boreas halophilus) Science Foundation Chapter 5 Appendix 5.1 Case Study Northern toad (Anaxyrus boreas halophilus, formally Bufo

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1 Science Foundation Chapter 5 Appendix 5.1 Case Study Northern toad (Anaxyrus boreas halophilus, formally Bufo boreas Authors: Rachel Tertes 1 1 U.S. Fish and Wildlife Service, Don Edwards San Francisco Bay National Wildlife Refuge, 1 Marshlands Road, Fremont, CA DESCRIPTION OF THE SPECIES The California toad (Anaxyrus boreas is one of 3 subspecies of the western toad (Anaxyrus boreas). California toads are widespread throughout most of California, and are common in the Bay Area. They require a pond or wetland that retains water for at least 2 months for breeding, as well as upland refugia with ground squirrel or gopher burrows and vegetative cover for foraging and shelter (Mullally 1952). The toads are year-round residents and travel distances averaging 40m daily and annually travel 2.5km (Bartelt et al. 2004). Amphibians are declining worldwide at an alarming rate for a variety of reasons, such as urbanization, agriculture and associated pesticide drift, disease, UV-B radiation, land-use change and climate change (Davidson et al. 2002, Hof et al. 2011, Alford 2011). They are especially vulnerable to climate change due to their reliance on both aquatic and terrestrial habitats. This case study covers the California toad. The California toad, a subspecies of the well-researched western toad, has not itself been well studied. Western toads have experienced serious declines in Canada, Washington, Oregon and Rocky Mountains for a variety of reasons and may serve as proxy for California toads. CRITERIA FOR SELECTION OF THE GUILD Over the past decade, research has been conducted to identify the causes of amphibian decline, such as pathogens and UV Radiation. Pathogens have proven to have a strong negative effect on amphibians world-wide (Hof et al. 2011). While some amphibians have a strong resilience to pathogens, the western toad has a high susceptibility to viruses, bacteria, oomycetes, parasites (trematodes), and fungi (Deguise and Richardson 2009, Kiesecker et al. 2001, Johnson et al. 2001a, Pilliod et al. 2010). Below are two examples of pathogenic effects to western toads. Amphibian chytridiomycosis (chytrid)(caused by Batrachochytrium dendrobatis, Bd) is a pathogen implicated in amphibian declines and extinctions worldwide (Padgett-Flohr and Hopkins 2010, Blaustein et al. 2012). Bd is found in both ephemeral and perennial ponds and it affects all life stages of various amphibian species differently. Bd infects keratinized cells such as tooth rows and jaw sheaths in larvae, impairing foraging and proper development. Adult frogs may experience impairment of osmoregulation, electrolyte disruption, reduced fitness and mortality due to their keratinized epidermis (Blaustein et al. 2012). In western toads, chytrid causes high mortality and malformations in tadpoles (Blaustein et al. 2005). If the toads survive to Page 1 of 9

2 adulthood, they have a stronger resilience to chytrid. Pilliod et al. (2010) observed only a small 5-7% annual decrease in adult western toads survival in diseased populations and concluded that some amphibians may coexist with Bd. Trematodes enter limb buds and cause limb malformation and mortality in many anurans (Johnson 2001a). Similar to chytrid, interspecific effects of trematodes also varies. Trematodes caused low survivorship and malformations in larval western toads from Oregon (Johnson 2001a). Conversely, of four amphibians surveyed in California, trematode effects on California toads were less than the predicted 0-5% baseline (Johnson 2001b). This contrasted greatly with California newts (Taricha torosa) within the same ponds where larvae experienced an abnormality rate of 50% (Johnson 2001b). UV-B radiation has been implicated in reducing survivorship of adult western toads (Blaustein et al. 2005) and amphibians in general (Bancroft et al. 2007). Bancroft et al found that UV-B reduced amphibian survival by 1.9 fold and UV-B affected all life stages and species differently. When additional stressors were factored with UV-B radiation, survivorship decreased even more (Bancroft et al. 2007). For example, increased UV-B radiation increased susceptibility to oomycytes, thereby decreasing survivorship (Kiesecker et al. 2001). UV-B radiation has also been shown to increase the growth of the algae (Saprolegnia ferax) which infects communal egg masses such as those laid by the western toads (Kiesecker and Blaustein 1997) REVIEW OF CLIMATE CHANGE EFFECTS ON THE SPECIES Most ecoregions in the western hemisphere are projected to have at least 10% amphibian fauna turnover (low emissions scenario) and 30% turnover (higher emissions scenario) (Lawler et al. 2010). The San Francisco Bay area is projected to have a 30-50% amphibian species turnover (low to high emissions scenario, respectively) (Lawler et al. 2010). Decreased annual precipitation and increased temperatures, both effects of climate change, have already been observed causing amphibian declines at sites such as Yellowstone National Park (McMenamin et al. 2008). There are many components of Climate Change that will affect amphibians, such as change in precipitation patterns, increases in temperature, sea level rise, and increases in wildfires. When climate change effects are added to the already lengthy list of threats to amphibians, amphibians appear to have a perilous future. A decrease in precipitation, rather than temperature may be the largest cause of alarm for amphibians (Araujo et al. 2006). Changes in precipitation may cause earlier and faster drawdown, shortened hydroperiods (the length of time water is in a wetland), reduced number and depth of ponds/pools, increased probability of drying (preventing sufficient time for metamorphosis), alter spatial distribution of suitable and optimal breeding, foraging, dispersal, or overwintering habitats, facilitate pathogens and disease, increase UV-B radiation and advance receding shorelines (increasing exposure to aquatic predators) (Blaustein et al. 2012, Kiesecker et al. 2001, Bay Area Open Space Council 2011, Lee et al. 2015, Amburgey et al. 2012, Araujo et al. 2006). There is also the likelihood of reduction of habitat from conversion of more persistent wetlands to more ephemeral habitats (Lee et al. 2015). Temperature effects due to climate change are not solely about increasing air temperatures. For amphibians, increased temperatures can effect breeding phenology, development (including sex determination, growth rates and hatching rates), and increase disease and pathogens (Todd et al. 2011, Page 2 of 9

3 Blaustein et al. 2001, Blaustein et al. 2010, Blaustein et al. 2012, Bartelt et al. 2010, Eggert 2004, Padgett- Flohr and Hopkins 2010, Piotrowski et al. 2004). It can also alter hydroperiod and water quality, such as dissolved oxygen (Blaustein et al. 2010, Mills and Barnhart 1999). Temperature plays an important role in all aspects of the California toad s life. California toads have a very narrow body temperature range, between 10 C and 25 C (Smits 1984). Subterranean refugia (i.e. burrows) are important for hibernation, but also to insulate toads from extreme temperatures, both hot and cold (Smits 1984, Mullally 1952). Toads use temperature cues, rather than light, to emerge from burrows for diurnal activity (Smits and Crawford 1984) and hibernation (Browne and Paszkowski 2010). Temperature, and partially the moon, also influences spring migration (Arnfield et al. 2012). Salt water intrusion, causing increased salinity into freshwater systems, as well as inundation and loss of habitat, have been predicted as a result of sea level rise. In general, amphibians are poor osmoregulators. Increased salinity can affect all stages of reproduction and may include decreased size of tadpoles, malformations, delayed development and growth, low hatching success, and decreased survivorship (Karrakar et al. 2010, Gomez Mestre et al. 2004, Gomez-Metre and Tejedo 2003, Alexander et al. 2012, Rios-Lopez 2008). However, research, mostly conducted within the past 10 years, has identified an increasing number of amphibians, 100 species and growing, that have evolved a salt tolerance to exploit coastal and inland saline habitats (Hopkins and Brodie 2015). Western toads have an intermediate tolerance to saline environments and can tolerate up to about 12.5% of salt (approximately 400 mos). One observed effect of high salinity on western toad is a negative strike response. However the effect was only temporary and the toads improved accuracy as they acclimated to the hypersaline solutions (Dole et al. 1985). Overall, salinity may prove to be a very important factor for toads that live in the Baylands at the salt and freshwater confluence. Wildfires are predicted to increase due to climate change. Wildfire can cause both direct (mortality) and indirect (habitat change) effects on amphibians and their habitat. In contrast to many of the negative effects of climate change on amphibians, wildfire appear to have a positive or neutral effect on western toads by providing increased open areas for foraging, connectivity and dispersal (Hossack and Pilliod 2011). In addition, western toad occupancy and abundance in most habitats that were burned did not experience a decrease, nor did water temperature of ponds in burned areas influence colonization (Hossack and Corn 2008, Rochester et al. 2010). MANAGEMENT ACTIONS TO BE CONSIDERED 1. Establish buffers for ponds, including connectivity to uplands/terrestrial (ex. migration corridors), and suitable cover/refugia (non-breeding habitat). Western toads, similar to many amphibians, depend on both breeding ponds and upland refugia throughout the year. The area around ponds should include protective cover primarily to prevent desiccation. This terrestrial habitat should include underground burrows, downed wood and stumps for predator avoidance and to conserve body water. It should also include shrub and a mix of shady and open canopy cover (Bartelt et al. 2004). In the case of western toads in Idaho, the recommended buffer zone around breeding ponds should be at least 150 to 200m to protect the majority of toad movement. This is a site specific recommended buffer that includes essential non-breeding habitat. If the non-breeding habitat components mentioned above cannot be found near breeding ponds, then buffers will need to be increased to encompass adequate habitat. Breeding wetlands, migration corridors and non-breeding terrestrial habitat are equally important to the Page 3 of 9

4 survival of toads and each requires its own buffer and protection to be determined a case site by site basis (Fellers and Kleeman 2007). 2. Creation, enhancement and restoration of amphibian breeding sites. Heterogeneous temporary breeding sites with a variety of depths and diverse vegetation may increase resilience to increasing temperatures and changing hydrology (Shoo et al. 2011). By providing breeding ponds with both shallow and deep areas, as well as open and shady cover, amphibians at various lifestages can access the microhabitat they require. Plants such as sedges and grasses along shallow edges provide oviposition sites and proper temperatures for egg development (Semlitsch 2002). For example, western toads lay their eggs at a depth between 10 and 15cm (Hammerson 1999). Once the young metamorphose, they can move to deeper, less vegetated water for predator avoidance and thermoregulation (Semlitsch 2002). 3. Pond Location. In addition to current breeding pond locations, consider areas that may provide new opportunities, such as stream and creek mouths, and tidal wetland restoration projects with freshwater components. 4. Manipulation of hydroperiod. In some cases, ponds may need water management for supplemental water or excavation for longer hydroperiod (Shoo et al. 2011). Western toads need a minimum of 2 months of ponding to metamorphose, while other amphibians such as California tiger salamander need at least 3 months (Shaffer and Trenham 2004). Amphibian diversity can be maximized if ponds hold water for a minimum of 2 months and less than 1 year. Allowing ponds to dry annually prevents establishment of predatory fish and bullfrogs and decreases the spread of disease and pathogens (Semlitsch 2000, Semlitsch 2002). Rivers and stream conditions for amphibians may be improved through habitat restoration and modifying flows for breeding sites (Shoo et al. 2011). 5. Refuge assurance. Installation of microclimate and microhabitat refuges such as artificial wetting (ex. portable irrigation sprayers and misters), litter supplementation, artificial shelters (ex. coverboards and downed wood), and change in canopy cover (ex. increase cover by planting vegetation to decrease temperature in ponds) may be needed where other options are limited (Shoo et al. 2011). 6. Manage for multiple species. In general this is a good strategy and target species life histories and habitat preferences should be considered. In the case of western toads, managing lentic wetlands for both the California tiger salamander and the western toad is not recommended (Bobzien and DiDonato 2007). 7. Grazing. Maintain grazing regimes that support habitat for amphibians, reptiles, and grassland butterfly species. Avoid build-up of thatch and biomass, which degrade grasslands and reduce ground squirrel populations, which provide burrows for amphibians and prey for snakes (Bay Area Open Space Council 2011). 8. Invasive weeds. Control invasive weeds that crowd out native plants and alter vegetation composition and hydrology in native habitats (Bay Area Open Space Council 2011). DATA GAPS Page 4 of 9

5 a. Additional metapopulation studies of pond-dwelling species, such as California toads, California redlegged frog, and California tiger salamander are needed to guide landscape-scale pond management, restoration, and creation, and to provide estimates of metapopulation viability. b. We suggest conducting comprehensive reptile and amphibian surveys in the Bay Area and the creation of an online repository for this information, similar to California Avian Database Center. c. Map the occurrence of chytrid fungus, and estimate its current and potential impact on local amphibians. Minimize spread of the disease by implementing best management practices, such as washing field equipment and boots when conducting pond surveys (Bay Area Open Space Council 2011). d. In many cases, California toad data has informally been collected as incidental catch during listed species surveys, for example the comprehensive East Bay Regional Park District surveys (Bobzien, S and JE DiDonato 2007). We suggest compiling this and other California toad survey data to improve the range map to assist with conservation efforts. e. Provide an outreach and educational opportunity by creating a Citizen Science project to track toad observations. LITERATURE CITED AND RESOURCES Alexander LG, Lailvaux, SP, Pechmann, JHK, and PJ DeVries Effects of salinity on early life stages of the gulf coast toad, Incilius nebulifer (Anura: Bufonidae). Copeia, 2012(1): Alford, R Ecology: Bleak future for amphibians. Nature, 480: Amburgey, S, Funk, C, Murphy, M and E Muths Effects of hydroperiod duration on survival, developmental rate, and size at metamorphosis in boreal chorus frog tadpoles. Herpetologica, 68(4): Araujo MB, Thuiller W, and RG Pearson Climate warming and the decline of amphibians and reptiles in Europe. Journal of Biogeography, 33: Arnfield, H, Grant, R., Monk, C., and T. Uller Factors influencing the timing of spring migration in common toads (Bufo bufo). Journal of Zoology, 2012(288): Bancroft,BA, Baker, NJ, AND A.R. Blaustein A Meta-Analysis of the Effects of Ultraviolet B Radiation and Its Synergistic Interactions with ph, Contaminants, and Disease on Amphibian Survival. Conservation Biology, 22(4): Bartelt, PE, Klaver RW, and WP Porter Modeling amphibian energetics, habitat suitability, and movements of western toads, Anaxyrus boreas, across present and future landscapes. Ecological Modeling, 221: Page 5 of 9

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