Reasons why Pacific Newt roadkill may be significantly under-reported

I'm reposting this entry from January 15, 2019 (with some additions) to emphasize its importance. As horrifying as the total death count is (5,349 as of this date), we may be under-reporting the actual number killed on Alma Bridge Rd. Here are the reasons:

1. Most of the time @merav and I are not able to cover the entire 4.1 mile length of Alma Bridge Road. We survey both sides of the road, so the entire hike is 8.2 miles. It takes about 3-5 hours to survey the entire length taking pictures. Some days (during the week) I only have a couple hours to do this work. I'm keeping a spreadsheet that shows the percentage of coverage for each day we go to the site. I've only covered 100% on six out of 52 data collection days. The average coverage per survey date is 47%. Therefore, the death toll could be as high as twice what we've reported!

2. Carcasses disappear from the road over time. @merav and I walked between Limekiln and Priest Rock trailheads one Saturday morning, and she 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."

3. 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.

4. 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 (which of course is highly variable across species and populations within species), 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."

* I've seen crows eating the newt carcasses on several occasions:
https://www.inaturalist.org/observations/19649069
https://www.inaturalist.org/observations/19649066
https://www.inaturalist.org/observations/19476078

* I've also seen beetles that appear to be eating newt carcasses:
https://www.inaturalist.org/observations/19375712
https://www.inaturalist.org/observations/19354057
https://www.inaturalist.org/observations/19184311

5. 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. There are a lot of them, but I can't even begin to quantify how many.

Posted by truthseqr truthseqr, April 13, 2019 11:44

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