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Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand

journal contribution
posted on 2023-05-17, 07:50 authored by Linklater, WL, Elissa Cameron, Minot, EO, Stafford, KJ
Abstract Although feral horses are a common management problem in numerous countries, detailed and long-term demographic studies are rare. We measured the age and sex structure, and pregnancy, birth and death rates in a population of 413 feral horses in New Zealand during 1994¨C98 and used them to construct a model simulating population growth. Survivorship increased with age (0¨C1 years old = 86.8%, 1¨C2 = 92.3%, 2¨C4 = 92.4%, ¡Ý 4 years old = females 94%, males 97% per annum). Birth sex ratio parity, a slight female bias in the adult sex ratio (92 males per 100 females) and higher adult male survivorship indicated lower average survivorship for young males than females that was not detectable in mortality statistics. Pregnancy and foaling rates for mares ¡Ý 2 years old averaged 79 and 49%, respectively. Foaling rates increased as mares matured (2¨C3-year-old mares = 1.9%, 3¨C4 = 20.0%, 4¨C5 = 42.1%, ¡Ý 5 = 61.5% per annum). Young mares had higher rates of foetal and neonatal mortality (95% of pregnancies failed and/or were lost as neonatal foals in 2¨C3-year-old mares, 70.6% in 3¨C4, 43.2% in 4¨C5, and 31% in mares ¡Ý 5 years old). Population growth was 9.6% per annum (9.5¨C9.8, 95% CI) without human-induced mortalities (i.e. r = 0.092). Our model, standardised aerial counts, and historical estimates of annual reproduction suggest that the historical sequence of counts since 1979 has overestimated growth by ~50% probably because of improvements in count effort and technique.

History

Publication title

Wildlife Research

Volume

31

Pagination

119-128

ISSN

1035-3712

Department/School

School of Natural Sciences

Publisher

C S I R O Publishing

Place of publication

150 Oxford St, Po Box 1139, Collingwood, Australia

Rights statement

Copyright © CSIRO 2004

Repository Status

  • Restricted

Socio-economic Objectives

Other environmental management not elsewhere classified

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