Using faecal pellet counts along transects to estimate quokka (Setonix brachyurus) population density

2005 ◽  
Vol 32 (6) ◽  
pp. 503 ◽  
Author(s):  
Matt W. Hayward ◽  
Paul J. de Tores ◽  
Michael J. Dillon ◽  
Barry J. Fox ◽  
Peter B. Banks
Keyword(s):  
Population Density ◽  
Threatened Species ◽  
Faecal Pellet ◽  
Population Densities ◽  
Jarrah Forest ◽  
Linear Relationships ◽  
Pellet Counts ◽  
Transect Counts ◽  
Fox Control ◽  
Broad Scale

A study was conducted to determine the validity of using transect counts of faecal pellet groups to estimate population densities of a threatened, macropodid marsupial – the quokka (Setonix brachyurus (Quoy & Gaimard, 1830)). Mark–recapture estimates of population density were regressed against counts of faecal pellet groups at six sites with and three sites without fox control within the northern jarrah forest of Western Australia. Significant linear relationships were found between population density and pellet counts for all sites (r2 = 0.56, P < 0.02) and when all unbaited sites were excluded (r2 = 0.98, P < 0.01). We suggest that this method could be used for broad-scale monitoring of this threatened species.

scholarly journals Blue duiker Philantomba monticola densities in the Tsitsikamma National Park and probable factors limiting these populations

Koedoe ◽  
1991 ◽  
Vol 34 (2) ◽  
Author(s):  
N. Hanekom ◽  
V. Wilson
Keyword(s):  
National Parks ◽  
National Park ◽  
Nature Reserve ◽  
Faecal Pellet ◽  
Density Estimates ◽  
Pellet Counts ◽  
Transect Counts ◽  
Fallen Leaves ◽  
Blue Duiker ◽  
Winter Population

Numbers of blue duikers recorded on 157 and 28 variable width transect counts, done over a two year period in the Tsitsikamma Coastal National Park (TCNP) and Tsitsikamma Forest National Park (TFNP) respectively, did not differ significantly {P > 0,10) with seasons (summer v. winter). Population density estimates from transects were similar to those from game drives (0,18 v. 0,19 duikers/ha (TCNP) and 0,13 v. 0,17 duikers/ha (TFNP); P >0,10), higher than from faecal pellet counts (P < 0,10) and at least three times lower than estimates from the Kenneth Stainbank Nature Reserve and Umdoni Park in Natal. Factors contributing to the low population densities in the Tsitsikamma national parks were investigated. Twentyseven and seven percent of leopard (25) and caracal (12) scats respectively analyzed contained blue duiker remains, but predator numbers appear to be low. Forest characteristics were investigated, and results from this and other studies suggest that undergrowth cover does not markedly influence blue duiker densities in the southern Cape forests. Field and stomach analysis indicate that blue duikers feed primarily on freshly fallen leaves and fruit, and are selective foragers. In the Tsitsikamma national parks (TNPs) the frequency of occurrence of trees known to be palatable to duikers are low, while less than 45 percent of the dominant tree species fruit fully annually. This apparent scarcity of food, the low numbers of antelope species and individuals in these forests and results from duiker research in Zaire, suggest that habitat rather than predation is limiting duiker numbers in the Tsitsikamma national parks.

Methods for Small-Scale Surveys of Grey Kangaroo Populations

1985 ◽  
Vol 12 (2) ◽  
pp. 119 ◽  
Author(s):  
GM Coulson ◽  
JA Raines
Keyword(s):  
Population Size ◽  
Survey Methods ◽  
Faecal Pellet ◽  
Critical Conditions ◽  
Small Scale ◽  
Line Transect ◽  
Faecal Pellets ◽  
Grey Kangaroo ◽  
Pellet Counts ◽  
Transect Counts

Small-scale survey methods which have previously been applied to grey kangaroos were evaluated on a population of known size. The total population size of free-ranging eastern grey kangaroos, Macropus giganteus, on Rotamah Island in the Gippsland Lakes of Victoria was determined by a drive count. Two types of small-scale survey methods were evaluated against this total: line transect counts and faecal pellet counts. The line transect estimates were not significantly different from the known population size, and grey kangaroos appear to meet the critical conditions of the models. Counts of individual faecal pellets gave an acceptable estimate of population density, whereas counts based on pellet groups had significant positive bias.

Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

1992 ◽  
Vol 70 (10) ◽  
pp. 2005-2008 ◽  
Author(s):  
Robert Hall ◽  
Lana Gay Phillips
Keyword(s):  
Population Dynamics ◽  
Phaseolus Vulgaris ◽  
Population Density ◽  
Fusarium Solani ◽  
Population Densities ◽  
Total Rainfall ◽  
Colony Forming Units ◽  
Bean Crop ◽  
Previous Summer ◽  
Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

Population Densities Allowed Around Dutch SEVESO Establishments

2000 ◽  
Author(s):  
G. M. H. Laheij ◽  
B. J. M. Ale ◽  
J. G. Post
Keyword(s):  
Population Density ◽  
The Netherlands ◽  
Individual Risk ◽  
Population Densities ◽  
Planning Policy ◽  
Relative Contribution ◽  
Societal Risk ◽  
Dangerous Substances ◽  
The Individual ◽  
Uniform Population

Abstract In the Netherlands, the individual risk and societal risk are used in efforts to reduce the number of people exposed to the effect of an accident at an establishment with dangerous substances. To facilitate the societal risk planning policy an investigation was carried out for the Dutch SEVESO establishments to investigate the possibility of determining a generic uniform population density for the zone between the individual risk contours of 10−5 and 10−6 per year. The indicative limit for the societal risk at this density was not to be exceeded. Also there was to be enough space left for a significantly higher population density outside the individual risk contour of 10−6 per year. The RORISC methodology and the actual data for the 124 Dutch SEVESO establishments were used to determine the generic uniform population density. Based on the data available it can be concluded that the maximum allowed uniform population density in the zone between the individual risk contours of 10−5 and 10−6 per year is lower than one person per hectare. At this density there is no space left for a higher population density outside the individual risk contour of 10−6 per year. For uniform population densities the relative contribution to the societal risk has been found significant up to the individual risk contour of 10−7 per year.

scholarly journals Effects of population density on cauliflower crop (Brassica oleracea L. var. botrytis)

1981 ◽  
Vol 38 (1) ◽  
pp. 1-10
Author(s):  
Keigo Minami ◽  
Ricardo Victoria Fº
Keyword(s):  
Population Density ◽  
Brassica Oleracea ◽  
Plant Population ◽  
Population Densities ◽  
Plant Population Density ◽  
Brassica Oleracea L ◽  
Quality Weight

An experiment was carried out to study the effects of the following population densities cauliflowers (plants per ha): 20,833 (0.60 m x 0.80 m), 25,641 (0.60 m x 0.65 m), ....37.037 (0.60 m x 0.45 m) , 55.555 (.0.60 m x 0.30 m), and 111,111 (0,60 m x 0,15 m) ; variety Snow ball. It was concluded that the effects of plant population density are greater on curd quality (weight and size) than on production per ha. The best plant population density to produce cauliflowers curd for Brazil market is from 20,000 to 25,000 plants/ha while for mini-curd is above 55,000 plants/ha.

Population dynamics and production of a brine shrimp, Parartemia zietziana Sayce (Crustacea : Anostraca), in two salt lakes in westren Victoria, Australia

1977 ◽  
Vol 28 (4) ◽  
pp. 417 ◽  
Author(s):  
R Marchant ◽  
WD Williams
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Temperature Stress ◽  
Brine Shrimp ◽  
Dry Weight ◽  
Salt Lakes ◽  
Confidence Limits ◽  
Length Frequency ◽  
Population Densities ◽  
The Mean

Quantitative samples of P. zietziana were taken monthly for two years from Pink Lake and Lake Cundare. Shrimps were usually contagiously distributed. To reduce error, samples were stratified resulting in confidence limits of 40-50% for the mean population density. Despite this variability, stable trends emerged, and variation was not so great as to mask significant differences. Length-frequency analyses distinguished cohorts; a regression was established between length and dry weight, enabling growth to be estimated from samples. By combining growth with population densities in Allen curves, production was computed. In Pink Lake and Lake Cundare mean pro- duction was 11.3 and 1.0 g dry weight m-2 year-1 respectively. Generally there were two or three generations per year, but time and extent of recruitment were not predictable. Each generation suffered continuous mortality, the death of young shrimps accounting for most of the production. This mortality remains unexplained; there are no significant predators and salinity and temperature stress would occur only during summer.

Grain Yield Gains and Associated Traits in Tropical X Temperate Maize Germplasm Under High and Low Plant Density

2021 ◽  
Author(s):  
Vince Ndou ◽  
Edmore Gasura ◽  
Pauline Chivenge ◽  
John Derera
Keyword(s):  
Population Density ◽  
Grain Yield ◽  
Plant Density ◽  
Plant Population ◽  
Population Densities ◽  
Genetic Gains ◽  
Maize Germplasm ◽  
High Plant Density ◽  
Number Of Leaves ◽  
Plant Population Density

Abstract Development of ideal breeding and crop management strategies that can improve maize grain yield under tropical environments is crucial. In the temperate regions, such yield improvements were achieved through use of genotypes that adapt high plant population density stress. However, tropical germplasm has poor tolerance to high plant population density stress, and thus it should be improved by temperate maize. The aim of this study was to estimate the genetic gains and identify traits associated with such gains in stable and high yielding temperate x tropical hybrids under low and high plant population densities. A total of 200 hybrids derived from a line x tester mating design of tropical x temperate germplasm were developed. These hybrids were evaluated for grain yield and allied traits under varied plant population densities. High yielding and stable hybrids, such as 15XH214, 15XH215 and 15XH121 were resistant to lodging and had higher number of leaves above the cob. The high genetic gains of 26% and desirable stress tolerance indices of these hybrids made them better performers over check hybrids under high plant population density. At high plant population density yield was correlated to stem lodging and number of leaves above the cob. Future gains in grain yield of these hybrids derived from temperate x tropical maize germplasm can be achieved by exploiting indirect selection for resistance to stem lodging and increased number of leaves above the cob under high plant density conditions.

Effects of a Transmission Line on Bird Populations in the Red Lake Peatland, Northern Minnesota

The Auk ◽  
1984 ◽  
Vol 101 (3) ◽  
pp. 487-498 ◽  
Author(s):  
Gerald J. Niemi ◽  
JoAnn M. Hanowski
Keyword(s):  
Transmission Line ◽  
Habitat Structure ◽  
Breeding Population ◽  
Habitat Characteristics ◽  
Population Densities ◽  
Yearly Variation ◽  
Bird Populations ◽  
Census Methods ◽  
Habitat Differences ◽  
Transect Counts

Abstract The effects of a 500-kV transmission line on bird populations were assessed by comparing paired treatment areas [which included a transmission line and right-of-way (ROW)] with similar control areas in six different habitat types during the breeding and migration seasons. Habitat structure was measured to examine the inherent differences between control and treatment areas. Using two census methods, territorial mapping and transect counts, we determined that Sedge Wrens and LeConte's Sparrows had lower breeding-population densities in treatment areas than in control areas. LeConte's Sparrows and Connecticut Warblers occurred at greater mean distances from the transmission line in treatment areas than from a similarly positioned line in control areas. Fifteen paired t-tests (five habitats in 3 yr), in which territorial mapping data were used, revealed that community densities were lower in one treatment habitat (high shrub) in 1 of 3 yr (P < 0.05). A two-way analysis of variance with transect counts, however, was not confirmatory when yearly variation was included. Transect counts revealed lower population densities in one treatment habitat (low shrub) in 2 of 3 yr (P < 0.05). In contrast, we observed greater species richness (P < 0.05) in two treatment habitats (closed spruce and sedge fen) than in controls. Treatment habitats were most similar in habitat structure to their paired control habitats, but each habitat of the pair was significantly different (P < 0.05) from the other in at least 2 of 10 habitat characteristics analyzed. We suggest that the avian differences observed between paired areas were primarily attributable to (1) the inherent habitat differences between control and treatment areas, and (2) the new habitat created under the transmission line. Our data indicated negligible effects of this transmission line on bird populations, but interpretations are difficult, because the effects varied with (1) habitat, (2) season, and (3) method considered. Postimpact studies, which compare control and treatment areas, are less effective than before-and-after studies, because differences in habitat structure exist between any two areas.

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