Lexington Newt Population Study (2020-2021)
A Pacific Newt population study will be conducted by HT Harvey & Associates in collaboration with Peninsula Open Space Trust (POST) and Midpeninsula Regional Open Space District (MROSD) for the migration season starting late November 2020 and ending sometime between April and May 2021. Daily field operations will be led by a biologist from one of the above agencies paired with volunteers.
The study protocol is considered proprietary (POST asked @merav to review it, but no one else on our team has seen it). However, you can read their public-facing request for funding here:
https://www.openspace.org/sites/default/files/20200923_Agmt_NewtMortalityPopulationStudyAlmaBridgeRd_R-20-104.pdf
The study objectives are as follows:
"The planned newt population and mortality study will estimate the number of adult newts attempting to cross Alma Bridge Road to breed in Lexington Reservoir and the percentage that are killed by vehicular strikes during a single breeding season. The data will be analyzed through a model to characterize this percentage relative to long-term impacts on the local newt population... The report will also provide daily levels of vehicular traffic and how these levels compare with levels of newt movement. "
The study was prompted by Santa Clara County Roads, Parks, & Water departments who stated that "further study is needed to better understand the issues..."
The HT Harvey analysis of our 2018-2019 roadkill data found "a concentration of mortality along a few road segments" which they deem "Extremely High Mortality." See the map attachment in the above memo. They will install pitfall traps along six 100 ft. sections of road (0.1 mile) for their study. Please be aware that our team has found newt roadkill along all 4.1 miles of our study area.
The HT Harvey team started field work building their pitfall traps the week of 10-14-20. Merav spoke with Jeff Wilkinson to coordinate the efforts between his team and ours.
Kommentit
@merav, @sea_kangaroo, @newtpatrol, @joescience1, @anudibranchmom, @biohexx1, @tyap, @karangattu
If you haven't joined the new project for the upcoming migration season, please do so. Also, please join the umbrella project so you can have easy access to all the subprojects.
https://www.inaturalist.org/projects/pacific-newts-dead-2020-2021-lexington-reservoir
https://www.inaturalist.org/projects/pacific-newt-roadkill-lexington-reservoir
Regarding the population analysis performed by J. Wilkinson (HT Harvey & Associates, Aug. 2, 2019) using the modeling software by Gibbs and Shriver (2005), my memory fails me so I looked up the exact numbers. These are all estimates (J. Wilkinson gave a long discussion of why he chose these numbers):
Starting population = 15,000 (arbitrary number, ~3.7 times the number of newts killed during the 2018-2019 breeding season)
Carrying capacity of the reservoir as the larval habitat of 2,000,000
Starting adult annual survival rate of 0.9, without mortality from vehicular strikes due to predation, disease, etc.
The report stated: "We do not know whether the observed road mortality on Alma Bridge Road is sufficient to pose a significant risk to the viability of the local newt population..."
"As an exercise, if we were to assume the 45,665 adult population size prior to construction and use of the road, and use the 4,042 number that was tallied this year by Anne to reduce the survival rate due to road mortality to 0.811, the adult population size would plateau at 31,580 after 63 years. This seems plausible because the reservoir and road have been in use for 67 years, yet road mortality of this magnitude is still being observed. If this mortality were to cause a substantial reduction in, or even the extirpation of, this Lexington Reservoir population, the loss of this one population would have a minimal effect on region-wide populations, as this species is common throughout the hills and mountains of the Bay Area."
i guess the same mentality could be used with our current pandemic.... ugh.
thanks for posting this anne
That mentality is also what leads to extinctions. We decimate the populations little by little, and each little bit doesn't seem like it matters, until it does, and either they're gone or on the endangered species list and now we have to put so much more time, effort and resources into bringing them back than we would have to keep them thriving in the first place. This way of thinking needs to change if we're going to regain balance with the rest of the planet.
Newtpatrol, you are correct. You can see urban sprawl and its consequential increase in traffic. Pollution takes effect as well. Newtpatrol also mentioned population density the other day.
There was a time when zero newts were killed by traffic, then maybe 100 per year, then 500 per year, then a thousand per year, til the number we're at today. The number of roadkill deaths will increase with an increase in usage of the reservoir.
@biohexx1, what you said makes so much logical sense to me. Why didn't J Wilkinson take that into account in his first population modeling? He just assumed 5000 newts were being killed from Day 1 after the road was built. It seems such analyses would be more robust with feedback like this from the team. That first analysis was flawed. Hopefully he will take all this into account with his second analysis after collecting data this year. Hopefully @merav will be able to review his report before it's released to the "partners" this time.
That's why we meet and strategize! Together we will come up with a good mitigation plan.
I'm going to speak today at Supervisor Ellenberg's meeting at noon (district 4). I would like to ask her why they are repaving the road without doing anything for the newts. They still have half of the road to repave, so maybe it's not too late? I'm guessing it is too late, but I'd like to at least say something about it. When I was there yesterday I thought it was crazy they are doing nothing for the newts. I'm sure the most expensive part in adding an underpass for newts is repaving the road. Since they are already doing that, they could have added pipes or something, or fix a few culverts.
Wow! Thanks so much, @merav!
When I started this project, I didn't know who to report it to or who had the power to do something about it. Linking up with you and Shani @ Audubon was the best thing for the newts. You two know all the players and how to get things accomplished. Thanks a million!
I have no idea either. It was Shani's idea :)
What did the Supervisor say, @merav?
I was the last one to speak, so she didn't get a chance to reply. But Harry Freitas from County Roads was there, and he said how he feels sorry for the newts, and how complicated it is to implement a solution to this problem, and that he's working with the population study and provides funding for something. So, he didn't say much, but I think it's good that the supervisor is now aware of the problem, Shani hasn't communicated with her before about this. I might ask for a personal meeting with her.
@merav, are Midpen & HTH sharing all their pictures with you? To date, it looks like they've only shared pictures for 5 of the 22 days since the newts first appeared. Their team recorded 21 out of 136 (15%) of the newt deaths in Nov. Does that sound reasonable for the "extremely high mortality" sections of the road?
I haven't seen any photos of live newts. Are they catching any live ones in the pit traps? Are they photographing them?
Let me know if you need help processing pictures.
I think you made a very wise decision to continue your surveys throughout this season. Otherwise, the roadkill stats might be very skewed.
I agree - I'm really glad we're continuing the survey. And the data, as always, is really interesting. With so little rain a few weeks ago, we still see newts out and about (or dead on the road).
They are supposed to be sharing all their photos, but there are some missing, others are missing data. I will contact them today to try and fix that. I had a meeting with Neal earlier this week about this, so I hope it will help.
I'm not sure how they document the live newts. I do know they had over a hundred live ones so far, but I think that was only around the rain event.
@merav, thanks for staying on top of this. Like all of us, it might take a little while for them to get into the swing of things.
Wow - 100 live newts! That's happy news. But with 21 dead ones, that means ~17% mortality for the first half of their trip, which is terrible news!
these are not exact numbers. I don't have the current numbers, and I'm not sure I'd post them here.
I am uploading 6 more photos now. Two of them are duplicated of observations I've already uploaded. Our photos are better, so I wonder what would be best to do with the pairs of observations? Should I remove one of them from the project but link to the observation, or delete from iNat?
here are the latest additions: https://www.inaturalist.org/observations?created_on=2020-12-10&place_id=any&subview=grid&taxon_id=27816&user_id=merav&verifiable=any
@merav, I agree that our team's photos are much better. I understand that the numbers aren't exact.
Use your best judgment about how to handle the duplicates. You could even use both photos in one observation with a comment that one was taken by you, the other by the Midpen/HTH team.
yes, I was thinking about using both in one observation. I think that makes sense, and would be less confusing
@merav, I created a new project for the Midpen population study because I think it's going to be very hard to track which observations are from them and which are from our team. When you upload their photos, could you please add them to the following project?
https://www.inaturalist.org/projects/pacific-newts-population-study-2020-2021-lexington-reservoir
Question: Should we include the Midpen numbers in our total number of roadkill project for this season, or should we keep them separate? I'm thinking we should include them in our project as well so we get a total roadkill count for the entire road that can be compared with previous years. What do you think?
I think it's a good idea to separate the observations. I think we should remove them from the regular project, and then we can decide if we add them to different analyses and such. It might also help with comparing duplicates.
In general, I think we need to include the HTH numbers in our totals, or we won't have a complete dataset. It will indeed allow us to compare this year with previous years, which is very important. Separating them artificially might be helpful though.
@merav, I thought about creating an umbrella project that combines our 2020-2021 data with Midpen's, but then we can't add it to the existing umbrella project. Please take a look at the project I set up. I left all Midpen observations in our project for now. We can decide if/when they should be removed from our project.
https://www.inaturalist.org/projects/pacific-newts-population-study-2020-2021-lexington-reservoir
i'm afraid the numbers will be drastically different given the impediment to crossing that the silt fencing creates. theoretically 1/2 the newts in any given section are blocked from the road.
we'll see how the numbers play out over the season, but on saturday the north section appeared to have multiples more heading up slope (caught on the reservoir side buckets) that down slope, which create artificially low numbers. at some point the tide will wash the other way and the numbers of killed will increase as others migrate downslope to breed.
@joescience1 - could you add a note on the observations that were found near the population study? Hopefully they were documented later on that day, and will become duplicates once I'm able to upload their observations.
I agree that their study will affect ours, but we can't do much about that, other than try documenting everything the best we can.
@joescience1, @merav, I've been thinking about the population study, too, and how it will affect our study.
My profession was in biotech software engineering, not science per se, but I seem to remember rules about designing experiments such that the experiment itself does not affect the data. In the case of this population study, the experiment is definitely affecting the data as Joe pointed out in his comments above. And, unfortunately, it's adversely affecting our study as well. Hopefully, some good will come of it, such as getting a better understanding of the percentage of the population being killed on the road plus maybe getting the newts on the CA species of special concern list.
@joescience1, that's a very interesting observation you made - that there are multiple more live newts in the buckets on the reservoir side of the fence. I wonder why? Could you tell if they were juveniles trying to return uphill to their terrestrial habitat?
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