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:

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.

Posted by truthseqr truthseqr, October 18, 2020 09:47



@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.

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."

Posted by truthseqr 1 day ago (Flag)

i guess the same mentality could be used with our current pandemic.... ugh.

thanks for posting this anne

Posted by joescience1 1 day ago (Flag)

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.

Posted by newtpatrol 1 day ago (Flag)

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.

Posted by biohexx1 about 12 hours ago (Flag)

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