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WAYNE L. LINKLATER & ELISSA Z. CAMERON. (2000). Distinguishing cooperation from cohabitation: the feral horse case. Anim. Behav., 59, F17–F21.
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Linklater, W. L., Cameron, E. Z., Stafford, K. J., & Minot, E. O. Estimating Kaimanawa feral horse population size and growth. In SCIENCE & RESEARCH INTERNAL REPORT 185.
Abstract: Animal flight behaviour in response to aircraft could have a profound influence
on the accuracy and precision of aerial estimates of population size but is rarely investigated. Using independent observers on the ground and in the air we recorded the presence and behaviour of 17 groups, including 136 individually marked horses, during a helicopter count in New Zealand’s Kaimanawa Mountains. We also compared the helicopter count with ground-based estimates using mark-resight and line-transect methods in areas ranging from 20.5 to 176 km2. Helicopter counts were from 16% smaller to 54% larger than ground-based estimates. The helicopter induced a flight response in all horse groups monitored. During flight, horse groups traveled from 0.1 up to 2.75 km before leaving the ground observer’s view and temporarily changed in size and composition. A tenth of the horses were not counted and a quarter counted twice. A further 23 (17%) may have been counted twice but only two of the three observers’ records concurred. Thus, the helicopter count over-estimated the marked sub-population by at least 15% and possibly by up to 32%. The net over-estimate of the marked sub-population corresponded to the 17% and 13% difference between helicopter counts and ground-based estimates in the central study area and for the largest area sampled, respectively. Feral horse flight behaviour should be considered when designing methods for population monitoring using aircraft. We identify the characteristics of the helicopter count that motivated horse flight behaviour. We compared our own recent estimate of population growth from measures of fecundity and mortality (λ = 1.096 with an earlier-published one (λ = 1.182, where r = 0.167) that had been derived by interpolating between the available history of single counts. Our model of population growth, standardised aerial counts, and historical estimates of annual reproduction suggest that the historical sequence of counts since 1979 probably over-estimated growth because count techniques improved and greater effort was expended in successive counts. We used line-transect, markresight and dung density sampling methods for population monitoring and discuss their advantages and limitations over helicopter counts. |
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Wakeling, E. (2002). Feral Horses of the West.
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Sharp, T., & Saunders, G. mustering of feral horses.
Abstract: Background
Feral horses (Equus caballus) can cause significant environmental damage and losses to rural industries. Although considered pests, feral horses are also a resource, providing products such as pet meat for the domestic market and meat for human consumption for the export market. Control methods include trapping, mustering exclusion fencing, ground shooting and shooting from helicopters. Feral horses are mustered by helicopter, motorbike or on horseback, sometimes with the assistance of coacher horses. Once mustered into yards, net traps or fenced paddocks, the horses are usually sold to abattoirs for slaughter which can offset the costs of capture and handling. Less commonly, they are sold as riding horses or relocated to reserves or horse sanctuaries. Where there is no market for them or where removal may be too costly or impractical e.g. in conservation areas or remote areas without access to transportation, horses are sometimes destroyed by shooting in the yards. This standard operating procedure (SOP) is a guide only; it does not replace or override the legislation that applies in the relevant State or Territory jurisdiction. The SOP should only be used subject to the applicable legal requirements (including OH&S) operating in the relevant jurisdiction. |
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Rutberg, A. T., & Keiper, R. R. (1993). Proximate causes of natal dispersal in feral ponies: some sex differences. Anim. Behav., 46(5), 969–975.
Abstract: Abstract. Fifteen years of data on natal dispersal age and the context of dispersal for the feral ponies of Assateague Island, Maryland are presented. Ninety-seven per cent of males and 81% of females dispersed from their natal groups by 5 years of age. For animals that left their natal group, average age of dispersal was 20[middle dot]8 months for males and 24[middle dot]6 months for females. Male dispersal age was strongly and significantly correlated with number of peers in the natal group, and males dispersing with peers were significantly older than males dispersing without peers, suggesting that males delayed dispersal when peers were available for interaction. Female dispersal age was not influenced by number of peers, but was correlated with age of first reproduction. Factors not influencing dispersal age in either sex were presence of a younger sibling, maternal band transfers, and maternal age and dominance rank. The relatively high frequency of females failing to disperse from their natal groups is puzzling in light of data showing diminished fecundity in non-dispersing pony mares.
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Dugatkin, L. A., & Earley, R. L. (2003). Group fusion: the impact of winner, loser, and bystander effects on hierarchy formation in large groups. Behav. Ecol., 14(3), 367–373.
Abstract: We present the results of a series of computer simulations that examined the impact of winner, loser, and bystander effects on hierarchy formation in fused groups. These effects and their implications for hierarchy structure and aggressive interactions were first examined in small four-member groups. Subsequent to this, the two small groups were fused into a single larger group. Further interactions took place in this fused group, generating a new hierarchy. Our models demonstrate clearly that winner, loser, and bystander effects strongly influence both the structure and types of interactions that emerge from the fusion of smaller groups. Four conditions produced results in which the same general patterns were uncovered in pre- and postfusion groups: (1) winner effects alone, (2) bystander loser effects alone, (3) winner and bystander winner effects operating simultaneously, and (4) all four effects in play simultaneously. Outside this parameter space, hierarchy structure and the nature of aggressive interactions differed in pre- and postfusion groups. When only loser effects were in play, one of the two clear alphas from the prefused groups dropped in rank in the eight-member fused group. When bystander winner effects were in play, it was difficult to rank any of the eight individuals in the fused group, and players interacted almost exclusively with those that were not in their original four-member group. When loser and bystander loser effects operated simultaneously, two top-ranking individuals emerged in the fused groups, but the relative rank of the other players was difficult to assign.
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Seaman, S. C., Davidson, H. P. B., & Waran, N. K. (2002). How reliable is temperament assessment in the domestic horse (Equus caballus)? Appl. Anim. Behav. Sci., 78(2-4), 175–191.
Abstract: Differences in behavioural characteristics between individuals of the same species are often described as being due to the temperament of the individuals. These differences can have enormous implications for welfare with some individuals apparently being able to adapt to environmental challenge more easily than others. Such differences have resulted in animals often being described as either `active' copers, which try to escape from or remove an aversive stimulus, or `passive' copers, which show no outward signs of a situation being aversive, thus, appearing to be unaffected. Tests previously developed to assess the temperament of animals have been criticised for several reasons. Behaviour is often recorded and categorised using methods that are not objective and tests are generally carried out once with no consideration of whether or not behavioural responses are consistent over time. This study takes these factors into account. The behaviour of 33 horses was recorded in three types of test--an arena test, response to a person and response to an object. In order to test whether or not responses were consistent over time, the tests were repeated three times with an average of 9 days between trials. Test results were validated using responses from questionnaires completed by the farm team leader. The data were analysed using an initial principal component analysis (PCA) and factor analysis. The horses were found to behave consistently over the three trials in their responses in the arena test. The responses to the person test and the object test were similar to each other; however, these responses were not consistent over trials. The behaviour in the arena test was unable to be used to make a prediction of behaviour in the person and object tests and vice versa. The responses shown by the horses did not enable them to be categorised as either active or passive copers. Behavioural responses in the tests were not predictive of the response to a startle test (water spray), nor could they be used to predict status or response to being reintroduced to the group after testing. There was no relationship between the responses in the tests and the ratings given by the farm team leader. It was concluded that horses vary widely in their responses to artificial behavioural tests, with only the responses to an open-field arena test being consistent over time, and therefore, the only type of test which can indicate some core factor of temperament.
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Caro, T. M., Graham, C. M., Stoner, C. J., & Vargas, J. K. (2004). Adaptive significance of antipredator behaviour in artiodactyls. Anim. Behav., 67(2), 205–228.
Abstract: We used comparative data to test functional hypotheses for 17 antipredator behaviour patterns in artiodactyls. We examined the literature for hypotheses about auditory and visual signals, defensive behaviour and group-related antipredator behaviour in this taxon and derived a series of predictions for each hypothesis. Next, we documented occurrences of these behaviour patterns and morphological, ecological and behavioural variables for 200 species and coded them in binary format. We then pitted presence of an antipredator behaviour against presence of an independent variable for cervids, bovids and all artiodactyls together using nonparametric tests. Finally, we reanalysed the data using Maddison's (1990, Evolution, 44, 539-557) concentrated-changes tests and a consensus molecular and taxonomic phylogeny. We found evidence that snorting is both a warning signal to conspecifics and a pursuit-deterrent signal, lack of evidence that whistling alerts conspecifics and indications that foot stamping is a visual signal to warn group members. Evidence suggested that tail flagging was a signal to both conspecifics and predators, that bounding, leaping and stotting were used both as a signal and to clear obstacles and that prancing functioned similarly to foot stamping. Analyses of tail flicking, zigzagging and tacking were equivocal. We confirmed that inspection occurs in large groups, freezing enhances crypticity, and species seeking refuge in cliffs tend to be small. Entering water and attacks on predators had few correlates. Finally, group living, a putative antipredator adaptation, was associated with large body size and species living in open habitats, confirming Jarman's (1974, Behaviour, 48, 215-267) classic hypothesis. Bunching and group attack apparently deter predators. Despite limitations, comparative and systematic analyses can bolster adaptive hypotheses and raise new functional explanations for antipredator behaviour patterns in general.
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Fishman, M. A. (1999). Predator Inspection: Closer Approach as a Way to Improve Assessment of Potential Threats. J. Theor. Biol., 196(2), 225–235.
Abstract: When detecting a predator, some prey animals respond in a counterintuitive fashion by approaching, rather than fleeing, that potential threat of extinction. This seemingly paradoxical behaviour, known aspredator inspection, has been reported for a wide variety of taxa--and therefore can be assumed to be adaptive. However, the view of predator inspection as a paradoxical behaviour rests on two implicit assumptions: (a) initial predator detecting is unambiguous, with no uncertainty in discriminating between hunting and non hunting members of predator species, or members of predator species and unrelated phenomena; (b) the costs of flight are negligible relative to the risk of predation. Upon reflection assumption (a) is not really tenable. Whereas assumption (b) is not consistent with experimental evidence [Godin & Crossman (1994)Behav. Ecol. Sociobiol.34,359-366]. Given that predator detection is ambiguous and the costs of flight are not negligible, a prey individual may benefit by a closer approach to the source of the alarming signals, thus improving its assessment of the situation--despite the increased risk of predation. In this paper, the above statement is given rigor by reformulating the problem in game theoretical terms. The results indicate that a prey will minimize its costs by performing predator inspection whenever its degree of certainty regarding predator identification and/or assessment of its intentions is less than a threshold, which is determined by the model's parameters.
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FitzGibbon, C. D. (1994). The costs and benefits of predator inspection behaviour in Thomson's gazelles. Behav. Ecol. Sociobiol., 34(2), 139–148.
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