Hoof and foot loads for reindeer (Rangifer tarandus)

1. What they did

Reindeer spend over 40% of each year in snow, and their broad, crescent-shaped hooves, working dew claws and bristly hair help them stay on top of it. How far an animal sinks depends on its “load on ground”: its weight divided by the area of hoof or foot carrying it. The author set out to measure this for reindeer in Finland, as no study had compared it between reindeer populations.

• Living reindeer. In winter 1988, at the Kaamanen Reindeer Research Station, he weighed 60 semi-domesticated reindeer (8 female and 13 male calves, 10 young females aged 2, 9 young males aged 2 to 3, and 20 adult females). The left front and hind feet were pressed onto a hard surface in a natural position and their outlines drawn, for the hoof alone and for the whole foot (hoof plus dew claws). Lengths were measured to the nearest millimetre.
• Checking against footprints. To make the areas as correct as possible, he measured clear reindeer footprints on hard snow for the spacing between the hooves and the distance from the back of the hooves to the dew claws.
• Wild forest reindeer. He measured clear footprints on hard snow of 26 identified wild forest reindeer (7 calves, 11 adult females and 8 adult males) in Kuhmo and Salamajärvi national park, 1985 to 1988.
• Loads. Hoof load and foot load were each reindeer’s live weight divided by the combined area of all 4 hooves or feet. Loads were also worked out for moments when a reindeer stands on only 3, 2 or 1 feet, as happens when walking and galloping.

2. What they found

Hoof and foot size

• Front hooves and feet were bigger than hind ones.
• Male calves and young males had bigger hooves and feet than female calves and young females.
• Wild forest reindeer footprints gave bigger hoof and foot areas than semi-domesticated reindeer: for example, foot areas of 200.3 cm² for calves, 230.4 cm² for adult females and 258.6 cm² for adult males, against 165.3 cm² (front feet) for semi-domesticated calves and 214.1 cm² for adult females. Their dew claws were also longer.
• Heavier reindeer had bigger hooves and feet (correlations of r = 0.64 to 0.84 between live weight and hoof or foot area).

Loads on four feet

• Standing on all 4 feet, semi-domesticated calves had a hoof load of about 235 g/cm² and a foot load of about 85 g/cm². Adult females had 268 and 102 g/cm².
• Calves and young reindeer had the lowest loads.
• Counting the dew claws as part of the foot gave loads well under half the hoof-only loads.

Loads when moving

• A walking reindeer is carried by only 2 or 3 feet at a time; in a heavy diagonal gallop, by only 1 or 2.
• Foot load rose from about 85 to 102 g/cm² standing to a maximum of about 358 to 443 g/cm² when galloping on 1 foot.
• For comparison, other studies report reindeer hoof loads of about 125 to 180 g/cm² standing, 500 g/cm² walking and 1000 g/cm² trotting, and 390 to 659 g/cm² for standing moose.

3. What they concluded

• Semi-domesticated reindeer, and especially wild forest reindeer, are well adapted to travel through deep, soft snow.
• Wild forest reindeer are 10 to 15 cm taller than mountain and semi-domesticated reindeer, with longer legs and bigger feet. Their long legs and low load on ground are important adaptations to the taiga, where snow is usually very deep and soft.
• Hoof and foot loads show how hard snow must be to carry a reindeer. If it is too soft, the reindeer sinks and uses more energy walking.
• Load on ground is usually given for an animal standing still on 4 feet. It has practical value only when given for 1, 2, 3 or 4 feet, to match how the animal is moving.
• The author notes that the wild forest reindeer figures, taken from footprints, probably include some measurement error. The effects of speed on foot load were not considered.

4. How tracking was or was not used

Footprints were part of the method. The wild forest reindeer were measured only from their clear footprints on hard snow, and footprints of reindeer were also used to check the spacing between hooves and the position of the dew claws behind them. The paper does not say how the 26 wild forest reindeer prints were identified to individual, age or sex. The walk and gallop diagrams (Fig. 2) show which feet are on the ground at each moment.

5. Tracker or observer certification

Not reported. The paper does not say who found or measured the wild forest reindeer footprints, or how the individuals, ages and sexes were identified from them.

6. Other technologies, skills or innovations

• Hoof and foot outlines drawn with each foot pressed down on a hard surface in a natural position, and areas calculated by the Kelsall and Telfer (1971) method.
• Loads worked out for 1, 2, 3 or 4 feet on the ground, using the support patterns of walking and galloping.

7. Implications for conservation (from the paper)

• Long legs and low load on ground are key adaptations of wild forest reindeer to deep, soft taiga snow.