BLOODY Awesome: Reflex Bleeding (Autohaemorrhaging)
“World’s Weirdest: Blood-Squirting Lizard’” by National Geographic. NatGeo Wild Youtube Channel, 30 January 2013.
URL: http://www.youtube.com/watch?v=GgB4u6Mgy2M (accessed on 20 March 2013)
Bloody Awesome Defence
‘Blood-squirting’ sounds like a scene ripped out of horror movies, but this action can be found in the Texas horned lizards (Phrynosoma cornutum) and Armoured ground crickets(Acanthoplus discoidalis). As seen in the clip, the ability to rupture vessels within the membranes of their eyes, spraying blood at predators, is an act of defence called autohaemorrhaging or reflex bleeding.When combined with toxins found in the blood of animals or insects (Moore & Williams, 1990), autohaemorrhaging acts as a chemical defence against predators. These chemicals present in the blood , coupled with elaborate head movements affects the oral receptors of the predator (Sherbrooke and Mason, 2005). The source of this defensive component within the lizard’s blood derives from the toxic venom of the ants that it consumes (Sherbrooke and Middendorf III, 2004). Such action belongs to a larger collection of ‘intimidation-type’ anti-predator behaviours, where the prey tries to intimidate the predator.
How and when autohaemorraging is carried out?
Animals carry out mechanisms that they deem more plausible to successfully allow their escape from the predator. The Texas horned lizard, resorts to autohaemorrhage (Marshall, 2010) when the action of ‘bowing its head’ (exposing horns on its head to a potential predator) fails.For the armoured ground crickets, the position of their predator affects how much and how autohaemorrhage is carried out. When the predator is above the cricket, it is difficult for the lizard to bite the predator in defence. Hence crickets engage in rapid autohaemorrhaging: Large quantities of haemolymph (toxic material that the cricket exudes) will be stored in the dorsal area (Bateman& Fleming, 2009)rather than squirted. This contact with the large amount of haemolymph successfully leads to the predator’s rejection of the cricket. Comparatively, if the predator is positioned beside the cricket, it is able to bite the predator and couple it with autohaemorrhaging. The cricket will squirt blood to a height of four to five times their body length (Bateman & Fleming, 2009), hence scaring their predator off.
Bateman, P.W. & Fleming, P.A., 2009. There will be blood: Autohaemorrhage behaviour as part of the defence repertoire of an insect, Journal of Zoology, 278: 342-348
Marshall, M., 2010. Zoologger: Horror Lizard squirts tears of blood.Zoologger,28 julty 2010. Hosted on: http://www.newscientist.com/article/dn19231-zoologger-horror-lizard-squirts-tears-of-blood.html (accessed on 21/03/2013).
Moore, K.A. & Williams, D.D., 1990. Novel strategies in the complex defense repertoire of a stonefly (Pteronarcysdorsata) nymph. Oikos, 57: 49–56.
Sherbrooke, W. C., & Mason, J. R., 2005. Sensory modality used by coyotes in responding to antipredator compounds in the blood of Texas horned lizards.The Southwestern Naturalist, 50(2): 216-222.
Sherbrooke, W. C., & Middendorf III, G. A., 2001. Blood-squirting variability in horned lizards (Phrynosoma). Copeia,4: 1114-1122.
“World’s Weirdest: Blood-Squirting Lizard’” by National Geographic. NatGeo Wild Youtube Channel, 30 January 2013. URL: http://www.youtube.com/watch?v=GgB4u6Mgy2M (accessed on 20 March 2013)