This is an old wives' tale and is not based on any scientific or practical evidence. Septic systems are designed to treat human waste and other biodegradable materials, such as toilet paper, that are flushed down the drain. Adding dead animals, bones, or fur to a septic tank can potentially cause clogs, blockages, and other issues. These materials do not break down properly in the septic tank and may interfere with the normal biological processes that occur in a septic system, leading to malfunction or failure.