Saving California Newts Two Models at a Time

Start: 03/22/2017 - 4:15pm
End  : 03/22/2017 - 5:15pm


Courtney Davis (Pepperdine University)

Santa Monica Mountain (SMM) streams are home to the California newt (Taricha torosa), a species of special concern in California.  Our historically severe drought as well as stream invasion by nonnative crayfish (Procambarus clarkii) that prey upon newt eggs have decimated local newt reproduction.  This has led to localized newt extinctions in some SMM streams.  Restorative measures are currently underway in some SMM streams to remove crayfish through trapping in order to prevent or slow the decline of native species.
In collaboration with biologists and undergraduate mathematics students, we have created discrete mathematical models to study the population dynamics of the California newt under drought and crayfish predation.  In this talk, I will describe how we construct two nonlinear systems of discrete equations that include demographic parameters such as survival rates for newt life stages and egg production, which depend upon habitat availability and rainfall. We estimate these demographic parameters using 15 years of stream survey data collected from SMM streams.  Our models capture the observed decline of the studied newt population and replicate crayfish trapping data.  Our drought model makes predictions about how the length and severity of drought can affect the likelihood of persistence and the time to critical endangerment of a newt population.  With our crayfish trapping model, we evaluate the persistence or the time to extinction for newt populations under crayfish trapping regimes when varying the quantity of trapping resources, frequency of trapping implementation, and susceptibility of the crayfish population to trapping. Predictions made with both models inform restorative efforts and crayfish management.


Shanahan B460, Harvey Mudd College

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