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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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refbase @ user @ | Serial | 515 | ||
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Author | Linklater, W.L.; Cameron, E.Z.; Stafford, K.J.; Veltman, C.J. | ||||
Title | Social and spatial structure and range use by Kaimanawa wild horses (Equus caballus: Equidae) | Type | Journal Article | ||
Year | 2000 | Publication | New Zealand Journal of Ecology | Abbreviated Journal | New Zealand J. Ecol. |
Volume | 24 | Issue | 2 | Pages | 139-152 |
Keywords | Bachelor male; Band; Density; Habitat use; Home range; Management proposals; Micro-climate; Vegetation monitoring; habitat use; home range; mammal; social structure; spatial distribution; New Zealand; Equus caballus | ||||
Abstract | We measured horse density, social structure, habitat use, home ranges and altitudinal micro-climates in the south-western Kaimanawa ranges east of Waiouru, New Zealand. Horse density in the Auahitotara ecological sector averaged 3.6 horses.km-2 and ranged from 0.9 to 5.2 horses.km-2 within different zones. The population's social structure was like that of other feral horse populations with an even adult sex ratio, year round breeding groups (bands) with stable adult membership consisting of 1 to 11 mares, 1 to 4 stallions, and their predispersal offspring, and bachelor groups with unstable membership. Bands and bachelor males were loyal to undefended home ranges with central core use areas. Band home range sizes varied positively with adult band size. Home ranges overlapped entirely with other home ranges. Horses were more likely to occupy north facing aspects, short tussock vegetation and flush zones and avoid high altitudes, southern aspects, steeper slopes, bare ground and forest remnants. Horses were more likely to be on north facing aspects, steeper slopes, in exotic and red tussock grasslands and flush zones during winter and at lower altitudes and on gentler slopes in spring and summer. Seasonal shifts by bands to river basin and stream valley floors in spring and higher altitudes in autumn and winter are attributed to the beginning of foaling and mating in spring and formation of frost inversion layers in winter. Given horse habitat selectivity and the presence of other ungulate herbivores, results from present exclosures are likely to exaggerate the size of horse impacts on range vegetation. Proposals to manage the population by relocation and confinement are likely to modify current social structure and range use behaviour and may lead to the need for more intensive management in the longer term. | ||||
Address | Ecology Group, Institute of Natural Resources, Massey University, Private Bag 11-222, Palmerston North, New Zealand | ||||
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ISSN | 01106465 (Issn) | ISBN | Medium | ||
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Notes | Cited By (since 1996): 12; Export Date: 21 April 2007; Source: Scopus; Language of Original Document: English; Correspondence Address: Linklater, W.L.; Ecology Group; Institute of Natural Resources; Massey University; Private Bag 11-222 Palmerston North, New Zealand; email: wlinklater@hotmail.com | Approved | no | ||
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refbase @ user @ | Serial | 793 | ||
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