This is the part most new tahr hunters get wrong.
A "trophy bull" is not just an animal with long horns. It is an animal that is old, properly mature, expressing the full set of physical features that come with age. The horn length matters, but the heaviness of the bases, the depth of the cape, the overall body shape and the broomed tips of old monarchs all matter just as much. New Zealand's Deerstalkers Association publishes a field aging guide that is worth memorising. The categories below are a compressed version.
Juveniles (six to eighteen months) are roughly nanny-sized, narrow-bodied, hard to sex at distance.
Immature bulls (two and a half to four and a half years) carry small or scruffy manes, light overall colour, no defined dorsal stripes, and horns of nine to twelve inches with light bases and widely spaced annuli. A two-year-old bull can already have nine-inch horns. Resist the temptation. He has years to grow.
Mature bulls (five and a half to eight and a half years) are the typical herd bulls. Full mane, often blonde fading to grey or black down the body. Dark hindquarters. Near-black face. Faint dorsal kidney stripes. Body about one and a half to two times the size of a nanny. Horns of ten to fourteen inches, with the bases beginning to "stack" — the visible ridges from successive years' growth piling up close together.
Old bulls (eight and a half years and up) are the prize. They are heavier through the hips. The horns are the giveaway: a high proportion will have broomed, broken or chipped tips, the ridging is worn smooth, and the bases are thick and stacked regardless of how long the horns happen to measure. A bull whose horns measure thirteen inches is almost certainly eight years old or more.
Trophy scoring in New Zealand is done by the Douglas Score, devised by Norman Douglas and adopted by the NZ Deerstalkers Association in 1958. For tahr the score is simple: add together each horn's length over the outside curve, plus its base circumference, both sides, and double the shorter horn's measurements to enforce symmetry. You enter the NZDA records at 40 Douglas points or with a horn longer than 13 inches, whichever comes first.
International hunters often think in Safari Club International scores instead. SCI uses a similar method and runs a record book with bronze, silver and gold tiers. SCI scores tend to come in a point or two higher than Douglas for the same animal because of small differences in how the bases are measured. Rowland Ward uses single longest horn measurement and groups tahr with chamois, ibex and tur for record purposes.
The horn-length expectations to carry in your head are these:
- 10 inches. Common. Young or sub-mature bull. Pass it.
- 11 inches. A standard mature bull on public land. A respectable trophy if the bases are heavy and the bull is old.
- 12 inches. A solid trophy. Above-average for a guided hunt.
- 12.5 to 13.5 inches. A genuinely above-average bull. Most well-run guided hunts will average something in this band.
- 13 inches and over. Trophy of a lifetime tier. Rare on public land, achievable on quality private blocks.
- 14 inches and over. Exceptional. Possibly the top one or two animals taken in NZ in any given season.
The species' maximum recorded horn length is around 18 inches, from a Himalayan animal. NZ-grown horns can run high but rarely break the upper end of that range.
The most common rookie mistake is to measure with the eye: a young animal's horns look long because the bull's face and body are small. The base mass and the stacking are what tell you the age. If you can't see the bases clearly through the spotter, walk a hundred metres up the ridge for a better angle and look again.