Salamanders in Crisis!
An Overview of Why Salamander Conservation is Needed
by Matt Ellerbeck, Salamander Conservationist
Although they are rarely given much thought, and often overlooked when they are, salamanders are in a terrible crisis. Around half of all of the world’s salamander species are listed as threatened by the International Union for Conservation of Nature. These species are all facing a high risk of extinction. A further 62 species have been designated as near-threatened with populations rapidly dwindling. This means they are quickly getting closer to threatened status and to the brink of extinction. Sadly for some salamanders it is already too late, as both the Yunnan Lake Newt (Cynops wolterstorffi) and Ainsworth’s Salamander (Plethodon ainsworthi) have already gone extinct.
Salamanders have been on the earth for over 160 million years, and the terrible state that they now find themselves in is due to the detrimental acts of humans. Even those species that are not experiencing population declines deserve attention and conservation to ensure that they remain healthy and stable.
For many people the thought of declining species conjures up images of exotic animals found in far-away lands. However, Ontario is home to many salamander species. These include the Blue-Spotted Salamander (Ambystoma laterale), Eastern Red-backed Salamander (Plethodon cinereus), Four-toed Salamander (Hemidactylium scutatum), Northern Two-lined Salamander (Eurycea bislineata), Spotted Salamander (Ambystoma maculatum), Northern Dusky Salamander (Desmognathus fuscus), and many more!
Several of Ontario’s salamander species have be designated as Species at Risk. Examples include the Allegheny Mountain Dusky Salamander (Desmognathus ochrophaeus), the Jefferson Salamander (Ambystoma jeffersonianum), and the Small-mouthed Salamander (Ambystoma texanum). Even more devastating is the fact that two salamander species that used to exist in Ontario have been completely exterminated from the province. The Eastern Tiger Salamander (Ambystoma tigrinum) and the Spring Salamander (Gyrinophilus porphyriticus) are both listed as Extirpated (extinct in Ontario).
One of the biggest issues affecting salamanders is the loss of their natural habitat. Many areas that were once suitable for salamanders have now been destroyed for developmental construction and agriculture. Habitats of all kinds are being lost at an alarming rate; wetlands are drained, forests are cut down, and waterfronts are developed. Salamanders are literally losing their homes and they are losing them rapidly. The expansion of urban areas threatens the suitable habitats that still remain.
Where natural habitats do still exist, they are often fragmented or degraded. Fragmentation occurs when healthy areas of habitat are isolated from one another. These fragmented areas are known as habitat islands. Salamander populations are affected since gene flow between the populations is prevented. This increases the occurrence of inbreeding, which results in a decrease in genetic variability and the birthing of weaker individuals. Fragmented populations where inbreeding occurs often end in a genetic bottleneck. This is an evolutionary event where a significant percentage of the population or species is killed or otherwise prevented from reproducing. Habitat fragmentation is also harmful because it often eliminates crucial requirements in the area which are critical to the survival of salamander populations. Such areas include spaces that can be utilized for thermoregulation, prey capture, breeding, and over-wintering. Without such habitat requirements populations dwindle.
Breeding sites, often in the forms of vernal pools, are particularly important. The loss of such areas due to habitat destruction can negatively affect the entire population and its reproductive output. According to the Committee on the Status of Endangered Wildlife in Canada, there is some evidence that certain salamander species have individuals that return to the pond in which they were born once they reach maturity. Therefore, destruction of a breeding pond may result in the loss of the entire population returning to that site. Habitat complexity is also important as complex habitats offer shelter to salamanders from both predators and human persecution.
Degradation occurs when the natural habitat has been altered and degraded to such a degree that it is unlikely that any remaining salamander species would be able to survive. Development projects and agriculture near fragmented habitats put salamanders at serious risk. As amphibians, salamanders have extremely absorbent skin. Industrial contaminants, the introduction of sedimentation into waterways, sewage run off, pesticides, oils, and other chemicals and toxic substances from developmental construction sites and human settlements can all be absorbed by salamander skin. This can quickly lead to poisoning or death. Chemical contaminants can also cause deformities to occur. A study conducted at Purdue University found that out of 2,000 adult and juvenile salamanders, 8 percent had visible deformities. Habitat destruction and degradation can also affect the availability of prey items, causing unnatural declines in appropriate food sources.
According to Save the Frogs, Atrazine (perhaps the most commonly used herbicide on the planet, with some 33 million kg being used annually in the US alone) can reduce survivorship in salamanders. Many products are sold with the claim that they are eco-friendly. However, these claims should be viewed with caution. For example, according to N.C. Partners in Amphibian and Reptile Conservation, Roundup and many other surfactant-loaded glyphosate herbicide formulations are not labeled for aquatic use. When these formulations are applied to upland sites according to label instructions, the risk to surfactant-sensitive species is considered low. While this may be the case for fish, it does not necessarily apply to amphibians. Salamanders that breed in water routinely use non-aquatic areas and could easily be exposed to glyphosate formulations that contain harmful surfactants through direct contact and not just incidental drift.
In addition to habitat degradation issues caused chemical contaminants, habitats are often isolated and cut off from one another by the roads and highways that run through them. Countless numbers of salamanders are killed on roads and highways every year when they are hit by vehicles. Salamanders that are migrating to breeding and egg-laying sites, or salamanders in search of new habitat, must often cross over roads to reach suitable areas. Here many of the mature members of the adult breeding population are killed. Removing members of the breeding population greatly limits reproductive output and makes it much more difficult for salamander populations to recover.
Roads present an additional problem because they represent a form of habitat loss. The roads that run through natural areas fragment existing populations, effectively shrinking the number of individuals in a population that are able to interact. This limits natural gene flow and genetic diversity between the isolated population members on either side of the road, and can greatly increase the population’s chances of extirpation.
A 2005 article in Wetlands Ecology and Management proposed that, for adult spotted salamanders, an annual road mortality rate of greater than 10% can lead to local population extirpation. It is estimated that road mortality rates can approach 100%, meaning populations are at extreme risk of extirpation and extinction due to road mortality. Wyman (1991) reported average mortality rates of 50% to 100% for hundreds of salamanders attempting to cross a paved rural road in New York State. Given that this figure pertains to a rural area over a decade ago, it is fair to assume that even higher mortality rates may occur today as the number of cars on our roadways steadily climbs from year to year. Reducing road mortality is paramount to preserving salamander species.
Being hit and killed by vehicles is not the only threat that roads create for salamanders. Chemical run-off from vehicles contaminates roadside ditches and pools. These sites are often utilized by salamanders for breeding and birthing. According to a recent study published in Scientific Reports, salamander survival in roadside pools averaged just 56%, as compared to 87% in woodland pools. The study also reported that an average of 36% fewer individual embryos survived to hatching in roadside versus woodland pools.
Salamanders are also threatened when they are harvested from the wild. Salamanders are taken for the pet trade, for food markets (mudpuppies), and for use as fishing bait.
There is much about salamanders that scientists do not know. Aspects of the biology, ecology, and lifestyles of many species are still a mystery. This undoubtedly means human interference is negatively affecting salamanders in ways in which we don’t even know. One thing is for sure – the intricate relationship between all species and the vital roles they play within ecosystems is being altered. Such alterations can have serious consequences to not just salamanders, but many other animals as well, including humans.