Amy J. Lind

Multiscale habitat relationships of stream amphibians in the Klamath-Siskiyou region of California and Oregon

Regional amphibian distribution patterns can vary greatly depending on species and the spatial scale of inquiry (e.g., landscape to microenvironment). These differences appear to be related both to habitat selection among species as well as availability of suitable habitats across scales. We sampled amphibians in 39 second- and third-order streams in the conifer-hardwood forests of northwestern California and southwestern Oregon, USA (the Klamath-Siskiyou Region) during 1984 and 1985. We concurrently measured spatial, structural, compositional, and climatic attributes of the forest and stream environment-attributes representing landscape, macroenvironment, and microenvironment scales-to determine key habitat relationships. We captured 7 species, 97% of which were larval and paedomorphic Pacific giant salamanders (Dicamptodon tenebrosus) and larval and adult tailed frogs (Ascaphus truei). Streams in late seral forests supported both the highest diversity of amphibians and the highest densities of A. truei. Overall, A. truei distribution was patchy in occurrence, while D. tenebrosus distribution was widespread throughout the region at all scales. The incidence of A. truei was assessable at the landscape, macroenvironment, and microenvironment scales; however, variation in density was most predictable at the microenvironment scale. Changes in density of D. tenebrosus were detected only at the microenvironment scale. Tree size class and plant species composition variables distinguishing younger from older, more structurally complex forests, and forest microclimates and in-stream attributes best determined the presence and density for both life stages of A. truei. However, only in-stream conditions were good predictors of D. tenebrosus density. A. truei occupied a narrower range of habitat conditions than D. tenebrosus, exhibiting an ecological dependence on lotic and riparian environments found more reliably in late serai forests.

Habitat correlates of the southern torrent salamander, rhyacotriton variegatus (Caudata: Rhyacotritonidae), in northwestern California

Asystematic stratified sampling design was used to quantify the habitat relationships of the southern torrent salamander, Rhyacotriton variegatus, in northwestern California. We sampled 53 first to third order streams, each surrounded by at least 5-7 ha of relatively homogeneous forest or harvested forest habitat. Measurements of 121 attributes of the forest and stream environment were recorded in conjunction with area-constrained aquatic sampling for salamanders. A subset of 68 variables, grouped into 11 ecological components including attributes at the landscape, macrohabitat, and microhabitat scales, was used in a hierarchical analysis of habitat associations. Results from discriminant and regression analyses indicated that this species occurs within a relatively narrow range of physical and microclimatic conditions and is associated with cold, clear headwater to low-order streams with loose, coarse substrates (low sedimentation), in humid forest habitats with large conifers, abundant moss, and HO% canopy closure. Thus, the southern torrent salamander demonstrates an ecological dependence on conditions of microcli- mate and habitat structure that are typically best created, stabilized, and maintained within late seral forests in northwestern California.

Habitat Correlates of the Del Norte Salamander, Plethodon elongatus (Caudata: Plethodontidae), in Northwestern California

A stratified systematic sampling design was used to quantify the habitat relationships of the Del Norte salamander (Plethodon elongatus) in northwestern California. We sampled 57 sites, each within at least 5-7 ha of relatively homogeneous forest or post-forest habitat, where we measured 83 characteristics of the environment. Salamander sampling consisted of area-constrained sampling of 7 x 7 m plots with at least 25% rock cover at each site. A subset of 43 variables was used in a hierarchical analysis of habitat associations using discriminant analysis and regression. Variables included attributes at the landscape, macrohabitat, and microhabitat scales. Results indicate a significant association of the Del Norte salamander with older forests with closed, multi-storied canopy (composed of both conifers and hard- woods), with a cool, moist microclimate, and rocky substrates dominated by cobble-sized pieces. These habitat attributes appear optimal for survival and reproductive success throughout most of the range of this species. The Del Norte salamander may require ecological conditions found primarily in late seral stage forests.

Effects of Flow Regimes Altered by Dams on Survival, Population Declines, and Range-Wide Losses of California River-Breeding Frogs

Widespread alteration of natural hydrologic patterns by large dams combined with peak demands for power and water delivery during summer months have resulted in frequent aseasonal flow pulses in rivers of western North America. Native species in these ecosystems have evolved with predictable annual flood-drought cycles; thus, their likelihood of persistence may decrease in response to disruption of the seasonal synchrony between stable low-flow conditions and reproduction. We evaluated whether altered flow regimes affected 2 native frogs in California and Oregon (U.S.A.) at 4 spatial and temporal extents. We examined changes in species distribution over approximately 50 years, current population density in 11 regulated and 16 unregulated rivers, temporal trends in abundance among populations occupying rivers with different hydrologic histories, and within-year patterns of survival relative to seasonal hydrology. The foothill yellow-legged frog (Rana boylii), which breeds only in flowing water, is more likely to be absent downstream of large dams than in free-flowing rivers, and breeding populations are on average 5 times smaller in regulated rivers than in unregulated rivers. Time series data (range = 8 - 19 years) from 5 populations of yellow-legged frogs and 2 populations of California red-legged frogs (R. draytonii) across a gradient of natural to highly artificial timing and magnitude of flooding indicate that variability of flows in spring and summer is strongly correlated with high mortality of early life stages and subsequent decreases in densities of adult females. Flow management that better mimics natural flow timing is likely to promote persistence of these species and others with similar phenology.

GARTER SNAKE POPULATION DYNAMICS FROM A 16-YEAR STUDY: CONSIDERATIONS FOR ECOLOGICAL MONITORING

Snakes have recently been proposed as model organisms for addressing both evolutionary and ecological questions. Because of their middle position in many food webs they may be useful indicators of trophic complexity and dynamics. However, reliable data on snake populations are rare due to the challenges of sampling these patchily distributed, cryptic, and often nocturnal species and also due to their underrepresentation in the eco- logical literature. Studying a diurnally active stream-associated population of garter snakes has allowed us to avoid some of these problems so that we could focus on issues of sampling design and its influence on resulting demographic models and estimates. From 1986 to 2001, we gathered data on a population of the Pacific coast aquatic garter snake (Thamnophis atratus) in northwestern California by conducting 3-5 surveys of the population annually. We derived estimates for sex-specific survival rates and time-dependent capture probabilities using population analysis software and examined the relationship between our calculated capture probabilities and variability in sampling effort. We also developed population size and density estimates and compared these estimates to simple count data (often used for wildlife population monitoring). Over the 16-yr period of our study, we marked 1730 snakes and had annual recapture rates ranging from 13% to 32%. The best approximating de- mographic model for our data demonstrated higher survival rates for females than males and showed low and annually variable capture probabilities for both. Annual population size estimates (converted to linear densities), ranged from 58 to 131 snakes/km. Mean annual field counts typically accounted for only 5-10% of the total population size estimated using capture-recapture models. We found no evidence for a changing population size throughout the study. We found a positive relationship between sampling effort and capture probabilities. We evaluate survey design options that would help us approach recommended levels of capture probabilities and thus increase the precision of our estimates, allowing derivation of more complex demographic models. Our results should be useful in the development of monitoring programs for snakes and other secretive wildlife species and provide target demographic rate values for restoration of related at-risk snake species.

Population Ecology of two Relictual Salamanders from the Klamath Mountains of Northwestern California

We investigated the population ecology of the southern Olympic salamander (Rhyacotriton variegatus) and the Del Norte salamander (Plethodon elongatus) in the Klamath Mountains of northwestern California. A random stratified sampling design was used to investigate the distribution and relative abundance of subpopulations (metapopulation structure) of both species. We investigated specific demographic and other ecological aspects of one subpopulation of each species at sites with the highest relative numbers of each as revealed by the metapopulation analyses. Mark-recapture studies were conducted over 3 yr at these sites to gather ecological information on populations of these salamanders that appeared to exist in optimum conditions. We report data on population parameters, reproductive biology, movement, and growth. We offer this approach as a way to evaluate potential long-term viability of highly specialized or relictual species. We emphasize the importance of integrating site-specific ecological data with information on metapopulation structure at landscape and bioregional scales for conservation planning.

Parasitic Copepod (Lernaea cyprinacea) Outbreaks in Foothill Yellow-legged Frogs (Rana boylii) Linked to Unusually Warm Summers and Amphibian Malformations in Northern California

Abstract How climate change may affect parasite–host assemblages and emerging infectious diseases is an important question in amphibian decline research. We present data supporting a link between periods of unusually warm summer water temperatures during 2006 and 2008 in a northern California river, outbreaks of the parasitic copepod Lernaea cyprinacea, and malformations in tadpoles and young of the year Foothill Yellow-legged Frogs (Rana boylii). Relative to baseline data gathered since 1989, both 2006 and 2008 had significantly longer periods when daily mean water temperatures exceeded 20°C compared to years without copepod outbreaks. Infestation varied spatially in the watershed, as prevalence increased concomitantly with temperature along a 5.2 km longitudinal transect. At breeding sites of R. boylii with copepods in 2006, infestation ranged from 2.9% of individuals upstream to 58.3% downstream. In 2008, copepods were absent from the most upstream sites and infested up to 28.6% of individuals sampled at downstream locations. Copepods most frequently embedded near a hind limb or the cloaca. Among individuals with parasites in 2006, 26.5% had morphological abnormalities compared to 1.1% of un-infested individuals. In 2008 when the infestation peak occurred late in development (post Gosner stage 39), abnormalities were not associated with copepod infestation. In both years, recently metamorphosed frogs with copepods were, on average, slightly smaller than those not infested. These occurrences represent a sudden increase in local prevalence atypical for this river ecosystem. Previously we had only once seen copepods on amphibians (on non-native Bullfrogs, Rana catesbeiana), six km further downstream. Pacific Chorus Frogs, Pseudacris regilla, which co-occur with R. boylii in shallow near shore habitats were not used as hosts. The data suggest that increasing summer water temperatures, decreased daily discharge, or a combination of both, promote outbreaks of this non-native parasite on an indigenous host, and could present a threat to the long-term conservation of R. boylii under the flow regime scenarios predicted by climate change models.

Water Velocity Tolerance in Tadpoles of the Foothill Yellow-legged Frog (Rana boylii): Swimming Performance, Growth, and Survival

We explored the effects of large magnitude flow fluctuations in rivers with dams, commonly referred to as pulsed flows, on tadpoles of the lotic-breeding Foothill Yellow-legged Frog, Rana boylii. We quantified the velocity conditions in habitats occupied by tadpoles and then conducted experiments to assess the tolerance to values at the upper limit of, and outside, the natural range. In laboratory flumes and field enclosures we mimicked the velocities observed during pulsed flows. In all experimental venues, the behavioral response of tadpoles was to seek refuge in the channel substrate when velocity increased. In a large laboratory flume, tadpoles moved freely at low water velocities (0–2 cm•s−1) and then sheltered among rocks when velocity increased. In a smaller scale laboratory flume, the median critical velocity was 20.1 cm•s−1. Critical velocity varied inversely with tadpole size, developmental stage, and proportion of time spent swimming. Velocities as low as 10 cm•s−1 caused tadpoles approaching metamorphosis to be displaced. In field mesocosm experiments, tadpoles exposed to repeated sub-critical velocity stress (5–10 cm•s−1) grew significantly less and experienced greater predation than tadpoles reared at ambient velocities. Responses to velocity manipulations were consistent among tadpoles from geographically distinct populations representing the three identified clades within R. boylii. The velocities associated with negative effects in these trials are less than typical velocity increases in near shore habitats when recreational flows for white water boating or peaking releases for hydroelectric power generation occur.

Evidence of lingual-luring by an aquatic snake

-We describe and quantify the components of an unusual snake behavior used to attract fish prey: lingual-luring. Our earlier research on the foraging behavior of the Pacific Coast aquatic garter snake (Thamnophis atratus) indicated that adults are active foragers, feeding primarily on aquatic Pacific giant salamanders (Dicamptodon tenebrosus) in streambed substrates. Juvenile snakes, however, use primarily ambush tactics to capture larval anurans and juvenile salmonids along stream margins, behaviors that include the lingual-luring described here. We found that lingual-luring differed from typical chemosensory tongue-flicking by the position of the snake, contact of the tongue with the water surface, and the length of time the tongue was extended. Luring snakes are in ambush position and extend and hold their tongues out rigid, with the tongue-tips quivering on the water surface, apparently mimicking insects in order to draw young fish within striking range. This behavior is a novel adaptation of the tongue-vomeronasal system by a visually-oriented predator. The luring of prey by snakes has been associated primarily with the use of the tail, a behavior termed caudal luring (e.g., Neill, 1960; Greene and Campbell, 1972; Heatwole and Davison, 1976; Jackson and Martin, 1980; Schuett et al., 1984; Chizar et al., 1990). Greene and Campbell (1972) noted that caudal luring was a form of mimicry, which Schuett et al. (1984) called feeding mimicry. Lingual-luring behavior, analogous to that which we described here, has been described in the alligator snapping turtle (Macroclemys temminckii) (Drummond and Gordon, 1979) and the snowy egret (Egretta thula) (Buckley and Buckley, 1968). Most research on ophidian tongue use has focused on the chemosensory function of the tongue. In fact two reviews of the behavioral ecology of snakes make no mention of a lingualluring function (Mushinsky, 1987; Ford and Burghardt, 1993). However, Lillywhite and Henderson (1993) noted the occurrence of a prolonged extension of the tongue observed in vine snakes (e.g., Kennedy, 1965; Henderson and Binder, 1980), a behavior which is described in detail by Gove (1979). Lillywhite and Henderson (1993) listed prey luring as one of several possible hypotheses to explain this phenomenon (but see Keiser, 1975). We know of one other reference to a similar behavior in a laboratory setting (Czaplicki and Porter, 1974). Here we describe and quantify field observations of lingualluring by a snake for the first time. We have studied the natural history, behavior, and population dynamics of the Pacific Coast aquatic garter snake (Thamnophis atratus) along an approximately 5 km section of Hurdygurdy 68 H. H. WELSH AND A. J. LIND TABLE 1. Timed field observations of durations (in seconds) of lingual-luring behavior in the Pacific Coast aquatic garter snake (Thamnophis atratus) at Hurdygurdy Creek, Del Norte County, California. Each line represents a different individual. SVL = snout to vent (cloaca) length. Total obs. # of x length of Date Gender SVL (mm) time (min:sec) tongue-flicks tongue-flicks Min-max

Predation by Thamnophis couchii on Dicamptodon ensatus

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