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KEYWORDS: aquatic carnivore, citizen science, ecosystem restoration, Lontra canadensis, North American River Otter, San Francisco Bay Area, sentinel species, species recovery
We present results from the first-ever study of populations of the North American River Otter, Lontra canadensis, in coastal habitats of the San Francisco Bay Area, California. Historically extirpated from the region, wild populations of this sentinel carnivore appear to have made a recovery in recent years. Utilizing a citizen-science network paired with field investigations in 2012 and 2013, we documented 1374 River Otter observations across 8 of 9 San Francisco Bay Area counties. We demonstrate that River Otters are reproducing, and report here on the 1st sightings in decades in Alameda, San Francisco, and Santa Clara counties indicating a possible gradual expansion of the species' range southward. Within our Intensive Study Area in coastal Marin County, conservatively estimated densities ranged from 0.21 to 0.32 River Otters/km, with otters inhabiting a range of habitats from freshwater to marine. A pilot assessment of disease and mortality indicates that otters are being exposed to pathogens such as Vibrio and that observable mortality was largely due to car-strikes. We also report on timing of mating, timing of pup-juvenile emergence, and pup-juvenile production. Despite large-scale ecosystem restoration actions underway across the San Francisco Bay Area, River Otters have been overlooked by resource managers. Being apex carnivores that not only directly benefit from restoration actions but also likely play a significant role in the outcome of recovery actions focused on endangered salmonids and waterfowl, we strongly recommend attention to their potential role as a keystone species in the San Francisco Bay Area.
Tetrodotoxin (TTX) is a low molecular weight neurotoxin that is found in a wide variety of taxa. Tetrodotoxin blocks voltage-gated sodium channels, preventing the propagation of action potentials and inducing paralysis in susceptible animals. Taricha granulosa have been documented to possess TTX in high quantities and are preyed upon by snakes of the genus Thamnophis. However, recent observations of predation events on T. granulosa by otters were documented in a high-elevation population just outside of Crater Lake National Park, Oregon. We quantified TTX levels in this population as well as 3 populations in Crater Lake National Park using a Competitive Inhibition Enzymatic Immunoassay. We further compared these high elevation populations to a known high-toxicity population from Benton County, Oregon. We found that the populations in Crater Lake have lower levels of TTX relative to populations outside of the lake, and that all high-elevation locations have relatively low levels of TTX. We then analyzed previously published whole-newt TTX levels and elevation, and found that there is a significant negative relationship. However, there is a non-significant relationship between whole-newt TTX levels and elevation when examining elevations below 500 m. This further exemplifies the potential for novel predation and previously unidentified selective pressures in high-elevation newt populations.
A Corynorhinus townsendii maternity roost located in an abandoned ranch house in central California was monitored for 25 y. Prior to the discovery of the bats in 1987, the house was broken into regularly and disturbance levels were quite high. Upon discovery of the roost, the house was fortified and vandalism was greatly reduced. The number of females and the number of volant young greatly increased during our study and was directly correlated with the decline in vandalism. Bats emerged from the house 43.6 (± 10.9 SD) min after local sunset. Bats emerged later in the evening during spring and fall, when it was warmer, and when it was windier. We also evaluated duration of emergence (47.11 [45.0–49.7] min), and seasonal patterns of re-entry into the roost. Several factors suggested that potential predation, most likely by owls, influenced both the timing and duration of evening emergences.
We sampled 86 randomly selected survey plots to evaluate the distribution and abundance of Red Tree Voles (Arborimus longicaudus) on the Tillamook and Clatsop State Forests in the northern Coast Ranges of Oregon in 2011–2013. We conducted surveys by visually searching for tree vole nests while walking along 500 m of transect in each plot. Trees with potential nest structures were climbed to determine if the structures were tree vole nests. We found tree vole nests in only 4 random plots, all of which were located near the coast, at the western edge of the Tillamook State Forest. Of 33 tree vole nests located, 20 (61%) were in old forests (≥80 y old), and 13 (39%) were in 1 plot in a young forest that was 65 y old. We concluded that tree voles were absent from most of the Tillamook and Clatsop State Forests, probably due to the fact that most of the area was either logged or burned in the early 1900s, and subsequently intensively managed on short rotations. We also suggest that remnant stands of old forest on Bureau of Land Management and state lands are acting as source populations from which tree voles populate adjacent young forests. Cuttings found in nests provided evidence that most of the voles were feeding on needles of Western Hemlock (Tsuga heterophylla) or Sitka Spruce (Picea sitchensis).
Winter survival of Rocky Mountain Mule Deer (Odocoileus hemionus hemionus) depends on an energy conservation strategy. However, not all Mule Deer habitats are equivalent; slope, cover, weather conditions, and other factors contribute to differences in habitat use patterns and behavior among wintering populations. We studied Mule Deer on the East Front of the Rocky Mountains, Montana, and Warm Springs and Sink Creek, east-central Idaho to determine how weather and different habitats affect their winter habitat use. We located radiocollared adult female Mule Deer and collected data on weather, landscape, cover, and forage variables at locations used by deer, and at random locations during winter 2010–2011. Deer used different habitat components on the different winter ranges. On the East Front, forage, cover, and environmental conditions affected probability of deer use, and these covariates changed in magnitude depending upon weather conditions and deer behavior. In Idaho, cover and forage variables were important predictors of Mule Deer habitat use, and habitat use differed between Idaho study areas. In Warm Springs, covariates related to foraging predicted habitat use, whereas in Sink Creek covariates related to thermal or hiding cover predicted habitat use. Differences among all 3 study areas suggest that deer use different habitat components under different winter conditions. Discrepancies in habitat use among winter ranges are important when considering habitat requirements and habitat management for Mule Deer.
Cusk-eels and brotulas of British Columbia have been poorly studied, and until now, there were published records of only Spectrunculus grandis and Brosmophycis marginata from our waters. However, a single specimen of S. crassus has been identified from among the few S. grandis from British Columbia held at the Royal British Columbia Museum. Furthermore, increased sampling effort from deep-water surveys, shrimp surveys, and the commercial fishery revealed 5 additional cusk-eel species and 1 brotula offshore of British Columbia. Two specimens of Chilara taylori were collected from the southern Strait of Georgia at depths of 78 to 109 m. A single specimen of Acanthonus armatus was taken from near Triangle Island at 1778 m and is the 1st record for the eastern North Pacific Ocean. One specimen of Cherublemma emmelas was found at 1097 m in Kyuquot Canyon, west of Vancouver Island; 4 specimens of Bassozetus zenkevitchi were collected from depths of 1909 to 2125 m west of Vancouver and Graham islands; and a specimen of Cataetyx rubrirostris from 2000 m and a Porogadus promelas from 1967 m were taken in Queen Charlotte Sound, east of the Tuzo Wilson Seamounts. Because of increased sampling effort from 1999 to 2007, we now understand the number of cusk-eels and brotulas in British Columbia to be 9 species.
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