Estimating distribution and abundance of feral horses (Equus caballus) in a coniferous plantation in Australia, using line-transect surveys of dung

2016 ◽  
Vol 43 (7) ◽  
pp. 604 ◽  
Author(s):  
Magdalena A. Zabek ◽  
David M. Berman ◽  
Simon Blomberg ◽  
John Wright
Keyword(s):  
Population Distribution ◽  
Decay Rates ◽  
Line Transect ◽  
Population Abundance ◽  
Horse Population ◽  
Feral Horses ◽  
Feral Horse ◽  
Coniferous Plantation ◽  
The Mean ◽  
Strip Transect

Context Feral horses are a growing problem in Australia, despite implementation of management strategies. The incidence of horse sightings and horse-associated vehicle collisions within the Tuan and Toolara State Forest (TTSF), a coniferous plantation in south-eastern Queensland, has increased in the past decade, indicating an increase in population and the necessity to undertake an accurate appraisal of population abundance. Aim To determine the feasibility of using dung counts, defecation and dung-decay rates to determine the distribution and abundance of feral horse population in a managed coniferous plantation where dense vegetation prohibits the use of visual-based animal detection methods. Methods Population distribution was assessed by dung count incorporated into a vehicle strip-transect survey on 582 km of forest tracks. Population abundance was estimated from dung density, the mean defecation frequency of feral horses, and the mean number of days required for dung to decay. Dung density was obtained from on-ground distance line-transect survey that sampled all representative plantation habitats and consisted of 111 transects totalling 44.3 km. Key results The strip-transect survey clearly showed that although feral horses were dispersed across the plantation, the distribution was uneven, with the central region of the plantation being the most heavily populated. The combination of dung counts, defecation rate (mean ± s.d., 7.97 ± 8.74) over 24 h and dung-decay rate (444 ± 150.7 days) provided an estimation of the density of feral horses in various habitats and indicated that the plantation was occupied by 1321 (95% CI 940–1965) horses, which corresponded to an average density of 1.8 horses km–2. The method clearly identified variations in horse abundance among the various habitats within the surveyed areas. Open habitats, created following harvesting, showed higher occurrence rates, whereas the habitats of mature forest were scantily occupied. Key conclusions Dung counts are a simple, effective and practical technique that can provide information on distribution and abundance of feral horse population in densely forested habitats where visual-based techniques are not applicable. However, unbiased and precise defecation and decay rates must be estimated. Implications The study validated the use of dung counts to provide information on feral horse distribution and abundance in densely forested environments where direct methods of census may be difficult to obtain. The methods are applicable to a range of ecosystems, but defecation and dung-decay rates must be determined separately for each ecosystem.

Seasonal mountain lion predation on a feral horse population

1992 ◽  
Vol 70 (5) ◽  
pp. 929-934 ◽  
Author(s):  
John W. Turner Jr. ◽  
Michael L. Wolfe ◽  
Jay F. Kirkpatrick
Keyword(s):  
Survival Rate ◽  
First Year ◽  
Horse Population ◽  
Feral Horses ◽  
Mountain Lions ◽  
Mountain Lion ◽  
Felis Concolor ◽  
Feral Horse ◽  
Annual Cohort ◽  
Demographic Impact

A population of feral horses (Equus caballus) was studied from 1986 to 1991 to determine the demographic impact of predation by the mountain lion (Felis concolor). The population, inhabiting a 600-km2 area on the central California – Nevada border comprised approximately 162 individuals > 1 year old, with an average of 9 yearlings, 8 two-year-olds, and 144 adults. Numbers of horses varied by only 4–8% and showed no consistent trend. The parturition peak spanned May and June, when 80% of foaling occurred. One-third of the average annual cohort of 33 foals was missing by July and only half of the cohort remained by October. The mean first-year survival rate estimated from the differential incidence of foals and yearlings in successive years was 0.27, which was less than one-third of the foal survival rate reported for other feral horse populations. A minimum of four adult mountain lions used the study area each year between May and October. Of 28 foal carcasses located from May to mid-July, at least 82% were the result of mountain lion kills. No evidence of predation on older horses was observed, but mountain lions preyed on mule deer (Odocoileus hemionus) during winter. We conclude that the growth of this horse population is limited by predation.

scholarly journals Feral Horse Distribution, Habitat Use and Population Dynamics in Theodore Roosevelt National Park

1990 ◽  
Vol 14 ◽  
pp. 123-125
Author(s):  
Clayton Marlow ◽  
Leonard Gagnon ◽  
Elena Hovland ◽  
Lynn Irby
Keyword(s):  
National Park ◽  
Home Range Size ◽  
Home Ranges ◽  
Theodore Roosevelt ◽  
Horse Population ◽  
Feral Horses ◽  
Population Growth Rates ◽  
Feral Horse ◽  
Theodore Roosevelt National Park ◽  
Reproductive Rates

Description of the ecological niche feral horses fill in Theodore Roosevelt National Park requires information on reproductive rates, home range size, individual and band affinity to home ranges, food and shelter requirements and seasonal diets. Therefore, the initial objectives will be to: 1. identify the number, size and location of home ranges for harem and bachelor stallion bands; 2. describe daily and seasonal movements of bands within identified home ranges; 3. describe the vegetation habitat types and landform types used by horses for mating, foaling, foraging, and resting cover; 4. describe seasonal horse diets; and 5. collect data on sex, age and social hierarchy within respective bands to facilitate estimation of horse population growth rates. Ultimately, this information will be used to accomplish the project goal; integrate horse requirements with those of elk, bison and the Park's vegetation communities to determine the large ungulate carrying capacity of Theodore Roosevelt National Park.

Population dynamics of feral horses (Equus caballus) in an exotic coniferous plantation in Australia

2016 ◽  
Vol 43 (4) ◽  
pp. 358 ◽  
Author(s):  
Magdalena A. Zabek ◽  
David M. Berman ◽  
Simon P. Blomberg ◽  
Christina W. Collins ◽  
John Wright
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Body Condition Score ◽  
Equus Caballus ◽  
Population Increase ◽  
Adult Survival ◽  
Feral Horses ◽  
Adult Females ◽  
Coniferous Plantation ◽  
The Mean

Context Understanding population dynamics of invasive species is crucial for the development of management strategies. Feral horses (Equus caballus) are a growing problem in the Tuan–Toolara State Forest (TTSF), a coniferous plantation in south-eastern Queensland, Australia. Aim The population dynamics of the TTSF feral horses was not known. Therefore, the study was designed to characterise the major vital parameters of this population and, using these data, develop a long-term management plan. Methods The study was conducted over 3 years (2011–14) involving 522 individually identified horses. Foaling rates were used to calculate fecundity. Body fat distribution was estimated using body condition score (BCS), which reflects the nutritional, metabolic and general health of individual animals. Multi state mark–capture population models were used to estimate age-specific survival, and the Leslie age-structured projection matrix model was used to determine the annual rate at which the population increased. Key results The mean annual fecundity was low (0.23 ± 0.07 s.d.). The mean BCS of the population was mid-range (2.55 ± 0.51 s.d.) with adult females having lower scores than other age and gender groups. Survival estimates were consistently high (0.92–0.95) across all age groups. The average annual finite rate of population increase (λ) for the 3 years of the study was 1.09. Sensitivity analysis demonstrated that the population growth rate was almost seven times more sensitive to changes in adult survival compared with juvenile survival, and almost twice as sensitive to changes in fecundity. Key conclusions Population dynamics of the TTSF feral horses were comparable to other feral horse populations similarly challenged by environmental nutritional limitations. Implications Defining population dynamics of the TTSF feral horses permits the formulation of management goals that can be audited and adapted as required. The most effective strategy for controlling population growth in the TTSF would involve the continuing removal of substantial numbers of adult females or manipulation of survival and/or fecundity. As selective removal will likely alter the adult sex ratio and age structure of the population, ongoing assessment is necessary to minimise adverse welfare outcomes.

Prospects for immunocontraception in feral horse population control: exploring novel targets for an equine fertility vaccine

2016 ◽  
Vol 28 (7) ◽  
pp. 853 ◽  
Author(s):  
Aleona Swegen ◽  
R. John Aitken
Keyword(s):  
Vaccine Development ◽  
Population Control ◽  
Future Research ◽  
Economic Damage ◽  
The Novel ◽  
Horse Population ◽  
Feral Horses ◽  
Feral Horse ◽  
Species Specific ◽  
Free Ranging

Feral horses populate vast land areas and often induce significant ecological and economic damage throughout the landscape. Non-lethal population control methods are considered favourable in light of animal welfare, social and ethical considerations; however, no single effective, safe and species-specific contraceptive agent is currently available for use in free-ranging wild and feral horses. This review explores aspects of equine reproductive physiology that may provide avenues for the development of specific and long-lasting immunocontraceptive vaccines and some of the novel strategies that may be employed to facilitate appropriate antigen discovery in future research. Potential antigen targets pertaining to spermatozoa, the ovary and oocyte, as well as the early conceptus and its associated factors, are reviewed in the context of their suitability for immunocontraceptive vaccine development.

scholarly journals Performance of Parametric Model for Line Transect Data

2020 ◽  
pp. 1-7
Author(s):  
Noryanti Muhammad ◽  
Gamil A.A. Saeed ◽  
Wan Nur Syahidah Wan Yusoff
Keyword(s):  
Simulation Study ◽  
Present Model ◽  
Parametric Model ◽  
Line Transect ◽  
Population Abundance ◽  
Line Transect Sampling ◽  
Detection Function ◽  
Transect Sampling ◽  
Proposed Model ◽  
Shoulder Condition

One of the most important sides of life is wildlife. There is growing research interest in monitoring wildlife. Line transect sampling is one of the techniques widely used for estimating the density of objects especially for animals and plants. In this research, a parametric estimator for estimation of the population abundance is developed. A new parametric model for perpendicular distances for detection function is utilised to develop the estimator. In this paper, the performance of the parametric model which was developed using a simulation study is presented. The detection function has non-increasing curve and a perfect probability at zero. Theoretically, the parametric model which has been developed is guar-anteed to satisfy the shoulder condition assumption. A simulation study is presented to validate the present model. Relative mean error (RME) and Relative Bias (RB) are used to compare the estimator with well-known existing estimators. The results of the simulation study are discussed, and the performance of the proposed model shows promising statistical properties which outperformed the existing models. Keywords: detection function, line transect data, parametric model

scholarly journals Double Kernel Method Using Line Transect Sampling

2016 ◽  
Vol 41 (2) ◽  
Author(s):  
Omar Eidous ◽  
M.K. Shakhatreh
Keyword(s):  
Kernel Method ◽  
Kernel Estimator ◽  
Real Data ◽  
Line Transect ◽  
Population Abundance ◽  
Line Transect Sampling ◽  
Numerical Examples ◽  
Bootstrap Techniques ◽  
Transect Sampling ◽  
Kernel Type

A double kernel method as an alternative to the classical kernel method is proposed to estimate the population abundance by using line transect sampling. The proposed method produces an estimator that is essentially a kernel type of estimator use the kernel estimator twice to improve the performances of the classical kernel estimator. The feasibility of using bootstrap techniques to estimate the bias and variance of the proposed estimator is also addressed. Some numerical examples based on simulated and real data are presented. The results show that the proposed estimator outperforms existingclassical kernel estimator in most considered cases.

A model for the effect of bias for cholesterol on the population at risk.

1988 ◽  
Vol 34 (11) ◽  
pp. 2256-2259 ◽  
Author(s):  
M H Kroll ◽  
M Ruddel ◽  
R J Elin
Keyword(s):  
At Risk ◽  
Standard Deviation ◽  
Reference Values ◽  
Gaussian Distribution ◽  
Population Distribution ◽  
Reference Value ◽  
Mean Value ◽  
The Body ◽  
Methodological Bias ◽  
The Mean

Abstract The location of the Reference Value for an analyte within the population distribution affects the magnitude of error due to methodological bias. Using the gaussian distribution, we evaluated the effects of systematic and proportional biases of the method (positive and negative), mean value, and standard deviation on the magnitude of error. We chose four Reference Values for cholesterol as a model. For a population with a mean of 2.0 and SD of 0.36 g of cholesterol per liter, a 3% positive proportional bias causes sixfold more error at the 50th percentile than at the 97.5th. In general, the error for a given bias (proportional or systematic) is greater for a Reference Value within the body than at the tails of the distribution. Further, the magnitude of the error varies as a function of the mean and standard deviation of the population.

scholarly journals An index framework founded on the future profit potential of female beef cattle to aid the identification of candidates for culling

2020 ◽  
Vol 98 (11) ◽  
Author(s):  
Fíona L Dunne ◽  
Donagh P Berry ◽  
Margaret M Kelleher ◽  
Ross D Evans ◽  
Siobhan W Walsh ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Population Distribution ◽  
Beef Cows ◽  
Calving Interval ◽  
Transition Matrices ◽  
Individual Female ◽  
The Mean ◽  
Carcass Performance ◽  
Expected Longevity ◽  
Profit Potential

Abstract Meticulous culling decisions, coupled with careful breeding decisions, are fundamental to shifting a population distribution in the favorable direction and improving profit per cow. Nevertheless, there is a paucity of easy-to-use dynamic tools to aid in culling decisions in beef cattle. The motivation for the present study was to develop a monetary-based culling tool, here referred to as the Beef Female’s Profit Potential (BFPP), to identify females for culling. The BFPP reflects the expected lifetime profitability of an individual female in a herd for the expected remainder of her lifetime; this profit included that of the beef female herself as well as her progeny. The BFPP index framework was composed of 4 subindexes reflecting the value of an animal: (1) as a nulliparae (this was voided if the cow had already calved), (2) for the remainder of her current parity, (3) summed across each of her expected remaining parities, and (4) when she is retained within the herd and not voluntarily culled. Each subindex was comprised of different components reflecting both genetic and non-genetic effects associated with each female. Transition matrices predicting the expected longevity of each female and their expected month of calving were also utilized in calculating the expected remaining lifetime profitability of each female. The BFPP index was validated on 21,102 beef cows as well as their harvested progeny from 875 herds by stratifying the cows, within herd, into 4 strata based on their BFPP. The mean of the within-herd correlation between the BFPP and the Irish national replacement (i.e., breeding) index was, on average, 0.45 indicating the shortcomings of the breeding index as a culling tool. Cows within the top BFPP stratum had a genetic expectation of accruing almost an additional €36 profit per calving, relative to cows within the worst stratum; when validated on the cow’s own calving interval and survival performance as well as their progeny’s carcass performance, the actual phenotypic value was estimated to be an additional €32 profit per calving. A proportion of this additional profit was due to the harvested progeny of the high BFPP cows having, on average, heavier, more conformed carcasses with less fat cover relative to their poor BFPP contemporaries. This BFPP framework is a useful and easy-to-use tool to aid in producer decision making on the choice of females to voluntarily cull but also on which replacement heifers to graduate into the mature herd.

Causes and consequences of an unusually male‐biased adult sex ratio in an unmanaged feral horse population

2020 ◽  
Vol 89 (12) ◽  
pp. 2909-2921
Author(s):  
Charlotte E. Regan ◽  
Sarah A. Medill ◽  
Jocelyn Poissant ◽  
Philip D. McLoughlin
Keyword(s):  
Sex Ratio ◽  
Horse Population ◽  
Feral Horse ◽  
Adult Sex Ratio
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