Previous: Chapter Four: Of Niche and Kin
There was an email from Rad waiting for MaryLiz as the sun rose, cc’ed to Frances.
“MaryLiz (and Hi, Frances!),
“I extracted what I could from your critter videos. The dropped frames got me thinking. Since the videos all include visible timecode, I made a list of timecodes for all the missing frames [Attachment 1].
“Your team set the cameras going six hours before they were found, so there’s plenty of stream where nothing’s disturbing the cameras. I averaged the interval between dropped frames to get a baseline. It varies according to how far each camera was from the repeater, like you’d expect. With no motion detection taking place, the mean dropped frame rate is a little less than one frame every three minutes. I wondered if the dropped frame rate depended on each camera’s distance from the repeater. It does. See my signal strength overlay for your map [Attachment 2].
“Things start to get a little interesting five minutes before the action starts. Five of the streams have little strings of missed frames here and there. Nothing’s yet in front of the camera, so it was probably missed.
“It gets to be three missing frames a minute, in places, which is nine times worse than the baseline. Like tremors before an earthquake. I wonder if that’s not your study subjects, entering the area, moving around the cameras, causing minor disruptions to the wifi signal, just radio wave reflections off their own bodies.
“As you know, the cameras were placed on a fairly square grid, with the central wifi repeater tied up in a tree. Not quite smack in the center of the the camera field, but near enough.
“The first camera nabbed, camera #3, was at 4:05:20. It’s dragged along for 40 seconds, then is heard no more. You can see from the graph that the dropped frame rate rises slowly at first, then ever more quickly until the last frame is received at 4:06:01. It’s not an exact fit to the the inverse square law, which matches the fact that the camera was dragged and dropped in fits and starts, but near enough, given the small sample size.
“The second camera, camera #11, meets the same fate as the first, starting at 4:07:04. But here it’s different. Even while being dragged, its dropped frame rate stays steady as a rock for the first ten seconds, and it stays in range 15 seconds longer than its predecessor.
“The same thing, roughly, is true for camera #16, and, here’s the thing…after 5 seconds of being dragged, when its dropped frame rate starts rising, cameras #4 and #12 show brief spikes in dropped frames.
“It struck me that one explanation might be that the cameras, as they’re dragged further from the repeater, are trying harder and harder to stay connected to the repeater, and that interferes with their nearest comrades in the process.
“Going in, I thought I wouldn’t be able to help you figure out what direction they might have been taken, because with just one point, the wifi repeater, there’s no way to triangulate. I could have judged basic distance from ping times, which we don’t have. However, looking at the results from the dropped frame analysis, I realized that we really have up to ten reference points for triangulation, namely, the radio repeater and whatever cameras were still operating nearby, as each one was taken.
“The first camera taken was on the eastern edge of the grid, and it didn’t register any impact on the others. The second was on the northern edge, quite a bit closer to the repeater.
“The next two were both set up near the western edge, a little north and south of the repeater, and there was interference to two sets of cameras east of both of them at the same time that they were taken away, with the closest camera experiencing interference first, both times.
“If you think you see where this is going, you’re probably right. Every camera for which there’s applicable data shows the same thing.
“Your bandits both arrived from, and returned to, pretty much due east. Best guess, based on good old least square regression, points to a heading of 87 degrees, five degree error either way.
“You’re welcome.
“– Rad.”
MaryLiz reached to call Frances, just as Frances knocked once and burst through the door. “Did you read –?”
MaryLiz said, “Yes. I just did.”
Frances said, “They came from the Gulf. The notoriously wallaby friendly Gulf of Mexico.”
“I think it’s time to saddle up. No. Coffee first.”
“Heard. I’ll put the word out. See you in the Mess.”
MaryLiz was still groggy. “Frances, could you do me a favor?”
“Sure, Cap, name it.”
“Find out if Jo knows how to ride a horse.”
An hour later, a mounted posse arrived at Mystery Poop Valley. The riders spaced themselves fifty meters apart, and, methodically, rode due east towards the coast. The forever war between the competing powers of the Rio Grande and the tides was evident here, so close to the Gulf of Mexico, and the horses struggled to pick their way across mudflats, abandoned oxbow lakes, and marshes of brackish water.
They could hear the pounding of the surf over the coastal dunes when a shout from one of the hands brought everyone riding over. The ranch hand, Merl, dismounted, and put up a hand to stop the others when they’d come within about ten meters.
“Wook,” said Merl, pointing at the ground. “Wawaby twacks.”
Jo examined the imprints in the mud and whistled. “They sure are. Well done, mate, good eye!”
The clue was small as it was tantalizing: the area preserving the animal tracks was the size of a baseball pitcher’s mound. But within it could be seen what Jo declared to be two sets of footprints heading west, and two more, with a probable third, heading east. Jo stopped to photograph the tracks next to a reference scale as the others remounted.
Excited by their discovery, Merl made a beeline for the coast, and was the first to the dunes, followed closely by the others.
Merl’s face fell, seeing what lay past the crest of the dunes.
“Oh,” Merl said, “This place.”