Motorhome manufacturer Winnebago Industries Inc. adopted a “poison pill” shareholder rights plan as a defense against “coercive or unfair takeover tactics,” Chairman Bruce Hertzke announced late Monday.

The poison pill would be activated if a person or group buys 15% or more of Winnebago’s common stock or announces plans to do so, Hertzke said.

Certain members of the family of the late John K. Hanson, founder of the company, are exempt from the poison pill. Certain Hansen family trusts and estates also are exempt.

The poison pill would allow shareholders to buy preferred stock that could be exchanged for common stock at a deeply discounted price.

Hertzke did not say whether Winnebago currently is the target of an unfriendly takeover effort, although that is considered unlikely because Luise V. Hanson, widow of the founder, owns 37% of the company’s shares.

Thor’s effort to takeover Coachmen currently is at a standstill because of Coachmen’s poison pill and Indiana’s tough anti-takeover law, according to most observers.