This extended abstract was originally submitted to The Effects of Oil on Wildlife Conference in Anchorage, Alaska in 2015. It was later presented at the Oiled Wildlife Care Network’s Oilapalooza conference in Emeryville, California in 2015 and again at the National Wildlife Rehabilitators Association Symposium in South Padre Island, Texas in 2020.
Author’s current contact information: Samantha Christie Wildlife Care Specialist Oiled Wildlife Care Network [email protected] (530) 752-5035
Considerations for Treating Oiled Amphibians
Samantha Christie Tri-State Bird Rescue & Research, Inc., 170 Possum Hollow Rd, Newark, DE 19711 USA
Abstract Wildlife care professionals have had many opportunities to demonstrate success in caring for, cleaning, and releasing a variety of oiled wildlife species. As the majority of oiled wildlife treated during a response are birds, avian cleaning and rehabilitation techniques have been regularly practiced and honed to a level of expertise by oiled wildlife responders internationally. The same can be said, to a lesser degree, of the techniques employed for treating oiled aquatic mammals and reptiles. Far fewer advancements have been achieved in the study of lesser-known biota. There are numerous challenges in relation to studying the effects of oil on all species, however those obstacles are amplified in species that command little public interest for conservation. In the interest of preserving biodiversity, it is prudent to also study these less charismatic species.
Unlike the other classes of tetrapod, amphibian species have generally been overlooked in terms of oil contamination and response strategies. There are few documented cases of oiled amphibians receiving treatment in an oiled wildlife response facility. Consequently, the effects of oil spills on amphibians are not well understood. An Ohio oil pipeline release in 2014 produced an opportunity for Tri-State Bird Rescue and Research, Inc. to develop and document procedures for the care of impacted salamanders and frogs. Plans to mitigate the oil’s impact on wildlife were complicated by the salamanders’ natural breeding behaviors, which presented a perpetual risk of new animals becoming oiled as they entered the contaminated zone to spawn. Responders faced unique challenges including nocturnal field surveys, preemptive capture for clean animals, treatment of secondary injuries due to oil remediation techniques, and long-term care for salamanders when release habitat criteria could not be met.
Introduction Amphibians have become an icon for the current biodiversity crisis. At least 159 amphibian species are known to have gone extinct in recent decades (Stuart et al., 2008). Without rapid intervention, the threats to their survival are expected to cause a further loss of species and genetic diversity (Stuart et al., 2006). A successful approach to addressing this global crisis will require a coordinated response from stakeholders within the conservation, academic, government, and private-sector communities (Stuart et al., 2006). Oiled wildlife experts have a role to play in contributing to this common goal.
Amphibian Population Decline Amphibian population decline is a global and rapidly growing concern for conservationists. In 2004, the International Union for Conservation of Nature (IUCN) conducted a comprehensive World Conservation Union Global Amphibian Assessment (GAA) that gathered data on distribution, population trends, and threats. The assessment indicates that amphibians are significantly more threatened than either birds or mammals (Stuart et al., 2006). A 2008 update to the GAA found that 32% of amphibian species are threatened and at least 42% of all amphibian species are declining in population (Stuart et al., 2008). Familiar threats including habitat loss, disease, and pollution are believed to be widely responsible for much of the current population trend; however, many species are declining for unknown reasons (Stuart et al., 2008).
The current amphibian extinction rate is dramatically higher than the reported background extinction rates suggesting that the current population declines cannot be explained by natural fluctuation (McCallum, 2007). Many population declines are attributed to climate change, habitat loss, over-exploitation, and other anthropogenic threats (Mendelson et al., 2006). Other declines are poorly understood which is problematic for the development of management plans and conservation strategies (Stuart et al., 2006).
The Effects of Oil on Amphibians Wildlife care professionals have had many opportunities to demonstrate the success of oiled bird rehabilitation. As the majority of oiled wildlife treated in rehabilitation facilities are birds, developments in avian rehabilitation procedures have been plentiful. Far fewer advancements have been achieved in the rehabilitation of lesser-known biota. There are numerous challenges in relation to studying the effects of oil on all species, however those obstacles are amplified in species that often command little public interest for conservation. In the interest of preserving biodiversity and contributing to larger conservation goals, it is prudent to also study these less charismatic species.
Cleaning and rehabilitation techniques for oiled birds have been practiced regularly and honed to a level of expertise by oiled wildlife responders internationally. The same can be said, to a lesser degree, of the techniques for treating some oiled aquatic mammals and reptiles. Unlike the other classes of tetrapod, amphibian species have generally been overlooked in terms of oil contamination and rehabilitation strategies. Scientific studies evaluating amphibian response to petroleum exposure are largely focused on larval growth delays and metamorphic effects and are not well characterized. Despite known occurrences of amphibian mortality events resulting from oil spills, there are few documented cases of oiled amphibians receiving treatment in a wildlife rehabilitation facility (Hoffman et al., 2003). Consequently, the direct effects of oil spills on adult amphibians are not well understood.
The literature reflects a lack of information on the ecotoxicology of oil on amphibians (Sparling et al., 2010). Past and present amphibian ecotoxicology research interests seem to be focused on the implications of chronic oil presence in the environment, rather than the direct effects of oil exposure on individual animals. Compared to the threats of habitat loss and emerging diseases, oil mortality may be a fairly minor stressor for amphibian populations, however, there is value in developing this area of study.
2014 Pipeline Release Case Study An oil pipeline release in 2014 produced an opportunity for oiled wildlife responders to develop and document procedures for the care of impacted salamanders and frogs. Plans to mitigate the oil’s impact on wildlife were complicated by the salamanders’ natural breeding behaviors, which presented a perpetual risk of new animals becoming oiled as they entered the contaminated zone to spawn. Responders faced unique challenges including nocturnal field surveys, preemptive capture for clean animals, treatment of secondary injuries due to oil remediation techniques, and long-term care for salamanders when release habitat criteria could not be met.
On 20 March 2014, Tri-State Bird Rescue & Research, Inc.’s Oil Spill Response Team (Tri- State) was mobilized to respond to a pipeline release in southwestern Ohio. The release of crude oil originated near a creek within a nature preserve. Oil flowed down approximately 3,000 linear feet of stream and terminated in a vernal pool. Tri-State’s team was mobilized out of concern for the native amphibian population. Tri-State managed the rehabilitation of affected animals and collaborated with the stakeholders to address wildlife concerns throughout the response.
Both oiled and clean animals were collected during clean-up operations. A drift fence was constructed around the vernal pool to preemptively capture clean animals attempting to enter the contaminated zone. The Anuran species recovered were American toad (Anaxyrus americanus), green frog (Lithobates clamitans), and spring peeper (Pseudacris crucifer). Caudate species recovered were streamside salamander (Ambystoma barbouri), Jefferson salamander (Ambystoma jeffersonianum), Southern two-lined salamander (Eurycea cirrigera), and Southern red-backed salamander (Plethodon serratus). The Ambystoma sp. were in the midst of their annual run to the vernal pool to breed and were the most frequently encountered amphibian species (78%). Tri-State adapted their standard operating procedures to suit the demands of the unique caseload.
All animals were examined upon intake. Photo documentation and skin swabs were collected in accordance with Tri-State’s standard procedures. Oiled amphibians were rinsed with water upon recovery and then periodically until being washed in a dilute concentration (2%) of Dawn® dish soap. The animals were housed individually on moistened unbleached paper towels. Terrarium moss and additional moist paper towels were provided for burrowing opportunities.
A release plan was developed in consultation with herpetologists and local experts. Experts believed that Ambystomatids released onsite would inevitably return to the vernal pool during their breeding season. Due to this seasonal breeding behavior, wildlife trustees elected to hold the Ambystomatids in captivity until the oil cleanup in the environment reached an acceptable phase. Trustees decided against relocating the animals to a new habitat. Other species were relocated to nearby water sources after rehabilitation, as they were unlikely to return to the contaminated zone.
Tri-State cared for forty-one amphibians representing seven species between 21 March and 2 April. Upon demobilization, Tri-State transferred twenty-three Ambystomatids to an AZA accredited facility equipped to provide long-term housing until they could be safely returned to the nature preserve. Fully recovered salamanders were released at the nature preserve in late May 2014.
Some of the salamanders collected presented with traumatic injuries upon intake examination. Two streamside salamanders had injuries consistent with crushing. Six streamside salamanders and one Jefferson salamander exhibited burns of varying severity as a result of thermal remediation conducted on contaminated leaf litter along the stream and vernal pool. Tri-State followed basic wound management protocols on the affected salamanders and consulted with spill managers and wildlife trustees to minimize the impacts of thermal remediation on amphibians. Five of the burned salamanders died or were euthanized as a result of their injuries. Two streamside salamanders with moderate burns survived with minimal scarring.
This unique wildlife response was a learning experience for all involved. It is uncommon for wildlife responders to be mobilized for oil spills that do not impact conspicuous, large-bodied species such as birds and mammals. This was Tri-State’s first response with a primarily amphibian caseload and it provided many opportunities to develop and test treatment protocols. It was also an opportunity to collaborate with local herpetologists on a wildlife plan that included preemptive capture and long-term housing. The burned salamanders were an unfortunate reminder that remedial actions following a spill may carry their own risks for wildlife. Amphibians and reptiles may be particularly vulnerable to remediation techniques that are generally not a concern with birds and mammals. Wildlife responders should consult with local experts to advise spill managers of ways to mitigate remedial effects on all wildlife, not just the birds and mammals.
Conclusion Oil’s lethal and sub lethal effects on amphibians are still relatively unknown. While oil mortality events may be less threatening to amphibian populations than habitat loss and emerging diseases, it is pertinent that oiled wildlife response organizations familiarize themselves with amphibian recovery strategies. Threatened and endemic species could be highly vulnerable to an oil mortality event. Responders should consider amphibians when providing recommendations and developing response plans for spill managers and trustees. Amphibians may never receive the same attention as birds, mammals, and large reptiles, but as an icon of the modern biodiversity dilemma, they are worthy of protection and rehabilitative efforts during oil spills.
Literature Cited McCallum, M.L. (2007). Amphibian decline or extinction? Current declines dwarf background extinction rate. Journal of Herpetology, 41(3), 483-491.
Mendelson, J.R., Lips, K.R., Gagliardo, R.W., Rabb, G.B., Collins, J.P., et al. (2006). Confronting amphibian declines and extinctions. Science, 313:48.
Hoffman, D.J., Rattner, B.A., Burton, A., Caines, J. (2003). Handbook of Ecotoxicology (2nd ed.). Boca Raton, FL: Lewis Publishers.
Sparling, D.W., Linder, G., Bishop, C.A., Krest, S., (2010). Ecotoxicology of Amphibians and Reptiles (2nd ed.). CRC Press.
Stuart, S.N., Chanson, J.S., Cox, N.A., Young, B.E., Rodrigues, A.S.L., et al. (2004). Status and trends of amphibian declines and extinctions worldwide. Science 306:1783-1786.
Stuart, S.N., Hoffmann, M., Chanson, J.S., Cox, N.A., Berridge, R.J., Ramani, P., and Young, B.E. (eds.) (2008). Threatened Amphibians of the World. Arlington, VA: Conservation International.