Alicia V. Linzey

Modeling Population Variation in Peromyscus leucopus: An Exploratory Analysis

Time-series analysis was applied in an exploratory analysis of density estimates for Peromyscus leucopus obtained over 9 years by weekly nest-box checks supplemented by live trapping. We developed a model that quantified the relationship between population density in a given month and density 1 month prior (1st-order autocorrelation), 12 months prior (seasonal effects), and 36 months prior (multiannual effects). The remaining variation was examined to determine the influence of stochastic variations in parameters of weather. In order of importance, predictors of density in a given month were density in the previous month (60.4% of variance explained), seasonality (6.1%), and multiannual effects (7.0%). Of the remaining 26.5% of variance, 3.4% was due to two weather factors; deviation from mean precipitation with a 5-month lag and high temperature with a 2-month lag. The population of P. leucopus was relatively resilient to abiotic effects over the 9 years. Quantitative models of this type are rare in the literature because gathering and adequately analyzing long-term ecological data is a demanding task. However, quantitative descriptions of variations in population density are essential to assessment of the relative importance of various mechanisms contributing to population regulation.

Effects of chronic polychlorinated biphenyls exposure on growth and reproduction of second generation white-footed mice (Peromyscus leucopus)

White-footed mice (Peromyscus leucopus) chronically exposed to polychlorinated biphenyls (PCBs) in the diet at a level of 10 ppm (μg/g) through the second generation were evaluated in regard to reproductive success, growth (body weight) and development of reproductive organs. PCBs-treated second generation mice exhibited poor reproductive success in comparison with second generation controls and the parental generation. Although young from second generation control and PCBs-treated litters did not differ in weight at birth, PCBs-treated young were significantly smaller at 4, 8, and 12 weeks of age. Similarly, reproductive organs of females (uteri, ovaries) and accessory glands of males were smaller in PCBs-treated mice at 8 and 12 weeks of age. Testes weights were unaffected by PCBs exposure. These results provide insight into the cumulative effects of chronic PCBs exposure.

Characteristics of a white-footed mouse (Peromyscus leucopus) population inhabiting a polychlorinated biphenyls contaminated site.

Demographic characteristics of a white-footed mouse (Peromyscus leucopus) population inhabiting a woodland containing a low level of PCBs contamination were compared to an uncontaminated reference site. Although population density was higher on the PCBs-contaminated grid, the population exhibited greater temporal variability among years and had a higher number of transient animals. These population trends are consistent with those observed in structurally suboptimal habitats, indicating that the PCBs-contaminated grid is functioning as a suboptimal habitat. However, the data are not compelling enough to firmly conclude that the differences are due to contamination rather than to undetected environmental variation between sites. If demographic differences due to contamination are slight, they will be difficult to detect against a background of demographic variation resulting from subtle environmental differences. We conclude that animals at this site experienced a level of contamination that was below threshold for unequivocal detection of demographic effects.

Effects of habitat disturbance on a Peromyscus leucopus (Rodentia: Cricetidae) population in western Pennsylvania

Abstract Many species of wild mammals occur in habitats that have been disturbed by fragmentation or degraded in quality. Previous researchers have hypothesized that demographic characteristics of populations may shift with changes in environmental conditions, with self-regulatory ability increasing with environmental suitability. We studied responses of white-footed mice (Peromyscus leucopus) to habitat disturbance. Given that optimal habitat for this species is deciduous woodland, we predicted that populations in habitats disturbed by cutting woody vegetation would be lower and more variable in density than in undisturbed habitat, density and stability of populations in disturbed habitat would increase over time, survival would be higher in undisturbed than in disturbed habitat, and populations in undisturbed habitat would show a greater degree of self-regulation. This 6-year study in western Pennsylvania involved 3 replicated study sites (each 3.8 ha), with woody vegetation removed on half of each site prior to beginning the study. Density in disturbed treatment averaged 65% of density in undisturbed habitat. There were no differences between treatments in survival or in population growth rates over time. Population trends over time were similar between treatments, populations in disturbed habitat did not become more stable with time, and density did not converge with that of undisturbed habitat. Although populations in the undisturbed habitat were clearly self-regulating, those in disturbed habitats were not. Despite expectations that demographic performance will align with environmental suitability, it may be difficult to ascribe a particular demography to a habitat generalist such as P. leucopus.

Aethomys chrysophilus (Rodentia: Muridae)

Abstract The genus Aethomys currently includes 11 species, but recent evidence indicates a need for taxonomic revision of the genus. Aethomys chrysophilus (De Winton, 1897) is a muroid rodent commonly called the red veld rat. A medium-sized rodent with a long, sparsely haired tail, A. chrysophilus is largely parapatric with its sibling species, A. ineptus, and in areas of co-occurrence, determination of chromosome number, mitochondrial DNA analysis, or morphology of spermatozoa are required to distinguish A. chrysophilus from A. ineptus. Endemic to Africa, A. chrysophilus is found in savanna–woodland habitats that include varying combinations of grass–herbaceous ground cover, shrub understory, and miombo or mopane woodlands. It is not of special conservation concern.

Aethomys ineptus (Rodentia: Muridae)

Abstract Aethomys ineptus (Thomas and Wroughton, 1908), commonly called the Tete veld rat, is a medium-sized rodent with a long, sparsely haired tail and spermatozoa with spatulate-shaped heads (unique for all muroid rodents thus far examined). A. ineptus co-occurs with its sibling species, A. chrysophilus, and in areas of co-occurrence, an examination of spermatozoa, diploid number, allozymes, or mitochondrial DNA is required to distinguish the 2. Previous work described as many as 11 species of Aethomys, but recent evidence indicates a need for taxonomic revision of the genus. Endemic to Africa, A. ineptus prefers habitats where there is substantial cover in the form of shrubs, rocks, and herbaceous vegetation. It is not of special conservation concern.

Women in Mammalogy (1940–1994): Personal Perspectives

We present autobiographical accounts of four women mammalogists whose careers collectively span the period of 1940-1994. All are long-term members of The American Society of Mammalogists and are actively involved in education and mammalogical research. In addition to discussing our interactions within the ASM, we discuss important influences in our early decisions to pursue a scientific career, the consequences of such decisions, and our subsequent career and family path.

James Nathaniel Layne (1926–2017)

James Nathaniel Layne (Fig. 1), 91, of Lake Placid, Florida passed away peacefully at home on 10 June 2017 surrounded by his daughters. He was born in Chicago, Illinois on 16 May 1926, a son of the late Leslie and Harriet (Hausmann) Layne. He married Lois Linderoth on 25 August 1950. They had been married for almost 66 years when Lois died in March 2016. Jim is survived by 5 daughters (Linda Farnsworth, Kimberly Crawford, Jamie Stayer, Susan Royce, and Rachel Troutman), 10 grandchildren, and 2 great-grandchildren. Jim grew up on Chicago’s north side. From the time he was 6 years old, when his father left the family, he and his younger brother were raised by his mother through the years of the Great Depression. His mother encouraged his interest in natural history. With additional nurturing from high school teachers, his early interest in birds of prey intensified during his teen years and he once remarked that he had trained an American kestrel to falconry as a youth. His first scientific paper dealt with the nests of hawks and was published in 1943 in the Illinois Audubon Society Bulletin. Following high school, Jim enlisted in the U.S. Army Air Force from 1943 to 1946, first as a preaviation cadet (1943–1944) and then on active duty (1944–1946). After being discharged in August 1946, he enrolled at Chicago City Junior College, but after a year there he transferred to Cornell University, where his interests expanded to include fishes and mammals. He earned his B. A. in 1950 (zoology and general studies) and Ph.D. in 1954 (major in vertebrate zoology/mammalogy; minors in botany and entomology) from Cornell. W. J. Hamilton, Jr. was chair of his Ph.D. committee. His first paper on mammals was a General Note in the Journal of Mammalogy in 1951 that described how an opossum (Didelphis virginiana) used its tail to carry nesting material. Jim returned briefly to Illinois as an Assistant Professor at Southern Illinois University, Carbondale (1954–1955), but accepted a position at the University of Florida, Gainesville in 1955, where he was an Assistant Professor (1955–1959) and then Associate Professor (1959–1963). During this same period, he was Assistant and then Associate Curator of mammals at the Florida State Museum. In 1963, he returned to Cornell University, where he accepted the position vacated by Dr. Hamilton upon his retirement. He remained at Cornell until 1967, when he became the first Director of Research at Archbold Biological Station, a research institute near Lake Placid, Florida (1967–1976). As the administrative structure at Archbold evolved over the years, Jim became the Station’s first Executive Director (1976–1985) and later Senior Research Biologist (1985–1993). Upon retirement in 1993, he continued his research as Senior Research Biologist Emeritus. As a teacher and mentor, Jim influenced many students during his career. He directed the research of 9 Ph.D. students and 5 Master’s students during his time at the University of Florida and Cornell University. He chaired committees of 9 other Journal of Mammalogy, 99(1):283–292, 2018 DOI:10.1093/jmammal/gyx172 Published online December 21, 2017