were more dominant than Hereford co

were more dominant than Hereford cows.
Social dominance hierarchies are largely passive. Subordinates
avoid conflict and dominant animals make few overt
attempts to supplant subordinates. Low-ranked animals monitor
their spatial relationships relative to dominant animals. As
subordinates get closer to dominants, subordinate animals
may reduce their bite rate, stop feeding, or move away, but
behavior of dominants is largely unaffected by their proximity
to subordinates (Bennett et al. 1985; Bennett and
Holmes, 1987). Thus, movements by dominant animals may
displace subordinates, and dominant animals enjoy greater
freedom in habitat selection. This may restrict the amount or
quality of resources available to subordinates (Bennett et al.,
1985; Bennett and Holmes, 1987). Dominant animals may
preclude subordinate animals from occupying certain sites,
and dominant animals have priority access to available resources,
including feeding areas, shade, salt licks, supplemental
feed, and shelter from storms (Bennett et al., 1985;
Bennett and Holmes, 1987). Low-ranked animals are forced
to relocate into areas of lower habitat quality or they must
wait their turn until the more dominant animals are satisfied
and leave the area. If the relative differences in resource
utilization are great, dominant individuals and their offspring
gain more weight and reproduce more successfully (Wagnon
et al., 1966; Broom and Leaver, 1978; Bennett et al., 1985;
Bennett and Holmes, 1987).
Dominance hierarchies also exist between subgroups of
cattle, and higher-ranked groups limit access to resources by
lower-ranked subgroups. Lazo (1994) found that a subordinate
subherd reduced its home range area and relocated its
home range when higher-ranked subherds came too close.
Similarly, dominant subgroups (bands) of feral horses displace
subordinate subgroups from watering locations. Horses
within the dominant subgroups, in addition to the dominant
stallions, display aggression toward horses in the subordinate
subgroups, indicating that the hierarchy is, in fact, an intergroup
hierarchy and not just a hierarchy of the dominant
stallions from each band (Miller and Denniston, 1979).
Social dominance hierarchies play an important role in
supplement consumption by rangeland cattle. Wagnon (1966)
reported that hand-feeding cows from 2 to 10 yr of age resulted
in many 2- and 3-yr-old cows being driven from the
feed troughs before they had the opportunity to feed. Subordinate
4- and 5-yr-olds spent less time at the feeders, more
time waiting, and gained half as much weight as older, more
dominant, cows (Wagnon, 1966).
Friend and Polan (1974) studied the feeding behavior of
21 Holstein cows and found dominant-ranking cows to occupy
feeding stalls adjacent to cows of similar social rank.
Mean time eating ranged from 2.9 to 4.7 h/d and was quadratically
related to social rank. Mid-ranked cows spent the
least amount of time eating. The authors concluded that
dominance values failed to predict access to feeding stalls.
They also doubted the existence of a classical social hierarchy
in this herd. Rather, they suggested that cows were
driven by physiological demands and that cows operating at
Proceedings of the American Society of Animal Science, 1999
3
peak production gained access to resources through persistence
rather than aggression.