Date: January 13, 2017
Source: University of California - Riverside
Summary:
The antagonistic predator-prey relationship is of interest to
evolutionary biologists because it often leads to extreme adaptations in
both the predator and prey. One such relationship is seen in the
rattlesnake-kangaroo rat system. Now researchers have captured in high
speed (500 frames per second) a rattlesnake trying to capture a kangaroo
rat.
Feeding
is paramount to the survival of almost every animal, and just about
every living organism is eaten by another. Not surprisingly, the animal
kingdom shows many examples of extreme specialization -- the chameleon's
tongue, fox diving into snow, cheetah sprinting -- for capturing prey
or escaping predators.
The
antagonistic predator-prey relationship is of interest to evolutionary
biologists because it often leads to extreme adaptations in both the
predator and prey. One such relationship is seen in the
rattlesnake-kangaroo rat system -- a model system for studying the
dynamics of high-power predator-prey interactions that can be observed
under completely natural conditions.
Curiously,
however, very little is known about the strike performance of
rattlesnakes under natural conditions. But that is now about to change
because technological advances in portable high-speed cameras have made
it possible for biologists like Timothy Higham at the University of
California, Riverside to capture three-dimensional video in the field of
a rattlesnake preying on a kangaroo rat.
"Predator-prey
interactions are naturally variable -- much more so than we would ever
observe in a controlled laboratory setting," said Higham, an associate
professor of biology, who led the research project. "Technology is now
allowing us to understand what defines successful capture and evasion
under natural conditions. It is under these conditions in which the
predator and prey evolve. It's therefore absolutely critical to observe
animals in their natural habitat before making too many conclusions from
laboratory studies alone.”
A
question Higham and his team are exploring in predator-prey
relationships is: What factors determine the success/failure of a strike
or escape? In the case of the rattlesnake and kangaroo rat, the
outcome, they note, appears to depend on both the snake's accuracy and
the ability of the kangaroo rat to detect and evade the viper before
being struck.
"We
obtained some incredible footage of Mohave rattlesnakes striking in the
middle of the night, under infrared lighting, in New Mexico during the
summer of 2015," Higham said. "The results are quite interesting in that
strikes are very rapid and highly variable. The snakes also appear to
miss quite dramatically -- either because the snake simply misses or the
kangaroo rat moves out of the way in time.”
Many
studies have examined snake strikes, but the new work is the first
study to quantify strikes using high-speed video (500 frames per second)
in the wild.
Study results appear in Scientific Reports.
In
the paper, Higham and his coauthors conclude that rattlesnakes in
nature can greatly exceed the defensive strike speeds and accelerations
observed in the lab. Their results also suggest that kangaroo rats might
amplify their power when under attack by rattlesnakes via "elastic
energy storage.”
"Elastic
energy storage is when the muscle stretches a tendon and then relaxes,
allowing the tendon to recoil like an elastic band being released from
the stretched position," Higham explained. "It's equivalent to a sling
shot -- you can pull the sling shot slowly and it can be released very
quickly. The kangaroo rat is likely using the tendons in its lower leg
-- similar to our Achilles tendon -- to store energy and release it
quickly, allowing it to jump quickly and evade the strike.”
To
collect data, the team radio-tracked rattlesnakes by implanting
transmitters. Once the rattlesnake was in striking position, the team
carried the filming equipment to the location of the rattlesnake (in the
middle of the night) and set up the cameras around the snake. The team
then waited (sometimes all night) for a kangaroo rat to come by for the
snake to strike.
"We would watch the live view through a laptop quite far away and trigger the cameras when a strike occurred," Higham said.
Next,
the researchers plan to expand the current work to other species of
rattlesnake and kangaroo rat to explore the differences among species.
Story Source:
Materials provided by University of California - Riverside. Original written by Iqbal Pittalwala. Note: Content may be edited for style and length.
Journal Reference:
1 Timothy E. Higham, Rulon W. Clark, Clint E. Collins, Malachi D. Whitford, Grace A. Freymiller. Rattlesnakes
are extremely fast and variable when striking at kangaroo rats in
nature: Three-dimensional high-speed kinematics at night. Scientific Reports, 2017; 7: 40412 DOI: 10.1038/srep40412
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