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Author | Linklater, W. L.; Cameron, E. Z.; Stafford, K. J.; Minot, E. O. | ||||
Title | Estimating Kaimanawa feral horse population size and growth | Type | Conference Article | ||
Year | Publication | SCIENCE & RESEARCH INTERNAL REPORT 185 | Abbreviated Journal | ||
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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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Call Number | refbase @ user @ | Serial | 515 | ||
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Author | Cameron, E. Z.,; Linklater, W. L.,; Stafford, K.J.,; Minot, E. O., | ||||
Title | Social grouping and maternal behaviour in feral horses (Equus caballus): the influence of males on maternal protectiveness | Type | Journal Article | ||
Year | 2003 | Publication | Behavioral Ecology and Sociobiology | Abbreviated Journal | Behav. Ecol. Sociobiol. |
Volume | 53 | Issue | 2 | Pages | 92-101 |
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Abstract | The risk of infant injury or mortality influences maternal behaviour, particularly protectiveness. Mares are found in bands with a single stallion or bands with more than one stallion in which paternity is less certain. We investigated maternal behaviour in relation to band type. Mares in bands with more than one stallion were more protective of their foals, particularly when stallions and foals approached one another. The rate of aggression between the stallion and foal was a significant predictor of maternal protectiveness, and mare protectiveness was significantly correlated with reduced reproductive success in the subsequent year. Mares that changed band types with a foal at foot, or had their band type experimentally altered, were more protective of their foal in multi-stallion bands than they were in single-stallion bands. Equids are unusual amongst ungulates in that infanticide and feticide have been reported. Both occur where paternity has been uncertain, and equid social structure is similar to other species in which infanticide has been reported. Stallions benefit from infanticide as the mare has greater reproductive success in the subsequent year. Stallion aggression is a significant modifier of mare behaviour and maternal effort, probably due to the risk of infanticide. | ||||
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Corporate Author | Thesis | ||||
Publisher | Place of Publication | Editor | |||
Language | Summary Language | Original Title | |||
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Area | Expedition | Conference | |||
Notes | Approved | no | |||
Call Number | refbase @ user @ | Serial | 458 | ||
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