technique was successful less often in only 48 of 67 (72%) animals. Sex was correctly assigned by palpation for 21 of 27 beavers (78%). Beaver studies in which accurate sex identification is critical may benefit by verifying the sex of individuals using one or both of these molecular markers.