The control of feral goats (Capra hircus) and relevant aspects of their biology were studied on Aldabra Atoll, Republic of Seychelles, from October 1993 - May 1994 and November 1994 - May 1995. A total of 832 goats were killed on Aldabra using both the Judas goat technique and traditional hunting methods; a total of 28 Judas goats were used during the entire campaign. The remnant goat populations on Ile Picard (N=13) and Ile Malabar (N=19) were eradicated during the first season. On Grande Terre, a total of 798 (374 M: 424 F) goats were killed. The overall kill rate on Grande Terre was 0.37 goats killed/hour with 1.66 shots fired/goat. A total of 1,042 goats were encountered of which 26.1% escaped. Mean group size was 3.2 with a range of 1 to 20. Judas goat hunting became increasingly important over time with 18.0% (n=85) of goats killed in the first season being in the presence of Judas goats; 42.3% (n=126) of goats killed during the second season were in the presence of Judas goats. The overall kill rate for the project was almost 2 times greater for Judas goat hunting (0.61 goats killed/hr) than traditional hunting (0.32 goats killed/hr); Judas goat hunting was approximately 70% more effective than traditional hunting when compared using multiple linear regression. There was a significant relationship between Judas goat home range size and the number of conspecifics killed. Feral goats on Aldabra may be unique among feral goat populations by apparently not responding to population reductions in a density-dependent manner. For the first season, the intrinsic rate of increase (r) was 0.45; r=0.39 for the second season. Twinning rates were 30.7% and 37.5% in the first and second seasons, respectively. I subjectively estimated approximately 60-120 goats remaining on all of Grande Terre at the end of the project; 84 goats were estimated using the Leslie-Davis removal method of population estimation. / Graduation date: 1998

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

A vegetation assessment was conducted to understand the effect of feral goats (Capra hircus) on the vegetation of Isolated Hill Scenic Reserve located in Southern Marlborough. New Zealand forests evolved without the pressure of mammalian herbivores but following human settlement they became subject to intensive browsing following the introduction of exotic mammals. This study focuses on the presence of feral goats. Interest arises from the settlement of other countries and the subsequent liberations of feral goats which are now considered to be responsible for the significant removal of native vegetation as well as playing a dominant role in erosion. Changes in plant communities have occurred with the pressure of goat browsing as well as secondary effects such as habitat degradation The purpose of this research was to investigate the changes in plant species composition since the initial and subsequent research conducted in 1985 and 1994. An analysis of previous work on the diet of multiple introduced ungulate species was also conducted. Previous studies were not limited to only feral goat studies and included other introduced herbivores to provide a broad overview of diets. The New Zealand Forest Service implemented a programme for monitoring the seral forest in Isolated Hill Scenic Reserve using standard Forest Service vegetation quadrants. 32 quadrants were established, including three exclosures, in various locations around the Reserve to allow assessment of feral goat impacts on seral forests (forest whose constituents are of varied age classes). Nine forest service plots, including three exclosures were re-measured and an additional nine plots were measured. Given the progression of vegetation change that has been observed during the course of this study, both analytically and observationally, Isolated Hill Scenic Reserve in its current state, involving the notable presence of feral goats and the vegetation types will continue to diminish in diversity.

(1) Reliable measures of population abundance are essential for managing wildlife effectively. Aerial surveys provide a rapid and efficient means of surveying large mammals and many techniques have been developed to adjust for the inability to count all animals within transects. The probability of detection varies according to a range of factors which are important to consider when estimating density. Standardised survey methods developed in flat country are not readily transferable to steep terrain due to safety, access and difficulties delineating transect widths. Other methods have logistic constraints and must adhere to various other assumptions. (2) Density estimators are seldom examined using actual population size, hence their ability to correct for true bias is unknown. Studies that compare techniques are difficult to interpret because of the uncertainty of adherence to their respective assumptions. Factors influencing detection probability, estimators that correct for bias, the validity of their assumptions and how these relate to true density are important considerations for selecting suitable methods. The aim of this study was to obtain accurate and reliable methods for estimating the density of feral goats by improving predictions of detection probability, investigating the assumptions of aerial surveys, and examining the accuracy of 15 density estimators by comparing with total counts of feral goats. (3) Group size, vegetation and observer were the most important factors influencing the probability of observing a group of goats during aerial surveys. However, different approaches to analysing these data influenced the significance of variables and the predicted probabilities. Goat colour, type of helicopter, site and rear observer experience in hours were also found to be significant (P<0.05) when using likelihood equations based on all animals in the population rather than only those in the sample. The slope of the terrain was also shown to significantly (P=0.014) affect the probability of detection. (4) Indices are commonly used in wildlife management for their simplicity and practicality, but their validity has been questioned because of variable probability of detection. Results of this study suggest aerial survey indices are useful in monitoring a range of medium-sized mammal species across space and time if differences in detection probability between species, group size, vegetation and observer are considered and their effects are standardised. (5) An assumption of most sampling regimes that is fundamental but rarely examined is that animals are not counted more than once. In this study the behavioural responses of feral goats to helicopters were investigated as a basis for estimating the probability that goats were recounted. No long-term consequences were evident in feral goat behaviour of responses to helicopters. However, helicopter surveys were found to alter the structure of 42% of groups observed, with 28% of groups merging with others and 14% splitting into separate groups. Therefore, group size estimated from the air should not be considered as biologically important, and when estimating density, researchers should also avoid using group sizes determined from independent ground observations to correct group sizes determined from aerial surveys. Goats were also more likely to flush further when helicopters were within 150 m, which is close to or within standard helicopter strip widths. Substantial movement occurred between transects and 21% of goats were estimated to be available for recounting in adjacent transects. (6) Different detection probabilities between groups of goats may be particularly relevant when using double-counting, where multiple observers are �capturing� and �recapturing� animals in the same instant. Many analyses test and adjust for this �unequal catchability� assumption in different ways, with the approaches of Huggins and Alho allowing prediction of unique probability values for a range of co-variates. The approach of Chao attempts to correct for skewed distributions in small samples. The Horvitz-Thompson approach provides a useful basis for estimating abundance (or density) when detection probability can be estimated and is known to vary between observations according to a range of independent variables, and also avoids errors associated with averaging group size. (7) After correcting for recounting, the Alho estimator applied to helicopter surveys was the most accurate (Bias = 0.02) and reliable of all techniques, which suggests that estimates were improved by taking into account unconditional detection probability and correcting individual observations according to their characteristics. The positive bias evident in the Chao (Bias = 0.28) and Petersen (Bias = 0.15) aerial survey estimators may have been a result of averaging detection probability across all observations. The inconsistency and inaccuracy of the ground-based area-count technique emphasises the importance of other assumptions in density estimation, such as representative sampling and availability bias. The accuracy of index-manipulation-index techniques was dependent on the indices used. Capture-recapture estimates using mustering showed slight negative bias (Bias = -0.08), which was likely a result of increased probability of re-capture (i.e. trap happy). Ground-based capture-resight estimates were labour intensive and positively biased (Bias = 0.13), likely due to underestimating the area sampled, or overestimating the number of unmarked individuals with each sample. (8) Helicopter survey using double-counting is recommended for estimating the density of feral goats in steep terrain. However, consideration of recounting under intensive sampling regimes and adjustments for the factors that influence unconditional detection probability is required.

Merino sheep are the most numerous domestic livestock in Australia and feral goats are wide-spread and locally abundant in many of the regions where sheep are grazed. Foot and mouth disease (FMD) is a disease of ungulates that causes severe economic hardship to countries where outbreaks occur or where it has become endemic. In India, Africa, Greece and recently the United Kingdom and Eire, sheep and goats have been implicated in the spread and maintenance of FMD. In Australia, there are contingency plans (AUSVETPLANS) for dealing with an outbreak of FMD. Included in those plans are strategies for control of the disease in feral ungulates including feral pigs and feral goats. Modelling has provided assistance in developing strategies to combat outbreaks in feral pigs and for controlling outbreaks in domestic livestock. No models have been constructed to aid decisions about controlling FMD in feral goats where they co-occur with merino sheep. In Australia, the greatest densities of free-ranging feral goats and domestic livestock occur in the high rainfall zone (> 500 mm mean annual rainfall) along the eastern tablelands and adjacent slopes of the Great Dividing Range. Previous studies of feral goat biology, population dynamics and behaviour in Australia have concentrated on arid and semi-arid zones or on islands. Interactions between free ranging feral goats and merino sheep have not previously been studied in the high rainfall zone. My study investigated the ecological and behavioural characteristics of feral goats and their interactions with sympatric merino sheep at a high rainfall site in central eastern New South Wales. The population dynamics, biological and behavioural parameters of feral goats and sheep were then used to model FMD in such an environment. Deterministic temporal models and a new spatial stochastic model were used. Of particular interest were the rates of contact within and between subgroups of feral goats (termed herds and mobs), within and between subgroups of merino sheep (termed flocks and mobs), and between subgroups of the two species. Feral goats at the study site were found to be numerous (mean density = 34.94 goats km-2, from aerial surveys), in good condition, fecund and had high adult survival and low annual adult mortality (survival= 0.81�1.00) in the absence of harvesting and hunting. They had an observed instantaneous rate of increase of 0.112 per year. Annual rate of increase was similar to other sites in Australia without sustained harvesting pressure. Home ranges were small for both males (3.754 km², s.e. = 0.232, n = 116 goats) and females (2.369 km², s.e. = 0.088, n = 241 goats). From this and other Australasian studies, an inverse power function was found to be an excellent descriptor of the relationship between mean annual rainfall and female home range size. A resource selection function was fitted in a geographic information system to observational data of feral goats. The habitat selection of feral goats included a preference for wooded vegetation on eastern and north eastern aspects at higher elevations. The resource selection function was also used to set the probabilities of occurrence of feral goats in 1 ha areas of the landscape and these probabilities were used to generate heterogeneity in a spatial model of foot and mouth disease virus (FMDV) transmission. Daily per capita contact rates were estimated from observed contacts in the field where a contact between individuals was recognised when one approached within 1 body length ([approx] 1m) of another. The contacts between feral goats within herds were frequent and occurred at a rate of 6.96 (s.e. = 1.27) goat�goat contacts day-1. Sheep to sheep contacts were slightly less frequent (4.22 sheep�sheep contacts day-1, s.e. = 0.65) but both estimates were most likely negatively biased because of observer errors in estimating the number of individual animals coming in contact with observation subject (focal) animals. Contacts between herds of feral goats were not common and those between adjacent populations were fewer than 1 per year. In sheep, flock to flock contact was largely governed by husbandry practices and occurred at a mean daily rate of 0.0014 flock�flock contacts. Contacts between sheep and feral goats were less frequent but nonetheless common (2.82 goat�sheep contacts day-1, s.e. = 0.40). In feral goats the size of the mob in which focal goats were observed was found to be the most important factor in determining contact rates between individuals and a counter-intuitive inverse relationship was identified. Contacts were heterogeneous and density was not an important determinant of contact rates implying that, because of the uniformly high densities at the site, saturation had occurred. The temporal models of FMDV transmission showed that the rate of contact within and between species was such that FMD was predicted to spread rapidly throughout an infected herd or flock. Control strategies of intense culling of feral goats at the population level were predicted to allow the disease to persist at low prevalence, with a small peak corresponding to the annual lambing pulse in sheep. However, the same level of control (>90% reduction) at the herd level was predicted to eliminate FMD and allow the safe reintroduction of sheep. Extreme control that left very small groups (<3 individuals) may be counter productive because such small groups are likely to join the reintroduced sheep in an effort by the goats to meet gregarious urges. The spatial model was more reassuring. It predicted that FMD would die out in a mixed sheep and feral goat population in less than 90 days because of the low rate of herd to herd contact and herd to flock contact. For similar environments, the contingency planning consequences are that an outbreak of FMD introduced into feral goats from sympatric sheep is likely to be containable by removing all the sheep, determining the extent and likely range of the feral goats, then removing a substantial proportion of or eradicating each herd. Feral goats, being relatively sedentary, are unlikely to spread to adjacent populations and the disease will die out through lack of contact between herds and populations. Because feral goat home ranges overlap and are centred on one or two small catchments, a containment ring of feral goat control, set to encompass the home range of a target herd and that of adjacent herds, should be adequate to limit spread of FMD.

The ability of feral herbivores to reduce the amount of food available to domestic livestock has rarely been quantified. This thesis seeks to examine the degree to which feral goats (Capra hircus) reduce the availability of pasture and shrub biomass for other herbivores. The interaction between feral goat populations and their food supply will be explored using a modelling approach. In addition to this it will also examine the cost of controlling goats and attempt to identify the cost efficient target densities for control operations. The implications of this information for management will be discussed. There are two ways an animal population can interact with its food supply, through: (1) intrinsic food shortages, and (2) extrinsic food shortages. Intrinsic food shortages occur when a negative feed-back loop exists between the animal population and their food supply. This means the animals affect the availability of their food and their food supply affects the dynamics of the animal population. Since the animals are affecting their own food supply it could be said that they will also affect the availability of that food to other herbivores if they consume the same species. Extrinsic food shortages occur when there is no feed-back from the animals to their food supply. Food availability is determined by extrinsic factors such as rainfall and is unaffected by the animal population. To determine how feral goats interact with their food supply several models will be examined, and these include: (1) single species models which use data from the animal population only. These have historically been used to identify density dependence which is commonly caused by the animal population being regulated through their food supply in the case of large herbivores, and (2) trophic models which incorporate data from at least two trophic levels in an ecosystem, in this case those being the animal population and the vegetation they are thought to consume. These models allow a more direct examination of the relationship between the feral goat population and their food supply. The various models were fitted to data collected on the field sites and the following results were obtained: (1) the dynamics of the feral goat populations could not be represented by single-species models. This was most probably due to the stochastic environment in which they lived causing the level of density dependence experienced by the goats to vary greatly masking its presence. (2) the rate of increase of the goat population could be predicted by the numerical response of rate of increase to pasture biomass. This demonstrated that food availability influenced the dynamics of the goat population. (3) goat density affected the availability of some species of shrub biomass. There was, however, no response seen in the availability of pasture species to changes in goat density. Since the study was conducted during a drought this is in agreement with other studies which indicated that goats will primarily browse during dry spells but switch to pasture species when conditions improve following rainfall. These results indicate that a negative feed-back loop does exist between feral goat populations and their food supply since the goats affected the availability of some shrub species and so they suffer intrinsic food shortages. This means goats have the ability to reduce the availability of food to other herbivores providing both are eating the same species. Cost-efficiency analysis showed that the cost of removing individual feral goats increases exponentially as density decreases because the search time per animal becomes greater. This relationship was used to construct a model that predicted the cost of achieving a target density. The model describing cost of control over density was also combined with a productivity model based on the numerical response of feral goats to pasture biomass to predict the cost of maintaining target densities under different environmental conditions. Using these models the most cost-efficient density identified was 11 goats/km2. From this study we can make the following conclusions: (1) feral goats have the ability to reduce the amount of shrub biomass available to other herbivores during dry conditions (2) their ability to influence the availability of pasture species remains unknown (3) given the cost of initial and ongoing control and the minimal benefits that result it would be difficult to justify controlling goats during a drought on the field sites.

Thesis (M. Appl. Sci.)--University of Canberra, 2004. / Title from PDF title page (viewed on July 20, 2005). Includes bibliographical references (p. 129-146).