Dynamics of Peripheral Populations of Great Basin Pocket Mice, Perognathus parvus, and Western Harvest Mice, Reithrodontomys megalotis, in Southern British Columbia

The Great Basin Pocket Mouse (Perognathus parvus) and Western Harvest Mouse (Reithrodontomys megalotis) are two peripheral species occurring in the southern Okanagan Valley of British Columbia, Canada. Both species are listed as vulnerable to extirpation because of habitat loss, primarily due to conversion of natural habitat to agricultural uses and suburban expansion. Population dynamics of these two species were studied in three habitat types: old field, sagebrush, and pine forest. The Great Basin Pocket Mouse occurred at densities ranging from 12 to 28/ha in sagebrush habitats and at 2-8/ha in old fields and Ponderosa Pine forest. The Western Harvest Mouse occurred at variable densities up to 10/ha in old fields and up to 5/ha in sagebrush habitats. Mean number of lactating females for Great Basin Pocket Mice ranged from 4-8 in sagebrush, 1-5 in old fields and pine forests combined. Mean juvenile survival to adulthood ranged from 3.28 young Great Basin Pocket Mice per pregnant female in sagebrush, 4.67 in old field, and 1.82 in pine forest habitats. Mean juvenile survival to adulthood of Western Harvest Mice ranged from 1.46-1.72 young per female in old field and sagebrush habitats. Conservation of habitat features (high biomass and structural diversity of grasses and forbs) in linear habitats has the potential to maintain populations of Western Harvest Mice. The Great Basin Pocket Mouse needs features of sagebrush and old field habitats that need to be conserved as natural non-linear components in mosaics of natural and anthropogenic habitats. Both species could act as “indicators” of habitat integrity for a wide range of other vertebrate, invertebrate, and plant species in the Okanagan Valley

Population Dynamics of Deer Mice, Peromyscus maniculatus, and Yellow-pine Chipmunks, Tamias amoenus, in Old Field and Orchard Habitats

There are often several rodent species included in the small mammal communities in orchard agro-ecosystems. This study was designed to test the hypothesis that the population levels of Deer Mice (Peromyscus maniculatus) and Yellow-pine Chipmunks (Tamias amoenus) would be enhanced in old field compared with orchard habitats. Rodent populations were intensively livetrapped in replicate old field and orchard sites over a four-year period at Summerland, British Columbia, Canada. Deer Mouse populations were, on average, significantly higher (2.5 – 3.4 times) in the old field than orchard sites in summer and winter periods. Mean numbers/ha of Deer Mice ranged from 12.1 to 60.4 in old field sites and from 3.3 to 19.9 in orchard sites. Breeding seasons in orchards were significantly longer than those in old field sites, in terms of proportion of reproductive male Deer Mice. Recruitment of new animals and early juvenile survival of Deer Mice were similar in orchard and old field sites. Populations of Yellow-pine Chipmunks ranged in mean abundance/ha from 5.6 – 19.0 in old field sites and from 1.9 – 17.5 on one orchard site, with no difference in mean abundance in 2 of 4 years of the study. Recruitment and mean survival of Yellow-pine Chipmunks also followed this pattern. This study is the first detailed comparison of the population dynamics of these rodent species in old field and orchard habitats. These species should be able to maintain their population levels and help contribute to a diversity of small mammals in this agrarian landscape

The digestive tract of a harpacticoid copepod, Tiqriopus californicu: a light and electron microscope study

A study on the digestive tract of a harpacticoid copepod, 2i3lio£Ss californicus, was carried out using techniques of light and electron microscopy. It was found that a curved, cuticulized esophagus extends from the ventral mouth to the midgut. Its musculature and shape allows fairly large food particles to enter the gut. The noncuticulized portion of the digestive tract consists of; 1. A single, anterior, spherical midgut caecum, 2. An anterior midgut extending from the midgut caecum to the joint at the beginning of the urosome, 3. A posterior midgut extending almost the length of the urosome. The cuticulized hindgut can be divided, structurally, into anterior and posterior regions. It is suggested that the anterior hindgut functions in ion and water regulation as well as begins the formation of a faecal pellet. The posterior hindgut compacts the faecal pellet and retains it until defaecation. At the light and electron microscope levels four cell types could be distinguished. By studying the cell's position in the gut, electron density, amount of lipid, amount and type of vesiculation and the abundance and position of the cell*s organelles, functions for these cells were determined: 1. cell type one is an embryonic cell which will replace cells worn away or lost in secretion. 2. Cell type two functions mainly in the synthesis and secretion of proteins and also plays a role in lipid absorption. 3. Cell type three appears to function mainly in lipid absorption. 4. Cell type four also functions in lipid absorption but this cell is only found in the anterior midgut and the type of vesicles found in this cell suggest a different type of absorption is occurring than in cell type three. From the abundance of each cell type, the length of the microvilli, the development of the basal lamina and luminal projections, the following conclusions were made: 1. The midgut caecum functions mainly for absorption of digested nutrients. 2. The anterior midgut also functions for nutrient absorption but plays a more important role in merocrine and exocrine secretion. The presence of concretions in cell types two and three of the anterior midgut suggest a role in excretion, water or ion regulation. 3. The posterior midgut functions mainly in absorption, though some holocrine secretion is evident.Science, Faculty ofBotany, Department ofGraduat

Influence of nitrogen fertilization on abundance and diversity of plants and animals in temperate and boreal forests

Aerial and land-based applications of nitrogen-based fertilizers to enhance forest growth makes nutrients potentially available to all trees, plants, and wildlife in a given ecosystem, and therefore may have direct and indirect effects on wildlife and biodiversity. A scientific review of these potential effects was conducted with 106 published studies covering vascular and non-vascular plants, amphibians, birds, mammals, terrestrial invertebrates, and soil animals associated with fertilization in temperate and boreal forests, primarily in North America and Scandinavia. In terms of direct effects, amphibians and domestic mammals appear to be the most sensitive to urea used in fertilization programs. The avoidance behaviour and/or mortality of amphibians in laboratory studies was species-dependent. Ruminant animals, including wild ungulates, rapidly convert urea to ammonia and are susceptible to toxicity following ingestion of large amounts of urea. Feeding on urea pellets by small mammals or gallinaceous birds appears to be minimal as granules are unpalatable. In terms of indirect effects, the majority of responses of understory herbs to nitrogen fertilization showed an increase in abundance. Some shrubs in repeatedly fertilized stands eventually increased in abundance in long-term studies, whereas dwarf shrubs and abundance of bryophytes (mosses and terrestrial lichens) declined. In general, species richness and diversity of understory herbs and shrubs declined, or were unaffected, in fertilized stands. Response in abundance and species richness-diversity of vascular plants to a single application of nitrogen showed either an increase or no change. Repeated applications (2-5 and > 5) usually resulted in declines in these responses. Relative abundance of mule deer (Odocoileus Rafinesque spp.), moose (Alces alces L.), and hares (Lepus L. spp.), and forage quantity and quality were usually increased by fertilization. Small mammal species generally showed increases or no change in abundance; decreases may be related to fertilizer-induced changes in food sources. Forest fertilization may provide winter feeding habitat for coniferous foliage-gleaning insectivorous birds in some cases. Six species of forest grouse showed no response to fertilizer treatments. Responses of soil animals to nitrogen fertilization appeared to be species- and dose-specific and ameliorated by surrounding micro- and macro-habitat characteristics.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Influence of Removal Sampling of Small Mammals on Abundance and Diversity Attributes: Scientific Implications

Terrestrial small mammals occupy a variety of temperate and boreal forests in North America and Eurasia and contribute to biodiversity within these ecosystems. Researchers commonly use a variation of removal trapping to sample small-mammal populations and communities in these systems. However, it is not known if recurrent removal sampling might bias abundance estimates or alter the very populations under study. We addressed 2 questions: (1) are estimates of population size and species richness and diversity gained from removal trapping different from those based on live-trapping? and (2) what residual impact does removal trapping have on small-mammal populations and communities, as revealed by live-trapping? In 2 experiments (summer 2004 and autumn 2005), we compared undisturbed controls (non-removal) with removal sampling for 5-, 10-, and 30-night periods. Total abundance estimates during removal periods were dramatically higher (up to 3-fold) on non-removal than removal sites in both experiments. Mean abundance of the 2 most common species, deer mouse (Peromyscus maniculatus) and northwestern chipmunk (Neotamias amoenus), were substantially higher on non-removal than removal sites in the autumn experiment. The longer the removal interval, the deeper the degree of departure from non-removal levels of abundance. Species richness during removal periods also followed the pattern of abundance, whereby new, uncommon species appeared on removal sites, but not non-removals, during the autumn experiment. The residual impact of removal trapping, as revealed by live-trapping, indicated that abundance estimates were up to 4.5-fold higher on non-removal than post-removal sites and continued for at least 1 month as the small mammal community reorganized itself via immigration and settlement. Species diversity was still significantly different among removals 8 months after the autumn removal period. Removal-trapping over variable lengths (5 to 30 nights) may not provide an accurate picture of the abundance or diversity of small mammals

Demography of montane voles in old field and orchard habitats in Southern British Columbia

Voles (Microtus spp.) occupy perennial grasslands and agricultural areas in many parts of North America. This study was designed to provide a detailed analysis of the population dynamics of montane voles (M. montanus) in old field and orchard habitats. Vole populations were intensively live-trapped in replicate old field and orchard sites over a 4-year period (1982-86) at Summerland, British Columbia, Canada. Populations of montane voles reached peak densities of 186 and 144 voles/ha in old field sites before declining to numbers averaging less than 60 voles/ha. Orchard populations of montane voles also followed this pattern but at consistently lower numbers than old field sites. This difference in abundance ranged from 2.3-3.6 times during the peak year to 23.8-116.3 times in the decline year, at which time montane voles had declined to a mean number of 0.3-2.4 voles/ha in orchard sites. Length of breeding seasons, proportion of reproductive voles, and mean number of recruits were generally similar in old field and orchard sites. Overall mean survival of voles tended to decline through time in orchard sites, averaging 0.47 compared with old field survival of 0.76. Mean body mass of voles was consistently higher in old field than orchard sites. Montane vole populations in orchards seemed to be linked to source area dynamics of populations in old fields

Long-Term Changes in Abundance and Composition of Forest-Floor Small Mammal Communities in a Landscape with Cumulative Clearcutting

Responses of forest-floor small mammals to clearcutting are species-specific with generalists occupying a range of habitats, and specialists persisting on clearcuts for variable periods. We investigated the responses in abundance and species composition of small mammal communities to cumulative clearcutting of coniferous forests on a landscape that had four independent clearcutting events (Periods 1 to 4) over a 42-year interval from 1979 to 2020 in south-central British Columbia, Canada. We ask if the small mammal communities have changed significantly over these decades owing to removal of old-growth forest by clearcut harvesting. Hypotheses (H) predicted that the small mammal community would (H1) increase in abundance, species richness, and diversity on new clearcuts owing to the availability of early seral post-harvest habitats from cumulative clearcutting; and (H2) have higher mean abundance, species richness, and species diversity in clearcut than uncut forest sites, owing to availability of vegetative food and cover. A third hypothesis (H3) predicted that abundance of (i) early seral vegetation (herbs and shrubs) and (ii) small mammal populations, will be greater in ungrazed clearcut sites than in those grazed by cattle (Bos taurus). Mean total numbers of small mammals on new clearcuts declined in Periods 3 and 4, and hence did not support the abundance part of H1. Much of this decline was owing to low numbers of the long-tailed vole (Microtus longicaudus) and meadow vole (M. pennsylvanicus). Two generalist species: the deer mouse (Peromyscus maniculatus) and northwestern chipmunk (Neotamias amoenus), contributed to high mean species richness and diversity in Periods 2 and 3 before these metrics declined in Period 4, and hence partly supported H1. The similarity in mean total numbers of small mammals in Periods 2 to 4 did not support the abundance prediction of H2 that total numbers would be higher in clearcut than uncut forest sites. Higher mean species richness (Periods 2 and 3) and diversity (Period 3) measurements on clearcut than forest sites, particularly in the early post-harvest years, did support these parts of H2. The vegetation part (i) of H3 was not supported for herbaceous plants but it was for shrubs. The small mammal part (ii) of H3 that populations would be higher in ungrazed than grazed clearcut sites was supported for abundance but not for species richness or diversity. The decline and near disappearance of both species of Microtus was possibly related to the reduction in plant community abundance and structure from grazing (at least for shrubs) and potentially from drought effects associated with climate change. Loss of microtines from these early seral ecosystems may have profound negative effects on various ecological functions and predator communities.Forestry, Faculty ofNon UBCForest and Conservation Sciences, Department ofReviewedFacultyResearche

Population Fluctuations of the Deer Mouse (Peromyscus maniculatus) in Old-Field and Bunchgrass–Sagebrush Habitats : The Role of Agricultural Setting and Optimum Habitat

In semiarid regions, the deer mouse (Peromyscus maniculatus) is a major small mammal species occupying perennial grassland habitats that include old-fields, native bunchgrass–sagebrush, and some agricultural settings. We investigated population changes in deer mouse populations in perennial grasslands, both natural and old-field, from 1982 to 2003 in southern British Columbia, Canada. Hypotheses (H) predicted that P. maniculatus populations will have (H1) multiannual fluctuations in abundance driven by population increases from extended breeding in summer and winter; (H2) relaxed spring reorganization events in some years leading to higher overall recruitment and survival; and (H3) interspecific competition with montane voles that causes deer mice to be lower in density when voles are higher. P. maniculatus populations in old-field and grass–sagebrush sites had clearly defined periods of high “peak” mean numbers (32–52/ha) and other times of low mean numbers (20–22/ha). Based on mean annual peak density in autumn, deer mouse populations exhibited fluctuations of 3–4 years in both habitats, but this pattern was not always present. The greater numbers of P. maniculatus in high than low years was directly related to population increases from extended breeding seasons and an increased number of lactating females, thereby supporting H1. Spring breeding season declines occurred but were similar or less in high than low years of mean abundance and were relaxed in comparison to forest populations of deer mice in other studies. Thus, H2 was supported for recruitment with high numbers of young-of-the-year breeding and total number of juvenile recruits but for survival was equivocal. Total summer survival was consistently higher in high than low population years but juvenile productivity in all years was poor. Mean abundance of P. maniculatus and M. montanus in old-field sites were highly correlated, and hence H3 was not supported. This latter result is the first, to our knowledge, of P. maniculatus coexisting in a similar pattern of population fluctuations with a Microtus species in a mainland grassland habitat. Higher than average precipitation in the year preceding a peak population of deer mice may have enhanced herbaceous vegetation and contributed to population increases in both habitats. We conclude that the old-field habitat associated with this agricultural setting provides optimum habitat for P. maniculatus and facilitates multiannual population fluctuations in this species.Land and Food Systems, Faculty ofNon UBCReviewedFacultyResearche

Long-term influence of glyphosate herbicide on demography and diversity of small mammal communities in coastal coniferous forest

This study tested the hypothesis that (1) abundance and related demographic parameters of small mammal populations, and (2) species diversity of small mammal communities, would be adversely affected in herbicide-treated habitats at 9 and 11 years after treatment in coastal coniferous forest. Study areas were located in south-coastal British Columbia, Canada, in the Coastal Western Hemlock (CWH-dm) biogeoclimatic zone where small mammal populations were intensively sampled on paired control and treatment sites. Average density of deer mice (Peromyscus maniculatus) during summer periods (1981-1990) was lower in the treatment than control in the immediate post-treatment (PT) period (1982), with comparable numbers in 1983, 1985, and 1990. At the 11-year PT area, deer mouse numbers were similar on control and treatment sites in 1978, 1979, 1980, and 1990. Average density of Oregon voles (Microtus oregoni) was higher on treatment than control sites at 9 and 11 years after treatment. Townsend chipmunks (Eutamias townsendii) tended to be less abundant on the treatment than control site 9 years PT but were essentially absent from the 11-year PT study area. There was no difference in average density of shrew (Sorex spp.) populations between control and treatment sites at either study area. It is likely that post-harvest successional change has more of an impact on small mammal abundance than change induced by a herbicide treatment. Our results suggest that glyphosate herbicide did not adversely affect reproduction, survival, or growth of deer mice and Oregon voles in coastal forest a decade after application. Species richness and diversity of small mammal communities changed little over the decade following treatment. This study is the first investigation on the effects of forest herbicide use on demography and diversity of small mammal communities that extends to a decad

PREDATOR ODORS AND THEIR POTENTIAL ROLE IN MANAGING PEST RODENTS AND RABBITS

The snowshoe hare (Lepus americanus). several species of voles (Microtus spp.), the northern pocket gopher (Thomomys talpoidest. and the red squirrel (Tamiasciurus hudsonicus) cause serious damage to forest plantations and stands (and voles and pocket gophers in tree fruit orchards) by their feeding activities. Certain synthetic predator odors are reviewed which have produced significant avoidance responses in these pest species and reduced damage to crop trees on an experimental basis. In addition, the specific study reported in this paper was designed to assess the influence of predator odors on population density and survival of montane vole (M. montanus) populations in natural grassland habitat. Vole populations declined significantly in three consecutive winters on an area (and also on a replicated area in the third winter) treated with predator odors. These declines were caused by significantly lower survival in the treatment than control populations. Concurrent feeding damage to young apple trees was significantly reduced on the treatment area. We suggest that the predator odors may have attracted additional predators to the study area thereby increasing predation, as well as perhaps inducing behavioral-physiological stress in the vole populations. This technique could be implemented in forest plantations and tree fruit orchards as a means to disrupt resident vole populations and protect crop trees from damage