Wild pigs (Sus scrofa) are one of the most invasive species of mammal worldwide. Introduced to California in the 1700s, and again in the 1920s, they have since been documented in 56 of the state's 58 counties. Pigs cause significant ecological and economic impacts through rooting, wallowing, and depredation and are extremely difficult to manage. The East Bay Stewardship Network comprises five agencies that collectively manage over 272,000 acres of public lands. These contain invaluable habitat for threatened and endangered species, drinking water for neighboring cities, and are maintained for recreational access. To protect these resources, the Network aimed to develop and operate an effective pig management program. Since the pigs that use Network properties are likely interconnected, a regionally collaborative pig management effort was warranted. We helped the Network develop a scientifically-backed and adaptive pig management plan. We collected and evaluated available pig presence data to better understand pig presence on Network and adjacent properties and generated a habitat suitability model. These analyses were used to inform the development of a collaborative effort to improve the efficiency and effectiveness of pig management and continue to provide adequate protection for sensitive resources at risk due to pig presence.

Invasive predators can negatively impact biological communities through top-down predation, but the ecological processes that shape the consumption of prey in novel communities are less understood. The “Enemy release hypotheses” and “Naïve prey hypothesis” are two explanations for why invasive species succeed in novel environments and, under these hypotheses, diets of invasive predators are expected to initially expand and then contract over time during invasion. Additionally, differing invader densities, and fluctuations in climactic and biogeographic conditions that shape prey community composition are likely to influence prey availability and selection, but the relative importance of these factors has yet to be tested. Here we used DNA metabarcoding on intestinal samples to determine diet composition and diversity of Barred Owls (Strix varia) within their native and invasive ranges. We present diets from 6 invasive populations in California, Oregon and Washington, and 1 native population in Minnesota and Wisconsin. Dietary diversity was greater in the invasive range across all taxonomic levels, with the leading edge of the invasion in California having the most diverse diet. Non-mammalian prey had higher importance in the invasive range, with amphibians and invertebrates represented most often.

American bullfrogs (Lithobates catesbeianus) are invasive in western North America and are well established in California, where they are widespread. This invasive species has been implicated in the decrease of native amphibian populations and is believed to have contributed to the decline of threatened and endangered amphibians regionally. We utilized air rifles, tin alloy pellets, and 2 shooters to systematically control bullfrogs in both lentic and lotic habitat types within 2 counties in California. We visited sites monthly (Apr. through Nov.) for approximately 8 and 14 years to lethally target and remove bullfrogs from aquatic habitat. The use of air rifles facilitated selective targeting; adult bullfrogs were initially targeted to break the reproductive cycle, with subadult bullfrogs secondarily targeted and removed when possible. Egg masses, when encountered, were also removed. Habitat type (lentic vs. lotic) did not appear to affect the results of the technique used. We considered bullfrogs under control when observed breeding adults were reduced by approximately 95% from original estimates, which occurred within 36 months for both sites. California red-legged frogs (Rana draytonii) were observed recolonizing the lotic site 12 months before bullfrogs numbers reached control levels. At the lentic site foothill yellow-legged frogs (R. boylii) colonized and reproduced in a pond 31 months following the onset of bullfrogs control. This technique appears to be highly efficient for bullfrogs control, which, if conducted effectively, may support colonization or recolonization of habitat by native anurans.