October 16, 2019

Kiawah Bobcat Death Caused by Rat Poison

Kiawah’s historically healthy and stable bobcat population is declining, due in part to a recent rise in mortality rates. Four of the six bobcats fitted with GPS collars this past winter, as part of the Town’s Bobcat GPS Study, have died and Town Biologists have been trying to figure out why. The latest incident occurred on August 1, when Bobcat 300, an adult female, was found dead near Seascape Villas. Biologists sent the bobcat to the University of Georgia’s Wildlife Disease Laboratory for analysis. Laboratory tests revealed that the bobcat died from consuming toxic levels of four different anticoagulant rat poisons.

The four poisons identified in Bobcat 300 at high levels were Bromadiolone, Brodifacoum, Diphacinone, and Difethiolone. A fifth poison, Difenacoum, was found at low levels. All of these poisons are anticoagulant rodenticides (rat poison) and work by inhibiting the body’s recycling of Vitamin K, which is vital to the blood clotting process. Infected rodents ultimately bleed to death 3-7 days after consuming the poison. Bobcats pick up these poisons secondarily by eating infected rodents, not by consuming the actual poison itself.

Secondary poisoning of wildlife from anticoagulant rodenticides is well-documented in places like California’s Santa Monica Mountains, where a recent study found that 92% of bobcats and 94% of mountain lions had been exposed to rat poison. Other studies have shown high levels of rat poison in many different species of raptors (hawks, owls, eagles). The extent of the problem on Kiawah is currently unknown, and while future studies may provide additional details, taking action now to curb the use of these toxic chemicals is critical.

Rodenticides, especially the more toxic second-generation anticoagulants, are heavily regulated and can only be used by licensed, commercial pest control agents. Because of their high toxicity to people and pets, baits containing these rodenticides are placed within black plastic bait stations to prevent access by children and pets. Bait stations are placed around homes and other structures where rodents enter the box, eat the poisoned bait, and ultimately die somewhere nearby. Predators, including bobcats, hawks, owls, and snakes that provide natural control of Kiawah’s rodent populations, eat the poisoned rodents and over time, accumulate a toxic amount of these rodenticides. 

How can you help?

Talk to your pest control provider and tell them to:

Stop using all second-generation anticoagulant rodenticides. These include: Brodifacoum, Bromadiolone, Difenacoum, and Difethialone.

Follow an integrated pest management strategy.

• Identify specific rodent problems and locations by doing a thorough survey of the property. Only take action if a problem exists.
• Use non-chemical methods of rodent control (eliminate food/water sources, exclude rodents from structures by sealing exterior holes and cracks, use traps).
• Pesticides should only be used as a last resort for large infestations. In these cases, use first-generation anticoagulants or non-anticoagulant rodenticides only. The pesticide should only be applied for a short time (typically 10 days) and then stopped once the problem is resolved.

Town Biologists will continue to research this emerging issue. If you have questions, please contact Biologist Jim Jordan at 843-768-5106 or at jjordan@kiawahisland.org.