scholarly journals Population of Proboscis Monkey (Nasalis lavatus) in Manggar River, Balikpapan City, Indonesia

2021 ◽  
Vol 886 (1) ◽  
pp. 012068
Author(s):  
Ike Mediawati ◽  
Teguh Muslim ◽  
Amir Ma’ruf ◽  
Mukhlisi ◽  
Hery Seputro ◽  
...  
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Anthropogenic Activities ◽  
Proboscis Monkey ◽  
Adult Males ◽  
Conservation Area ◽  
Nasalis Larvatus ◽  
Survey Technique ◽  
Males And Females ◽  
Proboscis Monkeys

Abstract A population estimation of proboscis monkeys (Nasalis larvatus) has been conducted in Manggar River, Balikpapan. In this non-conservation area, the anthropogenic activities threaten the proboscis monkey habitat. Boat survey technique was applied along ± 17 km of the river in the morning and evening. The number of proboscis monkeys in the surveyed area was estimated to range from 57 to 69 individuals with estimated population density of 4.75 individuals/Km2. Moreover, the population of this primates was divided into 4 groups and the sex ratio between adult males and females was 1:2.33. The proboscis monkeys were distributed in the middle of the river to the upstream. The highest population was found in the upstream area with less human activities. Conservation efforts in the Manggar River need to be carried out considering the proboscis monkey habitat in the area has been fragmented and isolated. These efforts could involve local economic communities.

Population parameters of ringed seals (Phoca hispida Schreber, 1775) in the Svalbard area

1987 ◽  
Vol 65 (4) ◽  
pp. 1021-1027 ◽  
Author(s):  
Christian Lydersen ◽  
Ian Gjertz
Keyword(s):  
Sex Ratio ◽  
Ringed Seal ◽  
Adult Males ◽  
Population Parameters ◽  
Phoca Hispida ◽  
Age Class ◽  
Ringed Seals ◽  
Males And Females ◽  
The Mean ◽  
Sexually Mature

Samples were taken from 284 ringed seals (Phoca hispida) in the Svalbard area during April–July 1981 and March–April 1982. The age of 283 seals was determined by reading annuli in the cementum of the canine teeth. The mean age of the males was 11.3 years, and of the females, 14.9 years. Females were found to be significantly older than males. The mean length of sexually mature ringed seals was 128.9 cm for both sexes. The mean weight of adult males and females was 53.5 and 61.4 kg, respectively. Females were found to be significantly heavier than males. The sex ratio was 47.8% males and 52.2% females. Studies of microscopic sections of testis and epididymis from ringed seal males showed that 63, 75, and 80% of 5-, 6-, and 7-year-old animals, respectively, were sexually mature. The weights of testis and epididymis, diameters of tubuli, and the size of testis all showed a marked increase in the 5-year age-class. Macroscopic sections of ovaries from ringed seal females showed that 20, 60, and 80% of 3-, 4-, and 5-year-old animals, respectively, were sexually mature. The size of the ovaries showed a marked increase in the 5-year age-class. The ovulation rate of ringed seals from Svalbard was calculated to be 0.91.

Demography of Eurotestudo hermanni in a mesic area of Central Italy

2007 ◽  
Vol 28 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Valeria Ramacciato ◽  
Massimo Capula ◽  
Anna Loy ◽  
Federica Gentilotti
Keyword(s):  
Sex Ratio ◽  
Central Italy ◽  
Average Density ◽  
High Density ◽  
Environmental Constraints ◽  
Adult Males ◽  
Males And Females ◽  
European Populations

AbstractHermann's tortoise (Eurotestudo hermanni) from a mesic area of Central Italy (Isernia, Molise) was investigated during a two-year period (2003-2004). The population is characterized by a fairly high density when compared to other Italian and European populations, with density ranging from 16.16 individuals/ha in 2003 to 25.08 individuals/ha in 2004 (average density 20.84/ha). The sex ratio was 1:1 both in 2003 and 2004. Females were captured in higher percentages from May to July in both years, while males were most abundant from August to October. These differences can be related to the different needs and behaviour of males and females in the two periods, and to the environmental constraints of the study area. All the marked tortoises were found aged between 10 and 21 years. Adult males and females from the study area were small-sized when compared to those from other Italian and European populations.

scholarly journals PENDUGAAN POPULASI BEKANTAN (Nasalis larvatus) DI TAMAN WISATA ALAM TANJUNG BELIMBING KECAMATAN PALOH KABUPATEN SAMBAS

2019 ◽  
Vol 7 (4) ◽  
Author(s):  
Selpa Selpa ◽  
Slamet Rifanjani ◽  
Muflihati Muflihati
Keyword(s):  
Nature Conservation ◽  
Endangered Species ◽  
Large Population ◽  
Population Decline ◽  
Primate Species ◽  
Survey Method ◽  
Proboscis Monkey ◽  
Species Status ◽  
Conservation Area ◽  
Nasalis Larvatus

Proboscis monkey (Nasalis larvatus) is an endemic animal of Borneo including protected primate species as an endangered species status. This species listed as an endangered species caused by large population decline and habitat demage continues to threaten the proboscis population. This research was conducted in Taman Wisata Alam Tanjung Belimbing (TWATB) is a nature conservation area that supports the conservation of proboscis monkey. The purpose of this research is to collect the amount of proboscis monkey populations, so as to provide an overview of conservation efforts that must be carried out. The method was used the River Survey method. The result of Proboscis research based on the age level was found consisted average of 5 adult male individuals, 6 adult female individuals, 7 adolescent individuals and 5 childs. Estimation of the population is calculated using the King’s Method. Estimated individuals population is 12 individuals with a density of 25.5 individuals/km2.Keywords: Proboscis monkey, Population, Tanjung Belimbing, Paloh.

Sex ratios and survival in fluctuating populations of the deer mouse, Peromyscus mamculatus borealis

1970 ◽  
Vol 48 (4) ◽  
pp. 809-811 ◽  
Author(s):  
Raymond P. Canham
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Deer Mouse ◽  
Sex Ratios ◽  
Natural Populations ◽  
In Captivity ◽  
Males And Females ◽  
Young Of The Year ◽  
Fluctuating Populations ◽  
Number Of Males

In litters of the deer mouse, Peromyscus mamculatus borealis, born in captivity there was a significantly greater number of males than females. In natural populations of the same subspecies, an excess of males caused the sex ratio in captured young of the year to differ significantly from 1:1 only in those summers in which population density increased considerably. The sex ratio did not change appreciably during a winter in which density remained stable, but in winters of low survival the proportion of males declined. A difference between males and females in the amplitude of the fluctuations in postnatal survival thus appeared responsible for variations in the sex ratio.

Adult survival and recruitment and the explanation of an uneven sex ratio in a tortoise population

1990 ◽  
Vol 68 (3) ◽  
pp. 547-555 ◽  
Author(s):  
Adrian Hailey
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Adult Survival ◽  
Adult Longevity ◽  
Adult Males ◽  
Northern Greece ◽  
Female Population ◽  
Lower Survival Rate ◽  
Adult Sex Ratio ◽  
Testudo Hermanni

Survival, recruitment, and dynamics of adult Testudo hermanni at Alyki (northern Greece) were studied from 1980 to 1988. Recruitment of adult males was greater than that of females owing to their shorter time to maturity (9 vs. 11 years); recruitment of subadults (6 years old) was equal in males and females. Mean annual survival was slightly greater in males (0.914) than females (0.877), equivalent to mean adult longevity values of 11.6 and 8.1 years, respectively. Excluding tortoises that die before maturity, male and female T. hermanni are mature for about 56 and 42% of their life, respectively. Generation time was roughly twice the age at maturity, and three times the age at which secondary sexual characters develop, a pattern which may apply to other tortoises. The combination of adult survival and recruitment should lead to a stable sex ratio (males/females) of 2.1. The adult sex ratio was higher than this, but decreasing, from4.1 in 1982to3.0 in 1986, with an increase in the female population; the number of males was stable. The observed sex ratio showed a similar decline and a further fall to 2.4 in 1988. The cause of the lower survival rate of females compared with males is proposed to be damage during courtship attempts. The courtship behaviour and related anatomy of T. hermanni are compared with those of T. graeca, a species with even population sex ratios. The level of male-induced female mortality would depend on population density; the increasing number of females during the study follows the approximate halving of population density in 1980.

scholarly journals Microhabitat preferences of the freshwater prawn Macrobrachium jelskii (Decapoda: Palaemonidae)

2019 ◽  
Vol 109 ◽  
Author(s):  
Jersei N. Silva ◽  
Guilherme de Oliveira ◽  
Sérgio S. da Rocha
Keyword(s):  
Sex Ratio ◽  
Water Reservoir ◽  
Habitat Choice ◽  
Freshwater Prawn ◽  
Adult Males ◽  
Adult Females ◽  
Males And Females ◽  
Microhabitat Preferences ◽  
Lower Depth ◽  
Juvenile Males

ABSTRACT We analyzed the microhabitat preferences of Macrobrachium jelskii (Miers, 1877) males and females inhabiting an urban water reservoir in Cruz das Almas, Bahia, Brazil. Prawns were collected monthly, from March 2015 to February 2016, in three microhabitats, using a sieve. Each microhabitat was dominated by one macrophyte species: Eleocharis sp. (M1), Cabomba sp. (M2), and Nymphaea sp. (M3). The prawns were measured (carapace length), and categorized as juvenile males, adult males, juvenile females, non-ovigerous adult females and ovigerous adult females. An analysis of variance (ANOVA) was used to compare the number and size of individuals. The sex ratio and frequency of ovigerous females in the three microhabitats were also calculated. The sex ratio was biased towards females in M1 and did not deviate from 1:1 in M2 and M3. When prawns were separated into five categories we observed that non-ovigerous adult females were more abundant in M1, while adult males were the most abundant demographic category in M2 and M3. Juveniles of both sexes and ovigerous females showed no microhabitat preference, although M1 and M2 appeared to be more suitable for the latter. Adult females were the largest individuals in all microhabitats. Food availability, lower depth and lower predation pressure in M1 are the main factors that make M1 more suitable for M. jelskii, particularly non-ovigerous adult females and larger adult males. Intraspecific competition for shelter in M1 might also occur and adult females win this competition due to their larger body size. Therefore, adult males are found in higher abundance in M2 and M3 and the juvenile of both sexes spread evenly across all microhabitats. Our results help to understand the ecological role and the niche used by M. jelskii. Future studies on the habitat choice and predation under laboratory conditions should help to understand the behavior of this species.

scholarly journals Sex ratio of breeding Common toads (Bufo bufo) – influence of survival and skipped breeding

2010 ◽  
Vol 31 (4) ◽  
pp. 509-524 ◽  
Author(s):  
Thomas Madsen ◽  
Jon Loman
Keyword(s):  
Sex Ratio ◽  
Deterministic Model ◽  
Breeding Site ◽  
Breeding Population ◽  
Bufo Bufo ◽  
Adult Males ◽  
Breeding Sites ◽  
Lower Survival Rate ◽  
Biased Sex Ratio ◽  
Males And Females

AbstractAnuran sex ratio at breeding sites is typically male biased. Such sex ratios may be due to poor female survival, to females not breeding as frequently as males and/or to males becoming sexually mature earlier than females. In the present study, the first two factors are analyzed in a common toad (Bufo bufo) population in southern Sweden. Toads were captured, marked and recaptured at the breeding site during 5 years. Within season capture patterns were analyzed using the Jolly-Seber model and among-year captures using the Closed robust design model. Population estimates of males and females yielded an among year variation in breeding population sex ratio, ranging from 16% to 34% females. On average, 41% (proportion adult alive but not breeding) of the females skipped breeding seasons, whereas the corresponding estimate for males was less than 5%. Yearly survival averaged 42% for adult female and 63% for adult male toads. First year adult males and females had a lower survival rate than older toads. Our results demonstrate that both a female biased mortality rate and a higher proportion of skipped breeding in females contribute to the observed male biased sex ratio. However, a deterministic model suggests other factors may also be involved to obtain this degree of male biased sex ratio, the most likely being that females mature at a later age than male toads.

scholarly journals The local extinction of the proboscis monkey Nasalis larvatus in Pulau Kaget Nature Reserve, Indonesia

Oryx ◽  
2000 ◽  
Vol 34 (1) ◽  
pp. 66-70 ◽  
Author(s):  
Erik Meijaard ◽  
Vincent Nijman
Keyword(s):  
Carrying Capacity ◽  
Nature Reserve ◽  
Local Extinction ◽  
Monitoring Programme ◽  
Food Sources ◽  
Agricultural Expansion ◽  
Isolated Population ◽  
Proboscis Monkey ◽  
Nasalis Larvatus ◽  
Proboscis Monkeys

AbstractThe population of the threatened proboscis monkey Nasalis larvatus, a Bornean endemic, in the Pulau Kaget Nature Reserve, South Kalimantan, Indonesia, is extinct. Until 1997, this small, isolated population, estimated at c. 300 individuals, had been pushed towards the fringes of the reserve by illegal agricultural expansion. As food sources became depleted, the population apparently exceeded the decreasing carrying capacity of the reserve and was reported to be starving to death. As a solution, 84 animals were translocated to nearby, unprotected sites, resulting in 13 fatalities. An additional 61 animals were taken to a zoo, where 60 per cent died within 4 months of their capture. There was neither a proper pre-translocation assessment of the suitability of the release sites, nor a proper post-translocation monitoring programme for the released animals. We conclude that the Pulau Kaget reserve and its proboscis monkeys have been poorly managed. We provide some suggestions to improve the effectiveness of conservation efforts in Indonesia.

scholarly journals Conservation Status and Population Density of Himalayan Serow (Capricornis sumatraensis) in Annapurna Conservation Area of Nepal

1970 ◽  
Vol 3 ◽  
pp. 12-19
Author(s):  
Achyut Aryal
Keyword(s):  
Land Use ◽  
Habitat Fragmentation ◽  
Population Density ◽  
Sex Ratio ◽  
Conservation Status ◽  
Livestock Grazing ◽  
Conservation Area ◽  
Small Patch ◽  
Annapurna Conservation Area ◽  
Conservation Threats

Himalayan Serow ‘Capricornis sumatraensis' population is isolated in a small patch of the southern part of Annapurna Conservation Area (ACA) with a population density of 1.17 individual/km2 and a population sex ratio of 1:1.6(Male: Female). A strong correlation was found between population (y) and pellets density (x) (y=0.011x-0.2619, R2-0.97). The major problems in the Serow habitat were habitat fragmentation & land use change, conflict between predator and villager, livestock grazing and poaching. The study was successful in providing information on the present status of Himalayan Serow in the ACA Key Words: Population density, Sex ratio, Fragmentation, Conservation, Threats   DOI: 10.3126/init.v3i0.2423 The Initiation Vol.3 2009 p.12-19

scholarly journals Demography of the enigmatic low phase in a cyclic lemming population

2021 ◽  
Author(s):  
Dominique Fauteux ◽  
Gilles Gauthier
Keyword(s):  
Sex Ratio ◽  
Reproductive Potential ◽  
Indirect Evidence ◽  
Adult Males ◽  
Density Dependent ◽  
Live Trapping ◽  
Biased Sex Ratio ◽  
Males And Females ◽  
Cyclic Populations

Abstract Deciphering the mechanism behind the lack of growth during the prolonged low abundance phase of cyclic populations represents a major challenge due to the lack of data. However, long-term capture-mark-recapture datasets can help resolve this question through demographic analyses. We analysed the demography and movements of cyclic brown lemmings on Bylot Island, Canada, with a 16-yr (2004-2019) live-trapping program and looked for inversely density-dependent factors that could contribute to a prolonged low phase. We found that the proportion of females in the population was inversely density-dependent with a strong male-biased sex ratio at low densities but not at high densities. In contrast, survival of adult females was higher than adult males, but both had lower survival at low densities than at high ones. Distances moved by both adult males and females were density-dependent, and proportion of females in reproductive condition was weakly density-dependent. Individual body condition, measured as monthly change in body mass, was not density-dependent. Overall, the strong malebiased sex ratio at very low densities suggests a loss of reproductive potential due to the rarity of females and appears to be the most susceptible demographic factor that could contribute to the prolonged low phase in cyclic brown lemmings. What leads to this sexbias in the first place is still unclear, but indirect evidence suggests that this may be due to a higher vulnerability of nesting females to predation in winter than males.

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