October 18, 2020

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.

Posted on October 18, 2020 09:47 by truthseqr truthseqr | 4 comments | Leave a comment

October 16, 2020

When will the Lexington newts start migrating this season?

Michael Thomas Hobbs says the most important environmental factor that triggers breeding migrations for the related Santa Cruz Long-toed Salamander (A. m. croceum), is rainfall:
"With the first winter rains in November and December adults migrate en mass from their upland habitat to ponds for breeding (Reed, 1978). Breeding cannot commence until ponds fill and as such, adults do not emerge until the ground has saturated. Records show that when seasonal rainfall exceeds 10.7 cm (4.2”) adults are triggered to begin migrating, with continued rainfall needed to sustain the migration (Anderson, 1966)." pp 14-15
https://scholarworks.sjsu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=7936&context=etd_theses

Our rainfall records for the Lexington newts supports this assessment that approximately 4 inches of rain must fall before the newt migration commences.

Peter Claggett offers more insight into newt migrations in his paper:
Migration Patterns of Taricha torosa in Tilden Regional Park
https://nature.berkeley.edu/classes/es196/projects/1989final/ClaggettP_1989.pdf

Hobbs' thesis and Claggett's paper are very apropos to our project and make very interesting reading.

Posted on October 16, 2020 17:15 by truthseqr truthseqr | 2 comments | Leave a comment

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