scholarly journals Long‐term changes in population size and the age structure and sex ratio of waterbuck in a Sudanian savannah of Burkina Faso

2020 ◽  
Author(s):  
Sidiki Konate ◽  
Djidama Sirima ◽  
Lankoande Ardjima ◽  
Youssouf Sanou ◽  
Emmanuel M. Hema ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Burkina Faso ◽  
Population Size ◽  
Age Structure ◽  
Long Term Changes

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.

scholarly journals A management plan for a declining population of the Souss valley tortoise in an arid steppe-land of west-central Morocco

2021 ◽  
Author(s):  
Hichami Nawal ◽  
MOHAMMED ZNARI
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Extinction Risk ◽  
Management Plan ◽  
Habitat Destruction ◽  
North West ◽  
West Central ◽  
Arid Steppe ◽  
The Impact

The endangered Moorish tortoise Testudo graeca is the unique terrestrial chelonian species in North-west Africa. In west-central Morocco, the endemic subspecies, the Souss valley tortoise T. g. soussensis, occupies semi-arid to arid low-quality habitats, and is subject to serious threats. A long-term mark-recapture programme from 2001 to 2012 allowed estimating population size and structure, sex ratio, and survivorship in one of the well-known populations in a degraded and overgrazed arid steppe-land of west-central Morocco. Spring population size considerably decreased to more than half in less than 10 years, with a mean density lower than 3 ind.ha-1 in 2012 compared to its last known density estimat-ed in 2003. In spring 2012, the population structure exhibited an unbalanced male-biased sex ratio (61:39) and a scarcity of juveniles (<5%). We identified five major conservation problems in the study area: (i) habitat destruction and overgrazing; (ii) over-collecting of tortoises for pet trade , iii) direct dis-turbance; iv) tortoise handling mostly for field research, and v) increased extinction risk due to the small population size. We carried out a population viability analysis using the VORTEX software based on published and obtained data on population and life history parameters. With no management action, the population will go extinct during the forthcoming 40 years after the last estimate. The most efficient management option for a long-term persistence of the population would be reducing the nest and neo-nate mortality by 90%. To attenuate the impact of the threatening factors, we developed a management plan that includes population reinforcement and habitat restoration options. 

scholarly journals Population biology of Parides anchises nephalion (Papilionidae) in a coastal site in Southeast Brazil

2001 ◽  
Vol 61 (4) ◽  
pp. 623-630 ◽  
Author(s):  
A. V. L. FREITAS ◽  
R. R. RAMOS
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Residence Time ◽  
Age Structure ◽  
Population Biology ◽  
Coastal Site ◽  
Population Peak ◽  
Se Brazil ◽  
The Mean ◽  
Travel Distances

A population of Parides anchises nephalion was studied during seven months in SE Brazil. The population size was about 10-20 individuals (with theoretic maximum near 60 individuals), with small variations in some months. Sex ratio was male biased, with males dominating in all months. The age structure was not stable, with an increase in new individuals before the population peak in December. The residence time was 14.1 ± 8.2 days for males and 9.0 ± 3.6 to females, with the maximum registered of 30 days. Males can travel distances of up to 400 m, but most individuals were always recaptured in the same site. The mean forewing length was greater in females. The population features agree with those found in other species of Parides in other neotropical sites.

scholarly journals Population Viability and Resource Competition on North Brother Island: Conservation Implications for Tuatara (Sphenodon Punctatus) and Duvaucel's Gecko (Hoplodactylus Duvaucelii)

2021 ◽  
Author(s):  
◽  
Joanna Wilson
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Body Condition ◽  
Resource Competition ◽  
Adult Population ◽  
Population Viability ◽  
Adult Survival ◽  
Intraspecific Interactions ◽  
Sphenodon Punctatus

<p>Population viability for small, isolated populations is determined by many factors, particularly demographic stochasticity. Coexistence of communities is promoted through resource partitioning, particularly if species share similar niche requirements. Demographic characteristics, long-term trends and patterns of partitioning were investigated for two reptile species: tuatara (Sphenodon punctatus) and Duvaucel's gecko (Hoplodactylus duvaucelii), using mark recapture techniques on North Brother Island, New Zealand. Capture time and location were recorded as well as snout-vent length, mass and sex of individuals. Adult population size, sex ratio, survival and recapture probability for both species were estimated. Intervention will be needed to prevent population collapse for tuatara, as the population is male-biased (3.24 males: 1 female), with sub-adults exhibiting a stronger bias (4.1 males: 1 female). The total population size is estimated at 390-437 adults, with high adult survival (95%). The Duvaucel's gecko population is stable enough to be harvested for translocation, as the population was estimated at 583-677 adults, with an even sex ratio. Adult survival was high (92%) and longevity is at least 43-50 years. Patterns in partitioning suggest tuatara are excluding Duvaucel's gecko as tuatara occupy vegetated areas and few animals were caught at the same time in the same place as a member of the other species (~10%). Long-term site fidelity appears to occur in both species as the majority of animals were captured previously within 10m (tuatara) or 15m (Duvaucel's gecko) of their 2008 location, and travelled less than 2m per year on average. Tuatara show an overall decline in body condition since 1957, which is more rapid in females, and may be related to intraspecific interactions and density-dependent effects. Gecko body condition is not declining, suggesting no negative effects at the population level are occurring as a result of competitive exclusion. This study indicates that characteristics that have implications for population viability have the capacity to differ, even for species with similar niche requirements occupying the same habitat, and supports the considerable value of long-term monitoring.</p>

Biology of Tiger Sharks (Galeocerdo cuvier) caught by the Queensland Shark Meshing Program off Townsville, Australia

1992 ◽  
Vol 43 (1) ◽  
pp. 33 ◽  
Author(s):  
C Simpfendorfer
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Adult Males ◽  
Gill Nets ◽  
Galeocerdo Cuvier ◽  
Total Length ◽  
Sea Snakes ◽  
Apparent Decrease ◽  
Size At Birth

The biology of 835 specimens of Galeocerdo cuvier caught between 1964 and 1986 off Townsville, Australia, was examined. The sharks were caught in a protective meshing programme using both large mesh gill-nets and set lines. The size at birth was estimated to be 80-90 cm total length, and females matured at approximately 287 cm total length. Litter sizes ranged from 6 to 56. Breeding and pupping both appear to occur in summer, with females not breeding every year. Mature females possibly migrate inshore during late spring and summer to give birth. The sex ratio of juveniles and adults favoured females, with few adult males being caught. Ontogenic changes in the diet were observed, with juveniles feeding predominantly on teleosts, sea snakes and birds and adults mostly consuming teleosts, sea snakes, turtles and crabs. There was no apparent decrease in the population size of G. cuvier in the Townsville area as a result of the long-term catching of sharks by the protective meshing programme.

scholarly journals Population Viability and Resource Competition on North Brother Island: Conservation Implications for Tuatara (Sphenodon Punctatus) and Duvaucel's Gecko (Hoplodactylus Duvaucelii)

2021 ◽  
Author(s):  
◽  
Joanna Wilson
Keyword(s):  
Sex Ratio ◽  
Population Size ◽  
Body Condition ◽  
Resource Competition ◽  
Adult Population ◽  
Population Viability ◽  
Adult Survival ◽  
Intraspecific Interactions ◽  
Sphenodon Punctatus

<p>Population viability for small, isolated populations is determined by many factors, particularly demographic stochasticity. Coexistence of communities is promoted through resource partitioning, particularly if species share similar niche requirements. Demographic characteristics, long-term trends and patterns of partitioning were investigated for two reptile species: tuatara (Sphenodon punctatus) and Duvaucel's gecko (Hoplodactylus duvaucelii), using mark recapture techniques on North Brother Island, New Zealand. Capture time and location were recorded as well as snout-vent length, mass and sex of individuals. Adult population size, sex ratio, survival and recapture probability for both species were estimated. Intervention will be needed to prevent population collapse for tuatara, as the population is male-biased (3.24 males: 1 female), with sub-adults exhibiting a stronger bias (4.1 males: 1 female). The total population size is estimated at 390-437 adults, with high adult survival (95%). The Duvaucel's gecko population is stable enough to be harvested for translocation, as the population was estimated at 583-677 adults, with an even sex ratio. Adult survival was high (92%) and longevity is at least 43-50 years. Patterns in partitioning suggest tuatara are excluding Duvaucel's gecko as tuatara occupy vegetated areas and few animals were caught at the same time in the same place as a member of the other species (~10%). Long-term site fidelity appears to occur in both species as the majority of animals were captured previously within 10m (tuatara) or 15m (Duvaucel's gecko) of their 2008 location, and travelled less than 2m per year on average. Tuatara show an overall decline in body condition since 1957, which is more rapid in females, and may be related to intraspecific interactions and density-dependent effects. Gecko body condition is not declining, suggesting no negative effects at the population level are occurring as a result of competitive exclusion. This study indicates that characteristics that have implications for population viability have the capacity to differ, even for species with similar niche requirements occupying the same habitat, and supports the considerable value of long-term monitoring.</p>

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