scholarly journals Detecting and modelling delayed density-dependence in abundance time series of a small mammal (Didelphis aurita)

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
E. Brigatti ◽  
M. V. Vieira ◽  
M. Kajin ◽  
P. J. A. L. Almeida ◽  
M. A. de Menezes ◽  
...  
Keyword(s):  
Time Series ◽  
Density Dependence ◽  
Small Mammal ◽  
Delayed Density Dependence ◽  
Didelphis Aurita

Ecological change points: The strength of density dependence and the loss of history

2017 ◽  
Author(s):  
José M. Ponciano ◽  
Mark L. Taper ◽  
Brian Dennis
Keyword(s):  
Time Series ◽  
Population Dynamics ◽  
Density Dependence ◽  
Change Point ◽  
Likelihood Estimation ◽  
Theory And Practice ◽  
Change Points ◽  
Ecological Change ◽  
Proposed Model ◽  
Change Point Model

AbstractChange points in the dynamics of animal abundances have extensively been recorded in historical time series records. Little attention has been paid to the theoretical dynamic consequences of such change-points. Here we propose a change-point model of stochastic population dynamics. This investigation embodies a shift of attention from the problem of detecting when a change will occur, to another non-trivial puzzle: using ecological theory to understand and predict the post-breakpoint behavior of the population dynamics. The proposed model and the explicit expressions derived here predict and quantify how density dependence modulates the influence of the pre-breakpoint parameters into the post-breakpoint dynamics. Time series transitioning from one stationary distribution to another contain information about where the process was before the change-point, where is it heading and how long it will take to transition, and here this information is explicitly stated. Importantly, our results provide a direct connection of the strength of density dependence with theoretical properties of dynamic systems, such as the concept of resilience. Finally, we illustrate how to harness such information through maximum likelihood estimation for state-space models, and test the model robustness to widely different forms of compensatory dynamics. The model can be used to estimate important quantities in the theory and practice of population recovery.

Geographic variation in population cycles of Canadian muskrats (Ondatra zibethicus)

2000 ◽  
Vol 78 (6) ◽  
pp. 1009-1016 ◽  
Author(s):  
John Erb ◽  
Nils Chr. Stenseth ◽  
Mark S Boyce
Keyword(s):  
Density Dependence ◽  
Trophic Interactions ◽  
Dynamic Properties ◽  
Population Cycles ◽  
Period Length ◽  
Ondatra Zibethicus ◽  
Delayed Density Dependence ◽  
Relative Contribution ◽  
Arctic Regions ◽  
Harvest Data

We investigated the dynamic properties of population cycles in Canadian muskrats (Ondatra zibethicus). Ninety-one historic time series of muskrat-harvest data obtained from the Hudson's Bay Company Archives were analyzed. Most series were 25 years in length (1925–1949) and were distributed primarily throughout five ecozones. For each series, we estimated period length and coefficients for a second-order autoregressive model. Estimated period length varied between 3 and 13 years, with 3- to 5-year periods located in Subarctic-Arctic ecozones. We hypothesize that the 4-year cycles are largely a result of predation by red fox (Vulpes vulpes), which exhibit 4-year cycles in Arctic regions. The remaining ecozones generally averaged 8–9 years in period length. However, the relative contributions of direct and delayed density dependence varied along a latitudinal gradient. We hypothesize that both social and trophic interactions are necessary to produce the observed dynamics, but that shifts in the nature of mink predation were responsible for the changes in the relative contribution of direct and delayed density dependence. Essentially, there is a tension between population-intrinsic and trophic interactions that may bound the length of the cycle.

Population decline in semi-migratory caribou (Rangifer tarandus): intrinsic or extrinsic drivers?

2013 ◽  
Vol 91 (11) ◽  
pp. 820-828 ◽  
Author(s):  
Guillaume Bastille-Rousseau ◽  
James A. Schaefer ◽  
Shane P. Mahoney ◽  
Dennis L. Murray
Keyword(s):  
Density Dependence ◽  
Rangifer Tarandus ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Population Decline ◽  
Negative Relationship ◽  
Population Limitation ◽  
Continental Scale ◽  
Delayed Density Dependence ◽  
Winter Severity

Many populations of caribou (Rangifer tarandus (L., 1758)) across North America, including Newfoundland, are in a state of decline. This phenomenon may reflect continental-scale changes in either the extrinsic or the intrinsic factors affecting caribou abundance. We hypothesized that caribou decline reflected marked resource limitation and predicted that fluctuations should correspond to time-delayed density dependence associated with a decline in range quality and decadal trends in winter severity. By conducting time-series analysis using 12 populations and evaluating correlations between caribou abundance and trends in (i) vegetation available at calving (normalized difference vegetation index, NDVI), (ii) winter weather severity (index of North Atlantic Oscillation, NAO), and (iii) caribou morphometrics, we observed strong evidence of density dependence in population dynamics (i.e., a negative relationship between caribou population size and caribou morphometrics). Caribou population trajectories were time-delayed relative to winter severity, but not relative to calving-ground greenness. These island-wide correlations could not be traced to dispersal between herds, which appears rare at least for adult females. Our results suggest that trends in winter severity may synchronize broad-scale changes in caribou abundance that are driven by time-delayed density dependence, although it remains possible that calving-ground deterioration also may contribute to population limitation in Newfoundland. Our findings provide the basis for additional research into density dependence and caribou population decline.

scholarly journals Simple dynamics underlie sockeye salmon (Oncorhynchus nerka) cycles

1998 ◽  
Vol 55 (10) ◽  
pp. 2355-2364 ◽  
Author(s):  
Ransom A Myers ◽  
Gordon Mertz ◽  
Jessica M Bridson ◽  
Michael J Bradford
Keyword(s):  
British Columbia ◽  
Density Dependence ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Stochastic Forcing ◽  
Stable Mode ◽  
Delayed Density Dependence ◽  
Cyclic Patterns ◽  
Ricker Model ◽  
Parameter Values

A variety of mechanisms have been proposed to explain the renowned British Columbia sockeye salmon (Oncorhynchus nerka) cycles, most of which invoke between-brood interactions (delayed density dependence) or depensatory harvest practices. We examine the dynamics of the Ricker model with realistic parameter values and suggest that the cycles could result from a stable mode excited by stochastic forcing. The previously proposed mechanisms are not required to generate cyclic patterns, although they could play a role in reinforcing cycles. Our results suggest that relaxing harvest rates will increase yields and decrease variability in sockeye abundances.

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