16 Jan 09
Big generator still out today so we’re still operating on the small one. Conserving power, and no internet this morning. Running on battery power as long as I can.
Proxmity Tracking paper
Reading the proximity paper I mentioned a few days ago. A few interesting things stick out:
The collars had a weight of 125g. That’s too high for us. Are they less now?
The error rates look high to me. In the field, 34% exhibited problems they could not correct in the field. Apparently this is similar to the rates for GPS collars. Given my own experience with small GPS units, I wonder if that’s due to the size of the GPS collar. In any event, a 34% failure rate for proximity collars seems high.
The number of erroneous contacts is worth noting. Below a 15-second sample rate, they saw many continuous contacts show up as multiple contacts. That’s not so useful, though they do note that as the sample rate is taken higher, the number of erroneous multiple contacts decreases.
The number of “phantom radio detections” they had seems high too. I wonder if they are all analog radios, which is what’s causing the error?
They state that “because this was the first field deployment of these collars, such problems were not unexpected and determining their causes should enhance design modifications to limit similar problems.” In other words, they might be functioning much better now. This paper is from 2006, meaning there’s likely been another revision or two of the collars.
Their tests were all for the 1 – 1.5m range, though the collars can supposedly go out to 100m. I wonder if any research has been done on the longer ranges.
Further research: “Passive integrated transponder (PIT) tags have been used successfully to monitor individuals’ proximity to structures or use of certain areas (Prentice et al. 1990, Harper and Batzli 1996, Boarman et al. 1998, Kunz 2001, Gibbons and Andrews 2004) but have not been used to document individual-to-individual contacts. To our knowledge, the only previous attempt at proximity detection has been the MateID system (Sirtrack Ltd.; Ji et al. 1999, 2005)….. This system is limited in that contact can be estimated between, but not within, the 2 groups (e.g., genders) and only at very close ranges.”
“One-way systems may be available in the future, utilizing fixed-location receivers and animals carrying only transmitters, which would be similar to some current PIT tag applications (Gibbons and Andrews 2004). Such an arrangement would have positive implications for power consumption and collar size.” It would also have positive implications for our relay idea.
The rest of the day
In other news, it was a fairly quiet day. After a morning reading up on animal telemetry, we had a nice small lunch — only two tables out of about twelve were filled, because it’s Friday, and the boat took the last large group of undergrads back up the river after breakfast this morning. We had a leisurely lunch, filled with stories from Rudy the ornithologist about his travels around Bolivia, the hallucinogenic effects of ayahuasca and San Pedro cactus, and so forth.
After lunch, I finished off a little code and some email, then went for a walk on my own. It was a gorgeous sunny day, and the view from the canopy tower was spectacular. Lots of butterflies, but sadly, no monkeys. Then, on the way back, I ran across a group of wooly monkeys and got the chance to take some more pictures. Finally got a half decent one of a monkey staring down at me while he wrestles with another monkey. Those little bastards are hard to get pictures of!
Came back to camp and coded a little more, then did a quick run into the forest with Tony and Margaret looking for a wooly group she had been tracking earlier in the day. We didn’t find them, unfortunately. There is some confusion at the moment as to which monkeys are in which groups, because both Margaret and Peter have run across at least two signals at the same time. Tony’s not sure what it means, but he’s intrigued.
A new batch of undergrads have arrived this afternoon. We’ll see what they’re like at dinner.