Date of Award:

1977

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Ecology

Advisor/Chair:

David F. Balph

Abstract

This study examined the activity patterns and social relation ships between individuals in a large herd of domestic sheep (Ovis aries) in an effort to determine if behavioral characteristics predisposed certain individuals to coyote (Canis latrans) predation. The research was conducted on the Cook Ranch near Florence, Montana, from March through September of 1975. Data were collected from a herd of 627 ewes and 1082 lambs, each individually identifiable. A random sample of 44 ewes and their 75 lambs were intensively studied over a 16-wk period to establish activity budgets and the relationships between sheep activity and vulnerability to coyote predation. The feasibility of creating target lambs in a free-ranging environment by altering movement, appearance, or social relationships with other herd members was examined in six experiments. During the study, 24 ewes and 47 lambs died from natural causes. Predators killed 7 ewes and 73 lambs. Coyotes selected single lambs, lambs displaying aberrant movement, and lambs whose dams had restricted mobility. Reduced mobility appeared to increase the probability of a lamb being on the periphery of the bedground and this in turn increased the probability of it being encountered by an attacking coyote. Grazing and resting periods of lambs were highly correlated with those of the ewes. Lambs were not within sight of their dams 30 percent of the time and showed a greater tendency to be absent during rest periods than during other activity periods. Yearling ewes investigated less and won less encounters. Brocatelface ewes grazed less and slept more than whiteface ewes. The oldest ewes interacted with other members of the herd less than younger ewes. Although significant differences in behavior existed between different age and genotype cl asses, the behavior of ewes whose lambs were killed by coyotes was remarkably similar to all other ewes. Male lambs were consistently absent from their dams less than female lambs. Single lambs also showed a tendency to be with the ewe more than twins. Single lambs spent more time nursing than twins during the first half of the study but not the last half. Siblings that were killed by coyotes consistently lay down less than their litter mates. Although differences existed in the behavioral signature of various classes of lambs, no relationships between these differences and vulnerability to predation was apparent. / coyote predation on domestic sheep seems to be related more to the chance of a lamb being on the periphery of the bedground than to differences in behavioral signatures. No pairwise associations were found between ewes. Yearling ewes associated with other yearling ewes and were peripheral individuals both during the day and on the bedground. Brocatelface ewes were peripheral during the day, but not on the bedground. Statistically, yearling ewes were leaders, but leadership in a welfare sense did not exist. The general lack of file formations and the rolling pattern of files when files were formed suggests that leadership in domestic sheep is not a robust phenomenon. The influence of dominance on positional behavior observed during the study was reflected in strange-lamb experiments. Lambs which were unfamiliar with the herd were subordinate and were forced into peripheral positions where they were more vulnerable to predation for up to 3 weeks. ' Lambs with a high susceptibility to coyote predation can be created by simply raising lambs in isolation and later releasing them into a herd.

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