Feral horse abundance can be measured in three ways: as the total number of animals in a population; as the number of animals per unit area (absolute density); or by a density index where a measurable correlate of absolute density is used (relative density) (Caughley 1977); Dung counts are more reliable indicators of animal density than visual or track counts (Seber 1982) and can provide estimates of absolute density if defecation rates are known.
Dung counts have been used to provide ~dices of relative density, although these apply only to comparative studies between similar areas over time (Dobbie et al. 1993); or to temporally spaced surveys of the same area.
For the present study the measure of relative density was chosen, where a density index of fresh dung deposits was correlated to habitat Home ranges of feral horse bands overlap (Duncan 1983, Dobbie et al. 1993); vary in size according to habitat (Dobbie et al. 1993); and, in arid Australia, can be as large as 88 km2 (Dobbie & Berman 1990).
Within home ranges, seasonal and daily variation can be expected (Pratt et al. 1986).
Feist (1971) records a home range estimate of up to 32 sq.
Km 2 for harem bands, bachelor bands and solitary males in Wyoming and Montana.
Climatically these areas are similar to conditions encountered in the Australian Alps. 5 Wild horses spend 50-70 per cent of the day feeding (Duncan 1985) and can tolerate a wide variety of foods and ingestion schedules (Waring 1983).
Horses prefer to feed in areas with the greatest concentration of high quality food (green plant matter) and when this is sparse they search out areas with the greatest concentration of perennial herbaceous plants (green or dead) (Duncan 1983).
Horses mainly eat grasses, but will ingest roots, bark, buds and fruit.
Seasonal patterns in ingestive behaviour occur in most locations (Waring 1983).
Horses don’t usually graze where dung occurs, but show a preference for defecating in areas containing dung (Waring 1983).
Foals up to one month old may eat faecal material, usually that of their mothers, but the ingestion of faeces is rare in adults (Waring 1983).
Adults may, however, eat faeces if food is scarce (Feist & McCullough 1976). Defecation rates Defecation rates in horses and other ungulates is influenced by a wide variety of factors such as: diet (composition, quantity, quality, water content, amount of roughage); ambient temperature; activity level; sex and age; and season (Eberhardt et al. 1956, Irby 1981, Loft et al. 1988, Neff 1968, Pratt et al. 1986, Smith 1964, Waring 1983).
Tyler (1972) found that during daylight hours New Forest ponies defecated, on average, every 2.2 hours in summer and every 2.4 hours in winter.
Kownacki et al. (1978) found that stallions defecated on average 12.8 times per day, mares 6.5 times, and foals 10.3 times~ However, identification of sex and age classes from dung samples is unlikely to be achieved in the field.
Equations that relate body weight to faecal pellet dry weight (Coe& Carr 1983, Putman 1984) are possible.
The daily faecal output per horse tends to be 14-23 kg (Waring 1983).
Horses will often continue to move or graze while defecating (Waring 1983).
The determination of an average daily defecation rate per horse is essential if an estimate of horse numbers based on dung counts is to be made.
Free-roaming horses tend not to limit defecation to certain areas (unlike contained horses), stallions being the exception (Waring 1983).
Adult males (harem stallions and bachelors) tend to defecate at dung (stud) mounds, while young males do so occasionally (Feist & McCullough 1976, Waring 1983).
Dung mounds occur periodically throughout the range (Waring 1983).
The largest ones occur along routes common to a number of bands, such as on the way to watering holes (Waring 1983).
The mounds vary from 19ss than one square metre to a series of adjacent mounds as large as 1.8 by 7.6 metres (Feist 1971).
They are often used during encounters between stallions as part of the agonistic behaviour patterns.
Stallions appear to limit the amount of faecal discharge when marking mounds, or the dung of mares, so that repeated marking may occur in a short span of time (Waring 1983). 6 If defecation in horses occurs with specific behaviour patterns and is also linked to social behaviours, this implies a non-random dung distribution (shown by Edwards & Hollis 1982, for free-ranging ponies).
Elimination by one animal appears to induce other animals in the band to eliminate, especially adult males (Waring 1983).
Stallions may paw at existing piles of dung and add to them (Waring 1983.
McCort 1984), making it necessary for dung counters to differentiate between individual defecations.
Stallions defecate on the dung of their harem mares most frequently during the spring to summer breeding season ([urner et al. 1981).
Dung counts outside this period, when this behaviour is less marked, may be necessary to distinguish individual defecations.
The expectation is that dung will not be randomly distributed, but clumped within home ranges.
A sampling system will therefore need to be large enough to accommodate non-random distributions of dung. Strip-transect Dung counts have been performed using line-transects (Bames et al. 1991), quadrats within gridsystems (Jachrnann & Bell 1979), and strip (belt) transects (Overton 1971).
Line-transects were thought to be inappropriate for the present study because they fail to net sufficient information.
Quadrat-based techniques (including stratified random sampling methods) appeared to be impractical because of the effort involved in transporting equipment in mountainous country and producing sufficient sample size.
Strip-transects were the chosen method as they appeared to offer sufficient flexibility, accuracy and sampling intensity for the present study. METHODS Study area Field work was carried out in two stages, the first, a pilot study at McPhersons Plain (148 15’E, 35 47’S) near Sue City on 25 September 1995, was performed to establish the transect width.
The second stage.
To assess transects, was based at Tin Mine Hut (148 14’E, 36 42’S) in Kosciusko National Park (the study area) between 20 and 24 November 1995 (Map 1 ).
As part of the second stage a measure of the daily defecation rate of horses was made at Torn Groggin station (148 08’E, 36 33’S) using saddle horses.
The Tin Mine Hut location was at altitude 1246 rn, on predominantly alpine plateau.
Major lineation was north west/south east marked by the Ingeegoodbee and Moyangul Rivers, which formed the major drainage lines. — McCort, W.
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