'Werewolf' rats specialize in eating poisonous scorpions and centipedes

The southern grasshopper rat is nicknamed the "ghost wolf" because it often howls like a small wolf on a full moon night before killing its prey .

The southern grasshopper rat ( Onychomys torridus ) lives in the southwestern United States and northwestern Mexico, eating scorpions, insects, other rats, and some plants. They are predators that can resist scorpion venom, according to Live Science .

Howling posture of a grasshopper mouse. (Photo: Minden Pictures)

This rat is extremely aggressive, will attack anything that moves that is not too much larger than it. It is even willing to cannibalize when food is scarce. Grasshopper rats will ambush their prey, then capture and kill them with a bite to the head. One of their favorite prey is the Arizona bark scorpion ( Centruroides sculpturatus ) with venom strong enough to kill humans.

To cope, grasshopper mice reduce the impact of venom by pausing the chemical channel that transmits pain signals to the brain when hit by venom. This means they basically don't feel pain, although researchers still don't know why the poison doesn't kill them. Grasshopper rats can also bite off scorpion tails to prevent their prey from injecting venom.

When howling on a full moon night, the grasshopper mouse stands on its hind legs, raises its nose to the sky and makes a sound that can be heard from a distance of 100 m. Their calls are produced in a similar way when humans speak and wolves howl, using tissue vibrations produced by air currents, according to a 2017 study. The team also found that these mice have bell-shaped sound path, helping to increase sound intensity.

The howl emitted right before killing prey helps grasshopper rats mark their territory. They are highly territorial and mostly live alone. Individuals may live in pairs of males and females, but they often kill their mates, according to Animal Diversity Web.