Threat Impact CommentsTransportation corridors, Culverts and roads (from Howell and Roberts 2008): Culverts and roads can pose barriers to amphibian movement and an inability to disperse puts populations at risk because it limits gene flow and the ability to recolonize after disturbance (Jackson 2003). Specifically, culverts present barriers at outflow pipes where there are significant drops and where they have encouraged increased velocity of water above a surface that does not present any natural characteristics, such as instream structures or quiet pools, which would facilitate animal movement. Additionally, R. olympicus, given its close association to the stream channel and adjacent, saturated ground, may not likely move any significant distance upland to navigate around such barriers. These types of culverts have long been recognized as problems for fish and have only recently become more of a topic of concern for amphibians. It is not known to what degree culverts, and roads, fragment habitat for the Olympic torrent salamander as there have not been any studies on distribution specifically related to road locations. Nonetheless, Hayes et al. (2006) found that coastal tailed frogs (Ascaphus truei) engaged in upstream seasonal movements seeking invertebrate-rich intermittent headwater areas and Olson et al. (2007) speculated that similar environmental situations may exist for post-metamorphic torrent salamanders to do the same.
Biological Resource Use, Timber Harvest (from Howell and Roberts 2008): Raphael et al. (2002) conducted a retrospective study of the effects of six forest management conditions on a variety of species including R. olympicus. They found R. olympicus was significantly associated with older forest stands, in comparison to the other five stand conditions which all included some past forest management activities. Although the drivers of this relationship were not well examined, they found species associations with elevation, gradient, width, and stream classification.
On lands where harvesting timber is a management activity, the effects on other torrent salamander species, such as R. variegatus, have been confounded with natural variation in habitat quality (Diller and Wallace, 1996; Welsh and Lind, 1996; Hunter 1998). This, however, is not the case for the work done by Adams and Bury (2002) in Olympic National Park where timber harvest does not occur and where R. olympicus was still associated with coarse substrates and steep gradients in lower-order streams. Additionally, the species’ congener, Rhyacotriton cascadae, has been documented persisting in areas around Mt. St. Helens where there was complete vegetation removal following the 1980 eruption (Jones et al. 2005), so consequently, the degree to which timber harvest (i.e. human-caused removal of vegetation) plays a role in the distribution of R. olympicus is uncertain.
In general, the harvest of timber in riparian areas can affect the stream by increasing water temperatures (from canopy removal) and sedimentation. Based upon where R. olympicus has been documented (steep gradient systems with high flushing capacity), it is presumed that sediment input from ground disturbing activities would have a negative effect upon torrent salamanders. Likewise, in areas where timber harvesting causes increases in water temperature, decreases in oxygen, or increases in siltation, Rhyacotriton spp. have been rare or absent (Leonard et al., 1993). It’s possible, however, that for R. olympicus, this may not be the case since Adams and Bury (2002) did not find the species to be associated with canopy cover. Given the difficulty in distinguishing between intrinsic habitat limitations (eg. the requirement for environments provided by steep-gradient streams) versus areas affected by timber harvest (in some drainages on certain ownerships streams in steep areas may have been less likely to have been harvested in the past), there is a need to compare harvested and unharvested lower- and higher-gradient sites simultaneously (Lannoo 2005).
Natural systems modification, fire (from Howell and Roberts 2008): The effects to R. olympicus from fire are unstudied though it might be assumed that negative impacts could result from an infusion of sediment into the streams and changes in water temperature from the removal of canopy cover. The natural fire pattern in humid regions of the Olympic Mountains is large catastrophic events with long return intervals (Agee 1993). For this reason and because of the reduction in timber harvest over the past decade on federal lands, which had provided a large portion of the acres that were subsequently burned, as well as increased smoke management restrictions, the amount of landscape subjected to fire has markedly decreased and the impact of fire to R. olympicus should be minimal.
In terms of wildfire on private and state lands within the range of R. olympicus, the same will be true, that the effects should be minimal due to the relative rarity of natural events. As for managed fire, state forest lands in Washington typically only do pile burning after harvesting, or may remove a lot of the material for wood recycling at some facilities that have been established in recent years on the Olympic Peninsula (Bentley, personal communication, 2007). Broadcast burning is rare on state lands and only slightly less rare on private lands (there is one timber company on the peninsula that still conducts prescribed burns) largely due to regional smoke management restrictions. Given that R. olympicus reside largely in, or adjacent to, streams, where fuel moistures are higher, fire that does creep into these riparian areas will likely not completely consume the vegetation.
Pollution, chemical applications (from Howell and Roberts 2008): Herbicides, pesticides, fire retardants, salt, and fertilizers can all impact amphibians, particularly since these animals breathe through their skin which must stay moist and permeable. On federal lands, herbicides, used for such work as eradicating and minimizing the spread of invasive plant species, would be the chemicals most likely to impact amphibians. Herbicides, in a general sense, pose less risk to amphibians (than other types of pesticides) because they do not target species that have nervous systems. Most of the active ingredients in herbicides commonly used in Washington are not considered to be especially toxic to aquatic biota, but some (e.g. picloram and the ester formulation of triclopyr) can be toxic, especially at high doses or in the event of an accidental spill. Information about surfactants and other adjuvants is less well known. For example, the surfactant in Roundup®, rather than the glyphosate (the active ingredient), is known to be lethal to aquatic organisms, including frog larvae (Relyea 2005). Also, the petroleum solvent in sethoxydim is known to be toxic to aquatic organisms. Herbicides with known toxicity to aquatic organisms contain instructions on the label to avoid application to surface waters.
Disease and Predation (from Howell and Roberts 2008): Diseases in R. olympicus are unknown at present (Lannoo 2005). Nonetheless, in recent years, the topic of disease and amphibians has become a global concern and even more recently, a national one. Beginning in 1995, a series of mass salamander mortalities was documented across the U.S. Two iridoviri, Ambystoma tigrinum virus (ATV) (Jancovich et al. 1997) and Regina ranavirus (RRV) (Bollinger et al. 1999) have been isolated and implicated as the cause of these mortalities. Prior to this time, iridoviri were not known to infect salamanders, indicating that a new strain has developed and become virulent towards salamanders. Recent research by Jancovich et al. (2005) suggests that this disease is being spread via anthropogenic means, most likely live bait sales of salamanders. There have been no incidents of iridovirus-induced mass mortality in the Pacific Northwest, nor is there any indication whether stream salamanders are susceptible.
Additionally, a chytrid fungus, Batrachochytrium dendrobatidis, or “Bd” has also been implicated in the decline of amphibians (Berger et al. 1998). Pearl et al. (2007) sampled), and mortality has also been occurring (Olson, personal communication, 2007). It is possible that L. catesbeiana is a vector for Bd (Daszak et al. 2004) while itself being fairly resistant to the effects of the disease. The fact that L. catesbeiana has not yet been documented on most of the Olympic Peninsula is of benefit, and not just because of disease transmission, for numerous amphibian species.
Climate Change: Climate change is likely the biggest threat and the shift from snow-dominated delay water storage basins to rain-dominated basins as climate change progresses. Climate change is shifting snow-melt patterns, reducing snowpacks, and creating earlier shifts in streamflow peaks (Marc Hayes, Washington Department of Fish and Wildlife, pers. comm.).
Recent analysis of some of the vulnerable species to climate change: Case (2014) gave R. olympicus a score of 67, suggesting that it was the one of the top 20 amphibians and reptiles from northwestern North American species most susceptible to climate change impacts. Species that occupy sensitive habitats, such as the Olympic torrent salamander (headwater streams), Cascades frog and Van Dyke’s salamander (aquatic habitats) are generally ranked as highly sensitive to climate change (Halofsky et al. 2011).