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Keiper, R., & Houpt, K. (1984). Reproduction in feral horses: an eight-year study. Am J Vet Res, 45(5), 991–995.
Abstract: The reproductive rate and foal survival of the free-ranging ponies on Assateague Island National Seashore were studied for 8 years, 1975 to 1982. Most (52%) of the 86 foals were born in May, 13% were born in April, 22.6% in June, 10.4% in July, and less than 1% in August and September. The mean foaling rate was 57.1 +/- 3.9% and the survival rate was 88.3 +/- 3.6%. Forty-eight colts and 55 fillies were born (sex ratio 53% female). Mares less than 3 years old did not foal and the foaling rate of 3-year-old mares was only 23%, that of 4-year-old mares was 46%, that of 5-year-old mares was 53%, and 6-year-old mares was 69%. The relatively poor reproduction rate was believed to be a consequence of the stress of lactating while carrying a foal when forage quality on the island was low. The hypothesis was supported by the higher reproductive rate (74.4 +/- 2.4%) of the ponies in the Chincoteague National Wildlife Refuge on the southern part of the island. Their foals are weaned and sold in July each year. Despite the low reproductive rate on Assateague Island National Seashore , the number of ponies increased from 43 to 80, a 90% increase in the 8-year period or greater than 10%/yr. There were 24 deaths and 8 dispersals from the study area.
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Bard J,. (1984). Perch la zebra In:Kos;Revista di Cultura e Storia della. Sci Med, Nat e Humane, 1(6).
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Bökönyi, S. (1984). Horse. In Manson (Ed.), Evolution of domesticated animals (Vol. 18, pp. 162–173). Hoboken, NJ: John Wiley & Sons.
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KASEDA Y et al,. (1984). Separation and independence of offsprings from the harem groups in Misaki horses. Jap J Zootechn Sci, 55, 852–857.
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Kusunose R, S. H. (1984). The behavioral development of thouroughbred foals and the relationship between dams and foals. Jap J Zootechn Sci, 55, 263–271.
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Mccort Wd,. (1984). Behavior of feral horses and ponies. J Anim Sci, 58, 493–499.
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Seyfarth, R. M., & Cheney, D. L. (1984). The acoustic features of vervet monkey grunts. J Acoust Soc Am, 75(5), 1623–1628.
Abstract: East African vervet monkeys give short (125 ms), harsh-sounding grunts to each other in a variety of social situations: when approaching a dominant or subordinate member of their group, when moving into a new area of their range, or upon seeing another group. Although all these vocalizations sound similar to humans, field playback experiments have shown that the monkeys distinguish at least four different calls. Acoustic analysis reveals that grunts have an aperiodic F0, at roughly 240 Hz. Most grunts exhibit a spectral peak close to this irregular F0. Grunts may also contain a second, rising or falling frequency peak, between 550 and 900 Hz. The location and changes in these two frequency peaks are the cues most likely to be used by vervets when distinguishing different grunt types.
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BAGTACHE B et al,. (1984). Paläontologie – Présence d`un Equus cacallin et d`une autre espéce nouvelle d`Equus dans l`Aterien des Allobroges, Agérie. C R Acad Sc Paris, 298, 609–612.
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DUNCAN P et al,. (1984). Reduction of inbreeding in a natural herd of horses. Anim Beh av, 32, 520–527.
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Eisenmann V,. (1984). Sur quelques caractères adaptatifs du squelette d`Equus et leurs implications paléoécologiques Bull. Bull Mus natn Hist nat Paris, 6, 185–195.
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