The COVID-19 pandemic has impacted lives everywhere, including my own. It has been almost a year since I left the office and began working remotely. This change has left me grappling with feelings of isolation that I have never felt before. However, isolation is a phenomenon that impacts species beyond humans. I have come to empathise with one that is native to my hometown in Whatcom County, Washington—the Oregon spotted frog (Rana pretiosa). Their decline has been exacerbated by population isolation, which occurs when small populations of a species can no longer reach each other.
The Oregon spotted frog and I
The Oregon spotted frog is my neighbour on the Pacific Northwest coast of the United States of America. They are typically found at lower elevations in still water ponds connected by streams or ditches. Named after the black spots found across their back, Oregon spotted frogs can be green, tan, or red, and they have bright yellow or gold eyes. These frogs were once found in wetlands from southwestern British Columbia to northern California. But they now occupy only 10–30 percent of that territory, concentrated in limited areas of western Washington, southwestern British Columbia, and Oregon. Before the pandemic, I regularly travelled a similar distance, visiting family and friends in British Columbia and Northern California. I now only travel within my small city. This restriction in range makes me claustrophobic at times. However, for the Oregon spotted frog, this habitat limitation has led to them being listed as ‘threatened’ in the U.S. Endangered Species Act and as ‘endangered’ in Canada. There are multiple factors influencing the decline of the species. However, the loss and alteration of their wetland habitat is listed as one of the main causes.
Isolation and its consequences
Oregon spotted frogs rarely stray from wetlands. They utilise shallow ponds in the spring during their breeding season, while deeper waters suit their active lifestyle in the summer. In the winter, they seek natural springs, beaver features (areas with water overflowing stream banks or pools created by a dam), and other wetlands with emergent vegetation. Feeding, basking, mating, and movement between seasonal habitats all occur in the water. However, connected landscapes with habitat requirements for all seasons have become increasingly rare. This restriction of movement now feels similar to how almost all my activities are limited to my apartment. Yet, my experience differs from that of the Oregon spotted frog in that I have the option of leaving.
This isolation due to lack of aquatic habitat connectivity occurs at both the population level as well as between seasonal habitats. Population isolation occurs as groups of Oregon spotted frogs that used to congregate during breeding can no longer reach each other. While I currently feel isolated from my family and friends, these frogs have been dealing with isolation from their extended family and friends for generations. This has led to sub-divided genetic groups with low genetic diversity, or genetic variation, due to inbreeding. Maintaining and improving connectivity between seasonal habitats is important for the survival of individual frogs, while reducing population isolation improves the chances of survival of the species overall.
Aquatic habitat connectivity can be disrupted in several ways, with human structures and processes playing a major role. Similar to how I’m restricted by the physical constraints of signs, tape, plastic shields, walls, and other barriers to enforce social isolation; impervious surfaces, such as roads, can create physical barriers between populations of Oregon spotted frogs. Further, unsuitable habitats can also act as a barrier to connectivity if water quality, hydrology, and plant species composition impede movement between habitat patches.
Since receiving my first dose of the COVID-19 vaccination, I’m able to foresee an end to my isolation. While vaccine creation and dissemination brings hope for the end of the worst impacts of the virus, the future of Oregon spotted frog habitat improvement is grim. They have evolved to rely on aquatic habitat for much of their life history. Factors such as precipitation and temperature can have an enormous impact on the connectivity between populations. If the streams and ditches they use to move are dry or too warm, they become further isolated. Climate change projections for the Pacific Northwest also indicate that there will likely be a reduction in the overall water availability, which would create a reduction of water connectivity for the Oregon spotted frog. This in turn leads to further isolation. However, the good news is that we can work towards conservation solutions, similar to how we have worked towards mitigating the effects of the COVID-19 pandemic.
Conservation solutions for the Oregon spotted frog are complex and require a multi-pronged approach, similar to the COVID-19 pandemic. We are utilising social distancing measures, vaccine development and deployment, and protective equipment to bring an end to the pandemic. Conservation solutions for the frog depend on decreasing their isolation through maintaining habitat connectivity, expanding and maintaining Oregon spotted frog habitat, and the founding of additional populations.
Captive breeding and head-starting
Some work is already ongoing to potentially reintroduce Oregon spotted frogs into areas that were likely part of their former range. Similarly, captive breeding, reintroduction, and head-starting programmes are underway in Canada and the United States. In head-starting programmes, young individuals are removed from wild populations and raised in captivity during vulnerable life stages, before being reintroduced into the population. This is comparable to how more vulnerable human populations, such as the elderly or those with autoimmune disorders, had special grocery store hours and other measures to protect them until the vaccine became available.
Captive breeding with reintroduction and head-starting programmes help conserve Oregon spotted frogs by introducing more genetic diversity into isolated populations. However, there are a few challenges. Some studies have shown that wild populations can be harmed by captive-reared reintroductions. This is because those animals do not survive as well, despite increasing genetic diversity. It also takes many captive frogs to have sufficient genetic diversity. This problem is currently being improved by a new method that involves freezing sperm from different individuals, minimizing the number of males needed to be kept in captivity. However, like social distancing measures, captive breeding and head-starting are only temporary measures. Predictive modeling suggests that these measures can likely reduce short-term extinction, but they will not save the species in the long term. It is common in reintroduction programmes for the original threats that cause a species’ decline to continue to impact the introduced animals and the population as a whole. Thus, it is imperative to also address the issue of habitat loss and alteration.
Habitat loss is considered the leading cause of decline of the Oregon spotted frog. Reversing the loss of habitat is important for improving genetic diversity in the frog populations. As with COVID-19, where achieving a high proportion of vaccinated individuals is the only way to end the pandemic; improving, maintaining, and creating suitable Oregon spotted frog habitat is essential to ensuring their long-term persistence.
Of special concern is the loss and alteration of shallow breeding wetlands. This, in part, is caused by invasive reed canary grass (Phalaris arundinacea). Controlling invasive aquatic plants is difficult because herbicides can cause damage to amphibians and many mechanical or manipulative approaches have limited effectiveness. Fortunately, recent work has shown that some herbicides can be used without harm to the Oregon spotted frog to control the reed canary grass. These herbicides are now being applied, but eradication takes several applications over a few years.
Cattle grazing was also shown to successfully reduce reed canary grass in these habitats in 2003. However, livestock cannot remove the plant permanently, and can also lead to adverse impacts by contributing to water quality issues. To be used effectively, it should be limited to open thick stands of reed canary grass. Studies are being conducted to understand the full impact of grazing on Oregon spotted frogs. Similarly, mowing reed canary grass is a short-term solution because it will not remove the grass permanently. These solutions are reminiscent of utilizing protective equipment, such as masks, against COVID-19. They are not completely effective. However, if implemented repeatedly and universally, protective equipment can help minimise the spread. In the case of the cattle grazing and mowing, it can help to rebuild populations until more permanent solutions are found.
Apart from invasive plant management, other habitat improvements can also be made. We have all sought ways to improve our lives at homes, in order to deal with overwhelming feelings of social isolation. I have personally bought new books and other sources of entertainment. I have also created an office for myself at home.
Introducing and protecting beavers (Castor canadensis) is one way to improve Oregon spotted frog habitat. Beavers help create suitable habitats and increase habitat connectivity. Improving water connectivity between habitats is just as essential. Even man-made ditches can help the frogs travel farther to overwintering habitats. Additionally, improvement or maintenance of water quality, hydrology, and vegetation are also important for creating suitable habitat and ensuring habitat connectivity. Habitat improvements must focus on the physical, spatial, and environmental requirements of the Oregon spotted frog to be effective.
Population isolation—due to lack of habitat and water connectivity—is leading to the decline of the Oregon spotted frog, and we are largely to blame. Some of the last remaining suitable frog habitat is in my hometown. Until recently, I wasn’t aware of their existence. If it were not for my own isolation during the COVID-19 lockdown, I would not have empathised as deeply with their plight. For the effective conservation of the Oregon spotted frog, habitat concerns should be addressed, populations should be augmented, and populations need to continue to be monitored. This requires both community and global involvement. Much of the Oregon spotted frog habitat in Whatcom County is on private land. Local residents, like myself, can help by spreading awareness of the frog’s struggles and the different methods that can be deployed to increase habitat and water connectivity. Awareness can then lead to further community action, such as improving water quality in local waterways and advocating for beaver protection.
Duarte, A., J. T. Peterson, C. A. Pearl, J. C. Rowe, B. McCreary, S. K. Galvan, and M. J. Adams. 2020. Estimation of metademographic rates and landscape connectivity for a conservation-reliant anuran. Landscape Ecology 35(6): 1459–1479.
Funk, W. C., C. A. Pearl, H. M. Draheim, M. J. Adams, T. D. Mullins, and S. M. Haig. 2008. Range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and Rana pretiosa) in northwestern North America. Molecular Phylogenetics and Evolution 49(1): 198–210.
Robertson, J. M., M. A. Murphy, C. A. Pearl, M. J. Adams, M. I. PáezVacas, S. M. Haig, D. S. Pilliod, et al. 2018. Regional variation in drivers of connectivity for two frog species (Rana pretiosa and R. luteiventris) from the U.S. Pacific Northwest. Molecular Ecology 27(16): 3242–3256.
Map created by Technology for Wildlife. Colour: Karunya Baskar