Population Processes of the Silky Desert Mouse Pseudomys apodemoides (Rodentia), in Mature Heathlands

1981 ◽  
Vol 8 (3) ◽  
pp. 499 ◽  
Author(s):  
A Cockburn
Keyword(s):  
Sex Ratio ◽  
Population Ecology ◽  
Breeding System ◽  
Food Resources ◽  
Rapid Response ◽  
Population Processes ◽  
Western Victoria

The population ecology of P. apodemoides was examined at two mature heathland localities in western Victoria. At the more mesic Little Desert site animals bred in spring and summer, but at the xeric Big Desert site they bred in winter. Such a discrepancy may arise from phenological differences between the two sites, rather than successional or climatic differences. Both populations were characterized by high levels of transience, and one instance of long-term dispersal was recorded. The breeding system may be promiscuous, and large; unstable groups of animals of both sexes may occupy individual burrows. The sex ratio at breeding was female-biased, which generates a capacity for rapid response to fluctuations in food resources. This is valuable in habitats frequently perturbed by fire and drought.

scholarly journals Can we reestablish a self-sustaining population? A case study on reintroduced Crested Ibis with population viability analysis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yashuai Zhang ◽  
Fang Wang ◽  
Zhenxia Cui ◽  
Min Li ◽  
Xia Li ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Carrying Capacity ◽  
Wild Population ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Viability Analysis ◽  
Crested Ibis ◽  
Reintroduced Population

Abstract Background One of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability. The wild population of the Crested Ibis (Nipponia nippon) has recovered to approximately 4400, and several reintroduction programs have been carried out in China, Japan and Korea. Population viability analysis on this endangered species has been limited to the wild population, showing that the long-term population growth is restricted by the carrying capacity and inbreeding. However, gaps in knowledge of the viability of the reintroduced population and its drivers in the release environment impede the identification of the most effective population-level priorities for aiding in species recovery. Methods The field monitoring data were collected from a reintroduced Crested Ibis population in Ningshan, China from 2007 to 2018. An individual-based VORTEX model (Version 10.3.5.0) was used to predict the future viability of the reintroduced population by incorporating adaptive patterns of ibis movement in relation to catastrophe frequency, mortality and sex ratio. Results The reintroduced population in Ningshan County is unlikely to go extinct in the next 50 years. The population size was estimated to be 367, and the population genetic diversity was estimated to be 0.97. Sensitivity analysis showed that population size and extinction probability were dependent on the carrying capacity and sex ratio. The carrying capacity is the main factor accounting for the population size and genetic diversity, while the sex ratio is the primary factor responsible for the population growth trend. Conclusions A viable population of the Crested Ibis can be established according to population viability analysis. Based on our results, conservation management should prioritize a balanced sex ratio, high-quality habitat and low mortality.

Breeding system can affect the offspring sex ratio in Syrian hamsters

2011 ◽  
Vol 45 (1) ◽  
pp. 55-57 ◽  
Author(s):  
M O M Chelini ◽  
N L Souza ◽  
E Otta
Keyword(s):  
Sex Ratio ◽  
Breeding System ◽  
Offspring Sex Ratio ◽  
Syrian Hamsters ◽  
Offspring Sex

scholarly journals Some aspects of the history and population ecology of the tsessebe damaliscus lunatus lunatus in the Kruger National Park

Koedoe ◽  
1977 ◽  
Vol 20 (1) ◽  
Author(s):  
S.C.J. Joubert ◽  
P.J.L. Bronkhorst
Keyword(s):  
Sex Ratio ◽  
Population Ecology ◽  
Age Structure ◽  
National Park ◽  
Kruger National Park ◽  
Population Trends ◽  
Social Organisation ◽  
Developmental History ◽  
The Social ◽  
History Of

The population trends and distribution of the tsessebe population of the Kruger National Park are evaluated in terms of the available data derived from records compiled in the developmental history of the Kruger National Park (KNP). The recent numerical status of the population is also given. A description of the habitats favoured by tsessebe in the KNP is presented as well as an analysis of the age structure and sex-ratio of the population. Aspects of the social organisation of tsessebe affecting the interpretation of the age structure and sex-ratio phenomena of the population, are also discussed.

scholarly journals Assessing Summer Pond and Lake Inlet Use by Gray Treefrogs (Hyla versicolor/chrysoscelis complex) Using PVC Pipe Traps in Northwest Missouri

2020 ◽  
Vol 48 (2020) ◽  
pp. 17-21
Author(s):  
J. D. McGhee
Keyword(s):  
Sex Ratio ◽  
Hyla Versicolor ◽  
Monitoring Methods ◽  
Contingency Table Analysis ◽  
Detection Rates ◽  
Sampling Locations ◽  
Table Analysis ◽  
Pvc Pipe ◽  
Gray Treefrog

Abstract The widespread decline in amphibian populations highlights the need for establishing rigorous monitoring methods for long-term population studies. In an attempt to launch a long-term monitoring study for a Gray Treefrog complex (Hyla versicolor LeConte /chrysoscelis Cope, hereafter treefrog) population in northwest Missouri, I tested the use of PVC pipe traps in a system of ponds and inlets along a lakeside habitat for three years. For each pond (3) and inlet (2), I established an array of 16 pipes so as to compare differences in use between pipe location, ponds and inlets, and sex ratio between sites. Pipes were checked twice a week during the summer for the presence of treefrogs. Treefrog usage of pipes between ponds and inlets were compared using a contingency table analysis, while an ANOVA was used to assess differences in sex ratios between sites (α = 0.05). A single inlet was used by treefrogs more heavily than the other ponds or inlet (G = 13.61, df = 3, P = 0.0035), however, I found no differences in terms of pipe location within a pond or inlet. Mean sex ratio between water bodies varied but did not significantly differ. There appears to be little effect in terms of pipe placement within our 50 m buffer from the water's edge, but unique habitat effects at sampling locations may significantly affect detection rates or usage.

Mortality and breeding failure of little penguins, Eudyptula minor, in Victoria, 1995 - 96, following a widespread mortality of pilchard, Sardinops sagax

2000 ◽  
Vol 51 (4) ◽  
pp. 355 ◽  
Author(s):  
Peter Dann ◽  
F. I. Norman ◽  
J. M. Cullen ◽  
F. J. Neira ◽  
A. Chiaradia
Keyword(s):  
At Risk ◽  
Breeding Season ◽  
Breeding Success ◽  
Egg Laying ◽  
First Year ◽  
Breeding Failure ◽  
Food Species ◽  
Intestinal Parasitism ◽  
Western Victoria

In May 1995, numbers of little penguins, Eudyptula minor, coming ashore declined at Phillip Island and St Kilda concurrently with deaths of many penguins in western Victoria and a massive mortality of one of their food species (pilchard) throughout southern Australia. Among 1926 dead penguins reported were 131 banded birdsrecovered from Phillip Island (86% adults and 14% first-year birds), 26 from Rabbit Island and six from St Kilda. The number of banded penguins found dead per number of adult Phillip Island birds at risk was 2.3% in 1995 compared with an annual mean of 0.7% for 1970–93. Of 29 corpses autopsied, at least 26 died of starvation associated with mild–severe gastro-intestinal parasitism. Following the pilchard mortality, egg-laying by penguins in the subsequent breeding season (1995–96) was ~2 weeks later than the long-term mean and 0.3 chicks were fledged per pair compared with the long-term mean of 1.0. Unlike previous years, few penguins were recorded in Port Phillip Bay in September–October 1995, a period when pilchard schools were infrequently seen. It is concluded that the increase in penguin mortality in northern Bass Strait and the significant reduction in breeding success were associated with the widespread pilchard mortality.

A Decade of Mark-Recapture of Platypuses on The Duckmaloi River: Any New Insights into Population Dynamics?

1998 ◽  
Vol 20 (2) ◽  
pp. 302
Author(s):  
D. Goldney
Keyword(s):  
Sex Ratio ◽  
New South ◽  
First Year ◽  
Mark Recapture ◽  
South Wales ◽  
Adult Status ◽  
Second Year ◽  
Gill Netting ◽  
Population Numbers

A long-term mark-recapture program has been carried out on the Duckmaloi Weir (near Oberon, New south Wales) and associated river over the period 1986 to the present. The pipehead weir creates a long shallow ·pool' about 2.5 ha in area, ideal for gill-netting platypuses. One hundred and eighty-two (182) individual animals have been captured in excess of 500 times. The majority of animals have been captured in the weir pool. A very dynamic situation exists with new adults and juveniles being captured on a regular basis and conversely captured animals "disappearing" on a regular basis from the system. Some individuals exhibit both transience and site attachment characteristics. However, relatively few animals remain site attached for long periods of time. Sixty nine percent of individuals are captured two or fewer times. Band loss cannot account for this phenomenon. Of the captured animals, 11.3% have been caught more than 5 times. The sex ratio of the population favours females in first capture adults (1:1.72) but males in first capture juveniles (1:0.73). Females are more likely to be recaptured than males. The sex ratio of juveniles varies significantly from year to year. The period between recaptures varies greatly and can be up to 6 years. Four animals have been captured over nine years (3 females/1 male) but no animal has been captured every year of the study. Recruitment has occurred at levels able to maintain the current population numbers. Thirty percent of available adults have been found lactating, including second year females. Seventy one percent of first year capture juveniles and 89.9% of first capture adults "disappear" within two years of first capture. Forty two percent of juvenile animals reach adult status before "disappearing".

Maximization of long-term productivity in a rat colony

1972 ◽  
Vol 6 (2) ◽  
pp. 203-206 ◽  
Author(s):  
N. T. Gridgeman ◽  
J. M. Taylor
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Albino Rats ◽  
Mathematical Treatment ◽  
Production Time ◽  
Time Curve ◽  
Intensive Breeding

Maximization of intensive breeding in the animal colony can be approached using a simple mathematical treatment of the production-time curve. It has been found that in a colony of specified-pathogen-free albino rats whose breeding dams were averaging litters of 11 at 6-week intervals, the stock should be entirely replaced at intervals of 27-28 weeks to maximize the output of weanlings. Some data on litter size and sex ratio are also presented.

Superparasitism Occasionally Predisposes Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae) to Develop Gregariously in Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae)1

2002 ◽  
Vol 37 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Eric Wellington Riddick
Keyword(s):  
Sex Ratio ◽  
Spodoptera Exigua ◽  
Host Density ◽  
Adult Emergence ◽  
Cotesia Marginiventris ◽  
First Instar ◽  
Emergence Rate ◽  
Lepidoptera Noctuidae ◽  
Density Treatment

Experiments were designed to estimate the incidence of superparasitism of Spodoptera exigua (Hübner) and gregarious development of Cotesia marginiventris (Cresson). Dissections of host larvae revealed that superparasitism was common at all host densities (5, 10, or 20 larvae per 0.05 liter arena). At least two parasitoid eggs were present per host on day 1 after parasitoid oviposition; eggs were scarcely found on day 2 and never found on days 3, 4 or 5. More than one parasitoid first instar was present per host on day 2 at all densities, although more were found in hosts of the 5 density rather than the 20 density treatment. Second instars were present in hosts on days 3, 4 and 5, and at least one was present per host on day 5. Third instars (the final instar stage) were not present inside hosts by day 5. Rearing of host larvae demonstrated that gregarious development was rare, since less than 6% of parasitized hosts yielded two third instars that spun cocoons. Neither host density nor exposure time (24 h, 48 h) had an effect on the occurrence of gregarious development. The adult emergence rate was 64% and the sex ratio was male-biased for parasitoids that developed gregariously. The adult emergence rate was 73% and the sex ratio was unbiased for those that developed solitarily. This research suggests that superparasitism of hosts by C. marginiventris can occasionally predispose parasitoid larvae to develop gregariously. Frequent superparasitism of hosts may be detrimental to the long-term propagation of C. marginiventris.

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