Featured Research

from universities, journals, and other organizations

Spitting cobras track first, predict later

Date:
May 15, 2010
Source:
Journal of Experimental Biology
Summary:
Spitting cobras spray venom in the eyes of their victims with remarkable accuracy, but how do they achieve this accuracy when they cannot steer the jet of venom? Researchers have found that cobras initially track their prey's movements, but at the moment when they spit, they predict where the victim's eyes will be 200 milliseconds in the future and aim there.

Spitting cobra.
Credit: iStockphoto

Most venomous snakes are legendary for their lethal bites, but not all. Some spit defensively. Bruce Young, from the University of Massachusetts Lowell, explains that some cobras defend themselves by spraying debilitating venom into the eyes of an aggressor.

Getting the chance to work with spitting cobras in South Africa, Young took the opportunity to record the venom spray tracks aimed at his eyes. Protected by a sheet of Perspex, Young caught the trails of venom and two things struck him: how accurately the snakes aimed and that each track was unique. This puzzled Young. For a start the cobra's fangs are fixed and they can't change the size of the venom orifice, "so basic fluid dynamics would lead you to think that the pattern of the fluid should be fixed," explains Young.

But Young had also noticed that the snakes 'wiggled' their heads just before letting fly. "The question became how do we reconcile those two things," says Young, who publishes his discovery that the snakes initially track their victim's movement and then switch to predicting where the victim is going to be 200 milliseconds in the future in the Journal of Experimental Biology.

Young remembers that Guido Westhoff had also noticed the spitting cobra's "head wiggle," so he and his research assistant, Melissa Boetig, traveled to Horst Bleckmann's lab in the University of Bonn, Germany, to find out how spitting cobras fine-tune their venom spray. The team had to find out how a target provokes a cobra to spit, and Young was the man for that job, "I just put on the goggles and the cobras start spitting all over," laughs Young.

Wearing a visor fitted with accelerometers to track his own head movements while Boetig and Westhoff filmed the cobra's movements at 500 frames/s, Young stood in front of the animals and taunted them by weaving his head about. Over a period of 6 weeks, the team filmed over 100 spits before trying to discover why Young was so successful at provoking the snakes.

Analyzing Young's movements, only one thing stood out; 200 ms before the snake spat, Young suddenly jerked his head. The team realized that Young's head jerk was the spitting trigger. They reasoned that the snake must be tracking Young's movements right up to the instant that he jerked his head and that it took a further 200 ms for the snake to react and fire off the venom.

But Young was still moving after triggering the snake into spitting and the snake can't steer the stream of venom, so how was the cobra able to successfully hit Young's eyes if it was aiming at a point where the target had been 200 ms previously? Realigning the data to the instant when Young jerked his head, the team compared all of the snakes' head movements and noticed that the cobras were all moving in a similar way. They accelerated their heads in the same direction that Young's eyes were moving. "Not only does it speed up but it predicts where I am going to be and then it patterns its venom in that area," explains Young.

So spitting cobras defend themselves by initially tracking an aggressor's movements. However, at the instant that an attacker triggers the cobra into spitting, the reptile switches to predicting where the attacker's eyes will be 200 ms in the future and aims there to be sure that it hits its target.


Story Source:

The above story is based on materials provided by Journal of Experimental Biology. The original article was written by Kathryn Knight. Note: Materials may be edited for content and length.


Journal Reference:

  1. Westhoff, G., Boetig, M., Bleckmann, H. and Young, B.A. Target tracking during venom 'spitting' by cobras. Journal of Experimental Biology, 2010; 213: 1797-1802 [link]

Cite This Page:

Journal of Experimental Biology. "Spitting cobras track first, predict later." ScienceDaily. ScienceDaily, 15 May 2010. <www.sciencedaily.com/releases/2010/05/100514074909.htm>.
Journal of Experimental Biology. (2010, May 15). Spitting cobras track first, predict later. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2010/05/100514074909.htm
Journal of Experimental Biology. "Spitting cobras track first, predict later." ScienceDaily. www.sciencedaily.com/releases/2010/05/100514074909.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com
What's To Blame For Worst Ebola Outbreak In History?

What's To Blame For Worst Ebola Outbreak In History?

Newsy (July 27, 2014) A U.S. doctor has tested positive for the deadly Ebola virus, as the worst-ever outbreak continues to grow. Video provided by Newsy
Powered by NewsLook.com
The New York Times Backs Pot Legalization

The New York Times Backs Pot Legalization

Newsy (July 27, 2014) The New York Times has officially endorsed the legalization of marijuana, but why now, and to what end? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins