To judge from now-clichéd chase scenes in wildlife doc­u­men­taries, you might think  predator-prey inter­ac­tions are sim­ple and pre­dictable: A preda­tor sees, chases, kills, and then eats its prey. End of story.

But don’t let such scenes fool you. Recent research indi­cates that some predator-prey encoun­ters are remark­ably intri­cate, and nuanced inter­ac­tions  can deter­mine their out­comes. This research includes the col­lec­tion and analy­sis of video record­ings of inter­ac­tions between rat­tlesnakes and their prey–including squir­rels, chip­munks and lizards—by a research team led by Rulon Clark of San Diego State University.

Snakes: Here, there and everywhere

Clark stud­ies rat­tlesnakes because these rep­tiles are key mem­bers of many food chains. A case in point: Clark’s research has pegged the rel­a­tively small rat­tlesnake as the  preda­tor with the great­est over­all bio­mass at Blue Oak Ranch Reserve, located on Mount Hamil­ton about 10 miles east of San Jose, Calif. The reserve is one of the 38 sites in the Uni­ver­sity of California’s Nat­ural reserve System.

Clark says the rattlesnake’s sur­pris­ing abun­dance in the reserve is partly due to its cold-blooded biol­ogy, which enables indi­vid­u­als to sur­vive by con­sum­ing as few as two or three ani­mals per year. Warm-blooded preda­tors such as coy­otes and bob­cats must eat much more frequently.

Clark’s research also indi­cates that rat­tlesnake den­si­ties in the reserve exceed those doc­u­mented else­where through­out Cal­i­for­nia, includ­ing the remote Mojave Desert. Clark attrib­utes this abun­dance to the fact that the reserve has remained rel­a­tively undis­turbed by ranch­ers and hunters for decades. Blue Oak’s high rat­tlesnake den­sity may rep­re­sent the impor­tant influ­ence of these car­ni­vores  in cer­tain ecosys­tems, includ­ing those located rel­a­tively close to devel­oped areas.

You-blink-and-you-miss-it

Despite the eco­log­i­cal sig­nif­i­cance of rat­tlesnakes, their preda­tory behav­ior has not been thor­oughly stud­ied. Mas­ters of cam­ou­flage, rat­tlesnakes are furtive, mak­ing them  dif­fi­cult to find and fol­low in the field. What is known is that a suc­cess­ful rat­tlesnake attack involves three steps:

1) Strik­ing and hit­ting a prey ani­mal, usu­ally from just 10 inches away.

2) Inject­ing venom into the prey ani­mal, which may attempt to escape before suc­cumb­ing to the venom.

3) Relo­cat­ing the weak­ened prey animal.

Rat­tlesnakes usu­ally com­plete the first and sec­ond steps of each attack in less than one sec­ond—too fast to be observed in detail with the naked eye. The snakes may also wait weeks or even months before attack­ing again. That means observ­ing pre­da­tion by rat­tlesnakes in the field usu­ally demands more patience and luck than even the most ded­i­cated researchers can muster.

Rat­tlers ready for close-ups

Funded by the National Sci­ence Foun­da­tion, Clark is solv­ing many of these prob­lems with high-tech help. He and his col­leagues catch wild snakes and insert tiny radio tags into their tis­sues. The tags help sci­en­tists locate snakes hid­ing under rocks or beneath bushes. When they spot indi­vid­u­als poised in ambush coils, the researchers plant portable mini video cam­eras one to three meters away to film poten­tial strikes. The film then gets trans­mit­ted to reserve head­quar­ters via Blue Oak Ranch’s wire­less data network.

Video cam­eras can be employed on snake stake­outs as long as nec­es­sary to cap­ture brief squir­rel attacks. “Unlike peo­ple, they are as patient as a snake,” Clark says.

Once a snake strike has been recorded, researchers can sim­ply fast-forward the video until they get to the action. View­ing the film on a frame-by-frame basis can help reveal the exact dis­tances, move­ments, and tim­ing of the move­ments of rat­tlesnakes and their prey. The record­ings thus pro­vide more spe­cific and pre­cise infor­ma­tion than live, non-filmed observations.

Strik­ing out

Clark’s video record­ings show that about 50 per­cent of strikes by wild rat­tlesnakes are unsuc­cess­ful. This research has also revealed that rat­tlesnake attacks are most com­monly thwarted if the prey makes a rapid, eva­sive dodge dur­ing the frac­tion of a sec­ond after the rat­tlesnake starts to strike, but before the rat­tlesnake reaches the prey.

The researchers also dis­cov­ered that rat­tlesnakes may strike out dur­ing any of the three steps required for a suc­cess­ful attack. For exam­ple, the researchers have observed rat­tlesnakes clearly strike their prey, but then fail to find the struck ani­mal. In these cases, the researchers sus­pect, the rat­tlesnake knew it had not suc­cess­fully enven­o­mated its prey, and chose not to devote energy to a poten­tially fruit­less pursuit.

The researchers have also observed rat­tlesnakes fatally strike prey, but then fail to relo­cate their enven­o­mated prey after it suc­cumbed to the venom.

An age-old arms race

Clark’s spe­cial inter­ests include inter­ac­tions between rat­tlesnakes and their favorite prey: Cal­i­for­nia ground squir­rels. Young Cal­i­for­nia ground squir­rel pups account for up to 69 per­cent of a rattlesnake’s diet, and up to 34 per­cent of the pups are lost to rattlesnakes.

The predator-prey rela­tion­ship between rat­tlesnakes and Cal­i­for­nia ground squir­rels is ancient; it orig­i­nated about 10 mil­lion years ago in the ances­tors of these species.

As the two species evolved, they devel­oped “a kind of arms race, where an adap­ta­tion by one of them trig­gered the evo­lu­tion of an adap­ta­tion in the other,” says Clark. A sim­i­lar arms race occurs between increas­ingly strong antibi­otics and microbes that are evolv­ing increas­ing resis­tance to antibiotics.

Wag the squirrel

The rattlesnake’s arse­nal isn’t lim­ited to toxic venom. It also includes a pair of pit organs on its face that can sense infrared radi­a­tion, or heat. The pit organs help the snake find warm-blooded prey.

To counter rat­tlesnakes, Cal­i­for­nia ground squir­rels devel­oped a rare abil­ity to neu­tral­ize rat­tlesnake venom. So armed, Cal­i­for­nia ground squir­rels some­times assertively stand their ground to rat­tlesnakes instead of quickly flee­ing for fear of being bit­ten. The squir­rels may vocal­ize to warn their pups or kick dirt at the snake while evad­ing the reptile’s defen­sive strikes. On rare occa­sions, squir­rel may even attack and kill rattlesnakes.

In addi­tion, a Cal­i­for­nia ground squir­rel may flag its tail, rais­ing and wag­ging it back and forth, before enter­ing under­ground bur­rows or patches of plants likely to con­ceal rat­tlesnakes. Tail flag­ging also increases the tem­per­a­ture of the tail.

Such tail flag­ging had pre­vi­ously been inter­preted solely as warn­ings to other prey about the pres­ence of rat­tlesnakes that had been seen by the flag­ging squir­rel. But this inter­pre­ta­tion has recently been chal­lenged by obser­va­tions that Cal­i­for­nia ground squir­rels may per­form the tail sig­nals whether or not they have actu­ally seen a rat­tlesnake in the area.

In addi­tion, Cal­i­for­nia ground squir­rels that have seen coiled rat­tlesnakes have been observed to approach, inspect and repeat­edly tail flag near the snake for sev­eral min­utes; this type of sig­nal­ing appears to be directed at the coiled snake.

Such obser­va­tions inspired Clark and his team to research the pos­si­bil­ity that the squir­rels may use tail wag­ging and tail heat­ing, both of which may be seen by rat­tlesnakes, to com­mu­ni­cate with preda­tory rat­tlesnakes in addi­tion to other prey.

Tails you lose

Specif­i­cally, the researchers sus­pect that squir­rels may per­form two types of tail signaling:

1) “Vig­i­lance adver­tis­ing” per­formed before enter­ing areas that are par­tic­u­larly likely to har­bor rat­tlesnakes. The researchers sus­pect that the squir­rel issues this type of sig­nal to gener­i­cally warn any rat­tlesnakes that may be nearby whether or not they have actu­ally seen snakes nearby. Squir­rels may per­form vig­i­lance adver­tis­ing to demon­strate they are look­ing out for the preda­tors and pre­pared to dodge their attacks. The tail flag­ging might thus inhibit rat­tlesnake attacks by con­vinc­ing rat­tlesnakes that their attacks would be thwarted.

2) “Per­cep­tion adver­tis­ing” that is intended: a) to tell a recently dis­cov­ered rat­tlesnake that it has been dis­cov­ered by the flag­ging squir­rel and will there­fore be unable to take the squir­rel by sur­prise; and b) to “out” the dis­cov­ered rat­tlesnake to other nearby squir­rels and other poten­tial prey in order to raise their rat­tlesnake vigilance.

As increas­ing num­bers of squir­rels dis­cover and adver­tize a rattlesnake’s pres­ence at any par­tic­u­lar loca­tion, the rattlesnake’s abil­ity to com­plete suc­cess­ful sur­prise attacks there decreases. After rat­tlesnakes are dis­cov­ered and “out­ted” by tail-flagging squir­rels, they fre­quently aban­don the area and move some­place where they would still have the advan­tage of sur­prise. Snakes often relo­cate even though flag­ging squir­rels don’t usu­ally pose a seri­ous, direct threat to their safety.

When squir­rels flag their tails, they may inad­ver­tently announce their pres­ence to other types of preda­tors such as birds of prey. Because other preda­tors are not as depen­dent on the ele­ment of sur­prise as rat­tlesnakes, they would not nec­es­sar­ily be inhib­ited from attack­ing by tail flag­ging. So even though tail flag­ging may help pro­tect squir­rels from rat­tlesnakes, it may increase their risk of being attacked by other preda­tors. For this rea­son, squir­rels prob­a­bly reserve their tale flag­ging for cer­tain cir­cum­stances that have, as yet, not been specif­i­cally identified.

Meet the robotic squirrel

To test Clark’s ideas about vig­i­lance adver­tiz­ing and per­cep­tion adver­tiz­ing from squir­rels, he and his research team are  record­ing con­trolled encoun­ters between live rat­tlesnakes and a life­like robotic squir­rel which can wag its tail. What’s more, its body can be heated by cop­per coils to anatom­i­cally cor­rect tem­per­a­tures, and its tail tem­per­a­ture can be increased above its body tem­per­a­ture dur­ing predator-prey interactions.

The robotic squirrel’s body is made from a taxi­der­mied skin, and is stored in squir­rel bed­ding when off-duty to give it a real­is­tic smell.

Test­ing tail signals

Because the robotic squirrel’s behav­ior can be manip­u­lated in ways that a live squirrel’s behav­ior can­not, it can help test the responses of rat­tlesnakes to cer­tain squir­rel behav­iors. For exam­ple, Clark’s team is using the robot to see how live rat­tlesnakes react to a tail that is motion­less, one that is wag­ging; and one that is wag­ging and heated.

Clark’s goal is to help iden­tify the func­tions of the tail sig­nals. For exam­ple, the exper­i­ments could show that when the robotic squirrel’s tail is wag­ging and heated, it inhibits attacks from rat­tlesnakes and com­pels rat­tlesnakes to aban­don their ambush sites.

If the exper­i­ments show that a motion­less tail does not elicit any par­tic­u­lar response from rat­tlesnakes, it sug­gests tail sig­nal­ing is designed to inhibit attacks and com­pel rat­tlesnakes to aban­don their ambush sites.

On the other hand, the exper­i­ments could show that the robotic squirrel’s tail behav­ior has no impact on rat­tlesnake attacks or retreats. Such results would refute the idea that tail flag­ging is used for per­cep­tion adver­tis­ing and vig­i­lance advertising.

The exper­i­ments may also reveal that rat­tlesnake behav­ior is influ­enced by related fac­tors such as the dis­tance between the rat­tlesnake and the sig­nal­ing robotic squir­rel and the amount of time the robotic squir­rel spends tail signaling.

The ascent of robots

In addi­tion to cre­at­ing a robotic squir­rel, teams of sci­en­tists and engi­neers have recently cre­ated robotic mod­els of bees, fish, lizards, cock­roaches, rats, sage grouse, frogs and other organ­isms. These types of robotic crea­tures are cur­rently being incor­po­rated into stud­ies address­ing diverse top­ics, includ­ing, for exam­ple, the design of search-and-rescue robots and the devel­op­ment of meth­ods to save school­ing fish from oil spills and other nat­ural dis­as­ters. Because of advance­ments in tech­nol­ogy and the decreas­ing costs of robot­ics, increas­ingly sophis­ti­cated robotic mod­els will likely soon be incor­po­rated into more types of sci­en­tific studies.

—Lily White­man, National Sci­ence Foundation

Har­ried trav­el­ers trudg­ing through Nor­man Y. Mineta San Jose Inter­na­tional Air­port have a new way to escape the stresses of a mod­ern tran­sit hub. All they have to do is wan­der over to Ter­mi­nal B, between the Alaska and South­west ticket coun­ters and the bag­gage carousels.

There they’ll spot a sleek kiosk hous­ing video mon­i­tors on each side. One screen shows a sedge-lined pond that mir­rors the sky; another, a satel­lite view of the South Bay; still more depict grassy hills dot­ted with majes­tic oaks. Draw closer to the kiosk, and the scenes begin to move. Clouds shift and shad­ows lengthen; two ducks wing in, then rip­ples crease the water behind the pad­dling pair. It’s time-lapse pho­tog­ra­phy of the NRS’s Blue Oak Ranch Reserve, located just nine miles from the air­port as the crow flies.

Called Wired Wilder­ness 01, the art­work by Freya Bardell and Brian Howe of Green­meme Stu­dio went live at the air­port this week. They were awarded $30,000 from the City of San Jose Pub­lic Art Pro­gram, plus sup­port from the airport’s Art + Tech­nol­ogy Pub­lic Art Pro­gram, to cre­ate the piece.

The project is intended to raise aware­ness of cli­mate change by blend­ing Sil­i­con Val­ley inge­nu­ity with artis­tic cre­ativ­ity. These glimpses of nature beyond air­port glass, steel, and asphalt also remind trav­el­ers of the inher­ent value of wild places.

“We were inter­ested in look­ing at nature but also how tech­nol­ogy is being used to bet­ter under­stand nature’s mes­sages,” Bardell says. This focus led them to dig­i­tal ecol­o­gist Michael Hamil­ton of the UC Nat­ural Reserve System.

For over a decade, Hamil­ton has helped pio­neer the devel­op­ment of wire­less envi­ron­men­tal sen­sors. Designed to oper­ate out­doors for long peri­ods of time, these small devices can pro­vide con­tin­u­ous record­ings of cli­mate, audio, and video con­di­tions from remote loca­tions. Arrays of sen­sors can pro­vide a fine-grained view of phys­i­cal con­di­tions such as tem­per­a­ture, humid­ity, light lev­els, and soil mois­ture across an entire land­scape, but also record the pro­gres­sion of events such as wild­flower blooms and bird nesting.

The devices do dou­ble duty as wire­less net­work nodes. They can relay data to a hub at reserve head­quar­ters, where it be accessed via the Inter­net. A recent grant from the National Sci­ence Foun­da­tion through the Amer­i­can Rein­vest­ment and Recov­ery Act (ARRA) dra­mat­i­cally increased the speed and capac­ity of  the reserve net­work and the Inter­net, mak­ing the seam­less trans­fer of video data from the reserve to the air­port pos­si­ble.

In 2008, Hamil­ton was named direc­tor of the NRS’s Blue Oak Ranch Reserve, located in the Dia­blo Range bor­der­ing east­ern San Jose. He wasted no time deploy­ing a new gen­er­a­tion of envi­ron­men­tal sen­sors across the 3,300-acre site. Dubbed the Very Large Eco­log­i­cal Array, the net­work keeps con­tin­u­ous tabs on con­di­tions across the reserve’s oak wood­lands, chap­ar­ral, sage scrub, and ponds.

To Bardell and Howe, Hamilton’s arrival at Blue Oak was noth­ing short of serendip­i­tous. Wired to col­lect cli­mate and video data from its far­thest reaches, it seemed an ideal place to blend sci­ence, tech­nol­ogy, and art. The City of San Jose agreed, award­ing a $30,000 grant to Green­meme to develop art respond­ing to cli­mate change.

Bardell and Howe wanted to col­lect some cli­mate data of their own using the reserve’s exist­ing wire­less net­work. They envi­sioned cam­eras that could take pho­tos of reserve sites every three min­utes, then beam the images to the airport.

The replayed scenes “give trav­el­ers a dif­fer­ent per­spec­tive on how time works; they see nature’s time com­pared to their time on the way to a flight,” Bardell says. By see­ing these changes in the land­scape, view­ers are reminded of envi­ron­men­tal trans­for­ma­tions hap­pen­ing over a much longer and larger scale.

If the con­cept was straight­for­ward, get­ting the sys­tem to work wasn’t so easy. Because the reserve gen­er­ates all its elec­tric­ity locally from solar pan­els, Bardell and Howe had to design the sys­tem to oper­ate on very lit­tle power. The cam­eras had to with­stand pour­ing rain, bak­ing heat, and winter’s chill, yet remain able to trans­mit their pho­tos to the air­port for years on end.

To solve the prob­lem of weather resis­tance, Bardell says, “we hacked into water­tight Pel­i­can cases to make our own cam­era hous­ings, then set the boxes onto mobile hunt­ing stands.”

The project doesn’t just con­vey infor­ma­tion away from the reserve; it also informs reserve research. For exam­ple, one sci­en­tist work­ing at Blue Oak is using Green­meme video to dis­tin­guish between fog and cool weather events in the reserve’s cli­mate sen­sor records. The infor­ma­tion will help estab­lish whether fog pat­terns can be used as an indi­ca­tor of cli­mate change.

“We wanted the art to be some­thing that func­tioned in tan­dem with sci­ence, ” Howe says, “as a con­duit for sci­ence to get away from the reserve. We knew we were going to get a pub­lic audi­ence at the air­port, but we weren’t quite expect­ing a sci­en­tific one.”

Says Bardell, “it’s been a very valu­able expe­ri­ence for us as artists to be immersed in the com­mu­nity of sci­ence researchers. We’ve spent a lot of time on the reserve and we’ve made good rela­tion­ships with peo­ple doing many weird and won­der­ful research projects. The expe­ri­ences we’ve had there will def­i­nitely go on to inform our future work.”