There will be blood. And barf.
It’s a tough world out there.
Prey species experience intense selection pressure to evolve ways to outwit their predators. Indeed, the ‘Life-Dinner’ principle explains that while unsuccessful predators lose a meal, unsuccessful prey will lose their lives! The diversity of ways in which prey species in the animal kingdom defend themselves against predators is extremely vast; however, there can also be a great deal of diversity in anti-predator behaviors within a single species. Not all predator attacks are of the same magnitude, and not all prey individuals of a certain species will react in the same way to a given level of attack.
It was with these questions in mind that Bateman and Fleming (2010) investigated variation in the antipredator responses of armoured crickets (Acanthoplus discoidalis). Specifically, the researchers were most interested in the kinds of attacks that would elicit regurgitation and autohaemorrhaging. What exactly does this mean? I
It means that these scientists tortured crickets until they either barfed or spewed blood everywhere.
Attacks were performed with forceps and initiated from either the top on the pronotum (a severe attack) or from the side on the legs (a less severe attack). It was found that attacks from the side initially resulted in a biting attempt (by the cricket), followed by an autohaemorrahge of acrid-smelling haemolymph approximately 62% of the time. Attacks on the pronotum resulted in an autohaemorrhage 86% of the time. Interestingly, females were more likely to regurgitate than males in response to a simulated predator attack, and the probability of regurgitation increased with repeated attacks (seriously…how do you do this kind of thing without feeling like a big jerk?!).
Additional experiments were conducted in order to elucidate the response of a predator to both the haemolymph and the regurgitate of the crickets. Foodstuffs were presented to bearded dragon lizards (Pogona vitticeps) and striped skinks (Trachylepis punctatissima) that were either untreated or painted with haemolymph or regurgitate. It turns out that autohaemorrhaging is extremely effective. Predators never consumed foodstuffs anointed with haemolymph, and if they made the ‘mistake’ of biting into one, they dropped it immediately and proceeded to wipe their mouths on the ground. Regurgitate anointed foodstuffs were consumed part of the time by the predators, indicating that this isn’t as effective as autohaemorrhaging in response to a substantial attack.
In conclusion then, when biologists tortured crickets the crickets reacted by throwing up and making a bloody mess. However, there was purpose to this behavior since it seems that such indignities actually deter the predators that threaten them. Biologists suggest that autohaemorrhaging may be more common in organisms that sequester defensive compounds from plants that can be used as part of their discharge. Man, it’s a tough world out there.
Bateman, P., & Fleming, P. (2009). There will be blood: autohaemorrhage behaviour as part of the defence repertoire of an insect Journal of Zoology, 278 (4), 342-348 DOI: 10.1111/j.1469-7998.2009.00582.x
very cool!
malcolm
^ wash, of course. Feel free to correct and delete this.
Wow.
I suppose I would try to wash out my mouth too! *eeecck!*
Reminds me of the American Dad pilot episode where Roger oozes everywhere.
http://americandad.wikia.com/wiki/File:Roger_pilot.jpg
Why would a predator be repelled by the taste of a prey animal’s haemolymph? Do they not chew?
Good point Tim…I’m not quite sure of the answer. I expect that the defensive spew has a kind of toxic chemical makeup in addition to just being blood…not sure though.
Done