Defensive Venoms: Is Pain Sufficient for Predator Deterrence?

Area of Science:

• Zoology
• Animal Behavior
• Chemical Ecology

Background:

• Pain serves as an adaptive warning signal for potential tissue damage.
• Venomous animals use pain-inducing stings to deter predators by activating pain pathways.
• Distinguishing the role of pain versus toxicity in venom-mediated deterrence is challenging.

Purpose of the Study:

• To investigate whether pain alone is sufficient to deter predators.
• To determine the relative contributions of pain and toxicity in venom for predator deterrence.
• To examine the predatory behavior of southern grasshopper mice towards different scorpion species.

Main Methods:

• Laboratory experiments using southern grasshopper mice (Onychomys torridus) as predators.
• Presenting mice with Arizona bark scorpions (Centruroides sculpturatus) and stripe-tailed scorpions (Paravaejovis spinigerus).
• Comparing mouse predation success and preference with functional and blocked stingers.

Main Results:

• Southern grasshopper mice showed a preference for preying on less painful stripe-tailed scorpions over bark scorpions when stingers were functional.
• This preference vanished when scorpion stingers were blocked, indicating pain's deterrent effect.
• Mice that consumed a painless scorpion later attacked a venomous bark scorpion, even when capable of stinging.

Conclusions:

• Painful stings are necessary but not always sufficient to deter southern grasshopper mice.
• Toxicity, leading to tissue damage or neurological dysfunction, may be required for stronger predator aversion.
• Venom's defensive efficacy depends on a combination of pain and harmful effects.