Distributional analysis with line transect methodology of the distance sampling techniques: Case of large mammals of the Mole National Park (MNP) of Ghana

AbstractHistorically, the onager or Persian wild ass Equus hemionus onager, endemic to Iran, was widespread on the arid and semi-arid central steppes but only two natural populations remain. We estimated the population density of the onager in Qatruiyeh National Park using line transect distance sampling. Transects were surveyed on three plains in the Park and the results compared with total counts conducted by the Department of Environment. Our estimate (109 onagers per 100 km2; 95% confidence interval 67–179) is similar to that obtained by the total counts (137 onagers per 100 km2). Distance sampling is therefore a promising method for estimating the abundance of the onager. Using the annual censuses performed by the Department of Environment over the last 13 years we estimated that the population has a growth rate of 0.09. During the same period the onager population in the Touran Protected Complex has experienced a severe decline. The high density of onagers within the National Park indicates the unsuitability of adjacent habitats, including Bahram-e-Goor Protected Area, for this species. Lack of sufficient security and poorly distributed water sources appear to be the main reasons discouraging onagers from entering the Bahram-e-Goor Protected Area. We recommend and describe management interventions that could potentially assist in maintaining the last surviving onager populations in Iran.

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Application of distance sampling to estimate population densities of large herbivores in Kruger National Park

Wildlife Research ◽

10.1071/wr07084 ◽

2008 ◽

Vol 35 (4) ◽

pp. 371 ◽

Cited By ~ 26

Author(s):

J. M. Kruger ◽

B. K. Reilly ◽

I. J. Whyte

Keyword(s):

National Park ◽

Distance Sampling ◽

Kruger National Park ◽

Population Trends ◽

Population Estimates ◽

Line Transect ◽

Large Herbivores ◽

Sampling Intensity ◽

Coefficients Of Variation ◽

White Rhinoceros

Aerial surveys have been used in the Kruger National Park, South Africa, to count large ungulates since the late 1970s. After 1998, aerial line-transect sampling using fixed-wing aircraft and Distance analyses replaced the ‘total’ counting method. This paper investigates these methods and three sampling intensities for estimating the densities of nine large ungulate species in Kruger National Park. Estimates suitable for the detection of population trends and making management decisions were decided by examination of coefficients of variation (set <20%, a priori). Despite the likely violation of some key assumptions of Distance sampling methods, analyses gave population estimates with adequate coefficients of variation for monitoring trends in impala, giraffe, zebra, kudu, white rhinoceros, and elephant bull populations. Significant improvements in precision were obtained at higher sampling intensities for kudu, giraffe, bull elephants and white rhinoceros, but these species already had sufficiently precise population estimates for the detection of trends at the lowest sampling intensity (15%). The estimates for warthog, wildebeest and waterbuck populations were, however, insufficiently precise for assessing population trends. Increasing sampling intensity to 22% and higher did not significantly increase the precision of the Distance estimates for these species. Shortcomings in interpretation of the data caused by violations of critical assumptions of analyses are identified and discussed.

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Getting the Most From Surveys: How Method Selection and Method Modification Impact Butterfly Survey Data

Annals of the Entomological Society of America ◽

10.1093/aesa/saab004 ◽

2021 ◽

Author(s):

Katherine C Kral-O’Brien ◽

Adrienne K Antonsen ◽

Torre J Hovick ◽

Ryan F Limb ◽

Jason P Harmon

Keyword(s):

Species Richness ◽

New Species ◽

Count Data ◽

Distance Sampling ◽

Line Transect ◽

Similar Species ◽

Method Selection ◽

M 10 ◽

Sampling Procedures

Abstract Many methods are used to survey butterfly populations, with line transect and area surveys being prominent. Observers are typically limited to search within 5 or 10 m from the line, while observers are unrestricted in larger specified search regions in area surveys. Although methods differ slightly, the selection is often based on producing defendable data for conservation, maximizing data quality, and minimizing effort. To guide method selection, we compared butterfly surveys using 1) line versus area methods and 2) varying width transects (5 m, 10 m, or unrestricted) using count data from surveys in North Dakota from 2015 to 2018. Between line and area surveys, we detected more individuals with area surveys, even when accounting for effort. However, both methods accumulated new species at similar rates. When comparing transect methodology, we detected nearly 60% more individuals and nine more species when transect width increased from 5 m to unrestricted, despite similar effort across methodology. Overall, we found line surveys slightly less efficient at detecting individuals, but they collected similar species richness to area surveys when accounting for effort. Additionally, line surveys allow the use of unrestricted-width transects with distance sampling procedures, which were more effective at detecting species and individuals while providing a means to correct count data over the same transect length. Methods that reduce effort and accurately depict communities are especially important for conservation when long-term datasets are unavailable.

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Bridled Quail-dove Geotrygon mystacea population assessment after hurricanes Irma and Maria, St. Eustatius, Caribbean Netherlands

Bird Conservation International ◽

10.1017/s0959270920000647 ◽

2021 ◽

pp. 1-12

Author(s):

FRANK F. RIVERA-MILÁN ◽

HANNAH MADDEN ◽

KEVIN VERDEL

Keyword(s):

National Park ◽

Food Limitation ◽

Distance Sampling ◽

Population Status ◽

Management Actions ◽

Abundance Estimates ◽

Detection Mode ◽

Limited Food ◽

Seed Eating ◽

Free Ranging

Summary Structural vegetation damage and food limitation are important effects of major hurricanes, particularly for fruit/seed-eating, forest-dependent Caribbean birds with restricted distributions and small populations, such as the Bridled Quail-dove Geotrygon mystacea. Motivated by the lack of abundance estimates, corrected for detection probability, we conducted distance-sampling surveys inside and outside the Quill National Park each May in 2016-2019. Detection mode was the most important covariate, with others receiving no support from the data. Detectability of available single individuals and clusters of individuals within 60 m of transect centrelines averaged 0.957 ± 0.114 standard error for audio detections, 0.434 ± 0.052 for visual detections, and 0.693 ± 0.064 for detection modes combined. Availability averaged 0.475 ± 0.138 and the product of detectability and availability averaged 0.329 ± 0.098. Density averaged 1.459 ± 0.277 individuals ha-1 and population size averaged 642 ± 122 individuals in 440 ha. Density did not differ along and away from forest trails, but was higher inside than outside the park and at elevations within 201-400 m than 100-200 m and 401-600 m. Density declined by 76% after hurricanes Irma and Maria in 2017. We suggest that major hurricanes together with free-ranging livestock overgrazing degraded foraging habitats, limited food supply, and caused a population bottleneck. Our methodology can be implemented across the distribution range to assess population status and trends and evaluate the result of management actions at key conservation sites. Bridled Quail-dove populations probably were declining on most islands before the 2017 hurricanes and population status warrants revision.

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Harbor porpoise (Phocoena phocoena) recovery in the inland waters of Washington: estimates of density and abundance from aerial surveys, 2013–2015

Canadian Journal of Zoology ◽

10.1139/cjz-2015-0236 ◽

2016 ◽

Vol 94 (7) ◽

pp. 505-515 ◽

Cited By ~ 3

Author(s):

Thomas A. Jefferson ◽

Mari A. Smultea ◽

Sarah S. Courbis ◽

Gregory S. Campbell

Keyword(s):

Puget Sound ◽

Distance Sampling ◽

Line Transect ◽

Inland Waters ◽

San Juan ◽

Phocoena Phocoena ◽

Harbor Porpoise ◽

San Juan Islands ◽

Juan De Fuca ◽

Harbor Porpoises

The harbor porpoise (Phocoena phocoena (L., 1758)) used to be common in Puget Sound, Washington, but virtually disappeared from these waters by the 1970s. We conducted systematic aerial line-transect surveys (17 237 km total effort) for harbor porpoises, with the goal of estimating density and abundance in the inland waters of Washington State. Surveys in Puget Sound occurred throughout the year from 2013 to 2015, and in the Strait of Juan de Fuca and the San Juan Islands (and some adjacent Canadian waters) in April 2015. We used a high-wing, twin-engine Partenavia airplane and four observers (one on each side of the plane, one looking through a belly port, and one recording data). A total of 1063 harbor porpoise groups were sighted. Density and abundance were estimated using conventional distance sampling methods. Analyses were limited to 447 harbor porpoise groups observed during 5708 km of effort during good sighting conditions suitable for line-transect analysis. Harbor porpoises occurred in all regions of the study area, with highest densities around the San Juan Islands and in northern Puget Sound. Overall, estimated abundance for the Washington Inland Waters stock was 11 233 porpoises (CV = 37%, 95% CI = 9 616 – 13 120). This project clearly demonstrated that harbor porpoises have reoccupied waters of Puget Sound and are present there in all seasons. However, the specific reasons for their initial decline and subsequent recovery remain uncertain.

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The importance of survey design in distance sampling: field evaluation using domestic sheep

Wildlife Research ◽

10.1071/wr10234 ◽

2011 ◽

Vol 38 (3) ◽

pp. 221 ◽

Cited By ~ 6

Author(s):

Tom A. Porteus ◽

Suzanne M. Richardson ◽

Jonathan C. Reynolds

Keyword(s):

Population Size ◽

Survey Design ◽

Distance Sampling ◽

Field Evaluation ◽

Stage I ◽

Stage Ii ◽

Line Transect ◽

Domestic Sheep ◽

Management Decisions ◽

Mobile Species

Context Sampling methods to estimate animal density require good survey design to ensure assumptions are met and sampling is representative of the survey area. Management decisions are often made based on these estimates. However, without knowledge of true population size it is not possible for wildlife biologists to evaluate how biased the estimates can be if survey design is compromised. Aims Our aims were to use distance sampling to estimate population size for domestic sheep free-ranging within large enclosed areas of hill country and, by comparing estimates against actual numbers, examine how bias and precision are impaired when survey design is compromised. Methods We used both line and point transect sampling to derive estimates of density for sheep on four farms in upland England. In Stage I we used limited effort and different transect types to compromise survey design. In Stage II we increased effort in an attempt to improve on the Stage I estimates. We also examined the influence of a walking observer on sheep behaviour to assess compliance with distance sampling assumptions and to improve the fit of models to the data. Key results Our results show that distance sampling can lead to biased and imprecise density estimates if survey design is poor, particularly when sampling high density and mobile species that respond to observer presence. In Stage I, walked line transects were least biased; point transects were most biased. Increased effort in Stage II reduced the bias in walked line transect estimates. For all estimates, the actual density was within the derived 95% confidence intervals, but some of these spanned a range of over 100 sheep per km2. Conclusions Using a population of known size, we showed that survey design is vitally important in achieving unbiased and precise density estimation using distance sampling. Adequate transect replication reduced the bias considerably within a compromised survey design. Implications Management decisions based on poorly designed surveys must be made with an appropriate understanding of estimate uncertainty. Failure to do this may lead to ineffective management.

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The influence of animal mobility on the assumption of uniform distances in aerial line-transect surveys

Wildlife Research ◽

10.1071/wr07077 ◽

2008 ◽

Vol 35 (4) ◽

pp. 275 ◽

Cited By ~ 31

Author(s):

Rachel M. Fewster ◽

Colin Southwell ◽

David L. Borchers ◽

Stephen T. Buckland ◽

Anthony R. Pople

Keyword(s):

Survey Design ◽

Distance Sampling ◽

High Mobility ◽

Line Transect ◽

Transect Line ◽

Aerial Surveys ◽

Pack Ice ◽

Capture Recapture ◽

Distance Data ◽

Crabeater Seals

Line-transect distance sampling is a widely used method for estimating animal density from aerial surveys. Analysis of line-transect distance data usually relies on a requirement that the statistical distribution of distances of animal groups from the transect line is uniform. We show that this requirement is satisfied by the survey design if all other assumptions of distance sampling hold, but it can be violated by consistent survey problems such as responsive movement of the animals towards or away from the observer. We hypothesise that problems with the uniform requirement are unlikely to be encountered for immobile taxa, but might become substantial for species of high mobility. We test evidence for non-uniformity using double-observer distance data from two aerial surveys of five species with a spectrum of mobility capabilities and tendencies. No clear evidence against uniformity was found for crabeater seals or emperor penguins on the pack-ice in East Antarctica, while minor non-uniformity consistent with responsive movement up to 30 m was found for Adelie penguins. Strong evidence of either non-uniformity or a failure of the capture–recapture validating method was found for eastern grey kangaroos and red kangaroos in Queensland.

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Mistletoes, their host plants and the effects of browsing by large mammals in Addo Elephant National Park

Koedoe ◽

10.4102/koedoe.v34i2.430 ◽

1991 ◽

Vol 34 (2) ◽

Cited By ~ 13

Author(s):

J.J. Midgley ◽

D. Joubert

Keyword(s):

National Park ◽

Host Plants ◽

Large Mammals ◽

Plant Parasites

There are at least four plant hemiparasites [=mistletoes, viz. Viscaceae (3 species), Loranthaceae (1 species)] within the Addo Elephant National Park. Highly selective utilisation of these plant parasites by large browsing animals has resulted in severe decline of these plants within the elephant enclosure. The parasites are often associated with spinescent host plants. We suggest this has less to do with escaping herbivory by large mammals and more to do with spinescent plants being optimum hosts because they are a richer nutritient source for plant parasites than most non-spinescent plants.

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The large mammals of the Kruger National Park - Their distribution and present-day status

Koedoe ◽

10.4102/koedoe.v6i1.810 ◽

1963 ◽

Vol 6 (1) ◽

Cited By ~ 14

Author(s):

U. De V. Pienaar

Keyword(s):

National Park ◽

Kruger National Park ◽

Large Mammals

The large mammals of the Kruger National Park - Their distribution and present-day status

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KEPADATAN POPULASI MAMALIA DARAT KARNIVORA DI CAMP LEAKEY KAWASAN TAMAN NASIONAL TANJUNG PUTING, KALIMANTAN TENGAH

Jurnal BIOMA ◽

10.21009/bioma12(2).3 ◽

2017 ◽

Vol 12 (2) ◽

pp. 83

Author(s):

Siwi Arthapati Mandiri ◽

Paskal Sukandar ◽

Yossa Istiadi

Keyword(s):

Data Collection ◽

Population Density ◽

National Park ◽

Line Transect ◽

Line Transect Sampling ◽

Clouded Leopard ◽

Helarctos Malayanus ◽

Transect Sampling ◽

Palm Civet ◽

Leopard Cat

Borneo has wide land that support high biodiversity. One of them is Tanjung Puting National Park (TPNP), which have biodiversity such as terrestrial mammalian carnivore. Carnivore has a role to maintain its ecosystems. But, there are no data for population density of terrestrial mammalian carnivore. The object of this research is to find out population density of terrestrial mammalian carnivore in Camp Leakey, TPNP, Central Borneo. This research accomplished in September-October 2015 in Camp Leakey. Using line-transect sampling. Data collection was accomplished at 18.00-24.00 Central Indonesian Time (WITA) on eight transects with three times replication by direct surveys and indirect surveys. This research has obtained five species, malayan sun bear (Helarctos malayanus), sunda clouded leopard (Neofelis diardi), leopard cat, and group of civet, like small-toothed palm civet (Arctogalidia trivirgata) and asian palm civet (Paradoxurus hermaphroditus). Population density of each species from the highest to the lowest is 13,5 Individual of leopard cat/km2, 9,84 Individual of malayan sun bears/km2, 4,31 Individual of sunda clouded leopard/km2, and 3,65 Individual of civet/km2. Malayan sun bears, sunda clouded leopards and civets prefer to be in land forest. Leopard cats prefers to be in transition forest.

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