Are Black Widows Poisonous To Pets?

As a pet owner, you want to protect your furry friend from danger. Unfortunately, that includes handling potentially dangerous situations such as your cat or dog encountering the infamous black widow spider. These spiders are known to be highly venomous and can cause serious injuries to humans, so it’s important to understand their effect on pets. Continue reading to discover the effects of black widow spider venom on cats and dogs, and how to protect your pet.

How to Identify Black Widows

Black widow spiders are highly venomous and are dangerous to both humans and pets. These spiders can be found throughout North America, excluding Alaska. On average, female black widow spiders measure 2-2.5 cm in length, are black and shiny, and have an orange or red hourglass marking on their underside. Immature females are brown, and the hourglass mark is lighter in color. The males are brown and do not have the hourglass mark on them. The males are generally considered non-toxic due to the small size of their fangs and bite. The spiders carry a potent venom, a-latrotoxin, which can cause serious injury or even death if not treated quickly.

Black Widow Poisoning Symptoms

Dogs and cats bitten by a black widow spider may exhibit severe clinical signs. Common signs of poisoning to watch out for include: 

  • Severe muscle pain
  • Cramping
  • Instability
  • Tremors
  • Paralysis
  • Blood pressure changes
  • Drooling
  • Vomiting
  • Diarrhea

If treatment is not sought out in a timely manner, death can quickly follow. 


Pets may come across a black widow spider in dark, dry, and undisturbed environments such as a leaf pile outside or even in your basement. If your pet encounters a black widow spider and gets bitten, you need to seek treatment immediately. Contact Pet Poison Helpline at (855) 764-7661 and your veterinarian for life-saving advice. Your pet will need to receive treatment from your veterinarian. This can include the administration of antivenom, IV fluids, anti-seizure medications, pain medications, and supportive care. Being aware of our pets’ surroundings and behaviors is so important as well as taking necessary steps to prevent poisoning accidents from occurring. Do not hesitate to contact Pet Poison Helpline should any poisoning emergency arise.