Influence of rainfall on population dynamics and survival of a threatened rodent (Pseudomys novaehollandiae) under a drying climate in coastal woodlands of south-eastern Australia

2017 ◽  
Vol 65 (1) ◽  
pp. 60 ◽  
Author(s):  
Mandy Lock ◽  
Barbara A. Wilson
Keyword(s):  
Population Dynamics ◽  
Population Decline ◽  
Resource Depletion ◽  
Mammal Species ◽  
Eastern Australia ◽  
Apparent Decrease ◽  
Mediterranean Systems ◽  
Precipitous Decline ◽  
Breeding Seasons ◽  
Successional Vegetation

In Mediterranean systems, such as south-east Australia, predictions of climate change including lower rainfall and extended drought, threaten vulnerable mammal species. We investigated the relationship between rainfall and population dynamics for a native rodent at risk of extinction, the New Holland mouse (Pseudomys novaehollandiae). In the eastern Otways, the species was significantly influenced by rainfall, exhibiting a population irruption (15–20 individuals ha–1) following six years of above-average rainfall and a precipitous decline to site extinction during subsequent drought. The decline was predominantly related to loss of adults before and during breeding seasons, together with an apparent decrease in juvenile survival. Population abundance was positively correlated with a rainfall lag of 0–9 months. We propose that the response of this omnivore to high rainfall was mediated through increased productivity and that rainfall decline resulted in resource depletion and population decline. Under a drying climate the direct impacts of rainfall decline will continue. However management of other threats may increase the species’ resilience. Burning to provide optimal successional vegetation, protection of refugia, and predator control are priorities. However, burning should be avoided during drought, as the likelihood of local extinctions is substantial.

scholarly journals Separating the effects of climate, bycatch, predation and harvesting on tītī (Ardenna grisea) population dynamics in New Zealand: A model-based assessment

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243794
Author(s):  
Sam McKechnie ◽  
David Fletcher ◽  
Jamie Newman ◽  
Corey Bragg ◽  
Peter W. Dillingham ◽  
...  
Keyword(s):  
Population Dynamics ◽  
New Zealand ◽  
Southern Oscillation ◽  
Population Decline ◽  
Management Strategies ◽  
Model Averaging ◽  
Adult Survival ◽  
Enso Events ◽  
Introduced Predators ◽  
Best Fitting

A suite of factors may have contributed to declines in the tītī (sooty shearwater; Ardenna grisea) population in the New Zealand region since at least the 1960s. Recent estimation of the magnitude of most sources of non-natural mortality has presented the opportunity to quantitatively assess the relative importance of these factors. We fit a range of population dynamics models to a time-series of relative abundance data from 1976 until 2005, with the various sources of mortality being modelled at the appropriate part of the life-cycle. We present estimates of effects obtained from the best-fitting model and using model averaging. The best-fitting models explained much of the variation in the abundance index when survival and fecundity were linked to the Southern Oscillation Index, with strong decreases in adult survival, juvenile survival and fecundity being related to El Niño-Southern Oscillation (ENSO) events. Predation by introduced animals, harvesting by humans, and bycatch in fisheries also appear to have contributed to the population decline. It is envisioned that the best-fitting models will form the basis for quantitative assessments of competing management strategies. Our analysis suggests that sustainability of the New Zealand tītī population will be most influenced by climate, in particular by how climate change will affect the frequency and intensity of ENSO events in the future. Removal of the effects of both depredation by introduced predators and harvesting by humans is likely to have fewer benefits for the population than alleviating climate effects.

scholarly journals Social Upheaval, Poverty and the Latvian Demographic Crisis

2016 ◽  
Vol 50 ◽  
pp. 97-126
Author(s):  
Alfred Wong
Keyword(s):  
Death Rate ◽  
Birth Rate ◽  
Traumatic Event ◽  
Free Market ◽  
Population Decline ◽  
Physical And Mental Health ◽  
Political Event ◽  
Premature Deaths ◽  
High Death ◽  
Precipitous Decline

Latvia has been suffering a substantial decrease in population since the early 1990s. There appears to have been little or no detailed analysis of the genesis of this decline in population. The major political event occurring at the beginning of the population decline was the rapid transitioning from socialism to capitalism. This study has revealed the causes of severe population decline to be a combination of steadily-declining birth rate, sharply rising high death rate, and mass emigration of people to wealthier European states. The cross-over of birth rate and death rate could be attributed to the tumultuous societal upheavals in the changeover from the socialistic protective-welfare system to a free-market capitalistic economic system. In particular, this traumatic event had probably affected the physical and mental health of many people to result in premature deaths from, among other things, consequential morbidity, accidents, homicides and suicides. Practicable remedies to arrest the continuing trend of precipitous decline in the population might include a) repairing the failures of the current modality of national health care, b) creating higher paying jobs in Latvia to entice prospective young emigrants to stay in Latvia, and c) repatriating of recent Latvian émigrés.

Population Dynamics of Municipalities in Central Russia

2017 ◽  
Vol 2017 (6) ◽  
pp. 97-124
Author(s):  
Irina Kalabikhina ◽  
Denis Mokrensky
Keyword(s):  
Population Dynamics ◽  
Elderly Population ◽  
Population Change ◽  
Population Decline ◽  
The Elderly ◽  
Second Stage ◽  
Central Russia ◽  
Population Concentration ◽  
Population Reduction ◽  
Demographic Policy

In this paper we present the results of the analysis of the population change in nonmetropolitan city municipalities by components and concentration of population in the municipalities were investigated, their typologization was developed in accordance with the contribution of various components to population dynamics. The article discusses the limitations of municipal statistics. The methods of average values, the balance equation, and the measures of population concentration are used. The main conclusions confirm the trends of population decline at the second stage of demographic policy, territorial unevenness and concentration of population in administrative centers and the closest settlements to them. Less than 2% of the municipalities in question demonstrate both natural and migratory growth, and in 70% of municipalities both migration and natural components make a contribution to population reduction. The relatively high proportion of the elderly population was observed in the studied municipalities; crude birth and death rates were worse than the average in the district.

An Experimental Field Study to Examine Whether Capillaria Hepatica (Nematoda) Can Limit House Mouse Populations in Eastern Australia.

1995 ◽  
Vol 22 (1) ◽  
pp. 31 ◽  
Author(s):  
GR Singleton ◽  
GR Singleton ◽  
LK Chambers ◽  
LK Chambers ◽  
DM Spratt ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Host Population ◽  
Rapid Decline ◽  
Low Density ◽  
Noticeable Effect ◽  
Mouse Population ◽  
Apparent Lack ◽  
Capillaria Hepatica ◽  
Experimental Field ◽  
Eastern Australia

A replicated experimental field investigation to examine the effect of the nematode parasite Capillaria hepatica on populations of Mus domesticus is described. A 2-year study was conducted at 7 sites with matching farming practices, soil types, topography and habitat heterogeneity on the Darling Downs in south-eastern Queensland, Australia, where mice cause substantial economic, social and environmental problems. A 4 km2 sampling zone was designated on each site and sites were assigned randomly to one of 3 untreated and 4 treated groups. The parasite was released successfully on 3 occasions at 3 markedly different stages of mouse population dynamics. The first release was in winter 1992 into a low-density, non-breeding population. Mice on treated sites had significantly lower survival for 6 months after the release than mice on untreated sites. The parasite had a relatively high impact on survival of young mice (<72 mm long) 2 months after its release. The greatest impact on old mice (>76 mm) occurred a month later. The most pronounced effects of C. hepatica on mouse abundance occurred during the 4 months after its release (June-September). Mice on the untreated sites, however, had poor survival in September, so by October their population abundance was at a level similar to that of the treated populations. Once breeding began in mid-October C. hepatica had no noticeable effect on mouse population dynamics. This was because the parasite (i) had no effect on breeding of mice, (ii) had minimal transmission and (iii) had a diminishing effect on survival after October. The apparent lack of transmission of C. hepatica was probably due to a combination of low population density, the transient nature of the mouse population and predominantly dry weather for 6 months after the release. A second release was made in February 1993 into a breeding, medium-density host population that was rapidly increasing in abundance. Less than 2% of the population was affected during the release so interest focused on transmission rather than the effect of the parasite on the host's demographic machinery. Transmission did occur at a low rate and the parasite persisted for 4.5 months (to June) when it was decided to boost the proportion of mice infected in order to follow its effect on the overwintering population and the demographic effects during the next breeding season. This late release was compromised by synchronous, widespread and rapid decline in mouse densities. Densities fell from greater than 500 ha to less than 1 ha in less than 6 weeks. Two messages emerge from these studies. First, C. hepatica will not limit mouse populations if it is released into a low-density population during a long dry period on the Darling Downs. Second, more information is needed about the factors that influence the survival and transmission of the parasite under field conditions.

scholarly journals Evidence of breeding activity of subadult Turdus thrushes in Argentina

2019 ◽  
Vol 27 (3) ◽  
pp. 149-152
Author(s):  
Exequiel Barboza ◽  
Patricia Capllonch ◽  
Fernando Diego Ortiz ◽  
Alex E. Jahn
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Bird Species ◽  
Life History Strategies ◽  
Brood Patch ◽  
Breeding Condition ◽  
Different Populations ◽  
Males And Females ◽  
Breeding Seasons ◽  
Subadult Female

AbstractLittle is known about the age at which many Neotropical bird species first attempt to breed. We evaluated the breeding condition of 515 adult and subadult males and females among four species of Turdus thrushes (T. nigriceps, T. chiguanco, T. amaurochalinus and T. rufiventris) in Tucumán, Argentina during three breeding seasons (2015 to 2018). We registered a total of 126 individuals with brood patches and cloacal protuberances, which accounted for 24.5% of thrushes in breeding condition that we sampled. Forty thrushes had a brood patch (31.7% of those in breeding condition), of which 11 were subadults (8.7%). Eighty-six thrushes (68.3%) had a swollen cloacal protuberance, 18 of which were subadults (14.3%). Only a few of the subadults in breeding condition built nests, incubated eggs or raised nestlings. Of 130 nests we found, only 3 belonged to a subadult thrush (in all cases, a subadult female with an adult social mate), one of which was successful. Further research on these patterns among various Neotropical bird species could lead to important insights into the life history strategies that characterize different populations, and how these ultimately affect their population dynamics.

Variation in maternal attendance patterns and pup behaviour in a declining population of Steller sea lions (Eumetopias jubatus)

1997 ◽  
Vol 75 (8) ◽  
pp. 1241-1246 ◽  
Author(s):  
Wendy R. Hood ◽  
Kathryn A. Ono
Keyword(s):  
Prey Availability ◽  
Population Decline ◽  
High Tide ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Breeding Area ◽  
Foraging Effort ◽  
Sea Lions ◽  
Attendance Patterns ◽  
Breeding Seasons

Maternal attendance patterns of lactating female Steller sea lions (Eumetopias jubatus) and the activity budgets of pups on Año Nuevo Island, California, were compared between the 1973 and 1992 breeding seasons to investigate temporal changes in behaviour that may be associated with population decline. Females were absent from the breeding area longer in 1992, which may reflect increased foraging effort. Pups also spent significantly less time sucking and more time swimming in 1992. Suckling time is correlated with milk intake in some otariid species, thus the decreased amount of time 1992 pups spent sucking could reflect a reduction in the total volume of milk produced by females. Pups in 1992 are likely to have spent more time swimming than pups in 1973 because high tide covered a greater proportion of the study site in 1992 than in 1973. An increase in time females spent at sea and a decrease in time pups spent sucking are consistent with behavioural changes associated with reduced prey availability.

The Flatback Turtle, Chelonia depressa, in Queensland: Reproductive Periodicity, Philopatry and Recruitment

1984 ◽  
Vol 11 (3) ◽  
pp. 579 ◽  
Author(s):  
CJ Limpus ◽  
A Fleay ◽  
V Baker
Keyword(s):  
Breeding Season ◽  
Sea Turtles ◽  
Recruitment Rate ◽  
Southern Limit ◽  
Total Fecundity ◽  
Eastern Australia ◽  
Reproductive Life ◽  
Breeding Seasons ◽  
Remigration Interval ◽  
High Degree

The Bundaberg coast is the southern limit for reproduction by Chelonia depressa in eastern Australia. Here the species lays 2.84 � 0.78 (mean � SD) clutches per breeding season with a renesting interval of 15.99 � 1.89 days. When successful nesting does not occur on a nesting crawl the female returns after 1.17 � 1.07 d for another attempt. The mean remigration interval is 2.65 � 0.92 years and the average female is estimated to have a reproductive life of between 2.05 and 2.55 breeding seasons. The estimated annual recruitment rate of neonate nesting females into this colony is 27.2 � 10.8% of the population. The females return repetitively with a high degree of accuracy to the same small nesting beach within a single breeding season and in successive breeding seasons. The reproductive strategy of C. depressa compared with that of other sea turtles appears to involve an increase in hatchling size, to reduce predation, achieved by laying relatively large eggs. However, only a few small clutches are laid in a breeding season, so that seasonal fecundity for the species is low relative to that in other sea turtles such as C. mydas. Because its reproductive life is longer, C. depressa has a total fecundity only slightly less than that of C. mydas.

scholarly journals Information on population trends and biological constraints from bat counts in roost cavities: a 22-year case study of a pipistrelle bats (Pipistrellus pipistrellus Schreber) hibernaculum

2015 ◽  
Vol 42 (1) ◽  
pp. 35 ◽  
Author(s):  
Christian Kerbiriou ◽  
Jean François Julien ◽  
Sophie Monsarrat ◽  
Philippe Lustrat ◽  
Alexandre Haquart ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Size ◽  
Spatial Scales ◽  
Population Decline ◽  
Current Trend ◽  
Biodiversity Loss ◽  
Population Trends ◽  
Railway Tunnel ◽  
Biodiversity Indicators ◽  
Pipistrellus Pipistrellus

Context According to the current trend of biodiversity loss, information on population trends at large temporal and spatial scales is necessary. However, well documented animal population dynamics are generally based on intensive protocols requiring animal manipulation, which can be impossible to conduct in species for which conservation is a concern. Aims For many bat species, an alternative approach entails performing an appropriate analysis of counts in roost cavities. Because of managers’ perception of chaotic variations through time, relatively few count monitoring surveys are regularly analysed. Here, we present the analysis of a twenty-two-year survey of a large hibernaculum of pipistrelle bats (Pipistrellus pipistrellus) located in a railway tunnel in Paris, France. Methods We propose that using combinations of population-dynamics modelling using demographic parameters from the literature and statistical analyses helps with identifying the biological and methodological effects underlying the dynamics observed in census analyses. Key results We determined that some of the observed year-to-year variations of population size cannot be explained only by the intrinsic dynamics of the population. In particular, in 1993–94, the population size increased by >40%, which should have implied a massive immigration. This change coincided with the end of the operation of the railway line. After consideration of a drastic trend of population decline (7% year–1), we were able to detect this event and several environmental effects. Specifically, the winter conditions and the temperature in July affected the colony size, presumably because of aggregative behaviour and reproduction success, respectively. Conclusions Emigration–immigration processes might have preponderant effects on population dynamics. In addition, our analysis demonstrated that (1) the study population suffered a large decline, (2) a combination of human disturbance and meteorological variation explains these dynamics and (3) emigration–immigration processes have preponderant effects on the population dynamics. Implications To conduct a meaningful analysis of non-standard time series and provide a source of data for implementing biodiversity indicators, it is necessary to include (1) the local knowledge of the people involved in the field surveys in these analyses (the existence of disturbances and site protections) and (2) meteorological information for the appropriate seasons of the year.

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