DOES SEVERE DROUGHT EXACERBATE PREDATION BY NEWTS (TARICHA SPP.) ON AMPHIBIAN EGG MASSES?
|Jeff Wilcox; Sonoma Mountain Ranch Preservation Foundation; firstname.lastname@example.org;
Predation events that result in the mass mortality of amphibians are sporadically reported in the literature; most often involving predation of the terrestrial adult stage of biphasic amphibians by avian or mammalian predators. Recently, reports from multiple locations in California describe egg predation (oophagy) by adult newts (Taricha spp.) on the egg masses of California red-legged frogs (Rana draytonii), significantly depleting the number of developing ova or eliminating the egg mass altogether. Specifically, I will describe oophageal predation events that occurred concurrently at two ponds, by two species of newts (T. torosa and T. granulosa), on the Mitsui Ranch in Sonoma County, California in Spring 2021. Predation was not limited to the egg masses of R. draytonii, but occurred on three additional native amphibian species in one of the ponds and three species total in another. Predation enets occurred over a 6-week period, from February through April, during the most severe drought recorded on the Mitsui Ranch in 47 years of ownership. The Mitsui Ranch has hosted continuous research and monitoring teams since 2011, but this is the first observed incident involving significant oophagy by Taricha spp. I’ll discuss environmental, behavioral, and evolutionary factors that might lead to these mass predation events, and whether they could have long-term demographic effects on amphibian populations. Finally, I’ll discuss whether and when such events compel mitigating management actions.