The influence of food resources on population dynamics in Columbian ground squirrels

1985 ◽  
Vol 63 (9) ◽  
pp. 2095-2104 ◽  
Author(s):  
F. Stephen Dobson ◽  
Julia D. Kjelgaard
Keyword(s):  
Population Dynamics ◽  
Environmental Factors ◽  
Population Size ◽  
Ground Squirrel ◽  
Food Resources ◽  
Ground Squirrels ◽  
Limiting Factors ◽  
Supplemental Food ◽  
Survival And Reproduction ◽  
Population Processes

Determining the environmental factors that limit the size of populations and examining the influence of environmental factors on population processes (immigration, emigration, survival, and reproduction) are fundamental problems for population ecologists. We conducted an experimental study of population dynamics in the Columbian ground squirrel, Spermophilus columbianus, from 1981 to 1983, in southwestern Alberta, Canada. We supplemented the food resources of two local populations of ground squirrels at different elevations and also monitored two reference (unsupplemented) populations. Population size increased by about 85% annually and population biomass increased by about 94% annually where supplemental food was provided. Reference populations varied in numbers and biomass by less than 40% annually. Because the increase in size of supplemented populations was dramatic, we concluded that food resources probably limited the size of the ground squirrel populations before we began the experiments and that other possible limiting factors were insufficient to check the increases stimulated by supplemental food. Several population processes were influenced by the increased food resources. Immigration of all age-classes was higher to supplemented than to reference populations and favored females. Survival of resident young was higher in supplemented than in reference populations. Reproduction was greatly increased in supplemented populations compared with reference populations, with surviving young residents of 1982 making the greatest contribution to increases in population size. The results were generally similar in the two replicates of the experiment. Competition for food resources appeared to be strongest among yearling and adult females and among young of both sexes.

Effective population size and genetic structure of a Piute ground squirrel (Spermophilus mollis) population

2001 ◽  
Vol 79 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Michael F Antolin ◽  
Beatrice Van Horne ◽  
Michael D Berger, Jr. ◽  
Alisha K Holloway ◽  
Jennifer L Roach ◽  
...  
Keyword(s):  
Genetic Analysis ◽  
Population Size ◽  
Effective Population Size ◽  
Ground Squirrel ◽  
Population Genetic ◽  
Ground Squirrels ◽  
Perennial Grasses ◽  
Population Subdivision ◽  
Effective Population ◽  
Population Genetic Analysis

Piute ground squirrels (Spermophilus mollis) are distributed continuously in habitat dominated by native shrubs and perennial grasses in the Snake River Birds of Prey National Conservation Area in Idaho, U.S.A. This habitat is being fragmented and replaced by exotic annual plants, changing it to a wildfire-dominated system that provides poor habitat for ground squirrels. To assess potential effects of this fragmentation on ground squirrel populations, we combined an estimate of effective population size (Ne) based upon a demographic study with a population genetic analysis. The study area included three subpopulations separated from each other by 8–13 km. The ratio of effective population size to census number (Ne/N) was 0.57. Combining Ne/N with dispersal distances from a radio-tracking study, we calculated that neighborhood size was 62.2 ha, which included between 204 and 480 individuals. Our population genetic analysis (based on randomly amplified polymorphic DNA (RAPD) and microsatellite markers) showed relatively low levels of genetic differentiation (Qpopulations [Formula: see text] 0.07–0.10) between subpopulations and no inbreeding within subpopulations (f = 0.0003). These estimates of population subdivision translate into an effective migration rate (Nem) of 2.3–3.3 per year, which represents a high level of gene flow. Invasion by exotics will reduce the overall productivity of the habitat, and will lead to isolation among subpopulations if favorable habitat patches become isolated.

Temperature and the Regulation of Enzyme Activity in the Hibernator. Isoenzymes of Liver Pyruvate Kinase from the Hibernating and Non-hibernating Arctic Ground Squirrel

1974 ◽  
Vol 52 (10) ◽  
pp. 894-902 ◽  
Author(s):  
Hans W. Behrisch
Keyword(s):  
Molecular Weight ◽  
Pyruvate Kinase ◽  
Wide Temperature Range ◽  
Ground Squirrel ◽  
Energy Charge ◽  
High Energy ◽  
Ground Squirrels ◽  
The Arctic ◽  
Arctic Ground Squirrel ◽  
Temperature Range

Liver of the hibernating (H) Arctic ground squirrel (Citellus undulatus) contains a single species of pyruvate kinase (PyK) that is distinct from the single isoenzyme of pyK observed in the non-hibernating (NH) ground squirrel, which has been previously described (Behrisch &Johnson (1974) Can. J. Biochem. 52, 547–559). The H-PyK has a pI value of 5.7 and a molecular weight of 241 000 – 243 000. Affinity of the H-PyK for the substrates phosphoenolpyruvate (PEP) and ADP is not affected by changing temperature. It is argued that this stability of the apparent Km's for substrate over a wide temperature range permits the hibernator to take advantage of the Q10 effect in maintaining a low rate of the PyK reaction. Similarly, affinity of H-PyK for the allosteric activator fructose-1,6-phosphate (FDP) and the inhibitor ATP is also conspicuously independent of temperature, suggesting a fine stoichiometry in the relative concentrations of the regulatory ligands in control of H-PyK over a wide temperature range. Further, affinity of H-PyK for the inhibitor ATP is about three- to fourfold lower than that of the NH-PyK, a condition that would favor the maintenance of a high energy charge in the hibernating liver cell. ATP apparently inhibits PyK by causing a dissociation of the enzyme molecule into two "halves" of about 110 000 molecular weight each. This dissociation is offset and reversed by FDP. Removal of the ATP by dialysis does not of itself result in a reassociation of the PyK "halves"; FDP and/or the substrates are required for the two subunits of PyK to reassociate. As the apparent Ki of H-PyK for ATP is higher than that of NH-PyK, substantially higher concentrations of ATP are required to effect the dissociation of H-PyK. Similarly, elevated concentrations of FDP are required to offset the ATP-caused dissociation of the H-PyK.Hibernating Arctic ground squirrels that are preparing to emerge finally from the hibernating state already possess substantial activities of the NH-PyK isoenzyme. This suggests that the animal "anticipates" its transition from one metabolic state from another. On the basis of these data a formal mechanism is proposed for the regulation of liver PyK in the Arctic ground squirrel in both the non-hibernating and hibernating states.

Estimation of Catchabilities and Population Sizes of Lobsters

1963 ◽  
Vol 20 (1) ◽  
pp. 59-88 ◽  
Author(s):  
J. E. Paloheimo
Keyword(s):  
Environmental Factors ◽  
Population Size ◽  
Atlantic Coast ◽  
Temperature Data ◽  
New Method ◽  
Bottom Temperature ◽  
Population Size Estimates ◽  
Population Sizes ◽  
Estimate Population Size ◽  
Size Estimates

Techniques of estimating population size, level of fishing, and the degree of dependence of fishing success on environmental factors are examined on the basis of tagging, catch and effort data. A new method is developed to estimate population size from catch, effort, and temperature data when the catchability varies with temperature.The methods of estimation discussed are applied to data collected from a number of lobster fisheries on Canada's Atlantic coast. Analysis confirms a relationship between the catchability of lobsters and bottom temperature. Differences in this relationship are found between areas and between tagged and untagged lobsters within areas. It is suggested that these differences are attributable to the differences in densities as well as to aggregations of lobsters and fishing. The effect of these aggregations on population size estimates is considered.Calculated average catchabilities at comparable temperatures are different for different areas. These differences are correlated with the numbers of trap hauls per day per square miles fished. It is suggested that the differences in the catchabilities might be due to interactions between units of gear not predicted by the customary relationship between catch and effort.

Survival and cause-specific mortality of the female eastern wild turkey at its northern range edge

2014 ◽  
Vol 41 (7) ◽  
pp. 545 ◽  
Author(s):  
Britney Niedzielski ◽  
Jeff Bowman
Keyword(s):  
Management Strategies ◽  
Meleagris Gallopavo ◽  
Limiting Factors ◽  
Wild Turkey ◽  
High Productivity ◽  
Supplemental Food ◽  
Range Edge ◽  
The North ◽  
Wild Turkeys ◽  
Peripheral Areas

Context In an era of rapid environmental change, many species are shifting their distributions. As temperate-zone species’ expand their ranges north, different and potentially severe limiting factors may begin to affect their ability to survive and reproduce. The wild turkey (Meleagris gallopavo) is one example of a species undergoing rapid northern expansion. Aims An improved understanding of wild turkey demography at the species’ northern range periphery would facilitate effective management of this important game species. Therefore, we undertook a study to evaluate survival, causes of mortality, and behavioural strategies that may govern survival of female wild turkeys. Methods We captured 53 female wild turkeys, and used backpack transmitters to monitor their individual fates during 2012–13. Key results The annual survival estimate was 0.37 (95% CI: 0.25–0.55), with the lowest seasonal survival in the winter. The most frequent cause of mortality was mammalian predation, predominately by coyotes (Canis latrans). Age, proximity to supplemental food, and habitat use did not affect risk of mortality. Conclusions Northern wild turkeys in our study exhibited lower survival and suffered higher predation than did populations in the species’ historic range. Despite our findings, the wild turkey has expanded its range northwards and continues to exist in these peripheral areas. This may be due to high productivity or a source–sink dynamic, whereby high mortality is offset by immigration from the south. Implications The low survival and high predation of wild turkeys in the north must be considered when developing management strategies, particularly if interest exists in translocating turkeys farther north. Further research is needed to better understand whether northern turkey populations persist as sinks.

scholarly journals Population dynamics in northwestern China

2021 ◽  
Author(s):  
Xueyan Yang ◽  
Wanxin Li ◽  
Wen Jing ◽  
Chezhuo Gao ◽  
Rui Li ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Structure ◽  
Population Size ◽  
Ethnic Groups ◽  
Northwestern China ◽  
Average Level ◽  
Han Population ◽  
Sex Structure ◽  
Biological Sex

AbstractThis article analyzes the population dynamics in northwestern China from roughly 2010 to 2020. The area’s dynamics showed a slow, stable increase in population size, a stable increase in the population of non-Han ethnic groups, which increased at a more rapidly than the Han population, and population rejuvenation coupled with a population structure that aged. The biological sex structure fluctuated within a balanced range in northwestern China. Urbanization advanced in northwestern China, throughout this period, but the area’s level of urbanization is still significantly lower than the average level of urbanization nationally.

scholarly journals The influence of microhabitat on the population dynamics of four herbaceous species in a semiarid area of northeastern Brazil

2016 ◽  
Vol 76 (1) ◽  
pp. 45-54 ◽  
Author(s):  
K. A. Silva ◽  
J. M. F. F. Santos ◽  
J. R. Andrade ◽  
E. N. Lima ◽  
U. P. Albuquerque ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Size ◽  
Mortality Rates ◽  
Dry Forest ◽  
Northeastern Brazil ◽  
Annual Rainfall ◽  
Herbaceous Species ◽  
Forest Fragment ◽  
Experimental Station ◽  
Over Time

Abstract Variation in annual rainfall is considered the most important factor influencing population dynamics in dry environments. However, different factors may control population dynamics in different microhabitats. This study recognizes that microhabitat variation may attenuate the influence of climatic seasonality on the population dynamics of herbaceous species in dry forest (Caatinga) areas of Brazil. We evaluated the influence of three microhabitats (flat, rocky and riparian) on the population dynamics of four herbaceous species (Delilia biflora, Commelina obliqua, Phaseolus peduncularis and Euphorbia heterophylla) in a Caatinga (dry forest) fragment at the Experimental Station of the Agronomic Research Institute of Pernambuco in Brazil, over a period of three years. D. biflora, C. obliqua and P. peduncularis were found in all microhabitats, but they were present at low densities in the riparian microhabitat. There was no record of E. heterophylla in the riparian microhabitat. Population size, mortality rates and natality rates varied over time in each microhabitat. This study indicates that different establishment conditions influenced the population size and occurrence of the four species, and it confirms that microhabitat can attenuate the effect of drought stress on mortality during the dry season, but the strength of this attenuator role may vary with time and species.

scholarly journals Population parameters and the relationships between environmental factors and abundance of the Acetes americanus shrimp (Dendrobranchiata: Sergestidae) near a coastal upwelling region of Brazil

2015 ◽  
Vol 63 (3) ◽  
pp. 229-238
Author(s):  
Ana Paula Freitas dos Santos ◽  
Sabrina Morilhas Simões ◽  
Gabriel Lucas Bochini ◽  
Cinthia Helena Costa ◽  
Rogerio Caetano da Costa
Keyword(s):  
Population Dynamics ◽  
Sexual Dimorphism ◽  
Environmental Factors ◽  
Primary Productivity ◽  
Low Temperatures ◽  
Coastal Upwelling ◽  
Statistical Correlation ◽  
Individual Growth ◽  
Otter Trawl ◽  
Population Parameters

AbstractThe population dynamics of Acetes americanus was investigated, focusing on the sex ratio, individual growth, longevity, recruitment and relationship between abundance and environmental factors in the region of Macaé, strongly influenced by coastal upwelling. Otter trawl net samplings were performed from July 2010 to June 2011 at two points (5 m and 15 m). Nearly 19,500 specimens, predominantly females (77.15%), were captured. Their sizes, larger than that of males, indicated sexual dimorphism. Shrimps at lower latitudes present larger sizes and longer longevity than those from higher latitudes. This difference is probably due to low temperatures and high primary productivity. Though no statistical correlation was found between abundance and environmental factors, the species was more abundant in temperatures closer to 20.0º C and in months with high chlorophyll-a levels. Due to the peculiar characteristics of this region, A. americanusshowed greater differences in size and longevity than individuals sampled in other studies undertaken in the continental shelf of Southeast Brazil.

The population dynamics of aphids on fire weed: a comparison of local populations and metapopulations

1978 ◽  
Vol 56 (12) ◽  
pp. 2554-2564 ◽  
Author(s):  
John F. Addicott
Keyword(s):  
Population Dynamics ◽  
Spatial Heterogeneity ◽  
Rocky Mountains ◽  
Median Number ◽  
Marked Variation ◽  
High Frequencies ◽  
Local Populations ◽  
Epilobium Angustifolium ◽  
Population Processes ◽  
Different Levels

Local populations of four species of aphids (Macrosiphum Valerianae, Aphis varions, A. helianthi, and A. salicariae) occur on shoots of fireweed (Epilobium angustifolium) in the Rocky Mountains of Colorado, U.S.A. Through exhaustive and repeated nondestructive sampling of the local populations on over 3800 shoots of fireweed, information was obtained on the dynamics of both the local populations and the metapopulation of each species. The dynamics of the metapopulation were analyzed in terms of the frequency of shoots occupied by aphids and the median number of aphids per occupied shoot. There were significant differences between species in both parameters, but high densities were not necessarily accompanied by high frequencies. Local populations were initiated throughout the summer, and there was marked variation in the duration and size of these populations. Most populations lasted only a few weeks, but others lasted up to 14 weeks. This turnover of local populations within the metapopulation implies that local populations must be studied in order to understand the dynamics of the metapopulation. There is a discussion of the relationships between population processes occurring at different levels of spatial heterogeneity.

A comparative study of scent-gland location and related behaviour in some northwestern nearctic ground squirrel species (Sciuridae): an evolutionary approach

1976 ◽  
Vol 54 (8) ◽  
pp. 1294-1306 ◽  
Author(s):  
V. Keith Kivett ◽  
Jan O. Murie ◽  
André L. Steiner
Keyword(s):  
Ground Squirrel ◽  
Scent Marking ◽  
Ground Squirrels ◽  
Scent Gland ◽  
Anal Glands ◽  
Greeting Behavior ◽  
Mouth Corner ◽  
Northwestern North America ◽  
Gland Development ◽  
Dorsal Gland

Location and hisiology of integumentary glands were investigated in six species of ground squirrels of the genus Spermophilus found in northwestern North America; S. columbianus, S. undulatus, S. richardsonii, S. tridecemlineatus, S. lateralis, and S. franklinii. Among these species, glands in oral, dorsal, and anal regions were structurally similar. Locations of oral and anal glands were identical but location of individual glands in dorsal-gland fields varied considerably. Gland development was greater in S. columbianus and S. undulatus and least in S. franklinii. Active scent marking was most frequent and extensive in S. columbianus and S. undulatus, less frequent in S. lateralis and S. tridecemlineatus, and absent in S. franklinii. In most instances, greeting behavior (which is focused on the mouth-corner oral-gland area) and the degree of sociality paralleled levels of scent marking. A hypothetical scheme of development or scent marking in relation to habitat and social organization is presented. This scheme fits, in general, classical interpretations of phylogeny.

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