Population dynamics of kit foxes

1999 ◽  
Vol 77 (3) ◽  
pp. 486-493 ◽  
Author(s):  
P J White ◽  
Robert A Garrott
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Field Studies ◽  
High Amplitude ◽  
Short Term ◽  
Juvenile Mortality ◽  
Kit Fox ◽  
Fundamental Causes ◽  
Amplitude Fluctuations ◽  
Reproductive Rates

We evaluated data from field studies of kit foxes to identify factors that strongly influence or regulate their population dynamics. Two density-dependent regulating mechanisms were detected. First, the rate of juvenile recruitment was inversely related to the density of adult foxes because a higher proportion of juveniles were killed by coyotes at higher fox densities. The mortality rates of adult foxes were independent of population density. Second, populations of kit foxes are bounded by their territorial spacing behavior, which limits recruitment at high densities. These regulatory factors may operate in concert to curtail population growth at high densities, whereas decreased juvenile mortality by coyotes can operate independently to increase population growth at low densities. Despite the presence of these strong regulating factors, density-independent variations in reproductive rates often result in population crashes or irruptions that are the fundamental causes of instability in populations of kit foxes. Desert systems are characterized by unpredictable fluctuations in precipitation, which contribute to high-frequency, high-amplitude fluctuations in the abundance of mammalian prey (leporids, rodents) for kit foxes. These fluctuations subsequently contribute to density-independent variations in fox reproductive rates, which are strongly influenced by food supply. Projection models of a kit fox population showed that unpredictable, short-term fluctuations in precipitation and, in turn, prey abundance could generate longer term, aperiodic fluctuations in the density of foxes. Consequently, high amplitude fluctuations in the abundance of kit foxes may be intrinsic to the desert systems that they inhabit and need not reflect special or persistent causes such as predation or disease.

Factors regulating kit fox populations

1997 ◽  
Vol 75 (12) ◽  
pp. 1982-1988 ◽  
Author(s):  
P. J. White ◽  
Robert A. Garrott
Keyword(s):  
Population Dynamics ◽  
Interference Competition ◽  
Survival Rates ◽  
Prey Abundance ◽  
Short Term ◽  
Density Dependent ◽  
Kit Fox ◽  
Vulpes Macrotis ◽  
Predominant Factor ◽  
Major Factors

Recent declines in several populations of kit foxes (Vulpes macrotis) have been attributed to decreased prey abundance and increased coyote-related mortalities. However, it is not known if short-term fluctuations in prey abundance or interference competition by coyotes can regulate the population dynamics of kit foxes. We coalesced data from all pertinent studies of kit and swift foxes and examined their numerical responses to changes in prey abundance. We also explored the influence of coyote-related mortalities on fox population dynamics. Fox density was positively correlated with leporid abundance, and fox reproduction rates were density-dependent at low prey densities. The proportion of the fox population killed by coyotes increased linearly over low to moderate fox densities, and survival rates of adult foxes decreased as the proportion of mortalities caused by coyotes increased. Hence, prey abundance and interference competition by coyotes may regulate fox populations. We suspect that prey abundance, and behavioral spacing mechanisms, are the major factors regulating fox densities. Coyote-related mortalities may be a less predominant factor, but could still act in concert with prey abundance to reduce the amplitude of fox population dynamics and keep foxes at lower densities than they might otherwise attain.

scholarly journals Toward a New Cycle: Short-Term Population Dynamics, Gentrification, and Re-Urbanization of Milan (Italy)

2018 ◽  
Vol 10 (9) ◽  
pp. 3014 ◽  
Author(s):  
Margherita Carlucci ◽  
Francesco Chelli ◽  
Luca Salvati
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Population Decline ◽  
Population Expansion ◽  
Local Scale ◽  
City Centre ◽  
Short Term ◽  
Homogeneous Population ◽  
Scale Population ◽  
The City

After sequential cycles of urbanization and suburbanization, European cities underwent a (more or less intense) re-urbanization wave. The present study analyzes short-term population dynamics in the core of a large metropolitan region (Milan, northern Italy), providing evidence of spatially-heterogeneous re-urbanization characterized by spatially-complex population growth (or shrinkage) at a local scale. Population dynamics over 1999–2017 were assessed in 88 urban districts partitioning Milan′s municipal area and projected up to 2036 for the same spatial units. Empirical results identify spatially-complex and temporally non-linear dynamics with expanding or declining districts distributed heterogeneously across the study area. Multivariate analysis outlines a generalized population decline during 1999–2008 and an opposite pattern afterward (2008–2017), with spatially-homogeneous population expansion expected in the near future. Spatial analysis finally highlights that local-scale population growth rates were more clustered in 2008–2017 than in 1999–2008. While the population decreased continuously in the inner districts (<1 km from the city centre), sub-central districts (1–5 km far from the city centre) experienced mixed patterns of population growth and stability. These results confirm the relevance of local-scale policies managing urban renewal and rehabilitation and promoting metropolitan expansion in a spatially-coordinated manner.

scholarly journals Skewed distributions of LRS: beyond mean and variance

2019 ◽  
Author(s):  
Shripad Tuljapurkar ◽  
Wenyun Zuo ◽  
Tim Coulson ◽  
Carol Horvitz ◽  
Jean-Michel Gaillard
Keyword(s):  
Life History ◽  
Reproductive Success ◽  
Population Growth ◽  
Life History Evolution ◽  
Field Studies ◽  
Lifetime Reproductive Success ◽  
Skewed Distributions ◽  
Mean And Variance ◽  
Signatures Of Selection ◽  
Reproductive Rates

AbstractMany field studies find that lifetime reproductive success (LRS) is highly skewed and often multimodal among individuals. Field biologists generate invaluable data on survival and reproductive rates, as a function of age and stage, that are used to parameterise structured models. These models often perform well at predicting population growth and mean LRS, but we do not know whether they accurately predict observed distributions of individual LRS. If the models fail to recreate these distributions, their use may be limited because the LRS is central to understanding life history evolution. We present powerful tools to generate distributions of LRS from age and/or stage structured models. Our methods reveal that structured models do perform well at generating distributions that agree with observations. Our approach also reveals why such skewed distributions arise, and helps resolve a debate about detecting signatures of selection in skewed distributions of LRS.

Transient population dynamics drive the spread of invasive wild pigs in North America

2021 ◽  
Author(s):  
Ryan S Miller ◽  
Michael Tabak ◽  
Christopher L Burdett ◽  
David W Wolfson
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
North America ◽  
Population Growth ◽  
Population Growth Rate ◽  
Spatial Models ◽  
Initial Population ◽  
Short Term ◽  
Wild Pigs ◽  
Transient Population

Invasion of nonindigenous species is considered one of the most urgent problems affecting native ecosystems and agricultural systems. Mechanistic models that account for short-term population dynamics can improve prediction because they incorporate differing demographic processes that link the environmental conditions of a spatial location explicitly with the invasion process. Yet short-term population dynamics are rarely accounted for in spatial models of invasive species spread. Accounting for transient population dynamics, we predict the population growth rate and establishment probability of wild pigs following introduction into any location in North America. We compared predicted population growth rate with observed geographic rates of spread and found significant relationships between the annual rate of spread and population growth rates. We used geospatial data on the distribution of mast producing tree species (a principle forage resource of wild pigs) and agricultural crops that can replace mast in their diets to predict population dynamics using transient population simulations. We simulated populations under different initial population sizes (i.e. number of introduced individuals, often termed propagule size) and for different amounts of time following introduction. By varying the initial population size and simulation time, we were able to identify areas in North America with high probability for establishment of wild pigs if introduced. Our findings can be used to inform surveillance and removal efforts to reduce the potential for establishment and spread of wild pigs.

scholarly journals Subway Gearbox Fault Diagnosis Algorithm Based on Adaptive Spline Impact Suppression

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 660
Author(s):  
Zhongshuo Hu ◽  
Jianwei Yang ◽  
Dechen Yao ◽  
Jinhai Wang ◽  
Yongliang Bai
Keyword(s):  
Fault Diagnosis ◽  
Spline Interpolation ◽  
Reference Value ◽  
High Amplitude ◽  
Engineering Practice ◽  
Negative Effects ◽  
Short Term ◽  
Time Domain Signal ◽  
Gearbox Vibration ◽  
Long Time

In the signal processing of real subway vehicles, impacts between wheelsets and rail joint gaps have significant negative effects on the spectrum. This introduces great difficulties for the fault diagnosis of gearboxes. To solve this problem, this paper proposes an adaptive time-domain signal segmentation method that envelopes the original signal using a cubic spline interpolation. The peak values of the rail joint gap impacts are extracted to realize the adaptive segmentation of gearbox fault signals when the vehicle was moving at a uniform speed. A long-time and unsteady signal affected by wheel–rail impacts is segmented into multiple short-term, steady-state signals, which can suppress the high amplitude of the shock response signal. Finally, on this basis, multiple short-term sample signals are analyzed by time- and frequency-domain analyses and compared with the nonfaulty results. The results showed that the method can efficiently suppress the high-amplitude components of subway gearbox vibration signals and effectively extract the characteristics of weak faults due to uniform wear of the gearbox in the time and frequency domains. This provides reference value for the gearbox fault diagnosis in engineering practice.

scholarly journals Human trampling as short-term disturbance on intertidal mudflats: effects on macrofauna biodiversity and population dynamics of bivalves

2007 ◽  
Vol 151 (6) ◽  
pp. 2077-2090 ◽  
Author(s):  
F. Rossi ◽  
R. M. Forster ◽  
F. Montserrat ◽  
M. Ponti ◽  
A. Terlizzi ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Short Term ◽  
Intertidal Mudflats ◽  
Human Trampling

scholarly journals Quantifying the effect of genetic, environmental and individual demographic stochastic variability for population dynamics in Plantago lanceolata

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ulrich K. Steiner ◽  
Shripad Tuljapurkar ◽  
Deborah A. Roach
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Population Change ◽  
Adaptive Dynamics ◽  
Plantago Lanceolata ◽  
Environmental Parameters ◽  
Experimental Population ◽  
Stochastic Variation ◽  
Survival And Reproduction ◽  
Stochastic Events

AbstractSimple demographic events, the survival and reproduction of individuals, drive population dynamics. These demographic events are influenced by genetic and environmental parameters, and are the focus of many evolutionary and ecological investigations that aim to predict and understand population change. However, such a focus often neglects the stochastic events that individuals experience throughout their lives. These stochastic events also influence survival and reproduction and thereby evolutionary and ecological dynamics. Here, we illustrate the influence of such non-selective demographic variability on population dynamics using population projection models of an experimental population of Plantago lanceolata. Our analysis shows that the variability in survival and reproduction among individuals is largely due to demographic stochastic variation with only modest effects of differences in environment, genes, and their interaction. Common expectations of population growth, based on expected lifetime reproduction and generation time, can be misleading when demographic stochastic variation is large. Large demographic stochastic variation exhibited within genotypes can lower population growth and slow evolutionary adaptive dynamics. Our results accompany recent investigations that call for more focus on stochastic variation in fitness components, such as survival, reproduction, and functional traits, rather than dismissal of this variation as uninformative noise.

The effects of Velpar L (hexazinone) on seedling growth and ectomycorrhizal symbiosis of Pinusresinosa

1988 ◽  
Vol 18 (7) ◽  
pp. 917-921 ◽  
Author(s):  
P. Chakravarty ◽  
L. Chatarpaul
Keyword(s):  
Seedling Growth ◽  
Field Studies ◽  
Indigenous Species ◽  
Mycorrhizal Infection ◽  
Infection Rates ◽  
Seedling Mortality ◽  
Short Term ◽  
Ectomycorrhizal Symbiosis ◽  
Significant Recovery ◽  
Application Rates

We investigated the effects of Velpar L (hexazinone) on ectomycorrhizal (Laccarialaccata) and nonmycorrhizal Pinusresinosa seedlings in the greenhouse and in the field. In both greenhouse and field studies, seedling growth was reduced by Velpar L at 1, 2, and 4 kg/ha application rates in the short term (2 months' exposure) with significant recovery occurring afterwards. Seedling mortality occurred only with herbicide treatments and was higher in the greenhouse than in the field. The 4 kg/ha Velpar L treatment caused the highest mortality and toxicity was most pronounced in the mycorrhizal (Laccarialaccata inoculated) seedlings. In both experiments mycorrhizal infection was significantly reduced by 2 and 4 kg/ha Velpar L treatments during the 0- to 2-month and 2- to 6-month exposure periods, with significant recovery occurring in the latter. Although seedlings not infected with Laccarialaccata became mycorrhizal through unidentified indigenous species, their infection rates were also affected by Velpar L at all levels during the 0- to 2-month period and at the 2 and 4 kg/ha levels after 2–6 months of exposure to the herbicide.

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