scholarly journals The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears

2015 ◽  
Vol 282 (1798) ◽  
pp. 20141840 ◽  
Author(s):  
Jacinthe Gosselin ◽  
Andreas Zedrosser ◽  
Jon E. Swenson ◽  
Fanie Pelletier
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Indirect Effects ◽  
Ursus Arctos ◽  
Brown Bear ◽  
Relative Importance ◽  
Direct And Indirect Effects ◽  
Negative Effects ◽  
Hunting Pressure ◽  
Demographic Rates

There is increasing evidence of indirect effects of hunting on populations. In species with sexually selected infanticide (SSI), hunting may decrease juvenile survival by increasing male turnover. We aimed to evaluate the relative importance of direct and indirect effects of hunting via SSI on the population dynamics of the Scandinavian brown bear ( Ursus arctos ). We performed prospective and retrospective demographic perturbation analyses for periods with low and high hunting pressures. All demographic rates, except yearling survival, were lower under high hunting pressure, which led to a decline in population growth under high hunting pressure ( λ = 0.975; 95% CI = 0.914–1.011). Hunting had negative indirect effects on the population through an increase in SSI, which lowered cub survival and possibly also fecundity rates. Our study suggests that SSI could explain 13.6% of the variation in population growth. Hunting also affected the relative importance of survival and fecundity of adult females for population growth, with fecundity being more important under low hunting pressure and survival more important under high hunting pressure. Our study sheds light on the importance of direct and indirect effects of hunting on population dynamics, and supports the contention that hunting can have indirect negative effects on populations through SSI.

Catastrophes, disturbances and density-dependence: population dynamics of the spiny pocket mouse (Heteromys desmarestianus) in a neotropical lowland forest

2007 ◽  
Vol 23 (5) ◽  
pp. 507-518 ◽  
Author(s):  
Rob Klinger
Keyword(s):  
Population Dynamics ◽  
Indirect Effects ◽  
Juvenile Survival ◽  
Direct And Indirect Effects ◽  
Direct Effects ◽  
Lowland Forest ◽  
Density Dependent ◽  
Demographic Rates ◽  
Independent Events ◽  
Pocket Mouse

Capture–mark–recapture methods were used to study the influence of density-dependent and density-independent factors on population dynamics of the spiny pocket mouse Heteromys desmarestianus in a lowland forest in Belize. Fourteen trapping sessions were conducted in six 0.5-ha grids at irregular intervals from July 2000 to March 2005. Responses by H. desmarestianus to four disturbance events depended on the type and magnitude of the events. Although fluctuations in density were strongly related to fruit availability, the disturbances tended to magnify direct and delayed density-dependent effects on reproduction and juvenile survival. A catastrophic flood in July 2000 eliminated the entire population, but by September 2001 population density had increased from 34.4 individuals ha−1 immediately pre-flood to 42.5 individuals ha−1. Indirect effects from a hurricane in October 2001 had greater and longer lasting influences on demographic rates than direct effects from less severe floods in August 2002 and September 2003. Fruiting ceased for almost 2.5 y after the hurricane, resulting in extremely low juvenile survival and a decline in density from 46.8 individuals ha−1 in January 2002 to 23.0 individuals ha−1 in January 2004. Fruiting began again in January 2004, and after several subsequent pulses of reproduction and generally higher rates of juvenile survival the population reached a maximum of 77.3 individuals ha−1 in March 2005. Inferences from the study, especially on the duration of delayed-density-dependent effects, must be made cautiously because of the irregular trapping intervals resulting from the unplanned disturbances. However, the results indicate that population dynamics of many tropical small-mammal populations will be driven by direct and indirect effects from density-independent events that amplify density-dependent influences on demographic rates.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

Effects of Grit on the Academic Success of Adult Female Students at Korean Open University

2017 ◽  
Vol 121 (4) ◽  
pp. 705-725 ◽  
Author(s):  
Mae Hyang Hwang ◽  
Hyo Jin Lim ◽  
Hye Suk Ha
Keyword(s):  
Academic Success ◽  
Grade Point Average ◽  
Indirect Effects ◽  
School Success ◽  
Female Students ◽  
Self Control ◽  
Open University ◽  
Direct And Indirect Effects ◽  
Negative Effects ◽  
Grade Point

This study examined the structural relationship between age, grit (i.e., perseverance of effort and consistency of interest), conscientiousness, self-control, and school success of female students at an Open University in Korea. We analyzed 509 students’ responses, and it turned out that the level of perseverance of effort was negatively correlated with academic maladjustment. Also, perseverance of effort had a positive indirect effect on grade point average scores. Conscientiousness and self-control were found to be positively correlated with grit factors and they had negative effects on academic maladjustment through perseverance of effort. Age had both direct and indirect effects on grit and academic success of the students.

scholarly journals Decomposing variation in population growth into contributions from environment and phenotypes in an age-structured population

2011 ◽  
Vol 279 (1727) ◽  
pp. 394-401 ◽  
Author(s):  
Fanie Pelletier ◽  
Kelly Moyes ◽  
Tim H. Clutton-Brock ◽  
Tim Coulson
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Age Structure ◽  
Life History Traits ◽  
Population Fluctuations ◽  
Relative Importance ◽  
Ecological Interactions ◽  
Structured Population ◽  
Individual Covariates ◽  
Age Structured

Evaluating the relative importance of ecological drivers responsible for natural population fluctuations in size is challenging. Longitudinal studies where most individuals are monitored from birth to death and where environmental conditions are known provide a valuable resource to characterize complex ecological interactions. We used a recently developed approach to decompose the observed fluctuation in population growth of the red deer population on the Isle of Rum into contributions from climate, density and their interaction and to quantify their relative importance. We also quantified the contribution of individual covariates, including phenotypic and life-history traits, to population growth. Fluctuations in composition in age and sex classes ((st)age structure) of the population contributed substantially to the population dynamics. Density, climate, birth weight and reproductive status contributed less and approximately equally to the population growth. Our results support the contention that fluctuations in the population's (st)age structure have important consequences for population dynamics and underline the importance of including information on population composition to understand the effect of human-driven changes on population performance of long-lived species.

scholarly journals Allelopathic interactions between the macrophyte Egeria densa and plankton (alga, Scenedesmus acutus and cladocerans, Simocephalus spp.): a laboratory study

2016 ◽  
Vol 75 (s1) ◽  
Author(s):  
Cristian A. Espinosa-Rodríguez ◽  
Ligia Rivera-De la Parra ◽  
Aurora Martínez-Téllez ◽  
Gisela C. Gómez-Cabral ◽  
S.S.S. Sarma ◽  
...  
Keyword(s):  
Population Growth ◽  
Conditioned Medium ◽  
Indirect Effects ◽  
Population Increase ◽  
Life History Strategies ◽  
Direct And Indirect Effects ◽  
Egeria Densa ◽  
Scenedesmus Acutus ◽  
Cladoceran Species ◽  
Allelopathic Interactions

<p>Allelopathic interactions between macrophytes and zooplankton are important to understand the plankton dynamics in shallow waterbodies. <em>Egeria densa</em> is a native, perennial, submerged macrophyte in the tropical and subtropical zones of South America. It has been introduced to Central and North America and is now common in many Mexican lakes. This macrophyte produces chemical substances that negatively affect some phytoplankton species. However, it is not clear how zooplankton species adapt different life history strategies in the chemical presence of this macrophyte. Here, we tested the direct and indirect effects of allelochemicals released by <em>E. densa</em> on the population growth of <em>Scenedesmus acutus</em> and on the demographic variables of three species of <em>Simocephalus</em>, <em>S. exspinosus</em>, <em>S. serrulatus</em> and <em>S. mixtus</em> (via alga exposed to the macrophyte allelochemicals). To quantify the effect of <em>E. densa</em> on <em>S. acutus</em> we set up four treatments: control, artificial <em>Egeria</em>, natural <em>Egeria</em> and allelochemicals from <em>Egeria</em>. To test the allelochemical effects on <em>Simocephalus</em> species, we compared four treatments: Control, indirect effect (using <em>S. acutus</em> grown on <em>Egeria</em>-allelochemicals), direct effect (using <em>Egeria</em>-conditioned medium) and together with both these kinds of direct and indirect effects. <em>Scenedesmus </em>had the highest cell density in the presence of allelochemicals from <em>Egeria</em>, followed by controls. The specific algal growth rate (µ) between control and allelochemicals treatment was not significant (P&lt;0.05). However, the µ of alga in the presence of artificial or natural <em>Egeria</em> was significantly lower than controls or in treatment involving allelochemicals. The age-specific survivorship of the three cladoceran species was longer in treatments containing <em>Egeria</em>-conditioned medium. Cladocerans receiving <em>Egeria</em> conditioned-medium and algae cultured on macrophyte-allelochemicals also had a longer survivorship. Daily fecundity of <em>S. serrulatus</em> increased after reaching mid-age while <em>S. expinosus </em>and <em>S. mixtus</em> showed continuous reproduction starting from the first week. In general, <em>Egeria</em>-allelochemicals enhanced the age-specific reproductive output for all the three cladoceran species. The average lifespan of the three <em>Simocephalus </em>varied from 17 to 46 days, depending on the cladoceran species and treatment. <em>S. serrulatus </em>had lower lifespan compared to other two cladoceran species. For the three species, lifespan significantly increased in treatments containing macrophyte-conditioned medium + algae grown on the plant-allelochemicals; also under these conditions, both gross and net reproductive rates were significantly enhanced. This stimulatory effect was also evident in generation time (about 50% higher). The rate of population increase ranged from 0.23 to 0.38 per day for the three tested <em>Simocephalus</em> species but there were no significant differences (P˃0.05) among treatments. Our results suggest that the biological activity as well as physical structure of <em>E. densa</em> had negative effects on <em>S. acutus</em> population growth but had stimulatory effects on the demography of <em>Simocephalus</em>. </p>

Sign in / Sign up

Export Citation Format

Share Document