North/Jones side - 1/8/2020

Coverage: North half of Alma Bridge Road, from the parking lot to the second stop sign @ one way road section.
Time: 12:48pm - 2:17pm
Rainfall: 0 inches, dry for the past few days; cloudy with rain predicted tonight
Vehicles: 19
Big trucks: 2

  • 1 MidPen truck
    Bikes: 0
    Pedestrians: 1
    Live Newts: 0
    Dead Newts: 118, one very fresh
    Dead young garter (I think) snake: 1

I don't have time to post the actual observations today, but will soon.

During today's patrol, I wondered if it's possible that having long dry spells makes it more likely that we'd end up double-counting from one patrol to the next. Most of the bodies I found were very dry. I'd think they'd be more likely to break down when it's wet and not get double-counted, but if it's dry they're more likely to crisp up instead of break down, and still be visible for several patrols. @truthseqr, @merav have you had any experience with this?

Also, sorry that some of my observations from the previous patrol have bad locations, my GPS was not doing well that day, and it's tedious enough to figure out approximately where they should go and move them that I haven't had time. My assumption was that it's better to move them to approximately the right location, since it's not like the GPS location will be spot on every time anyway. But perhaps it's better to delete those observations instead, given the larger uncertainty? Thoughts?

Oh, one last thing. @truthseqr, just confirming that it would be best for me to remove my observations from 12/22, due to them being duplicates of @joescience1 doing the same patrol earlier in the day. True?

Posted on January 9, 2020 02:31 AM by newtpatrol newtpatrol

Comments

@newtpatrol, @merav, @anudibranchmom, @joescience1, @sea-kangaroo:

Short answers:

Yes, it does seem like the dried out carcasses stay around longer. However, last year during a dry, super cold period of about 10 days, I found the road almost bare of carcasses. I concluded that the high winds had blown the dry carcasses away. Heavy rains wash the carcasses away. I never found any carcasses that stayed on the road longer than 3 weeks.

@newtpatrol, please leave all your observations from 12/22 in iNat. When I was reviewing yours and Joe's observations, I didn't see any that were obvious duplicates. At some point we might want to do an actual comparison, but for now let's leave it "as is." The two patrols were done at different times of day, so it's conceivable that new roadkill happened between Joe's and Stacie's patrols. You've documented the fact that you both patrolled the same section of road, so that's good.

Please don't delete observations where the GPS is questionable. If you have time, please move the observation to an approximate location and put a note to that effect in the Description field. Just do the best you can. A couple times I forgot to set my GPS tracker and had to position each observation manually. I agree, it's a big pain and less than precise. I'll let the people analyzing the data know that several of us had difficulty with GPS. (I'll write a separate post on GPS.)

The issue of duplicates is a complex one. Here are my thoughts:
Last year I took extreme measures to ensure that I did not double-count the corpses because I didn’t want anyone to question my numbers. I noticed that the “fresh” roadkill had bright yellow/orange underbellies and/or bright red blood. These colors faded within about 3 days. When I uploaded the pictures to my computer, I sorted out the “fresh” from the “decomposed” corpses. I then compared the decomposed ones with the observations from previous weeks. If there were duplicates, I didn’t upload them to the main iNaturalist.org project, but rather added them to a project called “Decomp Study” (https://www.inaturalist.org/projects/pacific-newts-decomp-study-lexington-reservoir-area) so that I could understand how the newts decompose and what features to look for. This was an extremely time-consuming process that took hundreds of hours, and in the end, I don’t think it was worth the time and effort. Out of 2,148 decomposed newt pictures, I only found 332 duplicates (15%).

On the other hand, there are many reasons why we might be undercounting the dead newts:

Carcasses disappear from the road over time, sometimes in very short order. For example, Merav and I walked between Limekiln and Priest Rock trailheads one Saturday morning. She returned later that day with her family and noticed the following: "By the way - I was there again in the afternoon for a hike, and was surprised to see that almost all the newts we saw in the morning just by the Limekiln trailhead were gone. In the morning there were at least 10 dead newts. By 4 pm they were all gone, but 1 that was still there."

Carcasses disintegrate beyond recognition when many cars run them over. The traffic throughput on weekends is sometimes as high as 90+ vehicles per hour. Imagine what a small, soft-bodied newt looks like after it's been run over by 90+ vehicles.

I think many newts may be carried away on car or truck tires, so they're not counted. Also, around the quarry, I think newts are pulverized by all the gravel trucks that pass that way (sometimes several per hour).

We have not taken into account the effect that scavengers may have on newt roadkill count. According to Greg Pauly, Curator of Herpetology, Natural History Museum of Los Angeles County, "Raccoons, skunks, otters, crows, and ravens are all known predators of newts. While garter snakes swallow newts whole and therefore get exposed to the full dose of toxins, these bird and mammal predators tend to slit the animals up the belly and then eat the muscle tissue inside, often pulling limbs out. This leaves behind most of the organs and the skin with some or all of the limbs turned inside-out."

When there's a lot of rain, the carcasses tend to turn to mush rather quickly and they look like grayish splats on the road. You wouldn't even know they're newt roadkill unless you know what to look for.

During the rainy season, there are often mudslides along Alma Bridge Rd. and maintenance equipment routinely scrapes the sides of the roads to remove the mud. We believe dead newts are being swept up along with the mud and therefore are not being counted.

This is a complex problem without an easy solution. I’m hoping the possibility of double-counting the dead newts is balanced by the possibility of undercounting the roadkill.

Posted by truthseqr about 4 years ago

I suppose the ideal would be to patrol every day and remove the carcasses that are counted. But who has the time & inclination to do that? No one I know. We do the best we can.

Posted by truthseqr about 4 years ago

@truthseqr, thanks for the thorough responses. Very interesting to read your experience and observations about under/overcounting and decomposing. You've really put a lot of time and energy into this!

I won't remove my observations from 12/22. And will relocate the remaining bad GPS points when I have time.

Posted by newtpatrol about 4 years ago

@newtpatrol, when you're patrolling the beat hour after hour, day after day, month after month, looking at thousands of dead newts, you think about stuff like this. At least I do. I've often been accused of having an analytical mind. The darn thing just works like that. haha But I like it that way.

Posted by truthseqr about 4 years ago

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